ENGINEERING RESEARCH INSTIT TJIE T UNIVERSITY OF MICHIGAN ANN ARBOR PROMOTION OF SOME CHEMICAL REACTIONS WITH GAMMA RADIATION Reported by: JOHN G. LEWIS Supervisor: J. J. MARTIN Project M943-4 U. S. ATOMIC ENERGY COMMISSION CONTRACT NO. AT (11=1)-162 January, 1954

PREFACE The author wishes to acknowledge the assistance, direction, and support of all who have made this report possible: Dr. L. C. Anderson Mr. R. L. Kinney Mr. F. Bashore Dr. J. J. Martin Dr. L. E. Brownell Mr. R. D. Pierce Mr. F. H. Chadsey Mr. E. M. Rosen Dr. H. J. Gomberg Mr. S. A, Stolton Mr. J. R. Hallman Dr. L. Thomassen Mr. D. E. Harmer Mr. L. E. Wagner Dr. L. M. Hobbs ii

TABLE OF CONTENTS Page PREFACE ii LIST OF TABLES v LIST OF.FIGURES vi ABSTRACT ix INTRODUCTION 1 APPARATUS 3 General Description 3.Design and Construction of a Pressure Reactor 3 Hydrostatic Test of the Reactor 8 Operation of the Reactor 9 ANALYSIS OF DOSE RATES NEAR HOLLOW CYLINDRICAL SOURCES OF GAMMA RADIATION 28 Experimental Procedure 29 Calculation Procedure 32 DOSE RATES WITHIN A CYLINDRICAL PRESSURE REACTOR 6o PRELIMINARY INVESTIGATIONS 72 Synthesis of Ammonia 72 Beta Radiation from Palladium-109 74 Partial Polymerization of Natural Oils 76 Polymerization of Acetylene 78 Chlorination of Kerosene and Benzene 79 Oxidation of Sulphur Dioxide. 81 Reaction of Carbon Dioxide with Hydrogen 84 Polymerization of Isobutylene 85 Polymerization of Propylene 85 Polymerization of Ethylene 85 DISCUSSION OF PRELIMINARY INVESTIGATION 86 POLYMERIZATION OF ETHYLENE 90 Prior Work 90 Polymeritation of Ethylene by Means of Gamma Radiation 91 DISCUSSION OF POLYMERIZATION OF ETHYLENE 97 EVALUATION OF POLYETHYLENE PRODUCT 99 iii

Page SUGGESTIONS FOR U~jIURE WORK IN I9E PROMOTION OF CHEMICAL REACTIONS BY GAMMA IRRADIATION 121 Polymerization of Ethylene 121 Other Reactions 122 CONCLUSIONS 123 APPENDIX 125 Design Data for Bomb 125 Assembly Instructions for Bomb 125 Operating Instructions for Bomb 126 Definition of Radiation Yield 126 BIBLIOGRAPHY 129

LIST OF TABLES Table No. Page I Irradiation of Ferrous Sulfate Solutions in Cobalt-60 Source - Dosimetry by Method of Weiss 31 II Dose Rates on Axis of 10-KC Source 36 III Dose Rates on Mid-Plane of 10-KC Source 37 IV Estimates of Activites from Measurements of Dose Rates 38 V Dose Rates on Axis of 1-KC Source 40 VI Irradiation of Mixture of Nitrogen and Hydrogen with Palladium-10O9 Beta Rays 73 VII Results of Irradiation of Natural Oils with Palladium109 Beta Rays 75 VIII Changes in Viscosity of Soya Oil after Irradiation and Subsequent Heating 77 TX Irradiation of Mixtures of Kerosene and Chlorine in 1-KC Cobalt-60 Gamma Source 80 X Irradiation of Mixtures of Benzene and Chlorine in 1-KC Cobalt-60 Gamma Source 82 XI Irradiation of Mixtures of Sulfur Dioxide and Oxygen in 1-KC Cobalt-60 Gamma Source 83 XII Irradiation of Propylene 83 XIII Irradiation of Ethylene 92 XIV Analyses of Ethylene from Storage Cylinders and from Reactor 95 XV Properties of Polyethylene Produced 103

LIST OF FI GURES Figure Page 1 Working Drawing for the Construction of the Reactor 11 2 Pressure Reactor and Auxiliary Fittings 12 3 Pressure Reactor Disassembled 13 4 Electrical Connections of Pressure Reactor 14 5 MDrawing of Plug Gauge 15 6 Pressure Reactor with 150 psi Rupture Disc 16 7 Plug Gauge and Body of Reactor 16 8 Adapter Fitting: Cone Joint to Iron Pipe Thread 17 9 Adapter Fitting: Cone Joint to Iron Pipe Thread 18 10 Pressure Reactor: X-rays of First Welds Showing Locations at Head 19 11 Pressure Reactor: X-rays of First Welds Showing Locations at Bod~y 20 12 Pressure Reactor: X-rays of Second Welds Showing Locations 21 13 X-ray B2: Weld in Upper Body - First Attempt 22 14 X-ray of Weld in Upper Body - Second Attempt 22 15 X-ray C3: Weld at Head - First Attempt 23 16 X-ray of Weld at Head - Second Attempt 23 17 Pressure Reactor: Drawing of Rack 24 18 Pressure Reactor: Drawing of Sling 25 19 Extension Legs for Rack 26 20 Pressure Reactor Behind Lucite Shield for Palladium109 Experiments 27 21 Insertion of Pressure Reactor into l-Kilocurie Gamma Source 43 vi

LIST OF FIGURES (Oont) Figure Page 22 Pressure Reactor in l-Kilocurie Gamnra Source 43 23 Rack and Sling for Pressure Reactor 44 24 Pressure Reactor: Tubing Assembly and Gas Cylinder 44 25 Pressure Reactor in l0-Kilocurie Gamma Source Room 45 26 Sectional View of Cobalt-60 Vault 46 27 1-Kilocurie Cobalt-60 Source with Shielding 47 28 10-Kilocurie Source: Elevator and Well 48 29 10-Kilocurie Source: Rack for Rods 49 30 Cobalt Rod for 10-Kilocurie Source 50 31 Source with Negligible Wall Thickness 51 32 Source with Finite Wall Thickness 52 33 Dose Rate Equations for Source with Finite Wall Thickness 53 34 Dose Rate on Mid-Plane of 10-Kilocurie Source 5,4 35 Dose Rate on Axis of 10-Kilocurie Source 55 36 Dose Rate on Axis of 1-Kilocurie Source 5 37 Location of Dosimetry Samples for Run 132307 with 10-Kilocurie Source 57 38.Location of Dosimetry Samples for Run 152308 with 10-Kilocurie Source 58 39 Dose Rates Parallel to Mid-Planey Interpolated from Measurements with 10-Kilocurie Source 59 40 Dose Rates Parallel to Axis, Interpolated from Measurements with 10-Kilocurie Source 65 41 Is odose Surfaces Interpolated from Measurements with l0-Kilocurie Source 66 42 Calculated Dose Rates Parallel to Mid.Plane with 1-Kilocurie Source 67 43 Calculated Dose Rates Parallel to Axis with 1-Kilocurie Source '68 vii

LIST OF FIGURES (Oont) Figure Page 44 Calculated Isodose Surfaces with 1-Kilocurie Source 69 45 Diagram for Attenuation by Distance and Absorption 70 46 Diagram for Dose Rate Inside Pressure Vessel 71 47 Location of Pressure Reactor for Dose Rate Studies with 10-Kilocurie Source 87 48 Dose Rates Inside Pressure Reactor with 1-Kilocurie Source 88 49 Dose Rates Inside Pressure Reactor with 10-Kilocurie Source 89 50 Average Dose Rate Inside Pressure Reactor as Function of Time with 1-Kilocurie Source 106 51 Average Dose Rates Inside Pressure Reactor as Function of Time with 10-Kilocurie Source 107 52 Apparatus for Drying of Natural Oils by Palladiumn-109 Beta Rays 108 53 Flow Sheet for the Additive Chlorination of Benzene 109 54 Melting-Point Bar 110 55 Influence of Oxygen on Polymerizati,6n of Ethylene 111 56 Yield as Function of Order of Run in Polymerization of Ethylene 112 57 Rate as Function of Order of Run in Polymerization of Ethylene 113 58 Radiation Yield as Function of Dose of Radiation in Polymerization of Ethylene 114 59 Solution Viscosity Determinations on Polyethylene 115 60 Molecular Weight as Function of Radiation Yield of Polyethylene 116 61 Molecular Weight and Crystallinity as Functions of Radiation Dose for Polyethylene 117 62 Stress-Strain Plots for Test Specimens of Polyethylene 118 63 Crystallinity and Tensile Strength as Functions of Radiation Yield for Polyethylene 119 64 Melting Points as Functions of Radiation Yield of Polyethylene 120 viii

ABSTRACT The purpose of the program of investigation described below was to study some radiation-promoted chemical reactions of potential industrial importance. In gaseous systems the high densities which result from the application of high pressures increase the absorption of gamma radiation. Therefore pressure was thought to increase any chemical effects caused by radiation. Since many systems of interest are gaseous, it was decided to construct a pressure reactor to study such systems in the presence of radiation. A description is given of the design, construction, and successful operation of this pressure reactor used in proximity to the sources of radiation. An analysis is presented of the dose rates caused by the sources of gamma radiation, both in air and within the reaction vessel. The resulting measure of the intensity of irradiation made possible the relating of irradiations and the chemical effects observed. Preliminary investigations were made of the influence of gamma radiation on the following reactions: synthesis of ammonia; oxidation of drying oils and of sulfur dioxide; chlorination of kerosene and of benzene; the reaction of carbon dioxide and hydrogen; and the polymerization of soya oil, acetylene, isobutylene, propylene, and ethylene. The polymerization of ethylene to a white, solid polyethylene is described in detail. Also reported is the influence of radiation yield and of some trace impurities on molecular weight, crystallinity, tensile strength, and melting point of the solid polymers of ethylene. ix

INTRODUCTION The production of fission products as an unavoidable feature of the operation of nuclear reactors has necessitated the development of extensive storage programs for the isolation of these highly radioactive materials. It has appeared to be advisable to develop some potential applications of fission products, both in order to use the energy emitted by these materials and in order to provide an alternative to the expensive dead-storage facilities which must otherwise be provided (see Gibson25). The fission products are chemical elements resulting from the splitting or fissioning of uranium-235 as a consequence of nuclear reaction. The most abundant fission products are those resulting from the approximate halving of the uranium-235. Most of the fission products emit gamma or beta radiation. If attention is restricted to fission products occurring in yields of more than 0.5%, of half-lives longer than 40 days, and of energy levels of more than 0.1 million electron-volts, then the energy of the emissions does not exceed about 1.5 million electron-volts for either beta or gamma radiation (see Hayner28). The beta radiation would be absorbld by the walls of most containers. Consequently the gamma radiation would be the only form of radiation usable in an installation in which the fission products are not in direct contact with the materials to be irradiated. One possible useful function of gamma radiation is in the promotion or catalysis of chemical reactions. It seems logical to expect gamma radiation to promote chemical reactions. Gamma radiation, in common with alpha and beta radiation and x-rays, causes ionization to occur in matter in its path. Such kinds of radiation are consequently known collectively as

ionizing radiation. If ions are produced in a mixture of materials which could react chemically, then a reaction might be expected to occur in order to satisfy the electrical forces thus set up. A program of investigation was undertaken with the objective of finding some chemical reactions so promoted by gamma radiation that they would provide industrial applications for the waste fission products. Since it was desired to simplify the techniques of preliminary investigations and the interpretations of the results, fission products were not used as sources of gamma radiation for the work described below. One reason for not using fission products in preliminary studies is that the handling of these materials appears to be troublesome. In addition, the separation of the fission products into individual isotopes of well defined radiation spectra appears to be a formidable problem. In any event, fission products are not yet available in packaged form for use in the laboratory. In order to minimize difficulties of the kind just mentioned, cobalt-60 was used as the source of gamma radiation. Cobalt may be fabricated into convenient form for handling before being made radioactive by irradiation in a nuclear reactor. Moreover, the chief components of the spectrum of cobalt-60 are two gamma rays, of 1.17 and 1.31 million electron-volts. Consequently, by the use of cobalt-60, problems of handling the source of radiation are minimized, and a radiation of nearly uniform energy is obtained. Experimental data can then be correlated more surely with the effects of radiation. In the following work there is presented first a brief description of some exploratory work done in an effort to discover some reactions of potential industrial usefulness which would be accelerated significantly by gamma radiation. There are then presented the results of the principal program of research followed, the polymerization of ethylene by means of gamma radiation.

APPARATUS General Description In the section on Preliminary Investigations references are made to the various pieces of apparatus used in those investigations. Most of the equipment was of standard design and presented no unusual features. However, for the conduct of the experiments under pressure, it was necessary to design and build a vessel which would permit the use of elevated pressures and temperatures for the reacting system while in close proximity to a source of gamma radiation. The description of apparatus will be limited chiefly to an explanation of the design of this pressure equipment. Design and Construction of a Pressure Reactor Design Conditions. A special reactor was designed and constructed for the purpose of holding chemical systems simultaneously under pressure and in the presence of gamma radiation. Design conditions chosen were 2000 psi at 650~F. Details are shown in Fig. 1. The rate of absorption of gamma radiation of a given intensity may be considered proportional to the density of the gases within the vessel, and the density may be considered approximately proportional to the pressure. Therefore it is evident that pressures of 2000 psi will permit absorption in a perfect gas at about 130 times the rate at 1 atmosphere, neglecting absorption of radiation by the walls of the container. The use of a maximum pressure of 2000 psi permitted the use of gas cylinder pressure and minimized the need for a compressor, It was decided that the use of pressure in proximity to the source of radiation need cause no unusual concern. It was not clear just how to define a maximum permissible temperature of operation, however. One

criterion was that sufficient clearance be allowed between the bomb and the source in order that thermal expansion would not cause the bomb to stick inside the source. The other criterion was that the temperature should not be so high that the aluminum jacketing around the cobalt would be weakened or that the air between the cobalt and the aluminum would reach a pressure high enough to cause a break in the aluminum jacket. A tentative upper limit in temperature of 5750F was set for the jacket surrounding the source. It was necessary for the reactor to be inserted into an access hole 1-1/2 inches in diameter in a shielding block of lead (see Figs. 26 and 27) in order for the vessel to be exposed to the gamma radiation. The thickness of the walls of the vessel was kept to a minimum in order to make a maximum amount of working space available within the bomb and also to allow a maximum amount of gamma radiation to pass through to the contents. For the use of the pressure vessel in the l-kilocurie source, which has no auxiliary shielding, the effect of the pressure vessel on personnel shielding requirements had to be investigated. Measurements of dose rate surrounding the source indicated that no perceptible horizontal scatter was caused by a model of the bomb. Measurements made after the subsequent completion of the bomb showed the same result. Materials of Construction. AISI 304 stainless steel was chosen as the material of construction for the body, head, and flanges of the bomb. This material would resist corrosion by many chemicals and would permit higher stresses and therefore thinner walls in the body than would carbon steel. An 18-8 austenitic steel was also desired so that chilling in dry ice would be permissible without going below the transition temperature of the steel. The bolt studs and nuts for assembling the bomb are shown in Fig. 3. The bolt studs are of ASTM A-193. The nuts were cut from AISI 304

plate, with the transverse plane of each nut parallel to the flat direction of the plate. The plates were faced down sufficiently to remove all surface blemishes. The flanges for the bomb were cut according to the same specifications as the nuts. Usually the reactant materials were charged to the bomb and the product materials were removed from the bomb through the tubing assembly shown in Fig. 3. AISI 304 seamless steel tubing was used. Ermeto fittings, manufactured by the Weatherhead Corporation, were used for all connections except to the bomb and to the gauge. It was desired to avoid pipe threads at these latter two points, and consequently Fixed Nitrogen Research23 metal-to metal joints were employed. In Fig. 8 are shown the details of a special fitting employed to connect a pressure gauge having an iron-pipesize thread to a cone joint fitting. The pressure gauge fitting was machined out to provide a cone seat to match the standard cone on the end of the tubing. This kind of joint was used to provide a better seal than was thought to be possible by the use of tapered pipe threads. The assembly of tubing and fittings was originally constructed using aluminum tubing except for the cone joints. The aluminum was found to be too easily bent, and was replaced with the stainless-steel tubing. The bends shown were made cold. Design of Component Parts. Seamless tubing was selected for the body, and it was decided to weld the bottom-end-closure to the body. 'is procedure was adopted in order to avoid machining a long thin-walled vessel from solid stock. A section with screw threads was to be machined from solid stock and welded to the top of the seamless tubing for the body section. The body flange was to be secured by screw threads in order to avoid welding the flange section to the much thinner body section.

A tongue-and-groove joint was used between the body and the head. The tongue was machined on the body, the walls of which were too thin to receive the groove. The design of the head presented special -problems, since the flanges were to fit within the existing opening in the vault. This opening was only 4-1/2 inches in diameter. Therefore the bolt circle was made as small as possible, both in order to fit within the vault and to prevent undue stress and deflection of the flanges. The flanges were particularly subject to deflection, having been made thin in order to keep the joint between body and head as far within the access hole as possible 'and thereby to reduce scatter of the primary beam of radiation into a horizontal plane. Although the bolt circle had to be as small as possible because of radiation shielding requirements, the head of the bomb had to accommodate numerous connections, namely, two electrical power leads, four thermocouple leads, an entrance line, an exit line, a pressure gauge, and a rupture disc. There was barely room to accommodate two 1/4-inch holes inside the gasket circle of the head. Space for all these required connections was obtained by using a piece of round bar for the head and running the electrical leads in through the exit opening and the thermocouple leads in through the entrance opening. These electrical fittings were sealed by means of Fixed Nitrogen Research23 cone joint fittings using "Teflon" cones in holes drfilled into the side of the head and intercepting the respective process holes, wrhicrh were drilled longitudinally through the head.. The pressure gauge and. r upture disc were placed on the external tubing lines, A single-jacketed copper-clad asbestos gasket of standard size was selected for use in the head-to-body joint. These gaskets are manufactured by Goetze Gasket Division of the Johns-Manville Corporation.

Welding and Inspection of Welds. The three welded joints were welded initially using AISI 309 rod of 1/8-inch diameter at 80 amperes. The surface finish of these welds was exceptionally smooth. Some positiveprint x-ray photographs of these welds appear in Figs..13 and 15. All three joints were rejected because of regions of low density such as those shown. The joints were all cut open. Each joint contained a black material reseribling slag in the regions shown by the photographs to be of low density. The joints were refaced and rewelded, using AISI 347 rod of 1/8-inch diameter at 110 amperes. Some undercutting resulted, and the exteriors of the welds appeared somewhat rough. Some positive-print x-rays of the second welds appear in Figs. 14 and.16. These welds were all accepted. Some light spots appear in the head-to-flange weld, but these could be accounted for almost entirely by the surface roughness due to undercutting. Installation of Electrical Circuits. In Fig. 4. appears a supplementary section through the head of the bomb, showing the method of assembling the electrical connections. The installation of the power leads was accomplished by first threading a bare copper wire into the top hole and out of the bottom of the vertical hole. The wire was pulled tight to give a nearly square corner at the turn in order to assist in keeping the wire centered in the hole. The two-hole ceramic spaghetti insulation was inserted over the wire in the space between the horizontal outlets. Then a bare wire was inserted in the same manner through the lower horizontal hole. The lower ceramic spaghetti insulation was added; then the one-hole ceramic spaghetti was inserted into the horizontal holes. The circuits were checked for continuity and grounds, and then the pressure seals were assembled. The installation of the thermocouple leads was accomplished in a similar manner. These leads were more easily threaded through the holes than were the copper wires and also carried their own insulation. The

insulation of the thermocouple leads consisted of a silicone varnish applied directly to each lead and a braided glass fabric which covered both leads. This type of thermocouple lead was a Leeds and Northrup product. It was discovered that if the glass braid was removed from the assembly for several inches and the two wires threaded together, through the 0.040-inch hole in the "Teflon" cone, a seal could be made which would retain 2000 psig. This result was unexpected, since it was thought originally that a separate sealing cone would be required for each wire, and that the wire would have to be scraped to bare metal. After the "Teflon" cones had once been seated by the retaining nut, they were difficult to extract from their seats. It was found that if the wires were pulled out, wood screws could be driven into the wire hole, and the plug extracted by pulling on the screw. The hole would be much enlarged, but re-application of pressure by the retaining nut would re-form the "Teflon" about a wire and permit a usable seal. Often, however, the cone would be ruined in extracting it in this manner. The thermocouples used were formed by welding matched chromel P-alumel wires in an oxygen-gas flame. Brazing flux was applied molten before the twisted couples were heated. Hydrostatic Test of the Reactor After the reactor was completed and before it was placed in regular service, it was given a hydrostatic test at 2800 psig. The electrical outlets were plugged with short stubs of wire during the hydrostatic tests. The test pressure was maintained for about one hour, All joints were then hammered with a soft-faced hammer while a pressure of 2000 psig was maintained.

After the initial welding was completed a hydrostatic test conducted as described above revealed the presence of a pin-hole leak at the location shown in the x-ray of Figs. 12 and: 13 After the second welding was completed, a hydrostatic test was conducted as indicated above. No diminution of pressure and no visible leaks occurred. An x-ray of the location after rewelding was completed appears in Fig. 14. Operation of the Reactor The flanges of the reactor were tightened to the same clearance all around, with a tolerance of + 0,001 inch measured directly opposite the bolt studs. A clearance of 0.120 inch to 0.150 inch was found to be satisfactory. The nuts were tightened to about 250 inch-pounds of torque. Some difficulty was experienced in inserting the body of the bomb into the vault. An external diameter of 1.480 inches was specified for the bomb, and this should have been sufficiently small to clear the inside of the vault opening which was supposed to be 1-1/2 inches in diameter (see Figs. 26 and 27), The bomb would enter the hole freely for about 10 inches and then stop. In order to investigate this situation a special gauge was fabricated (see Figs. 5 and 7). The gauge was a piece of 1-1/2 -inch-outside-diameter cold-rolled steel bar with a handle permitting remote manipulation over the open source. The bar was originally 1.499 to 1.500 inches O.D. This diameter permitted the bar to be inserted 12-1/4 inches, The bar was turned to 1.490 inches and could then be inserted 14-1/4 inches, The diameter was reduced by 0.010-inch increments to 1.470 inches, at which dimension it would go in 22-1/4 inches. Then it was finally turned to 1.465 inches, which dimension permitted the gauge to go in the full

10 24-1/8 inches with a minimum clearance of 0.005 inch on the diameter. The body of the bomb was then turned to 1.465 inches O.D., and fitted into the vault satisfactorily. A steel rack was designed and built for the purpose of positioning the stainless-steel reactor approximately symmetrically with respect to the 10-kilocurie source (see Figs. 17 and 23 for details). Extension legs (Fig. 19) permit use of the rack to hold the reactor on the axis of the source. The steel rack was designed to accommodate the sling (Figs. 18 and 23) previously constructed for the purpose of supporting the reactor with its attached tubing in the 1-kilocurie source.

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-ERAMIC INSULATORS TEFLON CONES 10*04 DRILL CERAMIC INSULATORS FITTINGS 2-18 B.W.G BARE COPPER WIRES INSTALLATION AT POWER LEADS l i I~ ltNO. 28 B.W.S. CHROMEL ALUMEL DUPLEX TO CONDUCTOR LEEDS AND NORTHRUP GLASS BRAID OVER SILICONE VARNISH INSULATION OUTER GLASS BRAID STRIPPED OFF WHERE LEADS GO THROUGH TEFLON" CONES AMINCO ELECTRICAL PRESSURE FITTINGS INSTALLATION AT THERMOCOUPLES Fig. 4. Electrical Connections of Pressure Reactor. 14

III 1 THREAD.O.D. 16 I1111 1ci~ 9-44 US -1,46 --- Fig. 5. Drawing of Plug Gauge.

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C, I I 1t ISO KVP, SMA., IOMIN., DUPONT 506 FILM Fig. 10. Pressure Reactor: X-rays of First Welds Showing Locations at Head. 19

FILM A I - BOTTOM WELD POSITION A,SPOT I 2- BOTTOM WELD POSITION A,SPOT 2 B I - TOP WELD POSITION B, SPOT I 2-TOP WELD POSITION B, SPOT 2 0~~~~~~~~~~~~~~ 21/ I " SPOT 2 900AROUND VESSEL FROM I, MARKED ON MASKING TAPE 150 KVP, 5MA., 4 MIN., DUPONT 506 FILM Fig. 11. Pressure Reactor: X-rays of First Welds Showing Locations at Body.

150 KVP, 5MA., DUPONT 506 FILM PIN -HOLE LEAK AT 2500 PSI. I-IJw PHOTO# I PHOTO 4# 2 C M (CUT CORNER) IF 7W 8-2 POSITION BOTH VIEWS ON SAME FILM-VIEW EXPOSURE O.K #`2 ON CUT CORNER FOR VIEW 2 FILMS OVEREXPOSED Fig. 12. Pressure Reactor: X-rays of Second Welds Showing Locations.

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SCALE I '-0 TWO 16 DRILL Is 16 I6 PLAN WELD ON BASE PLATES TICK ELEVATION Fig. 17. Pressure Reactor: Drawing of Rack. I I jE)~2

I X IX L SCALE: I"= I'-0" BOLTS WITH WING NUTS Ie-I SCALE- FULL SIZE I AR 12 X 4 X4 PL. \543 INCHES LONG"U" BOLT DRILL 4 HOLES IN FIEL SCALE 4" I'-O" _ _ _ _ _ _ _ _ _ _ _ _ 84 2 _ _ -II _ I I - 416 / X4X PL. 51B INCHES LONG "U"HESE LINESOL 2 DRILL TWO 3 HOLES I-2 5 SCALE 4" I'-0" low 6 - 4 T i I fs DRILL - 2 HOLES

5/16" DRILL -I HOLE I/ IX IX 1/8 ANGLE I T ~PLAN b I I,, 4 u NOTE: 4 REQUIRED ELEVATION Fig. 19. Extension Legs for Rack. 26

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ANALYSIS OF DOSE RATES NEAR HOLLOW CYLINDRICAL SOURCES OF GAMMA RADIATION It was proposed to examine some effects of gamma radiation on the rate of polymerization of ethylene. For this purpose it was necessary to adopt some criterion of the effect of gamma radiation on matter. In the following treatment the rate of ionization produced in air has been used as a measure of the effect of gamma radiation. The units used are the roentgen for air subjected to electromagnetic radiation and the roentgen equivalent physical (rep) for tissue subjected to electromagnetic or to charged-parti-. cle radiation. Siri49 has discussed these units.. The roentgen corresponds to the absorption of about 83 ergs per gram of air, while the rep corresponds to the absorption of 93 ergs per gram of water58, and is often used to report doses for other aggregations of matter as well. There is some evidence that the rate of reaction in a given chemical system subjected to ionizing radiation is proportional to the rate of ionization produced in that system. Lind36 used an equation developed by Mund44 to calculate the rate of ionization produced in a given chemical system subjected to alpha radiation. Lind found that in many systems the yield of a given reaction produced by alpha radiation alone was proportional to the ionization as calculated by Mund's equation. Lind developed the concept of the "ion yield", i.e., the ratio of molecules of product secured to ion pairs produced in the system, which he denoted as "M/N". He foundthat values of M/N were nearly constant for a given system and were nearly equal for many systems. Values of M/N appeared usually to range from 1 to 2, but there were a few cases in which the value was much in excess of *28

29 unity. Allenl pointed out that the observed M/N should be constant for most systems at small degrees of reaction, but should decrease to 0 at e qulibrium. The rate of ionization caused by the passage of gamma radiation through matter is a common measure of the intensity of this radiation. As seen above, the rate of ionization has been found by other workers to govern the rate of chemical reactions under some conditions. Consequently, we now wish to develop a means of predicting the rate of ionization caused by gamma rays as a function of the position of the receiving point and the geometrical configuration and composition of the source. Such a measure of the rate of ionization is known as the "dose rate" in the matter, caused by the radiation. Experimental Procedure Dose rates were measured chemically by Harmer9 by the method employing the oxidation of ferrous sulfate solutions. Dilute solutions of ferrous sulfate (5 x.10- M) in aerated 0.8 N sulfuric acid solution were exposed to gamma radiation for doses of between 5 and 20 ki.lorep. The ferric ion produced by the gamma radiation depends on the presence of a small amount of oxygen which is furnished by first passing air through the solution. For quantitative determinations of the ferric ion produced by irradiation, the spectrophotometric method described by J. Weiss of Brookhaven National Laboratory was employed58. This method makes use of a spectral absorption peak of ferric ion at about 304 millimicrons in the ultraviolet region. Optical densities of the irradiated solutions are measured at 305 millimicrons and compared with those of known ferric solutions made up by dilution of standardized ferric stock solution.

30 In converting the chemical yield to radiation dosage, a value of 15.4 micromoles per liter per kilorep was used. This value is based on the absorption of 93 ergs/gm of water for each equivalent roentgen of radiation. The solutions were irradiated in glass bottles about 3 cm in inside diameter and filled to a depth of about 4 cm. The:bottles of solution were placed inside and outside the 10 -kilocurie source, as shown in Figs. 37 and 38, and were placed inside the 1-kilocurie source, (See Table I and Fig. 26.) Proper exposure times were calculated to fall within the range of the method of ferric-ion determination. Measurement of dose rate in the 1-kilocurie source was carried out at times separated by an interval of 1 year, and values were found to be consistent after corrections for radioactive decay were applied. Measurements using a ceric sulfate system were also made and found to agree within experimental error with the ferrous sulfate results. Physical determinations of dose rate have also been carried out by Nehemias9 on both sources. Two instruments have been employed in these determinations: The first was a Victoreen roentgen ratemeter, which measures the current flow between electrodes in an ionization chamber placed in the radiation field. The second was a Victoreen r-meter, which measures the drop in potential of a charged condenser due to ionization current caused by the radiation. The ratemeter was calibrated against raditun standards by the manufacturer, while the r-meter was calibrated against a cobalt standard at the University of Michigan. Within 50 cm of the center of the lO0-kilocurie source the ratemeter readings were 15 to 20 percent lower than the ferrous sulfate determinations. The r-meter readings were 15 to 20 percent higher than the ferrous sulfate measurements in the lO-kilocurie source, and were 25 to

31 TABLE I' IRRADIATION OF FERROUS SULFATE SOLUTIONS IN COBALT-60 SOURCE - DOSIMETRY BY METHOD OF WEISS58 Data From 10-Kilocurie Source Unless Noted Page 132308 Page 132307 Date 16 March 1953 Date 13 March 1953 See Fig. 38 For Location of See Fig. 37 For Location of Samples Samples Sample Dose Rate Sample Dose Rate Number kilorep/hr Number kilorep/hr 1 280 1.144 2 250 2 194 3 242 3 249 4 244 4 261 5 292 5 266 6 342 6 28.1 7 38 7 243 8 102 8 234 9 80 9 248 10 8 10 274 11 57 11 168 12 60 12 86.13.115 14 52 15 24 16 13 17 22.18.17.19 74 20 42 21 4o4 22 2.6 23 2.0 1 kilocurie 55

32 30 percent higher in the 1-kilocurie source. The detailed significance of these differences is not clear. Calculation Procedure Since gamma radiation front a point source may be assumed to follow the usual inverse-square relation, it is possible to calculate the dose rate at any position in the neighborhood of a source of known shape and total activity by an integration technique similar to that employed in radiant heat transfer. If the configuration of the source is complicated, the re-i sulting integration may be difficult. A hollow cylinder of negligible wall thickness is a simple shape similar to that of the two cobalt-60 sources. The activity of the actual source may be assigned to such a cylinder. The dimensions of such a cylinder were taken to correspond as nearly as possible to those of the actual source, and the assigned curies were assumed to be distributed uniformly over the surface of the cylinder. Absorption and attendant effects were neglected. Then the contribution to the radi-.ation intensity at any given point due to an element of source area, dA, at a distance p away was given by Equation (1). See Fig. 31. dI o dA (1) p2 The total intensity at the given point was obtained by summing the contributions from all elemental areas as =L G=r ar d; dZ I = 2. rdd - -- (2) JI = 2J~ R2 + r2 - 2Rr cos 0 + (ZZ)2 (2) Z=0 Q=0 Integrating Equation (2) gives

33 I = 2%Tr [F(tan-l R+r,k) - F(tan-1 R+r,k)] R+r Z1-L Z1 for Z1 > L > O, R > 0, r >, (3) 0 < tanl' R+r tan 1 R+r <it Z1-L Z1 2 and I = 2cr f2K(k) - [F(tan'- R+r,k) + F(tan-l R+r,k)] R+r L-Z1 Z1 for L > Z1 > O, R > O, r > O R r, (4) 0 < tan'l R+r tan-l R+r < L-Z1 Z1 2 An alternative form may be obtained as shown by Equation (5). Dewes and Goodale19 have indicated the preliminary steps in this development. I 2r F(tan1 k)F(tan' k) F(tan-1 Z1-L,k)] R+r r-R jr-R for Z1 > O R > 0, r > O, R r, (5) - - < tan-l ' <, O < tan- Z_ < _ 2 Ir-RI 2 Ir-RI 2 A relation given by Hancock27 permits the transformation of Equations (3) and (4) into Equation (5), and vice versa. Equation (5) is considered more convenient in most computations, except for R=r, Z1>L, where Equation (3) may be used. The symbols used above are defined as follows: I = dose rate, equivalent roentgens per hour.

34 A - area of source. p = distance from elemental area dA to the point at which I is taken. total activity000 millicuries \ area of source, cm2 curie (equiv. roentgens at 1 cm K (hour) (millicurie point source)/ r - radius of source, and also constant radius vector of cylinder. R = radial distance of point at which I is taken from axis of source. 9 = central angle from R to r. Z - distance parallel to axis of source from base of source to element dA. Z1 = A coordinate of point at which I is taken. k =.2/R+r F(V,k) = elliptic integral of first kind of modulus k and amplitude 0. K(k) = complete elliptic integral of first kind of modulus k. Self absorption of a hollow cylindrical source of finite thickness may be approximated along the axis of the source by the following procedure (see Fig. 32). It will be assumed (1) that the source is of uniform unitvolume-activity and density, (2) that absorption occurs only within the source, (3) that scattered radiation due to the absorber will not affect the dose rate, (4) that radiation intensity and dose rate vary inversely with the square of the distance from a point source and inversely with an exponential function of absorber thickness, and (5) that the part of the source lying outside the cone 0 = tan-3 x/(Z3.1L) also fulfills the foregoing assumptions. The resulting differential equation and its approximate integration are as shown in Fig. 33, where P = distance between point and element of volume, p = density, grams per cm3,. = mass absorption coefficient, em2/gram,

V =total activity, curies loo000 millicuries \volume of source, cm3 curie / equiv, roentgens at 1 cm (hour) (millicurie point source)! dv = element of volume of source, and all other terms are defined as above or in Fig. 33. Equations (5) and (8) were applied to both the 1000- and 10,000 -curie sources. In the case of the 1000-curie source, it was straightforward to assume a cylinder with dimensions corresponding to the actual cobalt cylinder. In the case of the 10, 000-curies source, the nest or bundle of.100 rods was assumed equivalent to a cylinder whose inside and outside diameters were the shortest and longest diametrical distances across the rod bundle. The 10,000 curies was assumed to be uniformly distributed throughout this volume and the density of the assumed cylinder was taken so that its mass equalled that of the rods themselves. Calculated and observed values of dose rate for the.10-kilocurie source of cobalt-60 are compared in Tables II and III and are plotted in Figs. 34 and 355. The calculated values were based on an assumed activity of 10,000 curies. The observed values are considerably less than the calculated values. For any given method of measurement the observed values are a nearly constant fraction of the calculated values. In Figs. 395, 40, and 41 appear cross-plots of Equation (5) when the latter is made to agree with data from the oxidation of ferrous ion. The data were taken on the mid-plane on the axis in March, 1953. The source was irradiated at the Chalk River NRX reactor and was rated at 9250 curies on shipment from the Chalk River site in January, 1953. The activity computed from each means of measurement appears in Table IV. In the extreme right column of Table IV there appears the ratio of the curies estimated from observed values of dose rate to the 9250-curie nominal value after correction of the

36 TABLE II DOSE RATES ON AXIS OF 10-KC SOURCE L -Z1 = Distance Above Mid-Plane, cm, R = 0 2 Calculated Rep/hr for 10,000 curies Annular Source Sheet Ferrous Victoreen L L Z1_ - Source Z1- - Oxidation Ratemeter No With No 2 13 March 1953 Absorption Absorption Absorption unless noted 0 1,020o000 830,000 1, 010,000 0 242,000 (.16 March 1953) 6.35 910,000 747,000 928,000 2.5 249,000 12.7 665,000 527,000 662,000 2.5 234,000 25.4 222,000.154,000 218,000 8.9 194,000 38.1 97,000 61,000 96,000 15.2 144,000 63.5 32,000 20.3 6 1,000 21.6 74,000 - - 22.8 - - - 48,000 25.4 - - - 38 000ooo 26.7 42,000 38, 1 16 000 50o.8 8, 81oo 60.8 5,000 76.2 3,5300

37 TABLE III DOSE RATES ON MID-PLANE OF 10-KC SOURCE Z1 = L = 12.7 cm; R = Distance from Axis, cm 2 Rep/hr for Rep/hr for Rep/hr for Sheet Source, Ferrous Oxidation Victoreen Meters R No Absorption. R R Calculation for 13 March 16 March Ratemeter R-Meter 10 000 curies 1953 1953 0 1,000,000. 0 249,000. 242,000 21.3 61;000 0 234,000. 4.85 1,120,000 3.30 243,000 250,000 23.1 52,000 8.70 1,800,000 3.30 248,000 244,000 26.2 43,000. 9.70 o 6.30 281,000 280,000 30.8 32,000 10.7 1,800oo000 6.30 274,o000 292,000 31.8 --- 40,000 12o0 1,150,000 14.7 168,000 38.4 18,500 19o4 379,00. 18.1 86,000 102,000 51.0 --- 15,500 29.1 160,000 20.6 115,000 79,500 64.0 7,500 38.8 92,000 25.7 52,000 73.9 --- 7,500.100 14,000 38.4 24,000 140 1 800 51.0 13,000.165 1,200 89.1 4,400 114.8 2,600 140.0 2,000. 20.6 82,000. 9 June 1953

38 TABLE IV ESTIMATES OF ACTIVITIES FROM MEASUREMENTS OF DOSE RATES Estimate of Activity, Curies 'A' After Value ~Indicates Mean Value Source Measurements Date Self-Absorption was Divided By Where Method Considered Decaye d Taken Arithmetic- Nominal Value Maximum Minimum Mean 10 KC Axis Ferrous Mar. 53 2500 2100 2300 0.26 Oxidation 3100A 2800A 2950A O 33A Victoreen Mar. 53 1700 1400 1550 0.17 Ratemeter 2600A 2500A 2550A 0.28A Mid- Ferrous Mar. 53 2600 2200 2400 0.27 Plane Oxidation Victoreen Mar. 53 2500 2000 2250 0.25 Ratemeter Victoreen Mar. 53 3000 2900 2950 0,33 R-Meter 1 KC Axis Ferrous May 52 140 0.16 Oxidation 180A 0,20A May 53 130 0o.16 170A 0. 21A Victoreen Feb. 53 150 110 130 0.16 Ratemeter 190A 150A 150A 170A 20A Victoreen May 52 170 0.19 R-Meter 230A C0 26A May 53 160 0,20 210A 0.26A

39 latter value for decay. If self-absorption is not considered, the activity is estimated to be from 17 to 33 percent of the nominal value. If selfabsorption is considered, the activity is estimated to be from 28 to 33 percent of the nominal value. These figures are computed from data taken both on the mid-plane and on the axis. No estimate of self-absorption was made on the mid-plane, however. Calculated and observed values of dose rate for the 1-kilocurie source are compared in Table V and in Fig. 36. The 1-kilocurie source was irradiated at Brookhaven National Laboratory and was assumed to have a nominal activity of 1000 curies in July, 1951. The activity computed from each means of measurement is given in Table IVl. The ratios of observed to decayed nominal curies appear in the right column. If self-absorption is not considered, the activity is estimated to be from 16 to 20 percent of the nominal value. If self-absorption is considered., the activity is estimated to be from 20 to 26 percent of the nominal value. These figures are computed from data taken on the axis only, since it was not possible to make measurements external to the source. However, it was desired to compare the dose rates predicted by Equation (5) for the 1-kilocurie source with those predicted for the.10-kilocurie source in order to observe differences caused by the different geometrical proportions of the two sour-es, Consequently Figs 42, 43, and 44 are presented to portray the dependence of dose rate on position in the neighborhood of the 1-kiloclarie source, 7o e data for these figures were computed on the assumption that the source actually contained 1000 curies. Judging from the above results there appears to be about a threefold discrepancy between the curies in the 10-kilocurie source as estimated from ionization measurements and as calculated from neutron absorption. ale comparisons for the L-kilocurie source are not so meaningful, since no firm

4o TABLE V DOSE RATES ON AXIS OF 1-KC SOURCE Z,_L = Distance Above Mid-Plane, cm 2 R=O r = 2,493 cm Calculated Rep/hr for 1,000 curies Measured Rep/hr Sheet z 1L Annular Source Source Z1-L Ferrous Victoreen Victoreen 2 No With No 2 Oxidation Ratemeter R-Meter Absorption Absorption Absorption Feb.53 0 442,000 341,000 460,000. 0 62,300\ 79,000\ May, 52 May,52J 8o75 429,000 336,000 450,000 0 57,200k 72,000O May,53j May,53 17.5 232,000 184,000 240,000.1.3 511,600 35.0 --- --- 15,200 3.8 52,800 87.5 --- -- 900 6 3 54,000 8,9 55,800.11.4 57,500.14o0 46,800 16.5 19,200 19.0 9,300 21.6 5,150 24,2 3,240 26.7.1,860 29.2.1 320 34.2 490

41 estimate of the activity of the source was made by Brookhaven National Laboratory, which supplied the source. The errors in the methods of calculation summarized in Equations (3), (5), and (8) probably arise chiefly from the simplifying assumptions made. The assumption that the source has no thickness is evidently justified by the agreement of values calculated on this assumption with those in which thickness of the source is considered (see Figs. 35 and 36). The results of Tables II and V show that absorption is not negligible. However, in Figs, 35 and 36 it can be seen that the plots from data and from Equations (3), (5), and (8) differ by an approximately constant factor between any pair of curves, This result is interpreted to mean that Equations (3) and (5) may be used within limits to predict the distribution of dose rates without consideration of self-absorption, but that accurate prediction of dose rates requires consideration of self-absorption. The 1-kilocurie source is evidently not of uniform activity throughout its whole volume, This conclusion was reached from a study of Fig. 360 Note that the measured dose rates in the 1-kilocurie source do not vary with distance along the axis in the manner predicted by the calculated curves. The depression near the mid-plane is probably caused by lower unit activity inside the source in this region, The lower unit activity here is probably caused by failure of neutrons in the pile to penietrate to -te interior of the cobalt cylinder near the mid-plane as abundantly as nea- _the ends, The other assumptions introduced are thought to be reasonably acceptable, although Equation (8) converges much more slowly as Z1 is ncreased. The value of 13.5 equivalent roentgens per hour at one centimetell per millicurie point source of cobalt-60 was taken from the work of Marinelli, Quimby, and Hine42, and was assumed to be correct within our experimental erroro

42 Although there were some differences between the chemical and physical dosimetry measurements, they were not sufficiently large to account for the factor of three or four between the nominal activities of the sources and those which result from the dose measurements themselves. It was con.cluded that the methods of analysis of dose rates and the measurements of dose rates were both correct, and that the activities of the sources should be re-computed from this information. The activities so computed are summarized in Table IV. The activities estimated from measurements of dose were about 20 to 30 percent of the values previously estimated from absorption of neutrons. Levin and Hughes34 have recently noted that a factor of about 0,30 should be applied to computed activities in neutron-irradiation of cobalt in order to account for nonuniform distribution of neutrons in the sample being irradiated.

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Xg.. Iressure Reactor in. 10 K.KC (kui:ia 8uwce Room.

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P~~~~~~~~~~~i ivU LEAD PLUG TOP OF LEAD CONTAINER 1000 CURIES COBALT 60 31/4' BOTTOM OF LEAD CONTAINER I/4" STAINLESS STEEL JACKET DRAIN LINE Fig. 27. 1-Kilocurie Cobalt-60 Source with Shielding.

Yi, P. Irl-dA b' TLI I ~ ~ ~~~~~~~~~~ ~~~~~.~. ]~ A —r b:.'.. -.'...- A' *'.. r. '... o. IM DIA. 0-S STAINLESS S1W.. OM 03~~~ IC+ I ~ I ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Lo H-. 2 o I; *' b.. c-f 0::l!.t I~__. a~~~~~~~~~~~~~~ ~~ ~~~~.' "t ".1~'I~. ~'.:'. a ~~.~~~~ (1) I'-'

0.425 DIA. 48 HOLES 0.435 DIA. 52 HOLES ~~~~~~~~~~~b/\ ROD PLATE Q~~~~~~~ I II 3 REQ' DO. II II~~~~~~~~~~~~~~~~~~~~~~~~~~~ II,, IlI K1 III IF~~~~~~~I ii II I, ii 1~ ~, —, -F- - - -t - ~ L~~J________________________ IR~~~~,EQ' D. Fig. 29. 10-Kilocurie Source: Rack for Rods. 49

0.405". - 269" 0.250' A A SECTION BB COBALT 3SH18 ALUMINUM PIPE 1/8 IPS 10 I B B ALCAN 25 WELDINGd ROD SECTION AA Fig. 30. Cobalt Rod for lO-Kilocurie Source. To

P( R,O,Z1 dA Fig. 31. Source with Negligible Wall Thickness. 51

sssaGU'-'PT l TTUM 1 a4T.Jq GOFG at noS 0 c ol C) iT / An! ( LIZ ) d.* ~, ',~M /]Oa / \W,// 'Z:J ) d i... l l- ~~(~~

dl V e EQ. (6) /I r=r1 f V Z =LrddZdr -/Lp(r-rd)csc4 EQ (7) -r, Z ~O=O 0 r2+(Z,-Z)2 if a three-term approximation to the exponential is employed: I =.27rVr2 (tafl ZL - tan 2 L r-aI t' Z ta L) r2 r (2-(r2 rr Zi 2' X z, —. +In In ) +Z,"-,n r2 (,. i +( 1+ r, fo'I-r2,' r2 -2-ta 'ZL taI+-' 2;, - tan T' ta — 2 - r>O, r2>0, rr2 ZI r lI, I r\3 +Z-s- (sn 'i -L 2h Z, 2 _, ZIZ 2 2' ~(r2'Vr~r~)2+l-rI r2+ I' ) + (Z,- L) r, I n, + I' for Z,0, - o ' ZL' ZL< _;

~ 10,000 CURIE POINT SOURCE. u \& -CALCULATED, NO ABSORPTION X 10,000 CURIE SHEET SOURCE -CALCULATED, NO ABSORPTION yV FERROUS OXIDATION MEASUREMENTS, 13 MARCH'53 U A U/ 01 FERROUS OXIDATION MEASUREMENTS, 16 MARCH '53 105 Lru V FERROUS OXIDATION MEASUREcv z s7 MENTS, 9 JUNE '53 z z ~, Y /\+z + VICTOREEN RATE METER MEASUREMENTS, MARCH '53 IAIt /,0OVICTOREEN R METER' tw [ E tMEASUREMENTS, MARCH '53 Ir. LO 10 100 DISTANCE FROM AXIS, CM. Fig. 34. Dose Rate on Mid-Plane of 10-Kilocurie Source.

10 O 10000OCURIE POINT SOURCE -CALCULATED, NO ABSORPTION 0 10,000 CURIE ANNULAR SOURCE -CALCULATED, NO ABSORPTION X 10,000 CURIE SHEET SOURCE -CALCULATED, NO ABSORPTION \A '10,000 CURIE ANNULAR SOURCE ''_ \\' -CALCULATED, WITH ABSORPTION 5 \ \\\ V FERROUS OXrDATION MEASURE105 \ tMENTS, 13 MARCH '53 Lz~ \> \ \ ~~~~~~+ VICTOREEN RATE METER MEASUI\ E u REMENTS, MARCH '53 0 tr~~~~~~~~~~~~~~~l~~l.. 1.0 10 100 DISTANCE ABOVE MID-PLANE, CM. Fig. 35. Dose Rate on Axis of 10-Kilocurie Source.

1,000 CURIE POINT SOURCE -CALCULATED, NO ABSORPTION o 1,000 CURIE ANNULAR SOURCE -CALCULATED, NO ABSORPTION -X 1,000 CURIE SHEET SOURCE -CALCULATED, NO ABSORPTION -A 1,000 CURIE ANNULAR SOURCE -CALCULATED, WITH ABSORPTION ' \ O VICTOREEN R METER MEASURE*cp 105 | \ MENT, MAY '52 I!-> \ \ —t-, VICTOREEN R METER MEASUREQ g-~~~ \_ _~~\- \ MENT, MAY '53.I IV +,\___ FERROUS OXIDATION MEASUREMENT, MAY '53 FERROUS OXIDATION MEASURE\ MENT, MAY '53. \-\ + VICTOREEN RATE METER MEASUREa: \\ MENT, FEB. '53 -.I0,d L... 1,-.. o 10o 1.0 10 100 DISTANCE ABOVE MID-PLANE, CM. Fig. 36. Dose Rate on Axis of l-Kilocurie Source.

U 0 a:: ALL DIMENSIONS IN INCHES AND TO CENTER ~ LINES OF BOTTLES,J ALL BOTTLES GLASS, B.R.SC, 1.3" In DIA. X 2.4"TO SHOULDER r3.82- o ALL BOTTLES VERTICAL DURING LL... __ T IRRADIATION EXCEPT 2,485,WHICH - - 41-1 WERE HORIZONTAL % | I 1SOURCE t,__ U 0 1 - I55.13 I I M.H.C. Fig. 37. Location of Dosimetry Samples for Run 132307 with 10-Kilocurie Source.

~ Ira PLAN 5.8 L. cn SOURCE %SOURCE —t ~ __ ELEVATION M.H.C. ALL at - ] Fig. 38. Location of Dosimetry Samples for Run 132308 with 10-Kilocurie Source. 58

106 _-4 -. -- 12.7 ' l======10==- ==Io a\ wlz4 0 %0 1,1,. 0.0 DISTANCE FROM AXIS, R, CM. Fig. 39. Dose Rates Parallel to Mid-Plane, Interpolated from Measurements with lO-Kilocurie Source.

DOSE RATE WITHIN A CYLINDRICAL PRESSURE REACTOR ALl the foregoing calculations and dose measurements are for points in air lying at different distances from the sources. In the experiments reported on the polymerization of ethylene, the reaction took place inside a stainless-stee.l pressure vessel. The dose rate inside this vessel is certainly not the same as that on the outsidee. Consequently, a series of calculations were made on the intensity of radiation inside the pressure vessel, taking into account the absorption of gamma radiation by the walls of the vessel (see Fig. 46). It is assumed (1) that the source of gamma radiation is a cylindrical sheet of no thickness and of uniform activity per unit area, (2) that the source is transparent to its own radiation, (3) that the dose rate varies inversely with the square of the distance and inversely with an exponential function of absorber thickness, (4) that no absorption occurs inside the reactor, and (5) that secondary radiation from the bomb wall does not affect the dose rate. None quilibrium secondary radiation probably does affect the dose rate in the ethylene but this consideration was neglected in computing the dose rates used to calculate G values for the polymerization of ethylene. Let the terminology be defined as in Fig. 46 and as follows: I = dose rate at P(R,Z), rep/hr; activity of source, curies.1000 millicuries) area of source, cm2 / curie / equiv. roentgen at 1 cm (hr) (millicurie point source). = absorption coefficient, cm 2/gram, taken from Snyder and Powe.ll53; A = area of source, cm2 60

P = distance from dA at P(r,Z,Q) to P(R,Z), P.' = distance through bomb wall, cm; K(k) = complete elliptic integral of first kind of modulus k; kj = 2wOr R+r p = density of bomb wall, grams/cm3; and x = distance in Fig. 45 from source to point at which I is measured. From assumption (3) the:following'e quation may be written: dI = -ktIdx - 2Idx (9) x Integration and substitution of limits yields the expressions: I2 = (xl) I1 (10) I4 = (X3_2 Is (11) X4 13 - 2)2 e-I(x3-x2) (12) 12 \X3/ Combining Equations (10), (11), and (12) results in the expression: I4 = (xl\2 I1 e-l(X3-X2) (13) \x4/ From Equation (13) we may deduce that the location of an absorber is immaterial as long as it is between the source and point P. Thus only the thickness of the absorber need be considered. Now Equation (16) may be written for dose rate on the axis of the bomb (see Figs 46). P' = b csc, (14)

62.csc, _ / R2 + r2 - 2Rr cos Q + (Z_-Z)2 (15) R2 + r2 - 2Rr cos Q and dI = O dA e- pP'. (.16) p2 Equation (16) must be integrated over the entire source, as shown by Equation (17). A three-term approximation to the exponential is employed. Z=L =T: I = 2 arddZ f 1 g: Z= o 8,_ ardedZ i R2 + r2 - 2Rr cos o + (Z1-Z)2. Z-_ 9= 0 O _ bp (17) 4R2 + r2 - 2Rr cos 0 + (Z1-Z)& R2 + r2 - 2Rr cos 0 + j2b2p2 1 21' (R2 + r2 - 2r cos e) f The first term within braces has been integrated above, in Equations (3) and (5). Integration of Equation (17) yields Equation (18): 2ccr [F(tan-1 Z1, kl) - F(tan- Z1-L kl)] R+r lr-R ' Ir-RRI - 2bp Z=L K(k).dk + trL2b2p2 (18) 1 - (k/kl)2 R2 _r Z1-Z=Z1-L where k = k1 (z1-Z) 4/(R-r)2 + (Z,-Z)2 Equation (18) holds for Z1 > L > 0, O < tan2l Z1-L tan'l Z1 <, R r $ 0 - - |lr-R! Ir-R I 2

If, however, L > Z1 > 0, R $ r 4 0, then I 2 2 2r [F(tan- l Z, kl) - F(tan-1 Z1-L, k )] R+r.Ir-R I Ir-RI Z,-Z=O, z —Z=Zl - 20albp pI K(k) dk + Kk 1 - (k/k[1)2 1- (k k2 -I-Z=Z1-L Z1-Z=O + ccrLT2b2p2 (19) R2 - r2 Since k, defined above, is the modulus of an elliptic integral of the first kind, 1 > k> 0 Consequently, for Equation (.19) the following definitions are employed. k- = -k (Z z) for Z1 > Z:(R_r)2 + (Z.,Z-)2 k1 (Z -Z1) for Z > Z1 /(R-r)2 + (Zi_z)2 If Z1 > L > 0, R = 0, r > 0 then I = 2 Utc (tan-l ' - tan-l (Z,-L) ) r r (20) - 2 azbpic ln ( Zz + lr2 + Z12 ) + czxL42b2p2 (Z1-L) + r2 + (Z1-L r where 0 < tanl1 (Z), tan'- (Z1-L) < r/2 r r

64 If, however, L > Z1 > 0O R = O, r > O, then I = 2 ca. [tan'l (ZL) + tan-' (L-Z1)] r r - 2 caibpt in [[(L-Z1) +r2 + (LZ- )2] [Z1 +r+Z) (21) r2 + oL~2b2p2 r where 0 < tan'l (Z1), tan-l (L-Z1) < /2. In Equations (18) and (.19) r r terms of the form:. K(k) dk 1 - (k/kl)2 may be integrated graphically. The above expressions have been evaluated for both the 1-kilocurie source and the 10-kilocurie source with reference to the stainless-steel pressure vessel, Fig. 1. The locations studied are indicated in Fig. 47. In Fig. 48 dose rate is plotted against vertical position inside the reactor for the 1-kilocurie source, while Fig. 49 is a similar plot for the.10-kilocurie source. The dose rates for the location of the bomb in the center of the source were calculated separately, and are not shown in Fig. 49. In Fig. 50, the data of Fig. 48 are averaged and plotted against time, assuming that cobalt-60 has a half-life of 5.3 years. In Fig. 51 the data for the 10-kilocurie source (from Fig. 49) are plotted similarly against time.

106 R.8.73 Rx 10.67 R"4.85 r R:19.40 C. R- 38.9 W R' 77. 6 _ _ I _I__ 1 _ _ _ _ 103 on~. 0.1 1. 10 100 DISTANCE FROM MID-PLANE, --, CM. Fig. 40. Dose Rates Parallel to Axis, Interpolated from Measurements with l0-Kilocurie Source. 65

! 50 E Lu 41 aJ n CL 30 IJ w~~~~~~~~~~~~~~~~~~~~190 REP 2:x~~~~~~~~~~~~~ ~HR REP 50000 P 20000 IHR!1 HR I RE _,, ~ ~~ 300,000, I~ L L -, 0 - 0 -O, o030 450 60 70 80 o90 DISTANCE FROM AXIS, cm Fig. 41. Isodose Surfaces Interpolated from Measurement with l0-Kilocurie Source.

106 mI I1 I0T T I I IOX o -- = W 0 4 - OS0.1 DISTANCE FROM AXIS R, CM. Fig. 42. Calculated Dose Rates Parallel to Mid-Plane with 1-Kilocurie Source. 67

106 R-3.06 =_ RO CM _ I RQ 10.72CM2 a - _. I' w 100 0.l 1. 10 L I ' ' DISTANCE FROM MID-PLANE,, —,CM. Fig. 43. Calculated Dose Rates Parallel to Axis with l-Kilocurie Source. 68

50 ~ 40 4 bJ 30. HR '0..... REP HR ~10 '~ 'lo " 20 30 4b 50 6o 70 DISTANCE FROM AXIS,cm Fig. 44. Calculated Isodose Surfaces with l-KiLlocurie Source. 69

POINT (P) AT WHICH DOSE RATE IS TO BE MEASURED SOURCE ABSORBER x2 II x3 x4 XI S X2 3, X3 4 Fig. T5. Diagram for Attenuation by Distance and Absorption.

a o w Fig. 46. Diagram for Dose Rate Inside Pressure Vessel. 71

PRELIMINARY INVESTIGATIONS A survey of the literature relating to radiation chemistry indicated that few reactions appeared to be accelerated sufficiently by gamma radiation alone to warrant serious thought of commercial exploitation. -However, much of the data reported was secured with the aid of relatively small sources of radiation. It was desired to check some of these results, employing the l-kilocurie and the 10-kilocurie gamma sources of cobalt-60 at the University of Michigan as described by Anderson, Martin, et al. 5Y8 Synthesis of Ammonia Of the various reactions reported in the literature to be accelerated by radiation, the synthesis of ammonia appeared promising. Boulle2 investigated the influence of cathode rays and of various metallic catalysts on the kinetics of the ammonia synthesis. D'Olieslager and Jungers21 investigated some effects of alpha radiation, as did Lind40, using alpha rays from radon. In Gmelins Handbuch26 are reviews of numerous articles dealing.with attempted syntheses of ammonia by the use of radiation and electrical discharges. It was thought that if gamma radiation would accelerate the ammonia reaction at a given temperature, then perhaps prevailing industrial rates of reaction could be secured at lower temperatures than those commonly used. Lower temperatures would result in a more favorable percentage of ammonia at equilibrium. Such a circumstance would have permitted the designer of an ammonia plant additional options in the choice of processes to be employed. Harmer6 attempted in this laboratory to synthesize and to decompose ammonia at atmospheric pressure by cobalt-60 gamma radiation. The results 72

73 failed to indicate the formation or decomposition of ammonia in any experiment. Nessler's reagent, alkalimetry, and combustion tests were used to analyze for ammonia and for hydrogen. It was suspected that the low density of the synthesis mixture and the attendant low absorption of gamma rays were responsible to some extent for the failure to obtain measurable yields of ammonia. However, increasing the pressures to about 100 atm also failed to produce measurable yields, as shown by some tests made at 1200 psig and room temperature. Palladium-109 beta radiation and the pressure vessel illustrated in FigS 1 were used in these tests. The use of the analytical methods mentioned above for the atmospheric tests indicated no measurable formation of ammonia. The data appear in Table VIJ TABLE VI IRRADIATION OF MIXTURE OF NITROGEN AND HYDROGEN WITIH PALLADIUM-109 BETA RAYS Pressure, psig Page Time Curies Temper~~~~~~~~~Page 3000 lb/gm, n6t No. Elapsed, Time Date Pd-109 ature, hrs 1st Foil Calibrated F N~ H,2 (by Total. di.ff. )f 124214 0 2100 17 Jan 52 1.2 300 800 1100 70+5 0.75 2145 750 70+5 11.6 0835 18 Jan 52 0.95 705 70+5 Reactor vented to 505 psig at 11.6. Effluent gas passed through Nessler's reagent. Negative test for ammonia. However, Selke et al.46 have obtained measurements of the yields of ammonia in similar experiments, using more sensitive methods of detection. These workers47 reported yields up to 0.00oo46 mole percent of ammonia in a reaction mixture of nitrogen and hydrogen exposed to gamma radiation. The investigation of the ammonia synthesis was suspended after the above results became known. Fortunately the possibility of wishing to

74 study different reactions had been foreseen in the design of the equipment for studying the ammonia synthesis. Consequently, it was possible to adapt the equipment to the study of other reactions without difficulty. Beta Radiation from Palladium-109 We were also interested in the use of beta radiation as well as gamma radiation for the purpose of promoting chemical reactions. It had been thought that beta radiation, being more completely absorbed than the gamma radiation, would be correspondingly more effective in promoting chemical reactions. The following experiments were devised in order to test this idea when some sources of beta radiation became available for the use of the author and co-workers. These sources were three pieces of palladium-109 foil varying from about 20 to about 100 curies of initial beta activity and were originally procured in connection with some other experiments of the Engineering Research Institute of the University of Michigan. Beta radiation from palladium-109 was used in an attempt to synthesize ammonia from its elements. See the description of this work under "Synthesis of Ammonia". Some experiments were conducted as described below in order to test the effect of beta radiation on the rate of drying of some natural oils. A foil of palladium-109 was wrapped in a pliofilm sheath and laid over a l/l4inch galvanized wire mesh separating it from weighed samples of several different natural oils. Each oil sample was placed on a 2,5-cm-diameter watch glass. A control test, differing only by the absence of radiation, was also set up. Each test was allowed to run for one week. The results are summarized in Table VII. The experimental setup is shown in Fig. 52. From the data in Table VII-it was eoncluded that the irraldiation of drying oils with Pd-109 beta radiation did accelerate the drying of some of the samples tested. The effect was of relatively small magnitude, however, and

TABLE VII RESULTS OF IRRADIATION OF NATURAL OILS WITH PALLADIUM-109 BETA RAYS Foil received 1 March 1952. Percentage Remarks Material Gain in Weight R Test Control Test Control Raw eRaw e+7.8 +0.53 tough, rough film no change Linseed Boiled +5.7 +7.0 tough, rough film tough, rough film Linseed Degummed +5*8 +0.39 tough, smooth film no change Soya Castor +1. 3 -0.58 no change no change Refined Refined+93 +4.5 tough, smooth film no change Menhaden Cottonseed 0Cottonseed -o.36 -0.19 no change no change Pitch Schedule of above irradiation Curies Remarks Time Date Pd-109 3rd Foil Temperature, 70-80~F 3rd Foil............ 0300 2 Mar 52 120 Start irradiation of oils o800 2 Mar 52 100 0800 3 Mar 52 33 0800 4 Mar 52 14 o800 5 Mar 52 7 o800 6 Mar 52 4.5 0800 7 Mar 52 3.4 o800 11 Mar 52 2.1 1400 11 Mar 52 2.0 End of irradiation of oils

76 it was niot considered worthwhile to secure more beta sources to continue the investigation. Partial Polymerization of Natural Oils It was desired to investigate the effects of gamma radiation on some natural fats and oils. Data reported by Sheppard and Burton48 indicate extensive decomposition of several fatty acids irradiated with alpha particles from radon. Burton'X5 reported decarboxylation, polymerization, and hydrogenation of Oleic acid irradiated with deuterons. Coolidge'6 reported on the solidification of castor oil by cathode rays outside the generating tube. Partial polymerization or "bodying" is a necessary step in the processing of some natural oils, and is accomplished by means of prolonged heating under vacuum. A long induction period at high temperature, followed by a rapid reaction, indicated that the reaction proceeds by a free-radical mechanism. The prolonged heating may be needed to form free radicals in sufficient concentrations to initiate the desired reaction successfully. There is evidence that free radicals are formed in some materials by gamma irradiation (see the work of Allen ). If free radicals could be formed at the outset instead of by the slow process of thermal formation, then the desired polymerization might follow almost immediately. The experimental procedure used in testing the effect of gamma radiation from Coe~ on refined soya oil was as follows. Samples of oil in glass containers were irradiated in the l-kilocurie vault for aboult 24 hours and then were heated in a glass flask by an automatically regulated gas flame. The flask was evacuated to an absolute pressure of about 1 millimeter of mercury. An air-cooled condenser was connected in series with a water-cooled condenser and the two were placed between the vacuum pump and the flask. Nordco No. 460 grease was used on all standard taper joints.

77 Data for these tests are given in Table VIII. Samples irradiated and then heated for 6 hours were more viscous than samples not irradiated but heated for 6 hours. The effect appeared to be small, however. The complexity of the reactions in bodying of natural oils is so great that it would be difficult to assess the effects of radiation alone. A study of the bodying of TABLE VIII CHANGES IN VISCOSITY OF SOYA OIL AFTER IRRADIATION AND SUBSEQUENT BEATING The starting material used in each run was dry, refined, degummed soya oil....* Pre s sure, Run Irradiation Temper- Time of Viscosity mm Mercury, No. aptuxe, 'F- Heating, hr. G-H Poises A&bsolute 11 24 hr, Coso 572 6 N+1/3 3.5 1 12 __ 572 6 J 2.5 1 13 24 hr, Coso 572 6 L 3.0 1 14 24 hr, Cd60 572 6 L 3.0 1 15 -- 572 NG-air leak ->- - )12 16 24 hr, Co60 572 6 L 3.0 1 17 -- 572 6.3 L 3.0 1 18 -- 572 6.2 J 2.5 1 19 5 — 72 6 J 2.5 1 26 24 hr, Co6O 600 6 Z4 63.4 1 27 -- 600 NG-air leak -- -- >10 28 24 hr, Co60 600 6 Z4+1/4Z5 69.4 1 29 -- 600 NG-boiled over.- 1 30 -- 600 6 Zl+2/3Z2 33.0 3 31 -- 600 6 Z3+1/2Z4 54.8 3-4 Donated by Wyandotte, Michigan, plant of Archer-Daniels-Midland Company.

78 oil by irradiation would not be worth while from -an industrial point of view unless a large increase in the rate of reaction could be achieved* Since the effect studied was found to be small, it seemed desirable to drop the work on natural oils and to work instead with some relatively simple, pure materials in order to be able to isolate the effects of radiation. Further work might be done by studying the chemical changes in pure componernts of the oils when subjected'-to irradiation as described above. Polymerization of Acetylene A preliminary test was made of the polymerizing effect of gamma radiation on acetylene. Mund and Koch43 and Lind and Bardwell37 had reported the polymerization of acetylene by alpha rays from radon. Rosenblun45 reported the formation of benzene by the irradiation of acetylene with alpha rays ferom radon. In the following work acetylene was irradiated under pressure in order to find possible evidence of the polymerization of acetylene to benzene under gamma radiation. Acetylene was irradiated with 1.,9 x 106' rep in air of cobalt-60 gamma radiation, The acetylene was dissolved in acetone which had first been absorbed in a dried mixture of Portland cement and asbestos. The cakes of cement were placed in the pressure reactor (Fig. 6), which was fitted with an aluminum rupture disc designed to burst at 150 psig. The reactor was evacuated with the cement in place, flushed with nitrogen, and evacuated again. Then 105 grams of acetone was added and acetylene introduced until an equilibrium pressure of 5 psig was reached,.The reactor thus charged was irradiated for 24 hours, after which the volatile contents were recovered by immersing the reactor in hot water and heating the discharge pipes with infrared lamps, Subsequently, the reactor was evacuated while being heated in the manner just described, During the heating and evacuation all effluent.material was passed through dry-ice traps. The

79 condensed liquid was distilled in a Podbielniak column, where it was observed that the overhead temperature during the distillation was not significantly different from that of acetone. About 0.2 gram of a brownish, waxy solid was recovered from the pot of the column. This material was insoluble in acetone. No further work was done along this line because of the small yield and indefinite nature of the product. Chlorination of Kerosene and of Benzene Attention was then turned to investigating the influence of gamma radiation on chlorinations. Alyea3 reported the addition of chlorine to benzene under alpha radiation from radon. The chlorination of hydrogen under ultraviolet light was studied by Lind and Livingston39. The first chlorination studied in this laboratory was that of kerosene. Gaseous chlorine was dissolved in a sample of kerosene. The sample was divided, one half placed in the 1-kilocurie vault and the other half retained in the dark. After irradiation of the test sample both samples were shaken with sodium hydroxide pellets and analyzed for total organic chlorides by the method of Liggett35. The data of Table IX indicate no difference between the irradiated and unirradiated samples. The reason for this behavior is probably to be found in the fact that all samples were allowed to stand one week before being analyzed, during which period chlorination probably proceeded to the exhaustion of chlorine both with and without radiation. Consequently it seemed wise to compare the kinetics of the irradiated and the unirradiated reactions. However, it was thought that such a program of study should be carried out on a pure compound instead of kerosene, which is of uncertain and variable composition. It was tentatively plamnned to use benzene for these studies. A test by Harmer indicated a rapid, nearly complete reaction of benzene and chlorine to hexachlorocyclohexane under gamma radiation, SlatorS and Luther and Goldberg4l have noted

TABLE IX IRRADIATION OF MIXTiRRES OF KEROSENE AND CHLORINE IN 1-KC COBALT-60 GAMMA SOURCE Pres- Avg. Dose Total Per- Date Page Start sure, Temp. Hours Rate Dose Sample centage, of Remarks No. Date ATM,ABS oF Irrad. Kilorep Kilo- No. Chlorine Annaly_ --- O- - - e. per hr......., sis 124216 1 Feb 52 1 70 -- zero -- 1 1.68 10 Mar 52 Duplicate detns,, 1.66 unirradiated 1 70 24 63 1500 1 1.42 14 Mar 52 Duplicate detns., 1.42 irradiated o 124245 1 Mar 52 1 70 -- zero -- 2 1.36 14 Mar 52 Duplicate detns., 1.37 unirradiated 1 70 24 63 1500 2 1.38 14 Mar 52 Duplicate detns., 1.36 irradiated For sample No. 1, Chlorine was dissolved in two separate portions of kerosene and one was irradiated. For sample No. 2, Chlorine was dissolved in a single portion of kerosene. This was divided in two, and one half was irradiated.

81 a similar catalytic effect of ultraviolet light on this reaction. Subsequent investigations conducted in the apparatus portrayed in Fig. 53 indicated that the yield of gamma isomer, valuable as an insecticide, was nearly the same as that ordinarily achieved industrially with the aid of ultraviolet light, i.e., about 12.5 percent by weight of the products of chlorination. This yield was also nearly independent of temperature in the region investigated, i.e., 14~F to 680F. Recrystallization and extraction procedures were used on some samples to achieve some separation of isomers. A melting-point bar of the design of Dennis'8, Fig. 54, was constructed to assist in this work. Table X summarizes the data obtained from this series of runs. Oxidation of Sulfur Dioxide Backstromlo and Alyea and Backstroms reported the investigation of the oxidation of sulfur dioxide, both in ultraviolet light and in the dark. Oxidations of sulfur dioxide were attempted by three procedures. In the first method sulfur dioxide and oxygen were simultaneously bubbled through water in a vessel in the 1-kilocurie vault. The apparatus used was nearly the same as that of Fig. 53, used for the benzene hexachloride experiments. Iodometric-acidimetric titrations as described by Bodenstein and Pohll" were used to determine sulfurous and sulfuric acids in the tail-gas scrubbers and in the reactor. Sulfate was determined gravimetrically (Willard and Furmants) in both the reactor and tail-gas scrubbers. The results appear in Table XI. In the, second procedure sulfur dioxide and oxygen were admitted to the reactor of Fig. 1, which had previously been evacuated. A heater was silver-soldered to the copper leads inside the reactor. The heater consisted of 18 gauge chromel-A wire coiled on a 1/8-inch arbor, stretched

TABLE X IRRADIATION OF MI:XIrRES OF BENZENE AND CHLORINE IN 1-KC COBALT-60 GAMMA SOURCE Pres- Avg. Dose Percent Page Start sure, Temp. Hours Rate Total Percent Carbon Percent* No. Date AATM of re- Irrad, Kilo- Dose Benzene tetra- Gamma Isomer ABS action, ~F rep/hr Rep (by vol) chloride in Benzenehexa(by vol ) chloride 129771 11 Aug 52 1 68 0.42 64 27 10 90 11.3 (over chlorinated) 129770 11 Aug 52 1 68 0.33 64 21 20 80 12.5 129773 12 Aug 52 1 14 0.73 64 47 10 90 12.3 129774 12 Aug 52 1 14 0.55 64 35 30 70 12.8 *Analyses through courtesy of E. I. du Pont De Nemours and Company, Engineering Service Division.

TABLE XI IRRADIATION OF MIXTiRES OF SULFTR DIOXIDE AND OXYGEN IN 1-KC COBALT-60 GAMMA SOURCE Average Percentage Sob Converted Dose Rate to So03 Based, on So.2 Page Start Temp. Hours Dose, to Sv3 Based on So2 No. Date F Irrad. ~Kilorep/hr Kilorep Recovered in Reactor Frocedure by iodine by gravimetric method method 132184 9 Jan 53 70 1.5 62 93 4.4 --- aqueous So2+0 132189 13 Jan 53 70 1.1 62 68 6.1 6.7 aqueous So2+02 132192 16 Jan 53 70 o.6 62 37 10.6 6.4 aqueous So2+02 132179 16 Dec 52 65-240 2.8 29 81... 1.3 gaseous So2+02 132194 19 Jan 53 56-510 none -- 4.4 3.2 liquid So2+02 132198 4 Feb 53 296-400 4.3 28.5 120 3-7 1.8 liquid So2+02 TABLE XII IRRADIATION OF PROPYLENE Page Start Hours Dose Rate, Temp,, Pres, Remarks No. Date n Irrad. Rep/hr Dose, Rep F psia 132140 6 Feb 53 1735 0 29,000 0 71 147 2.8-in.-depth liq. propylene in bomb; 3000-lb gauge. 132140 9 Feb 53 1313 67.6 29,000 2,000,000 66 145 Out of vault. 132140 18 Feb 53 1000 -- __ _ -.. Room 25-30 0.2 —0.3-in. -depth liquid in bottom, quickly evaporated.

84 to double the close-wound length, and inserted into a 10-mm-ODo pyrex tube. The tube was then bent into a "U" shape to fit inside the bomb. The reactants were heated by this hot-wire heater while being irradiated in the l-kilocurie vault. Samples of gas were absorbed in standard iodine contained in an Orsat pipette, using mercury for the levelling fluid. Shrinkage of volume was measured, Then the contents of the pipette were back-titrated with thiosulfate and then with alkali. In addition some of the gas was absorbed in water and sulfate was determined gravimetrically, as for the aqueous solutions described above. The results appear in Table XI. A third procedure used to study the oxidation of sulfur dioxide was to liquefy sulfur dibxide in the open body of the reactor, Fig. 1, seal the reactor, warm to room temperature, and place the reactor in the 1 -kilocurie vault. The assembled reactor, or bomb, was then heated to a temperature of about 500'F, and oxygen was slowly bubbled into the liquid sulfur dioxide. The bomb was cooled, the gas vented and absorbed in water, and the sulfurous and sulfuric acids determined by iodomnetric-acidimetric and by gravimetric methods, as before. Results of these tests also appear in Table XI. Under the conditions used, irradiation evidently did not accelerate significantly the oxidation of sulfur dioxide. Reaction of Carbon Dioxide with Hydrogen A test was made to determine whether carbon dioxide and hydrogen would react in the presence of gamma radiation. The purpose of this work was to test the possibility of formation of formaldehyde and similar oxygenated hydrocarbons. Carbon dioxide was therefore introduced into the evacuated bomb to a pressure of 680 psia. Hydrogen was added until the pressure was 1070 psia, and the bomb was then irradiated in the l-kilocurie source for 16 hours in November, 1952. No reaction was observed.

Polymerization of Isobutylene Polyisobutylene is of some importance as a plastic, and an attempt was therefore made to polymerize isobutylene by means of gamma radiation. Isobutylene was liquefied in the open body of the bomb; the bomb was then sealed, warmed to room temperature, and irradiated for about 100 hours in the 1-kilocurie source. The irradiations took place at intervals over a period extending from July to October, 1952. The contents of the bomb were vented to a dry ice trap. About 103 ml of liquid was obtained. The contents of the trap were then poured into a still flask through a vertical condenser cooled by circulating methanol which had been indirectly cooled by dry ice. The still flask was heated by warm water, a reflux was maintained in the vertical condenser, and the overhead was conducted to a dry-ice trap. The distillate was colorless liquid, presumably isobutylene, and the residue left in the flask was a dark straw color. The residue amounted to about 1 ml and had an odor similar to a terpene. Polymerization of Propylene Liquid propylene was irradiated for 67.6 hours at a dose rate of about 25,000 rep/hour, and the results are reported in Table XII. A small quantity of a volatile liquid was found in the reactor when it was vented and opened. Some polymerization therefore took place, but the yield was not measured. Polymerization of Ethylene Acetone and ethylene were introduced into the pressure reactor and irradiated. Some fluffy white powder was obtained. The acetone was added originally to release free radicals on radiolysis and to initiate the chain polymerizatiorn of the ethylenes

86 Discussion of Preliminary Investigations If gaseous systems are subjected to higher pressures, their densities are increased. The resulting increased densities cause increased absorption of gamma radiation. Consequently a reaction promoted by gamma radiation in a gaseous system should be accelerated by increased pressure. Accordingly, some preliminary work was undertaken as noted in the preceeding section, to find reactions occurring under pressure which would be accelerated by gamma radiation, Pressure reactions promoted by gamma radiation -would be interesting from an industrial point of view because the radiation can pass through the walls of pressure vessels and promote reactions where other forms of radiation-could not be used., The polymerization of ethylene appeared to be the most promising reaction in this.category to study further. The yields of polyethylene obtained were not large, but were somewhat larger than those for any of the other reactions studied, except for the chlorinations. In addition, polyethylene is one of the most important of the industrial plastics, and there is currently great interest in the development of manufacturing facilities for this material. Accordingly, further investigations were confined to the study of the polymerization of ethylene by means of gamma radiation.

PLAN A D.S. DENOTES ELEVATION OF DOSE STATION AT ALL RADIAL POSITIONS OF BOMB B C D E D.S. D.S. SOURCE 10-Kilocurie Source. II AIII_. -s~ei. tgi D.S. SOURCE 5" ELEVATIOON Fig. 47. Location of Pressure Reactor for Dose Rate Studies with l0-Kilocurie Source. 87

In N DATA OF P 132327, VICTOREEN RATEMETER, CALIBRATED BY OXIDATION OF FERROUS SULFATE 80,000 c (M 70,000 - OPEN VAULT 60t001&00 50,OOC' - j_0_ -~o,ooo o~ / ~~~~~~~~~~~~~~~~~~~~~~~~~~O~~~~~~~~~~~~~~~~~~~~~~~~~ BOMB BODY IN VAULT 40,00.00 30,000 - DOSE RATE, AVERAGED OVER VOLUME OF BOMB: 27,500 B 0 HR co w a w 20,000. -Q _ z~~~~~~~~~~~~ Z eo - w o e~~~~~~~~~~~~ ir, ul 10,000-o A, 0.I- ~ 0 0 0o _._4 8 12 16 20 24 28' DISTANCE ABOVE BOTTOM OF VAULT, INCHES Fig. 48. Dose Rates Inside Pressure Reactor with 1-Kilocurie Source. 88

100,000 R, RADIAL DISTANCE, BOMB TO, SOURCE, -6 INCHES 0~~~~~~~~~~ 80,000 co ~0~~~ ~o 80,000 O I\ o nm 06 0 0 a. 2 0 o I. — I — I — al 0 7r. 60,000 zJ z~~: 50,000 QL ccr 0 40,000 Rs =8 INCHES 30,000 VALUES CORRELATED WITH CHEMICAL DATA9, AND CORRECTED TO I JUNE 5J 20,000O 10'00: RxI5INCHES -I 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 DISTANCE ABOVE OUTSIDE BOTTOM OF BOMB, INCHES Fig. 19. Dose Rates Inside Pressure Reactor with lO-Kil~ocurie Source. 89

POLYMERIZATION OF ETHYLENE Prior Work Ethylene has been polymerized under various conditions, yielding polymers of widely different properties. At temperatures of 572-12920F and pressures of 0.2 to 70 atmospheres, ethylene has been polymerized to liquids in the presence of iron, silica, or zinc chloride (Ellis22). Such liquids have been of interest principally as fuels for internal-combustion engines and have consisted of mixtures of lower olefins and paraffins. Ethylene has also been polymerized by the use of catalysts cdnsisting of peroxidese2,64,67, or elementary oxygen29,63, as well as by the use of other catalysts32 65, to yield products of molecular weights varying from a few hundred to tens of thousands. Such polyethylenes display physical properties ranging from oils when of lower molecular weight to waxlike solids when of intermediate molecular weight and plastic solids when of high molecular weight. These materials are used for a variety of purposes. Planned capacity for the production of polyethylene was reported by Stenerson54 to be about 200,000 tons per year by 1955. Peroxide- or oxygen-catalyzed reactions were conducted at temperatures of 32 to 752~F by Robertsonieand by Roedel%9, although the lower or middle range of temperatures is often preferred in order to produce materials of higher molecular weight. Pressures of 1000 to 2000 atmospheres are often used in order to obtain materials of higher molecular weights. Ethylene has been polymerized at 77~F and about 1 atmosphere by Lind, Bardwell, and Perry38 using alpha radiation from radon to initiate the reaction. The products were liquids reported to be olefins of higher molecular weight, and also gases, reported to be hydrogen and methane. 90

91 Ethylene has also been observed to polymerize when irradiated with ultraviolet light. LeRoy and Steacie 33 noted that the metal sensitizers cadmium, zinc, and mercury accelerated the polymerization of ethylene irradiated with ultraviolet light and simultaneously caused some dehydrogenation to acetylene. In this work temperatures ranged from 77 to 572~F and pressures from 15 mm to 400 mm of mercury absolute. Danby and Hinshelwoodl7 investigated the polymerization of ethylene by ultraviolet light at 572~F and pressures to 400 mm of mercury absolute, as sensitized by acetone, by diethyl ketone, and by acetaldehyde. Taylor and Emeleus56 found that the polymerization of ethylene was photosensitized by ammonia at 68 to 212'F and 5 to 15 cm of mercury, and the same authors found57 that methyl and ethyl amines at 2 to 25 cm of mercury and temperatures to 3920F showed similar behavior. These reactions were studied in the gas phase; solid polyethylene was not isolated or studied. Ethylene has been polymerized by gamma radiation. This reaction has been studied by Bretton et all3 at 1 atmosphere and at temperatures ranging from room temperature to 372~F. The products were solids, usually yellowish or brown in color. Other properties of the solids were not reported. Polymerization of Ethylene by Means of Gamma Radiation Investigative Procedure. As was noted in the section on Preliminary Investigations, one or two initial tests indicated that ethylene could be polymerized by gamma radiation at moderately high rates. As explained above, these observations formed the basis for the decision to study this reaction in greater detail. The results obtained on resumption of this work were disappointing, however, since the later runs produced very erratic results. Moreover, as noted in Table XIII, the yields decreased ConSiderably.

T A BLE X II I IRRADIATION OF ETHYLENE Order Page Starting Avg. Avg. Grams Houra 0-Moles Reacted Averaged over Reactor OhrPsto fClne Av.Temp., HoIrrs Polysmr A =(trcTnMgae) Dose Rate Total Dose Othr u Psitoeof M ylide Ho. Ho. Date IntalFna sa -F Plmr Ird e or (Mti oT —g —p lorep/Hr Mgrp Reactants Sore Reactor Mf. No. Remark 2 132113 19 Dec 52 850 785 822 69 1. 6, 69.7 0.02+ 608. 29. 2.02 1 Ml acetone 1 Inc -- Matheaso FF 737 - 3 132118 12 Jan 53 820 795 822 70 o.666 61. 0.011 291. 28.9 1.76 - 1 ke —",,4 132147 3 Mar 53 1430 1330 1395 230 0.292 17.2 0.017 485. 29.3 0.507 — 10 Inc 8" NE 9" UP 5 13149ii Ma 53 820 700 77 50 o.004 0.9 0.0003 12.7 42. 0.666 -o1 Inc 8" NE 9", up 132149-II7Mar53 435 424 4515. 1 132159 26 Hov 52 790 780 Soo 68 0.394 42. 0.009 258 29.5 1.24 1 Ml acetone 1kIc "6 132250 10 Mar 53 810 715 777 50 0. 167 16.2 0.010 94.5 96. 1.55 IL1 k on (L. 1keBase at Bane - 7 132252 11 Mar 53 1430 1330 1395 200 1.04 16.1 0.06 513. 82.5 1.33 -10 Inc Do. 8 132253 12 Mar 53 698 692 710 45 1.48 87.7 0.017 423. 42.0 3.69 — 10 Inc 8" NE 9" up 630 psi N2 and 9 1532254 17 Mar 53 635 655 660 45 -- 23.3 -- -- 42.o 0.979 l5 paiaii lo ke 8" NE 9"up" vent, chg. C2H4 10 132255 18 Mar 53 800 710 770 45 0.088 21.5 0.004 865. 42.0 0.904 lo1 Inc 8", NE 9" up 11.132256 19 Mar 53 84o 760 815 420 0.381 15.3 0.0259 1800. 29.3 o.448 — o1 kc 8", NE 9" up 12 132258 23 Mar 53 810 70 455 45 0.010 39. 0.0003 12.5 41.9 1.63 10Ml1 Inc —"" Lk acetone La 13 132259 26 Mar 53 788 183 485 61 -- 15.3 -- —. 95. 146on O o as 95.5.46 0 kcBaseat Bane - 14 132263-i 4 may 53 i6oo 1425 1528 72 -- 21.9 -- -- 27.7 o.6o8 — 1kIc 15 132263-II 5 May 53 620 595 623 72 0.022 23. 0.001 45.8 27.7 0.6.38 — 1Inc 16 132264 7 May 53 615 600 622 69 <0.0001 20.7 <0.000005 <0.25 27.6 0. 572 100 Ml 02 1kIc - 17 132265 8 May 53 620 608 631 67 <0.0001 21.4 <0.000005 <0.24 27.6 0.591 25 Ml 02 1kIc 18 132266 9 May 53 594 577 601 72 0.034 25.6 0.0013 67.5 27.5 0.703 5.0 Ml 02 1kIc - 19 132267 10 May 53 600 575 603 75 -.0.00l 17.0...o-ooos.'. 3.1 27.5 o.468 2.0 Ml 02 1 kc - 20 132268 11 May 53 617 597 622 70 0.017 22.3 0.0008 36.6 27.5 o.613 10.0 Ml 02 1kIc - 21 132269 12 May 53 60s 590 612 71 0.030 21.1 0.0014 71. 27.5 0.581 10.kl02 1Ic 22 132270 13 May 53 637 629 638 66 o.o16 14.8 0.0011 30. 27.5 0. 407 5.0 Ml 02 1kIc - 23 132275 4 Juni 53 530 525 553 70 0.031 16.8 o.o02 94. 31.3 0.526 lo1 Inc 8", SW 13-7/8" UP 24 132276 7 Jul 53 490 490 505 76 0.021 22.1 o.ool- 63. 27.0 0.597 23 mm air 1kIc - 1 Ml acetone 25 132277 8 Jul 53 46o 460 475 78 -- 20.1 -- 0.0 27.0 0.543 95 Ml air 1kIc - 1 Ml water 26 132278 9 Jul 53 460 455 473 73 o.ou1 18.3 o.ooo6 43.1 27.0 0.494 C215a 1kIc - 27 132279 10 Jul 53 445 440 458 n.75 0 136 69.8 0.002 147. 27.0 1.88 33 ma S02 1kIn - 28 132280 13 Jul 53 426 39 425 87 Loat, sevE al 16.5 -- -- 27.0 0.44"6 458g grams tar 4.98ga11nc3 29 132281 14 Jul 53 430 420 44o 81 0.013 20.0 0.001 32.2 27.0 0.540 — 1kIc - 30 132282 15 Jul 53 420 410 430 79 0.657 23.2 0.028 184. 27.0 0. 627 1 atm. S02 1kIc - AS02 = 575 31 132284 16 Jul 53 420 385 417 83 2.692 16.1 0.167 241. 27.0 0.43.5 55 psia1 Inc — "" AS0 = 3380 S02 0 32 132285 17 Jul 53 393 70 246 83 30.9 64.o 0.483 2450. 27.0 1.73 23.98 gm l1kc- AS 24800 S2022 33 132287 20 Jul 53 400 390 410 -- -- -- - -0 o 27.9 gm -- 34 132293 3 Aug 53 810 790 815 80 0.208 17.0 0.012 357. 26.8 0.456 S -2 1kIc -- Ohio Chem. 028087 - 35 132294 4 Aug 53 930 910 935 76 o.472 21.8 0.022 443. 26.8 0.584 — 1kIc 36 132295 5 Aug 53 615 610 628 76 0.010 16.0 o.ooo6 30. 26.8 0.428 Al~n. pyrog~allol 1kIc - Matheson FF 737 - 37 132297 6 Aug 53 955 950 968 75 4.45 71.5 0.0623 7.50. 26.8 1.91 - 1kIc - Powdery, soft lumpsm ht 38 132350 10 Aug 53 320 320 335 75 0.005 15.7 0.0003 35.6 26.8 0.421 — 1kIc 39 132351 11 Aug 53 985 965 990 80 0.084 16.3 0.005 67. 26.8 0.437 — 1kIc 40 132353 12 Aug 53 94.5 930 950 75 o.085 14.6 o.oo,6 112. 26.8 0.392 — 1kIc 41 132354 13 Aug 53 86o 84o 865 80 0.150 16.3 0.009 234. 26.8 0.437 — 1Inc 42 132355 14 Aug 53 870 815 857 74 1.70 63.6 0.0268 638. 26.8 1.70 — 1kIc 43 132356 17 Aug 53 935 900 932 70 0.309 11.8 0.0262 509. 26.7 0.315 - 1kIc - Ohio Chem. 02807 - 44 132357 18 Aug 53 875 870 888 72 o.428 18.5 0.0231 551. 26.7 0.494 — 1kIc 45 132359 20 Aug 53 1015 970 1002 75 nO.005 17.4 O.'...002 7.3 26.7 o.465 — 1kIc -- Matheson 5772 - 46 132360 21 Aug 53 920 86.5 907 74 2.6 66.8 o.o4o 802. 26.7 1.78 - 1kIc - 47 132361 24 Aug 53 825 785 820 79 -- 15.7 -- 0.0 26.5 0.416 — 1kIc 48 132362 25 Aug 53 975 946 975 79 0.o29 14.o 0.0021 28.0 26.5 0.372 — 1kIc Carhide In small to medium lups 49 132363 26 Aug 53 1200 1000 1115 90 21.5 116.5 o.185 2380. 26.5 3.09 - 1kIc - and.1K 370331 slightly off white, mdrtl Carbon coherent 50 132366 5 Sept 53 1010 924 98o 77 4.9 90.5 0.o541 70 26.5 2.40o- 1kIc - Matheson 5772 Powdery, in small, sotlms white 51 132369 9 Sept 53 1005 925 980 73 -- 17.0 -- 0.0 26.5 0.451 - 1kIc - Carbide 32 132370 10 Sept 53 1000 970 1000 70 1.5 21.3 0.0705 790. 26.5 0.565 - 1kIc - and.JK 370331 - Carhon 53 132372 11 Sept 53 513 475 310 60 0.16 34.5 o.ooh64 298. 26..5 0. 912 Acetaldehyde 1kIc - Matheson 5772 - 34 132373 14 Sept 53 1500 960 1245 ".70 51.3 262.7 0.195 2200. 26.5 6.97 - 1k Ha —2d to he cut out of ho.Ra fines, all coherent,wht 55 132375 25 Sept 53 1370 1080 1315...65 43.6 71.8 0. 607 1915. avg; 89.6 6.43 - 10 Inc On - Had to he cut out of ho.Ra fines, all coherent, int 17.0 29.5 0.50 -- 1kIc 56 132376 30 Sept 33 1780 1110 1430.79 12.3 23.7 0. 18 avg: 745. avg; 89.5 2.1-2 — 10 Inc on out. ChInd.I 1065 White, soft powder, vr ml up 28.8 58. o 1.67 -- 10 Inc -~ ot Chm

93 At first it was thought that the decrease in rate of reaction was caused by the presence of oxygen in the system, and therefore a number of runs were made in which a known amount of oxygen was introduced. Although the results of these runs showed a dependence of the extent of reaction on the amount of oxygen, as shown in Fig. 55, the effect was far smaller than the decrease in reactivity from the early runs to the later runs (see Figs. 56 and 57). Therefore, it seemed unlikely that oxygen alone could be re sponsible for inhibiting the reaction. Other ideas were therefore advanced in order to account for the ers ratic polymerization rates observed. It was suggested that some polyethylene might be present in the storage cylinders and introduced during charging of the reactant to the pressure reactor; however, the conditions usually required for the polymerization of ethylene were unlikely to have prevailed in the storage cylinder. Another possibility was that some unknown inhibitor was present erratically, or that some unknown promoter was absent erratically. The substances most likely to fall into these categories were 'impurities in the ethylene, gases from the air, materials used in cleaning the reaction equip-~ nient, and the reaction equipment itself. The latter possibility was tested tentatively by allowing polymer to accumulate on the walls of the reactor and then checking the rate of reaction in a subsequent run;, no influence on the rate of reaction was noted. The influence of various solvents and other.materials thought possibly to have been present accidentally in the successful runs was checked by adding the following materials successively to separate batches of the reactant ethylene: acetone., acetaldehyde, air and acetone,,

94 powder sought. The addition of sulfur dioxide resulted in the production of a white powder at relatively high rates of reaction. However, this powder proved to have a sulfur content rather close to that of the equimolar addition product of sulfur dioxide and ethylene. See Fig. 58. Matthews and Elder61 and Snow and Frey52 have reported similar reactions between sulfur dioxide and olefins under ultraviolet light. Next the composition of the reactant gases was examined in some detail. The ethylene was analyzed (see Table XIV) immediately on removal from the storage cylinders, after charging to the reactor but before irradiation, and on removing from the reactor after irradiation. Components determined were "soluble in bromine", carbon dioxide, oxygen, carbon monoxide, paraffin hydrocarbons and nitrogen. Higher olefins and acetylenic compounds were not detected separately by the methods used. series of tests was made in order to remove posble oxygen or other volatile gases from the ethylene. The bomb was evacuated, ethylene was charged under cylinder pressure, and then the ethylene was condensed by ilmmersing the bomb in a flask contaj.nilng dry ice. The bomb was then vented until the pressure had dropped to a predetermined value or until a given Volume of gas had been released. The ethylene was then vaporized and the bomb and contents irradiated as before. Experimental Procedure. In this work ethylene was irradiated with.cobalt-60 gamma radiation while at room temperature and at pressures of 250 to 1600 pounds per.-square -inch pressure. Some tests were made in which ethylene was reacted alone and some in which the ethylene was mixed with other reactants. A stainless-steel bomb (Figs. 1 and 2) was used as the. reaction vessel.. The bomb was evacuated to a pressure of less than 1 mm-of mercury

TABLE XIV ANALYSES OF ETHYLENE FROM STORAGE CYLINDERS AND FROM REACTOR Material MgCO %~ CO ON 'f Combustible Number of Mfg. %CO2 %02 %co %~~~~N2 No. as marked Determinations 1 Math o.o6 0.02 0.02 0.15 0.1 propane? duplicate FF737 2 Math o0.06 0. 02+ 0.00 0.07 0.29 propane duplicate 5772 OC 73 OC 0.10+ 0.02+ 0.00+ 0.47 total ethane? single sample G28087 - -o C ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~and 4 C and C 0.37 0.02 0.05 1.7 0.8 pentane triplicate JK370331 5 USI o0.08 0.05 O.005(? ) 0.21 0.45 methane duplicate IC-1065

TABLE XIV (cont) ANALYSES OF ETHYLENE FROM STORAGE CYLINDERS AND FROM REACTOR Material Dose G Page %0* %~* fo N Combustible Number of Determinations o. No. 02 * as marked 4 3.09 2380 132363 0.37 0.02 0.05 0.00 3.8 ethane duplicate; first sample of 0.62 0.07+ 0.07 1 1. or more 0.06 0. 02 O. 00 2 2.40 730 132366 06 002 0.12 0.14 ethane(?) duplicate 2 0.45 0 126 036 0.02 0.00 0.22 total -?- duplicate 2 o.45 0 132369 0:02 0.05 0.01 0.346 0.02 0.00+ 40.543 0.02 O.01+ 2.49 total -?- duplicate 0.05+ 0.005 0.00 o.o6 0.02 0.00 2 6.97 2200 132373 0.05 ~0.01 0.00 0.09 0.18 methane single 0.11 0.02 0.00 3 6.43 1915 132375 0.11 0.02 o oo 0.16 0.32 ethane (?) single 4.29 745 152576 o o8 0.05 o.005(?) 0. 0.63 methane single 5 0.07 0.009 0.00 o.291 745 132372 o.o7s+ og o0 *Top, before irradiation (no removal by distillation and no addition to ethylene unless noted) Bottom, after irradiation

97 0-kilocurie source until the proper dose had been accumulated. After irradiation, the bomb was removed from the source, the unreacted ethylene was vented and analyzed by an Orsat analyzer and the accumulated polymer was removed mechanically.. Results of Polymerization of Ethylene. A white, solid polyethylene resulted from the irradiation of ethylene with cobalt-60 gamma rays. The yield ofpolymer was found to be quite small until the system had received a dose of about 1/2 megarep. The yield increased rapidly to a value of about 2500 gram-moles reacted/(metric ton)(megarep) at about 3 megarep, and remained nearly constant up to doses of 7 megarep, the highest dose studied (see Fig. 58)4 (It should be noted that 1 gram-mole reacted/(metric ton)(megarep) is equivalent to 0.97 molecule reacted per 100 electron-volts.) About one-third of the monomer was polymerized in three days in the center of the -kilocurie source. The thermodynamic properties of ethylene were taken from the work of York and White60 Discussion of Folymerizatio n of Ethylene From Fig,. 58 it can be seen that the yield of polymer per unit of energy absorbed from the radiationthe G value for the reactionis a function -of the total dose of radiation,. This relation is evidently due to the presence of an induction period for the reaction. No correlation could be observed between-contents of the following gases in the monomer and the yield as a function of dose:. carbon dioxide, oxygen,, carbon monoxide, hydrogen, paraf-~ f in hydrocarbons, nitrogen, and sulfur dioxide. It appeared., however, that the venting of noncondensable gases from the liquid ethylene did increase the initial rate of reaction to some extent. The data for the analyses of gases

98 that errors exist in the method of calculating the dose rates used in estimating the G values. A Victoreen ratemeter was used to measure the dose rates on the axis of the bomb. This instrument would detect the secondary photons produced by scatter from the wall of the bomb, but probably would not detect the scattered electrons. These scattered electrons would be quite effective in producing chemical reaction because nearly all their energy would be imparted to the chemical system. Consequently it can be seen that more ionization probably occurred than was taken into account by the calculations, in which the effect of the bomb wall was neglected. The effect of this error is that the G values given are too high. On the other hand, as a calculation device, the pri y beam was assumed to undergo no appreciable absorption within the ethylene in the bomb. Rather, the beam was assumed to maintain within the bomb a value which would be attained in the axis if the bomb were full of air. It was recognized, of course, that absorption within the ethylene was assumed to be causing the reaction If account were taken of absorption of primaries within the ethylene, then somewhat greater credit for 'initiating reaction would have to be given to each primary photon, and this would increase the G values given. Thus., neglect of nonequilibrium secondaries and neglect of the absorption gradient of primary gamma intensity within the ethylene compensate each other to some extent. 'The importance of accounting for the above errors in dosimetry is recognized. However, the complexity of the problems of.measurement would seem to indicate the desirability of pursuing this work further in future studies. Therefore, the values given for G in Fig. 58 should be regarded as relative rather than absolute., since all determinations

99 Elevated temperatures were investigated only briefly, but preliminary results indicated that considerably increased rates of polymerization would result in irradiated systems at temperatures of 200-400(F as compared with those obtained at room temperature. Evaluation of the Polyethylene Product General. The polyethylene obtained as a result of gamma irradiation of ethylene was subjected to a brief program of evaluation. The properties considered most basic to an understanding of the material were investigated. Most experimental work was concerned with determinations of solution viscosity, melt viscosity, density, and tensile strength. Melting points of some samples were also determined. Molecular weights were estimated from te determinations of viscosities of solutions and of melts. Crystallinity was estimated from determinations of density. The other measurements were made by conventional means. These measurements-and derived qucantities probably need no further explanation, with the exception of the concept of crystallinity of a polymer.The degree of crystallinity of a polymer is measured by the degree to which the molecules of polymer are arranged parallel to each other. An arrangement of parallel molecules results in a repetitive structural pattern such as that found among the molecules of a crystal. A random orientation of molecules similar to a pile of jackstraws might be expected to be less dense than a parallel arrangement such as that just described, and it has been found that percentage crystallinity may be correlated with the density of polyethylene (see Kirk-.Othmer31'). Some explanation is given in the following paragraph of the manner of presenting the data obtained from experiments on

100 The properties of the polyethylene are presented as functions of the radiation yield of the polymerization reaction because of the reasons given below. In addition molecular weight and crystallinity are presented as functions of dose. The radiation yield of the polymerization of ethylene may be expressed as the G value, the number of molecules of ethylene which undergo polymerization for every 100 electron-volts of energy absorbed from radiation. Lind6 has shown that in many gaseous systems, approximately one molecule reacts per ion pair formed in the system. In the irradiation of ethylene a variable number of molecules, usually much greater than one, react for each ion pair formed. The polymerization of ethylene is therefore evidently a chain reaction. For this calculation it is assumed that one chain is initiated for every ion pair formed, that all cbains are of equal length, and further that the formation of each ion pair requires 32.5 electron-volts of energy, a value approximately correct for gases at one atmosphere. The densities of ethylene under the conditions of reaction were greater than at one atmosphere and therefore the energy required per ion pair may be quite different from the value given. The G value may therefore be divided by three to give the approximate number of molecules reacted for each ion pair formed, and this result may then be multiplied by the molecular weight of the monomer in order to arrive at the molecular weight of the polymer.. Consequently., the G value is directly proportional to the molecular weight which would be expected of the polymer if the above assumptions held. Furthermore, the properties of a polymer are frequently found to be functions of 'its molecular weight. It therefore seems advantageous to consider the properties of the polyethylene as functions of the G value.

101 where it is indicated that the G value was about 0.1 to 1.0 until about 0.5 megarep had been received. The G value then increased rapidly with increasing doseuntil it reached a nearly constant value of about 2000 molecules er 100electron-volts for doses of about 3 to 7 megarep. Experimental. All the samples of polyethylene were white. Some were fluffy powders and others were tough, coherent masses. Portions of each of the samples of polyethylene which occurred in yields of 4 grams or more were molded into sheets as an operation preliminary to further examinations. A two-compartment mold was used, one compartment at a time. Samples were placed between aluminum foil in the mold, preheated to 000F pressed to 1000 psi, and cooled to about 125~F under pressure The resulting sheets were 2.5 by 4 by 0.025 inch. All such sheets proved to have the characteristic milky, translucent appearance of polyethylene. The sheets molded from the powders were brittle, while those from the tough reaction products were also tough. Molecular weights were estimated from viscosities of solutions., measured as follows: Solutions of some samples were prepared in concentrations of 0.01 percent and of 0.125 percent by weight in tetralin. Viscosities of these solutions and of the tetralin were measured in modified Ostwald pipettes at 212'F. Specific viscosities were calculated and divided by the respective concentrations. The resulting ratios were plotted as a function of the concentration of polymer, and the plots were extrapolated to zero concentration to give intrinsic viscosity. Intrinsic viscosity was assumed to be directly proportional to molecular weight. The concentration was computed in units of gram moles of monomeric ethylene per liter of solution. The constant the molecular-, i - weiht f Bkelte Y~ to agre wihte-au of 20,000- for

102 value of the constant was computed in this way to be 0~42 x 0 liter per gram. See also the work of Tani 5 on intrinsic viscosities of polyethylene in tetralin. The method of Dienes and Klemm20 was used to estimate molecular weights from melt viscosities. Viscosities were measured in a parallelplate plastometer with an attached dial gauge reading to 0.01 millimeter. The entire assembly was placed in an oven. Temperatures of 28F and of 266F were used. The samples were placed between sheets of aluminum foil about 1-1/2 mils thick. The thickness of the sheets of foilwas measured in the plastometer before each determination. Crystallinity was estimated by correlation with density (see KirkOthmer ). Densities were determined by the use of Archimedes principle. Weighings were made directly in water, after the sample had first been degassed by use of reduced pressure while it was immersed in water. TIIensile properties of the polyethylenes were examined by the following procedure. Specimens for testing were cut from the molded sheets by means of a die. The resulting specimen~s were 0.079 by 0.025 inch in the smallest cross section. The narrowest section was 1-1/2 inches long. Tension was applied in Gardner-Parks testing machine shown in Fig. 266 of Gardner 24.. This machine had a capacity of 2.5 kilograms. Melting points were determined on a melting-point bar of the design of Dennis 183(see Fig. 54). Discussion. The results of evaluation of the properties of the radiation-polymerized polyethylene are summari zed in Table X-J. -The molecular weight is plotted as a function of radiation yield in Fig. 60. The molec

TABLE XV PROPERTIES OF POLYETHYLENE PRODUCED Page Dose, Radiation Melting Density Ultimate Elongation, Crystallinity Molecular Weight Page ~~~~Point OF g/m[ Tensiley b et b Number Megarep Yield, A Point F g/cm Tensile Percent Percent by Melt by Solution _ _ _ _ _ Lower/upper _ _ psi at rupture Viscosity Viscosity 132250 1.55 95 219/226 132268 0.61 37 216/225 132269 0.58 71 205/217 132276 0.60 63 207/214 132281 o.54 52 196/205 132297 1.91 750 241/244 0.951 450 4 77 26,300 insol. 0 132362 0.37 28 234/235 132363 3.09 2400 248/689 0.941 2200 42 71 34,400 insol. 132366 2.40 730 210/248 0.951 770 2 77 28,100 4200 132369 o.45 0.1 132370 0.57 790 205/252 88oo00 132372 0.91 298 199/207 insol. 132373 6.97 2200 234/720 0.943 2100 29 72 40,500 insol. 132375 6.43 1900 241/610 0.941 2300 79 71 37,300 insol. 132376 4.29 745 241/244 0.951 630 3 77 11,900 3700 Bake lite Bakelite 0.921 1500 550 61 21,800 20,000 DYNHa assume

weight average molecular weights, based on the weight average molecular weightof Bakelite DYNH of 20,000 (see Table XV). However, differences in crystallinity and cross linking, mentioned above, may invalidate the comparison of the thermally polymerized. sample with the radiation-polymerized samples.. Determinations of molecular weight by melt viscosity may be subject to similar criticism. As shown in Figs. 60 and 61, the molecular weights determined by solution viscosity do not agree well with those determined by melt viscosity. Neither do the molecular weights fromsolution viscosity appear to display any regular variations with dose or with G value, in contrast to the regular behavior of molecular weights from melt viscosities. The reasons for these discrepancies are not clear. Values of crystallinity are plotted as a function of radiation yield in Fig. 6. The crystallinities varied from about 77 percent for samples of low radiation yield to about 71 percent for samples of high radiation yield. All these samples were of considerabely higher crystallinity than was the Bakelite DYNTI1, which had a crystallinity of a~bout 61 percent. It is possible that the radiation-polymerized. samples were of higher crystallinity than the thermally polynerized sample of DYN1I because the temperature of polymerization was lower for the- radiation-polymerized samples. The samples of low radiation yield would be expected to be more highly crystalline than those of high radiation yield., since radiation yield has been shown to increase with dose (Fig. 58), cross-linking and branching would probably also increase with dose, and increases in either cross —inMking or branching would cause decreased crystallinity. TenileproerIe are I ' reore In term of stress asa fucto

105 have higher tensile strengths and are more ductile than those subjected to lower doses of radiation. Such behavior would be likely if the irradiation increased cross-linking and branching. The Bakelite DYNH shows the characteristic elongation of several hundred percent before rupture. See KirkOtmer1, p. 942. Ultimate tensile stress as a function of radiation yield is plotted in Fig. 63. The ultimate tensile stress increased markedly with radiation yield and consequently with dose. A set of structural properties such as those just described for the radiation-polymerized polyethylene might be desirable for certain applications, but the properties differ from those of most polyethylene currently marketed. Melting points are plotted as a function of radiation yield in Fig. 64. Curves are given for both -the upper and the lower ends of the melting-point range. The results show tha-t there 'is a small increase 'in the temperature of initial softening with increase in radiation yield., and that there is a large increase in the temperature of complete melting. The higher melting points indicate higher degrees of cross-linking as a result of the higher doses of radiation, and are thus in conformity with the results of the other determinations mentioned above.

zj 0 _ _ __DATA OF 132 327, REFERRED TO CJ o a. FERROUS SULFATE, IKC SOURCE, 0.. Go - 60 (HALF-Li FE 5.3 YRS.) o W 0,~ o0o 40 H- 0 H0~ (1) I ~t-o 0 g ~~w 4 H H* I s.! Z P- FJ- - (D 020 0 H. ('D 1.0 0 0 JUN DEC JUN DEC JUN DEC JUN 51 51 52 52 53 53 54 DATE

CALM REFERRED TO FERROUS SULFATE 60 IOKC SOURCE, Go-60 (HALFLIFE 5.3 YRS.) 0 ' o o Czli t:S G0. ~ a'q ~ -,..,.,.....,.~. R= 6-5/8" n lx BODY ONLY 40 D- co R:8" w BODY ONLY H~. I-. P-, -- R= r d ~[ Lw BODYONLY U) CD- o (D~~~( ~~~~CD~~~~k IJ R-15" loCD ____________ ____________ __________ __ " -- -- — _'-' _ BO DY ONLY C) 0 0~~~ DEC JUN DEC JUN DEC JUN DEC 52 53 53 54 54 55 55 DATE

r3) 4 'N't -" X 1/16 THICK WATCH GLASSES kA!) __,_ |__ 1 l - 2K 4" TIMBER BASE PLAN / ~COVER OF POLYETHYLENE FILM -< ~ Pd 109..... "~ 11 1/4 X 1/4 GALV. STL. MESH 2 RUBBER BANDS 4 ELEVATION Fig. 32. Apparatus for Drying of Natural Oils by Palladium-109 Beta Rays. 108

LINE ______________________ ~~~~~~~~~~~~~~~~~~~~~~~~~L. & N. CHROMEL - ALUMEL MICROMAX THERMOCOUPLE LEADS TAIL GAS MANOMETER RUBBER STOPPER SEALED WITH DE KHOTINSKY CEMENT D GAS MANOMETER CONTROLLEF VENT GLASS GROUND JOINT CHLORINE RUBBER STOPPER LINE GLASS REACTOR N.C. RELAY METHANOL RETURN METHANOL FEED -~~ WTR/ASI SPLASH GUARDS IC IC -BUBBLERBUBBLER BUBBLER COBALT -60 GAMMA 0 RAY SOURCE REACTANT (BENZENE & CARBON TETRACHLORIDE) THERMOMETER CARBON TETRACHLORIDECHLOROFORM -DRY ICE INSULATION LEAD SHIELD METHANOL STEEL JACKET NITROGEN AIR MOOR Fig. 55. Flow Sheet for Additive Chlorination of Benzene in Cobalt-60 Gamma Ray Source.

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14 121 0 0 oVt1 10 Dl 0 10 '0 _ __ __ _ _ _ _ (D 0 w( C)2 ('D (/, o 0( o O H~~~~ o 0 ct 0 P::l I-. (D 1 o ( L —=j 3:2... (D w,~~~~~~~~~~~~i k,. CD i 0 10- 20 30 40 50 60 70 80 90 100 MILLILITERS OF OXYGEN ADDED AT STP

2.0 1.3 1.8 0,,V 1.6 ~~P' ~~cn ~C P m cr I C+ H 0 ~Pi~... 0 0 *~ CCD o 0 W 1.2... H ~ ~ ol - o " zii c:C+~~~ 0. IIHo a. o 0.6 2 4 6 8 10 12 14 16 18 20 22 24 ORDER NUMBER OF RUN I —b P,'0e2 2. 4 6 8 I0 12 14 16 18 20 22 24 ORDER NUMBER OF RUN

0.028 0.026. 0.024 -.. 0.022 -. 0.020 0 % 0.018 Clf) 0.016 IL o 0.010 0 0.008 w O. 0.008 3tJ 0.006 0.004 -. 0.002 I i.L 0 2 4 6 8 10 12 14 16 18 20 22 24 ORDER NUMBER OF RUN Fig. 57. Rate as Function of Order of Run in Polymerization of Ethylene. I-__.__~~~~~~11

ooo,, YIELD OF ADDITION PRODUCT OF SULFUR DIOXIDE AND ETHYLENE a z I I IVYIELD OF POLYETHYLENE a. XR w CL E10 100,,2. o i 4 0 -O OEVx W POLYMERIZATION OF ETHYLENE J5 x BY IRRADIATION WITH Cr6o W GAMMA RAYS O CONDITIONS N AMBIENT ROOM TEMPERATURE Q2 ~ O 250 TO 1600 PSIA PRESSURE w 0 o 0 PRESSURE VESSEL EVACUATEDAND a. CHARGED WITH ETHYLENE o X NON-CONDENSIBLE GASES VENTED 2 )FROM LIQUID ETHYLENE 2 SULFUR DIOXIDE ADDED TO Q1Q: ETHYLENE pc I.0 O HER REACTIONS w A ADDITION PRODUCT OF SULFUR DIOXIDE AND ETHYLENE 0.1 am-6 0- _ IIII.0 2 3 4 5 6 7 DOSE, MEGARER Fig. 58. Radiation Yield as Function of Dose of Radiation in Polymerization of Ethylene. 114

3.0 I I z INTRINSIC VISCOSITIES OF o POLYETHYLENE FROM is. ~~GAMMA RADIATION;IN TETRALIN 100 ~ 0.05 ~C 0 0.5 CONCENTRATION, WEIGHT P —ERCENTAGE 0 c.

5 0 x o 4 w 0 z wI FROM MELT VISCOSITY -J 0 w3 I0~~~~~ 0. o 0 a. -J 0 t.. 0~~~~~ -J 0 FROM SOLUTION VISCOSITY bIJ ~~~0 0 500 1000 1500 2000 2000 30 wz ~ ~ ~ RDTOYIEDGRAM MOLES REACTED RADIATONMETRIC TON x MEGAREP Fig. 60. Molecular Weight as Function of Radiation Yield of Polyethylene.

CRYSTALLINITY BY DENSITY, 70 60 50,000 ___50 z I..I 40,000 L 40 - MOLECULAR WEIGHT W BY MELT VISCOSITY o ~~I ~~~~~~~z 30,000 1 1 W C.a W 20,000. 20 0 0,000 10 MOLECULAR WEIGHT BY SOLUTION VISCOSITY 0 " 0 2 3 4 5 6 7 DOSE, MEGA REP Fig. 61. Molecular Weight and Crystallinity as Functions of Radiation Dose for Polymerization. 117

2500 'l-wr.x 132 375 2. 132 363 2000,1500 1000 132 366-ULTIMATE 1 132 376-ULTIMATE ~500, e - 132 297-ULTIMATE 500 0 I 2 3 4 5 6 STRAIN Fig. 62. Stress-Strain Plots for Test Specimens of Polyethylene. 118

PERCENTAGE CRYSTALLINITY 71 72 73 74 75 76 2400 0 2200 2000 e~~~~~~~~~~~~~ a. w 1800 w U3X b.z o0 1600,o PERCENTAGE C_.3 I D - CRYSTALLINITY w E oULTIMATE TENSILE STRENGTH 1400 1200 > 2O z 0 5 0 00 1000 400 800 1200 1600 2000 2400 2800 3200 ULTIMATE TENSILE STRENGTH, PSI Fig. 65. Crystallinity and Tensile Strength as Functions of Radiation Yield for Polyethylene. 119

GRAM MOLES POLYMERIZED RADIATION YIELD) A METRIC TON X MEGAREP 0~ - m.~ o0 m b b b 'o O 'o - N ~~~~~ 0 00~~~~0 0 0 0000 - 0 0b0 0 0 0 0 0 0 0 0 0 0 _ _ ~ ~~~ro GI * ~0 o'Q~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. 0 cfh U) ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Z 0 0 rll (9~~~~~~ GI 0 I -0 CO) o 0 ~d~u 0 P. 0 C+ r-q o -Iz (D 0 0 0 1-d 0 0 0~~ cI-? el H (D D _ _ _ _ _ _ _ __I_ _ _ _

SUGGESTIONS FOR FUTURE WORK IN TIE PROMOTION OF CHEMICAL REACTIONS BY GAMMA IRRADIATION Polymerization of Ethylene It would be of interest to investigate further the polymerization of ethylene under gamma radiation with the objective of determining the cause for the induction period observed for the polymerization. It seems possible that small concentrations of impurities are responsible for the induction period. However, it is also possible that such an induction period 'might be characteristic of the gamma-induced polymerization and independent of chemical parameters. If the ethylene could be caused to polymerize immediately on subjection to radiation at the same rate observed after the induction period, then a continuous process for the polymerization might be developed. Such a procedure would permit closer control of those properties of the polymer which are dependent on total dose of radiation. It would also be interesting to study the electrical properties of the polyethylene made by gamma irradiation. As mentioned above, lander "Discussion of the Polymerization of Ethylene, elevated temperatures in conjunction with irradiation caused greater rates of polymerization of ethylene than did irradiation alone. It would be interesting to investigate further the influence of both elevated temperatures and irradiation on the polymerization of ethylene. Some suggestions for such a program were advanced by Anderson, Martin, et al., based on some of the foregoing studies of radiation chemistry and on the work of Kennard30. 121

122 Other Reactions The reaction between ethylene and sulfur dioxide proceeds rapidly enough under gamma radiation that it should be possible to secure much information concerning the behavior of this reaction. It would be of interest to determine the physical properties of the resulting polymer when molded into massive form. The acceleration of the drying of natural oils appeared to be interesting in preliminary experiments (Table VII). Additional work on this topic might be of interest. Since chlorinations appear to be a class of reactions generally promoted by gamma radiation, it would be of interest to procure data on rates and yields of such reactions. Such results could then be compared with other methods commonly used to initiate the chlorination reaction.

CONCLUSIONS From the foregoing work the following conclusions were drawn: (1) Ethylene was polymerized by exposure to gamma radiation from cobalt-60. The rates of reaction were sufficiently large that further work on this reaction appears to be promising. (2) Polyethylene formed by gamma irradiation was subjected to a preliminary evaluation. The polymer was found to be denser, less ductile, and of a higher ultimate strength than Bakelite DYNH polyethylene. Molecular weights of the radiation-polymerized materials increased with dose of radiation to a value of about 40,000 when estimated from melt viscosities. Most samples were insoluble in tetralin and estimates of molecular weights from solution viscosities were not conclusive. Crystallinities estimated from densities varied from 71 to 77 percent. (3) Benzene reacted with chlorine in the presence of gamma radiation from cobalt-60 to form benzene hexachloride at large rates of reaction. The benzene hexachloride was found to have a content of the gamma isomer of about 12 percent, or approximately the same as that resulting from the reaction activated by ultraviolet light. (4) The polymerizations of soya oil, acetylene, isobutylene, and propylene were accelerated to small extents by gamma irradiation. The oxidation of drying oils was accelerated by palladium-109 beta-irradiation. (5) The synthesis of ammonia from nitrogen and hydrogen, the oxidation of sulfur dioxide, and the reaction of carbon dioxide and hydrogen were not measurably affected by cobalt-60 gamma irradiation. 123

124 (6) With the exception of reactions such as the polymerization of ethylene and certain chlorinations, most of the chemical systems examined were remarkable for the small magnitude of any effects caused by gamma radiation originating in 1/4 to 3 kilocuries of cobalt-60. Such information may be regarded as indicative of the relative stability toward gamma radiation of many chemical systems. (7) The activities of the cobalt-60 sources were calculated from measurements of dose and were found to be about 30 percent of the values obtained previously from nuclear-reactor calculations. (8) It was found that no unusual difficulties resulted from the operation of a pressure vessel at 2000 psi and 50 to 400~F within a hollow cylinder of cobalt-60 encased in aluminum.

APPENDIX Design Data for Bomb (1) Design conditions: 2000 psig, 650~F. (2) Maximum operating conditions: same as for (1). (3) Materials of construction: AISI type 304 stainless steel with AISI type 347 rod in welds. Bolts: ASTM A-193. Nuts: AISI type 304 plate, bored perpendicular to plane of rolling. Gaskets: 1-1/4-inch-I.D. x 1-1/2-inch-0.D. x 3/32-inch thick singlejacketed asbestos gaskets with copper cladding. Electrical fittings: Fixed Nitrogen Research (as described by Ernst23) with Teflon pressure cones. Tubing fittings: Fixed Nitrogen Research and Ermeto fittings. (4) Designed according to recommendations of the ASME Boiler Code, Section VIII4. Parts of the design were checked by the methods given by Sliepcevich51 (5) All welding radiographed. (6) Bomb and auxiliary tubing subjected to 2800-psi hydrostatic test before use. Assembly Instructions for Bomb (1) Clean the interior and the gasket seats. (2) Check to see that all passages are open. (3) Assemble electrical fittings, Teflon cones, and electrical and thermocouple leads in head. 125

126 (4) Check electrical leads for continuity and grounds. (5) Attach carefully to the head any internal fittings to be used. Use special rack to hold assembly during this operation. (6) Screw body-flange on body. (7) Place body in holding rack. (8) Place gasket on seat or in retaining groove. (9) Place head on body. (10) Assemble bolt studs and nuts but do not tighten. (11) Tighten the head bolts. Use alternate tightening sequence, checking separation of flanges by means of a feeler gauge. (12) Attach tubing and auxiliary fittings to head. Operating Instructions for Bomb (1) Attach pressure gauge to external fittings for safety, even if not required for operation. (2) Attach rupture disc, suitably anchored, to external fittings. (3) After assembly of the bomb, test for leaks with soap solution, and then test with a Freon alcohol-lamp assembly. (4) If internal fittings are in used in'the bomb, vent the pressure slowly to avoid overstressing the internal fittings. Definition of "Radiation Yield" Below is described the method used for reporting the yields of polyethylene produced by gamma irradiation. The quantities A, B, and G, mentioned below, are referred to elsewhere as the radiation yield. It was desired to report yields of chemical reactions in the units generally used, such as the quantity G, mentioned by Burton'l. G is the yield of a reaction in terms of molecules reacted per 100 electron-volts of energy absorbed from radiation. However, it was also desired to report yields in terms more closely related

127 to engineering usage. It was observed that both requirements could be met by an arrangement which will now be described. The observation was made that the yield in units of G, molecules reacted per 100 electron-volts absorbed, is numerically almost equal to the yield reported in units of what we have called A, gram moles reacted per metric ton subjected to 1 megarep. This relation is demonstrated below: gram moles reacted 1 602 x 10.23 molecules metric ton metric ton x megarepj gram mole l0. grams x megarep x gram x rep 1.6 x 10 12 ergs 1.00 (electron-volts) 10'; rep 93 ergs electron-volt 100 electron-volts = 1.04 x gram moles reacted x molecules x metric ton x megarep metric ton x megarep gram mole x 100 electron-volts molecules reacted 'G, 100 electron-volts Therefore A gram moles reacted G molecules reacted ' metric ton x megarep 1T04 ' 100 electron-volts By means of a similar procedure, the following relation can also be established: pound moles reacted G molecules reacted metric ton x megarep 51 100 electron-volts This method of reporting yields was applied as follows. The yield of polyethylene in grams was divided by the molecular weight of ethylene, 28.04, to give gram moles reacted. The weight of ethylene charged to the bomb was estimated from measurements of pressure and temperature and from the data of York and White 6o. The weight of ethylene charged was computed in units of metric tons, and therefore is the weight of material assumed to absorb radiation. The dose rates used in this work were values averaged

128 over the length of the axis of the pressure vessel for the positions in which it was placed for these experiments. The average dose rate so found was multiplied by the total time during which exposure to the radiation occurred. With some simplification the following relation was developed: gram moles reacted weight fraction ethylene reacted x 106 metric ton x megarep molecular weight of ethylene x dose, megarep

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