ENGINEERING RESEARCH INSTITUTE THE UNIVERSITY OF MICHIGAN ANN ARBOR DSIGN OF A RAILWAY MOBILE GAMMA SOURCE FOR INDUSTRIAL IRRADIATIONS L. E. Brownell S. N. Purohit G. Gyorey D. Harnsberger R. Trevi7 o Project 1943-7 UoS ATOMIC ENERGY COMMISSION CONTRACT NO. AT(11-1)-162 April 1956

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7- ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN - PREFACE This preliminary design of a railway mobile irradiation unit is based on a report by Messrs. G. Gyorey, D. Harnsberger, and R. Trevino submitted as a solution to a student problem in Course 195 in Nuclear Engineering at The University of Michigan. I ii

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - TABLE OF CONTENTS Page PREFACE ii LIST OF FIGURES iv ABSTRACT vi OBJECTIVE vi I. INTRODUCTION 1 A. THE PROCESS OF IRRADIATION 1 B. ADVANTAGE OF A MOBILE GAMMA-IRRADIATION UNIT 2 C. PRELIMINARY DESIGN CONSIDERATIONS FOR A MOBILE UNIT 2 II. THE RADIATION SOURCE AND FIELD 3 A. THE RADIATION SOURCE 3 Bo THE MAPPING OF THE RADIATION FIELD 8 C. ABSORPTION CORRECTION 14 III. SHIELDING 14 A. FOR HIGH-FLUX SOURCE ELEMENTS 14 IV. MECHANICAL DESIGN OF THE FACILITY 25 A. THE RAILROAD CAR 25 B. THE CONVEYOR 28 C. THE SOURCE CONTAINERS 28 D. DESCRIPTION OF OPERATION 29 V. CAPACITY OF THE IRRADIATION UNIT 32 VI. COST ESTIMATES 36 REFERENCES 39 iii

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN LIST OF FIGURES Figure Page 1 MTR fuel assembly. 4 2. Average gamma dose rate of MTR spent fuel elements vs time after shutdown. 6 3. Heat production from spent MTR fuel elements. 7 4. The coordinate system. 8 5. Variation of fi uniform 2-foot6. The spacing of 7. Dose rate vs x 8. Dose rate vs x foot. 9. Dose rate vs x feet. 10. Isodose curves 11. Isodose curves 12. Isodose curves 13. Dose distributi 14. Dose distributi feet. 15. Dose distributi feet..eld *rod the for for strength with distance fFom midpoint of source, normalized to source elements. different values of z different values of z 10' r/hr at 3 feet. for the case y=O. for the case y=l for different values of z for the case y=2 and dose distribution for z=O feet. and dose distribution for z=2 feet. and dose distribution for z=4 feet..ons corrected for absorption and for z=O. ons corrected for absorption and for z=2.ons corrected for absorption and for z=4 9 10 11 12 13 15 16 17 18 19 20 22 23 i 16. Thickness reduction factor for steel shielding (including build-up) of.7-mev gamma radiation. 17. Thickness reduction factor for lead shielding (including build-up) of o7-mev gamma radiation. iv

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN LIST OF FIGURES (Concl.) Figure Page 18. Shielding for railway irradiation facility. 24 19. Cutaway view of railway mobile gamma-irradiation facility shown irradiating citrus fruit. 26 20. Plan, elevation, and end sectional views of railway mobile irradiation facility. 27 21. Details of water-cooled lead shipping container for five spent fuel elements. 30 22. Maximum integral dose corrected for absorption. 33 23. Minimum integral dose corrected for absorption. 34 v

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN ABSTRACT A design has been developed for a railway mobile gamma-irradiation facility. The estimated capacity with 10 MTR fuel elements cooled for 40 days is 10 tons/hr with a 10,000-rep dose. This more than meets the army commitment of "a facility ready to process 1000 tons per month by 1958." This production results from more efficient absorption of gamma photons and use of a simple flexible conveying system. Cost has been minimized by using hot-rolled mild-steel mill plate 2 inches thick for shielding. Shielding thickness is varied from 4 inches to 16 inches by varying the number of plates with the radiation field. The steel shield is used to carry the carload, eliminating the structural undercarriage in the car. Double trucks are attached directly to the steel shield which acts as the car frame. The total car weight is estimated to be 173 tons. Fuel elements are kept in two water-cooled lead pigs weighing about 4 tons each and located on either side of the car. Fuel elements are kept submerged in a shallow 6-inch water trough during use but all irradiation is performed in air. A gear box on the conveyor drive permits variation of conveyor speed to allow delivery of dosages from a few thousand rep to several million rep. Capacity can be increased by using more 40-day-old MTR fuel elements or up to about 100-tons/hr maximum by using fuel elements or cesium sources with greater activity. Plans exist to build this unit and place it into operation within the next two years. OBJECTIVE To present a design of a mobile gamma-irradiation facility feasible at present both from the basis of economics and availability of gamma sources. It is proposed that this preliminary design be completed in detail and that such a facility be constructed and operated as a demonstration unit for industry by 1958. vi

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - I. INTRODUCTION A. THE PROCESS OF IRRADIATION A great number of studies recently completed or now in progress at various laboratories clearly indicate that gamma irradiation can increase the utility or economize the production of a great variety of commodities. It is safe to predict that as nuclear reactors in the United States increase in number, the process of gamma irradiation will become an integral part of the industry of the United States. On the basis of research performed to date it would appear that the impact of this new process of gamma irradiation may be greatest on the food industry. In order to present the advantages that can be derived from the irradiation of foods, a short review is presented here of the results of research performed in this field at the Fission Products Laboratory of the Engineering Research Institute at The University of Michigan. The process in which food is subjected to such doses of gamma radiation which do not completely sterilize, that is, do not destroy all the microorganisms found in the food, is referred to as radiopasteurization.12 A high radiopasteurization dose of about one million roentgen equivalents physical (1 megarep) given to seafood, meats, and vegetables extends their storage life at room temperature several fold, and their unfrozen, refrigerated storage life to long periods of time.3,4 Medium radiopasteurization in the neighborhood of 100,000 rep still reduces the population of microorganisms in foods by over 90% and extends refrigerator shelf-life appreciably.5'6y7 A process that is very promising, and which might be the first approved by the Food and Drug Administration, is a subradiopasteurization dose of about 10,000 to 20,000 rep. A dose of this magnitude will not destroy a sufficient fraction of microorganisms found in fresh foods to affect appreciably the storage life. However, such a dose will inhibit sprouting in potatoes and onions.8'910,11 It will sterilize insects infesting grain and cereal products, and will sterilize eggs and larvae of the Mexican fruit fly in fruit from infested areas of the United States (such as certain areas of Texas), thereby preventing spread of the infestation.* Also, such a dose *Shown by present studies at the Fission Products Laboratory. 1

I - ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN will, through reproductive sterilization, break the cycle of trichinosis in pork and similarly control tapeworm in beef, pork, and fish, and a number of other diseases caused by parasites.14,15,16s17,18 At present, several types of food, such as certain tropical fruits, are banned as U.S. imports because of possible insect infestation. This ban could be lifted for foods given subradiopasteurizing doses which would render them free of contamination. A design is presented for a gamma-irradiation unit which is capable of handling the irradiation of a wide variety of products at any desired dosage, and which is particularly well suited to subradiopasteurization of foods. B. ADVANTAGE OF A MOBILE GAMMA-IRRADIATION UNIT The types of products best suited to subradiopasteurization are very often those that are produced in crops of a seasonal nature. In addition to this, the harvest seasons occur at different times of the year in different parts of the country; therefore, the problem is geographic as well as seasonal. A mobile facility is thus an ideal means of providing for irradiation treatment of crops at the location where they are to be stored immediately after harvest. In this manner the entire crop of one locality can be treated and the mobile unit then moved to some other part of the country for treatment of another harvest crop, thus keeping it in more or less continuous use, resulting in a lower operating cost per unit of product irradiated. At times when harvests are slack, a mobile unit is again advantageous in that it can be taken to a seaport or border city and used for the irradiation of imported foods that would otherwise be restricted by quarantine. A mobile unit would also be of a very great public-service value as a general device for demonstration of the advantages of irradiation treatment of foods. C. PRELIMINARY DESIGN CONSIDERATIONS FOR A MOBILE UNIT A brief review of cost considerations indicates that high-capacity facilities will, in general, give lower unit costs for subradiopasteurization methods because shielding and source costs do not increase in proportion to capacity requirement. As high capacity and low unit cost are considered to be of prime importance in a prototype unit, highway transportation is not considered desirable due to weight limitationsO River transportation is not considered desirable due to geographical limitations. As rail-mounted vehicles have reasonably high allowable weights, and rail lines extend to J L - - 2

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN nearly all parts of the country where storage and processing facilities are located, a railroad car is considered to be the best means of transporting a mobile irradiation unit, Deciding on a rail-mounted unit imposes three interdependent limitations that will determine the ultimate capacity; namely, (1) maximum weight allowance (limits the maximum amount of shielding that can be carried and, consequently, the maximum source strength), (2) outside dimensions of the car (determines volume inside of shielding usable for irradiation), and (3) conveyor speed (must be slow enough to allow easy loading and unloading). Thus the design must include a combination of shielding configuration, source strength, and conveyor size which is consistent with weight, size, and conveyor speed limitations. The radiation field and conveyor arrangement should be such that a uniform field will exist at right angles to the direction of conveyor travel, in order that all material passing through the conveyor system will receive a very nearly equal dose of radiation. This will also require that the conveyor pass on both sides of the source, so that all layers of absorber will be irradiated as uniformly as possible. II. THE RADIATION SOURCE AND FIELD A. THE RADIATION SOURCE On the basis of the preliminary considerations described in the previous section, the source selected for this irradiation unit consists of ten separate source elements, Each of these elements is of uniform crosssection and of two-foot equivalent length enclosed in a suitable metallic jacket. The fuel element proposed to be used is the MTR fuel element as shown in Fig. 1. This figure is from a report by Francis and Marsden.ls A detailed description including fabrication methods for the MTR fuel element was given by J. E. Cunningham and E. J. Boyle at the Geneva Conference.20 This information was summarized in the "Catalog of Nuclear Reactors" by AECL21 and this summary is quoted as follows: "Because of the large number of reactors employing this type of fuel element a description of its general features is given here. For details of the variations encountered, see the particular reactor (MTR, LITR, BSF, CP-5, BORAX I and II, Convair, and GCR were known to be thus equipped in August, 1955. Others in this class but not yet operating at that time were: Pennsylvania State University, Michigan Memorial-Phoenix, Oak Ridge Research, Battelle Memorial Institute, Brookhaven Medical Research Facility, Livermore, I 3

I ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - Fig. 1. MTR fuel assembly. Watertown Arsenal, U.S. Naval Research Laboratory, and others in the planning stage. "Each fuel element is assembled from a number of long thin plates (usually 18 or 19) measuring 24 in. in length, 3 in. in width, and about 0.06 in. in thickness. An end-on view of the plate shows that its transverse section is curved on a 5.5-in. radius to give it the shape of a shallow trough with a width slightly less than 3 in. "An appropriate number of these plates are brazed into parallel grooves in thick aluminum side-plates, giving each element the configuration of a venetian blind with approximately O.l-in. spacing between adjacent slats (plates). Cooling water flows longitudinally through the element in these spaces, and in some versions, a "comb" is inserted down the centre of the element parallel to the side plates to give extra rigidity. "The assembled element is therefore 3 in. wide x 3.17 in. deep x about 3 to 4 ft long. The extra length is due to end fittings which plug into the reactor lattice grid and which provide a means for handling. "Individual plates consist of a uranium-aluminum core, clad in wrought 72-S aluminum by hot-rolling to achieve a good metallurgical bond. The 4

L. - ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN active core is about 2.5 in. wide and 0.02 in. thick, and the total thickness of the "sandwich" is 0.05 to 0.06 in. (The two outermost plates of each element are sometimes given thicker cladding to yield a total thickness of 0,065 in.) Cores containing highly-enriched U235 (greater than 90%) are prepared by alloying 10 to 20 weight % of uranium with high-purity aluminum. Cores containing 20%-enriched uranium require a total uranium content of 50 to 60% and are prepared using powder-metallurgy techniques with U02; these cores are slightly thicker than 0.02 in. Total U235 per element may be from 140 to 200 gm; i.e. 8 to 14 gm per plate, "It is said that MTR-type fuel elements containing five plates are available from Oak Ridge for $120 each." When the fuel elements are first removed from the reactor they have a very high gamma activity. However, they decay at a rapid rate when first removed, losing about half their initial activity before two days of cooling. After three weeks of cooling, their activity has decreased by a factor of approximately 10. Figure 2 shows this decay as a plot of the average gamma dose rate vs time after shutdown. This figure also is taken from the report by Francis and Marsden.19 In selecting a fuel element as a radiation source some compromise must be made between radiation intensity and the average half-life. If a very young fuel element is selected, it will have a high activity but will decay so rapidly as to make it difficult to maintain a sufficiently uniform radiation field for any appreciable length of time. Another problem exists in the heat removal from the spent fuel elements both during shipping and during use as radiation sources. The heat from spent MTR fuel elements is shown in Fig. 3 (also from report by Francis and Marsden19) As a compromise, fuel elements having an average age of 40 days after reactor shutdown were selected. Referring to Fig. 2, it is estimated that such fuel elements would have an average activity of 4.9 x 105 r/hr measured through water at a distance of three inches. It is hoped that the procedure of using identical fuel elements in various configurations and numbers to make up the different radiation sources required by different irradiation processes will become widespread, so that the wide variety of radiation-source needs of industry will be satisfied by just a few types of efficiently mass-produced spent fuel elements or radioisotppe sources having the same dimensions.. i 5

107r Qr w LJ 0_ c) Z z w LLJ 0 wI Q: U) 0 0 < 14 m Z z m m I1 m 7Q -r z — 4 rm 0 m -n I z 10 DECAY TIME AFTER SHUTDOWN-DAYS Fig. 2. Average gamma dose rate of MTR spent fuel elements vs time after shutdown. I

mU)UUU o — CALCULATED 1,000, CORRECTED FOR ESCAPE GAMMAS -1; M EA SU RED Iw 100 10 I I I I I I I I I I I I I I I I I I I I I 1 I 1.0 10 100 1000 DECAY TIME AFTER SHUTDOWN -- DAYS Fig. 3. Heat production from spent MTR fuel elements. m z z Z m m 731 m -I m n z I -H -( 0 n C0 J

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN BT THE MAPPING OF THE RADIATION FIELD For purposes of reference a coordinate system as shown in Fig. 4 was established In order to facilitate the calculation, the variation of the field strength with distance fwirom the midpoint of one element was calculated, using the following relationship: Z-Z2 I = k Z-Z1 dz x2 + (y-y1)2 + z2 or k I - x2 + (y-yl)2 tan-l Z + (-1 (Z-Z2) tan-1 _ z +~~- ( - i (1) where (x,y,z) are the coordinates of the field point, dose rate I is to be determined, and (o,yl,zl) and (oyl,z2) are the coordinates of the end points of the source element. The curve between dose rate vs distance from the source element is shown in Fig. 5. This curve was normalized to 4.9 x 105 r/hr at a distance of three inches through water, so as to correspond with the experimental dose rate for MTR fuel element cooled for 40 days as reported by Francis and Marsden.19 The value of k using the above normalization dose rate is equal to 4.6 x 104. X Y _ _ _ __ —' - Z i 0000 0 00000 Fig. 4. The coordinate system. 8

-I -- - m Z e ____ IIII1____m 6 m m 70 3C d=OT05'= 5 C rn Fig. 5. Variation of field strength with distane from midpoint Z of uniform 2-foot-rod source, normalized to r/hr at feet. 40 \ (T 104) 0 3 --- 30-,,, Kx~~~ \\ d=OTO 12" m 2 --—: 10 -- s 0 3 6 9 1250 INCHES-I —Im d=5'T09' o I 2 3 4 5? 5 6 7 8 9 =! d = DISTANCE FROM MIDPOINT OF ONE FUEL ELEMENT, IN FEET Fig. 5- Variation of field strength with distane from midpoint Z of uniform 2-foot-rod source, normalized to 10 r/hr at 3 feet. I I I

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN The field strength at any point was calculated by summing the contributions due to ten elements, neglecting self-absorption. Elements had been arranged in a group of five separated by an optimum distance. This optimum spacing had been obtained by trial-and-error method so as to produce a fairly uniform dose along the y-axis. Final spacing is shown in Fig. 6. Although it might be possible to replace the group of five elements by a single element with a still higher activity, this is not considered desirable as the source elements can be used much more economically by replacing them in pairs, one in each group, when needed. In the case of replacement, a pair of elements with stronger activity can be installed to make up for the depleted activity of other elements. Z,2" 22" 12 1 -6 I -6II 2. 2" 2" 2' -Y Fig. 6. The spacing of the source elements. In order to obtain the isodose curves and dose distribution throughout the conveyor at different points, the following curves were prepared: Dose rate vs x for Dose rate vs x for Dose rate vs x for different values of z for the case y=O (Fig. 7). different values of z for the case y=l foot (Fig. 8). different values of z for the case y=2 feet (Fig. 9). 10

Il - ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN I -i 200 iAn \ 0 FEET to 0 x C LJ Li ir O0 0 EQ 100 \Z=2 FEET - 51,-. I Z=4 FEET Z=6 FEET Z=8FEET n --- —----------------------- 2 3 4 x, FEET (HEIGHT ABOVE CENTER LINE OF SOURCE) Fig, 7. Dose rate vs x for different values of z for the case y=O. 11

I -- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - 400 - 300 ------- ro 200 - 200 Q w \ Z=0 FEET 0 Q I 1.0 2.0 3.0 x, FEET( HEIGHT ABOVE CENTER LINE OF SOURCE) Fig. 8. Dose rate vs x for different values of z for the case y=l foot. 12

l ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN - ____Li__i____ I I I O x li tw LI a: CL ~B 300 200 Z 0 FEET 100 Z100 ------— z = 4 FEET Z2 = 6 FEET-_ Z =8 FE l[ I I I I I ---I-III-IIII ---- --- ------ l v0 1.0 2.0 3.0 x,FEET ( HEIGHT ABOVE CENTER LINE OF SOURCE) 4.0 Fig. 9. Dose rate vs x for different values of z for the case y=2 feet. 13

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN These curves were utilized to obtain the isodose curves in (x-y) vertical plane for different values of z and the dose-rate distribution throughout the conveyor as shown in Figs. 10, 11, and 12. Dose distribution and isodose curves obtained in Figs. 10, 11, and 12 indicate the nonuniformity of dose. Inside the two conveyor paths shown by the two rectangles points of maximum and minimum dose distribution exist. For small distances from the fuel elements the isodose curves exhibit a dip in dose rate. The dip becomes sharper as the source elements are approached. For the case of the isodose curves with the dip, the minimum value occurs at y=O, and the maximum value is at y=l.5 feet. Away from the source, the isodose curves indicate a fairly uniform dose distribution along the y-axis. C. ABSORPTION CORRECTION The dose-rate distributions shown in Figs. 10, 11, and 12 were corrected for absorption by material inside the conveyor. It was assumed that the conveyor trays are filled with 10 inches of material and that this thickness attenuates the gamma rays by 50%. This is an average of experimental values obtained for the bulk potatoes and similar foods10. The absorption coefficient using this half-value thickness can be termed as broad-beam coefficient; it includes the correction due to build-up factor arising from the multiple scattering inside the material. 0.693 T1/ 1/2 o0693 x 6 feet-1 5 = 0.832 feet-1.. Dose-rate distributions corrected for absorption are shown in Figs. 13, 14, and 15. III. SHIELDING A. FOR HIGH-FLUX SOURCE ELEMENTS (I = 104 r/hr at 3'0") The first consideration in the design of the shielding was an appropriate choice between steel and lead. In this case steel can be shown to be more economical for the shielding of the irradiation chamber whereas 14

L.- ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 5.0 40X103r/hr C.) 48 52 53 52 48 U, 0 60X Ilerl 0 "65 '66 65 60 0 60 z 3.0 w w.,?78?'- -.Z78e Lt 6 0 XlO3r/ hr 1' > 102 106 00 06 102 1 / ',oo, 5",b, o ' W \O \qt 156 54 154 156 W / / 260 234 __177 __234 260_ LL x~ y, FEET (DISTANCE FROM CENTER LINE OF CAR) Fig. 10. Isodose curves and dose distribution for z=O feet. 15

L -- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - 4.0 i:,~ 40 43 43 43 4340 On 48 51 51 51 48 o 3.0 w Z / 56 61 61 56 z w3.. I 1. 96 102 96 102 96; 1.0 \ -V - 3.0 2.0 1.0 0 1.0 2.0 y, FEET (DISTANCE FROM CENTER LINE OF CAR) i Fig. 11. Isodose curves and dose distribution for z=2 feet. 16

1. -- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - 5.0 4.0 ------ -— i --- —- i --- —-- -- i -- 26 26 27 26e 26 w/ iLj -__ i 0 j129 I630s 29\ cr 2' u0 / 32 35 34 33 3.2 z fQ f / 35 36 37? 36 35 W 2.0........ CD 37 3 —7 z ^0 42 44 42 40 ' o -/ -~:, ki I Fig. 12. Isodose curves and dose distribution for z=4 feet. 17

1 -- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 1 w 3 3.0 0 3O C,) Lit 0 w -J z I w W 02.0 w 0 o z C] 1.0 w w LL x I x 103 r/hr. 9.0 9.5 6.5 9.5 9.0 * 01 * 17.5 18.5 15.6 18.5 175 35.3 36.6 33.8 36.6 35.3 45.4 46.2 40.3 46.2 45.4 105.4 101.5 75.2 101.5 105.4 260 234 177 234 260, I i-! Ki I I i 3 2 1 0 1 2 y, FEET (DISTANCE FROM CENTER LINE OF CAR) 3 Fig. 13. Dose distributions corrected for absorption and for z=O. 18

I - ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - 4.0 1 T W tL 0 U. 0 w 3.0 z ILL z w 0 W 0 2.0 w U z 0) W LL 1.0 X X 103r/hr 4.15 4.3 4.3 4.3 4.15 10.6 *11.2 I 11.2 ~11.2 10.64 19.05 20.8 21. 1 20.8 19.05 20.3 22.2 22.8 22.2 20.3 40.2 44.5 44 44.5 40.2 96 102 96 102 96 I I 3.0 2.0 1.0 0 1.0 y, FEET (DISTANCE FROM CENTER LINE OF CAR) 2.0 3.0 Fig. 14. Dose distributions corrected for absorption and for z=2 feet. 19

I - ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 4C0. w 0 Ci) Iw Li w 0 LJ z O i Q 5 LlO x 3.0 2.0 x 103r/hr. 1.8 1.8 1.9 1.8 1.8 3.85 3.85 4.0 3.85 3.85 6.1 6.25 6.4 6.25 6.1 6.1 6.3 6.5 6.3 6.1 12.6 12.9 14.3 12.9 12.6 40 42 44 42 40 l l l --- —------— l ----l --- —l --- —l 1.0. 6 - 3.0 2.0 1.0 0 1.0 y, FEET (DISTANCE FROM CENTER LINE OF CAR) 2.0 3.0 Fig. 15. Dose distributions corrected for absorption and for z=4 feet. 20

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN lead was chosen for the source shipping containers in order to minimize their size. The chamber thus is constructed of layers of two-inch hot-rolled run-of-the-mill plate steel which, in addition to being readily available and easy to fabricate, can have a high salvage value at the termination of the life of the facilityo In the shielding calculations consideration is given to the secondary effects of gamma radiationo Compton scattering is considered to be the major attenuating processo. The intensity of gamma radiation is given by the following relationship: -Tox I = IoBe where B is the dose build-up factor, 0IQ is the total linear absorption coefficient for 007-mev gamma rays, and x is thickness of the shielding that is necessary to reduce the ratio of I/Io to an acceptable value. Plots of I/Io for steel and lead are shown in Figso 16 and 17 for 0.7-mev gamma rays. These plots include the build-up factor correction0 For steel Io was taken as 0.55 cm-1 and for lead lo2 cm- 1 In the design of the shield, use is made of the fact that near the corners of the irradiation chamber the gamma rays enter the walls at an angle much less than 90 degrees and pass through more than the perpendicular thickness of the shieldO If a source emitting high-energy rays of more than 0,7 mev is selected, the total activity of the radiation source should be less for the shield design given, since it was designed for 0,7 mev. When the unit is in operation, the maximum dose rate immediately at the outside surface of the chamber is calculated to be 15 mr/hr, and the dose rate at a distance of 15 feet from the car is less than 1 mr/hr for the shield design showno Extra-heavy shielding is provided to reduce the radiation level at the loading area to an estimated value of 1 mr/hr for the safety of the personnel, The maximum dose rate outside the car when the unit is in transit and the same elements are retracted into their lead containers is 1 mr/hro The outside dimensions of the shielded chambers are 25' x 9 x 10' high, and the weight of the shield, for the design using high-flux source elements, is 160 tonso The detailed drawing and dimensions of the shield are shown on Fig. 18o Note on Shielding Dimensions The shielding dimensions shown in Fig. 18 are for 10 rod sources having 10 times the activity of 10 MTR fuel elements 40 days old. A thickness of two inches should be subtracted from all the dimensions for steel r 21

I -- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - 0i-O, 0 -4 - - Q -.~ ~ 8 LIu D N I II 12 13 THICKNESS OF STEEL (INCHES) Fig. 16. Thickness reduction factor for steel shielding (including build-up)of.7-mev gamma radiation. 22

-- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - 10 i7 %0 ~o cr 0 IO LL 0 le w ~ = I 6 7 THICKNESS OF LEAD (INCHES) Fig. 17. Thickness reduction factor for lead shielding (including build-up) of.7-mev gamma radiation. 25

m z r --- c m 25' 7, A G) 9_ m I1'1 e 4"~4C" — ~ HORIZONTAL SECTION < | |___^gC' AT SOURCE LEVEL to'q ~~ 12" ~~~~ 16 - ~~7~~~~ ~Z ----— C-40" —f~~, 1 —5 8" 16 I SECTION A-A' SECTION C-C' Fig. 18. Shielding for railway irradiation facility (see preceding note). I

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN shields and a thickness of one inch from the lead shields. With these corrections the following shield weights were calculated for the case of 40-day-old MTR fuel elements. Weight of steel shield 155 tons Weight of two lead casks 8 tons Weight of car trucks and accessories 10 tons Total 173 tons IV. MECHANICAL DESIGN OF THE FACILITY A. THE RAILROAD CAR The weight and dimensional limitations involved are of primary interest in the design of a mobile facility. Investigation of standard heavy-duty railway flat cars indicates that a type such as the New York Central-Delaware and Hudson 250-ton car having a cast-steel underframe is the largest in general use.22 The "light" (unloaded) weight of this car is 50 tons. It is mounted on four four-wheel trucks to keep rail loading within tolerance. As a fabricated plate-steel shield for this facility is designed to act also as the main structural member, the weight of the cast-steel underframe is saved, resulting in a maximum allowable weight limit of approximately 275 tons. The total weight of the facility as designed for use with the 40-day-old source elements is 173 tons, giving a loading factor of only 63%, thus margin is provided for increased shielding if more intense radiation fields inside or lower radiation fields outside are desired for the irradiation chambero The exterior dimensions of the railroad car were chosen to be identical with those of a standard 50-foot box car: length 50$ 6", body height 10' 6" (15' maximum over rail), width 9' 0". The taper of the shielding is directed inward on the sides to provide a smooth exterior surface and to allow access space for conveyor maintenance in the interior. The shield taper is directed outward on the top and bottom to provide straight paths for the conveyor rails and to gain a slight chamber-height advantage by being able to "belly" the lower surface down between the two sets of trucks. The center of gravity of the radiation chamber is located midway between the truck center lines to equalize wheel loadings. A cutaway perspective view of the proposed unit is shown in Fig. 19 and elevation, plan, and end sectional views are shown in Fig. 20. 25

--- m ~~~~~4~~~r m m C)b m m I ~~~ ~ ~ rn~~~~ -g m Z era _z m:: ~::_o:;r::;'i~i:;::-:~i'WO l::: 0 -n I Fig. 19. Cutaway view of railway mobile gamma-irradiation Z faciity shown irradiating citrus fruit. 'M x ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ r:i:::::~i e -~,:ii'- na ~'- -: ~ Fig. 19.Cutwayv e ofraiwaymoble amm-iraditio faclit sownirrditin ciru frit J

I C ' INSP DOOR 1 I V INSP DOOR A ~ \ N|\ U E5.Xx$';;.'~.,-z.-.. —S#. l _ a~~~~~~~~~~~~~~~~~~~~~~ E~~~~ LOADING tO O ~DORS i~ S~~~~~~~~~~~~~~ u.~. -~. C m z z m m z m I -I m m 70 n -4 v z SECTION B-B w F — z -n 0 z1 z SECTION a-A Fig. 20. Plan, elevation, and end sectional views of railway mobile irradiation facility. SECTION C-C I

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - B. THE CONVEYOR The preliminary considerations in the design of a tray conveyor for an irradiation facility are: (1) a tray size suitable for the type of product to be irradiated, (2) minimum tray spacing for maximum use of radiation field, (3) minimum handling required for loading and unloading especially for a high-capacity facility where the cost of such labor would be appreciable. As a general-purpose facility is considered, a tray size of 4' x 2t x i' high is chosen as it will conveniently handle the following products: 1. loose items, such as grain, vegetables, and fruits, 2. bags of material, such as potatoes, onions, fruits, 5. bulk items, such as slabs of meat, and 4. boxed or canned items, such as packaged meat or other food products. The trays are made of sheet 24S aluminum alloy and are supported by arms having a pivot point 18 inches above the center of gravity of the loaded tray, thus providing stability in transit and ease of unloading after transit by means of simple dump runners (see Fig. 20). Each tray is carried by roller-bearing wheels running in "U" beam tracks, adjacent trays being connected by link rods supported by additional idler wheels. Drive is by means of a variable-speed electric motor through a gear train or belts to the link rods. Power for the drive can be supplied by a d-c generator driven by a gasoline motor. This packaged unit would be located at the front of the car outside the shield, Using a minimum turning radius of the conveyor track of 12 inches, the tray spacing can be reduced to 4 inches, thereby making maximum use of the available radiation field. Placing two supplementary belt-type conveyors at the loading end of the car (either built in or extended into the car from the adjacent plant or storage building) allows completely automatic loading and unloading of the materials being handled, provided the feeds are synchronized. The slope of the dump runners is matched to the track slope so that the trays are tilted and then returned to the horizontal position in a smooth path, with no free oscillations to disturb the loading operation. A free traveling belt is provided on the runner surfaces to eliminate rubbing friction on the trays. The loading operation is such that an empty tray is always immediately below the one being loaded, thereby minimizing spillage of loose materials such as grain. C. THE SOURCE CONTAINERS In order to effect a maximum saving of weight, the source containers 28

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN are placed at points in the side walls of the car where maximum shielding thickness would ordinarily be required (see Figs. 19 and 20). This location also gives the minimum possible distance required for withdrawal of the sources from their respective containerso As explained in the section on radiation-field calculations, two close groupings of five rods each give the most efficient field pattern in this case, therefore two separate source containers are desirable for handling purposes. As the containers are compact and weigh about three tons each, they can be placed in position readily by suitable fork-lift trucks or an overhead crane. The containers are held in the wall by lugs bolted to the steel shield wall. The exterior surfaces of the containers are "stepped" to match corresponding steps in the shielding wall and prevent leakage of radiation while the facility is in operation. After the containers are placed in the side walls of the chamber, a lifting screw is attached to each door which is operated by a hand wheel on top of the car to provide for opening and closing the container doors. Details of the shipping containers are shown in Fig. 21. Ample space is provided inside the car for access to the source containers and for general maintenance of the conveyor system. While outside of the containers, the sources are supported in lightweight external "U" section tracks in a trough which also acts as the support for the tank of water used for cooling fuel elements. The lower edges of the container doors are notched to allow for the internal rails for support of the source assembly. If reactor fuel elements are used as the source elements, the elements may be cooled by circulating cool water through the lead source containers during shipping and through the trough in the radiation chamber during radiation processing. Since changing of source elements may be required, if spent reactor fuel elements are used, it would be desirable to provide two extra source containers for shipment and reloading while the other set is in use. Thus, maximum use of the facility could be made at all times. Do DESCRIPTION OF OPERATION To operate the facility the sources of radiation must first be installed. If spent MTR fuel elements are used, the shipping containers are first sent to the reactor site and five elements are loaded under water into each shipping containero The shipping containers are water-cooled and are supplied with a reserve tank of make-up water to replace that lost by evaporation during shipment to the mobile facility. Referring to Fig. 20, the shipping containers "U" are loaded into shield Q. Water pump "'Y ' pumps cooled water from sump "X" tq cool the fuel elements. Handwheel "W" and crank "Z" are then connected to provide the mechanism to raise the source doors and to move the source elements out of the shipping container, respectively. 29

- — l W _ P~ mr d x$/"]] '.IL P t O s 0 _ _ _.________ f j=W SECTION TA-A DRA t ~CD \ WATER EXIT, FOR CLOSED POSITION.^^^OO^^VFg 21MetTO STORA-' ---o — -ldi ---n 1 Fig. 21. Details of water-cooled lead shipping container for r l i6 T oo TO STOCZAOE~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 TANK LyTR Na ELEHFRTS~~~~~~~~~ L=~~~~~~~L 8~P-fr Fig. "' Dtails of ater-coold lead shyping conainer fo m z m z m m IA I — I m S m 0 z m -< 0 m n m 3Z CI >r Zr five spent fuel elements, I

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Details of this operation can be described by referring to Fig. 21. Handwheel "W" is located on the roof of the car. In transit this wheel will be kept locked with the source enclosed in the shipping container. Handwheel "W" turns shaft "a" which rides in bearing "b" sitting in shield "Qo' The motion is transferred by coupling "c" to screw "e" which lifts lead door "g" by means of nut "f." The load of the lead door is carried by bearing "d,'" Prior to raising lead door "g," a trough "r" is bolted to each shipping container with a gasket joint to be water tight. Pipe "p" is attached and brings cold water from a sump to cool the fuel elements. Water flows through the shipping container by loop "h" when the door is closed and directly through the door opening when the door is raised to overflow "o" and then returns to storage where it is cooled. After the water circulating system is operating and the source doors have been raised by handwheel "W," crank "Z" is attached to the side of the car to withdraw the sources from the shipping containers. Crank "Z" turns screw "j" inside tubular nut "k" which moves bar "1" toward the center of the caro Bar "l" is attached to two square rods "m" which serve as tracks for the assembly of five fuel elements. These tracks ride in groove 'n,t On shutting down the facility in preparation for travel to another location, the reverse procedure is used; the sources are drawn back into the shipping container and the shipping-container doors are lowered and locked, Details of the conveyor operation can be described by referring to Fig. 20. When the car is on location and cooling water is pumped from sump "X" by pump ttY, the source doors are raised by handwheels "W" and sources "S" withdrawn from lead containers "V" by means of crank "U," making the facility operative. Material to be irradiated is brought in via conveyor "A" from an adjacent warehouse, processing plant, or grain elevator and is fed into buckets at point "B.o" The conveyor in the car carries the material from point "B" past and over shield "C," under shield "D" over shield "E" into radiation zone "F.' After traveling the length of the upper pass "F," a turn is made about sprocket "G" and a lower pass "H" is made directly over sources "S.' -A turn is made around sprocket "I" and two identical passes "J" and "L" are made below the source passing around sprocket "Ko' Thus the material is first irradiated from the underside of the buckets in two passes and then from the top side of the buckets in two identical passes to equalize the dosage on top and bottom of the conveyor buckets. The material leaves the radiation zone, passing under shield "E," over shield "M" and under shield '"C" traveling up incline "N" where a guide cam tilts the bucket and empties it at point "O2o' Conveyor "P" returns the irradiated material to the warehouse, processing plant, or grain elevator. 31

1 ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN V. CAPACITY OF THE IRRADIATION UNIT In order to calculate the capacity of the irradiation unit, the dose received by the material being irradiated as it passes through the conveyor system must be determined. Total dose received is obtained by the numerical integration of the integral dose curve, which is obtained by plotting the distance traveled against the dose rate. It is desirable to know maximum integral dose so as to limit overdosage and possible off-flavors in irradiated foods and minimum integral dose so as to assure the completion of the purpose of irradiation such as the destruction of insects. Therefore, maximum and minimum integral dose curves were prepared as shown in Figs. 22 and 25 and the areas under the curve have been determined by the numerical integration. (a) Minimum Integral Dose.-The minimum integral dose curve was drawn by plotting the dose received by a point on y=0 on the central line of the tray. Since the conveyor makes two passes, outer and inner, on each side of the source, the integral dose determined for a travel of 40 feet (half the total distance) is multiplied by a factor of two. Minimum integral dose = 1.07 x 106 rep-ft hr (b) Maximum Integral Dose. —The maximum integral dose curve was drawn by plotting the dose received by a point on y=2 feet and situated at x=2.7 feet (outer pass) and x=l.3 feet (inner pass) while passing on one side of the source and at x=2.3 feet (inner pass) and x=5.2 feet (outer pass) while passing on the other side of the source against the distance traveled. Total distance traveled is 80 feet. Maximum integral dose = 1.8 x 106 repft hr (c) Capacity Calculation. —For calculating capacity, the average integral dose should be used (checking the minimum dosage so as to assure no underirradiation). Average integral dose = 1.435 x 106 rep-ft hr Conveyor speed for 20,000-rep dose = 1.435 x 106 rep-ft 2.0 x 104 rep hr 71.8 ft/hr i 32

7 INNER PASS y =2 Ft |- 1.3Ft. / m z C) m m r C) 70 m m 70 I -- m S I'1' t r e0 or 0 150 100 i INTEGRAL DOSE I=D(Z)dZ I0 8 [=1.8 x 106 rep fe hr I 50 - OUTER PASS - y=2 Ft. x =2.7Ft. i~~~~~~~~~~~~~~~~~~~~~~~~~~~~ L = y- c r. t: o INNER PASS r., o F, z m 0 -I, 8 0 80 o Z OUTER PASS y= 2 Ft. x=3.2 Ft 0 10 20 30 40 Z,TRAVEL IN FEET — 50 60 70 Fig. 22. Maximum integral dose corrected for absorption. I J I

I 7C 5C UJ:.4C bLJ 0)C 0 0 3C ) | (INNER PASS) yr=O x = 1.8 Ft. 40 I=2 (Z)dZ o I= 1.07 x 106 repfeet x=3.2 Ft. -- ROUTER PASS )~\___ m Z m Z z m m 50 z 0 73 m I m -n z 70:3: m Z 7 --< O Cn 3:,n C~ Z^ 2C IC 0 10.0 20.0 Z, TRAVEL IN FEET-_ 30.0 40.0 Figo 23. Minimum integral dose corrected for absorption.

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Volume of material on 1 ft of conveyor = 3 cu ft Capacity in bushels per hr = 2.41 bu x 71.8 ft ft hr = 175 bu/hr Weight of material on 1 ft of conveyor = 150 lb Capacity in tons per hr = 150 x 71.8 tons = 5.4 tons 2000 hr hr Capacity for 20,000-rep dose l= 5o4 tons/hr For operation of 16 hours per day for an average of 5 days per week, that is, 4160 hours per year, the yearly output of the unit is 175 bu x 4160 hr = 730,000 bu/yr hr yr Table I gives the capacity of the unit for different irradiation doses using MTR fuel elements cooled for different periods of times TABLE I CAPACITY IN TONS PER HOUR i No. Cooling R/H'r Capacity Tons/Hr for Different Doses Period x 105 10,000 Rep 20,000 Rep j 50,000 Rep | 100,000 Rep 1 20 days 10.0 22.02 11.01 4.4 2 2 2 40 days 4,9 10 8 5.4 26 1.08 3 60 days 350 6.62 3531 1.32 0.66 4 70 days 2.5 5.5 2.75 1.1 0.55 5 80 days 2.1 4.63 2.32 0o93 o.46

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN VIo COST ESTIMATES An attempt is made to be as realistic as possible concerning the probable construction and operating costs of this facility; however, the cost of rental or purchase of a source of the size required is an elusive figure and a considerable part of the total estimated operating cost must be recognized to be contingent on this rather uncertain estimate. The following assumptions are made in the cost estimates: 1. Source rental, or depreciation if purchased: $250 per month per elemento 2. Desired capital recovery period of three years at 8% interest. 3. Salvage value of the steel and lead shielding will be estimated at 50% of the original cost of materials0 4. Operating time will be 16 hours per day, an average of 5 days per week, that is, 4160 hours per year0 TABLE II ORIGINAL COST OF THE FACILITY The original cost of the facility is estimated as follows: 1. Steel shielding, 160 tons at $120 (material only) $19,200 2. Lead containers and miscellaneous shielding, 8 tons at $400 (material only) 3,200 35 Railway cars (trucks and outer frame only) 10,000 4. Conveyor system, including 46 trays 8,000 5. Motors, instruments 6,000 60 Source mechanism and cooling system 10,000 7. Engineering 5,000 8. Construction 32,000 Total $93,400 36

I - ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN The annual operating cost, including capital recovery, of the facility is estimated as follows: TABLE III ANNUAL OPERATING COST 1. Source rental: $250 x 12 x 10 $ 30,000 2. Operating personnel 20,000 3. Maintenance and plant overhead (10% of investment, excluding source) 4. Taxes and insurance (10% of investment) 5. Replacement of source elements (every 2 months at reactor site) 6. Capital recovery and interest (10,000-14,500) x.3880 + 14,500 x.08 Total 10,000 10,000 10,000 34,300 $114,300 The hrs (260 days cost of irradiation per ton is calculated using 4160 operating at 16 hrs/day) and a dose of 20,000 rep: 5.4 tons x 4,160 hr hr year i = 22,500 tons year Cost per ton = 114,300 dollars 22,500 tons = $5.10 per ton. It is quite probable that doses other than 20,000 rep will be desired as discussed in the introduction, or that fewer or more hours of operation per year will be possible. Table 4 summarizes the cost per ton of the product under a few operating conditions. 57

-- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN TABLE IV SUMMARY OF UNIT RADIATION COSTS Cost (Dollars/Ton) Dose (Rep) Capacity (Tons/Hr) for 4D160 Hr/Yr 10,000 10.8 2.55 20,000 5.4 5.1 50,000 2.16 10.2 100,000 1.08 20.4 200,000 0.54 40.8 i 38

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - I REFERENCES 1. Brownell, Lo Eo, Graikoski, Jo T., and Kempe, L. Lo, "Gamma Rays; The Hope of Researchers to Lengthen Refrigerated Life of Fresh Foods," Refrigerating Engineering, 63:42-47 (1955)o 20 Brownell, Lo Eo, Nehemias, Jo V0, and Purohit, S. No, "Gamma-Irradiation Facilities Designed to Process Commercial Quantities of Food Products," Proceedings AAAS, Atlanta, Gao, December, 1955o 30 Brownell, Lo E., and Purohit, So No, High Radiopasteurization as a "New" Food Process, Engineering Research Institute Project M943, The University of Michigan, Ann Arbor, 1955o 4. Brownell, Lo Eo, and Purohit, S. N., "High Radiopasteurization as a 'New' Food Process Combining Gamma Radiation and Refrigeration," Refrigerating Engineering, in presso 5. Brownell, Lo Eo, Nehemias, J. Vo, and Bulmer, JO J., "Proposed New Method of Wholesaling Fresh Meat Based on Pasteurization by Gamma Irradiation," The Industrial Atom (TID 8001), Atomic Energy Commission, Washington, Do C., 1955o 6. Brownell, Lo Eo, Nehemias, J. Vo, and Bulmer, J. Jo, "Proposed New Method of Wholesaling Fresh Meat Based on Pasteurization by Gamma Irradiation," Proceedings, 1955 Conference on Nuclear Engineering, University of California, Los Angeles, 1955, ppo D-68-92o 7. Brownell, Lo Eo, et al., "Proposed New Method of Wholesaling Fresh Meat," in:Utilization of the Gross Fission Products1 Engineering Research Institute Project M943, C00196, Progress Report 7, The University of Michigan, Ann Arbor, March, 1954, ppo 119-166. 80 Brownell, Lo E., and Nehemias, Jo Vo, "Atomic Energy and the Potato," National Potato Council News, 1:4-5 (1955)o 9. Brownell, Lo E,, Nehemias, Jo V., and Bulmer, Jo Jo, "Designs for GammaIrradiation Facilities for Potatoes," in:Utilization of the Gross Fission Products, Engineering Research Institute Project M943, C00196, Progress Report 7, The University of Michigan, Ann Arbor, March, 1954, ppo 120-500 i 39

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - 10o Brownell, L. E., Nehemias, Jo V., and Bulmer, Jo J., The Design of a Gamma-Irradiation Facility for the Control of Insect Infestation in Flour, Meal, or Grain, Engineering Research Institute Project M943, The University of Michigan, Ann Arbor, 1955. 11. Brownell, L. E., Nehemias, Jo V., and Bulmer, Jo J., Operation of the Fission Products Laboratory, Engineering Research Institute Project M943, Quarterly Progress Report 2, The University of Michigan, Ann Arbor, 1955o 12. Baker, V. H,, Taboada, 0., and Wiant, Do Eo, "Lethal Effect of Electrons on Insects Which Infest Wheat Flour and Beans - Part I," Agricultural Engineering, 34:755-58 (1953). 135 Baker, V. H., Taboada, 0o, and Wiant, D. E. "Lethal Effect of Electrons on Insects Which Infest Wheat Flour and Beans - Part II," Agricultural Engineering, 35:407-10 (1954). 14. Gomberg, Ho J., Brownell, Lo E., Nehemias, J. V., and Coleman, Eo, "The Design of an Irradiation Chamber for a Pork-Processing Plant," in: Utilization of the Gross Fission Products, Engineering Research Institute Project M943, Progress Report 5, The University of Michigan, Ann Arbor, 1953, ppo 85-110o.15o Gomberg, Ho J., Gould, S. E., Nehemias, J. Vo, and Brownell, L. E., "Breaking the Cycle of Trichinosis by Gamma Irradiation," in: Utilization of the Gross Fission Products, Engineering Research Institute Project M943, Progress Report 5, The University of Michigan, Ann Arbor, 1953, pp. 69-84. 16. Gomberg, Ho Jo, Gould, So Eo, Nehemias, J. Vo, and Brownell, L. E., "Design Fission Irradiator to Break Trichinosis Cycle," Food Engineering, 26:78 (1954). 17. Gomberg, Ho J., Gould, S. E., Nehemias, Jo Vo, and Brownell, Lo E., "Design of a Pork-Irradiation Facility Using Gamma Rays to Break the Trichinosis Cycle," Nuclear Engineering - Part III, 50:89-104, Chemical Engineering Progress Symposium Series, American Institute of Chemical Engineers, New York, 1954o 18. Gomberg, H. J., Gould, S. E., Nehemias, J. V., and Brownell, L. Eo "Using Co-60 and Fission Products in Pork-Irradiation Experiments," Nucleonics, 12:38-42 (1954)o 19. Francis, W. Co, and Marsden, Lo L., "Experimental and Theoretical Values of the Gamma Decay Dose Rate and Heating from Spent MTR Fuel Elements," IDO-16247, January 15, 1956o 40

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 20. Cunningham, Jo E., and Boyle, Eo Jo, "MTR Type Fuel Elements" Geneva Conf. Paper No. 953, 1955. 21. AECL "Catalog of Nuclear Reactors," CRR-590, Chalk River, Ontario, AECL No. 220, August, 1955. 22. The Official Railway Equipment Register The Railway Equipment and Publo Co., 1951. 41

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