UNI V E R S I T Y OF M I C H I G A N Department of Chemistry PROGRESS REPORT 4 November 1954 - October 1955 NUCLEAR CHEMICAL RESEARCH and RADIOCHEMIC AL SEPARATIONS W. W. Meinke, Project Director November 1, 1955 Project No. 7 Contract No. AT(11-1)-70 U. S. ATOMIC ENERGY COMMISSION

Project No. 7, Contract No. AT(ll-1)-70 between the University of Michigan and the U. S. Atomic Energy Commission was initiated on February 1, 1952. On November 1, 1952, Progress Report #1 was submitted to the Atomic Energy Commission. Progress Report #2 was submitted on November 1, 1953 and Progress Report #3 was submitted on November 1, 1954. The following is a report of the work which has been completed on the project during the year of November 1, 1954 to October 31, 1955. ii

TABLE OF CONTENTS PAGE I FACILITIES ~ ~ ~ ~ ~ ~ ~ ~ ~...... 1 Michigan Phoenix Memorial Laboratory... 1 Michigan Reactor...........* 4 Chemistry Building.................... 7 II INSTRUMENTATION (Including Calibration).. 8 Metal Evaporator.......... 8 Bombardment Chamber and Current Integrator. 9 X-ray Proportional Counter.......15 4 Pi Counters............. 18 Gamma-ray Spectrometer and Coincidence Apparatus................ 20 Scintillation Detectors......... 23 Calibration and Standard Samples.... 24 Lens Type Beta-ray Spectrometer..... 25 III EXPERIMENTAL................26 Nuclear Chemistry............. 26 Determination of (d,alpha) Cross Sections...............26 Systematics of (d,alpha) Reaction Yields and Possible Closed Shell Effects... 28 Excitation Functions for Charged Particle Reactions....... 31 Literature (Also see microfilm supplement C - Excitation Functions and Cross Sections)......... 31 Experimental............ 33 Decay Scheme Studies.......... 33 Iridium-196.............. 33 Other Nuclides............. 34 iii

TABLE OF CONTENTS (cont'd) PAGE Thin Films............... 35 Thickness Measurement......... 35 Nickel Films.............. 36 Chemical Procedures.............. 38 Sodium (Hall)......... *..40 Phosphorus (Hall)............ 42 Scandium (Hall)............... 44 Scandium (Gardner).............46 Manganese (Anders).............49 Silver (Hall),................ 51 Silver (Sunderman)......... 53 Barium (Sunderman)............ 55 Iridium (Gardner)............. 57 Radiochemical Separations.. 59 Alkaline Earth Separations (Also see Supplement A).............. 59 Yield of the Desired Constituent..... 60 Contamination by Other Activities... 60 Silver Exchange Separation (Also see Supplement B)...............63 Yield of Radioactive Silver,....... 64 Contamination by Other Activities...... 64 Interferences..............,. 67 Beta-ray Sources.............. 67 General Utilization of Isotopic Exchange,..69 General Silver Separations..........69 Methods Evaluated............. 69 Yield of Silver and Contamination By Other Activities............ 70 iv

TABLE OF CONTENTS (cont 'd) PAGE Literature Search and Punch. Card Compilation (Also see Supplement DRadiochemical Procedures)....... 72 IV PERSONNEL, PUBLICATIONS, TALKS.....74 Personnel Listing............* 74 Papers and Reports Published...... 75 On Project Work —..(Nov. 1954-Nov. 1955).75 On Other Work Related to Project — (Nov. 1954-Nov. 1955).... ~ * ~ * 76 Talks.....*... X.. *. *. X 77 V ACKNOWLEDGEMENT............. 79 VI LIST OF REFERENCES..........& 80

LIST OF FIGURES FIGURE NO, PAGE Michigan Phoenix Memorial Laboratory 1. Front view.......... 2 2. Rear view —reactor construction....... 2 3. Floor olan.............. 2 High Level Caves 4. Rear view.,.......... ~.. 3 5. Front view...,.......... 3 Glove Box Room 6. Glove box and manifold,.......... 5 7. Walk-in hood...... 5 Hot Chemistry Laboratory 8. Floor plan,................. 6 9. View of hoods............... 6 10. Side chamber assembly for metal evaporator..10 11. Schematic layout of cyclotron vacuum system. 12 12. Calibration schematic for current integrator 14 13. Apparatus for filling x-ray counter with krypton................... 16 14. Discrimination curves of NBS P-32.....19 15. Film absorption curve of sodium...... 21 16. Film absorption curve of scandium..... 22 17. Decay curve of sodium separated from magnesium............... 29 18. Transmission of Ni-63 radiation....... 37

I FACILITIES The past year has seen a great expansion of the facilities available to the project. A. Michigan Phoenix Memorial Laborato The new $1.2 million Michigan Phoenix Memorial Laboratory for resaerch with radioactivity was dedicated in June 1955 and the hot laboratory facilities opened for use during the late summer. The design of the hot laboratory has been described in a paper presented before the Fourth Annual Symposium on Hot Laboratories and Equipment in Washington and scheduled for publication (1) in the November 1955 issue of Nucleonics. The hot laboratory was designed to handle kilocurie and multicurie levels of activity as well as subcurie levels. Pictures of the completed building including greenhouse are shown in Figures 1 and 2 while the layout for the first floor area including the hot lab is given in Figure 3. Figures 4 and 5 show front and rear views of the two high-level radiation caves. One cave will be connected with the Michigan reactor by a pass through from the reactor pool. The other cave will be used for high-level chemical experiments and experiments using the underwater storage pit. The caves were designed to handle ten kilocuries of cobalt-60 equivalent gamma radiation and are very similar to the Argonne Metallurgy caves. They have three-foot thick walls of high density concrete and lead glass windows.

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3 Fig 4 Fig. 5. HIGH LEVEL CAVES Fig. 4. Rear view. Fig. 5. Front view.

For multicurie work a glove box and Junior cave area is available. This room is partially encircled by a manifold furnishing facilities such as exhaust, water, gas, vacuum, air, "cold" drain, and electricity. Glove boxes, as shown in Figure 6, or lead shielded Junior caves will be available for work with up to 5 curies of 1 Mev ganmna-ray emitter. Also in the middle of the room is a large walk in hood, shown in Figure 7, for use in vacuum line experiments and syntheses of compounds of high specific activity, such as C-14 compounds. A variety of hoods and glove boxes are available in the hot chemical laboratory for use with activity below the curie level. These are shown in Figures 8 and 9. Pneumatic tube terminals from the reactor will be located in each of three of these chemistry hoods. This location of the tube terminals will minimize active particulate (or gas) problems and permit "fast" chemistry on irradiated targets. B. MichiSan Reactor Construction on the Michigan Research Reactor which adJoins the Phoenix Building is proceding according to schedule. The partially completed first floor for the reactor is shown in Figure 2. It should be in operation by late spring according to current estimates. The reactor is a "swimming pool" type that will operate initially at 100 kilowatt but has been designed for 1 megawatt full power.

Figx 6,. ig. 7. ( GLOVE BOX ROOM Pig. 6 Gl ove box and manifold F~g, 7. Walk in hoodo:::: ~~~~~~~~~~~~8~~~g~~~~gpl[~~~~~~~~~:~~~~~~gg~~~~~p ~~ ~ ~.......

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C. Chemistry BuildinE The facilities in the spectrometer room in the Chemistry Building have been expanded by the removal of a cinder block wall to allow better coordination of the individual spectrometer units and to reduce crowding. In addition the project director has moved into a new small office and relinquished his previous space for a service area for files, photocopying and thin film preparation.

II INSTRUMENTATION (Including Calibration) The major items of specialized counting equipment available to the project have been kept in operation throughout the past year although a number of electronic repairs have been necessary. These units include the survey betaray spectrometer, the gamma-ray scintillation spectrometer and the coincidence counting equipment. Major modifications and improvements in other equipment are described below. A. Metal Evap ora The metal evaporator pictured and described in the previous progress report (2) has been used extensively during the past year. Thin films of cadmium, aluminum, gold, magnesium, manganese, nickel and calcium have been produced with a fair degree of success while it has proven very difficult to get any deposit at all of palladium or zirconium with the present set-up. Experimental techniques in producing the aluminum, manganese and cadmium films are reported in the project report by K. L. Hall (3). Several determinations have been made of the evenness of deposit on the 21-inch diameter films. Films of evaporated magnesium were cut into eight roughly equal rectangular pieces and their thickness in milligrams per square centimeter (metal plus substrate) was determined by weighing with a microbalance and measuring with a low power calibrated magnifier. It was found that the evenness of the evaporated films had a standard deviation of between 0.4 and 1.0%.

Construction and testing of the small side chamber for the metal evaporator has been completed. Considerable difficulties were met in making the chamber leak tight but recent experiments have proven that thin, even metal films can be easily deposited on 0.0004 inch mylar films, 3/8 inches in diameter, with this attachment. A diagram of the side chamber assembly is shown in Figure 10. Relatively large collection efficiencies can be obtained in this chamber because of its small dimensions and the directional design of the heating elements employed. Post experimental cleaning and decontamination when radioactive materials are evaporated were found to be considerably less difficult when all interior parts of the chamber except for the element and the target are covered with a thin layer of silicone high vacuum stop cock grease. (K. L. Hall and 0. Anders) B. Bombardment Chamber and Current Integrator The new bombardment chamber built in 1954 and described earlier (2) has proven very satisfactory and has been used by K. L. Hall in about 20 bombardments for the determination of absolute cross section data on the (d,alpha) reaction. A schematic drawing of the cyclotron layout showing the bombardment chamber "Q" in relation to the rest of the cyclotron equipment is given in Figure 11. Description of this equipment and shop drawings of the bombardment chamber are available in Mr. Hall's report (3).

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11 The current integrator used in the above bombardments has not been completely satisfactory. Circuits of this integrator and a number of comments regarding problems involved in its operation are given by Hall (3). Considerable time has been spent during the past year trying to correct the difficulties encountered with this integrator. Reasonable linearity of this instrument could be obtained only for currents below 0.8 microamperes and counting rates of the instrument below 9 counts per minute. These limitations restricted the cross section experiments to bombardments at low currents and long bombardment time. The Michigan cyclotron can now deliver several microamperes at the bombardment chamber and hence a new integrator was constructed to accomodate these higher beams. This new integrator was based upon a design obtained from S. Rankowitz of Brookhaven National Laboratory and had ranges from 0.01 microamperes to 100 microamperes full scale. Construction of this instrument was begun in July 1955 and considerable help in wiring and fabrication was obtained from the cyclotron group of the Physics Department. Several minor changes in the wiring were made and the construction has finally been completed. Vacuum sealed precision resistors obtained from the Victoreen Company were used for the critical standard reSistors in the design. The input stage as well as the integrating condensers and Raytheon CK5886 electrometer tubes were enclosed in two hermetically sealed metal boxes which are desiccated by a silica gel cartridge obtained

12 CYCLOTRON LAYOUT - SCHEMATIC yt w ~~~~~~V Y, ~ ~~ #, --- —- T SR A CYCLOTRON TANK R B WINDOW BOX _ --- — P C PROBE PORT 0 D SLITS L E 6 INCH PIPE NM L F FOCUSING MAGNET G 6 INCH CHANNEL H VACUUM PUMP INTAKE I 41INCH PIPE J SLITS H K 2 INCH PIPE G L SLITS \ F M SCATTERING CHAMBER N SCATTERING TARGET O MONITOR P 2 INCH PIPE Q BOMBARDMENT CHAMBER R TARGET S SUPPRESSOR RING T FARADAY CUP / E U VACUUM PUMP INTAKE V 6 INCH PIPE W SLITS D X ANALYZING MAGNET Y SLITS \C Z EXIT CHANNELB Fig. 11. Schematic layout of cyclotron vacuum system.

13 from the Atomic Instrument Company. When the desiccant is exhausted a pink color appears and the cartridge can be regenerated in an oven. The method that will be used for calibration of the new integrator is shown in Figure 12. A 10,000 ohm NBS standardized resistor was used with a Rubicon type B potentiometer and a Leeds and Northrup type R galvanometer and permitted measurement of currents as low as 0.01 microamperes to be determined with an error of 1%. In order to minimize the loss of secondary electrons from the Faraday cup of the bombardment chamber a suppressor ring that could be charged to -1000 volt was installed between target and cup to prevent the escape of these secondary electrons. The difference in charge collection in the cup with and without a negative voltage on the suppressor ring was found to be considerable (~ 20%). The effect increases rapidly up to 200 volts and levels off around -1000 volts. It was thus decided to charge the ring to -1000 volts with respect to the Faraday cup during the bombardments. Originally a voltage supply going up to -2000 volts was constructed with drycell batteries for this purpose. During the humid days of the past summer a short circuit developed and destroyed all the batteries in the supply. In order to avoid any further such accident a negative high-voltage power supply going up to 1600 volts was constructed. Provisions were made so that this power supply could be modified to a 2500 volts negative supply, by

14 STANDA RD POTENTIOM ETER STORAGE CELL BATTERY HI - MEG. STANDARD.F A A H.V. RESISTANCE FARADAYURRNTCU POWER Box RESITRC~ SUPPLY INTEGRATOR Fig. 12. Calibration schematic for current integrator.

15 changing the transformer to a Haldorson P 1931 A if need arises for different application. (K. L. Hall and 0. Anders) C. X-ray Proportonal Counter The x-ray proportional counter mentioned previously (2) has been completely rebuilt with small changes to the previous design. The old counter was too fragile and it seemed impossible to make the apparatus leaktight, The alterations of design were thus mainly of a mechanical nature to insure greater rigidity and fewer possibilities for, leaks to develop. The counter was tested and operated with fillings of one and two atmospheres of 90% argon and 10% methane; and 95% argon and 5% methane mixtures. With a commercial linear amplifier and scalar, plateaus of 350 volts and a slope of 0.5 per cent per 100 volts were obtained with the 9 key x-rays from Zn-65 samples. The counter was then filled with 2 atmospheres 90% krypton and 10% methane gas mixture for high efficiency counting of x-rays up to 30 kev. A special manometer and mercury pumping arrangement was built for this purpose and is shown in Figure 13. The counter with a krypton filling would not work with the standard equipment available. For a number of absolute cross section determinations it will be necessary to count "absolutely" the weak x-rays emitted from deuteron reaction products decaying by electron capture in the presence of relatively high gamma backgrounds. For this purpose it was decided that a good non-overloading amplifier and a high-precision 5000 volt power-supply along

Split pipe as support 150cc i r _ Kr Fig. 13. Apparatus for filling x-ray counter with krypton.

17 with part of the gamma-ray spectrometer must be used with the 4 inch proportional counter. For the amplifier a double delay-line design by Francis and Bell (4) of Oak Ridge National Laboratories was chosen as apparently best fulfilling the requirements. One comnercial supplier agreed to custom build it and a delivery date was agreed on in early March, 1955. Delivery could not be made, however, even by the end of July, apparently due to difficulties with the layout. The contract was cancelled and instead a commercially advertized Chase-Higinbotham nonoverloading linear amplifier and 5000 volt power supply was ordered from the Radiation Instrument Dompany, Silver Spring, Maryland. Both amplifier and high voltage power supply were delivered recently and are being checked. A preamplifier for the x-ray proportional counter was designed and built in this laboratory. This preamplifier furnishes a low-impedance input for the RIC non-overloading amplifier and is essentially a cathode follower stage employing a high-/ triode (6J4). It is expected that the x-ray counting equipment will be useful for x-ray spectroscopy in addition to its primary function of "absolute" x-ray counting. It is hoped that the equipment will be in operation early in November. (0. Anders)

D. 4P i Counters The two 4 pi counters assembled previously (2) were tested extensively during the past 12 months and satisfactory results obtained (see Hall (3)). The decay of several samples of In-116 were followed in the Borkowski counter for 13 half lives from counting rates as high as 106 c/m to below background and a dead time of about 7.9 micro seconds (corresponding to about 0.013% / 1000 C/m) determined for the counter. A solution of P-32 standardized by the National Bureau of Standards to within ~ 2% was checked by counting in our 4 pi counters. Aliquots were taken with pipettes previously calibrated with mercury. The values obtained were well within the error limit given by the Bureau. Discrimination curves, a primary test for the performance of a 4 pi counter, were taken and plateaus with negligible slopes were obtained over several discriminator settings. A typical curve of this type is given in Figure 14. Voltage plateaus with no slope over a 600 volt range were obtained with Sr-Y-90 and Co-60. These voltage plateaus were taken with samples having conducting gold-layers over the source and with samples supported by non-conducting Zapon film stretched over the ~-inch central hole of the counting plates. No difference in plateau lengths or slope were encountered for the various samples. Chi Square tests also substantiated the satisfactory reproducibility of counting rates obtainable with the 4 pi counters.

19 DISCRIMINATION CURVES OF NBS p32 (CYLINDRICAL 4W PROPORTIONAL COUNTER) 33 -+-GAIN 100 3900 VOLTS - GAIN 75 32 -x-x-GAIN 50 31 -A 4000 VOLTS z 32= 0 L3I o32 x 33 I LIMITS OF COUNTING \ 30 ERROR (STANDARD DEVIATION) 10 9 8 7 6 5 4 3 2 1 DISCRIMINATOR SETTING Fig. 14. Discrimination curves of P-32 standardized by the National Bureau of Standards. The limits of the counting error shown are twice the standard deviation of a single point.

20 Thorough studies were carried out by Hall (3) to determine the absorption of beta particles in different thicknesses of sample substrate. Absorption curves proved that no correction due to loss of beta particles in the 2 Zapon layer substrate of the counting samples had to be applied to obtain absolute decay rates for Na-22, while a 1% correction for Sc-46 samples was indicated. Film absorption curves for these two cases are given in Figures 15 and 16. (K. L. Hall and R. Maddock) E. Gamma-ray Spectrometer and Coincidence Apparatus During the past year we have had an inordinate amount of instrument trouble centering around the gamma-ray spectrometer and coincidence apparatus. Such things as fluctuations in resolving times, short term drifts in various units, unreproducible counting rates, and parts failure have caused much loss of time. Many of the difficulties can be traced to the damaging affects of large fluctuations in line voltage. It is hoped that these have been corrected by running all of the electronic units from a new 2000 watt Sorenson Voltage Regulator. A voltmeter has been installed to continuously monitor either the regulated or unregulated line voltage. Further improvements in instrumentation include a new very stable high voltage power supply (Atomic Instruments, Model 312) and a switching arrangement whereby several configurations of the basic gamma and proportional spectrometer units may be obtained without changing cables,

21 FILM ABSORPTION CURVE OF SODIUM (CYLINDRICAL 47 PROPORTIONAL COUNTER) 17500 1.7% Na22 17000 _. 16500 I --- D 1500 L2 22 a_ '20%Na,, 1460 31420 I E 0 310 22 100% Na22 290 I UNCOVERED SAMPLE I 2 3 4 5 6 7 8 9 10 LAYERS OF FILM Fig. 15. Film absorption curve of various mixtures of Na-22 and Na-24. The errors shown are standard deviations due to counting statistics.

22 FILM ABSORPTION CURVE OF SCANDIUM (CYLINDRICAL 47r PROPORTIONAL COUNTER) 380 46 50% Sci 370 1130 kn- i_ 3630 L_ 82 % Sc,220 1 2 345,6789109,10,111213 w 210 03 A 150 150 i451 — I00% Sc"' 135 130 -I 2 3 4 5 6 7 8:9 I0' 11 12 13 EQUIVALENT LAYERS OF FILM FILM THICKNESS (/zg/cm2) FIg. 16 Fil m absorption curve of various mixtures of Sc-44, Sc-46, Sc-47 and Sc-48. The errors shown are standard deviations due to counting statistics.

23 plug-in Jacks, or rewiring. The gray wedge may now be used routinely with the Lande camera for semiquantitative work. - The automatic step-sweep arrangement mentioned in the previous progress report (2) is almost completed. With it beta, gamma, and various coincidence spectra may be examined automatically with a predetermined probable error. The decay of gamma lines or portions of-beta spectra as seen by either a beta-ray scintillator or by the 1800 beta-ray spectrometer as well as spectra from the x-ray proportional counter may also be followed with a; predetermined probable error using the preset counter and time print that are integral parts of the step-sweep arrangement. (D. Gardner and W. Barrett) F. Scintillation Detectors Several new additions to our supply of scintillation type detectors have been made. A stilbene detector l- inch in diameter by l mm thick already mounted was purchased and found to be excellent for beta-gamma coincidence work. Because of the thinness of the crystal,beta spectral shapes and conversion electron peaks of more than a few tenths of an MEV, cannot be examined with any accuracy. Instead, for this work, a cylinder of scintillating plastic 1l inch in diameter by 7 mm thick was cut. from stock, polished, and mounted. This detector will completely stop beta-rays up to - 1.5 MEV, but still distorts the beta-ray spectra.

24 For the determination of spectral shapes and for resolving complex beta spectra a hollow plastic scintillator was made. It is in the form of a right truncated cone with a base 1 inch in diameter, height 3/4 inch, and top ~ inch diameter. A cavity of similar shape was hollowed out of plastic leaving a base 5 mm thick and walls about 3 mm thick. The inside of the crystal was polished as was the outside face of the base. Preliminary experiments showed Kurie plots with the hollow scintillator to be much less distorted than with the flat plastic scintillator, the stilbene scintillators on hand, or the 1800 beta-ray spectrometer. The Ca-45 source that was used unfortunately was much too thick, and so a complete evaluation must be made later when a carrier-free source can be used. Also the effect of the helium atmosphere inside the hollow crystal will be investigated. An x-ray detector composed of a 11 inch diameter by 2 mm thick NaI(Tl) crystal has also been purchased. It will be used primarily in coincidence work, but also for measuring very low energy gamma rays in the presence of other gamma rays. (D. Gardner) G. Calibration and Standard Samples The 1800 beta-ray spectrometeir (2) was recalibrated in February, 1955. It was found that there -had been essentially no drift in the unit in over a year. A redesigned sample chamber is under consideration which would include a gamma detector for coincidence work. Action on this is awaiting

the outcome of the hollow plastic scintillator work. Several new standard samples have been made. Background measurements with the sample chamber between the pole faces, at various field strengths have been made indicating no background variation with field strength. Our original stilbene crystal has been calibrated at various settings of the scintillation spectrometer. The resolution of the Cs-137 conversion peak is ~14% for this crystal. Various standard samples have been made for both beta and gamma samples. A special set of standards with (100/gms/cm2 Zapon backings which may be counted absolutely in our 4 pi proportional counters have been made. These standards include Co-60, Ca-45, Cs-137, Sr-89, Sb-124, Hg-203 and Sn-113 and will be used in branching ratio measurements, with the hollow scintillator, and for other special calibration work with the spectrometers. (D. Gardner) H. Lens Type Beta-ray Spectrometer Some spectra have been run on a lens type beta-ray spectrometer belonging to Professor M. L. Wiedenbeck of the Physics Department. This spectrometer has a resolution of - 6% and was used as a basis for evaluating results from the 1800 beta spectrometer and the hollow scintillator spectrometer. Use of this lens type instrument in conjunction with our decay scheme program has not been found practicable since the instrument normally requires much greater activities than are usually produced by the (d,alpha) reaction in a tyoical cyclotron bombardment. (D. Gardner)

III EXPERIMENTAL Much progress has been made during the past year both on the nuclear chemical and the separation phases of the program. Thirty-two bombardments have been made on the University of Michigan cyclotron, while five have been made at Argonne National Laboratory and one at the Berkeley Radiation Laboratory. The work on determining absolute yields for the (d,alpha) reaction has produced its first "high precision" values in the work of K. L. Hall described below. The experience gained and the equipment set up in these experiments will permit many more cross sections to be determined during the next year. The program of developing optimum radiochemical separations has progressed especially rapidly during the past year as evidenced by the publications on the work already in print or accepted. Detailed manuscripts on two phases of this work have recently been completed and are being submitted for publication, Preprints of these two articles are included as a supplement to this report. A. Nuclea Chemist 1. Determination of (d,alpha) Reaction Cross Sections The objectives of this research were to assemble the necessary apparatus and establish procedures for the accurate measurement of (d,alpha) reaction cross sections, and to apply these techniques to determine several cross sections using the 7.8 Mev deuterons

27 from the University of Michigan cyclotron. The measurement involved the bombardment of thin targets, subsequent chemical separation of the product nuclei, and determination of the absolute disintegration rate of the beta-ray emitting products. To obtain the irradiations a bombardment chamber was designed and installed as an integral part of the cyclotron vacuum system. The deuteron beam was stopped in a Faraday cup, after traversing the target. The beam current was measured by means of a current integrator which was built for this work. A metal evaporator was assembled for use in fabricating thin targets. After bombardment, the targets were dissolved, and the low yield (d,alpha) reaction products were chemically separated from relatively large amounts of (d, n) and (d, p) radioactive products. This was achieved without the addition of inactive carriers in the case of three of the four elements studied. Absolute counting of the separated products was accomplished by application of the techniques of 4 pi proportional counting. The experimental (d,alpha) reaction cross sections for the formation of the isotopes indicated are: Na-22: a = 0.094 + 0.004 barn at 7.8+ 0.1 Mev Na-24: a = 0.151 + 0.006 barn at 7.8+ 0.1 Mev P-32: a = 0.3 + 0.2 barn at 7.7+ 0.1 Mev Sc-46: a = 0. 00044 0.00033 barn at 7.0 0.8 Mev 1.2-hr Ag-104: c = 0.0017 + 0.0002 barn at 7.8+ 0.1 Mev Ag-112: o = 0.00049 + 0.00002 barn at 7.8+ 0.1 Mev Ag-lll: a = 0.0004 + 0.00004 barn at 7.8+ 0.1 Mev

28 The errors quoted are estimated standard deviations. The result for Sc-46 quoted above is an average of two determinations which differed from one another by a factor of four. The half-life of Na-24 was evaluated oy the method of least squares and found to be 14.93~0.04 hours. A graph of this decay is given in Figure 17. Separated isotopes were bombarded to assign the 27-minute and the "1.2-hour" periods in silver to Ag-104. This work is described in detail in the project report by K. L. Hall (3). Several sections of this report are being revised for submission to the Physical Review. (K. L. Hall) 2. Systematics of (dalpha) Reaction Yields and Possible Closed Shell Effects During the past year three (d,alpha) reaction cross section values have been obtained in this laboratory with errors as low as 4%. With most of the equipment in operating condition, it is planned for the coming year to extend this work to a series of other nuclides and to search for a trend in the cross section values of the (d,alpha) reaction. The new x-ray counter described above widens the field of attack to many (d,alpha) reactions producing isotopes which decay by electron capture. Absolute cross section measurements are planned for (d,alpha) reactions on elements such as Zirconium, Germanium, Nickel, Strontium, Yttrium, Iron, Cobalt,

29 DECAY OF SODIUM (CYLINDRICAL 4r PROPORTIONAL COUNTER) N24 4 3 222 D- _.. I I I I I z~ 0 o a~500 1000 1500 24 L9 a-Na22 z00 0 o 00 Na 0 0 20 40 60 80 100 120 140 160 180 200 220 TIME (HOURS) Fig. 17. Decay curve of sodium separated from magnesium resolved into the 2.6-year Ma-22 and 15-hour Na-24 components by the method of least squares.

30 Molybdenum, Niobium, Sulfur and Cadmium. For some of these measurements, the preliminary experiments have already been carried out. The (d,alpha) cross section determinations make absolute counting of beta particles mandatory for good precision. In order to avoid excessive uncertainties as to geometry and loss due to absorption and self absorption, it was decided to do all precision betaray counting with 4 pi counters as described earlier. For all counts thin films a few micrograms per cm2 thick are used as a substrate for essentially weightless radioactive samples. Carrier-free separation techniques have to be used for separation of the weightless amounts of radioactive (d,alpha) reaction product from the macro amounts of target element and target backing. Since a determination of the yield of this chemical separation is essential, tracer techniques using carrier-free tracers or tracers of very high specific activity have to be employed. Some of the carrier-free separations that can be used for this purpose have been worked out in this laboratory during the past year. Among others the carrier-free procedures for separating yttrium from zirconium and niobium; rubidium from strontium and yttrium; manganese from iron and cobalt; niobium from molybdenum and technetium and zirconium from niobium have been developed.

31 Ion exchange resin column techniques permit rather clean..and relatively fast-separation of many of the elements encountered and hence are used extensively in these carrier-free procedures. Thus within the next 12.months a number of (d,alpha) cross section values will be determined to obtain a reasonably good picture of.the:overall trend of the yield of this reaction. In addition it is planned to. investigate several of the so-called magic number nuclides to see if nuclear shell effects become evident in the yields of this reaction as they apparently do for the (p,- n) reaction. (0. Anders) 3. Excitation Functions for Charged Particle Reactions a) Literature -- In preparation for the investigation of the (d,alpha) cross section and excitation function measurements planned in this laboratory, a thorough literature search was carried out. The compilation of excitation functions mentioned in last year's report (2) has been brought up to date (September 1955) and the photocopies pasted on punch cards. These cards have been categorized according to element bombarded, element produced, and also according to bombarding particle, and particle emitted in the nuclear reaction. Charged particle excitation functions (and where possible cross sections) for bombarding energies above 2 Mev have been included in this compilation.

32 The curves included in this compilation have been found for the most part by an intensive search of Nuclear Science Abstract and Chemical Abstracts under many categories having to do with nuclear reactions. A number of progress reports of AEC installations have also been checked. It cannot be claimed, however, that the compilation is absolutely complete. Furthermore most or all of it will be overlapped by the eventual publication of the results of the Los Alamos Cross Section Group under the direction of Dr. Taschek. This compilation remains, however, a fairly complete accumulation of cross section data which is of special interest to the nuclear chemist in estimating how much of certain reaction products will be formed in a particular bombardment. In addition it serves as a basis for our cross section program to tell for what elements good cross section values have been determined and what elements are the most promising to work on. Previously it had been mentioned (2) that an attempt might be made to evaluate each bit of data found in the literature and to graph all data onto the same scale such as Hughes has done for neutron cross section values. We have decided against this additional work because of the work of Taschek's group at Los Alamos and also because of the multiplicity of values and curves coming out of various laboratories in the country at the present time.

33 Instead we will keep the punch card file of graphs up to date as much as possible, will microfilm it once a year and make it available to anyone interested. A copy of the first microfilm of this compilation is included as Supplement C to this Progress Report. (0. Anders and W. Meinke) b) Experimental -- The bombardment chamber of the Michigan cyclotron is designed so that bombardments of stacked foils can be made for excitation function determinations. The bombardment of multiple foils will not be emphasized, however, until a number of good cross section determinations have been made at one specific energy. Undoubtedly a number of excitation functions will have to be determined in connection with the study of the systematics of the (d,alpha) reactions mentioned above so as to eliminate from consideration the effect of the coulomb barrier as the atomic number of the target is increased. (O. Anders) 4 Decay Scheme Studies a) Iridium-196 — Work on the characterization of the isotope Ir-196 has now been completed and will be offered for publication soon. The work has involved three bombardments of platinum metal roils and one bombardment of platinum metal enriched in Pt-198. The results include harlf life determinations and

34 rough excitation functions for the Pt(d,alpha)Ir reaction for three platinum isotopes (198, 196 and 194) in the range from 8 to 22 MEV. Bombardments were obtained on the cyclotron at the Argonne National Laboratory and at Berkeley. The energy of the betaray from Ir-196 has been estimated. Information concerning the number of gamma-rays as well as their energy and abundance and coincidence information has been accumulated. The interpretation of these data for bombardments of the naturally occurring mixture of platinum isotopes is about impossible because of the large number (16 or more) of gamma-ray lines of the long lived Ir-192 which is found in good yield. Only by bombarding platinum enriched in the isotope of mass 198 was it possible to obtain some clear indication of beta and gamma radiations belonging to the 8 day Ir-196. A correlation of these data into a decay scheme is now being attempted. Although there are other interesting points in the decay scheme, such as the possibility of an isomeric state no further work will be attempted with the equipment presently available because of the complexity of the gamma spectrum. (D. Gardner) b) Other Nuclides -- In general, the nuclides chosen for study in our decay scheme program will comply with the following criteria. They will have a short half-life, usually of the order of minutes or at most hours.

35 The natural isotopic abundance of the target nuclide will usually be less than 10%, so that enriched isotopes will be used in at least some of the bombardments. The target nuclide will either be on a closed shell, or else + one nucleon from a closed shell. Practically all of the isotopes will be produced by the (d,alpha) reaction, the others being formed by the (d, n) reaction. Some work has been done on Sc-47, including the development of a carrier free separation for scandium from titanium and vanadium. This work has now been dropped due to recent publications which seem to characterize it rather well. The next isotope to be studied will be V-47, t~ 33m, produced by a (d, n) reaction on Ti-46. Enriched isotopes are now on hand that increase the isotopic abundance of Ti-46 from 8.0% to 82.7%. A fairly rapid, carrier-free separation using an ion exchange column and a "squirt" technique has been developed to separate vanadium from titanium and scandium. This procedure is described in detail in a later section of this report. (D. Gardner) 5. Thin Films a) Thickness Measurement -- Hall has given in his report (3) a detailed description of methods used in this laboratories to determine the thickness of thin plastic films used in 4 pi counting. The Ni-63 beta-ray absorption technique, similar to

36 that described by Pate and Yaffe (5), has been used in most cases. A calibration curve has been constructed for zapon films based on gravimetric determination of film thickness with a microbalance and is shown in Figure 18. A number of careful weighings on the microbalance showed that individual films drawn under standard conditions according to the techniques described previously (2), can be made to the same thickness to within 7 - 8 per cent. This fact allows considerable saving of time since even an 8 per cent difference introduces no appreciable error in the film absorption correction in 4 pi counting (3) when multiple layers of film are used. (This correction is made by extrapolating to zero absorber counts that are taken with several varying amounts of absorber.) An attempt will be made in the future to apply this same type of technique to the determination of thickness of target films prepared by evaporation. Thin collimated sources of Sr-Y-90 beta rays (6) will be used with a Geiger tube and should permit non destructive determination of evenness. (K. L. Hall and 0. Anders) b) Nickel Films -- In the search for methods other than evaporation that could be used for preparation of thin metal films, an electronic cell was set up and some experience gained in plating pure nickel metal on thin (0.005 inch) copper sheet.

1.O0 TRANSMISSION OF Ni`3 RADIATION (LOWER HALF OF CYLINDRICAL 4r PROPORTIONAL COUNTER) o. I) O) zo') - fto REFERRED TO UPPER AXIS q:.8' E ] 0 REFERRED TO LOWER AXIS -. CLL.6 2 3 4 5 6 7 8 LAYERS OF FILM I I I I I I I I I I I I I I 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 FILM THICKNESS (/ug/cm2) Fig. 18. Transmission of Ni-63 beta radiation in thin Zapon films. The upper x-axis gives the number of layers of film and the lower x-axis shows the surface density as determined gravimetrically.

38 After some preliminary experiments even nickel films were deposited from a warm bath containing NiC12, NiSO04, and boric acid. The main difficulty seemed the deposit of anode mud as particles on the nickel plate. This was finally overcome by use of an alundum sieve separating anode and cathode half cells from each other. Another problem was warping of the nickelplated copper foils. Stretching the copper foil in the opposite direction before plating helped overcome this obstacle. To prevent the nickel plating on both sides of the copper sheet a double layer of transparent Glyptal lacquer dried under a 1500 watt infrared heat lamp was applied to one side. The plated copper was cut into circles of target size with a stamp-die, the Glyptal layer removed with acetone and the coper backing dissolved off over night with chromic acid. Good nickel foils 0.001 inch or less thick were thus prepared. Bombardments using these foils are planned for the future. (0. Anders) 6. Chemical Procedures Valuable by-products of the nuclear chemical program on cross sections and decay schemes are the separation procedures developed. Some are not necessarily novel, combining steps already reported in the literature to accomplish the decontaminations required for the specific problem at hand. Others incorporate decided advances

39 in radiochemical techniques in order to satisfy certain conditions of the separations such as speed or high decontamination from one or two elements. All have been written up in the form used by Meinke (7) in his compilation of procedures and follow in this report. Two of the procedures, the silver separation by Sunderman and the indium separation by Gardner have been distributed in a slightly modified form by H. L. Finston in his compilation of Radiochemical Procedures sponsored by the National Research Council (8).

CHEMICAL SEPARATIONS Element separated: Sodium Procedure by: Hall Target Material: Magnesium Time for sep'n: - 8 hours Type of bbdt: 7.8 Mev Equipment required: 250 ml deuterons Phillips beaker, ion exchange column, automatic sample changer, 10OOx15 mm test tubes (Arthur H. Thomas Co., No. 9446) Yield: -50% Degree of purification: -103 Advantages: carrier free separation for 4 pi beta-counting. Procedure: (1) Place 1 ml con HSO4 in 250 ml Phillips beaker and add tracer Na22 ~see remark 2). Introduce the Mg target ( - 20 mg) and Mylar substrate. Heat strongly to decompose the Mylar. (2) Cool, add several drops of 30% H20 and reheat. Repeat until a clear solution is obtained. (3) Fume off excess H2SO and add 10 ml water. Neutralize (to pH ~ 4) by adding an excess high purity Mg. (4) Absorb onto Dowex 50 column (H+ form) at a flow rate of 2.5 sec/drop. Rinse the column with 10 ml of water. (5) Elute with 0.5 N HC1 at 2.5 sec/drop, collecting the eluates in clean 100x15 mm test tubes. Assay in scintillation well counter to determine the elution curVe. (6) Test sodium fractions for Mg+ with quinalizarin spot test (see remark 3). (7) Evaporate the most active fractions to dryness. Take up with water and transfer to 4 pi plates. Remarks: (1) General references: J. Beukenkamp and W. Rieman III, Anal. Chem. 22 582 (50) and V. J. Linnenbom, J. Chem. Phys. X, 1657 (52).

41 (2) The tracer is added for the purpose of determining the chemical yield. (3) Reference for quinalizarin test: Feigl, Qualitative Analysis b Spot Tests, 3rd ed. (New YorkI 467), P. 172 (4) Use conductivity water to make up solutions, etc.

42 CHEMICAL SEPARATIONS Element separated: Phosphrus Procedure by: Hall Target Material: Sulfur Time for sep'n: ~8 hours Type of bbdt: 7.8 Mev Equipment required: 250 ml deuterons Phillips beaker, ion exchange columns, automatic sample changer, 10Ox15 mm test tubes (Arthur H. Thomas Co., No. 9446) Yield: -20% Degree of purification: -103 Advantages: carrier free separation for 4 pi beta-counting. Procedure: (1) Place 2-3 ml- on H2S04 in 250 ml Phillips beaker and add tracer P3 (see remark 2). Introduce the S target ( -70 mrg) and the polystyrene substrate. Add several drops of 30% H202 and heat gently to decompose the polystyrene (see remark 3). (2) Cool and add 25 ml of a 2:3 mixture of Br2-CC1 Let stand 30 minutes to dissolve the sulfur. Add more H2S04-H202 and heat gently to complete the solution. (3) Neutralize to pH- 6.4 with solid Na2CO3 and dilute to 500 ml. (4) Absorb onto Dowex 50 column in Fe(OH) form at a flow rate of 1 sec/drop. Rinse with 50 ml water. (5) Elute with 125 ml 0.125 N NaOH at a flow rate of 1 sec/drop, channellin$ the effluent directly into a Dowex 50 column in H form. Collect the eluates in clean lOOx15 mm test tubes. Assay in a scintillation well counter to determine the elution curve. (6) Test phosphorus fractions for SO4 with Ba. (7) Evaporate the most active fractions to dryness. Take up with water and transfer to 4 pi plates. Remarks: (1) General reference: L. D. McIsaac and A. Voigt, ISC-271, (June 1952).

43 (2) The tracer is added for the purpose of determining the chemical yield. (3) If the H2S04 solution is heated to fumes, some PO4 may be lost. (4) Use conductivity water to make up solutions, etc.

44 CHEMICAL SEPARATIONS Element separated: Scandium Procedure by: Hall Target Material: Titanium Time for sep'n: - 5 hours Type of bbdt: 7.8 Mev Equipment required: 250 ml deuterons Phillips beaker, micro bell Jar, No. 00 Hirsch funnels, Whatman No. 50 filter paper, pHydrion (short range) pH paper Yield ~ 10% Degree of purification: - 102 Advantages: carrier free separation for 4 pi beta-counting. Procedure: (1) Place 1 ml co$6H2S04 in 250 ml Phillips beaker and add tracer Sc (see remark 2). Introduce the Ti target (. 130 mg) and the Mylar substrate. Heat strongly to decompose the Mylar. (2) Cool, add several drops of 30% H202, and reheat. Repeat until a clear solution is obtained above the unattacked Ti. (3) Add 10 ml 18 N H2SO4 containing 5% 16 N HN03. Heat, keeping the HNO3 replenished until the Ti is all dissolved. (4) Dilute to 100 ml and neutralize to pH 8.5 (use pHydrion paper) with a 1:15 mixture of 30% H202 and 8 N NH40H. Add enough excess H202 to keep the Ti in solution. (5) Filter twice through the same Whatman No. 50 filter paper, using suction. Wash three times with 3 N NH4C1 at pH 8.5. (6) Remove Sc with several portions of hot 3 N HC1. (7) Repeat steps 4, 5 and 6 twice, except in final cycle use conductivity water at pH 8.5 to wash the Sc "precipitate" (8) Evaporate to dryness. Destroy organic matter with aqua regia. Take up with water and transfer to 4 pi plates.

45 Remarks: (1) General reference: J. D. Gile, et al., J. Chem. Phys., 18, 1685 (50). (2) The tracer is added for the purpose of determining the chemical yield. (3) Use conductivity water to make up solutions, etc.

46 CHEMICAL SEPARATIONS Element separated: Scandium Procedure by: Gardner Target Material: Titanium Oxide Time for sep'n: - 2 hours Type of bbdt: 7.8 Mev Equipment required: Ion deuterons exchange column of AG 2-X8, 200-400 mesh resin obtained from Bio-Rad Laboratories. Resin bed was 8 mm x 140 mnm. Yield: >60% Degree of purification: >106 from V; >105 from Ti Advantages: carrier free separation with high decontamination Procedure: (1) Prepare column by washing several times with conc. HC1, then with conc. HC1+ KC103 (see remark 1). (2) Place TiO2 in a small porcelain crucible and add roughly 1-2 gms K2S207 per 100 mgs of TiO2. Cover and bring to dull red heat, Continue heating until TiO2 dissolves in flux (10-15 min) (see remark 2). (3) Cool below 2000C. and cautiously add 1-2 ml of conc. H2S04. (4) Heat until all solids dissolve in the H2S04. Upon cooling, contents of crucible should remain liquid. If solidification occurs, add more conc. H2S04 and repeat heating. (5) Pour li.quid into a beaker using a small amount of H20 as a wash. (6) Add solid NaOH until solution is basic to litmus and TiO2 precipitates out as a white hydrous oxide. Stir thoroughly for a few minutes to insure that all Sc will be carried down on the TiO2 (see remark 3). (7) Centrifuge out the TiO2 and salt. (Most of the V activity remains in the supernate). (8) Wash the TiO02 and salt several times with 1 N NaOH until all of the salt has dissolved (see remark 4). (9) Dissolve TiO2 in a few drops of conc. HC1 and reprecipitate with saturated Na2C03 solution. (Much of the Sc goes into the supernate in this step.)

47 (10) Remove supernate and repeat step 9 twice more, saving the supernatents at each step and combining them in the end (see remark 5). (11) Total supernate is acidified with conc. HC1 and evaporated down to less than 20 ml. Solution is then cooled in an ice bath and saturated with HC1 gas. (Saturation is assumed complete when no more salt comes out of solution.) Centrifuge and discard salt. (12) Continue evaporation almost to dryness. Extract residue with 5 ml of~ 11 M HC1 three times. Evaporate HC1 solution to 5-10 ml, add -5 mgs of KC103, cool in ice, and saturate with HC1 gas. Centrifuge to remove any salt and then place on column prepared in step 1. (13) Force solution through column at rate of - 1-2 drops/ sec., stopping Just before liquid reaches top of resin. (Do not allow top of resin to ever become dry.) Some Sc will appear after first 5 ml. Elute with 11 M HC1 + KC103 at rate of 1-2 drops/sec. (see remark 1) (14) Most of Sc comes off in first 10-15 mls of 11 M HC1. Ti begins to come off after 25-30 mls of 11 M HC1. (see remark 6) (15) A very small amount of salt may follow the Sc. This may be removed by evaporating eluent containing the Sc down to 5-10 ml, saturating it with HC1 gas, and then running it through the column - washed with Just conc. HC1 - at a much slower rate. The salt comes off first. Remarks: (1) All HC1 + KCLO3 solutions contain just enough KC10$ to impart a faint yellow color to the solution. Usually this was < 5m KC103. (2) K2S207 was made by heating K2S208 until S03 fumes ceased to evolve. (3) Some water may be added along with the solid NaOH, bit the volume of solution should be kept small, usually 20 ml or less. (4) All of the washings in step 8 will usually contain much less than 10% of the total Sc activity.

48 (5) Of the total Sc activity in the TiO2 precipitate over 60% is removed in the first reprecipitation and over 20% is removed in the second. (6) The eluent (including original solution) is usually taken in separate units of 3-5 ml. Aliquots of these are counted to give the Sc and Ti peaks, then the center 60-70% of Sc peak is taken for analysis. (7) General Reference for this type procedure: Hicks,H. G., et al., "The Qualitative Anionic Behavior of a Number of Metals with an Ion Exchange Resin, 'Dowex 2'"' Livermore Research Laboratory Report, LRL-65, Dec. 1953.

49 CHEMICAL SEPARATIONS Element separated: ManUanese Procedure by: Anders Target Material: Iron Time for sep'n: 2 hours Type of bbdt: 21 Mev deuterons Equipment required: 125 ml phillips beaker, HC1 gas tank Dowex II (200-400 mesh), two 8 cm x 0.4 cm columns, test tubes Yield:. 50% Degree of purification: 103 Advantages: carrier free separation for 4 pi beta-counting. Procedure: (1) Dissolve iron target in warm con. HC1 containing tracer. (2) Evaporate to about 2 ml in a small Phillips beaker and saturate with HC1 gas. (3) Transfer quantitatively to an 8 cm long, 0.4 cm diameter Dowex II (200-400 mesh) column. (4) Elute Mn with 12 ml con HC1. (5) Evaporate eluate to about 1 ml. (6) Transfer quantitatively to a second column with as little HC1 as needed (1 ml). (7) Elute Mn with 12 ml 9 M HC1. Use conductivity water to prepare the diluted HC1. Co has an elution minimum at 9 M HC1. (8) Concentrate eluate and plate for counting. Remarks: (1) This procedure was used for the preparation of carrier free Mn tracer. The target consisted of a 10 mil Fe foil soldered to a copper backing plate. Preliminary steps employing continous extraction of iron with isopropyl-ether in the dark and subsequent coprecipitation of Mn with added iron carrier were used to reduce the bulk of the iron. (2) The large amount of Co-57 produced in high yield by the (d,n) reaction on iron was also separated carrier

50 free. A Dowex II column of somewhat larger dimensions than given above was employed, to ensure good separation of cobalt. (3) General Literature reference: H. G. Hicks, et al., "The Qualitative Anionic Behavior of a Number of Metals with an Ion Exchange Resin, Dowex 2", Livermore Research Laboratory Report LRL-65, Dec. 1953.

51 CHEMICAL SEPARATIONS Element separated: Silver Procedure by: Hall Target Material: Cadmium Time for sep'n: 15 min Type of bbdt: 7.8 Mev Equipment required: Barber deuterons filter tubes and suction bulbs (Wilkens-Anderson Co., cat. no. 8480B and 1686), water bath, micro bell Jar, filtration apparatus (Tracer Lab, Boston, Mass.), test tubes, beakers, etc. Yield: - 70% Degree of purification: 104 Advantages: Rapid separation Procedure: (1) Place 1 ml con HNO3 in+100 ml high form beaker containing 20 mg or Ag and 10 mg each of T1+, Pd+, Bi+++, Cu n++,, Ga++ In+++carriers. Introduce the Cd target ( ' 50 mg) and dissolve. (2) Dilute ca fourfold with hot water, add 2 drops 0.1% aeresol solution and 5 drops 1 N HC1. (3) Adjust (Cl-) to 0.0025 N and digest 1 min. (4) Filter through glass wool using filter tube and micro bell Jar. Wash twice with hot 0.1 N HN03. (5) Dissolve precipitate off of filter by recycling 4 drops of 6 N NH40H, catching the solution in a 5 inch test tube. (6) Add 2,5 mg Fe+++, filter and wash the precipitate twice with 6 N NH40H. (7) To the filtrate from (6) add 3 mg each of the original carriers, substituting Cd++for Ag+. (8) Add HN03 and 2 drops 1 N NH4C1 to precipitate AgCl and recycle if desired. (9) Filter the final AgC1 precipitate on a 1 inch diameter filter paper using the filtration apparatus, wash with 0.1 N HN03, acetone, and ether.

Remarks: General references: W. W. Meinke, Chemical Procedures Used in Bombardment Work at Berkeley, AECD-2738(UCRL-432) (August 1949 ).

53 CHEMICAL SEPARATIONS Element separated: Silver Procedure by: Sunderman Target Material: Fission Time for sep'n: 15 min or less products or palladium Type of bbdt: Equipment required: Platinum gauze electrode ~" X xtl in cylindrical form, 50 mesh gauze. Magnetic stirrer. Source of variable voltage direct current Yield: > 99% Degree of purification: 103 to 106 depending on elements present Advantages: fast, high-decontamination, quantitative yield. Procedure: (1) Electroplate 10 mg metallic silver on a platinum gauze cathode from 10 ml of a 3 M_ NaCN solution, 0.5 M in NaOH. Stir magnetically. (2) Wash Ag surface with water for 15 seconds and emerse in 0.05 M HC1, connect platinum gauze as anode and electrolyze at about 1 v. for 5-10 minutes or until surface of silver is gray. (3) Wash AgC1l surface with water for 15 seconds. (4) Contact AgCl gauze with solution containing tracer silver in 10 ml vol. for 15 minutes. Stir magnetically. (5) Remove gauze and wash with stream of 8 M HNO3 from wash bottle for one full minute. (6) May count gauze if relative value is desired or dissolve AgCl in NHq and plate sample of solution or acidify NH3 soluti n with HN03, centrifuge, plate and count AC1. Remarks: (1) A smooth even Ag film is desirable on gauze so good stirring should be employed. (2) If the solution containing the tracer is not more than 0.1 M HC1 or 4 M HNO the yield will be over 99% in 15 minutes. For mure rapid, non-quantitative work 5 minutes contact will remove about 97% at room temperature. At 95~ about 2 minutes contact will

54 remove 98% of the tracer. The mechanism of removal is isotopic exchange. (3) The time required for the complete procedure is about 30 minutes. (4) The decontamination factor for separations in nitric acid solution from alkali metals, alkaline earth and rare earth activities is greater than 100 in one step. For platinum group, transition metals and other forming chloride complexes the DF is only about 10 in C1- sol. However in chloride free solutions the DF is greater than 10. (5) An inexpensive battery eliminator (Model BE-4) available from Heath Company, Benton Harbor, Michigan is used as a source of direct current. (6) See also AECU-2988, Science 121, 777 (1955) and succeeding papers.

CHEMIC AL SEPARATIONS Element separated: Barium Procedure by: Sunderman Target Material: misc. activities Time for seo'n: 1 hour Type of bbdt: Equipment required: International clinical centrifuge., 15 ml borosilicate glass centrifuge tubes. Platinum stirring wires. Plates or glass tubes for counting. Analytical balance for determination of yield. Yield: ~50% Degree of purification: 102 to 109 depending upon elements present Advantages: High decontamination Procedure: (1) Add carriers to 15 ml cone, secure isotopic exchange. (2) Pot. BaC1 2H20 from 3 ml aq vol by addition of 10 ml 4:1'HC1:Ether soln. (3) Digest 5 min., room temp, centrifuge 5 min, remove supernate. (4) Dissolve ppt., add carriers. (5) Ppt as in step (2) above. (6) Digest 5 min, centrifuge 5 min, remove supernate. (7) Dissolve ppt, add carriers. (8) Precipitate as in step (2). (9) Digest 5 min, centrifuge 5 min, remove supernate. (10) Dissolve ppt, add carriers. (11) Make volume to 10 ml with 1 M HNO2, ppt BaSO4 by addition of 1 ml 10% H2S04. (12) Digest 5 min, centrifuge 5 min, remove supernate. (13) Determine yield by weighing and count.

56 Remarks: Decontamination factors: 102 - 103 - Sb. 1 -1005 - Sr, Ir. 106 - 108 - Ca, Ce, Cs, Ru, Ag, Zr. 108 - 109 - Co, Cr, Ta, Sn, Se, I. Yield for Ba is about 55%.

57 CHEMICAL SEPARATIONS Element separated: Iridium Procedure by: Gardner Target Material: Platinum Time for sep'n: - 8 hours metal Type of bbdt: 20 Mev Equipment required: No deuterons special equipment Yield: 70%o Degree of purification: - 106 Advantages: Separates Ir from Pt, Au, Cu, Ni, and Zn with high decontamination factor. Procedure: (1) The Pt target was dissolved in boiling aqua regia and 3 mg Ir carrier and 10 mg each of the following carriers added; Cu, Ni, Zn and Au. (2) The solution was evaporated to incipient dryness, diluted to 10 ml with water and 10 drops conc. HC1 added. (3) Au was extracted 6-8 times with ethyl acetate. (see remark 1) (4) The aqueous phase (yellow-brown) was treated with 1-2 drops H2N NH2 to destroy N03. (Solution turns pale). (see remark 2) (5) Pt was reduced with SnC12 (solution turns deep red) and extracted 6-8 times with ethyl acetate. (see remark 3) (6) The aqueous phase was evaporated to dryness with 2-3 ml aqua regia and 5 mg Pt carrier added. The NO - was removed by addition of 20 drops conc. HC1 and evaporation to dryness. (7) The residue was dissolved in 2 ml H20 and 4 drops 6 N HC1. (8) The solution was saturated with solid NH4C1, warmed to dissolve any excess and cooled in ice for 0.5 hr. The red precipitate of Pt and Ir was washed several times with saturated NH4C1 solution. (9) The precipitate was dissolved in hot water, and NH4+

58 removed by evaporation to dryness with 2-3 ml aqua regia. (10) The residue was dissolved in 2-3 ml H20 plus 2-5 drops conc. HC1 and evaporated to dryness again. (11) The residue was dissolved in 6-8 ml H20 and made basic to litmus with a few drops of saturated NaC003 solution (solution turns from brown to yellow). (12) The solution was heated to boiling, 4-6 ml NaOBr solution (0.5 ml 1 M NHCO0/ 1 ml saturated Br2 solution) added and heating continued until the solution turns greenishblue. (see remark 4) (13) 1-2 drops 6 N HC1 was added to the still warm solution and the solution digested until the IrO2 coagulated. (14) The precipitate was washed several times with H20, dissolved in conc. HBr and evaporated to dryness. The residue was dissolved in H20 and mounted for counting. Remarks: (1) For both the Au and Pt extractions, aqueous phase = 2-4 organic phase New glassware was used for the last extraction in each case. (2) Metallic Pt may precipitate from hot solution. (3) If a red precipitate forms, conc. HC1 is added until it dissolves. In the presence of a large amount of Pt a series of partial reduction and extractions to remove all the Pt is preferred. (4) The addition of a drop of 1 M Na2C03 solution and/or saturated Br2 solution may expedite the formation of the blue-green color.

59 B. Radiochemical Separations The critical evaluation of radiochemical separation procedures which was first reported in Progress Report No. 3 (2) was continued during the period covered by the present report. Procedures reported in the literature for a particular element were collected and subdivided into individual separation steps. Those steps which were found unique and possessing general applicability were studied experimentally to determine optimum conditions (of both yield and contamination) for separation. These procedures were then further evaluated under the optimum conditions to determine the effects on the separation of a number of diverse but representative elements and materials. 1. Alkaline Earth Separations The alkaline earth elements, barium, strontium and calcium were the first elements studied in this manner. Several precipitations were studied to determine the conditions for optimum radiochemical separation within the group. It was found that conditions of operation must vary widely from commonly accepted analytical methods due to the demands of such factors as nonequilibrium operation, necessity for rapid precipitation, character of the precipitate, and manipulatory techniques.

60o The results of these experiments have been written up in detail and have been submitted for publication (9). A preprint of this manuscript is enclosed as Supplement A to this Report. In addition a short summary of the work is presented in the next few pages. a) Yield of the Desired Constituent -- The conditions for performing the nitrate, chromate and chloride precipitations of the alkaline earth elements were varied to show the effects of excess or deficiency of reagents, quantitative or nonquantitative precipitation and methods of adding precipitating reagents. These data were presented in part in Progress Report No. 3 (2) and are given along with the oxalate and sulfate results in Table I. b) Contamination by other Activities -- Sixteen typical tracer elements were studied to determine the contamination by other activities which would be expected when using procedures giving optimum yield. Each separation was conducted in the presence of one of the typical tracers and the contamination by the tracer determined. The precipitation of alkaline earth sulfates and oxalates was also studied since they are used

TABL`E~, I SUMMARY OF YIELD DATA OF PRECIPITATION REACTIONS FOR BARIUM, STRONTIUM AND CACIUJM* Percent Carried Prec ipit at ing Condition Calcium on Solution Barium Strontium Calcium on Barium Strontium Ammonium pH 4 70 + 3.4 1.6 + 0.3 o.8 + 0.o8 Dichromate pH 5 73 + 4.0 8 + 0.2 1.1 + O.b8 pH 6 86 + 1.3 22 + 2.0 1.7 + 0.22 Nitric Acid 80% 100 + 5.3 100 + 1.7 27 + 2.2 51 + 3.2 70% 100 + 3.6 98 +1.4 2.4 + 0.3 11 +2.3 60% 86 + 3.3 81 + 4.2 0.9 + 0.05 2.6 + 1.0 Hydrochloric 3 ml H20 82 + 1.1 2.8 + 0.9 0.6 + 0.4 Acid 1.5 ml H20 92 + 2.2 11 + 0.7 o.8 + o.o8 dry HC1 99 + 0.4 7.3 + 1.6 1.0 + 0.1 Ether:dry HC1 93 + 2.4 6.o + 3 1.5 + 0.1 Ammonium 95% 59 on SrC204 99 100 Oxalate 15 on CaC2O4 Sulfuric Acid xs Sulfate 100 57 on Barium 10 3;6 very slight alone *All values are average of quadruplicate runs. Errors are "standard deviations".

TBT3LE II CONTAMINATION OF ALKALINE EARTH PRECIPITATES BY.OTHER ACTIVITIES* I.... Precipitating Solution, Perzent Carried Ions Always Ions Always Present Element pH 4 0Oqo Nitric 60% Nitric Hydrochloric Oxalate Sulfate Sulfate in Precipitating Solution C hromate Acid Acid Acid on SrC204 on CaC2o4 Antimony 55 47 30 28 44 46 28 N0O3 C1 Barium 70 100 86 82 59 15 100 NO3, Cl Calcium 0.8 51 on Sr 2.6 on Sr 0.6 -- 100 10 NOs, C1 27 on Ba 0.9 on Ba Cerium 6 3.2 2.5 0.9 98 95 7.1 NO3, C1 Cesium 3.5 1 2 1.0 o.8 1.6 2.9 N03, C1 Chromium 1.2 1.8 1.0 0.7 89 96 0.5 NOs3 C1 Cobalt 1.1 3 3.5 1 52 21 0.5 NO3, C1 Iodine 2.0 1.2 o.8 0.9 2.3 5.0 1.5 NO03 Iridium 27 4.2 0.9 5.4 47 68 11 NOs, C1 Ruthenium 5 1.5 2.4 2 23 38 0.6 NO;, C1 Selenium 5.7 1.4 1.3 0.9 21 23 1.2 N03, C1 Silver 89 1.9 1.5 0..8 1.2 2 14 NO3 Strontium 1.6 100 81 2.8 99 -- 57 NO3, C1 Tantalum 10 1 0.7!- 24 o.6 N03, C1, F Tin 99.5 1 1.2 o0.8 73 95 0.5 N03, C1 Zirconium 6.3 2.6 3.3 2 93 88 20 NO3, (F )? *Values are average of duplicates on barium precipitates except where noted.

63 commonly for preparation of samples for counting. The results of these experiments are shown in Table II. (D. N. Sunderman). Silver Exchange Separation The exchange of silver ion between a precipitate of silver chloride and a solution of silver nitrate reaches isotopic equilibrium very rapidly. Because of the low solubility of silver chloride, a very favorable ratio exists at equilibrium between the silver atoms in the precipitate and the silver atoms in the solution. For this reason if silver chloride is added to a solution containing only trace amounts of radioactive silver, a high percentage of this silver will have exchanged with the silver in the precipitate by the time equilibrium is attained. Use has been made of this fact to develop a rapid, highdecontamination, single-step method for the separation (10) of traces of radioactive silver from a solution containing other radioactive species. The results of these experiments have also been written up and submitted for publication (11). A preprint of the manuscript is enclosed as Supplement B to this Report. In addition a short summary of the exchange work is presented in the next few pages.

64 a) Yield of Radioactive Silver -- Recovery of silver tracer in the exchange procedure using 10 mg, 4 mg and 1 mg of silver as AgC1 on the gauze is given in Table III. For each determination 20,000 - 40,000 d/m of Ag-1lO tracer was used. All samples were counted to a probable error of 0.4%. Errors quoted in the table are standard deviations. It should be noted that reproducible although not necessarily quantitative results can be obtained with 5 mg and even 1 mg amounts of silver. Thus it is possible to use such small amounts if, because of self-absorption or other considerations, it is necessary to obtain a high specific activity. b) Contamination by other Activities -- The quantitative procedure was checked with 18 different representative tracers to determine the levels of contamination which might be expected. Long-lived daughter activities of the tracers were also considered since no carriers were present and no attempt was made to separate parents from daughters. In these experiments the only radioactivity present was that of the element being studied. The contamination of the AgC1 gauze by each element is given in Table IV. All results are an average of at least two determinations. These data show that the separation of silver by isotopic exchange is highly specific and capable of high decontamination in one step.

65 Table III Yield of radioactive silver by exchange with silver chloride. Weight of Silver on Gauze Determination 10 mg 4 mg 1 mg 1 99.5% 99.0% 93.0% 2 98.5 99.1 94.3 3 99.8 98.8 94*7 4 99.8 99.0 94.9 5 99.8 98.8 95.8 6 99.2 99.0 7 100,0 98.7 Average and 99.5 + 0.5% 98.9 + 0.2% 94.5 + 1.c Std. Deviation

Table IV Contamination of silver by other activities in isotopic exchange method. Activity % Carried on Gauze Ba-140, La-140 0.00005 Ce-144, Pr-144 0.0001 Cs-134 0.0001 Co-60 0.001-0.0001 Cr-51 0.01 I-131 0. 01-0.001 Ir-192 0.1-0.01 Ru-106, Rh-106 0.1 Sb-124 0.01 Se-75 0.1 Sn-113, In-113 0.1-0.01 Sr-90, Y-90 0. 0001 Ta-182 0.01 Zr-95, Nb-95 0.01-0.001

c) Interferences -- A study was made of the effects of inactive species present in varying concentrations and forms in the solution from which tracer silver is to be removed. About 40,000 d/m of Ag-llO were added to solutions containing the given concentration of interfering specie, the quantitative procedure used to remove the silver activity, and the yield determined. The species chosen were those which were considered to be of most interest, with the greatest likelihood of appearance in process solutions. The values for the silver tracer yield, given in Table V, represent averages of duplicate runs. This study of the effect of inactive species in high concentrations revealed few specific interferences. The only substance which showed adverse effect on the yield of tracer silver at all concentrations was Fe(N03)3 Yield values remained between 93 and 95% for this compound. For other salts and acids included in the study, the effect seems to be one of salt concentration rather than a specific effect of any individual ion or salt. d) Beta-ray Sources -- A comparison of silver-lll to other isotopes for use as beta-ray sources on the basis of ease of preparation, handling and nuclear characteristics is presented in a paper accepted for publication in Nucleonics (12). The method described for the separation of silver-lll is that of isotopic exchange.

Table V Effect of interfering substances upon exchange of silver with silver chloride. Specie Concentration % Yield of Ag-llO Specie Concentration % Yield of Ag-llO HN03 1M 99 Cu (N03 )2 2M 95 4~~- ~ 99 1 97 8 93 0.5 98 12 91 16 85 Zn(N03)2 2M 95 1 97 HC1 0.05M 98 0.5 99 Fe(N03)3 2M 94 1.0 98 1- 93 3 89 0.5 95 o 6 11.1 5 9541 Bi(N03)3 2M 93 H2S04 1.5M 97 1 97 3 90 0.5 100 6 79 NaC2H302 2M 95 }HF 1.1M 98 l-1 97 3.3 98 0.5 98 6.6 83 13.2 57 C2H50H 99% 36 22 18 50 95 HC 2H302 99% 42 2AlN03 2M 86 ((CH3)2C0 99% 70 Al (NO3 ) 3 86 50 95 1 95 25 98 0.5 99

69 This makes possible the routine production of large beta-ray sources of silver-Ill from neutron bombarded palladium, thus supplementing the multimillicurie sources of beta emitting materials. e) General Utilization of Isotopc Exchange -- Investigations were begun to determine the general usefulness of isotopic exchange as a separation technique because of its high specificity and the high decontamination of which it is capable. Its use as a general tool for the technologist, particularly for the separation of I-131 has shown promise. A paper (13) introducing this technique for general separation use has been accepted for presentation at the Nuclear Engineering and Science Conference at Cleveland, Ohio in December 1955. (D. N. Sunderman) 3. General Silver Separations a) Methods Evaluated -- In the selection of which separations were to be evaluated for silver, an attempt was made not only to pick the most popular methods as indicated by the literature search but also to find new methods capable of high decontamination. Two problems are encountered in radiochemical separation of silver that require, in general, different methods of solution. These

70 are first, the separation of silver from other metals and second, its separation from halides, in particular iodine. The four separations that were evaluated in this laboratory consisted of two steps designed to accomplish each of these requirements. The precipitation of the chloride and of the benzotriazole compound were studied as members of a possible series of steps to be used alternately for the separation of silver from other metals by precipitation. The chloride precipitation.is carried out in acid solution while the benzotriazole precipitation is carried out in an ammoniacal solution in which the silver chloride is soluble. For the separation of silver from halide activities, electrodeposition and isotopic exchange were studied. The precipitation by sulfide, hydroxide, or the reduction to metal by chemical means were insufficiently specific for consideration. The precipitation of the iodide or iodate suffered from the same contaminants as the chloride while possessing in both cases the added handicap that they may be quite difficult to dissolve thereby hindering further chemical operations. b) Yield of Silver and Contamination by other Activities — The representative tracer elements were again studied to determine their effect on the purity of the silver separated by the above methods. The data are presented in Table VI.

Table VI Contamination of silver separations by other activities. Tracer Chloride Benzotriazole Electrodeposition Isotopic Exchange (carrier added) (carrier added) (carrier added)(carrier free) (carrier free) Ag-ll0 99 - 1.3% 92 + 5% 99 1.3% variable 99.5 + 0.5% Ce-144,Pr-144 0.5 2.3 insol. 24% 0.0001 Co-60 0.5 2.5 insol. 0.05 0.001-0.0001 Cr-51 0.5 92 0.4 2.1 0.01 Cs-134 0.5 2.5 0.001 0.004 0.0001 I-131 97 98 0. 2 0.04 0.01-0.001 Ir-192 27 29 0.06 0.2-4 0.1-0.01 Ru-106,Rh-106 2.5 2.5 0.03 0.1 0.1 Sb-124 22 52 26 5 0.01 Se-75 0.5 2.7 0.04 0.05 0.1 Sn-113,In-113m 0.8 77 insol. 10 0.1-0.01 Sr-90,Y-90 0.7 2.4 insol. 2.5 0.0001 Ta-182 0o.6 87 insol. 6.4 0.01 Zr-95,Nb-95 0.4 3.9 insol. 1.0 0.01-0.001

72 The chloride method is a good general decontamination step suffering from few specific interferences It is easily dissolved in ammonia and reprecipitated. It is no separation, however, from halide activities. The benzotriazole precipitation is less general in that it is performed in a solution in which many elements are not soluble, but will serve as a decontamination from chloride if this is necessary. It is bulky but easily dissolved in nitric acid. The separation by electrodeposition is a good method for removing silver from halide activities. It is quantitative, rapid and will also decontaminate from other activities that are not readily reducible. The yield and decontamination data for the isotopic exchange separation have been described in the previous section but are included in Table VI for completeness. These results on silver are now being written up and will be submitted for publication in the near future. (D. N. Sunderman) 4. Literature Search and Punch Card Conpilation The file of punch cards described in the last report (2) has been expanded about 50% during the past year. Additional elements that have been covered by checking references in both isotope tables (14, 15)

73 include gold, mercury, radium and francium. In addition numerous progress reports of laboratories such as BNL, ORNL, MIT, ANL and UCRL have been perused. Radiochemical procedures that were found for any element were photocopied and transferred to punch cards. A microfilm of the separation cards compiled to date is enclosed as Supplement D to the Progress Report. This compilation work will continue and it is expected that a number more elements will be covered and in more progress reports will be checked. It has been found that a good undergraduate student can make this type of survey in a reasonable length of time. The compilation has already proven its worth in pointing out the most fruitful steps for use in the studies of the alkaline earths and silver described above. A number of interesting procedures and cross references to new procedures have also been uncovered through this work.

74 IV PERSONNEL, PUBLICATIONS, TALKS A. Personnel Listing Staff Meinke, W. W. Graduate Students Anders, O.* Gardner, D.* (Teaching Fellow, Spring 1955) Hall, K. L.*(t) Sunderman, D. N.* (Predoctoral Fellow, Michigan Memorial Phoenix Project, Fall 1955) Undergraduate Students Burton, A.** Kochanney, G.** ( ' ) Turner, A.** (') Non Staff Ackermann, Isabelle* De, A. K. (Michigan Memorial Phoenix Project No. 95) Maddock, R. S. Typing Anders, E.** Hopkins, S.**(' ) Electronics Barrett, W. E.*(') Shideler, R. W.* Cyclotron Nye, H.** * Half time ** Hourly (') Terminated

75 B. Papers and Reports Published 1. On Project Work (Nov. 1954 - Nov. 1955) a) New Measurements of Radial Sensitivity with Point Millicurie Sources. Oswald U. Anders and W. Wayne Meinke. AECU-2942, (1953). 5 pages, 4 figs. (Revised and published in part, "Millicurie Beta-Ray Point Source", Oswald U. Anders, Nucleonics 13, No. 7, 46 (1955). 1 page, 2 figs.) b) Radiochemical Separations by Isotopic Exchange: A Rapid High Decontamination Method for Silver. Duane N. Sunderman and W. Wayne Meinke. Science 121, 777 (1955). 1 page. (AECU-2988 gives same information in slightly more detail.) c) Small Dry Box for Work with Scintillation Crystals. Wayne A. Cassatt Jr. and W. Wayne Meinke. Nucleonics 3, No. 5, 63 (1955). 1 page, 2 figs. d) Decay Scheme of Y-92. Wayne A. Cassatt Jr. and W. Wayne Meinke. Phys Rev. _, 760 (1955). 5 pages, 3 figs. (AECU-3004). e) Determination of (d,alpha) Reaction Cross Sections. K. Lynn Hall. Nuclear Chemical Research Project Report, University of Michigan September 1955. 222 pages, 56 figs. f) Silver-Ill Beta-Ray Sources. W. Wayne Meinke and D. N. Sunderman. Nucleonics 1_A, November or December 1955. (In press)

76 g) Decay Scheme of In-107. Wayne A. Cassatt Jr. and W. Wayne Meinke. Phys.Rev. December 1, 1955 (In press) h) Utilization of Isotopic Exchange for Radiochemical Separations. D. N. Sunderman and W. W. Meinke. Ind. and Eng. Chem. (Submitted) i) Radiochemical Separations I: Barium, Strontium and Calcium. Duane N. Sunderman and W. Wayne Meinke. Journal Inorg. and Nucl. Chem. (Submitted) j) Radiochemical Separations II: Separation of Radioactive Silver by Isotopic Exchange. Duane N. Sunderman and W. Wayne Meinke. Journal Inorg. and Nucl. Chem. (Submitted) 2. On Other Work Related to Project (Nov. 1954 Nov. 1955) a) Trace-Element Sensitivity: Comparison of Activation Analysis with Other Methods. W. Wayne Meinke. Science 121, 177 (1955). 8 pages, 15 figs. b) Problems Encountered in Routine Use of 10-Kilocurie, Gamma-Radiation Source. John V. Nehemias, L. E. Brownell, W. W. Meinke, and D. E. Harmer. American Journal of Physics 22, 511 (1954). 6 pages, 9 figs. (AECU-2712). c) A Hot Laboratory Facility for University Research: The Michigan Phoenix Memorial Laboratory. W. W. Meinke, A. H. Emmons and H. J. Gomberg. Nucleonics 13, November 1955. (In press)

77 C. Talks 1. D. N. Sunderman, "Radiochemical Analytical Methods: Development and Application", U. of M. Seminar in Analytical-Inorganic and Physical Chemistry, Ann Arbor, November 4, 1954. 2. O. U. Anders, "Models of Nuclear Structure" I and II, U. of M. Seminar in Chemical Physics, Ann Arbor, February 8 and 15, 1955. 3. W. W. Meinke, "Lectures on Nuclear Chemistry" presented in the U. of M. College of Engineering Intensive Course for Practicing Engineers on "Nuclear Reactors and Radiations in Industry", Ann Arbor, August 17 and 18, 1955. 4. W. W. Meinke (with A. H. Emmons and H. J. Gomberg) "A Hot Laboratory Facility for University Research - The Michigan Phoenix Memorial Laboratory" presented by A. H. Emmons at Fourth Annual Symposium on Hot Laboratories and Equipment, Washington, D.C., September 29, 1955. 5. D. N. Sunderman, "Radiochemical Separations by Isotopic Exchange", U. of M. Chemistry Department Colloquium, Ann Arbor, October 20, 1955. 6. W. W. Meinke, Discussion leader on Instrumentation at Symposium on Trace Analysis, New York City, November 4, 1955.

78 7. W. W. Meinke, "Activation Analysis", Symposium Program, Western New York Section, American Chemical Society, Buffalo, New York, November 19, 1955. 8. W. W. Meinke (with D. N. Sunderman), "Utilization of Isotopic Exchange for Radiochemical Separations", to be presented by W. W. Meinke at the Nuclear Engineering and Science Congress, Cleveland, Ohio, December 14, 1955.

79 V. ACKNOWLEDGEMENTS Thanks are again due to Professor W. C. Parkinson, Professor P. V. C. Hough and Harvey M. Nye of the University of Michigan cyclotron group for their kind cooperation and help in furnishing bombardments and in adapting their equipment to our requirements. We are also grateful to J. P. Fitzpatrick, W. E. Ramler and the crew of the Argonne National Laboratory cyclotron and to G. B. Rossi and the crew of the Crocker 60-inch-cyclotron at Berkeley for their help in arranging and making bombardments. Many discussions with Professor M. L. Wiedenbeck of the Physics Department have been most useful. The help of the Isotopes Division of the Atomic Energy Commission in supplying both enriched and radioactive isotopes for use in this work is acknowledged. We sincerely appreciate the assistance of the Michigan Phoenix Memorial Project in generously supporting work parallel to the scope of this project under Phoenix Projects Nos. 68, 76 and 95.

80 VI LIST OF REFERENCES 1. W. W. Meinke, A. H. Emmons and H. J. Gomberg, "A Hot Laboratory Facility for University Research: The Michigan Phoenix Memorial Laboratory", Nucleonics 1_, November 1955. (In press) 2. Nuclear Chemical Research, Progress Report 3, University of Michigan, 1954. 3. K. L. Hall, "Determination of (d,alpha) Reaction Cross Sections", Nuclear Chemical Research Project Report, University of Michigan, September 1955. 4. J. E. Francis, P. R. Bell and G. G. Kelley, Nucleonics 12, No. 3, 55 (1954). 5. B. D. Pate and L. Yaffe, Can. J. Chem. 33, 929 (1955). 6. 0. U. Anders, Nucleonics l, No. 7, 46 (1955). 7. W. W. Meinke, U. S. Atomic Energy Commission Report AECD-2738, (August 1949). 8. H. L. Finston, "Radiochemical Separations", collection and distribution supported by Atomic Energy Commission, National Research Council and Brookhaven National Laboratory (1955). 9. D. N. Sunderman and W. W. Meinke, "Radiochemical Separations I: Barium, Strontium and Calcium". (Submitted for publication) 10. D. N. Sunderman and W. W. Meinke, Science 12_1_, 777 (1955). AECU-2988. 11. D. N. Sunderman and W. W. Meinke, "Radiochemical Separations II: Separation of Radioactive Silver by Isotopic Exchange". (Submitted for publication)

81 12. W. W. Meinke and D. N. Sunderman, "Silver-lll BetaRay Sources". Nucleonics l_, (1955) (In press) 13. D. N. Sunderman and W. W. Meinke, "Utilization of Isotopic Exchange for Radiochemical Separations". To be presented at Nuclear Engineering and Science Conference, Cleveland, Ohio, December 1955. (Also submitted for publication) 14. J. M. Hollander, I. Perlman and G. T. Seaborg, Rev. Mod. Phys. 25,y 469 (1953). 15. K. Way, et al., Nat. Bur. Standards Circ. 499 and Supplements 1950.

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