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Preparation of I131 from irradiated uranium oxide
InternationalJournalof Applied Radibon and tOtopq 1964,Vol. 15, p. 695. PcrgamonPI-W Ltd. Printedin NorthernIreland
Preparation of Psl from Irradiated Uranium Oxide (Receiued 24 April 1964)
rntroduction LARGE amounts of carrier-free Ilsl are produced from neutron irradiated tellurium. However, because of the quantity of tellurium required, this procedure is not feasible when the flux available for irradiation is low (5 x 10” n/cm2 set) and the requirements of Ilsl are large (-2c/month). For this reason we have developed a dry distillation method to prepare llsl directly from irradiated enriched uranium. The simplicity of the method makes it especially suitable for remote control operations. The “wet distillation” of Ilsl from irradiated uranium has been described previously.(l,a) FISHER(~) and &VAERTs”) suggested the possibility for separating I’*l by thermal diffusion from irradiated uranium oxide. We investigated a dry distillation of Ilsl from uranium oxide in order to avoid the involved chemical procedures of the “wet” separation method. We found that we can distill 1131from irradiated UO, in a current of air at, a temperature of 800°C with a yield of about 70 per cent. Under these conditions, the ruthenium isotopes also distilled, but contamination of Ilsl by ruthenium was completely avoided by passing the distillate through iron shavings heated to 700°C.
Samples of UO, were prepared from uranyl nitrate by precipitation of UO,.xH,O with hydrogen peroxide. The precipitate was heated for 12 hr at 12O”C, pulverized and heated again to the same temperature. This treatment yielded an orange oxide, amorphous UO,, together with small amounts of U0,.2H,0t6). The oxide so obtained is more easily converted to UsO, by heating. Samples of UO, were prepared by reduction of UO, by hydrogen at 850°C. The samples of powdered UO, and UO, were irradiated for 8 days and, 15 days later, they were heated to different temperatures in order to determine the optimum conditions for distillation of Ils1. The removal of I’sI from heated uranium oxide was facilitated by flowing air 695
through the system (0.5 ljmin). The I’*1 was collected in a solution containing sodium hydroxide (0.2N) and sodium bisulfite (0.2N). In preliminary experiments we found that considerable amounts of Ru109 and Rules were distilled along with the Ilsl. In order to avoid this contamination, the vapors from the distillation were passed through iron shavings heated to 700°C. A quantitative retention of ruthenium was observed (>99 per cent). The original content of IIs in the irradiated siimples was calculated from the amount of Sren present in the uranium oxides after distillation. The maximum 1131yield observed after 10 hours of distillation from UO, was only 25 per cent at temperatures between 700°C and 1000°C. With UO, the maximum yield of IIs observed (70 per cent) took place between 700°C and 930°C. This result may suggest that the Ilsl diffusion takes place mainly during the transformation of UO, to U,O, which, under our experimental conditions, is complete at 650’C(5). Below 700°C or above 930°C the yield of I1sl from UO, decreased sharply. The distillation of 11s’ begins near 3OO”C, since the yield at 300°C was only 15 per cent. The decrease in yield at a temperature of 1030°C (56 per cent) was most probably due to a rapid sintering of the powder which could be observed directly. The radioactive purity of Ilsl as tested by y-spectrometry and /?-counting of its decay, was greater than 99 per cent. Programa de Prodwxidn Comisidn Nacionul de Energia Atdmica Buenos Aires, Argentina
s. R.
h3RASHKlN+
RADICELLA
References 1. 2.
3.
4. 5.
E. E. and FARMAKESJ. R. Report ORNL-1047 (1951). ARROL W. J., CHADWICK J. and EAKINSJ. Progress in Nuclear Energy, Series III, Vol. 1, p. 356. Pergamon Press, London ( 1956). FISHER C. Ind. chim. Beige 19, 785 (1954). GOVAERT~ J. Introduction d la Chimie Nucliaire, Dunod, Paris (1961). KATZ J. J. and RABINOWITCH E. The Chemistry of Uranium,McGraw-Hill, New York (195 1). RUPP A. F., BEAUCHAMP
* Present address: Nuclear Chemistry Department, Soreq Research Establishment, Israel Atomic Enem Commission, Rehovoth, Israel.
Preparation of Psl from Irradiated Uranium Oxide (Receiued 24 April 1964)
rntroduction LARGE amounts of carrier-free Ilsl are produced from neutron irradiated tellurium. However, because of the quantity of tellurium required, this procedure is not feasible when the flux available for irradiation is low (5 x 10” n/cm2 set) and the requirements of Ilsl are large (-2c/month). For this reason we have developed a dry distillation method to prepare llsl directly from irradiated enriched uranium. The simplicity of the method makes it especially suitable for remote control operations. The “wet distillation” of Ilsl from irradiated uranium has been described previously.(l,a) FISHER(~) and &VAERTs”) suggested the possibility for separating I’*l by thermal diffusion from irradiated uranium oxide. We investigated a dry distillation of Ilsl from uranium oxide in order to avoid the involved chemical procedures of the “wet” separation method. We found that we can distill 1131from irradiated UO, in a current of air at, a temperature of 800°C with a yield of about 70 per cent. Under these conditions, the ruthenium isotopes also distilled, but contamination of Ilsl by ruthenium was completely avoided by passing the distillate through iron shavings heated to 700°C.
Samples of UO, were prepared from uranyl nitrate by precipitation of UO,.xH,O with hydrogen peroxide. The precipitate was heated for 12 hr at 12O”C, pulverized and heated again to the same temperature. This treatment yielded an orange oxide, amorphous UO,, together with small amounts of U0,.2H,0t6). The oxide so obtained is more easily converted to UsO, by heating. Samples of UO, were prepared by reduction of UO, by hydrogen at 850°C. The samples of powdered UO, and UO, were irradiated for 8 days and, 15 days later, they were heated to different temperatures in order to determine the optimum conditions for distillation of Ils1. The removal of I’sI from heated uranium oxide was facilitated by flowing air 695
through the system (0.5 ljmin). The I’*1 was collected in a solution containing sodium hydroxide (0.2N) and sodium bisulfite (0.2N). In preliminary experiments we found that considerable amounts of Ru109 and Rules were distilled along with the Ilsl. In order to avoid this contamination, the vapors from the distillation were passed through iron shavings heated to 700°C. A quantitative retention of ruthenium was observed (>99 per cent). The original content of IIs in the irradiated siimples was calculated from the amount of Sren present in the uranium oxides after distillation. The maximum 1131yield observed after 10 hours of distillation from UO, was only 25 per cent at temperatures between 700°C and 1000°C. With UO, the maximum yield of IIs observed (70 per cent) took place between 700°C and 930°C. This result may suggest that the Ilsl diffusion takes place mainly during the transformation of UO, to U,O, which, under our experimental conditions, is complete at 650’C(5). Below 700°C or above 930°C the yield of I1sl from UO, decreased sharply. The distillation of 11s’ begins near 3OO”C, since the yield at 300°C was only 15 per cent. The decrease in yield at a temperature of 1030°C (56 per cent) was most probably due to a rapid sintering of the powder which could be observed directly. The radioactive purity of Ilsl as tested by y-spectrometry and /?-counting of its decay, was greater than 99 per cent. Programa de Prodwxidn Comisidn Nacionul de Energia Atdmica Buenos Aires, Argentina
s. R.
h3RASHKlN+
RADICELLA
References 1. 2.
3.
4. 5.
E. E. and FARMAKESJ. R. Report ORNL-1047 (1951). ARROL W. J., CHADWICK J. and EAKINSJ. Progress in Nuclear Energy, Series III, Vol. 1, p. 356. Pergamon Press, London ( 1956). FISHER C. Ind. chim. Beige 19, 785 (1954). GOVAERT~ J. Introduction d la Chimie Nucliaire, Dunod, Paris (1961). KATZ J. J. and RABINOWITCH E. The Chemistry of Uranium,McGraw-Hill, New York (195 1). RUPP A. F., BEAUCHAMP
* Present address: Nuclear Chemistry Department, Soreq Research Establishment, Israel Atomic Enem Commission, Rehovoth, Israel.