Methods for obtaining a tritium condensate during reprocessing of spent nuclear fuel

Abstract

When spent nuclear fuel is reprocessed, a definite mount of the tritium contained in fuel passes, on being dissolved in nitric acid, into solution in the form of tritium water. This solution is then spread through the liquid flows in the extraction separation of uranium and plutonium and also recovery of nitric acid from the raftinates. A large part of the solution ultimately enters the tritium condensate, which is ordinarily discarded [1][2][3]. It is ecologically safer to localize the tritium, for example, by solidifying the condensate to a minimum volume with a maximum localization.We present below some results of a check, using simulators, of alternative methods for obtaining the tritium condensate. Tritium was introduced into the simulating solutions in the form of tritium water. The concentration in the solutions was determined radiometricaUy on a RZhS-05 setup with a ZhS-8 scintillation liquid.Preparation of Tritium Condensate by Evaporation. The tritium-containing solutions were evaporated in a glass evaporation apparatus with a capacity of 0.2-1 liter/h under a pressure of 400 mm Hg. The solutions were prepared using a weighed portion of the commercial chemical reagents.1. Evaporation of the obtained solution by dissolving the spent fuel. The composition of the simulation solution was as follows (g/liter): HNO 3 200, UO2(NO3) 2 500, tritium 0.15 Ci/liter. The solution was evaporated to a concentration corresponding to the composition of uranyl-nitrate hexahydrate, i.e., by approximately a factor of 4. As a result, its minimum volume was equal to 0.8 of the initial volume, and the maximum degree of tritium localization was equal to 86 %.2. Evaporation of the raft'mate formed with extraction of uranium in the first cycle. The composition of the simulation raffmate was: HNO 3 200 g/liter, total nitrates Fe 3+ , Cr 3+, La 3+, Ce 3+, Ba 2+, Sr 2+, ZrO22+ , Cs +, 8.6 g/liter, tritium 0.1 Ci/liter. For evaporation by a factor of 40, the minimum volume was found to be approximately equal to the initial volume with a maximum degree of tritium localization equal to 97%.In summary, in the case when nitric-acid water solutions were evaporated, the tritium was distributed between the condensate and the vat residue almost proportionally to their volumes.Preparation of Tritium Condensate by Removal with Live Steam. This possibility follows from the data on the liquid-steam equilibrium in the system HNO3-H20-HTO [4].Tritium was removed, using live steam, from a solution with the composition indicated in paragraph 1 above, in a 30 mm in diameter plate column (LDR apparatus, Industrial Association "Khimlaborpribor," in the city of Klin).A minimum volume of the condensate equal to 0.74 of the initial volume with a maximum tritium localization of 67% was obtained with three plates and a volume of 0.82 and 94% localization was obtained with 20 plates, respectively. Therefore driving off the tritium with live steam is more effective than evaporation.Preparation of the Tritium Condensate by Rectification of Liquor Vapors. When...