Precipitates formation behavior in simulated high level liquid waste of fuel reprocessing.

Abstract

To clarify various kinds of precipitates formation behavior in high level liquid waste (HLLW) from the nuclear fuel reprocessing process, undissolved materials generated in concentration step under vacuum evaporation and aging step at various temperatures and nitric acid concentrations using simulated HLLW solution were closely investigated. Three kinds of material, mixed crystalline salt of barium and strontium (Ba0.5Sr0.5(NO3)2), phosphomolybdic acid (P2O5·24MoO3·7H2O), and zirconium molybdate (Zr(OH)2·Mo2O7·(H2O)2) were obtained as the precipitates in the simulated solution. Mixed crystalline salt and phosphomolybdic acid were formed during concentration process. Yield of the former depended on solubility of barium nitrate in nitric acid, so the precipitate was redissolved at concentration below 6 M HNO3 because of a large solubility at low concentration of HNO3. The yield of the latter depended on concentration factor of HLLW, but the precipitate was not redissolved at concentration of 2–10 M HNO3 in ...