Determination of the weight and composition of the precipitates formed in the course of dissolution of irradiated WWER oxide fuel

Abstract

The amount and composition of insoluble precipitates formed in the course of dissolution of spent fuel samples with the burn-up from 15 to 54 MW day (kg U)−1 were examined. The weight of the insoluble precipitates was from 0.03 to 0.44% of the fuel weight. The major elements determining the composition of the precipitates were platinum group metals (Pd, Rh, Ru), Zr, and Mo. The specific β- and α-activity of the precipitates obtained was 30–840 and 0.01–8 Ci kg−1, respectively. The major factor determining the concentration of α-emitting nuclides is the fuel burn-up. Depending on the dissolution conditions, the U content was 0.2–4, and the Pu content, 0.1–3%. The weight of secondary precipitates was from 0.005 to 0.3% of the irradiated fuel weight, or 11–50% of the total weight of the precipitates obtained in the experiments. The specific β-activity of the secondary precipitates obtained varies from 5 to ∼300 Ci kg−1 and is determined by the same radionuclides as in the primary precipitates. The α-activity of the secondary precipitates increases with the burn-up and amounts to 0.1–30 Ci kg−1. The values obtained vary only slightly depending on the dissolution conditions and on the time of solution keeping before control filtration.