Effect of decontamination factor on core neutronic design of light water reactors using recovered uranium reprocessed by advanced aqueous method

Nakano, Yoshihiro ; Okubo, Tsutomu; Koma, Yoshikazu  

In the case where uranium recovered by an advanced aqueous reprocessing is utilized in light water reactors (LWRs), the effects of the decontamination factor (DF) of the reprocessing on core neutronic characteristics were examined. The amounts of transuranium (TRU) elements and fission products (FP) contained in the recovered uranium depend on the DF of the reprocessing process, and also U is generated by neutron capture of U. These all act as poisons in the fuel. Therefore, in this paper, the additional U enrichment necessary to compensate for the produced TRU, FP and U was evaluated for three cases of representative DF values: 10, 10 and infinity. The low value, 10, corresponds to the advanced aqueous reprocessing process investigated here. An APWR core with a discharge burnup of 49 GWd/t when the initial U enrichment is 4.6% was considered as the reference core. It was calculated that the recovered uranium has to be re-enriched up to 5.24% even when DF is infinity in order to achieve the same burnup of 49 GWd/t as the reference core. On the other hand, it was also found that the necessary U enrichment after the advanced aqueous reprocessing studied here with the low DF value 10 is only slightly different. The effect of the DF value on moderator reactivity coefficient was also studied, and no effect was found.