Development of partitioning method

The present paper describes the examination of the possibility to improve denitration and extraction processes by adding oxalic acid in the partitioning process which has been developed for the purpose of separating high-level liquid waste (HLW) into a few groups of elements. First, the effect of oxalic acid in the denitration of HLW was examined to reduce the amount of the precipitate formed during the denitration. As a result, it was found that it was possible to reduce the precipitation of molybdenum, zirconium and tellurium. However, some elements precipitated at any concentration of oxalic acid. The addition of oxalic acid increased the amounts of precipitates of neodymium which was the representative of transuranic elements and strontium which was a troublesome element because of its heat generation. At the extraction process with DIDPA (diisodecyl phosphoric acid), oxalic acid was expected to prevent the third phase formation caused by iron, by making a complex with iron. However, the result showed that oxalic acid did not suppress the extraction of iron. The addition of oxalic acid was no effects on preventing the third phase formation. The influence of the presence of iron on the oxalate precipitation of rare earths was also examined in the present study. (author)