Solidification of ion-exchange resins by hydrothermal hot-pressing

Abstract

In Japan, some spent resins generated from a nuclear power station have been solidified by adding cement, plastics, and asphalt. However, if resins could be solidified by themselves without a solidifying material, this would reduce the volume of radioactive waste compared with ordinary solidification systems. On the other hand, various kinds of inorganic powder can be solidified by applying mechanical compression, particularly under hydrothermal conditions, due to recombination among various particles. This would possibly result in excessive lowtemperature sintering for ceramics which are awkward to sinter [1], which is also adopted for application to solidify radioactive waste [2-4]. Details regarding this reaction process have not yet been revealed, but a mixed powder which consists of both acid and base radicals is easily solidified [5]. The solidification reaction easily occurs while continuously keeping the mixture of cation and anion exchange resins compressed under hydrothermal conditions. Dehydration was considered to occur between sulphonic acid ( -SO3H) from cation exchange resins and quaternary ammonium [-CH2-N(CH3)3OH] from anion-exchange resins on terminal groups. Fig. 1 shows the hydrothermal hot-pressing apparatus [6]. The cation-exchange powder resins (PCH Powdex; Graver Co.) used had 3.21 mEqg -1 ion-exchange capacity and contained 52% moisture in the form of sulphonic acid ( -803 H) as the functional base. The anion-exchange powder resins (PAO Powdex; Graver Co.) used had 2.31 mEq g-1 ion-exchange capacity and contained 49% moisture in a form of the quaternary ammonium base [-CH2-N(CH3)3OH] as the functional base. The