Studies on resin degradation products encountered during purification of plutonium by anion exchange

Among the methods available for the purification of plutonium in Purex process, anion exchange method offers several advantages. However, on repeated use, the resin gets degraded due to thermal, radiolytic and chemical attacks resulting in chemical as well as physical damage. Frequently, plutonium product eluted from such resin contains significant quantities of white precipitates. A few anion exchange resins were leached with 8 M HNO3 at 60-80degC and the resin degradation products (RDP) in the leach-extract were found to give similar precipitates with tetravalent metal ions like Pu(IV), Th(IV) etc. Tetra propyl ammonium hydroxide in 8 M HNO3 (TPAN) also gave a white precipitate with plutonium similar to the one found in the elution streams. The results indicate that delinked quaternary ammonium functional groups might be responsible for the formation of precipitate. The characteristics of precipitates Th-RDP, Th-TPAN and that isolated from elution stream have been investigated. In a separate study a tentative formula for Th-RDP compound is proposed. The influence of RDP on the extraction of plutonium and other components in Purex process was studied and it was found that RDP complexes metal ions thus marginally affecting the kd values. A spectrophotometric method has been standardised to monitor the extent of degradation of anion exchange resins which is based on the ability of RDP to reduce the colour intensity of Th-thoron complex. This technique can be used to study the stability of the anion exchange resins. (author). 8 refs., 8 tabs., 5 figs.,