With the development of nuclear power industry, more attentions have been paid on reprocessing power reactor spent fuel. Up to now, PUREX process is the only process available commercially. The process achieves uranium and plutonium separation by means of quick and quantitative reduction of Pu (Ⅳ) to Pu (Ⅲ). Therefore the reductant is very important in PUREX process. Preliminary experiment results,[1], show that N, N-dimethyl hydroxylamine not only reduces rapidly Np (Ⅵ) and Pu (Ⅳ) to Np (Ⅴ) and Pu (Ⅲ), but also stabilizes the Np (Ⅴ) and Pu (Ⅲ) in acid solution. It may become a salt-free reductant with promising future for applications in the area,[2],. However, organics decompose under intense radiation environment, and this affects its reduction efficiency, and products from the degradation may affect separation of the radioactive elements.