Organic reductants of Pu and Np ions in wet technology for spent nuclear fuel reprocessing

Abstract

Scientific, technical, and patent information on the use of organic compounds as reductants of Pu and Np ions in wet technology for spent nuclear fuel reprocessing is summarized and correlated. Organic derivatives of hydrazine and hydroxylamine, and also oximes and urea derivatives at relatively low acidities and temperatures reduce Np(VI) to Np(V) and Pu(IV) to Pu(III). As the acidity and temperature are increased, Np(V) is slowly reduced to Np(IV). Alcohols, aldehydes, hydrocarbons, and acetic acid were identified among products of oxidation of the organic compounds in nitric acid medium. The above-named organic reductants can be used in different steps of the PUREX process: separation of Pu and Np from U in the first extraction cycle, purification of U to remove Np in the second cycle of uranium purification, and Pu stripping in the step of its final purification. Laboratory experiments performed on countercurrent extraction installations of mixer-settlers and of centrifugal contactors demonstrated the possibility of reaching high separation factors of U from Pu and/or Np and high degrees of plutonium concentration to obtain Pu strips containing up to 150 g L−1 Pu.