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The liquid–liquid extraction, recovery of Np(VI) and Np(V) from the solution of Na2CO3 by methyltrioctylammonium carbonate in toluene was investigated. By the graphic slope analyses method, as well as by recording of absorption spectra for obtained solutions and method of calculated determination of solution properties taking into account water activity, composition was established for the carbonate complexes of Np(VI) and Np(V) being extracted, which, depending on extraction conditions, can be expressed by the following formulae's: (R4N)2[NpVIO2(CO3)2], (R4N)3[NpVO2(CO3)2], (R4N)6[NpVIO2(CO3)4], (R4N)2[NpVIO2(CO3)2]·2(R4N)2CO3, (R4N)5[NpVO2(CO3)3], (R4N)7[NpVO2(CO3)4], (R4N)3[NpVO2(CO3)2]·(1–2)(R4N)2CO3, where R4N is the quaternary ammonium cation. The results have been obtained in the experiments, has much interest both in the field of alkaline radioactive waste management and with respect to their usage for extraction of transuranium elements during reprocessing of alkaline radioactive waste, as well as for liquid–liquid extraction purification of uranium and plutonium from admixtures of fission products. These techniques are used within the framework of a new alternative method for reprocessing of spent nuclear fuel in carbonate media the CARBEX (CARBonate EXtraction) process. [ABSTRACT FROM AUTHOR]

Recently a Np-237 target (26 mg) was analyzed for trace Pu isotopes (approximately 300 ppb). This work describes the chemistry required for a Np/Pu separation sufficient for Thermal Ionization Mass Spectrometry (TIMS), as well as the Pu purification from other potential contaminants. A point source was prepared from the purified Pu fraction and the atom ratios were measured via TIMS. The Pu isotopics provide a picture of the Np target's irradiation history, which will also be discussed. [ABSTRACT FROM AUTHOR]