Electrodeposition of241Am and244Cm in Spent Nuclear Fuel Samples for Alpha-Spectrometry

Abstract

Determination of fission products and actinide elements produced during irradiation in a nuclear power reactor is of importance for the chemical characterization of the spent nuclear fuels. Especially, the exact amount of transuranium elements, such as Np, Pu, Am, Cm and their isotopes, are useful to understand the burn-up behavior of the fuels because the isotopes of these elements are produced and decay by various pathways during irradiation and cooling. The radioactive material samples containing alpha-emitting nuclides should be handled in a shielded facility. Consequently, the analytical method for these materials, including sample pretreatment, is limited to some extent compared with that for non-radioactive samples. Generally, the determination of the actinides in neutron irradiated samples is widely performed by alpha-spectrometry after separation by ion exchange or solvent extraction. Thermoionization mass spectrometry is also widely used to measure isotope ratios after separation of the elements by ion exchange chromatography. Several methods have been reported for the electrodeposition of actinides in electrolyte buffer solutions, such as mixed oxalate-chloride matrix, 1 NaHSO4-H2SO4-NH4 buffer system, 2 ammonium oxalate-ammonium sulfate, 3 isopropanol medium 4 and NaHSO4-Na2SO4 matrix, 5 since Talvitie's method 6 using ammonium sulfate was introduced in 1972. However, most of these methods were applied for the electrodeposition of actinides in environmental samples containing trace amount of nuclides. Of these methods, the matrix of NaHSO4-Na2SO4 was selected as an electrolyte because this system has an advantage over pH adjustment, which is controlled only by the concentrations of the NaHSO4 and Na2SO4 solutions, and also has not been applied for Am and Cm in spent nuclear fuel samples. This method is especially convenient to handle the radioactive samples in a shielded space because no additional pH adjustment with acid or base is required. We tried the electrodeposition of 241 Am and 244 Cm in spent