3rd-INCC

Development of an original radiochemical protocol in a view of Sn-121m and Sn-126 measurements in Low and Intermediate Level Nuclear Wastes

19 Sept 2011, 17:30

1h 30m

Paladini (Città del Mare, Terrasini - Palermo - Sicily - Italy)

poster Nuclear Chemistry and Radiochemistry Poster Section 1

Speaker

Dr Celine Gautier (CEA Saclay DEN/DANS/DPC/SECR/LANIE)

Description

The LANIE (Elemental, Isotopic and Nuclear Analysis Laboratory) develops and implements a set of radiochemical protocols associated with radiological and elemental measurement techniques devoted to the characterization of Long Lived Radionuclides in Low and Intermediate Level Nuclear Wastes. 121mSn and 126Sn are two radionuclides of interest for the performance assessment of waste storage or disposal. Both isotopes are produced from the fission of 235U occurring in nuclear reactors, with thermal fission yields estimated to be about 0.00003% and 0.06% respectively. 121mSn can also be produced by activation of tin present as a minor additive in zircaloys, inconels and steels used in the nuclear industry. Due to their half-lives (55 and 250000 years for 121mSn and 126Sn respectively [1,2]), the National Radioactive Waste Management Agency (ANDRA, France) requests their monitoring in waste packages before their disposal in specific sites. Due to their low activities in nuclear wastes, 121mSn and 126Sn need a thorough chemical separation before any measurement can be performed. The radiochemical protocol was first developed on various synthetic solutions to separate tin from the matrices and concentrate it prior to any nuclear or mass spectrometry measurements. The protocol starts with a microwave digestion or alkaline fusion with the addition of a natural tin carrier and a 113Sn radioactive spiker. The following steps are constituted of ion exchange separations combined with co-precipitations and a highly selective ethylation step. The final purified fractions thus obtained are suitable for X spectrometry analysis of 121mSn and Q-ICPMS measurements of 126Sn. The protocol yield is evaluated by gamma measurement of 113Sn. The protocol was then optimized to be applicable to various sample types. As no 121mSn or 126Sn sources are commercially available, the protocol was first applied to zircaloys and spent nuclear fuel dissolution solutions to obtain in-house standards. The radiochemical procedure was validated subsequently on ion exchange resins spiked with 113Sn, 121mSn and 126Sn. Afterward, it was completed for the analyses of radioactive sludges and activated steels. This procedure enables to achieve high decontamination factors and to eliminate specifically all isobaric interferences (126Te, 110Pd16O, 110Cd16O) for 126Sn analysis by Q-ICPMS. The overall separation yields obtained range from 45% up to 70%. References: [1] S.A. Catlow et al., “Half-life measurement of 126Sn isolated from Hanford nuclear defense waste”, Journal of Radioanalytical and Nuclear chemistry, vol 236, no3, p599-603, 2005. [2] P. Bienvenu et al., “Determination of 126Sn half-life from ICP-MS and gamma spectrometry measurements”, Radiochimica Acta, vol 97, no 12, p687-694, 2009.