Determination of trace level thorium and uranium in high purity gadolinium sulfate using ICP-MS with solid-phase chromatographic extraction resins

The Super Kamiokand-Gadolinium (SK-Gd) project is the upgrade of the Super-Kamiokande (SK) detector in order to discover Supernova Relic Neutrinos (SRNs) by loading 0.2% of Gd-2(SO4)(3) into a 50 kton of the SK water tank. In order to continue solar neutrino measurement with low energy threshold at similar to 3.5 MeV, main radioactive contamination, U and Th in Gd-2(SO4)(3), should be purified before loading. We developed solid-phase extraction technique to measure low concentration of U and Th in Gd-2(SO4)(3) by ICP-MS. The extraction technique and current status will be presented.