TY - JOUR

T1 - Determination of trace levels of uranium and thorium in high purity gadolinium sulfate using the ICP-MS with solid-phase chromatographic extraction resin

AU - Ito, S.

AU - Takaku, Y.

AU - Ikeda, M.

AU - Kishimoto, Y.

N1 - Funding Information:
This work was supported by the JSPS KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas No. 26104007, Grant-in-Aid for Specially Promoted Research No. 26000003, and Grant-in-Aid for Young Scientists No. 17K14290. We also thank the companies who provided the purified Gd2(SO4)3·8H2O samples.

PY - 2017/11/1

Y1 - 2017/11/1

N2 - The new Super-Kamiokande-Gadolinium (SK-Gd) project is an upgrade of the Super-Kamiokande (SK) detector. In the SK-Gd project, 0.2% Gd-2(SO-4)-3 is loaded into the 50 kton water tank of the SK. One of the main purposes of the project is to discover supernova relic neutrinos. Neutrino measurements and proton decay searches will also be performed in the SK-Gd. In order to measure solar neutrinos with a low energy threshold of \sim3.5 MeV in the SK-Gd, the main radioactive contaminations, ^{238}U and ^{232}Th, in Gd-2(SO-4)-3{\cdot}8H-2O, should be minimized before loading. Our maximum levels for U and Th are 5 mBq (U)/kg (Gd-2(SO-4)-3{\cdot}8H-2O) and 0.05 mBq (Th)/kg (Gd-2(SO-4)-3{\cdot}8H-2O). In order to measure such low concentrations of U and Th in Gd-2(SO-4)-3{\cdot}8H-2O, we developed the solid-phase extraction technique. Using this method, about 90% or more U and Th could be efficiently extracted while Gd was reduced by a factor of about 10^{4}. This allowed these radioactivity contaminations to be measured precisely as 0.04 mBq/kg (Gd-2(SO-4)-3{\cdot}8H-2O) for U and 0.01 mBq/kg (Gd-2(SO-4)-3{\cdot}8H-2O) for Th. We measured three pure Gd-2(SO-4)-3{\cdot}8H-2O samples using this method and estimated that the purest one contained <0.04 mBq (U)/kg (Gd-2(SO-4)-3{\cdot}8H-2O) and 0.06 \pm 0.01 mBq (Th)/kg (Gd-2(SO-4)-3{\cdot}8H-2O) by the ICP-MS.

AB - The new Super-Kamiokande-Gadolinium (SK-Gd) project is an upgrade of the Super-Kamiokande (SK) detector. In the SK-Gd project, 0.2% Gd-2(SO-4)-3 is loaded into the 50 kton water tank of the SK. One of the main purposes of the project is to discover supernova relic neutrinos. Neutrino measurements and proton decay searches will also be performed in the SK-Gd. In order to measure solar neutrinos with a low energy threshold of \sim3.5 MeV in the SK-Gd, the main radioactive contaminations, ^{238}U and ^{232}Th, in Gd-2(SO-4)-3{\cdot}8H-2O, should be minimized before loading. Our maximum levels for U and Th are 5 mBq (U)/kg (Gd-2(SO-4)-3{\cdot}8H-2O) and 0.05 mBq (Th)/kg (Gd-2(SO-4)-3{\cdot}8H-2O). In order to measure such low concentrations of U and Th in Gd-2(SO-4)-3{\cdot}8H-2O, we developed the solid-phase extraction technique. Using this method, about 90% or more U and Th could be efficiently extracted while Gd was reduced by a factor of about 10^{4}. This allowed these radioactivity contaminations to be measured precisely as 0.04 mBq/kg (Gd-2(SO-4)-3{\cdot}8H-2O) for U and 0.01 mBq/kg (Gd-2(SO-4)-3{\cdot}8H-2O) for Th. We measured three pure Gd-2(SO-4)-3{\cdot}8H-2O samples using this method and estimated that the purest one contained <0.04 mBq (U)/kg (Gd-2(SO-4)-3{\cdot}8H-2O) and 0.06 \pm 0.01 mBq (Th)/kg (Gd-2(SO-4)-3{\cdot}8H-2O) by the ICP-MS.

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U2 - 10.1093/ptep/ptx145

DO - 10.1093/ptep/ptx145

M3 - Article

AN - SCOPUS:85040066076

VL - 2017

JO - Progress of Theoretical and Experimental Physics

JF - Progress of Theoretical and Experimental Physics

SN - 2050-3911

IS - 11

M1 - 113H01

ER -