Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 65(4): 157-167 (2016)


国家標準にトレーサブルな放射性セシウム分析用玄米認証標準物質の開発The Development of SI Traceable Brown Rice Certified Reference Material for Caesium 134 and Caesium 137 Measurement

1産業技術総合研究所計量標準総合センターNational Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology ◇ 305–8563 茨城県つくば市梅園1–1–1 ◇ 1–1–1 Umezono, Tsukuba-shi, Ibaraki Pref. 305–8563, Japan

2農業・食品産業技術総合研究機構食品総合研究所National Food Research Institute, National Agriculture and Food Research Organization ◇ 305–8642 茨城県つくば市観音台2–1–12 ◇ 2–1–12 Kannondai, Tsukuba-shi, Ibaraki Pref. 305–8642, Japan

受付日:2015年7月6日Received: July 6, 2015
受理日:2016年1月8日Accepted: January 8, 2016
発行日:2016年4月15日Published: April 15, 2016

放射性セシウム分析の妥当性が確認できる玄米認証標準物質を開発した。2011年に収穫された玄米粒を均質化し,認証標準物質の原料とした。134Cs, 137Cs放射能濃度の認証値は校正されたGe半導体検出器による測定で決定した。Ge半導体検出器のピーク計数効率は国家標準にトレーサブルな134Cs及び137Cs放射能標準液で求めた。測定と均質性に基づく標準不確かさから算出した認証値の拡張不確かさは134Cs放射能濃度が5.9%,137Cs放射能濃度が5.5%であった。

The certified reference material of brown rice grain was developed for validation in measurements of massic activities 134Cs and 137Cs. The homogenized brown rice harvested from north east area of Japan at 2011 was used as raw material of the certified reference material. The certified values of 134Cs and 137Cs in brown rice grain certified reference material were determined using the calibrated Ge semiconductor detectors. The counting efficiencies of 134Cs and 137Cs on the Ge semiconductor detectors were calibrated by standard solutions of 134Cs and 137Cs traceable to the national standard. The certified values of the certified reference material is close to the radioactive caesium standard value in general foodstuff set by Ministry of Health, Labour and Welfare of Japan. The associated expanded uncertainties of the certified values were calculated from standard uncertainties related 134Cs and 137Cs measurements and homogeneities of 134Cs and 137Cs. The relative expanded uncertainties of massic activities of 134Cs and 137Cs are 5.9% and 5.5%, respectively.

Key words: Certified reference material; Brown rice; Ge semiconductor detectors; National standard; Caecium 134; Caecium 137; Uncertainties

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