Method for simultaneous determination of ambient dose equivalent rate and activity concentration in air for environmental radiation monitoring

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K06966
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Nuclear engineering
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: kowatari munehiko 国立研究開発法人日本原子力研究開発機構, 原子力科学研究部門 原子力科学研究所 放射線管理部, 主査 (80391283)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 放射線防護 / 環境放射線 / モニタリング / CeBr3検出器

Outline of Final Research Achievements

A method to simultaneously determine ambient dose equivalent rate and radioactivity concentration in air by using a newly developed scintillation spectrometer was investigated. The performance of the proposed method was verified by a series of measurements, conducted according to the procedure of inter-comparison by EURADOS. Results show that the proposed method is suitable for environmental monitoring purposes. The activity concentration in air was determined in the laboratory by using a point-like sealed 133Ba source. The photon fluence rate was obtained from the pulse height distribution by using the unfolding method, and the activity concentration in air for radioisotopes of interest, mainly 133Xe, was estimated from the obtained photon fluence rate by applying the conversion coefficient evaluated via a Monte Carlo calculation. The results additionally show that the method presented in this study is reliable and suitable for the environmental radiation measurement.

Free Research Field

環境放射線

Academic Significance and Societal Importance of the Research Achievements

福島第一原子力発電所事故直後に発生した放射性希ガスの分布の正確な測定ができなかったが、本研究事業で開発した手法を用いることにより、原子力事故ごく初期に生じるイベントを適切に検知できるようになる。得られた測定結果を用いることにより、原子力事故時のソースターム推定をより精度よく行うことができるほか、測定により、住宅密集地、山林、耕作地等への放射性希ガス及び放射性ヨウ素の移行・沈着の挙動、という、微視的でローカルな拡散の挙動を適切にとらえることができる。原子力防災の観点から、本手法の導入により、公衆被ばくを過小評価せず、実測に基づいた避難指示等を適切に出せることが期待される。