Development of Neutron Measurement System for Radiation Therapy Field Using the Activation of a Scintillator

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K04996
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 31010:Nuclear engineering-related
• Research Institution: Kindai University
• Principal Investigator: Wakabayashi Genichiro 近畿大学, 原子力研究所, 教授 (90311852)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: シンチレータ / 自己放射化 / 熱中性子束 / ヨウ化セシウム / カドミウムフィルタ法

Outline of Final Research Achievements

When a cesium iodide (CsI) scintillator is irradiated by neutrons, the iodine and cesium contained in the scintillator are activated, and Cs-134m and I-128 are produced as activation products. Since these products are contained in the scintillator as internal radiation sources, the radioactivity can be measured with extremely high detection efficiency. In addition, since a large amount of radioactivity can be obtained with a short irradiation time, measurement with high sensitivity is possible. In this study, we developed a simple method to measure thermal neutron flux without using the cadmium filter method by utilizing the fact that two kinds of nuclides (Cs-134m and I-128) are produced in the scintillator by a single short time neutron irradiation.

Free Research Field

放射線工学

Academic Significance and Societal Importance of the Research Achievements

本研究で開発した中性子測定法は、従来の方法よりも簡便に高感度な測定が行える方法である。従来の放射化法では、熱中性子束を求める際にカドミウムフィルタ法を用いる必要があり、2回の中性子照射が必要であった。また弱い熱中性子束を測定するためには長時間の照射が必要であった。本方法では、短時間の1回の照射で比較的弱い熱中性子束を精度よく定量することが可能であり、放射線治療場で発生する二次中性子の測定や、低出力原子炉を用いた照射実験における中性子束測定に活用することができる。