「最も測定が困難な核物質」を非破壊測定する新技術を開発～東京電力福島第一原子力発電所の燃料デブリ本格取り出し時の測定に期待～

2025-07-18 日本原子力研究開発機構

日本原子力研究開発機構は、福島第一原発の廃炉に向け、燃料デブリ中の核物質を非破壊で測定できる新技術「高速核分裂中性子同時計数法（FFCC）」を開発。従来法は中性子吸収材の影響で測定困難だったが、FFCCは高速中性子と複数の高感度検出器を用い、核分裂中性子の同時放出を検出することで吸収材の影響を回避。実験により吸収材混在試料でも正確なウラン量測定が可能と確認され、燃料デブリ管理や核セキュリティへの応用が期待される。

燃料デブリ中の核物質量を非破壊測定可能な新しい手法を開発

＜関連情報＞

燃料デブリ仕分けのための非破壊測定法
Non-destructive measurement method for fuel debris sorting

Toh, Yosuke; Maeda, Makoto; Komeda, Masao

The decommissioning of the Fukushima Daiichi Nuclear Power Station is currently in progress. In this process, one of significant issues is the measurement of the quantity of nuclear fuel material contained in materials retrieved from the primary containment vessel. Non-destructive measuring method unaffected by neutron absorber materials is desirable since fuel debris may contain neutron absorber materials. The fast fission neutron coincidence counting method is a non-destructive nuclear material measurement technique that utilizes fast neutrons less affected by neutron absorber materials. This method distinguishes between irradiation and fission neutrons by taking advantage of the simultaneous emission of multiple neutrons in fission reactions. In this study, a measurement system using liquid scintillation detectors was constructed for simulation, and the performance expected when applied to fuel debris was evaluated by Monte Carlo simulation (PHITS). As a result, it was found that measurements of fuel debris containing neutron absorber materials are possible, while it is difficult to measure using the conventional methods. Furthermore, it was found that overall measurement accuracy improves compared to the conventional methods. This research was implemented under the subsidy for the Decommissioning, Contaminated Water and Treated Water Management project.