On-site Quantitative Nuclear Fuel Debris Analysis by Portable 950 keV/3.95 MeV X-ray/Neutron Sources in Fukushima

2. Japan Atomic Energy Agency (JAEA), Japan

Abstract: On-site inspection system to estimate Uranium (U)/Plutonium (Pu) mass density in nuclear fuel debris in TEPCO Fukushima Daiichi nuclear power plant is proposed by using the portable 950 keV / 3.95 MeV X-ray / neutron sources. The two portable X-ray / neutron sources have been already applied to on-site transmission inspection of real bridges in Japan. Two colored X-ray CT is applied to determine three dimensional (3D) atomic number distribution of the debris and nuclear resonance transmission absorption (NRTA) enables identification of U/Pu. Thus, we can estimate U/Pu mass density so that the criticality control is available for safe storage of the debris. We have successfully performed a proof-of-principle experiment using model debris samples. The next experiment using new model debris samples containing real natural U is planned in 2019. Further, we are proposing a quick in-site U/Pu mass density estimation system for mass-extraction of large amount of fuel debris from the reactors.