Keywords:Continuous air monitor, in-situ monitoring, alpha aerosols, nuclear fuel debris, decommissioning
A large amount of radioactive aerosols are expected to be dispersed during large-scale retrieval of fuel debris at the decommissioning of Fukushima Daiichi Nuclear Power Plant (1F) and nuclear fuel facilities. Particulates containing alpha-nuclides (alpha-aerosols) have high effective dose coefficients upon inhalation, therefore appropriate control and monitoring are required. Conventional dust monitors using SSBD have difficulties with moisture resistance and clogging of filter paper. We have developed an in-situ alpha air monitor (IAAM) that directly measures alpha-rays from aerosols using thin scintillator, multi-anode photomultiplier tube and flat-type-flow path equipped with a heater. In this presentation, we report on the basic performance evaluations, the change in particle size due to air drying, and the improvement of the power supply for on-site implementation at 1F.