How to Evaluate and Reduce the Risks of Dissemination of Radioactive Aerosols During Fuel Debris Retrieval Operations at Fukushima Daiichi - 23035

The general context of the article is to evaluate strategies that can be used to mitigate aerosols dispersion during the fuel debris or corium retrieval of Fukushima damaged reactors. IRSN is involved in several projects led by ONET Technologies along with CEA to provide relevant information to analyze the risk of aerosol resuspension induced by fuel debris retrieval. The knowledge of the aerosol source term emitted during fuel debris retrieval operations is one of the key issues for the assessment of aerosol dispersion that can lead to the release of radionuclides into the environment and also to define efficient strategy to mitigate this risk. Spray scrubbing tests are performed in the TOSQAN facility to evaluate the scavenging coefficients of aerosol particles whose size distribution is representative of the one released during the cutting of fuel debris. The main objective of this work is to determine the relevant characteristics of the spraying system that allow to achieve the best efficiency regarding Fukushima site implementation constraints. For safety issues, the scavenging coefficients will also allow to assess the remaining airborne aerosol fraction and provide input data for the design of filtration systems ensuring the containment of radioactive material. (authors)