AEROSOL MITIGATION MEANS FOR FUKUSHIMA DAIICHI FUEL DEBRIS REMOVAL

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. Such information are also necessary to define an efficient strategy to mitigate this risk. Various mitigation means could be implemented during the decommissioning of Fukushima Daiichi damaged reactors, depending on the operations such as cutting of fuel debris or metallic structures or investigation in Primary Containment Vessel (PCV) by robots. It is also important to consider accidental scenarios such as earthquake event, to define countermeasures limiting the consequence in terms of safety and radioprotection. We propose to study various mitigation means such as the spray scrubbing technology used to collect airborne particles and therefore limit their dispersion during the cutting operations. Resuspension of deposited particles may also occur during the decommissioning operations due to various type of stress, such as aeraulic, mechanical, vibrational and also during underwater operations. To address these particle resuspension issues, another mitigation means made by coating of resins is introduced.