As the Fukushima Daiichi nuclear power plant (NPP) accident illustrates, many challenges have to be faced in maintaining safety over the long term in a damaged NPP following a severe accident. These comprise maintaining and monitoring a stabilised and controlled state of the damaged plant; implementing provisions against further failures; evaluating the plant damaged state from a physical and radiological standpoint and ranking related risks; preparing and achieving fuel retrieval (either fuel assemblies stored in spent fuel pools or fuel debris from damaged reactors); and managing safely plant recovery and accident waste. All these actions are to be conducted protecting plant personnel from radiation exposure.
This status report reviews knowledge and experience gained through long-term management (LTM) of the Three Mile Island, Chernobyl and Fukushima Daiichi accidents, by identifying and ranking main issues and knowledge gaps. It also reviews the existing regulations and guidance, practices, technical bases and issues considered in member countries of the Nuclear Energy Agency regarding LTM of a severely damaged nuclear site.
Finally, it proposes recommendations and areas for future investigation to enhance LTM of an NPP as regards necessary knowledge and provisions development, particularly for the optimisation of management of contaminated cooling waters.