Study on strategy construction for dismantling and radioactive waste management at Fukushima Daiichi Nuclear Power Station

Abstract Upon the commencement of the phase-three decommissioning of Fukushima Daiichi Nuclear Power Station (FDNPS), strategy construction is a necessary step for effective radioactive waste management as well as safe project implementation. In this study, we evaluate safety and environmental detriment (SED) score of radioactive materials in the expected major stages of the project for the strategy construction. Following assumptions are made for the evaluation. The phase-three decommissioning, which is defined as active decommissioning, proceeds in the order of fuel debris retrieval, core component removal, piping & equipment dismantlement, and building structures demolition. The radioactive waste management proceeds in the order of pre-treatment, treatment, and conditioning. SED scores are calculated for each of the four groups of objects (object-base) and their total (plant-base) at a specific point of time during the active decommissioning, considering the progress of the radioactive waste management. The calculation results indicate following suggestions for strategy construction. First, treatment and conditioning of fuel debris and core components make a large contribution for reducing plant-base SED score during the active decommissioning. Second, nearly 90% of achievable amount of reduction in plantbase SED score could be realized without piping & equipment dismantlement and building structures demolition. Third, since plant-base SED score could be hugely influenced by physical form of fuel debris, it may be necessary to consider work plan from the viewpoint of cutting and containing methods. Those perspectives would be useful input to construct active decommissioning strategies together with project management parameters such as staffing, technical capability, and financial readiness.