The International Atomic Energy Agency (IAEA) on 31 January published the final report by an IAEA expert team that reviewed Japan's efforts to plan and implement the decommissioning of the Fukushima Daiichi nuclear powewr plant.
The report was based on findings from a 5-13 November 2018 mission by a 13-member team. The mission was the IAEA's fourth “International Peer Review of Japan’s Mid-and-Long-Term Roadmap towards the Decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Station”. Two previous reviews were carried out in 2013 and one in 2015.
The team concluded that addressing the situation of the damaged plants of Fukushima Daiichi and moving towards decommissioning while ensuring population and worker safety “remained a very challenging task, requiring resources, commitment, and innovation to tackle a unique situation” but that “significant progress has already been accomplished”. This should allow the focus of more resources for detailed planning and implementation of the decommissioning project of the whole site with considerations extended up to the completion of the decommissioning”.
The organisation put in place by the Japanese government, with clarified roles for the main actors “allows for more effective planning and implementation of the radioactive waste management and decommissioning” but “strong collaborative relationships among these organisations should be maintained”.
The team said daily activities at the site were “well managed, for the areas
reviewed” with “many improvements” since the previous mission in 2015. In particulary it noted improvements pertaining to water management (implementation of the multi-layered approach including sub-drain and recently the completion of the “frozen soil wall”), and solid waste management (construction of storage and volume reduction facilities)”. The team also noted improvement of working conditions at the site.
The team outlined the progress in the removal of spent fuel from Fukushima Daiichi units 1, 2 and 3, and “noted with interest the investigations made in the reactors and the research and development effort which support this objective”. However, the IAEA “continues to identify water management as critical to the sustainability of decommissioning activities, in particular the resolution of the disposition
path for the ALPS (Advanced Liquid Processing System) treated water containing tritium and other radionuclides in tanks”. The volume of ALPS treated water is expected to reach the planned tank capacity of 1.37 million cubic metres within the coming three to four years. However, the teamed noted that given current site facility plan for space allocations, and that further treatment and control of the stored water before disposition would be needed for implementation of any of the five solutions considered by the Japanese government, “a decision on the disposition path should be taken urgently engaging all stakeholders”.
Considering the challenges ahead, the team “encourages Japan to further strengthen programme and project management and related organisational structure for comprehensive and integrated planning for the completion of the site decommissioning”. While fuel debris retrieval is “one of the most important and challenging issues”, planning should also address sustainability and long-term aspects such as radioactive waste management, including the waste streams which will come from decommissioning.
Meanwhile, on 28 January, Toshiba Corp unveiled a remote-controlled robot with tongs that will be used in February to investigate the status of deposits at the bottom of the pedestal area interior of the primary containment vessel (PVC) of Fukushima-Daiichi 2.
The robot, designed and built by Toshiba’s Energy Systems & Solutions division, is 30cm long and 10cm wide and weighs approximately 1kg. It is fitted with a camera, external LED Lighting, a pan-tilt mechanism, a radiation dosimeter and a thermometer. In an advance on previous robots Toshiba has developed for Fukushima, it is equipped with a finger mechanism for exploring the nature of deposits.
In February 2017 robotic investigation by plant operator Tokyo Electric Power Company (Tepco) found that part of the grating of the platform inside the unit 2PCV of had dropped. Further investigation in January 2018 showed deposits at the bottom of the PCV. The new robot will investigate the nature and condition of these deposits.
Toshiba said it plans to use the new device to touch and grip the deposits with the tongs, which can hold a lump up to 8cm wide weighing up 2kg.
Tepco and government officials hope to devise methods for removing the melted fuel from all three damaged reactors later this year with the aim of beginning removal in 2021.
Photo: Toshiba has shipped a new robot to Fukushima. It will be used in February to investigate the physical conditions of deposits in Fukushima Daiichi unit 2 (Credit: Toshiba)