Japan has made significant progress in decommissioning the damaged Fukushima Daiichi nuclear power plant, but many challenges remain, a mission by the International Atomic Energy Agency (IAEA) has concluded.

Members of the mission team at the Fukushima Daiichi plant (Image: J Donovan/IAEA)

An IAEA team of experts yesterday completed the fourth review mission of Japan's efforts towards the decommissioning of Tokyo Electric Power Company's (Tepco's) damaged Fukushima Daiichi nuclear power plant, which began on 5 November. The team comprised 13 senior experts, including nine from the IAEA and four others from Indonesia, Russia, the UK and the USA.

The mission, which followed two previous reviews in 2013 and one in 2015, examined a wide range of issues at Fukushima Daiichi. The team reviewed progress since the 2015 mission, the current situation on site and future plans in areas such as water management, removal of used fuel assemblies and retrieval of fuel debris, management of radioactive waste, and institutional and organisational matters.

The team concluded Japan has "made significant progress since the accident in March 2011, advancing from an emergency situation towards a stable situation now". This achievement, it said, "will now allow Japan to focus more resources on detailed planning and implementation of decommissioning activities of the whole site, with considerations extended up to completion."

In its preliminary summary report, the team acknowledged a number of accomplishments since the 2015 mission. These include that groundwater ingress into the reactor buildings of units 1-4 has been reduced through the repair of subdrains and construction of a frozen soil wall around them. In addition, storage and processing facilities have been constructed for the management of solid radioactive wastes. The team noted improved site working conditions, including a reduced need for full protective gear. It also said there has been progress towards the removal of used fuel from units 1-3, as well as remote investigations of fuel debris using robots.

"Given the severity of the challenges faced from the outset of the accident, one can only be impressed by the dedication and the achievements of the people involved," said team leader Christophe Xerri, Director of the IAEA's Division of Nuclear Fuel Cycle and Waste Technology. "Despite these achievements, many challenges remain to be tackled in the decommissioning process, and ensuring safety in this complex situation requires sustained daily attention."

The team encouraged Japan to continue carrying out and enhancing its strategy for safely decommissioning and managing radioactive waste, and identified water management as critical to the sustainability of the overall project. The Japanese government, it said, should "urgently decide on a disposition path for treated water containing tritium and other residual radionuclides". This water is accumulating in on-site tanks, but the storage capacity is expected to be reached within three to four years.

The mission team also made suggestions where practices could be enhanced. These included the further strengthening by the government of a "project oriented" approach, including the provision of resources for comprehensive and integrated planning for the completion of decommissioning. It also suggested Tepco and the Nuclear Damage Compensation & Decommissioning Facilitation Corporation - the national entity responsible for the decommissioning strategy for Fukushima Daiichi - should consider more detailed, long-term planning for wastes generated through the decommissioning activities.

Xerri said, "Japan has laid the groundwork to effectively address the next steps in risk reduction at Fukushima Daiichi. While the international community will learn a lot from these efforts, Japan too can benefit from international experience and cooperation in support of its work towards decommissioning."

The team plans to deliver its final report to the Japanese government by the end of January.

Researched and written by World Nuclear News

Date: Wednesday, 14 November 2018
Original article: world-nuclear-news.org/Articles/IAEA-reviews-Fukushima-Daiichi-clean-up-work