An International Atomic Energy Agency (IAEA) said Tuesday that the agency had completed the fourth review mission of Japan's efforts towards the decommissioning of the Fukushima Daiichi Nuclear Power Station (NPS) in Japan, noting several key improvements had created stable conditions ad the devastated facility.

The International Peer Review of Japan's Mid-and-Long-Term Roadmap Towards the Decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Station took place from 5 to 13 November 2018, the agency said.

The team of experts who reviewed the site said Japan has made "significant progress" since March 2011, when a tsunami event, triggered by a massive earthquake, took out the backup systems at the plant that were keeping the reactors cool. The team said progress at the plant meant the conditions on site were "advancing from an emergency situation towards a stable situation now."

Now past the point of dealing with emergencies as needed, conditions had progressed to the point that Japan can "focus more resources on detailed planning and implementation of decommissioning activities of the whole site, with considerations extended up to completion," the IAEA team reported.

"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 mission examined a wide variety 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 spent fuel assemblies and retrieval of fuel debris, management of radioactive waste, and institutional and organizational matters.

In a Preliminary Summary Report on the visit, delivered to authorities in Japan, the team noted improvements since 2015 that included: The repair of subdrains and construction of the frozen soil wall around reactor Units 1-4, which have reduced groundwater ingress into the reactor buildings; the construction of storage and processing facilities for the safe management of solid radioactive wastes; improved site working conditions including a reduced need for full protective gear, and real-time radiation monitoring easily accessed by the workforce; and progress towards the removal of spent fuel from Units 1-3 as well as remote investigations of fuel debris by robots.

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 team said the Government of Japan should urgently decide on a disposition path for treated water containing tritium and other residual radionuclides.

The treated water is still accumulating in tanks on site and is expected to reach the currently planned tank capacity within three to four years. The water may require further treatment to reduce radionuclides to authorized levels before any of the five disposition paths considered by the Government (ground injection, controlled discharge into the sea, discharge as steam, discharge as hydrogen, and solidification for underground burial) can be implemented. A decision on the disposition path is needed soon to ensure a safe and sustainable decommissioning and can only be implemented after a regulatory review, with the support of a robust environmental monitoring program and a communication plan.

In addition, the team provided advice in areas where practices could be enhanced, including: further further strengthening a “project oriented” approach, including the provision of resources for comprehensive and integrated planning for the completion of decommissioning. In addition, TEPCO and NDF should consider more detailed, long-term planning for managing wastes arising from the decommissioning project and, considering the significant challenges and length of the project, sustained stakeholder interactions, appropriate knowledge management systems and broad international cooperation should be ensured.

“Japan has laid the groundwork to effectively address the next steps in risk reduction at Fukushima Daiichi,” Xerri said. “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 comprised 13 senior experts, including nine from the IAEA and four others from Indonesia, the Russian Federation, the United Kingdom and the United States of America. It plans to issue its final report to the government of Japan by the end of January.