The Maze of Decommissioning: Searching for the Endpoints of Fukushima Daiichi Nuclear Power Plant, 2018-2019."

The Maze of Decommissioning: Searching for the Endpoints of Fukushima Daiichi Nuclear Power Plant, 2018-2019."

Between 2018 and 2019, less than a decade after the Fukushima Daiichi nuclear accident, the term "decommissioning" was used symbolically in the government's and TEPCO's explanations. The chaotic period immediately after the disaster had passed, and the site appeared outwardly tidy, with debris removed and radiation levels reduced. However, behind this orderly landscape, the exact location of the fuel debris could not even be determined, and the phrase "steady progress" was repeated without concrete measures for removing the debris being decided upon. Behind this was a complex intertwining of technical and political issues at the Fukushima Daiichi Nuclear Power Plant at the time.

After the accident at the Fukushima Daiichi Nuclear Power Plant, the decommissioning of the plant was not merely a physical removal operation, but one that required advanced technology and deep expertise. Several years after the accident, although progress had been made in reducing radiation levels and removing debris, technical progress in accurately identifying the location and condition of fuel debris in the accident reactor had been slow. At this time, the Fukushima Daiichi Nuclear Power Plant urgently needed to develop robotics and tele-operation technologies, and in particular, unmanned aircraft and robots were introduced to safely work in the high-radiation zone. For example, the "Trial Robot" introduced by TEPCO was developed to remove fuel debris in a high-radiation environment and to check its internal condition. However, it was difficult to completely locate the exact position of the fuel debris, and specific measures on how to remove it were not determined. Furthe
rmore, there were limited techniques to minimize the effects of radiation and ensure the safety of workers, and the work went back and forth.

At the time, TEPCO and the government had a roadmap of "up to 40 years to complete decommissioning," but this figure was only a "rough estimate," and in reality the specific process to complete decommissioning and the definition of termination remained unclear. This ambiguity drew criticism from experts and Diet members. A major problem in the progress of decommissioning was the removal of fuel debris and the associated technical challenges. Fuel debris is high-temperature material that solidified after meltdown in the reactor, and special equipment and techniques were needed to remove it. In particular, the removal of fuel from the spent fuel pool and the removal of fuel debris from the reactor pressure vessel were extremely difficult because they were performed under extremely high radiation levels and high temperature environments.

Furthermore, the advancement of decommissioning technology at nuclear power plants was an important factor in international competition, and comparisons were being made with decommissioning technology in other countries. In particular, the decommissioning support technology developed by Siemens of the U.S. and the know-how of AREVA of France in decommissioning high-temperature gas-cooled reactors were attracting attention, but the application of these technologies was limited for decommissioning accident reactors such as the Fukushima Daiichi Nuclear Power Plant, and original technological development was required.

In the political arena, public opinion was sharply divided on the issue of restarting and decommissioning nuclear power plants. While some reactors, such as Kawauchi and Takahama, were being restarted, others were being decommissioned around the country, and the question of whether to restart or decommission them was influencing the elections for the heads of local governments. However, the policy question of what "decommissioning" meant--whether the reactors would be cleared or whether they would be left in place under safety management--had not yet been settled. Politically, there was a mixture of hope and anxiety about the progress of the decommissioning plan. While the maximum time frame to complete decommissioning was set at 40 years, the debate over nuclear policy continued, and the issue of restarting reactors was also involved. 2019 saw the announcement of a decommissioning plan for the Fukushima Daini Nuclear Power Plant, with a time frame of "44 years," which was lo
nger than that of the accident reactor, further complicating the issue. This further complicated the issue.