EDITORIAL | Nuclear Debris Capture Ushers In Hardest Part of Decommissioning

このページを日本語で読む

Tokyo Electric Power Company (TEPCO) succeeded in its first experimental removal of one particle (0.7 grams) of nuclear debris fuel from Unit 2 of its disabled Fukushima Daiichi Nuclear Power Station.

This debris resulted from the nuclear accident caused by the massive tsunami that followed the Great East Japan Earthquake. Hot uranium fuel melted down along with the reactor core after the March 2011 tsunami and later solidified.

The process leading up to the extraction proved difficult, with numerous problems causing delays. However, for the first time, nuclear debris was actually removed from the bottom of a highly radioactive reactor containment vessel. That is definitely a step forward.

The Three-Phase Decommissioning Plan

The Japanese government and TEPCO structured the decommissioning plan into three stages over 40 years. It started from the time of the accident at the Fukushima Daiichi Power Station in 2011.

The first phase involved the purification of radioactively contaminated water. Next, in the second phase, the release of ALPs treated water into the ocean began. With this recent debris removal, we have finally reached the starting line for the third phase of the decommissioning process.

Implementation of the third stage is the crucial turning point in the decommissioning project. As long as debris remains at the bottom of the containment vessels, the groundwater flowing into units 1 to 3 will come into contact with it. As a consequence, new contaminated water will be produced. In turn, purification of that additional water will also be required.

The debris removed will be examined over several months at laboratories such as the Japan Atomic Energy Agency and others. They will determine the debris' properties, including the composition of radioactive elements. Then, the acquired data can be used as basic information for future full-scale removal work using robotic arms.

*A collection device grabs nuclear debris from inside Fukushima Daiichi Unit 2 on October 30. (provided by Tokyo Electric Power Company)*

Challenge of the Completion Target Date

However, a huge barrier remains before this third stage of decommissioning can be completed. Necessary tests of the removed debris must be overcome before proceeding further. In the end, a total of 880 tons of debris must be removed from the three reactor pressure vessels and containment vessels damaged by the core meltdown.

Since the removal will have to be done remotely, completing the project by the target date of 2051 is seen as quite a challenge. Furthermore, some observers say it is impossible to recover the entire amount. Such concerns expressed by outsiders deserve to be heard.

TEPCO and the Japanese government should continue with the current process, however, while also starting to consider an alternative Plan B. The scale of the Fukushima accident exceeds that of the Three Mile Island nuclear power plant disaster of 1979 in the United States. It is, in fact, uncharted territory even for the global nuclear engineering community.

What is more, there are currently no prospects for a disposal site for the recovered debris. In some cases, perhaps, the "sarcophagus" (shelter structure) method, adopted at the Chernobyl nuclear power station in Ukraine, should be included as an option.

Japan's effort to carry out safe and practical decommissioning work has the world's attention.

Author: Editorial Board, The Sankei Shimbun

このページを日本語で読む