Key to dismantling nuclear reactors: Waste disposal

Key to dismantling nuclear reactors: Waste disposal
Near Chubu Electric Power Co.’s buildings for nuclear reactor Nos. 1 and 2, work is underway to dismantle such equipment as transformers.

A decision was made in March to decommission all five aging nuclear reactors in the nation, including the Nos. 1 and 2 reactors at Kansai Electric Power Co.'s Mihama plant in Fukui Prefecture. The time has come for many of Japan's nuclear plants to be decommissioned.

Using the ongoing dismantling of the Nos. 1 and 2 reactors at Chubu Electric Power Co.'s Hamaoka plant as a starting point, Eiji Noyori reports on the circumstances and challenges surrounding the reactor decommissioning process, which lasts nearly 30 years.

When I visited the Hamaoka nuclear power plant last month, I saw red and white tape stretched across transformers and other parts of the Nos. 1 and 2 reactors, indicating plans for them to be taken apart. There were only traces left of tanks that had once held such material as chemicals and crude oil.

Since 2009, decommissioning work has included processing nonradioactive building material surrounding structures such as those that house reactors and turbines.

Starting this fiscal year, preparations have been under way to dismantle equipment inside buildings such as turbines and condensers. They will then be removed from the buildings over an approximately 15-year period.

Work to dismantle the reactor body is scheduled to begin in fiscal 2023, with the decommissioning process planned for completion in fiscal 2036.

Reducing radioactivity

At this point, a particularly vital procedure is reducing low-level radioactive waste (See below). The surfaces of reactor components, for example, are tainted with radioactive material.

Components that were originally not radioactive were also contaminated after being exposed to neutrons.

Reducing radioactive levels and the amounts of such low-level radioactive material would make them easier to handle and open up the possibility of reusing them.

"It's possible to greatly reduce radioactive levels and amounts of waste through a number of methods, including stripping their surfaces of radioactive substances and decontaminating them using chemicals," said Yoshihiro Ichikawa, decommissioning supervisor at the Hamaoka plant.

Initial projections indicated about 14,000 tons of low-level radioactive waste around the nuclear plant, which the clean-up process is aiming to reduce to about 4,000 tons. Radioactive amounts found on parts such as the plumbing can also feasibly be brought down to about one-hundredth of their original levels.

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