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Fukushima Nuclear Plant Report: The Long Fight Continues; Decommissioning Has Only Just Begun

At Fukushima Daiichi, visible progress in cleanup and access masks the immense unresolved burdens of contaminated water and nuclear fuel debris that will determine the fate of decommissioning.

福島原発ルポ：続く長き闘い緒に就いたばかりの廃炉

nippon.com · 13 November 2024 · read the original in Japanese →

Fukushima Nuclear Plant Report: The Long Fight Continues; Decommissioning Has Only Just Begun. Science. Society - English - Japanese - Simplified Chinese - Traditional Chinese - French - Spanish - Arabic - Russian. Reactor buildings changing form.

It was in late October 2024 that I reported from the Fukushima Daiichi Nuclear Power Station. At the time of the 2011 accident, I had overseen coverage of the disaster as the desk chief of a national newspaper’s reporting team, but this was my first time entering the site itself. Measures have been taken throughout the grounds to prevent radioactive material from scattering, and the “red zones” and “yellow zones,” where radiation levels are high and full-face masks and protective suits covering the entire body are required, are now limited to certain areas such as the reactor buildings. Most of the site is a “green zone,” where protective clothing is unnecessary; during the reporting trip, too, our gear was light: helmets, masks, cotton work gloves, and the like.

According to Tokyo Electric Power Company, as of the end of August this fiscal year, 7,594 outside visitors, excluding media, had inspected the plant. In fiscal 2023, the number was 18,516, roughly twenty times the 913 visitors recorded in fiscal 2011. Although visits declined for a time during the COVID-19 pandemic, they are once again on the rise. Immediately after the accident, TEPCO restricted entry because of the dangers posed by high radiation levels at the site and scattered debris, but it has expanded access for inspections in order to give the public a broader understanding of the progress of work, including the release of treated water into the sea. There is no record of the number of media visitors, but a TEPCO official says, “Recently the number of reporters, including overseas media, has been increasing.”

Standing on a rise from which the reactor buildings of Units 1 through 4 can be seen, one can tell at a glance that progress differs from unit to unit. Unit 1, its steel frame still exposed by the hydrogen explosion, conveys the ferocity of the accident. In the spent fuel pool inside, 392 nuclear fuel assemblies still remain, but debris from the building and large cranes have been left in place, obstructing the work of removal. In a separate area, assembly is underway on a large cover that will enclose the building to prevent radioactive material from scattering during the work.

Unit 2, which suffered a meltdown but escaped explosion, is surrounded by steel structural members for the work now being carried out. Unit 3 has an especially conspicuous appearance. A long, narrow domed roof has been installed on top to remove spent fuel, and it gleams with a dull silver sheen. All 566 fuel assemblies have already been removed. Unit 4, which was undergoing regular inspection at the time of the accident, avoided meltdown, but hydrogen flowed into it through piping from Unit 3 and caused an explosion. A structure installed to remove the 1,535 assemblies that had been in the fuel pool covers the building, making its overall form hard to discern.

Directly beneath the buildings, radiation levels rise.建屋の直下、高まる放射線量

From the window of the minibus moving across the vast site, one notices rows upon rows of tanks storing treated water from which radioactive materials have been removed, clusters of containers holding waste, and large power-generation turbines once used here, left rusting in various places. Most of the debris has been cleared away, but here and there remain objects preserved as traces of the accident, such as a water storage tank badly dented by the tsunami. On a deck overlooking Units 5 and 6, part of the “shield machine” used to excavate the tunnel for discharging treated water into the sea has been preserved as a memorial object.

We get off the bus and walk around Unit 4 from the seaward side to the landward side. As we proceed, looking up at the buildings and structures we had seen from the rise, the severed cross-section of a huge duct reveals itself in a pitiful state. It once connected Units 1 through 4 to the exhaust stack, but it was cut away because it obstructed decommissioning work. On the structure of Unit 3, faint traces remain of the green agent that was sprayed on to keep adhering radioactive material from scattering, a sign left from the immediate aftermath of the accident.

As we continue north from Unit 3 toward the base of Unit 2, the radiation level rises. I find myself worrying about the reading on the personal dosimeter tucked into the chest pocket of the vest I am wearing. At Unit 2, work is underway to remove “nuclear fuel debris,” the mixture of nuclear fuel that melted and fell during the accident with surrounding structural materials; near the removal exit, workers clad in protective suits can be seen.

To return to the seaward side, we pass between Units 2 and 3. The number on the ambient dose meter climbs, reaching 240 microsieverts per hour. Before there is time to study the extent of the damage to the buildings, the official guiding us urges us on and we break into a trot. “A few years ago it was over 300 microsieverts per hour,” the official says, but even now the effects of radiation are by no means something that can be ignored.

Once we emerge on the seaward side, a seawall completed in March this year stretches roughly one kilometer from north to south as a tsunami countermeasure. A wall 13.5 to 16 meters high, built from assembled concrete components, protects Units 1 through 4 from tsunami waves. It is designed to withstand even a Japan Trench tsunami, whose occurrence is assessed as imminent, and TEPCO explains that “even in the unlikely event of such a disaster, it can reduce the risk that contaminated water will flow outside the site and pollute the environment.”

The double burden of “water” and debris.「水」とデブリの「二重苦」

On November 7, TEPCO completed the removal from Unit 2’s primary containment vessel of a piece of debris about five millimeters in size, grasped with a specialized device. The operation will be used in considering methods for full-scale debris removal. A total of 880 tons of debris is estimated to exist inside the containment vessels of Units 1 through 3, and this has become “the greatest obstacle to decommissioning.” Takahiro Kimoto, deputy director of the Decommissioning Communication Center, says, “Thirteen and a half years after the accident, we have finally taken a step toward decommissioning. But the work is still only at the stage where it has just begun.”

Although steady progress is being made in various areas, there is still no prospect of a fundamental solution to contaminated water, one of the major obstacles to decommissioning. Groundwater and rainwater flowing into the reactor buildings amount to 60 tons per day. Water injection to cool the reactors also continues, and 80 tons of contaminated water are generated every day, on average in fiscal 2023.

TEPCO treats the contaminated water using the Advanced Liquid Processing System, or ALPS, and other equipment, and continues to store it in tanks on the site. It began releasing treated water into the sea in August 2023, and by November 5, 2024, had carried out ten releases totaling 78,285 tons. The total amount of tritium, a radioactive substance that cannot be removed because its chemical properties resemble those of water, came to about 14.8 trillion becquerels, but TEPCO says monitoring of the surrounding sea area has found no abnormalities.

Yet the release into the sea of treated water stored on the site is expected to take another thirty years, and it is difficult to reduce completely to zero the generation of contaminated water caused by the inflow of groundwater and rainwater. If the rows of tanks, multiplied by the struggle to deal with “water,” do not decrease, the overall decommissioning plan will be affected, including the installation of storage facilities for debris whose removal is expected to advance in the years ahead.

Water and debris. How is the “double burden” of decommissioning work to be overcome? Deputy Director Kimoto says, “The challenge is how to curb the amount of contaminated water. If we can keep it from increasing and hold it stable, we will also be able to see a path for the decommissioning plan.”

Banner photo: Unit 1 of the Fukushima Daiichi Nuclear Power Station, its steel frame left exposed after the hydrogen explosion, in the foreground. The cylindrical dome visible behind it is Unit 3. Photographed on October 21, 2024, at TEPCO’s Fukushima Daiichi Nuclear Power Station. Photo by Hashino Yukinori, nippon.com editorial department.