Posted: 23rd September 2020
September 22, 2020 (Mainichi Japan)
It has been some 9 1/2 years since the triple-meltdown disaster at the Fukushima Daiichi Nuclear Power Station in northeast Japan, and in early September I visited the plant to get a close-up look at the reactor buildings and find out how much progress is being made in dismantling them.
The trip began aboard a microbus, which stopped on an inland promontory running north to south at an elevation of 33.5 meters above sea level. Getting off the bus, I looked east, over the Pacific Ocean. And then I saw them, just 100 meters away or so: the buildings containing the plant’s No. 1 to 4 reactors.
When a tsunami triggered by the March 11, 2011 Great East Japan Earthquake slammed into the coastal facility, reactors 1 to 3 were online, while No. 4 was shut down for a regular inspection. There were core meltdowns in all three of the active reactors, with the fuel mixing with material from the surrounding structure as it melted and turned into “fuel debris.” Later, the No. 4 reactor building, connected to the No. 3 building by plumbing, was blown apart by a hydrogen explosion.
To complicate matters further, the reactor buildings had fuel storage pools each containing between 392 and 1,534 nuclear fuel rods. However, the plant workers managed to keep the rods cool, averting a major secondary disaster.
On my visit, the No. 3 reactor building is encased in what looks like a Baumkuchen layer cake stood upright. Inside, operations are underway to remove the fuel rods from the 12-meter-deep storage pool.
“There’s a newly installed crane in there to take the fuel out,” said our guide Masayuki Ueda, who is a manager at the Fukushima Daiichi decommissioning unit of the plant’s operator, Tokyo Electric Power Company Holdings (TEPCO).
The hydrogen explosion choked the pool and surrounding area with debris, including fragments of the roof and bits of nearby machinery. Even after the clearing of this debris, equipment and other problems delayed the fuel removal operation by more than four years. The process finally got underway in April 2019. The special crane lifts the some 300-kilogram rods out of the pool one at a time, and they are then taken to a pool in a separate building. Of the 566 rods, 366 had been removed as of Sept. 11, 2020. Due to the high radiation in the building itself, the crane is operated remotely from a control facility about 500 meters away.
The hardest part of the task is yet to come; the handles on 16 of the rods were warped by falling debris, and can’t be extracted by the crane as they are. TEPCO is apparently working on a “grabbing tool” for the crane to lift out the damaged rods, among other methods, in hopes to finish the removal project by March 2021.
We get back on the microbus and head down the hill to a spot where we can look up at the No. 4 reactor building. Here, too, we can see the machinery for the so-called underground ice wall surrounding the No. 1-4 reactors.
Groundwater from the mountains flows relentlessly beneath the power station. The walls in the basement levels of the reactor buildings were cracked in the March 2011 quake, letting in the groundwater and rainwater that has come into contact with the nuclear fuel debris, contaminating it. The “ice wall,” which TEPCO began making in May 2013, is TEPCO’s attempt to control the problem.
The wall is made up of some 1,500 pipes sunk 30 meters into the ground, creating a subterranean perimeter about 1.5 kilometers long around the reactor buildings. Liquid cooled to minus 30 degrees Celsius is then run through the pipes, freezing the soil around them. The Japanese treasury spent about 34.5 billion yen (about $330.7 million) to make the wall, and the electricity and other maintenance to keep it going costs hundreds of millions of yen per year. These latter outlays are passed on to consumers in their power bills.
Previously, the stricken plant produced up to 600 metric tons of contaminated water per day. However, thanks to pumping up groundwater on the landward side of the plant and other measures, that was down to 160 tons per day in April through July this year. Under the plant decommissioning plan, TEPCO and the Japanese government intend to reduce that to 150 tons per day by the end of 2020, and 100 tons by 2025. TEPCO has said that, with work on new roofs over the reactor buildings proceeding, it believes it can meet the 150 ton target this year.
Meanwhile, with radiation levels around the reactor buildings gradually declining, the Nuclear Regulation Authority (NRA) believes it is the moment to consider going into the basement levels to patch the cracks in the walls. NRA Chairman Toyoshi Fuketa has said that “it’s about time to start discussing when to halt” the ice wall operation.
There are experts who doubt the efficacy of the ice wall. In 2018, TEPCO estimated the wall alone was preventing 95 tons of contaminated water from being generated per day. However, Hideyuki Ban, co-director of the nonprofit organization Citizens’ Nuclear Information Center, told the Mainichi Shimbun, “There needs to be an inquiry into whether the ice wall was ever really necessary.”
Parts of the Fukushima Daiichi decommissioning plan have been delayed repeatedly since its release in December 2011. At that time, the plan stated it would take 30-40 years to complete the project. However, after seeing the power station up close, I find it hard to imagine this.
(Japanese original by Suzuko Araki, Science and Environment News Department)