FUKUSHIMA – A subcontractor who was involved in building water storage tanks at the damaged Fukushima No. 1 nuclear plant said late last month that concerns about leaks emerged after workers were told to build the vessels as quickly as possible.
As feared, one of the tanks at the plant leaked 300 tons of highly radioactive water last month, Tokyo Electric Power Co. recently disclosed.
“We were required to build the tanks in quick succession,” the man said, recalling his experience building a group of tanks in the H4 area of the plant two years ago. “We were told to put priority on making the tanks, rather than quality control. There were fears that toxic water may leak.”
With some 400 tons of the radioactive coolant accumulating at the plant after the three reactor core meltdowns, workers rushed to slap together a 1,000-ton tank every three days, he said. The water, highly radioactive, was stored after being used to cool the melted fuel in the three reactors.
The tanks were flange-type units, which are less watertight than those with welded seams because they have many bolted parts that spring leaks.
The man said the workers were ordered by Tepco and its subcontractor to meet a deadline for the tanks because the amount of coolant water was rising and needed to be stored.
He said management of the tanks’ construction was poor, with necessary materials sometimes not delivered on time and rusty bolts found among the materials.
The tank that was confirmed to have leaked was originally constructed in the H1 area of the plant in June 2011, around three months after the Great East Japan Earthquake and tsunami helped trigger the three meltdowns. After terrain instability was detected in H1, the tank was dismantled and later reassembled in H4, he said.
He said he was involved in sealing the bolted parts and in waterproofing the insides of the tanks to prevent leaks. Currently, the work of waterproofing the insides is done by a company specialized in the field.
He also said the workers checked for cracks and leaks by injecting water.
“We never cut any corners in constructing the tanks and we used the latest technology,” he said. That said, the man noted the average life span of the water tanks is only five years.
“All of the tanks are makeshift. So more toxic water may leak as they deteriorate,” he said.
There are around 350 such water tanks at the plant.
Speaking on Tepco’s current efforts to deal with the huge volume of radioactive water accumulating daily, the man said, “Everyone is working so hard, but I don’t know whether this method is the right answer.”
On Monday, Shunichi Tanaka, chairman of the Nuclear Regulation Authority, said Tepco cannot store huge amounts of coolant water at the plant indefinitely.
“I’m afraid that it is unavoidable to dump or release the water into the sea” after it is purified to levels recognized as safe under international standards, Tanaka told a news conference.
Other officials said the government will present a set of emergency measures Tuesday to deal with the radioactive water problem. It’s not clear if the steps are also meant to curb the roughly 300 tons of highly radioactive groundwater that is believed flowing toward the Pacific Ocean daily, after running under the plant and possibly mixing with water in the basements of the stricken reactor buildings.
The measures to address the buildup of contaminated water, possibly including steps financed by the state budget, will be presented at a ministerial meeting headed by Prime Minister Shinzo Abe.