After finding tritium levels higher than the safety standard in well water at the crippled Fukushima No. 1 nuclear power plant, Tokyo Electric Power Co. withheld the information from the public for nearly three weeks.
The company on June 19 disclosed that 500,000 becquerels of tritium per liter of water, eight times the legal limit, were detected. It also said that 1,000 becquerels of strontium, 30 times the legal limit, were detected.
TEPCO began taking water samples from the well on the sea side of the turbine buildings for the No. 1 and No. 2 reactors on May 24.
Analysis results about tritium were conveyed to plant officials on May 31 and shared within the company on June 14.
A TEPCO official said the announcement was not made until June 19 because additional analyses were carried out as there had been problems in past measurements.
The official also said the company waited until June 18 to see analysis results about strontium, which were due that day.
But on June 14 the utility already began considering measures to prevent water from flowing into the sea under the ground.
The well, 27 meters from the sea, is close to a water intake system of the No. 2 reactor, an area from which highly radioactive water leaked into the sea in April 2011.
TEPCO suspects that the contaminated water spread underground at the time and later flowed into the well, one of the three it dug in November and December.
The company plans to dig four wells nearby to investigate the situation and also inject an agent into the ground along the coast to prevent contaminated water leaking into the sea.
The discovery of high levels of strontium and tritium is expected to delay TEPCO’s plan to pump groundwater at the plant and release it into the sea to slow an increase in radioactive water.
Kazunori Endo, of the Soma-Futaba fisheries cooperative in Fukushima Prefecture, said he was exasperated with the series of problems of contaminated water at the plant.
Members of his cooperative are opposed to the plan to dump groundwater into the sea, although TEPCO said the water contains lower levels of radioactivity than nearby rivers.
The opposition grew after June 3 when TEPCO said that radioactivity levels in the water were higher than initially reported due to a mistake in measurements.
“The problem is that (scandals) crop up one after another,” Endo said. He added that TEPCO must solve the latest problem before trying to release groundwater into the sea.
Members of his cooperative have been preparing to resume full-scale operations along the prefectural coast following the March 2011 nuclear disaster.
Akio Komori, a TEPCO managing executive officer, visited the Fukushima prefectural government office on June 19 to apologize for the high levels of strontium and tritium.
Tetsuya Hasegawa, head of the living environment department, asked Komori to identify the cause of high radioactivity levels, investigate the environmental impact and prevent the spread of contaminated water.
“It was regrettable that (radioactive water was found) at a time when we are calling for all possible measures,” he said.
Fukushima Governor Yuhei Sato told senior prefectural officials on June 19 to enhance monitoring of any effects of radioactivity in the ocean.
“We have repeatedly told TEPCO to take thorough precautions against contaminated water,” Sato said. “(The latest discovery) was regrettable.”
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