information about Fukushima published in English in Japanese media info publiée en anglais dans la presse japonaise
20 Février 2014
February 20, 2014
A warning alarm was ignored and 100 tons of highly radioactive water overflowed from a storage tank and seeped into the ground at the Fukushima No. 1 nuclear plant, the plant operator said Feb. 20.
The water did not reach the ocean, Tokyo Electric Power Co. said.
According to TEPCO, a worker on patrol spotted the water leaking from a storage tank in the H6 area at 11:25 p.m. on Feb. 19.
The area is surrounded by a barrier, but the leaking water entered a gutter for rainwater at the tank’s top plate and flowed outside the barrier, creating pools covering 870 square meters, TEPCO officials said.
Workers dismissed an alarm that sounded shortly past 2 p.m. on Feb. 19 that indicated dangerously high water levels in the tank, TEPCO said.
They believed that water levels could not be rising because no radioactive water was being transferred into the tank, and attributed the alarm to faulty instruments, such as the water level gauges, the utility said.
They did not check on the situation.
But they later concluded that highly radioactive water was leaking from the tank after detecting beta-ray levels of 50 millisieverts per hour and gamma-ray levels of 0.15 millisievert per hour from the water that had escaped.
They also found 230 million becquerels of beta-ray sources, including radioactive strontium, per liter of water in the rain gutter, TEPCO said.
The leak was apparently caused by open valves along a radioactive water conduit leading into the storage tank, a flange type that uses bolts to fasten steel panels. TEPCO officials said radioactive water likely entered the tank via the valves, filled it beyond capacity and escaped through openings in its top plate.
Workers closed the valves and transferred radioactive water to other tanks to lower the water level in the tank. They confirmed the leak stopped at 5:40 a.m. on Feb. 20.
TEPCO officials said workers were collecting the radioactive water that had escaped, adding that they will investigate why the valves were open.
http://mainichi.jp/english/english/newsselect/news/20140220p2g00m0dm081000c.html
TOKYO (Kyodo) -- Roughly 100 tons of highly radioactive water leaked from one of the huge tanks at the crippled Fukushima Daiichi nuclear complex, plant operator Tokyo Electric Power Co. said Thursday, admitting it could be the worst leakage from such containers since August.
Steps have been taken to stop the leakage of the water, which contains 230 million becquerels per liter of strontium and other beta ray-emitting radioactive substances. The utility believes the liquid has not flowed into the adjacent sea as there is no drainage nearby.
According to TEPCO, a worker on patrol noticed water spilling from the tank's lid area at 11:25 p.m. Wednesday. The water, by passing through a rainwater pipe, escaped outside a concrete barrier intended to block liquid from spreading outside when tanks leak.
TEPCO spokesman Masayuki Ono told a press conference the company suspects that radioactive water was mistakenly directed to the tank because valves that should have been closed were open, causing the container to overflow.
Among three valves, one appeared to have been closed, but may have malfunctioned, while two others had been open.
After closing the two valves, TEPCO said it confirmed the leak stopped at 5:40 a.m. Thursday.
More than nine hours before the leak was recognized, an alarm indicating a rise in the tank's water surface level was issued.
But workers thought the device was out of order and also could not find leaks when they patrolled the area at 3 p.m. and 4 p.m. Wednesday.
Ono said the utility may consider clarifying how valves should be operated and improving the design of rainwater pipes, which are attached to tanks as a measure to prevent rainwater from accumulating inside the concrete barriers surrounding clusters of tanks.
He also said the company must determine if and when the valve and a water level indicator malfunctioned.
The latest incident is another sign TEPCO is struggling to manage a massive amount of radioactive water generated in the process of cooling three reactors that have suffered meltdowns during the nuclear crisis triggered in March 2011.
The water passes through a facility that can reduce cesium, but it contains high concentrations of radioactive substances such as strontium-90. Strontium tends to accumulate in bones and is thought to cause bone cancer and leukemia.
In August last year, TEPCO said 300 tons of highly radioactive water escaped from a different tank, some of which is also believed to have flowed into the ocean.
TEPCO has since been stepping up efforts to detect leak incidents as quickly as possible such as by reinforcing patrolling activities and installing water-level indicators to all of the tanks made of steel sheets joined by bolts.
February 20, 2014(Mainichi Japan)
Staff Writer
Tokyo Electric Power Co. said Thursday about 100 tons of highly radioactive water overflowed and spilled from a tank at the Fukushima No. 1 plant.
The utility said it believes that the escaped water did not reach the ocean, as there was no drainage ditch that connects to the sea near the leaked area around the tank, which is in an area called H6.
At the crippled Fukushima No. 1 site, Tepco removes cesium from tainted water that flows into the basements of the crippled reactor turbine buildings daily. The water is put into storage tanks.
Tepco said the water was supposed to go to tanks placed at the E area, which is west of H6, but it went to the tank that was already storing water at H6 and overflowed.
According to the utility,two of the three valves of the pipe that control the water flow to the H6 area were open. Yet even if only the third valve was closed, the water should not have flowed, Tepco said, adding that the valve may be broken. But Tepco also admitted the three valves should have all been closed and is still not sure why two were left open.
While cesium was removed from the leaked water, it contains other radioactive materials, like strontium. Tepco said the level of those that emit beta rays was 230 million becquerels per liter.
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