Yet another Fukushima-related scandal has broken out as Japan’s nuclear regulator criticised the operator of the cripple plant for incorrectly measuring radiation levels in contaminated groundwater at the site. Almost three years since the reactor meltdowns at the Fukushima Daiichi station, Tokyo Electric Power Co (Tepco) still lacks basic understanding of measuring and handling radiation, Nuclear Regulation Authority (NRA) Chairman Shunichi Tanaka said on Wednesday. The utility has been widely criticised for an inept response to the March 2011 disaster.
Tepco said last week that groundwater drawn from a monitoring well last July contained a record 5 million becquerels per litre of dangerous radioactive strontium-90 – more than five times the total beta radiation reading of 900,000 becquerels per litre recorded in the well, which is around 25 metres from the ocean.
Tepco said there was a calibration mistake with one machine measuring strontium levels of well water at the plant, and it had also found an error with devices that decipher all-beta radiation.
“Something like this cannot happen … This (data) is what becomes the basis of various decisions, so they must do their utmost to avoid mistakes in measuring radiation,” Tanaka told reporters, though he added the mistake did not pose a serious safety risk at the plant.
The legal limit for releasing strontium 90, which has a half life of around 29 years, into the sea is 30 becquerels per litre.
A Tepco spokesman said the utility will re-check all-beta radiation readings of groundwater in light of the record strontium levels.
Last year, radiation leaks, power outages and other mishaps sparked international concern and prompted Japan’s government to step in with more funds and support. As part of a turnaround plan approved by the government last month, Tepco hopes to re-start its biggest nuclear station, Kashiwazaki Kariwa, this summer.
Tepco in November began the hazardous process of removing hundreds of brittle spent fuel rods from the damaged No. 4 reactor building at Fukushima. It said last week it had removed about 9 percent of more than 1,500 unused and spent fuel assemblies in the reactor’s storage pool.
Tokyo Electric Power Co. did not inform the public until recently that enormously high levels of radiation were discovered in groundwater collected at the Fukushima-1 nuclear plant last July. The company knew those figures that month, according to sources.
Tepco released the data on 6 February showing that the groundwater contained a record 5mln becquerels per litre of radioactive strontium-90. Initially, Tepco said that it had detected 900,000 becquerels of beta ray emitting radioactive materials, including strontium-90.
The company’s explanation for the huge difference in the two measurements was that the method of measuring beta ray-emitting materials could show lower-than-actual levels.
Because Tepco has repeatedly changed its explanations, the secretariat of the Nuclear Regulation Authority has asked it for more detailed information.
Previous reports said that Tepco belatedly revealed last year that about 300 tons of groundwater flowed into the sea daily, after mixing with radioactive water used to cool the plant’s three stricken reactors.
Eight more children in Fukushima have developed thyroid gland cancer in addition to previous 75 suspected cases discovered during the prefecture-led checkups, a local panel of experts said on Friday. The screening of Fukushima residents who were 18 or younger at the time of the nuclear disaster kicked off in October 2011 – half a year after a tsunami triggered by an earthquake hit Japan’s coast. About 270,000 teenagers have been examined since.
Many people are seriously concerned that a continuous increase in the number of thyroid cancer cases was caused by the exposure to radiation from the crippled nuclear plant, while the panel of doctors and other medical experts say they are not sure there is a link to the meltdown calamity.
Meanwhile, a new leakage of highly radioactive water from one of the damaged reactors has been detected inside Unit 3 Reactor at the Fukushima nuclear plant. There’s been no leakage to the outside of the building, the Tokyo Electric Power Company (TEPCO) which is in charge of the decommissioning work, announced.
On Saturday, one of the workers monitoring robots removing debris on the first floor of Unit 3 Reactor found that water was leaking to the drainage ditch in the northeast area of the first floor. TEPCO promised it would investigate into the cause of the leakage without interrupting the decommissioning work.
Besides, the operator has revised the radioactivity levels at the Fukushima No. 1 nuclear plant up to 5 million becquerels of strontium per liter which is a record and almost five times higher than the original reading of 900,000 becquerels per liter, detected in the water sampled last July.
On Friday, the company announced that the previous radiation levels had been wrong and apologized for the failures caused by malfunctioning measuring equipment.
However, the wrong readings only pertain to the radioactivity levels measured in water and those relating to radiation levels in air or soil are likely to have been accurate, according to TEPCO.
The 2011 tsunami caused the meltdown of three nuclear reactors at the Fukushima power plant, leading to the worst nuclear disaster since Chernobyl. Since then, leakage of radiation-contaminated water has posed a major threat to Japan’s population and environment, and to the international community.
By early January, the levels of nuclear radiation around Fukushima’s No. 1 plant rose to 8 millisieverts per year, surpassing the government standard of 1 milliseviert per year, TEPCO announced.
In mid-January, a record high level of beta rays released from radioactive strontium-90 (a radioactive isotope of strontium produced by nuclear fission with a half-life of 28.8 years) was detected beneath the No. 2 reactor’s well facing the ocean.
TEPCO hopes to solve the problem by freezing the ground around the reactors so that no groundwater can pass through it.
Reprinted from The Voice of Russia.