18 Sept (NucNet): Tokyo Electric Power Company (Tepco), the operator of the Fukushima-Daiichi nuclear plant, said yesterday that it released more than 1,000 tonnes of contaminated water into the sea after a typhoon caused high winds and heavy rains at the facility.
The utility said it released about 1,130 tonnes of water with low levels of radioactivity – below the 30 becquerels per litre (Bq/ℓ) of strontium-90, which is the safety limit imposed by Japanese authorities.
Typhoon Man-yi hit Japan on Monday, bringing rain that caused flooding in some parts of the country.
Rainwater built up inside enclosure walls around clusters of tanks containing contaminated water that was used to cool damaged reactors.
“Workers measured the radioactive levels of the water collected in the enclosure walls, pumping it back into tanks when the levels were high,” said Tepco.
“Once finding it was mostly rain water they released it from the enclosure, because there is a limit on how much water we can store.”
Recent leaks of contaminated water were reported on 19 August 2013 when water was discovered inside and outside a dike surrounding one of the water tanks.
On 21 August, the Japan Nuclear Regulatory Authority revised its rating of this leak from a Level 1 to a Level 3 on the International Nuclear and Radiological Event Scale.
The storage tanks were built following the March 2011 accident at the plant to hold radioactive water.
Tepco said earlier this month that an estimated 300 cubic metres of water had escaped from one of the tanks, leaving “hot spots” of pools of radioactive water.
In documents published online, Japan’s Nuclear Regulation Authority (NRA) said monitoring by Tepco of seawater near the plant has shown that in early September the concentration of caesium-137 was 1.7 Bq/ℓ or less. The Ministry of Environment standard for public bathing is 10 Bq/ℓ.
The concentration of caesium-134, tritium (H-3) and total beta were under the limit of detection, the NRA said.
The documents are online: www.nsr.go.jp/english/data/F1_130917-1r.pdf
