ORIGINALLY PUBLISHED: 12.46pmUPDATE 1: 1.35pm: remove mistaken description of rainwater valve as faulty Tepco is working to control a leak of highly radioactive water from a storage tank at Fukushima Daiichi. Water escaped from the tank and then reached the environment through a rainwater valve in the surrounding dam.
The cooling of the reactor cores damaged in March 2011 still requires a constant flow of water, which circulates through the power plant basements before treatment and storage in a complex of large tanks. The water becomes highly radioactive after contact with the cores and is pumped to a storage and treatment facility. After decontamination the water is used again for cooling.
At about 9.50am yesterday, a worker on routine inspection found water leaking from a rainwater drain valve in a dam that surrounds a tank of pre-treated water. This had formed two shallow puddles outside the dam. Investigations showed that the level of water in the tank was about 3 metres lower than expected, indicating that some 300 cubic metres had escaped. The water was said to be highly radioactive: 80,000 becquerels per cubic centimetre.
The drain valve has now been successfully closed. Water from the failed tank is currently being pumped to other tanks and Tepco is removing water from within the dam to a temporary tank before it will be added to other tanks at the facility.
Tepco is already removing the soil near the leak site and placing large sandbags in its place. The company's scientists are investigating how far the water may have spread and checking the area every three hours. It is also cleaning the floor slabs in the area.
There is no evidence that the water entered a drainage ditch, said Tepco, meaning it is unlikely to have left the area or reached the sea. The incident has been classified at Level 1 on the International Nuclear Event Scale - an anomaly.
Researched and writtenby World Nuclear News