Japan raises Fukushima radioactive water leak severity rating

Japan's nuclear regulator said on Wednesday it has officially raised the severity rating of the latest radioactive water leak at the crippled Fukushima nuclear plant to Level 3 on an international scale for radiological releases.

The upgrade by Japan's Nuclear Regulation Authority (NRA)raises the rating of what was Japan's first warning on the International Nuclear and Radiological Event Scale (INES) since the three reactor meltdowns at the Fukushima plant in March2011, which were triggered by a massive earthquake and tsunami. Those meltdowns were classified as Level 7, the highest INES rating.

The plant's operator, Tokyo Electric Power Co, said last week that 300 tonnes of highly radioactive water leaked from a storage tank at the facility. The utility still does not know how long the water may have been leaking and said it was possible the contaminated water may have reached the Pacific Ocean.

The NRA had said last week that it may upgrade the severity of the crisis from a Level 1 ‘anomaly’ to a Level 3 "serious incident" on the INES scale, after consultations with the International Atomic Energy Agency.