Japan's nuclear regulator has upgraded the rating of last week’s 300-tonnes contaminated water leak to Level 3 of the International Nuclear and Radiological Events Scale.
Originally, the event was described as Level 1 – an anomaly. However, after consulting the International Atomic Energy Agency, the Nuclear Regulation Authority of Japan increased the rating to Level 3 – a serious incident.
The International Nuclear and Radiological Events Scale (INES), introduced in 1990, was designed to improve information sharing within the international community regarding safety-significant issues involving nuclear accidents.
The 2011 Fukushima disaster itself was rated the maximum Level 7 - similarly to the even worse 1986 Chernobyl explosion.
On 19 August, Tepco – the operator of the damaged Fukushima nuclear power plant - reported about 300 tonnes of highly contaminated water had escaped from a storage tank, some of it probably reaching the ocean through a rainwater gutter.
The incident has further undermined trust in Tepco and its ability to handle the situation, prompting the Japanese government to promise it will take over the clean-up efforts.
It has also been announced earlier this week that Japan will partner with Ukraine to launch a satellite system monitoring Fukushima and Chernobyl power plants and their surroundings.