100 metric tons of radioactive water leaked from a holding tank at Japan's Fukushima Daiichi nuclear power plant on 20 February 2014.
The leak of an estimated 100 metric tons of highly contaminated water was discovered by Tokyo Electric Power Company (TEPCO).
The water leak was highly radioactive with a reading of 230 million becquerels per litre of radioactive isotopes. A becquerel is a unit used to measure radioactivity. WHO guidance advises against drinking water with radioactivity levels higher than 10 becquerels per litre.
The level is about 7.6 million times the government’s limit for water allowed to be released into the ocean.
The leak, according to TEPCO, might have been caused by a faulty valve in the pipes that transfers water from a decontamination facility to storage tanks.
However, the contaminated water had not reached the Pacific Ocean because the tank is located several hundred metres away from the sea and there are no spillways near the tank.
The Fukushima nuclear plant was damaged by an earthquake and tsunami in 2011 faced multiple problems including leaks and power cuts since the disaster.
Since the incidence, TEPCO has been storing the enormous volumes of water contaminated at the site in a steadily growing collection of containers.
According to TEPCO, as many as 20 trillion becquerels of cesium-137, 10 trillion becquerels of strontium-90 and 40 trillion becquerels of tritium have found their way into the sea by way of groundwater leaks between May 2011 and August 2013.
When: 20 February 2014