The operator of the damaged Fukushima nuclear plant admits discovering contaminated water dripping from one of its cooling tanks.
The tanks, which had been introduced to contain an earlier leak, were discovered to be dripping contaminated water at around midday on 5 June.
The new is likely to complicate operator Tepco’s efforts to get permission to release groundwater from the plant to the sea, particularly in the wake of the news that radioactive caesium was found in groundwater in the vicinity of the plant before the water even entered the site.
Tepco had previously insisted that the contamination was insignificant and that the water was safe enough to be dumped into the ocean. This latest news will erode the trust with the local authorities and fishermen, whose consent is required to route the groundwater away from the plant and into the ocean.
About 400 tonnes of groundwater flows daily into the reactor buildings where it mixes with highly contaminated water that comes from cooling the melted fuel.
Shunichi Tanaka, chief of Japan's new nuclear regulator, set up after its predecessor was discredited in the 2011 disaster, told media that Tepco should deal with the problem immediately. However, he added that the regulator did not regard the matter as serious.
A series of water leaks and power outages beset the facility in March and April making it difficult for the company to persuade the public and the government that it has the problem of contaminated water under control.
Last week, the Japanese government ordered Tepco to increase the storage capacity of the water tanks and construct a wall of frozen earth around the four reactor buildings to stop the flow of groundwater seeping into the plant.
Fukushima also hosted an international Emergency Response workshop organised by the Response and Assistance Network (RANET) of the International Atomic Energy Agency (IAEA). More than 40 participants from 18 countries took part in the four-day exercise aimed at further strengthening nuclear and radiological preparedness and learning lessons from the world's most serious nuclear disaster since the explosion at Chernobyl at 1986.
The participants were monitoring radiation, measuring contamination levels of soil and analysing samples taken from the areas affected after the March 2011 accident. “By bringing together so many experts from different countries in one place, the workshop helped us learn how international teams can work together to provide assistance in a nuclear or radiological emergency situation”, said IAEA RANET officer Pat Kenny.
RANET is a network currently comprising 22 countries through which the IAEA can facilitate the provision of expert support and equipment on request under the Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency. The workshop was the first activity conducted from the IAEA RANET Capacity Building Centre, a new training centre based in the city of Fukushima that was designated earlier this week with the support of the Japanese Foreign Ministry and Fukushima Prefecture.