Fukushima leak could become 'nuclear disaster'

A fifth leak of radioactive groundwater has been discovered at Tokyo Electric Power Company's (Tepco's) crippled Fukushima nuclear power station. The most recent leak is reportedly the worst so far and could culminate in nuclear disaster that will take years to clean up.

According to Japan's nuclear watchdog, a series of leaks have been detected coming from the storage tanks on the site. The tanks are used to store water that has leaked into the damaged reactors and, as a result, have become highly radioactive. Tepco have struggled to contain the contaminated groundwater so as to stop it from reaching the sea.

Hundreds of steel tanks have been used on the site to store the water. Tepco have announced that around 300 tonnes of highly radioactive water has leaked from one of the tanks; the leak was discovered earlier this week. It is not yet clear how the leak occurred, but it is thought that the water may have escaped through a seam in the tank. As all of the tanks are of the same design, there is a possibility that yet more drastic leaks will occur.

Shunichi Tanaka, the Nuclear Regulation Authority chairman, said: "That's what we fear the most. We must remain alert. We should assume that what has happened once could happen again, and prepare for more.  We are in a situation where there is no time to waste."

Upon testing of some of the leaked water it was found to be emitting around 100 millisieverts an hour of radiation, according to the Kyodo news agency. Speaking to Reuters, the general manager of Tepco Masayuki Ono explained that this level of radiation per hour is the equivalent to exposure limit for nuclear workers over a period of five years. This means that the contaminated, leaked groundwater is able to give a person a five-year dose of radiation in only an hour.

Work is now being done to remove the remaining water from the leaking tank and to transfer it to secure containers. Checks are also ongoing of the other tanks on the site to ensure there are no further leaks. Tepco will now have to recover any contaminated soil and put in place stronger monitoring processes to avoid any further fallout.