Storage of rainwater leads to spill

03 October 2013

A mistake in dealing with rainwater after a typhoon has led to a spillage of partially treated water at Fukushima Daiichi. There appears to be no impact beyond the immediate area.

The spill came from the same kind of storage tank as was involved in the leak in August, but this time the accidental release of water was due to an operational error rather than a mechanical failure.

In stormy weather yesterday following a typhoon, significant rainwater was accumulating in the area behind a dam that surrounds storage tanks of partially treated water. The Nuclear Regulatory Authority has not yet decided on a recent Tepco proposal for dealing with this kind of build-up of rainwater with a potential to be lightly contaminated so Tepco decided to add the rainwater to a series of storage tanks. One of these was already close to full and subsequently overflowed.

About 430 litres of water, containing significant tritium contamination of 580,000 becquerels per litre, spilled from the top of the tank and flowed down its outside wall. An inspection walkway on the outside of the tank diverted the flow to fall about one metre outside of the dam at the tank's base. Soil from this area is being recovered.

Tepco said it could not exclude the possibility of some water having flowed into a small drainage channel leading to the sea and took the precaution of placing sand bags in it. Measurements of beta radiation in that channel have increased in recent days but not above historic variations, while measurements where the channel meets the sea have not changed and remain within standards suitable for public bathing. The usual method for disposing of water containing tritium is dilution in a body of water like a river, lake or the sea.

Researched and written
by World Nuclear News