Water poses questions for Tepco

Thursday, 12 May 2011

Radioactivity test results are back on the leak discovered yesterday at Fukushima Daiichi 3, while better data from unit 1 has begun to illuminate the damage there. Off-site, tap water restrictions have all been lifted.

 

Results announced by Tokyo Electric Power Company (Tepco) today showed the water found leaking to sea from a cable pit near unit 3 was contaminated with iodine-131, caesium-137 and caesium-134 to levels far beyond regulatory limits.

 

No more water restrictions   The last remaining restriction on the consumption of drinking water was lifted on 10 May. Some 21 separate orders to avoid giving tap water to infants due to levels of iodine-131 were imposed in the last week of March. Only one was placed on tap water consumption by the general public, in Iitate, and this too has now been lifted.   Some 74 thousand homes remain cut off from mains water due to damage caused by the natural disasters on 11 March.

This would indicate the water may have been in contact with the damaged reactor core, and thereby raise the question of its travel through the nuclear site. The water was leaking from a cable penetration in a concrete pit near the sea. This is part of a system of cable trenches to supply power to pump rooms, separate from seawater piping ducts.

 

In the last two weeks the temperature of unit 3 has gradually risen from around 90ºC to around 210ºC. It is not known if this is related to the water leak.

 

Meanwhile at unit 1 the return of workers to the reactor building interior seems likely to lead to revelations about the true state of the core. Tepco has installed and calibrated one of two new water level gauges, finding the level to be below what was previously thought. This led to speculation that the entire reactor core may have been exposed for long periods of time, with the increased chance of serious damage.

 

The low water level also raises the question of where the water injected to the reactor core over the last eight weeks has gone. It is thought that some may have passed from the reactor vessel into the surrounding containment vessel and this idea has caused Tepco to reconsider its plan to flood the containment, potentially affecting the overall plan to stabilise the site.

 

Researched and written

by World Nuclear News