NHK...

Tokyo Electric Power Company has decided to be more cautious about the volume of cooling water injected into the spent fuel pool of one of its reactors.
This is due to fear that the reactor building might be further damaged by the weight of the water itself.

The company has been injecting water daily into the spent fuel pools of the reactors to prevent fuel rods from being exposed and further damaged.

At the Number 4 reactor's pool, the water temperature was about 91 degrees Celsius on Friday, more than 50 degrees higher than the normal level, and TEPCO was forced to inject 200 tons of water. Substantial amounts of water will have to be injected daily.

Citing damage to the walls of the building supporting the pool during last month's hydrogen explosion, the power company says excessive water injection could further weaken the structure of the building.

From Saturday, the utility started assessing more carefully the appropriate amount of water to be poured into the pool, using a device to monitor temperature and the level of cooling water in the pool.

1,535 spent fuel rods are stored in the pool of the Number 4 reactor's building, the largest amount at the site.

Saturday, April 23, 2011 12:23 +0900 (JST)

The Japanese government has expressed concern about the structural strength of the Fukushima Dai-ichi nuclear power plant's Number 1 reactor. It says the ongoing water injections may be making the vessel less earthquake resistant.

Tokyo Electric Power Company, or TEPCO, is planning to fill part of the containment vessel with water to cool the reactor.

TEPCO wants the water level to reach the top of the fuel rods in reactors one and three by mid July, so it can cool them under more stable conditions.

At the Number 1 reactor, where fuel rods are believed to be the most seriously damaged, six tons of water are being injected every hour.

TEPCO believes the water is vaporizing, then condensing in the containment vessel.

The water level is now estimated to be about half way up the bulb of the dry well.

TEPCO says the water accumulation will not compromise the structure. But the Nuclear and Industrial Safety Agency says large amounts of water can make the building less earthquake-proof.

The agency says it needs to check whether the suppression pool pipes can withstand higher levels of pressure from the extra water.

Saturday, April 23, 2011 07:20 +0900 (JST)