Mars 2011: Kärnkraftverket i Fukushima - utbruten och sammanfogad tråd

Fuel Integrity in the spent fuel pool: Unknown (=1) Unknown (=2) Damage Suspected (=3) Possibly damaged(=4)

●Function of containing radioactive material
It is presumed that radioactive material inside the reactor vessel may leaked outside at Unit 1, 2 and Unit 3, based on radioactive material found outside. NISA announced that the reactor pressure vessel of Unit 2 and 3 may have lost air tightness because of low pressure inside the pressure vessel. NISA told that it is unlikely that these are cracks or holes in the reactor pressure vessels at the same occasion. Nitrogen gas injection into the Unit 1containment vessel has been continued to reduce the possibility of hydrogen explosion since Apr. 6th. The pressure of the vessel has hardly risen for the past a few days and leakage of the vessel is suspected. The same measure will be taken for Unit 2 and 3.

Temperatures rise at No.4 spent fuel storage pool

The Tokyo Electric Power Company, or TEPCO, says the water temperature in the spent fuel storage pool at the No. 4 reactor in the crippled Fukushima nuclear plant has risen to about 90 degrees Celsius. It fears the spent fuel rods may be damaged.

TEPCO took the temperature on Tuesday using an extending arm on a special vehicle. It found the temperature was much higher than the normal level of under 40 degrees.

To cool the fuel, TEPCO sprayed 195 tons of water for 6 hours on Wednesday morning.

The company thinks the pool's water level was about 5 meters lower than normal, but 2 meters above the fuel rods.

TEPCO believes the water level is likely to rise by about one meter after the water spraying on Wednesday.

The company also believes temperatures rose after the loss of the reactor's cooling system.

TEPCO says high levels of radiation at 84 millisieverts per hour were detected above the water surface, where radiation is rarely detected.

The company plans to continue spraying and to analyze radioactive particles in the pool to determine whether the fuel has been damaged.

The storage pool at the No. 4 reactor has housed all the fuel rods that were in operation at the reactor due to massive engineering work there.

TEPCO has sprayed more than 1,800 tons of water on the No. 4 reactor using fire engines and special vehicles since the March 11th crisis. The company feared that fuel rods could cause evaporation of water and put workers at risk of exposure.

University of Tokyo Professor Koji Okamoto says the temperature of 90 degrees indicates that cooling is continuing, although some of the water in the pool may be boiling.

Okamoto says high radiation indicates the possibility of radiation leaks from damaged fuel, and called for the evaluation of water sampling to determine how the situation should be tackled.

The professor says that to prevent further damage to the fuel, it's important to continue cooling the pool while minimizing water leakage from it.

Wednesday, April 13, 2011 21:08 +0900 (JST)