The Daily Yomiuri
In an effort to restore power at the crippled No. 2 reactor of Fukushima No. 1 nuclear power plant, Tokyo Electric Power Co. has successfully connected a power cable with the reactor, raising hope the utility will be able to activate the central control room.
TEPCO was working Sunday to electrify the central control room using the power supplied to the No. 2 reactor.
Work to restore electricity at the Fukushima nuclear power plant is under way in three separate reactor groups--Nos. 1 and 2; Nos. 3 and 4; and Nos. 5 and 6. The highest priority was placed on the No. 2 reactor, whose reactor containment vessel is feared to have been damaged in the aftermath of the magnitude-9.0 quake that hit the Tohoku region on March 11.
Among the Nos. 1 to 4 reactors, the No. 2 reactor reportedly suffered the least quake and tsunami damage to its pumps and electrical equipment, making TEPCO officials hopeful that the equipment will start functioning once electricity is supplied.
TEPCO set up a temporary power switchboard on a vehicle near the No. 1 reactor Friday, and connected the devices with a cable to the No. 2 reactor's power switchboard-cum-transformer at the turbine building.
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Water-spraying continues
Meanwhile, Self-Defense Forces personnel and a special squad of the Tokyo Fire Department continued spraying water on troubled reactors in an effort to avert further disaster.
On Sunday morning, SDF personnel sprayed water on the No. 4 reactor for the first time, following a similar operation on the No. 3 reactor that lasted until early Sunday.
The SDF mission started at about 8:20 a.m. and ended 9:40 a.m., having sprayed about 82 tons of water using 10 SDF fire trucks and one fire truck TEPCO borrowed from U.S. forces, Tokyo Electric Power Co. said.
It is feared rising water temperature in the temporary storage pool at the No. 4 reactor will lower the water level in the pool and expose fuel rods, resulting in the leakage of radioactive material into the air.
The radiation level in the plant vicinity declined after the Tokyo Fire Department sprayed water on the No. 3 reactor on Saturday and Sunday.
Radiation levels at a location about 500 meters from the No. 1 reactor went down from 3,443 microsieverts per hour as of 2 p.m. Saturday to 2,758 microsieverts as of 3:40 a.m. Sunday, according to officials.
The water-spraying operation on the No. 4 reactor by the Tokyo Fire Department was to resume Sunday night.
The SDF and firefighters from across the nation, including the Osaka Municipal Fire Department, are expected to continue their water-spraying mission.
At the No. 3 reactor, on which Tokyo firefighters sprayed water from 2:05 p.m. Saturday until 3:40 a.m. Sunday, pressure within the reactor containment vessel started rising again, forcing TEPCO officials to consider releasing steam in the vessel to lower the pressure, TEPCO said.
Pressure in the containment vessel went up from about 2.8 atmospheres at 1:10 a.m. to 3.4 atmospheres at 4:30 a.m.
However, the pressure in the containment vessel stabilized as of noon. TEPCO officials continued to closely monitor changes in pressure inside the vessel for the time being.
At the Nos. 5 and 6 reactors, TEPCO successfully activated heat exchangers in temporary storage pools for spent nuclear fuel rods using emergency diesel power generators, including one that was repaired Saturday, making it possible to significantly lower water temperature in the storage pools.
Water temperatures in storage pools in the Nos. 5 and 6 reactors were 37.1 C and 41.0 C, respectively, as of 7 a.m., and were within or near the target temperature range of 40 C or below, TEPCO officials said.
TEPCO said the number of its workers whose radiation exposure exceeded 100 sieverts increased to seven from six as of 5 a.m. Sunday. The government had raised the upper limit of the radiation exposure for workers at the Fukushima plant from the ordinary 100 sieverts to 250 sieverts as an exceptional measure.
Meanwhile, TEPCO was considering using a German-made high-pressure pump capable of spraying water on a distant target with a boom longer than 50 meters, according to TEPCO sources. The pump is used to pour concrete at construction sites.
(Mar. 21, 2011)
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