The painstaking job of restoring electricity to the control rooms and cooling systems at the damaged Fukushima Nuclear Power Plant resumed on Thursday as radiation from the plant’s reactors continued to spread, although not at levels posing a general health threat.
Work had been suspended after a plume of black smoke was seen coming from the overheating reactor on Wednesday. Later on Thursday, two workers at reactor 3 were taken to hospital after being exposed to radiation, Kyodo news agency reported.
“The smoke might have been caused by oil in a pump catching fire,” said Hidehiko Nishiyama, spokesman of the Nuclear and Industrial Safety Agency. But “the exact cause is unknown,” he added.
Tokyo Electric Power Co., the plant’s operator, said it intended to restart the cooling system of Reactor No. 3 as early as Thursday to cool the reactor core. Until the system comes back online, Tepco plans to continue its operation to pump seawater into the reactor and the storage pool holding spent fuel, using pumper trucks.
In another small step forward, lighting was restored at the control room for the No. 1 reactor Thursday morning, the second control room to start to come back to service after the No. 3 control center, Kyodo News reported.
Earlier in the morning, the previously stable Reactor No. 1 had showed somewhat erratic behavior, as pressure in the reactor pressure vessel rose. High pressure could damage that vessel and could result in the leakage of radioactive materials into the containment vessel, raising the risk of a radiation leak outside the reactor.
Efforts to revive the cooling system for the complex’s six reactors have been fraught with setbacks. On Wednesday, Reactor No. 5 suffered a pump breakdown. Tepco was expected to replace the pump in the morning to facilitate normal cooling operations, according to the safety agency.
At Reactor No. 2, where repair work has been hindered by periods of high radiation inside the reactor building, workers continued their efforts to restore the lighting and control systems. At Reactor No. 4, active and spent fuel rods in the storage pool continued to emit a large amount of heat, “keeping the water near boiling point,” Mr. Nishiyama said.
White smoke was still seen rising from Reactors Nos. 1-4 Thursday morning, apparently vapor evaporating off the storage pools. That is seen as a sign that the hosing operations by firefighters to cool the pool from outside the buildings are yielding only limited results and that the cooling systems need to be restored to stabilize the conditions of the reactors.
Use of seawater to cool the reactors has also begun to raise concerns. Since March 12 Tepco has been flooding the containment vessels of Reactors Nos. 1-3’s in a stopgap attempt to cool down the reactor core and prevent a meltdown. However, fears have emerged that salt in the seawater could cause damage to some of the equipment and even accelerate the overheating of fuel rods.
Later on Thursday, Japan’s nuclear safety agency said three workers stationed at reactor 3 had been exposed to high levels of radiation as they were laying power cables.
Spokesman Hideyuki Nishiyama said the workers had been “exposed to radiation ranging from 170 to 180 millisieverts”, An exposure of 100 millisieverts per year is considered the lowest level at which any increase in cancer risk is evident.
It was also revealed today that Tokyo’s tap water has been contaminated by unusual levels of radiation. The government have issued a warning to all mothers urging them not to let babies drink the tap water.
Tokyo Water Bureau officials said levels of radioactive iodine in some city tap water contained 210 becquerels per litre of iodine 131 – two times the recommended limit for infants. They warned parents not to give babies tap water, although they said it is not an immediate health risk for adults.
Radiation has also seeped into vegetables, raw milk, the water supply and even seawater in the areas surrounding the plant. Meanwhile, officials in Iceland have detected ‘minuscule amounts’ of radioactive particles believed to have come from Fukushima, the site of the worst nuclear accident in 25 years.
The U.S. Food and Drug Administration says it will halt imports of dairy products and produce from the area of Japan where a nuclear reactor is leaking radiation. The FDA says that those foods will be detained at entry and will not be sold to the public. The agency previously said it would just step up screening of those foods.
Other foods imported from Japan, including seafood, will still be sold to the public but screened first for radiation. Japanese foods make up less than 4 percent of all U.S. imports, and the FDA has said it expects no risk to the U.S. food supply from radiation. [via Wall Street Journal, Power Gen Worldwide and Daily Mail (UK)]