Frantic Repairs Go On at Plant as Japan Raises Severity of Crisis
Kyodo News, via Associated Press
Fire trucks converged in preparation for spraying water at the Fukushima nuclear plant, in Iwaki, on Friday. More Photos »
By HIROKO TABUCHI and KEITH BRADSHER
Published: March 18, 2011
Japanese engineers battled on Friday to cool spent fuel rods and restore electric power to pumps at the stricken Fukushima Daiichi Nuclear Power Station as new challenges seemed to accumulate by the hour, with steam billowing from one reactor and damage at another apparently making it difficult to lower temperatures.
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In a further sign of spreading alarm that uranium in the plant could begin to melt, Japan planned to import about 150 tons of boron from South Korea and France to mix with water to be sprayed onto damaged reactors, French and South Korean officials said Friday. Boron absorbs neutrons during a nuclear reaction and can be used in an effort to stop a meltdown if the zirconium cladding on uranium fuel rods is compromised.
Tokyo Electric Power Company, which operates the plant, said earlier this week that there was a possibility of “recriticality,” in which fission would resume if fuel rods melted and the uranium pellets slumped into a jumble together on the floor of a storage pool or reactor core. Spraying pure water on the uranium under these conditions can actually accelerate fission, said Robert Albrecht, a longtime nuclear engineer.
In the past two days, Japanese officials have focused their efforts on cooling spent fuel rods in a storage pool in Reactor No. 3, but steam, probably carrying radioactive particles, was also seen on Friday rising from Reactor No. 2., which was hit by an explosion on Tuesday.
Additionally, a senior Western nuclear industry executive said that there also appeared to be damage to the floor or sides of the spent fuel pool at Reactor No. 4, and that this was making it extremely hard to refill the pool with water. The problem was first reported by The Los Angeles Times.
Engineers had said on Thursday that a rip in the stainless steel lining of the pool at Reactor No. 4 and the concrete base underneath it was possible as a result of earthquake damage. The steel gates at either end of the storage pool are also vulnerable to damage during an earthquake and could leak water if they no longer close tightly.
The senior executive, who asked not to be identified because his comments could damage business relationships, said Friday that a leak had not been located but that engineers had concluded that it must exist because water sprayed on the storage pool has been disappearing much more quickly than would be consistent with evaporation.
Technicians at the plant focused Thursday on fixing electrical connections at Reactor No. 2 and spraying more water on Reactor No. 3 while studying the problem at Reactor No. 4.
“They have to figure out what to do, and certainly you can’t have No. 2 going haywire or No. 3 going haywire at the same time you’re trying to figure out what to do with No. 4,” said the executive, who said he had learned of the problem from industry contacts in Japan.
One concern at No. 4 has been a fire that was burning at its storage pool earlier in the week; American officials are not convinced the fire has gone out. American officials have also worried that the spent-fuel pool at that reactor has run dry, exposing the rods.
The new setbacks emerged as the first readings from American data-collection flights over the plant in northeastern Japan showed that the worst contamination had not spread beyond the 19-mile range of highest concern established by Japanese authorities.
But another day of frantic efforts on Thursday to cool nuclear fuel in the troubled reactors and in the plant’s spent-fuel pools resulted in little or no progress, according to United States government officials. The crisis at the plant seemed increasingly to have produced divergent narratives in Washington and Tokyo, with Japanese officials emphasizing the effo rts they were making to tame the damaged plant and American officials highlighting the challenges.
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