A possible breach of one of the reactor cores at Japan's Fukushima Daiichi nuclear plant could lead to further contamination and be a major setback to efforts to bring the post-earthquake crisis under control, Japanese officials said today.
A senior nuclear executive was quoted by the New York Times as saying, "There is a definite, definite crack in the vessel -- it's up and down and it's large." The executive told the Times that the crack runs down the side of the reactor vessel below the water level and that the reactor has been leaking fluids and gases.
"The problem with cracks is they do not get smaller," said the Times' source.
Because of the new setback, work halted again today at the nuclear complex 150 miles northeast of Tokyo, where dozens of people have been working to cool reactors at the damaged plant.
A somber Prime Minister Naoto Kan today called the situation "grave and serious."
"We are not in a position to be optimistic," he said.
"We must remain vigilant," Kan said. "We must treat every development with the utmost care.
"We are working closely with local governments and stepping up our monitoring efforts and increasing monitoring [of radiation] and will disclose results promptly. We are committed to transparency," Kan said.
The breach was suspected when two workers waded into water 10,000 times more radioactive than normal and suffered skin burns, according to the Nuclear and Industry Safety Agency. The agency has yet to comment on the New York Times' report, but did speak on the situation earlier today.
"It is possible there may be damage somewhere in the reactor," spokesman Hidehiko Nishiyama said, adding that the cause of the burns was still unclear.
Nishiyama said there is no data suggesting there were any cracks, and that a leak in the plumbing or the vents could be the cause.
"As bad as the releases have been so far, they could increase by severalfold, ultimately, if this proceeds any further," said Edwin Lyman, a senior scientist at the Union of Concerned Scientists. "If all the iodine in three of the reactors were released, I believe it would only be a few times what was released at Chernobyl. I don't know if that's good news, but certainly the delay and the ability of the authorities to manage this crisis may have really helped in the ultimate radiological consequences."
Meanwhile, the death toll in Japan was estimated at 10,175 people, according the the NHK television network. More than 17,400 were still missing. It has been two weeks since the 9.0-magnitude earthquake and resulting tsunami hit on March 11.
The U.S. military is now taking a direct role in attempts to cool reactors at the damaged nuclear plant, according to U.S. and Japanese officials.
As a first step, the U.S. military plans to ship 525,000 gallons of fresh water on two U.S. Navy barges from a U.S. base in Yokosuka, south of Tokyo, according to a spokesman for the U.S. Forces Japan.
Tap water in Tokyo was reported to contain levels of radioactive iodine two times the legal limit for infants earlier this week. A day later it was reported that the tap water was safe to drink.
The confusion caused a run on bottled water and overwhelmed a government plan to distribute bottled water to families with babies.
Japan is still trying to feed and relocate hundreds of thousands of homeless survivors, clear away tons of debris and bury the thousands of dead.