Emergency cooling effort failing at Japanese reactor, deepening crisis

Tokyo: Japan's struggle to contain the crisis at a stricken nuclear power plant worsened sharply early Tuesday morning, as emergency operations to pump seawater into one crippled reactor failed at least temporarily, increasing the risk of an uncontrolled release of radioactive material, officials said.

With the cooling systems malfunctioning simultaneously at three separate reactors at the Fukushima Daiichi Nuclear Power Station after the powerful earthquake and tsunami, the acute crisis developed late Monday at reactor No. 2 of the plant, where a series of problems thwarted efforts to keep the core of the reactor covered with water -- a step considered crucial to preventing the reactor's containment vessel from exploding and preventing the fuel inside it from melting down. (Read: Meltdown threat rises at Japan nuclear plant)

The plant's operator, Tokyo Electric Power, said late Monday that repeated efforts to inject seawater into the reactor had failed, causing water levels inside the reactor's containment vessel to fall and exposing its fuel rods. After what at first appeared to be a successful bid to refill the vessel, water levels again dwindled, this time to critical levels, exposing the rods almost completely, company executives said.

Workers were having difficulty injecting seawater into the reactor because its vents -- necessary to release pressure in the containment vessel by allowing radioactive steam to escape -- had stopped working properly, they said.

The more time that passes with fuel rods uncovered by water and the pressure inside the containment vessel unvented, the greater the risk that the containment vessel will crack or explode, creating a potentially catastrophic release of radioactive material into the atmosphere -- an accident that would be by far the worst to confront the nuclear power industry since the explosion of the Chernobyl nuclear power plant 25 years ago.

In reactor No. 2, which is now the most damaged of the three at the Daiichi plant, at least parts of the fuel rods have been exposed for several hours, which also suggests that some of the fuel has begun to melt. If more of the fuel melts before water can be injected in the vessel, the fuel pellets could burn through the bottom of the containment vessel and radioactive material could pour out that way -- often referred to as a full meltdown. (Watch: Hydrogen explosion at the Fukushima plant)

"They're basically in a full-scale panic" among Japanese power industry managers, said a senior nuclear industry executive late Monday night. The executive is not involved in managing the response to the reactors' difficulties but has many contacts in Japan. "They're in total disarray, they don't know what to do."

The extreme challenge of managing reactor No. 2 came as officials were still struggling to keep the cores of two other reactors, No. 1 and No. 3, covered with seawater. There was no immediate indication that either of those two reactors had experienced a crisis as serious as that at No. 2.

But part of the outer structure housing reactor No. 3 exploded earlier on Monday, as did the structure surrounding reactor No. 1 on Saturday. Live footage on public broadcaster NHK showed the skeletal remains of the reactor building and thick smoke rising from the building. Eleven people had been injured in the blast, one seriously, officials said. (Read: Scramble at reactor after new blast)

Chief Cabinet Secretary Yukio Edano said earlier Monday that the release of large amounts of radiation as a result of the explosion was unlikely. But traces of radiation could be released into the atmosphere, and about 500 people who remained within a 12-mile radius were ordered temporarily to take cover indoors, he said.

Mr. Edano and other senior officials did not immediately address the threat of radioactive release from reactor No. 2.

The country's nuclear power watchdog said readings taken soon after the explosion showed no big change in radiation levels around the plant or any damage to the steel containment vessel, which protects the radioactive material in the reactor.

"I have received reports that the containment vessel is sound," Mr. Edano said. "I understand that there is little possibility that radioactive materials are being released in large amounts."

In screenings, higher-than-normal levels of radiation have been detected from at least 22 people evacuated from near the plant, the nuclear safety watchdog said, but it is not clear if the doses they received were dangerous.

Technicians had been scrambling most of Sunday to fix a mechanical failure that left the reactor far more vulnerable to explosions. (Watch: NDTV's special report on Japan's nuclear crisis)

The two reactors where the explosions occurred are both presumed to have already suffered partial meltdowns -- a dangerous situation that, if unchecked, could lead to a full meltdown.