Torn Japanese reactor has little water

TOKYO — One of Japan’s crippled nuclear reactors still has fatally high radiation levels and hardly any water to cool it, according to an internal examination Tuesday that renews doubts about the plant’s stability.

A tool equipped with a tiny video camera, a thermometer, a dosimeter and a water gauge was used to assess damage inside the No. 2 reactor’s containment chamber for the second time since the tsunami swept into the Fukushima Daiichi plant a year ago. The probe done in January failed to find the water surface and provided only images showing steam, unidentified parts and rusty metal surfaces scarred by exposure to radiation, heat andhumidity.

The data collected from the probes showed the damage was so severe, the plant operator will have to develop special equipment and technology to tolerate the harsh environment and decommission the plant, a process expected to last decades.

Tuesday’s examination with an industrial endoscope detected radiation levels up to 10 times the fatal dose inside the chamber. Plant officials previously said more than half of the melted fuel has breached the core and dropped to the floor of the primary containment vessel, some of it splashing against the wall or the floor.

Particles from melted fuel have probably sent radiation levels up to dangerously high 70 sieverts per hour inside the container, said Junichi Matsumoto, spokesman for Tokyo Electric Power Co.

“It’s extremely high,” he said, adding that an endoscope would last only 14 hours in that condition. “We have to develop equipment that can tolerate high radiation” when locating and removing melted fuel during the decommissioning.

The probe also found the containment vessel - a beaker-shaped container that encloses the core - had cooling water up to only 2 feet from the bottom, far below the 10 yards estimated when the government declared the plant stable in December.

Finding the water level was important to help locate damaged areas where radioactive water is escaping.

The actual water level inside the chamber was way off the estimate, which had used data that turned out to be unreliable, he said.

Three Fukushima reactors melted down, but the No. 2 reactor is the only one that has been examined because radiation levels inside the reactor building are relatively low and its container is designed with a convenient slotto send in the endoscope.

The precise condition of the other two reactors, where hydrogen explosions damaged their buildings, is still unknown. Simulations have indicated that more fuel inside No. 1 has breached the core than the other two, butradiation at No. 3 remains the highest.

The high radiation levels inside the No. 2 reactor’s chamber mean it’s inaccessible to the workers, but parts of the reactor building are accessible for a few minutes at a time, with the workers wearing full protection.

Last year’s earthquake and a tsunami set off the worst nuclear accident since Chernobyl.

During a recent visit by a group of journalists, the head of the plant said it remains vulnerable to strong aftershocks and tsunamis, and containing contaminated water and radiation is a challenge. Radioactive water has leaked into the ocean several times already.

Workers found the fresh leak of 120 tons from a water treatment unit this week from one of its hoses, with an estimated 20 gallons escaping into the ocean, Matsumoto said. Officials are still investigating its impact.