Troubles continue at Japan’s crippled nuclear plant, where technicians believe they have solved one big problem but are confronting another.
Officials said Wednesday they have finally stopped a leak of radioactive water from the Fukushima power station that was raising radiation in the nearby ocean to millions of times the legal limit.
But now they are worried about a build-up of hydrogen inside the containment vessel at another of the plant’s six reactors, creating the risk of an explosion that could release large amounts of radiation into the atmosphere. Plant officials said they may pump nitrogen into the reactor in an attempt to halt the chemical reaction.
Also Wednesday, Chief Cabinet Secretary Yukio Edano apologized to neighboring countries for Japan’s failure to notify them before it began pumping thousands of tons of low-level radioactive water into the sea near the plant.
Edano said the action, which could continue until Friday, is necessary to make room in a storage area for water that is 200 thousand times more dangerous. But he said steps have been taken to ensure better communication with nearby countries before such steps are taken in future.
Edano said the water leak, which had sent radiation levels in the nearby ocean to 7.5 million times the allowable limit on Saturday, had been stopped by 5:38 a.m. Wednesday. But he said it is too early to say with confidence that the problem has been solved, and that officials are still trying to determine whether radioactive water is leaking from any other locations.
Officials at the Tokyo Electric Power Company, which operates the Fukushima plant, said the latest threat of a hydrogen build-up is taking place at its number-one reactor. Japan’s NHK television quoted officials saying the build-up is occurring inside the containment vessel that keeps radiation from escaping into the atmosphere, and is an indication that the reactor’s core has been damaged.
Hydrogen explosions destroyed the outer buildings housing the number-one and three reactors earlier in the crisis, which began when a massive earthquake and tsunami destroyed the power plant’s cooling systems on March 11. Those blasts may also have damaged the containment vessels.
The high radiation levels in the nearby ocean were caused by water leaking from a storage pit next to the number two reactor. After days of failed efforts, technicians managed to stop the leak by injecting a hardening agent called liquid glass into the soil and gravel around the pit. TEPCO is still exploring ways to make sure the seal is permanent.
Highly radioactive water has accumulated in the basements of several of the plant’s reactors after weeks in which workers have pumped massive amounts of water over the reactors to prevent their fuel rods from overheating. The water needs to be removed before workers can complete repairs to the permanent cooling systems.
Technicians began Tuesday to pump 11,500 tons of lightly radioactive water into the ocean to make room in a storage area for the most dangerous water, most of it in the basement and utility tunnels at the number-two reactor. But South Korea has protested the action, suggesting it may violate international law.
National police said Wednesday the confirmed death toll in the March 11 disasters now stands at 12,468, with more than 15,000 people still unaccounted for.