The maximum radiation level to which workers can legally be exposed is 250 millisieverts per hour.
Hidehiko Nishiyama, deputy director general of Japan’s Nuclear and Industrial Safety Agency, said his agency has instructed Tepco to search the facility for other potential leaks.
“Today we found highly irradiated water in the pit where the electricity cables are contained,” Nishiyama said. “It seems that there is a crack on the side of the concrete wall of the pit. Some water is spilling out of the crack to the sea.”
At a news conference Saturday, a Tepco spokesman said the company plans to pour concrete into the crack to try to stop the leak.
The discovery came as Tepco was considering broader steps to deal with the burgeoning crisis. Among the latest ideas, officials said, are pumping nitrogen into reactors Nos. 1 and 3 to try to prevent explosions of hydrogen gas that is building up and using an artificial floating island to store contaminated water that has pooled inside the facility.
The reactors, when operating properly, are filled with nitrogen. Officials fear the nitrogen level might have decreased during explosions inside the power plant during the early days of the crisis, after the March 11 earthquake and tsunami knocked out the critical cooling systems.
As Tepco continued to struggle to contain the radiation leaks, a 15-member advance team from the U.S. military’s radiation control unit arrived at Yokota Air Base. Kyodo News reported that 140 more Marines from the unit are on the way. The force can monitor radiation levels, help with search-and-rescue operations and deal with decontamination, the wire service reported.
On Friday, Prime Minister Naoto Kan addressed his nation three weeks after the “Great East Japan Earthquake” to say that although disaster relief continues, the government will now begin focusing its attention on reconstruction, building a “bright and promising future.”
Even as he spoke, U.S. and Japanese military troops and rescue workers joined forces to launch an intensive three-day search for the missing, whose numbers still exceed 16,000.
The operation involved at least 25,000 rescuers, 120 airplanes and 65 ships. They are combing marshes along coastlines where the giant waves washed away whole towns and villages, and teams of divers are fanning out into the ocean. A total of 32 bodies were recovered Friday, according to the Kyodo news service.