If that turns out to be true, the devastated nuclear complex may be much more contaminated with radioactive materials than officials had previously thought.
The suspected reactor breach would mark a major setback for the crews racing to return power to the plant and bring its reactors and spent-fuel pools back under control.
Japanese Prime Minister Naoto Kan said Friday that the situation at Fukushima remained grave: “We are not in a position where we can be optimistic. We must treat every development with the utmost care.”
Two weeks to the day after an earthquake and tsunami devastated northeastern Japan, authorities had hoped that they could see an end to their fight to prevent more widespread release of radioactive material from Fukushima Daiichi, also known as Fukushima I. Connection of temporary electrical lines has returned lights to reactor control rooms, one by one. Instruments are beginning to function again at most units. Some coolant pumps are being tested to see if they can return to life.
But a serious accident March 24, in which three workers were exposed to radiation in the turbine room of the No. 3 reactor, alerted authorities to the possible reactor breach, according to NHK World News.
The workers were dragging an electrical cable through contaminated water to restart a crucial pump when water poured over their protective boots, soaking their feet. They ignored warning alarms sounded by their personal radiation dosimeters, perhaps in the belief that they were faulty, according to an account of the accident from the International Atomic Energy Agency.
Two of the three workers were taken to a nearby hospital, where they will remain under observation for at least four days, said the IAEA.
An examination of the water the workers sloshed through showed its radiation level to be 10,000 times higher than normal, said NHK. The radiation almost certainly came from the reactor itself, not the nearby spent-fuel pools, according to officials.
Temperature and pressure inside the No. 3 reactor core remained stable, indicating that further damage was not imminent. Work halted for a time at Fukushima Daiichi due to the incident, but resumed Friday.
The breach in No. 3 could have occurred on March 14, when a hydrogen explosion destroyed part of the surrounding containment building.
Evacuation zone enlarged
In a related development, Japanese authorities have begun to encourage people to evacuate from a larger zone around the Fukushima plant.
Japan previously evacuated all residents within 12 miles of the nuclear complex. Officials now say they will aid those who live from 12 to 19 miles from the plant if they, too, want to leave.
Japanese Cabinet Secretary Yukio Edano said that people within the 12 to 19 mile zone should still be safe if they stay indoors. But due to the difficulty in delivering supplies to the area, it might be best if those residents voluntarily evacuated, he said at a press briefing Friday.
US officials have told US citizens to stay at least 50 miles away from the Fukushima plant. Some experts have urged Japan for days to expand its own evacuation zone.
“It looks like there are going to be areas considerably further than 12 [miles away from the plant] that may require significant decontamination or condemnation,” said Edward Lyman, a senior scientist at the Union of Concerned Scientists, in a phone briefing for reporters on Thursday.