2011-05-17 14:36

TOKYO - Japan was to release a revised roadmap Tuesday for stabilizing its stricken nuclear plant amid signs that three troubled reactors have suffered worse-than-expected damage from the March 11 earthquake and tsunami.

The government is also expected to provide more details about how it will support some 80,000 evacuees who fled their homes near the radiation-leaking Fukushima Dai-ichi complex.

While authorities insist they will stick with a timetable announced in April to bring the plant to a stable cold shutdown by early next year, the new plan will provide more details on achieving that goal, including how operator Tokyo Electric Power Co. will restore cooling systems that were knocked out by the twin disasters.

Officials say that recent data from repaired gauges indicate that it's likely that fuel rods in at least one reactor had almost totally melted and fallen to the bottom of the capsule-shaped pressure vessel in the hours after the quake and tsunami hit. Although no workers were allowed inside two other reactor buildings to take new measurements, officials assume similar damage at Units 2 and 3 based on the duration they were out of cooling water.

By spraying water into the reactor cores, TEPCO has kept the temperatures well below dangerous levels so that the lumps of fuel pose no immediate threat, officials say.

But the melted fuel has probably created some holes in the pressure vessel through which water is leaking into and then out of the larger beaker-shaped containment vessel, officials say. That would help explain why the vast amount of radioactive water has collected in the lower levels of the reactor buildings.

The new plan will likely elaborate on how the utility plans to pump out and decontaminate the water - and possibly use it to circulate back into the reactor.

The recent findings suggesting serious leakage render a tentative plan to fill Unit 1's containment vessel with water unworkable. The utility has discussed the possibility of installing large cooling fans to further bring down the temperature of the core.

TEPCO has also said it is laying the groundwork for a plan to cover the reactors with a tent-like material to keep radioactive particles from spreading into the air.

Until all the reactors are safely shut down, they continue to leak radiation, though in much smaller amounts than in the early days of the disaster.

Still, the sheer volume of contaminants spewed from the plant - and their buildup in places outside the 12-mile (20-kilometer) evacuation zone - persuaded the government to order residents to leave more towns in late April. Some of those residents began evacuating this past weekend and will continue to move out through the end of May.