The Japanese government is to unveil revised plans on how it aims to make its stricken Fukushima Dai-ichi nuclear plant stable.
The roadmap has been adapted in the wake of news suggesting the damage sustained by three troubled reactors is worse than previously thought.
It is also thought that further light will be shed on support plans for the 80,000 evacuees who had to leave their homes after radiation leaked from the complex in the wake of the March 11 earthquake and tsunami.
The new plan will offer more detail on how authorities plan to honour the timetable announced in April to bring the plant to a stable cold shutdown by early next year.
It will cover 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 is 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 19km 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.