A fire at a spent-fuel pool could release cesium-137.

The report referred to a leak from a spent-fuel pool at Indian Point that was first discovered in August 2005.

The outdoor drain into which the water flowed is contaminated because over the years, water has leaked from the spent-fuel pool, where the used fuel is kept.

One item in question is the structure of the spent-fuel pool, Mr. Galatis said.

No one can get to the spent-fuel pool at reactor 4, or keep it and the others from being the source of further radiation releases.

The fuel is in the spent-fuel pool, and the reactor has been drained of water.

So far, at a pace of one bundle every 30 minutes, the utility has shifted approximately 50 bundles from the reactor to the spent-fuel pool.

And while a reactor core is isolated by thick layers of steel and concrete, a spent-fuel pool is largely unshielded.

A spent-fuel pool can hold many more fuel-rod assemblies-and thus much more radioactive material-than a reactor core.

Mr. Mayer is also involved in the effort to stop a much smaller leak from the spent-fuel pool of Indian Point 2.