Last night one of the plant's reactors leaked water which turned to radioactive sludge.

But if the fuel or radioactive sludge dried out, there's a risk of airborne contamination and that could take the [contamination] activity off site.

On the other side of the wall, beneath the surface of the water, lie 1,500 tonnes of radioactive sludge and 1,300 skips that contain corroding spent nuclear fuel.

It corroded, forming the radioactive sludge.

However, a substantial amount of residue remains in the older single shell tanks with one containing an estimated 447,000 gallons of radioactive sludge, for example.