Authorities say the high levels might be from the spent fuel pool lined with reinforced concrete.
We also need to cool the reactor and the spent fuel in the spent fuel pool but that basically means you wanna maintain the coolant inventory which means water in the primary system.
Given the crucial need to cool temperatures in the spent fuel pool and other parts of the reactors, "I think it is a battle against time", Mr Amano said.
Gregory Jaczko, chair of the US Nuclear Regulatory Commission, warned there was no water left in the spent fuel pool of the plant's number-four reactor, resulting in "extremely high" radiation levels.
When auxiliary batteries were exhausted, the plant was without power to continue cooling reactor cores and spent fuel pools.
The condition of the spent fuel pools has been a source of rising anxiety and confusion since the crisis began.
