The IAEA statement was released hours after Tepco temporarily shut down the coolingsystem in the second unit's spentfuel pool following the discovery of dead rodents near a transformer.
The systemcooling water which contained spent - but still highly radioactive - nuclear fuel rods failed and it took engineers some 30 hours to repair the damage.
In early April, the coolingsystem at one of the pools containing spent - but highly radioactive - fuel rods in reactor number three broke down for about three hours.