Power was restored to part of the cooling system at Japan's tsunami-hit Fukushima nuclear plant. The ponds cool the fuel (which generates intense heat) and provide shielding from radiation. The spent fuel remains in the ponds for a year or more.The temperature of water inside the cooling pool at reactor 3 was 15.1C, well below the safety limit of 65C. This suggested that the spent fuel remained stable and did not pose an immediate danger to the environment. The power cut in March 2013 shut down cooling systems for four spent fuel ponds at reactors 1, 3 and 4, although cooling for the reactors themselves was not affected. Possibly, a rat had damaged the electrics which caused a short circuit in a switchboard and triggering the power cut.
On 11 March 2011, an earthquake and tsunami severely damaged the plant. The mighty waves severely crippled cooling systems for the reactors, resulting to meltdowns at three of them.
Since then Engineers have tried to stabilise the plant but years of work are still remaining to fully contain the disaster and tackle its effects.