This picture taken on August 21, 2010 shows a MOX fuel storage pool inside the Tokyo Electric Power CO's (TEPCO) Fukushima No.1 plant third reactor building at Okuma town in Fukushima prefecture. The reactor is placed behind the pool. Four of the six reactors at the Fukushima No.1 plant have now overheated and sparked explosions since a massive earthquake and tsunami knocked out cooling systems. Radiation levels near a quake-hit nuclear plant are now harmful to human health, Japan's government said after two explosions and a fire at the crippled facility on March 15, 2011.