A hydrogen explosion at the Fukushima No. 1 plant last March sent a 35-ton machine plunging into the spent-fuel pool of reactor 3, which uses highly dangerous mixed oxide fuel, Tokyo Electric has reported.
“We believe the machine fell into the pool when the (hydrogen) explosion occurred, but we have not found any indication it damaged the pool’s walls and caused any leaks, or that it damaged the spent fuel,” Junichi Matsumoto, a spokesman for Tokyo Electric Power Co., told a news conference Friday.
The utility said engineers placed an underwater camera in the pool earlier Friday to prepare for the removal of its spent fuel rods. The No. 3 reactor is the only one at the crippled power station that was powered by the plutonium-uranium MOX.
Tepco released a photograph that appears to show part of the machine, which used to hang directly above the 11.8-meter-deep pool and was used to insert and remove fuel rods, resting on storage racks for the fuel rods.
Tepco also said that shortly after 1 a.m. Friday it was forced to stop injecting nitrogen into the containment vessels of the three reactors hit by meltdowns. The injections resumed around 10 a.m. via a backup system and no change in their hydrogen concentrations was detected, the utility said.
Tepco said it was the fourth time since March that it has been forced to suspend nitrogen injections, which are vital to prevent further hydrogen blasts.
Meanwhile, another image released by Tepco shows what looks like the building’s iron frame — all that remains after the hydrogen explosion ripped through it last year.