The shutdown of the ALPS water treatment system at the Fukushima No. 1 plant may have been caused by a rubber mat left in its water tank, Tokyo Electric Power Co. said Sunday.
Just a day after resuming trial runs of the advanced liquid processing system, Tepco detected technical problems with line C of the high-tech radiation-filtering machine at around 10:40 p.m. Friday.
On Sunday, the utility said it had found that a rubber mat used to keep ladders from slipping had been left inside an ALPS tank by workers.
The utility said it was still investigating whether the sheet was the cause of Friday’s shutdown.
ALPS was restarted on a trial basis after midnight Thursday and had processed around 100 tons of toxic water before its suspension.
ALPS extracts most radioactive materials from contaminated water and is seen as crucial in the utility’s efforts to process the vast amount of toxic water that continues to accumulate at the crippled No. 1 nuclear plant. The system operates via three separate lines.
While Tepco’s existing water treatment facility at Fukushima No. 1 can only remove cesium, ALPS can extract 62 different types of radioactive materials, with the exception of tritium.
Tepco and the government had trumpeted the ability of ALPS to process tainted water faster than it builds up at the wrecked complex, which suffered three meltdowns in March 2011. They planned to expand the system and enhance its performance in the future.
Initially, Tepco started a trial run of lines A and B in March, but halted all operations in June after the tank of line A was found leaking because of internal corrosion. While Tepco commenced repairs and investigated the problem, it sped up efforts on line C, which at the time was still waiting to be tried out.
Industry minister Toshimitsu Motegi said Sunday he believes Tepco will soon decide to decommission aging reactors 5 and 6 as well.
Prime Minister Shinzo Abe, during his second visit to the plant on Sept. 19, strongly urged Tepco to decommission the two undamaged units but did not explain why. He also sought a deadline for filtering the stored radioactive water.
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