Tokyo Electric Power Co. halted the operations of all three advanced radioactive water cleanup systems, collectively called Advanced Liquid Processing System, or ALPS, at the Fukushima No. 1 nuclear plant on Tuesday.
Tepco made the decision after it found that one of the systems, called B, was not functioning properly.
Water samples from System B on Monday showed that levels of beta ray-emitting radioactive substances, such as strontium-90, only dropped to several tens of millions of becquerels from several hundred million becquerels, instead of decreasing to several hundred becquerels.
Tepco suspended water decontamination work with the other two systems as well due to concerns about similar problems.
With its daily processing capacity of 750 tons, ALPS is regarded as a key element in containing the radioactive water crisis at the crippled plant. However, due to a series of problems, Tepco has yet to start full operations.