Two men have been hospitalized after they were exposed to radioactive liquid while cleaning a water filtration facility at the wrecked Fukushima nuclear plant, the plant's operator said Thursday.

The two workers, one in his 20s and the other in his 40s, are employees of a partner firm of Tokyo Electric Power Company Holdings Inc. and have been admitted to the Fukushima Medical University's hospital to be decontaminated and put under observation, though they did not sustain any visible injuries or complain of ill health.

File photo taken on Aug. 24, 2023, shows the Fukushima Daiichi nuclear power plant in Fukushima Prefecture. (Kyodo)

The exposure occurred when they were cleaning piping at TEPCO's filtration facility, called the Advanced Liquid Processing System, designed to treat water used in cooling nuclear fuel that remains at the plant.

A hose channeling contaminated solutions came loose, spraying the liquid on five workers, the company said.

On one of the victims, 6.6 millisieverts of beta ray was detected, exceeding a limit of 5.0 millisieverts set for cleaning work at the plant, according to TEPCO. The contaminated liquid seeped through his protective suit, exposing his entire body except his face to radiation.

The beta ray reading on the other victim's protective suit was 1.6 millisieverts, having had his hands and lower body exposed to the substance, TEPCO said. The two men were not wearing a waterproof outer layer as is required for such cleaning work, it added.

Both men were exposed to 0.11 millisieverts or less of gamma rays, below a 0.6 millisievert limit set by TEPCO.

The two men underwent decontamination procedures at the plant but their radiation levels did not come down sufficiently, the company said.

Decontamination of their skin continued at the hospital, where the two men are expected to stay for some time while they are put under observation at least two weeks, TEPCO said.

Water treated by TEPCO's Advanced Liquid Processing System has been stored at the complex, which was crippled by a massive earthquake and tsunami in 2011 and began being released into the sea in August.

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