Fukushima Daiichi Nuclear Power Station is seen in Okuma, Fukushima Prefecture, in this photo taken from a Mainichi Shimbun helicopter in August 2019. (Mainichi/Kaho Kitayama)

TOKYO -- Coolant has been found leaking from pipes in the underground wall of frozen soil surrounding reactor buildings at the tsunami-ravaged Fukushima Daiichi Nuclear Power Station at four locations, its operator said.

According to Tokyo Electric Power Company Holdings, Inc. (TEPCO), the coolant liquid contains calcium chloride, commonly used as a snow-melting agent, and is not an environmental contaminant.

The utility has confirmed that a total of about 20 cubic meters of the coolant has leaked from the pipes. Though the coolant supply to the leaking pipes has been halted, TEPCO does not expect the ice wall to suffer any loss of function. The pipes concerned are between the plant's No. 2 and No. 3 reactor buildings.

TEPCO noticed the problem in late 2019 when the volume in a coolant tank dropped abnormally. Workers examined the ice wall piping and found leaks in the joints. The company is poised to investigate the cause of the leak and replace the problematic parts.

The utility started the operation of the underground wall of frozen soil at the stricken complex in 2016. Coolant chilled to minutes 30 degrees Celsius is circulated through buried pipes, freezing the soil around the reactor buildings to prevent ground water from flowing into the structures.

(Japanese original by Yuka Saito, Science & Environment News Department)