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The Fukushima Dai-ichi nuclear power plant operated by Tokyo Electric Power Company (TEPCO) in Okuma town, northeastern Japan, on 14 Feb 2021, a day after a strong earthquake hit. AP

The operator of the wrecked Fukushima nuclear power plant said Monday that two seismometers at one of its three melted reactors have been out of order since last year and did not collect data when a powerful earthquake struck the area earlier this month. The acknowledgement raised new questions about whether the company’s risk management has improved since a massive earthquake and tsunami in 2011 destroyed much of the plant. The malfunctioning seismometers surfaced during a Nuclear Regulation Authority meeting on Monday to discuss new damage at the plant resulting from a magnitude 7.3 quake that struck the region on 13 February.

Cooling water and pressure levels fell in the Unit 1 and 3 reactors, indicating additional damage to their primary containment chambers. The operator, Tokyo Electric Power Co., has repeatedly been criticized for coverups and delayed disclosures of problems at the plant.

Regulatory officials asked TEPCO at the meeting why it did not have seismological data from the Unit 3 reactor for Saturday’s quake, and utility officials acknowledged that both of its seismometers had failed — one in July and the other in October — and had never been repaired.

TEPCO also said that seismometers at all but two of the reactor buildings that survived the 2011 disaster were submerged by water from the tsunami and have never been replaced.

During Monday’s meeting, regulatory officials said they were concerned about the declining water levels and pressure in the Unit 1 and 3 primary containment chambers because of the possibility that the quake had expanded the existing damage or opened new leakage paths, and urged the utility to closely check for any increased radiation levels in the ground water surrounding the reactor buildings.

TEPCO said no abnormality has been detected in water samples so far.

New damage could further complicate the plant’s already difficult decommissioning process and add to the large amounts of contaminated water being stored at the plant.

Since the 2011 disaster, cooling water has been escaping constantly from the damaged primary containment vessels into the basements of reactor and turbine buildings, where the volume increases as groundwater seeps in. The water is pumped up and treated, then part of it is reused as cooling water, while the rest is stored in about 1,000 tanks.

TEPCO initially reported there was no abnormality at the plant from Saturday’s earthquake. But on Monday, it said about 20 of the tanks had slid slightly due to the quake, a storage container carrying radioactive waste had tilted, and asphalt pavement at the plant was cracked.