BEIJING — Unusual activity at a nuclear power reactor in China has drawn international attention, as two French companies involved in the plant acknowledged problems Monday but said they could be handled safely.

The companies were responding to a report by CNN on Monday that Framatome, one of the companies, had sought help from the United States, citing an “imminent radiological threat” at the Taishan Nuclear Power Plant in Guangdong province.

EDF, France’s main power utility and part owner of the power plant, said in a statement that certain gases had accumulated in the water and steam surrounding the uranium fuel rods at the heart of the reactor. But it said that the reactor had procedures for dealing with such a buildup of gases, which it described as a “known phenomenon.”

Framatome, an EDF affiliate and the builder of the reactors, said that there had been a “performance issue” but that the plant was operating within its safety parameters. In China, the power plant said in a statement Sunday night that no leak into the environment had been detected.

The state-run China General Nuclear Power Group, better known as CGN, owns 70% of the Taishan plant, and EDF owns the rest. The French companies and the Chinese plant did not immediately respond to requests for interviews. China’s Foreign Ministry was closed Monday for a national holiday. An officer answering the phones there said no one was available to comment on the Taishan nuclear power plant.

The plant has two nuclear reactors that were built to French designs on the coast of southeastern China. The reactors, one of which started commercial operation in 2018 and the other in 2019, are about 80 miles southwest of Hong Kong and 30 miles south of Taishan itself, a town of 500,000.

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In its statement, EDF said it had called for a special meeting of the board of the joint venture that operates the power plant “to present all the data and the necessary decisions.”

Patrick H. Regan, a nuclear scientist at Britain’s National Physical Laboratory and at the University of Surrey, said the difficulty described by EDF appeared to be a leak of gases from one or more fuel rods into the water and steam that surround the rods in the reactor. The most likely gas to have been detected is a radioactive isotope of xenon, he said.

The problem with that isotope is that its presence may prompt reactor operators to remove limits on how fast the reactor runs. That can make the reactor more vulnerable to overheating, Regan said.

“It’s almost pressing the accelerator” in a car, he said.

This is not a new problem in nuclear reactors, sometimes occurring if a fuel rod has a crack. It is typically handled by removing the fuel rods from the reactor and letting the xenon isotope gradually dissipate over a couple of days through radioactive decay.

The other option is to keep running the reactor and vent traces of the xenon gas from the reactor into the atmosphere. Regulators around the world give each reactor a small annual allowance of radioactive releases. Venting can allow the reactor to continue operating, but may trigger regulatory reviews.

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Several details from the CNN report, which cited unnamed sources, could not be verified. CNN also reported that Framatome had said that Chinese authorities had raised the acceptable limits for radiation releases around the plant to avoid having to shut it down. The province is already suffering from electricity shortages.

Michael Friedlander, a former operator at three nuclear power plants in the United States, said many nuclear utilities around the world used to keep operating with leaking fuel rods and occasional venting of xenon gases. But that ended in the West in the 1990s as utilities sought to minimize even trace releases of radiation, partly to protect their own workers.

“The global best practice is to shut down and change out the leaking fuel rods as soon as practical,” he said. “This normally would occur way, way, way before you approach a regulatory limit.”

It appeared that the reactor had released gas in the past. The Hong Kong government, which stays in close contact with the management of nearby reactors, had said April 8 that there had been an incident three days earlier with the exhaust gas system at the same reactor. The incident resulted in a tiny release of a gas, but the details of which gas were not disclosed.

The release was only equal to 0.00044% of the annual limit for the power plant’s releases of that gas, however, the Hong Kong government said.

According to CNN, Framatome had contacted the U.S. government about getting help with operations at the power plant. CGN, the Chinese nuclear company, is on the U.S. Commerce Department’s Entity List of foreign enterprises with which U.S. companies are forbidden to do business.

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As part of the request for advice, Framatome had asked the United States to waive its limits on nuclear assistance to China on the basis that it met a legal test of an “immediate radiological threat,” the report said. The United States has a lot of early experience in managing the trade-offs of venting traces of gases from reactors and continuing to run them.

It is unclear how the company defined the threat. Some of the most sensitive radiation detection equipment tends to be at nuclear power plants, so as to provide early warning of any leaks. CLP, a Hong Kong-based electricity multinational that partly owns a nuclear power station in Shenzhen, near Hong Kong, said Monday in an emailed response to questions that it had not observed any abnormal radiation.

The U.S. Embassy in Beijing had no immediate comment.This article originally appeared in The New York Times.