EDF Energy confirmed that there was a build-up of noble gases in one of the two reactors’ primary circuits.
It comes after CNN reported that the US government had been assessing reports of a leak at the Taishan plant.
The facility’s Chinese part-owner, China Guangdong Nuclear Power Group, refuted claims of a leak on Monday.
A spokesperson for EDF Energy said that the coating on some of the fuel rods had deteriorated.
The company said gases were collected and treated before being released into the atmosphere in “accordance with regulations”.
Noble gases have a myriad of uses in modern life. For example, neon is a noble gas, and therefore the chemical behind neon lights.
The International Atomic Energy Agency told the Associated Press that it was aware of the reports and it was in contact with its counterpart in China.
“At this stage, the agency has no indication that a radiological incident occurred,” it said.
CNN reported that French engineering company Framatome, which is owned by EDF Energy and designed the reactor, had sent a letter to the US Department of Energy, warning them of the potential leak. It also warned that the Chinese safety authority was raising the acceptable limits for radiation detection outside the plant to prevent it from being shut down.
EDF Energy also announced on Monday that it had called a meeting of the plant’s board.
China Guangdong Nuclear Power Group told state outlet the Global Times that the nuclear plant has operated the reactors strictly in compliance with business licence documents and technical procedures.
All the two reactors’ operation indicators have been in line with nuclear safety regulations and the technical requirements of electricity plants, the company said.
The Taishan plant provides power for the Guangzhou and Shenzhen areas, both major manufacturing hubs.
The region has faced power shortages in recent weeks due to hot weather and lower than normal hydropower supplies from Yunnan province.