"There is no abnormality in the radiation environment around the nuclear power plant. Its safety is guaranteed," foreign ministry spokesperson Zhao Lijian told a news briefing in Beijing.
On Monday, CNN reported that the French company which helps operate the nuclear plant in southern Guangdong province had warned Washington of an "imminent radiological threat."
The warning included an accusation the Chinese safety authority was raising the acceptable limits for radiation detection outside the plant in order to avoid having to shut it down, according to a letter from French firm Framatome to the US Department of Energy, obtained by CNN.
Responding to the report on Tuesday, Zhao said the Taishan plant was fully compliant with all technical requirements.
"China attaches great importance to nuclear safety and has established a nuclear safety supervision system that is in line with international standards and national conditions," he said. "China's nuclear power plants as of now have maintained a good operating record. There have been no incidents affecting the environment and public health."
However, Zhao declined to answer follow-up questions regarding Framatome's language in its warning to US officials, specifically, its use of the term "imminent radiological threat," and the suggestion that Chinese authorities had raised acceptable limits of radiation for the plant and its surrounding area.
In a statement on its website Sunday, the plant's owners also maintained that environmental readings for both the facility and its surrounding areas were "normal."
The two nuclear reactors in Taishan are both operational, the statement said, adding that Unit 2 had recently completed an "overhaul" and "successfully connected to the grid on June 10, 2021." It did not define why or how the plant was overhauled.
Despite the alarming notification from Framatome, which is mainly owned by French utility company Electricite de France (EDF), the Biden administration believes the facility is not yet at a "crisis level," a source told CNN.
EDF holds a 30% stake in the power plant's owner and operator, TNPJVC -- a joint venture with state-owned China General Nuclear Power Group.
Framatome had reached out to the US in order to obtain a waiver that would allow them to share American technical assistance in order to resolve the issue at the Chinese plant.
US officials have been monitoring the situation and believe it does not currently pose a severe safety threat to workers at the plant or Chinese public. But the concern was significant enough that the National Security Council held multiple meetings last week.
The Biden administration has discussed the situation with the French government and their own experts at the Department of Energy, sources said. The US has also been in contact with the Chinese government, US officials said, though the extent of that contact is unclear.
In a statement to CNN on Friday, Framatome acknowledged it "is supporting resolution of a performance issue with the Taishan Nuclear Power Plant in Guangdong Province, China."
"According to the data available, the plant is operating within the safety parameters. Our team is working with relevant experts to assess the situation and propose solutions to address any potential issue," the statement added.
On Monday, French utility company EDF said in a statement it has been informed of an increased concentration of "noble gases in the primary circuit" of reactor number 1 of the Taishan nuclear power plant.
EDF said "the presence of certain noble gases in the primary circuit is a known phenomenon, studied and provided for in the reactor operating procedures," but did not elaborate on gas levels.
Later on Monday, a spokesperson for EDF said the increased levels of radiation were caused by a "degradation of the housing of the fuel rods."
The spokesperson affirmed that the levels of radioactivity observed at the plant were below the threshold stipulated by the Chinese authorities, adding the affected housings are the first of three containment barriers between the rods and the atmosphere.
The spokesperson noted the risk of a potential leakage in the rod housing was first discussed following a planned refueling outage in October 2020 after initial measurements led to suspicions of a "lack of tightness" in the housings.
However, the spokesperson stressed that without a full analysis, it is too early to confirm whether a complete shutdown of the reactor is needed, adding that EDF currently has no information regarding the origin of the rod housing degradation.