China said on Wednesday that there had been no leak at the Taishan nuclear power station and it had not raised the allowed radiation levels near the plant, responding to a CNN report earlier this week.
CNN reported on Monday that Framatome, the French company that designed the reactors, had said that China's nuclear safety regulator had raised limits on permissible levels of radiation outside the plant in the southeastern province of Guangdong to avoid having to shut it down.
China's Ministry of Ecology and Environment, which oversees the country's nuclear safety watchdog, said on Wednesday that the allegation was "erroneous".
It said the National Nuclear Safety Administration (NNSA) had reviewed specifications for noble gases used in the reactor coolant at Taishan, but this had "nothing to do with the detection of radiation outside the nuclear plant."
An increase in radiation levels was detected in the primary circuit at Taishan's Unit 1 reactor, but it was within the parameters for safe operations, the ministry said.
The increase was caused by damage to the cladding of a small number of fuel rods, which is normal during the production, transportation and loading of fuel, the ministry said on its Wechat social media account.
"Environmental monitoring in the vicinity of the Taishan plant found no abnormal parameters ... showing no leak has occurred at all," the ministry said.
About five out of more than 60,000 fuel rods at the core of the Unit 1 reactor were estimated to have been damaged, amounting to less than 0.01% of the total, far below the maximum designed amount of 0.25%, it said.
The ministry said it will closely monitor radioactivity levels at the reactor and also maintain communications with the International Atomic Energy Agency as well as France's nuclear safety watchdog.
Framatome said on Monday it was assessing the situation at the Taishan plant, which it said was operating within the safety parameters according to data available.
The Taishan project, in Guangdong province, around 200 km (124 miles) from Hong Kong, is a joint venture between the China General Nuclear Power Corporation and France's EDF. Itwas completed in 2019 and consists of two French-designed third-generation reactors.
China currently has 49 reactor units now in full operation, the third highest in the world behind the United States and France.
The International Atomic Energy Agency ranks nuclear safety incidents on a scale from one to seven. China says its plants have never experienced any event higher than two. The Fukushima and Chernobyl disasters both ranked seven.
China's energy regulator - the National Energy Administration - introduced new quality guidelines for the sector at the end of last year.
In a statement issued after the guidelines were published, it said "quality problems" had emerged during the construction of reactors in recent years.
It said the equipment procurement process focused too much on minimising costs and the design process was often inadequate. The regulator did not name any reactors.