French energy Group EDF said yesterday that it had been informed by operators of the increase in the concentration of certain inert (noble) gases in the primary circuit at Taishan-1, an EPR supplied by EDF subsidiary Framatome.
Taishan-1 made headlines on Monday after CNN reported that the US government had been working to investigate reports of a “leak” at the 1,660-MW pressurised water reactor unit.
EDF said the presence of inert gases in the primary circuit is a known phenomenon, “studied and provided for” in the reactor operating procedures.
The company said it has contacted local operators to provide its expertise and has called an extraordinary board of directors meeting for management to present all the data and necessary decisions.
EDF owns 30% of Taishan owner and operator TNPJVC in a joint-venture with China General Nuclear (CGN), which holds the remaining 70% majority stake.
Framatome said in a separate statement that they are working with local operators to “support the resolution of the situation”.
CGN issued a statement late on Monday saying that “the continuous monitoring of data” around Taishan shows that the plant and its surrounding environment “meet normal parameters”.
The company said its statement was in response to “some institutions and media which have paid attention to and have inquired about the situation at the Taishan nuclear power station.”
The BBC reported today that an EDF spokesperson confirmed gases that had built up in a component of the plant had been deliberately released.
"We are not talking about contamination, we are talking about controlled emission,” the spokesperson said.
According to the BBC, the spokesperson suggested the gas build up was because of a fuel rod problem.
Gases were collected and treated before being released into the atmosphere in "accordance with regulations", the BBC said.
The release of noble gases by an operating power reactor is a normal effect and it is tolerated in a given operating licence within a certain well-defined limit.
Releases of such gases – which are fission products, mainly isotopes of argon, krypton and xenon, and traces of neon and radon – are permanently under surveillance.
Most of the gases remain contained inside fuel elements, but could occasionally cause small leaks through fuel element cladding, and mix up in the reactor cooling liquid, most often water. A core with less than one percent of the fuel elements leaking noble gases is usually acceptable.
Once in the coolant, noble gases could find ways into the reactor containment, which would require a controlled release.
However, at this stage no information is available to confirm officially the cause of the inert gas build up at Taishan-1.
The International Atomic Energy Agency told the BBC it had "no indication that a radiological incident occurred".
The agency said it had contacted Chinese authorities about the issue.
There are two 1,660-MW EPRs in commercial operation at Taishan since December 2018 and September 2019. Taishan-1 was the first ever reactor of this design to become operational.