CGN, which owns 70% of the joint venture, said in a statement on Friday that after consultations between Chinese and French technical experts the decision had been taken to shut the reactor.

It said the unit was safe, under control, and evacuation had started.

"At present, a small amount of fuel damage has occurred during the operation of Unit 1, but it is still within the allowable range of technical specifications, and the unit can continue to operate stably," it said in a statement.

Engineers would now seek to locate the cause of the fuel damage and replace the damaged fuel, CGN said.

"This decision by the operator TNPJVC is in line with what EDF would have done in France with regard to its procedures for operating the French nuclear fleet," EDF said in a statement.

State-controlled EDF said in mid-June it was examining a potential issue at the nuclear power station linked to a build-up of inert gases.

U.S. news network CNN reported last month that the U.S. government was looking into reports of leaks and a potential radiological threat.

EDF clarified then that the measurements of krypton and xenon, which had affected the primary circuit of reactor No.1 of the Taishan plant, were below maximum levels authorised in China.

China said there was no leak, and denied a report that it had raised limits on permissible levels of radiation outside the plant.

The Taishan reactor is the first French-designed Evolutionary Power Reactor (EPR) to become operational. The technology is also being deployed in France, Finland and at the Hinkley Point C project in Britain.

(Reporting by Benjamin Mallet; Writing by John Irish; Editing by Jan Harvey)