Cold testing of third Sanmen unit completed

Such tests are carried out to confirm whether components and systems important to safety are properly installed and ready to operate in a cold condition. The main purpose of cold functional tests is to verify the leak-tightness of the primary circuit and components - such as pressure vessels, pipelines and valves of both the nuclear and conventional islands - and to clean the main circulation pipes. The tests mark the first time the reactor systems are operated together with the auxiliary systems.

China National Nuclear Corporation (CNNC) said the completion of cold tests at Sanmen 3 on Tuesday "is a key turning point in the nuclear power plant commissioning process, laying a solid foundation for subsequent tasks such as hot testing and fuel loading startup".

Cold testing will now be followed by hot functional tests, which involve increasing the temperature of the reactor coolant system and carrying out comprehensive tests to ensure that coolant circuits and safety systems are operating as they should. Carried out before the loading of nuclear fuel, such testing simulates the thermal working conditions of the power plant and verifies that nuclear island and conventional equipment and systems meet design requirements.

_{The Sanmen site (Image: CNNC)}

The construction of two new reactors at each of the Sanmen, Haiyang and Lufeng sites in China was approved by China's State Council in April 2021. The approvals were for Sanmen units 3 and 4, Haiyang 3 and 4 and units 5 and 6 of the Lufeng plant. The Sanmen and Haiyang plants are already home to two Westinghouse AP1000 units each, and two CAP1000 units - the Chinese version of the AP1000 - were approved for Phase II (units 3 and 4) of each plant.

"Once the second phase, units 3 and 4, are completed and put into operation, the Sanmen Nuclear Power Plant will generate more than 40 billion kilowatt-hours of electricity annually, equivalent to a reduction of 30 million tonnes of carbon dioxide emissions per year," CNNC noted. "This will be of great significance for optimising the regional energy structure and ensuring power supply."

Two Hualong One (HPR1000) reactors are planned for Phase III (units 5 and 6) of the Sanmen plant.