Haiyang Unit 3 Cold Tests Complete, Hot Testing and Fuel Loading Next

State Power Investment Corporation cleared a significant commissioning hurdle at Haiyang Unit 3 last week, announcing that cold functional tests at the Shandong province plant were completed successfully on the first attempt, putting hot functional testing and fuel loading squarely in the unit's near-term crosshairs.

SPIC's assessment was detailed and unambiguous. "The cold test confirmed that the four main coolant pumps and their domestically produced frequency converters of Unit 3 are operating normally, the primary loop pressure boundary integrity is good, the pressure-bearing performance meets standards, and the installation quality of related system equipment is excellent," the company said. Completion of the cold tests, SPIC added, lays "a solid foundation for subsequent key milestones such as hot functional testing and reactor fuel loading, as well as high-quality commissioning."

For anyone tracking the CAP1000 commissioning sequence, that language maps directly onto Stage A2 and Stage B of the formal AP1000 commissioning framework. Cold functional testing sits at Stage A1, with the reactor coolant system cold hydrostatic test procedure (RCS-T1P-503) as its centrepiece. Hot functional testing (A2), governed by procedure RCS-T1P-506, comes next: coolant temperatures are raised to simulate actual thermal working conditions, and every safety system gets wrung out before a single fuel assembly goes near the core. Initial fuel loading follows under procedure GW-T1P-601, then initial criticality and low-power physics tests under GW-T1P-611. Haiyang Unit 3 has now cleared the first of those gates.

The result at Haiyang echoes what happened about three weeks earlier at the Sanmen plant, where China National Nuclear Corporation confirmed on February 10 that the primary circuit hydrostatic cold test for Sanmen Unit 3 was also completed on the first attempt. CNNC described that test as "a comprehensive integrity check of the reactor coolant system, the plant's 'artery,' by verifying the pressure boundary of the primary circuit." Two CAP1000 units at two different sites passing their cold tests within the same month is not a coincidence — both units are part of the same State Council-approved expansion from April 2021 that added two new reactors at each of the Sanmen, Haiyang and Lufeng sites.

Haiyang 3 and 4 are CAP1000 units, the Chinese-developed derivative of the Westinghouse AP1000, and join the two existing AP1000 units already operating at the Haiyang site. First safety-related concrete for Unit 3's nuclear island went down in July 2022. Construction on the adjacent Unit 4 started in April 2025. The planned 56-month construction window puts both units on track for full commercial operation in 2027.

The stakes at Sanmen, which offers a direct preview of what completion means operationally, are considerable. CNNC has stated that once Sanmen Phase II units 3 and 4 are commissioned, the plant's annual output will exceed 40 billion kWh, cutting carbon dioxide emissions by approximately 30 million tonnes per year. Comparable figures for Haiyang Phase II would follow a similar scale.

With cold tests behind it, Haiyang Unit 3's commissioning clock is now running on the hot functional test schedule. That phase will be the last major systems verification before fuel goes in.