Huaneng Hainan Changjiang Nuclear Power Plant Unit 4 Secondary Loop Combined Hydrostatic Test Successfully Completed

At 04:29 on August 6, 2026, witnessed jointly by Huaneng Changjiang Nuclear Power Company and all participating construction units, the secondary loop combined hydrostatic test of Unit 4 was completed, laying a solid critical prerequisite foundation for the comprehensive implementation of subsequent cold functional tests of the unit.

Hydrostatic test curve diagram

The secondary loop hydrostatic test is the core critical test following the blasting purging process in the unit's secondary loop system, and constitutes a mandatory acceptance procedure during the construction and installation phase of the Hualong One nuclear power unit. The test primarily targets the steam generator secondary side system, main steam pipelines, feedwater system, auxiliary valves, supports and hangers, and all associated piping, comprehensively verifying the overall structural pressure resistance, weld and flange sealing performance, and overall installation construction quality, proactively identifying potential hazards such as leakage, deformation, and insufficient pressure-bearing capacity under high-pressure conditions. It is an indispensable core procedure in transitioning the unit from equipment installation to system commissioning.

To ensure the safe, precise, and on-schedule completion of the secondary loop hydrostatic test of Unit 4, Huaneng Changjiang Nuclear Power Company organized all participating construction units to develop tiered control measures and emergency response plans based on the actual on-site construction progress of Unit 4. The project team refined the step-by-step pressurization procedures, optimized on-site construction logic, dynamically allocated core resources such as test equipment, instrumentation, and personnel, and strictly enforced responsibilities for safety production and quality control. Throughout the test, 24-hour dedicated personnel were on duty, with multi-unit joint monitoring across the entire pressurization, pressure-holding, and depressurization process, strictly controlling key parameters such as pressurization rate, pressure-holding duration, and pressure fluctuation, safeguarding the safety bottom line and quality red line of nuclear power construction throughout the entire process.

Huaneng Changjiang Nuclear Power Company has always adhered to the fundamental principle of nuclear power construction of "Safety First, Quality First," working in unity with participating construction units including CNNC Engineering, CNNC Consulting, and CNNC Fifth Construction Company to tackle challenges collaboratively. The successful completion of the secondary loop hydrostatic test milestone marks the steady parallel progress of Unit 4 construction at Huaneng Changjiang Nuclear Power Company, continuously improving the clean energy supply layout of Hainan Free Trade Port. All project personnel will take this milestone as a new starting point, steadily advancing key subsequent tasks such as system commissioning, cold testing, and hot testing, making every effort to ensure the high-quality and on-schedule commissioning of Unit 4, contributing to the large-scale and high-quality development of Huaneng's nuclear power industry, and continuously contributing nuclear power strength to Huaneng Group's accelerated construction of a world-class enterprise and Hainan Province's development of a new power system.