"Linglong One" Global First-of-a-Kind Unit Enters Hot Functional Testing Sprint Toward Fuel Loading: Hainan Nuclear Power Details Fully Passive Safety and Multi-Layer Defense Logic

At the Hainan Changjiang Nuclear Power Base, the highly anticipated “Linglong One” multi-purpose modular small pressurized water reactor global first-of-a-kind demonstration project is in the hot functional testing phase, making an all-out sprint toward the goals of first core nuclear fuel loading and grid-connected power generation within the year. As the world's first onshore commercial modular small reactor to pass the International Atomic Energy Agency's generic safety review, its safety margins and engineering design logic have drawn widespread industry attention.

Currently, the civil engineering works of the “Linglong One” unit have been fully completed, and the installation and commissioning of core main equipment are essentially ready. Following the completion of cold functional testing in October 2025, the ongoing hot functional testing is raising the primary loop system temperature and pressure to near actual rated operating conditions, thereby comprehensively verifying the pressure-bearing performance and response reliability of the primary loop pressure boundary, main coolant system, and reactor protection system. After the hot functional testing is successfully concluded, the project will proceed in sequence with nuclear fuel loading, initial criticality testing, and grid-connected power generation, ultimately entering the commercial operation phase.

Hainan Nuclear Power systematically explained the safety defense logic of “Linglong One” from three dimensions: equipment simplification, accident prevention mechanisms, and extreme condition response. At the equipment level, the unit abandons the distributed layout of traditional large reactors and adopts a modular integrated reactor pressure vessel design, significantly reducing the total core loading and radioactive source term. By substantially cutting the number of active main pumps and various complex valves and other mechanical rotating components, the unit effectively reduces the risks of equipment mechanical wear and power supply failure, curbing equipment failures and human error hazards from the physical source.

At the accident prevention level, the demonstration project deeply integrates the design philosophy of “inherent safety and fully passive safety.” Relying on a sensitive reactor protection system, the unit can instantly trigger protection mechanisms when parameters deviate slightly, preventing local anomalies from escalating into severe accidents. The entire plant follows the defense-in-depth principle, implementing a graded risk management and control strategy, achieving early warning and active intervention through physical barriers and operating procedures.

Facing extreme adverse conditions such as station blackout or operator inaccessibility, the multiple passive safety systems of “Linglong One” demonstrate outstanding self-sustaining capability. This reactor type can achieve “no manual intervention required within 72 hours” after a severe accident occurs, relying entirely on inherent physical processes such as gravity, natural convection, and evaporative condensation to remove core decay heat, thereby securing a critical window for on-site emergency response, condition assessment, and external support.

The smooth operation of an advanced project cannot be separated from the soft support of a high-quality operator team. The full-scope simulator built by Hainan Nuclear Power was put into use in 2024, establishing a realistic full-condition simulation training environment. In 2025, the first batch of 34 operators officially obtained first-of-a-kind unit licenses, laying a professional talent foundation for “Linglong One” to transition from hot functional testing to initial fuel loading and subsequent long-cycle commercial operation.