Rigorous requirements, precautions essential to keep power plant running

Outside the main control room of the under-construction Unit 5 at the Lufeng nuclear power project, the hum of machinery never stops. Workers in hard hats stream past scaffolding, their footsteps echoing through corridors as the site slowly transforms from steel and concrete into a functioning power station.

The rows of glowing digital displays inside a full-scope simulator tell the story of China's most advanced domestic reactor design. Here, the Hualong One's safety philosophy is etched into every circuit and screen — a sophisticated interplay of digital control, layered redundancy and the promise of years of operator training, all converging to safeguard the unit.

Units 5 and 6 adopt the Hualong One technology with China's independent intellectual property rights. Unit 5 broke ground in September 2022, and Unit 6 followed almost a year later in August 2023.

In the Unit 5 main control room, shift supervisor Yang Shouning said the facility is designed to address any emerging situations.

Large display panels show overall unit status, while digital workstations are used by the nuclear island operator and the conventional island operator.

There are four operator workstations, which are mutually redundant, Yang said. The front two have operation authority during normal use, while the rear two are read-only. If the front workstations fail, operators can switch to the rear workstations.

The redundancy continues beyond the workstations. In an emergency situation, an emergency control panel can directly operate the plant's safety systems. "It effectively provides a quicker means of activation," Yang said.

He added that when all digital operator workstations fail, the auxiliary control panel can still operate normally. Additionally, in the event of software logic failure in the protection system, the human-machine interface panel remains functional. Even under the most extreme power loss conditions, the severe accident control panel continues to operate properly.

If a fire or other causes make the main control room unusable, operators can move to a Remote Shutdown System equipped with the same control capabilities as the digital workstations in the main control room, he said.

The nuclear power plant is designed under the principles of moderate automation and controllable operation, rather than full-scale automation.

Li Weitao, manager of the training department at CGN Lufeng Nuclear Power Co, said that manual operation modes are retained for systems with no urgent response requirements, so as to avert hidden faults and incorrect operation risks caused by excessive automation.

For nuclear safety-related equipment, strict procedures and confirmed safe status matter more than a superficial appearance of automation, he added.

Li said that nuclear plant operators must fully master the principles of power station equipment as well as operational skills before assuming shift duty. The Lufeng nuclear project's training center has put into operation a full-scope simulator for Units 5 and 6, and two additional simulators are being built.

The simulator is a one-to-one replica of the real main control room, from the human-machine interface and automatic control systems to the physical layout. The only difference, Li said, is that pipes, valves, pumps and the reactor are simulated by computer models that reproduce how the plant responds after each operator action.

New university graduates usually spend about three years at the plant learning equipment, processes and field conditions before they can be selected as trainee operators, Li said. Simulator training then lasts about a year, including 14 to 16 weeks of courses covering normal operation, faults, transient conditions and accidents.

Licensing is demanding. Trainees must pass an eight-hour written examination, a simulator examination, and an oral examination of about 45 minutes before applying for a reactor operator license from national authorities, Li said.

After receiving the license, he said an operator must accumulate about three years of licensed shift experience before becoming eligible to test for a senior operator license.

Training does not end after licensing. Licensed operators must complete annual refresher training, including 16 hours of theory and three weeks on the simulator, Li added.

The fastest path from university graduation to becoming a shift supervisor usually takes 10 to 12 years. The position carries high authority because the shift supervisor coordinates plant resources during the shift.

Lufeng generally staffs a new unit with about 60 to 70 licensed operators, Li said. The shift system usually has six operating crews, with three working on shifts, two resting and one in training every day.