Fangchenggang Nuclear Power Station Unit 2 Completes First Ten-Year Overhaul

On the morning of August 25, Unit 2 of CGNPC Fangchenggang Nuclear Power Station successfully synchronized to the grid on its first attempt following the 7th overhaul, marking the completion of the F207 overhaul undertaken by CGNPC Service Maintenance Company. This overhaul was the first ten-year overhaul since Unit 2 was put into commercial operation. The maintenance process achieved the goal of “no indicator events in safety, quality, and schedule” and made breakthroughs in charging pump maintenance and nuclear-grade socket welding operations.

During this overhaul, the nuclear-grade socket welding project was implemented on-site for the first time. To ensure work quality, the maintenance team completed preparatory work in advance, including welding procedure qualification certification, skill qualification process card review and submission, test piece welding, and non-destructive testing, all of which passed acceptance. After on-site welding was completed, radiographic testing passed on the first attempt, verifying the team's capabilities in nuclear-grade welding practice, personnel qualification management, and technical system development.

At the nuclear island valve maintenance site, the static equipment team completed full-scope maintenance of nuclear island valves and, for the first time, performed nuclear-grade welding valve maintenance for the essential building water system. During the same period, the team also advanced maintenance tasks for ventilation systems, piping, snubbers, and supports, providing assurance for the seismic stability and safe operation of nuclear island equipment.

The rotating equipment team completed disassembly and overhaul of key primary equipment such as the residual heat removal pumps, and for the first time undertook the motor maintenance task for Pump 3 of the chemical and volume control system horizontal double-casing centrifugal pump. This equipment features a complex structure and requires high assembly precision. Maintenance personnel verified key parameters step by step through disassembly, cleaning, reassembly, and test operation, ultimately meeting all test indicators and ensuring the equipment was ready for operation.

The instrumentation and control team completed the installation of leak detection probes in the work area at the bottom of the steam generator. This task involved equipment disassembly, alignment, wiring, and commissioning in a radiation environment, placing high demands on on-site organization and risk control. Upon completion, the work further enhanced the condition monitoring capability of the relevant equipment.

This overhaul also involved high-risk critical procedures such as the lifting of the nuclear island reactor vessel head and the opening and closing of the T-beam cover plates. Before commencement, the vessel team conducted technical briefings and risk reviews, clarifying personnel positioning, coordination signals, and on-site command procedures. During the operations, precise alignment of critical components was achieved, ensuring the major lifting tasks were executed as required.

In terms of equipment modification, the modification team focused on completing the replacement of the hydrogen detection system, while also advancing ventilation system optimization, signal redundancy addition, power supply circuit upgrades, and cabinet temperature control modifications. These modifications help address shortcomings in the original systems and enhance the unit's resilience against fault risks.

The F207 overhaul covered multiple tasks including in-depth maintenance, hidden hazard remediation, and equipment upgrades, and also tested the maintenance company's comprehensive capabilities in high-risk operations, new equipment maintenance, radiation dose control, and cross-disciplinary coordination. The experience gained will support the safe and stable operation of Unit 2 at Fangchenggang Nuclear Power Station in the next fuel cycle and provide a reference for similar ten-year overhaul projects.