Optimising performance at Kuosheng24 November 2015
By focusing on preventive maintenance and modifications, investing in training and taking a proactive approach to asset management, Kuosheng has achieved high-level equipment performance and nuclear safety.
The Taiwan Power Company (TPC), established in 1946, has three nuclear power plants in operation, Chinshan, Kuosheng and Maanshan, whose joint 5144MWe capacity provides 40TWh (18.6% overall) baseload power annually.
Kuosheng is the largest plant, providing 16TWh every year. Its two reactors are rated at 985MWe and began operation in 1981 and 1983. They are General Electric Company designs, with turbine generators manufactured by Westinghouse. Kuosheng has achieved a three-year capacity factor of 94% and an unplanned capability loss factor of 0.53%, and has had only five scrams in last 12 years.
These results meet long-term performance targets from the World Association of Nuclear Operators (Wano).
Kuosheng's equipment performance and safety strategy focuses on four areas:
- Preventive maintenance;
- Maintenance strategy and plant modifications to reduce core damage frequency;
- Highly skilled and motivated workforce and knowledge transfer;
- Long-term asset management.
Preventive maintenance has three aspects:
- Analysing maintenance: A post-refuelling outage review is performed for any equipment failure that occurs within the 90 days following each outage. These events are reviewed to determine what was done or should have been done to prevent them. Corrective actions are taken to prevent future failures. The threshold for inclusion is low and drives the staff to excellence. A recent post-refuelling outage review found three items needing evaluation because of failures within the 90-day window. The cause of the failures was determined, and corrective actions were implemented.
- Using spare components: During a refuelling outage, one piece of equipment is removed and replaced with a spare. After the outage is complete, the removed component undergoes a detailed overhaul in the maintenance or vendor shop. This process is repeated for subsequent refuelling outages. Some examples include spares for main coolant pump motors, turbine control system pump and motors, feedwater pump internals, condensate pump and motors, emergency feedwater pump and motors, boron injection pump motors, valves with actuators, and check valves.
- Managing preventive maintenance activities: Preventive maintenance is the cornerstone of preventing equipment failures. It was identified as the most important contribution to equipment reliability and sustained plant performance. Preventive maintenance tasks are planned in advance. Once the preventive maintenance activity is complete, the owner of the activity identifies and orders the parts needed for the next scheduled maintenance. Any changes to the preventive maintenance activity are identified and implemented in a timely manner.
With regard to reducing the probabilistic risk assessment (PRA) risk, plant modifications were installed before the Fukushima event.For example, the flood protection walls and watertight doors were installed to raise the emergency circulating water protection from 6.9m to 12m. The 4.16kV essential bus power source was improved by installing an additional start-up transformer and a fifth air-cooled diesel generator. Also, the direct current battery capacity was increased from 8 hours to 24 hours.
After the Fukushima event, it was understood that the key to preventing an event becoming an accident is timely response in the main control room. Therefore, a newly corresponding procedure, the Ultimate Response Guideline (URG) was developed, designed to cut off event evolution and take immediate action to prevent core damage. Key to URG is securing the reactor core by emergency depressurisation, containment venting and injecting any available water (even seawater) through any available injection paths. This is a response to reaching any of these three conditions: plant suffered from larger than SSE earthquake and tsunami; station blackout; or loss of ultimate heat sink. The regulator oversees regular practices of these conditions and actions.
To manage knowledge transfer and maintain a skilled workforce integrated training programmes have been established. There is a bias toward hands-on versus classroom training. With very few exceptions, workers stay in the same positions for an extended period. This results in a workforce that is skilled and experienced. The plant staff displays pride in and ownership of their work.
At Kuosheng, all new employees go through initial training at a corporate training institute. The technicians receive six months of training on fundamentals of electricity generation and the engineers undergo six weeks of training on nuclear reactor basics. At the site, the new engineers and technicians are offered six months of training on plant systems and equipment, followed by on-the-job training and additional job-specific training tailored to their position. Training continues after the initial four-year period.
At Kuosheng, maintenance and engineering are in one organisation to promote collaboration in resolving and preventing equipment failures.
The operations department is tasked with system monitoring and trending. The design-engineering organisation is typically located at corporate headquarters.
The system, component, and programme engineering functions reside in the maintenance department. The group is split by mechanical, I&C and electrical functions but with good teamwork. Corrective maintenance work orders are typically completed in 2-3 days, including identification, screening, planning and execution. Engineers, within each maintenance team, prepare repair plans and arrange the resources to execute the repairs.
In long-term asset management, Kuosheng has a proactive approach to planning and replacing safety-related equipment. Safety is the number one priority, partly driven by the regulators, but mostly embedded in employees and processes.
Kuosheng has completed or scheduled the following improvement modifications: replacing the main turbine low-pressure rotor; replacing the unit auxiliary transformer; replacing the 345kV switchyard bus, breaker, and disconnect switch; upgrading digital control systems; and replacing ethylene propylene rubber insulated cables with silicone rubber insulated cables.
TPC makes great efforts to maintain safe and stable operation, with huge manpower and advanced technologies, and keeps improving. This kind of approach is the key to success. ¦