A NPP comprises a large number of structures, systems and components and these need to be maintained in a good state of repair for safe and efficient operation. Maintenance can be largely divided into preventive, predictive and breakdown maintenance. All preventive maintenance activ­ities should be well planned according to manufacturers’ recommenda­tions and executed by well-trained personnel. These schedules shall be suitably revised from time to time based on actual experience. Modern NPPs have sufficient redundancy for equipment and instrumentation items that are safety related or which are needed to be taken out of service for maintenance or calibration with the NPP in operation. Some of this equip­ment or components may be radioactively contaminated and hence will have to be decontaminated prior to maintenance work. Where this is not possible, maintenance may have to be done in shops that are equipped to handle contaminated parts. For predictive maintenance, the components have to be kept under surveillance to monitor any degradation such as by condition monitoring techniques or by trending their performance. Maintenance work is then done to prevent breakdown while in service. For certain redundant safety-related components the technical specifica­tions for operation prescribe the allowed outage time. The plant mainte­nance groups should be well equipped to complete maintenance work on such items and return them to service within the permitted time to avoid forced shutdown of the NPP.

From the foregoing it can be seen that a high level of technical compe­tence for all types of maintenance work must be developed in the plant staff. This can be achieved by getting some personnel trained in mainte­nance at other NPPs of similar design and by equipment manufacturers. These personnel in turn should train the larger number of maintenance personnel at plant site. For overhauling some of the equipment of a special­ized nature such as the turbine generator, it may be necessary to engage the manufacturer’s personnel during planned outages of the NPP. However, the overall responsibility for getting the work carried out and bringing the equipment back to service must rest with the plant personnel. Several maintenance activities are undertaken during planned outages such as the refuelling outage. The duration of such outages and consequently the plant load factor is heavily dependent on the capability of the maintenance per­sonnel to complete the work in a timely manner while maintaining a high level of quality in the work performed. It must be remembered that a well — designed and well-operated NPP can give plant load factors in excess of 90% but this is possible only when it is maintained by personnel with a high level of technical skills and in the most professional manner.