For these components preventive maintenance, ISI, and condition monitoring/assessment are possible to mitigate Ageing and are replaced in a planned basis during operating phase. For examples: end shield cooling system equipments, Calandria vault cooling system components, PHT feed pumps, turbine generator system, process water systems piping and equipments, feedwater system piping and equipments, heat exchangers, diesel generators, UPSs, batteries.

A. I.1.1.4. Category 4 — Other SSCs

These are safety related support systems managed by planned preventive maintenance, ISI & conditioning monitoring/assessment and are routinely replaceable. For examples: air compressors & instrument air systems, heavy water recovery dryers, main exhaust fans, transformers, power and control cables.

There are 13 units of PHWRs in operation (refer to Table in Chapter 1 in country report) and another 5 under construction at present. The design details of plants including material specifications and quality control techniques used have seen improvements from plant to plant. Also the local environment control, operating practices and chemistry control have been upgrading from time to time. NPCIL has developed plant specific life management programme(s) to effectively monitor the condition of SSCs and take corrective action in time to maintaining safety margins. To effectively manage the ageing of SSCs the plant needs to have a programme that provides timely detection and mitigation of ageing degradation in order to ensure that the required integrity and functional capability of SSCs are maintained through out the service life and for long term operation.