It was not possible to follow a uniform policy on ageing management of control & instrumentation for a nuclear power plant. Hence individualized approaches are used for different commodities. The first task was to identify the applied major areas, which require replacement/up gradation. This was mainly based on the maintenance feedback over the last two decades. The major areas which required life management/replacement are:

• Indicating alarm meters

• Channel temperature monitoring system

• Certain electronic transmitters & controllers

• Fire alarm & beetle monitoring system

• Protection system

From experience with RAPS it has been seen that a proper type of instrument, selected during the construction stages of a plant can give good performance over a number of years of operation. As revealed from the several case studies, the problem with most of the instruments is mainly due to unavailability of spares. However it is recognized that high temperature and radiation environment does affect the operation of some of the instruments as seen in the case of terminal blocks, located in CTM junction boxes in fuelling machine vaults. Thus normal operating temperature and humidity conditions for each location, especially inside reactor building is to be assessed carefully since this has bearing on the long term performance.

Inside reactor building instrument location is also to be selected carefully so as to avoid high temperature and high radiation environment. Thus it is better to install all field instruments, especially electronic instruments in accessible areas. During up gradation of RAPS-2, we had relocated all electronic instruments to accessible areas.