Plant life extension program for Indian PHWR power plants - Actual experience and future plans

The Nuclear Power Corporation of India Limited (NPCIL) is responsible for design, construction and operation for all nuclear power plants in India. In the earlier Indian PHWRs zircaloy-2 has been used as coolant tube material, which is observed to have useful life of only about 10 full power years. Reactors at Rajasthan-1 and 2 Madras-1 and 2 Narora-1 and 2 and Kakrapara-1 require en-masse coolant channel replacement at least once in their lifetime. For subsequent reactors from Kakrapara-2 onwards the coolant tube material has been upgraded to Zr 2.5% Nb. En-masse coolant channel replacement and other life extension work have been carried out successfully in Rajasthan Unit-2 (RAPS-2). Work for en-masse coolant channel replacement and plant life extension for Madras unit-2 (MAPS-2) has been taken up since January 2002. Since the coolant channel replacement work requires a long plant outage, this opportunity is also used to extend life of existing systems as well as upgradation work. This life extension and upgradation program is based on the results of detailed in service inspection, evaluation of performance of critical equipment, obsolescence and other strategic reasons. This paper discusses in brief the experience of RAPS-2 in carrying out the above jobs as well as the strategies being adopted for MAPS-2 and future reactors. (author)