En-masse boiler heat exchanger replacement jobs in MAPS-1 ' a review of health and safety aspects'

Madras Atomic Power Station (MAPS) Unit-1, a pressurized heavy water reactor, was taken off the grid on 20.8.2003 at 10.1 FP years for Enmasse Coolant Channel Replacement (EMCCR). At MAPS some of the monel tubes of the boiler heat exchangers developed pin holes due to scale formation resulting in ingress of coolant D2O to feed water and led to forced shut down of the unit. It was decided to replace all the boiler hairpins during EMCCR campaign of the unit. In view of the high radiation field and volume of the work involved, control of external exposures to the working personnel was the main focus of attention during the entire campaign. Continuous assessment of radiological conditions and exposure control measures were done during the entire operation and review of workers dose and work technique helped in carrying out the work safely and within the budgeted dose. The health and safety aspects of the job is discussed in this paper. (author)