Contribution of SG Degradation Mechanisms to RIKT Behaviour

Abstract

Degradation of steam generators has a significant effect on CANDU heat transport system effectiveness and the overall efficiency of a nuclear power plant. Steam generator degradation results in an increase in the reactor inlet header temperature (RIHT), which has to be kept below an upper limit to avoid dryout of the fuel. Therefore an understanding of steam generator degradation mechanisms is needed to avoid plant deratings. In this paper, various steam generator degradation mechanisms are identified and their effect on the RIHT quantified using field data and numerical modelling. Thermal performance of CANDU steam generators has been mostly affected by a combination of divider plate leakage and tube-bundle fouling. An analysis of plant data indicates that CANDU 6 steam generators are fouling at the rate of 2.05*10^-6m2 degrees C/W per EFPY, of which the majority of this is attributed to primary-side fouling.