Fouling and corrosion problems of raw water circuits of FBTR and RAPS

Fouling and corrosion are two major operational problems in the heat exchangers of power plant cooling system. Nuclear power plants are more susceptible to fouling induced corrosion than their thermal counterparts due to their inherent design characteristics like long gestation period, multiple standby systems etc. Problems such as flow blockage of pipes, pipe punctures and relatively high corrosion rates were experienced in the service water system of the Fast Breeder Test Reactor (FBTR) at Kalpakkam. Similarly about 1100 condenser tubes in Rajasthan Atomic Power Station (RAPS) II have failed during two years of operation resulting in leakage (80-2100 l/h) of condenser cooling water into the boiler feed water. As a result of this total dissolved solids (TDS), chloride, total hardness and silica content in the boiler water remained above the specified limit for a good amount of time. In view of the possible linkage between water quality and microbial activity resulting in material degradation, experiments on water quality (Palar subsoil, open reservoir, RAPS intake and out fall), corrosion rate measurements, microbiological counts and experiment on chlorination vs bacterial mortality were carried out with a view to study the effectiveness of existing treatment programme in FBTR cooling system and also to look for possible linkage between water quality and condenser tubes failures of RAPS. 10 refs., 2 tabs., 1 fig