Water regime and corrosion problems of the secondary circuit of WWER type nuclear power plants

Secondary circuit measurements in the V-1 nuclear power plant in Jaslovske Bohunice showed a high iron concentration in feedwater. The inspection of the machinery confirmed that this was the result of erosion corrosion. The steam pipes after the high pressure turbine stage prior to the steam separator, and the pipes of heat steam at the inlet of the first superheater stage were attacked into the largest extent. The steam pipes were repaired by lining with austenitic steel sheets at the most exposed points, and this treatment was incorporated in the production of new equipment for other power plants. Only part of the corrosion product sources in feedwater, however, was removed. Therefore, brass as the material for the condenser pipes was recommended to be replaced with titanium alloys, which would allow increasing the pH value of the secondary circuit water, thus significantly reducing the erosion corrosion in the circuit. Also, the need would be eliminated to use austenitic materials for the secondary circuit pipes and components. In addition, the period of the cleaning of the steam generator secondary side would be extended. (Z.M.)