Nodular corrosion of technological channels of the first unit of the Kursk atomic power plant

Corrosion of technological channels made of Zr-2.5%Nb alloy has been studied after 11.5, 12.8 and 13.7 years of service of the first unit. The channel surface, contacting graphite brick work is covered with a homogeneous protective film nearly 3 μm thick. The channel internal surface, contacting heat-transfer water is covered with corrosion products of the primary loop, amounting to 240 g/m2. The channel internal surface sufferers nodular corrosion. Nodule density and sizes depend on neutron flux density and service duration. From both the measurement of dielectric loss angle and the tendency to cathode deposition of metal from electrolyte it was deduced that films contain the areas with high conductivity. X-ray analysis shows that films contain impurities. Within the framework of the electrochemical mechanism a long-term forecast of nodular corrosion development was carried out