Evaluation and Measurement of External Corrosion for Buried Pipes in NPP

Buried pipelines acting as medium transportation carrier play important role in nuclear power plants(NPPs). Usually, their corrosion is controlled by the combination of anticorrosion coating and cathodic protection. However, the risk of pipeline corrosion failure could increase with the increase of service time. Soil corrosion, stray current interference, anticorrosion coating defects and insulation resistivity, cathodic protection potential, pipe defects along the buried pipelines of a nuclear power plant were investigated. Trail hole excavation and verification were carried out according to test results, and the external corrosion state of buried pipelines was evaluated. The evaluation results showed that external corrosion for buried pipes of the plant was controllable, and most of the pipeline cathodic protection was effective, and partial pipeline cathode protection was under-protective. Some anti-corrosion measures of buried pipelines were proposed. Which might provide technical support for extension of NPPs operating permit, and also make reference for the long-life aging management of buried pipelines in other NPPs.