Objective The material of the main pipeline of the primary circuit in nuclear power plants is often made of cast austenitic stainless steel, which increase the material brittleness due to thermal aging after a long period of high-temperature service, posing a threat to the safety of the primary circuit. As an effective method for studying thermal aging, thermoelectric potential technology. Studying thermoelectric potential assessment technology can improve the thermal aging management level of the main pipeline and further ensure the safe operation of the main pipeline.

Method In order to study the evaluation method of the thermal aging, the impact energy and thermal potential (TEP) of multiple samples of materials after thermal aging were tested, and a relationship between the two was established; the ferrite content and distribution of the piping material were studied, and the influence of the differences in ferrite content on the assessment of thermal aging was revealed.

Result It was found that the distribution of ferrite content of the main pipe materials has differences in different areas, and the internal and external crystal structures are also significantly different. These factors have an impact on the thermal potential of the material, and an evaluation model between the thermal potential and the thermal aging was established to quantify the influence of the differences in ferrite content on thermal aging evaluation.

Conclusion When thermoelectric potential technology is applied to the thermal aging assessment of the main pipeline, the differences between the casting process of the main pipeline and the field test and experimental data should be fully considered. Clarify the differences between field test data and experimental data. Based on sufficient experimental data, adjust the data validity and establish a more refined model, so as to improve the accuracy of the thermal aging assessment results of the main pipeline.