Overview on performance degradation behavior of 20Cr25NiNb steel for gas cooled reactor cladding during service

In this paper, the performance degradation behavior of fuel cladding material 20Cr25NiNb for the British Advanced Gas Reactor (AGR) is reviewed in detail, which is a strong guideline for the material selection of supercritical carbon dioxide cooled reactors. The degradation behavior during in-core service mainly includes high-temperature creep, thermal aging and mechanical property degradation caused by neutron irradiation (fission gas products, helium embrittlement and irradiation sensitization) and CO2 (oxidation and carburizing). Long-term service in AGR leads to coarsening of the second phase and precipitation of harmful phases such as sigma, leading to performance degradation of the cladding. A point that should require special attention is that intergranular stress corrosion cracking (IGSCC) and intergranular attack (IGA) problems occur during wet storage of spent fuel.

Automated summary

This paper reviews in detail the performance degradation behavior of fuel cladding material 20Cr25NiNb for the British AGR and provides valuable guidance for the material selection of supercritical carbon dioxide cooled reactors. Degradation behavior during in-core service includes high-temperature creep, thermal aging, mechanical property degradation caused by neutron irradiation and CO2 corrosion. Long-term service in AGR results in coarsening of the second phase and precipitation of harmful phases, leading to degradation of the cladding performance. Intergranular stress corrosion cracking (IGSCC) and intergranular attack (IGA) issues occur during wet storage of spent fuel, which should be carefully addressed.