Document: NRC Regulatory Guide
Document ID: e16da529-b6b4-4fdf-bc3f-7490180363f3
Document Type: regulatory_guide
Title: Environmental Qualification of Certain Electric Equipment Important to Safety for Nuclear Power Plants (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2018/ML20183A423.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.89
CFR Part: 
CFR Title: 

Content:
ined environmental effects of the plant conditions such as radiation, humidity, and temperature that could result in greater degradation of equipment in relation to sequential application of the plant environment under normal, abnormal, and accident conditions. The synergistic effects on materials that are known to have such increased degradation under these conditions should be accounted for when assessing the qualified life. (2) The expected operating temperature of the equipment under service conditions should be accounted for in thermal aging. The Arrhenius equation is considered an acceptable method of addressing accelerated thermal aging within the limitation of state-of-the-art technology. The use of other aging methods should be justified, and the staff will evaluate it on a case-by-case basis. (3) The aging acceleration rate and activation energies used during qualification testing and the basis upon which the rate and activation energy were established should be defined, justified, and documented. Activation energy values should be based on the testing of the specific compound used in the equipment and on the most relevant material property and property endpoint (i.e., failure mechanism). Of note, the activation energy should be selected based on the temperature range of the equipment in service to ensure that the DG-1361, Page 13 equipment remains functional during and following a design-basis event. The selected activation energy values should be traceable to a specific test report for which these values were established, including the specific material property for which the activation energy was developed and how that material property is related to the function of the material in question. Potential nonlinearities and data extrapolation should be minimized by using activation energy values based on material test data obtained within the temperature range of interest. The data should also exhibit a good fit to the Arrhenius relationship within the