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:
iques to simulate aging may become more effective. Experience suggests that consideration should be given, for example, to a combination of the following: (1) preconditioning of test samples employing the Arrhenius theory; (2) concurrent radiation and thermal aging or sequential aging, as well as the order of radiation and thermal aging, based on which produces the worst-case degradation; and, (3) surveillance, testing, and condition monitoring of selected equipment specifically directed toward detecting those degradation processes that are not amenable to DG-1361, Page 17 preconditioning and that could result in common-cause equipment failure during design basis accidents e. Considerations such as the following should be taken into account when determining the environment for which the equipment is to be qualified: (1) equipment outside containment would generally see a less severe environment than equipment inside containment, (2) equipment whose location is shielded from a radiation source would generally receive a smaller radiation dose than equipment at the same distance from the source but exposed to direct radiation, (3) equipment required to initiate protective action would generally be required for a shorter period of time than instrumentation required to operate during and after an accident, and (4) analyses taking into account arrangements of equipment and radiation sources may be necessary to determine whether equipment needed for mitigation of design basis accidents other than LOCA or high-energy line breaks (HELB) could be exposed to a more severe environment than the plant-specific LOCA or HELB environments. f. Electric equipment to be qualified in a nuclear radiation environment should be exposed to radiation, before testing, that simulates the calculated integrated dose (normal and accident) that the equipment must withstand before completion of its intended safety functions. Cobalt 60 or cesium 137 would be acceptable gamma radiation sources for