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:
Regulations (10 CFR) section 50.49, “Environmental qualification of electric equipment important to safety for nuclear power plants,” require that the licensee provide appropriate EQ for equipment described in these examples, regardless of the safety classification of that equipment. Example 4 applies to some plants, depending on the specific location of control system components. Example 1 The injection of emergency feedwater (EFW) for pressurized-water reactors and the high- pressure coolant injection (HPCI) for boiling-water reactors are safety-related functions. The EFW system and the HPCI system are initiated upon detection of low water level. Automatic termination of these systems upon detection of high water level may also be provided. The high-level trip in some cases has been considered an equipment protection device; however, the inadvertent termination of EFW or HPCI due to misoperation of the level-sensing equipment when subjected to a harsh environment could defeat the safety-related injection function. Thus, the level sensing and electric equipment associated with automatic termination of the injection should be environmentally qualified. Example 2 In some cases, the electrical control system for a pump (for example, a charging pump or an emergency core cooling system pump) will include termination commands on loss of lubrication oil pressure or low suction pressure. These features are provided for equipment protection. Failure of these features, however, would defeat the safety-related function. They should, therefore, be environmentally qualified. Example 3 A safety-related fluid system may have nonsafety-related portions that are isolated from the safety-related portions upon the generation of an engineered safety features actuation signal. Isolation may be performed by motor-operated valves. These valve motor-operators should be environmentally qualified. Example 4 Harsh environments associated with high-energy line breaks (HELBs) could cause