Document: NRC Regulatory Guide
Document ID: cdc706d5-60ed-40a4-b55a-9771904107a7
Document Type: regulatory_guide
Title: Seismic Qualification of Electric and Mechanical Equipment for Nuclear Power Plants (Rev. 4)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1809/ML18093A675.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.100
CFR Part: 
CFR Title: 

Content:
e valve stroke times under zero differential pressure and flow conditions did not detect deficiencies that could prevent MOVs from performing their safety functions under design-basis conditions. Both regulatory and industry research programs later confirmed weaknesses in the performance of MOVs. Responding to weaknesses found in the initial design, qualification, testing, and performance of MOVs, in June 1989, the NRC issued GL 89-10, “Safety-Related Motor-Operated Valve Testing and Surveillance” (Ref. 15), which directed licensees to (1) ensure the capability of MOVs in safety-related systems to perform their intended functions by reviewing MOV design bases, (2) verify MOV switch settings initially and periodically, (3) test MOVs under design-basis conditions when practicable, (4) improve evaluations of MOV failures and necessary corrective action, and (5) trend MOV problems. The NRC staff evaluated NPP MOV programs by conducting onsite inspections of the design-basis capability of safety-related MOVs. In support of the regulatory activities to ensure an MOV design-basis capability, the NRC conducted a research program to test several MOVs under normal flow and blowdown conditions. The NRC summarized the results of this MOV research program in Information Notice (IN) 90-40, “Results of NRC-Sponsored Testing of Motor-Operated Valves,” dated June 5, 1990 (Ref. 16). The tests revealed the following: • More thrust was needed to operate gate valves than that predicted by standard industry methods. • Some valves were internally damaged under blowdown conditions, and the valves’ operability was unpredictable. • Static and low-flow testing might not predict valve performance under design-basis flow conditions. • During valve opening strokes, the highest thrust might be needed at unseating or in the flow stream. • Partial valve stroking did not reveal the total thrust needed to operate the valve. • Torque, thrust, and motor-operating parameters were