Document: NRC Regulatory Guide
Document ID: cf64153e-7623-469c-a3f9-b57ba0f5497d
Document Type: regulatory_guide
Title: Reactor Coolant Pump Flywheel Integrity + HISTORY - HISTORY 01/2006 – Periodic Review of Revision 1 – No Issues Identified
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003739936.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.14
CFR Part: 
CFR Title: 

Content:
U.S. NUCLEAR REGULATORY COMMISSION REGULATORY GUIDE OFFICE OF STANDARDS DEVELOPMENT REGULATORY GUIDE 1.14 REACTOR COOLANT PUMP FLYWHEEL INTEGRITY A. INTRODUCTION General Design Criterion 4, "Environmental and Missile Design Bases," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Licensing of Production and Utilization Facilities," requires that nuclear power plant structures, systems, and components important to safety be protected against the effects of missiles that might result from equipment failures. This guide describes a method acceptable to the NRC staff of implementing this requirement with regard to minimizing the potential for failures of the flywheels of reactor coolant pump motors in light-water-cooled power reactors. B. DISCUSSION The flywheels on reactor coolant pump motors provide inertia to ensure a slow decrease in coolant flow in order to prevent fuel damage as a result of a loss of power to the pump motors. During operation at normal speed, a flywheel has sufficient kinetic energy to produce high-energy missiles and excessive vibration of the reactor coolant pump assembly if the flywheel should fail. Overspeed of the pump rotor assembly during a transient increases both the potential for failure and the kinetic energ3T of the flywheel. The safety consequences could be significant because of possible damage to the reactor coolant system, the containment, or other equipment or systems important to safety. Methods of predicting the loss-of-coolant accident (LOCA) overspeed conditions are under continuing investigation. The limit on predicted pump overspeed in the event of a LOCA should be less than the calculated critical speed for failure of the flywheel. The conserva tism inherent in the latter calculation, coupled with a realistic prediction of maximum rotational speed, is considered to provide adequate margin because of the low probability of occurrence of the specific LOCA conditions that would cause such