IMPROVEMENTS IN MOTOR OPERATED GATE VALVE DESIGN AND PREDICTIVE MODELS FOR RELIABILITY IMPROVEMENTS IN NUCLEAR POWER PLANT SAFETY SYSTEMS

MOTOR OPERATED GATE VALVE OPERABILITY PROBLEMS AND FAILURES AT NUCLEAR POWER PLANTS ARE A MAJOR SAFETY CONCERN AS STATEDIN NRC IE BULLETIN 85-03 AND GENERIC LETTER 89-10. THIS PROPOSAL IS AIMED AT IMPROVING GATE VALVE PERFORMANCE BY (1) DEVELOPING COMPREHENSIVE PERFORMANCE PREDICTION MODELS FOR USE OVER A RANGE OF OPERATING CONDITIONS, (2) DEFINING LIMITS, BASED ON SPECIFIC DESIGNS, BEYOND WHICH EXTRAPOLATIONS ARE NOT VALID RESULTING IN UNACCEPTABLE VALVEDEGRADATION, AND (3) IDENTIFYING SPECIFIC IMPROVEMENTS IN GATE VALVE DESIGNS WHICH OVERCOME PRESENT DESIGN LIMITATIONS. METHODOLOGY DEVELOPED IN ACCOMPLISHING THESE THREE OBJECTIVES WILL BE APPLIED TO VALVE DESIGNS FOR WHICH EXTENSIVE INSTRUMENTED TEST DATA ARE BEING MADE AVAILABLE BYDUKE POWER CO. TO KALSI ENGINEERING FOR THE PROPOSED RESEARCH. THESE DATA WILL BE USED IN VALIDATING THE PERFORMANCE PREDICTION MODELS. DUKE POWER FLOW TESTS WERE PERFORMED UNDER HIGH P FLOW GENERATED BY A PUMP INSTEAD OF ABLOWDOWN ACCUMULATOR USED IN RECENT INEL TESTS, THUS PROVIDING VALUABLE NEW INFORMATION TO THE INDUSTRY. GATE VALVE IMPROVEMENTS DEVELOPED ON PAPER UNDER PHASE I WILL BE TESTED UNDER PHASE II. THE SUCCESSFUL COMPLETION OF PHASE I AND II RESEARCH WILL RESULT IN IMPROVEMENTS IN MOTOR OPERATED GATE VALVE DESIGNS AND THE DEVELOPMENT OF RELIABLE MODELS FOR PREDICTING THEIR PERFORMANCE. THIS SHOULD GREATLY CONTRIBUTE TOWARDS THE REDUCTION IN THE FAILURE RATES OF MOVS WHILE REDUCING THE IN-SITU TESTING REQUIREMENTS WHEN USED IN CONJUCNTION WITH THE STATE-OF-THE ART MONITORING TECHNIQUES. GATE VALVE IMPROVEMENTS MAY HAVE THE POTENTIAL FOR BEING RETROFITTED INTO EXISTING DESIGNS, AND WILL RESULT IN IMPROVED ] COMMERCIAL VALVE DESIGNS IN THE FUTURE.