IE Circular No. 79-22 - Stroke Times for Power Operated Relief Valves
CR79022 November 15, 1979 MEMORANDUM FOR: B. H. Grier, Director, Region I J. P. O'Reilly, Director, Region II J. G. Keppler, Director, Region III K. V. Seyfrit, Director, Region IV R. H. Engelken, Director, Region V FROM: Norman C. Moseley, Director, Division of Reactor Operations Inspections, Office of Inspection and Enforcement SUBJECT: IE CIRCULAR NO. 79-22 - STROKE TIMES FOR POWER OPERATED RELIEF VALVES The subject circular is transmitted for issuance on November 16, 1979. The Circular should be issued to all power reactor operating facilities and all utilities having a construction permit. The texts of the circular and draft letter to licensees and permit holders are enclosed for this purpose. Subsequent to issuance of the circular, the regions should followup per IE Procedure 92703B. Norman C. Moseley, Director Division of Reactor Operations Inspection Office of Inspection and Enforcement Enclosures: 1. Draft Transmittal Letter 2. IE Circular No. 79-22 CONTACT: R. W. Woodruff, IE 49-28180 . (Draft transmittal letter for IE Circular No. 79-22, to each holder of an. Operating License or a Construction Permit) IE Circular No. 79-22 Addressee: The enclosed IE Circular No. 79-22, is forwarded to you for information. No written response is required. Should you have any questions related to your understanding of this matter, please contact this office. Sincerely, Signature (Regional Director) Enclosures: 1. IE Circular No. 79-22 2. Recently Issued IE Circulars . SSINS: 6830 Accession No.: 7908220142 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C. 20555 November 16, 1979 IE Circular No. 79-22 STROKE TIMES FOR POWER OPERATED RELIEF VALVES Description of Circumstances: Most PWRs utilize power-operated relief valves (PORVs) to prevent overpressurization of the reactor coolant system when the reactor is at low temperature. On April 13, during a pressure transient at Robinson 2, the PORVs did not function as rapidly as intended. The estimated stroke time for the PORVs was three to five seconds whereas the intended stroke time is two seconds. As a result, the pressure transient did approach a pressure limit which is based on nil ductility considerations. Prior to April 13, the PORVs had not been used or exercised since February, 1978, when they had been repacked and stroked. Although the valve stems were scored at that time, stroke times were satisfactory. The licensee and the valve manufacturer believe that the scored stems and the 14-month interval without exercise resulted in poor performance of the PORVs. Recommended Actions for Licensees' Consideration: All holders of PWR operating licensee or construction permits should be aware of the potential problem of the type discussed above. Because of the generic implications in this matter, it is recommended that both licensees of operating facilities and holders of construction permits conduct a review to determine if periodic surveillance of PORVs is necessary to assure that the PORVs will perform as intended. No written response to this Circular is required. If you require additional information regarding these matters, contact the Director of the appropriate NRC Regional Office.
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