United States Nuclear Regulatory Commission - Protecting People and the Environment

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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