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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