ML20207Q822
| ML20207Q822 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 03/04/1987 |
| From: | Andrews R OMAHA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-PT21-87 LIC-87-058, LIC-87-58, NUDOCS 8703100035 | |
| Download: ML20207Q822 (2) | |
Text
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Omaha Public Power District 1623 Harney Omaha. Nebraska 68102 2247 402/536-4000 March 4, 1987 LIC-87-058 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555
Reference:
1.
Docket No. 50-285 2.
Letter OPPD (R. L. Andrews) to NRC (R. D. Martin), dated March 17, 1986 (LIC-86-165)
Gentlemen:
SUBJECT:
Revised Schedule For Replacing Valves This letter is to inform the NRC of OPPD's revised schedule for replacing the Valcor valves discussed in Reference 2.
By Reference 2, OPPD provided a 10 CFR Part 21 report, detailing the discovery of a material defect in the disc spring assemblies of two Valcor valves, OPPD tag numbers HCV-247 and HCV-248, installed at Fort Calhoun Station.
Failure was caused by hydrogen embrittlement of the 17-7 PH stainless steel springs.
Two other valves, HCV-249 and HCV-2988, were also identified as having the same spring material.
OPPD stated in Reference 2 that these four valves were to be replaced during the 1987 refueling outage.
While inspection and analysis of the disc spring assemblies of valves HCV-247 and HCV-248 revealed that the springs had experienced a catastrophic failure caused by hydrogen embrittlement, the identical spring assemblies in valves HCV-249 and HCV-2988 were found to be in good condition. Although the valves are exposed to the same fluid, valves HCV-247 and HCV-248 are normally open whereas valves HCV-249 and HCV-2988 are normally closed.
Exposure to the continuous flow through the open valves results in much higher temperatures that accelerates the corrosion process as compared to the normally closed valves where flow does not usually exist.
Solenoid valves HCV-247, HCV-248, HCV-249 and HCV-2988 were installed in Decem-ber,1982 as redundant valves, per the requirements of 10 CFR Part 50, Appendix A, Section IV, Criterion 35, for the long term core cooling system.
Problems with the disc spring assemblies in FCV-247 and HCV-248 were first experienced in August, 1985 during equipment rotation.
Spring material which would not be subject to hydrogen embrittlement could not be obtained in time for replacement during the 1985 refueling outage.
Because of the exhibited time for the 8703100035 870304 yD ADOCK 05000285 gan: rO9MhM fj00/
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U. S. Nuclear Regulatory Commission LIC-87-058 Page 2 original spring to fail, springs made of the same material were installed as a temporary repair. Valves HCV-247 and HCV-248 were scheduled fer replacement during the 1987 refueling outage. Surveillance testing of the valves indicate that the replacement disc assemblies have again experienced hydrogen embrit-tlement; this time with a much shorter operational history.
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To ensure the long term reliability of the valves, it was decided that the en-tire valve assembly should be replaced rather than just replacing the springs.
The normal delivery time for these valves is approximately 50 weeks.
Since replacement of HCV-247 and HCV-248 was considered necessary during the 1987 refueling outage, an expedited delivery was requested and the valves will be available for the scheduled installation.
Inspection of internal parts of HCV-249 and HCV-2988 did not show signs of corrosion. The valves have no operational problems, and are predicted to be satisfactory for service during Cycle 11 operation. Additionally, the valves are tested quarterly to ensure that they cycle properly. Therefore, a normal delivery schedule was deemed acceptable. Delivery of replacement valves for HCV-249 and HCV-2988 is scheduled for October of 1987, almost one year before the start of the 1988 outage, but not in time for installation during the 1987 outage.
In summary, OPPD wishes to inform you that our schedule for replacement of valves HCV-247 and HCV-248 is during the 1987 refueling outage and valves HCV-249 and HCV-2988 is during the 1988 outage.
If you have questions or require additional information, please contact us.
Sincerely R. L. Andrews Division Manager Nuclear Production RLA/me l
xc:
LeBoeuf, Lamb, Leiby & MacRae 1333 New Hampshire Ave., N.W.
Washington, DC 20036 l
A. C. Thadani, NRC Project Director W. A. Paulson, NRC Project Manager P. H. Harrell, NRC Senior Resident Inspector 1
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