ML17252A768
| ML17252A768 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/13/1975 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | James Keppler NRC/RGN-III |
| References | |
| BBS Ltr. #368-75 50-249/1975-30 | |
| Download: ML17252A768 (3) | |
Text
Commonwe.-' Edison
- One First Natio.
laza, Chicago,.llhno1s Address Reply to: Post Office Box 767 c.hicago, Illinois 60690 BBS Ltr. #368-75 Mr. James G. Keppler, Regional Director Directorate of Regulatory Operation~Region III
- u. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
SUBJECT:
REPORT OF ABNORM.l\\L OCCURRENCE PER SECTION 6.6.A OF THE TECHNICAL SPECIFICATIONS SBLC RELIEF VALVE SETPOmTS LESS THAN TECH SPEC LIMITS
SUBJECT:
- 1) Regulatory Guide 1.16 Rev. 1. Appendix A
- 2) Notification of Region III of u. s. Nuclear Regulatory Connnission Telephone:
P. Johnson, 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on June 5, 1975 Telegram: J. Keppler, 1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br /> on June 5, 1975
- 3) Drawing Number M-364
- 4)
Letter from H. K. Hoyt to Dr. Peter A. Morris; Report No. 50-237/1970-48 Report Number:
50-249/1975-30 Report Date:
June 13, 1975,
Occurrence Date:
June 5, 1975 Facility: Dresden Nuclear Power.Station, Morris, Illinois IDENTIFICATION OF OCCURRENCE The Standby Liquid Control (SBLC) pump discharge relief valves were found at setpoints lower than the Technical Specification limits.
CONDITIONS PRIOR TO OCCURRENCE Unit-~ was in the shutdown moEie for a refueling outage.
DF.sCRIPTION OF OCCURRENCE On May 24, 1975 a test was performed, in the maintenance shop, on relief valve 1105-A to determine the relief valve setting. The valve was found to be set at 1250 psi.
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.. _.;_,... /..
Mr. James G. Keppl~r June 13, 1975 The same test Wa.s performed on relief valve 1105B on May 28, 1975. At 1320 psi the valve began to leak.
These events were reported at 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on June 5, 1975. Failure to report the incident immediately was a result of a procedural inadequacy which specified that no action be taken.
DESCRIPI'ION OF APPARENT CAUSE OF OCCURRENCE (Equipment Failure) i I
Relief valve 1105A performed properly in the test except that the setpoint was low. This 'incident is attributed to setpoint drift.
Relief valve 1105 B began to leak at 1320 psi, below the required setting
- Disassembly of the valve revealed crystals of sodium pentaborate on the valve seat. These crystals prevented the valve from seating properly and lowered its relief setpoint *
.ANALYSIS OF OCCURRENCE Both SBLC pumps are 100% capacity pumps.
When required, the reactor operator will select one of the systems.
Therefore, the operability of t.he system is limited to 1250 psi. The system is intended as a backup system for the control rod drive system, with the reactor in the cold condition, in the everit that all rods fail to insert a~er a reactor trip.
The SBLC system will not be required to operate_with reactor pressure greater than 1250 psi as there are no expected reactor transients which result in a reactor pressure greater than 1250 psi in the period of time which can affect the operation of the SBLC system. Therefore, the health and safety of the public were not compromised by this occurrence.
CORRECTIVE ACTION Valve 1150-B, which started leaking at 1320 psi was cleaned and lapped to remove* the crystals around the valve seat. It was 'then reset to 1448 psi and reinstalled on May 30, 1975.
Valve 1105-A was cleaned and reset. This event is considered to be an isolated case and does not appear to be an inherent problem in the design of the valve.
No further action was deemed nec.cessary.
The procedure for testing the SBLC injection lines was revised prior to the most recent_ valve test. The valves are now tested with nitrogen in the maint-enance shop. This will minimize the possibility of sodium pentaborate crystals forming on the valve seat. In addition, the relief valve testing procedure will be revised by July
, 1975 to ensure that any deviation from Tech Specs limits is reported to the shift engineer within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the occurrence.
Mr. James e June 13, 1975 FAILURE DATA
- A review of station records indicates that sodium pentaborate deposits on the valve seat has occurred once before (reported August 25, 1970).
Setpoint drift as found on valve 1105-A has never occurred before.
Sincerely,
~~-*
BBS:DB:smp File/NRC f