ML20084R273
| ML20084R273 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 07/11/1973 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084R275 | List: |
| References | |
| RO-730711, NUDOCS 8306150052 | |
| Download: ML20084R273 (3) | |
Text
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Commohith Edison f'w Quad-Cities Nuclear Power Station V
E Post Offics Box 216 i
Cordova, Illinois 61242 Telephone 309/654-2241 g
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k July 11, 1973 JUL16?$73 - 9 1
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Mr. John F. O' Leary, Director Directorate of Licensing L
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U. S. Atomic Energy Commission N,'ig'W' Washington, D. C.
20545
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Dear Mr. O' Leary:
SUBJECT:
Quad-Cities Nuclear Power Station Units 1 and 2, Docket #50-254 and 50-265 DPR-29 and 30, Appendix A,
Sections 1.0.A.4 and 6. 6.B.1 The purpose of this letter is to inform you of the details con-cerning an abnormal occurrance which took place on July 5,
- 1973, whereby the Unit 2 standby liquid control system "A" was inoper-able due to premature lif ting of the pump relief valve.
This occurrance was reported to you by telegram on July 5, 1973.
PROBLEM AND INVESTIGATION At approximately 11:00 a.m. on July 5, 1973, Unit 1 was at a steady power level of 800 MNe and Unit 2 was operating at 788 MWe.
At that time, the monthly flow rate test on the standby liquid control system for Unit 1 and Unit 2 was being conducted.
When running the 2A standby liquid control pump it was observed that wi.th a pump discharge pressure ct U 400 PSIG, water flow was heard flowing through the 2A standby liquid control pump relief valve.
The 2A standby liquid control pump was stopped to prevent diluting the storage tank.
The 2B standby liquid control system was immedi-ately checked and was found to be completely operable (technical specification 3.4).
The 2A standby liquid control pump relief valve was immediately reset by the maintenance department.
Set pressure after the re-lief was reset was 1470 PSIG.
At 11:30 a.m. the 2A standby liquid control pump was declared operable.
The 2A pump had been started and flow checked.
No deficiencies or abnormalities were observed during flow rate test.
EVALUATIONS AND CORRECTIVE ACTIONS A.
SAFSTY IMPLICATIONS The 2A standby liquid control pump was inoperable for sv 30 minutes.
During this time a flowratetestwasrunop(p the 2B standby liquid control pump.
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The results of the flow rate test on the 2B standby liquid control pump met the operability requirements in the tech-nical specifications.
The 2B pump relief valve was checked and its setpoint was determined to be 1420 PSIG which is in limits specified in the - technical specifications.
The overall safe operation of the plant was thus not effected during the time which the 2A standby liquid control pump was inope rable.
B.
DETERMINATION OF CAUSE The probable cause for the 2A standby liquid control pump re-lief valve initially opening was due to the setting of the pump flow rate test pressure.
The operator apparently raised the pressure too high and inadvertently opened the relief valve.
It is postulated that the 2A standby liquid con *.rol pump relief did not fully reset because of possible build-up of sodium pen-taborate on the valve disc, which is spherical in shape.
When the valve rescated the disc rotated slightly and held the valve slightly open.
With the relief slightly open, water was heard flowing through the relief.
As water flowed through the slightly open relief, the sodium pentaborate disolved, and the relief completely reseated.
C.
CORRECTIVE ACTIONS A procedure change has been issued to caution the operator when setting the flow rate test pressure.
The 2A standby liquid control pump relief will be checked each week for one month to check set pressure and insure it reccats.
On July 10, 1973, the 2A standby liquid control relief was checked and it operated at 1470 PSIG and reseated properly.
During the time period that the 2A standby liquid control pump relief is tested, it will be observed for further possible operating problems.
On June 5, 1973, the Unit 1 standby liquid control pumps.re-lief valves were also check for setpoints.
The setpoints as found were:
1A relief valve set at 1440 PSIG and 1B rel'ief valve set at 1420 PSIG.
These were rechecked because of a setpoint drift found during the June flow rate test of the Unit 1 standby liquid control system.
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l We will inspect the 2A standby liquid control system pump re-lief valve at the next scheduled outage to examine the valve j
seating surface.
D.
EVALUATION OF CUMUIATIVE EXPERIENCE FOR SAFETY IMPLICATIONS The Unit 1 standby liquid control pump relief valves were found to be set slightly low.
They were reset and rechecked one month later.
The setpoints were within technical specifica-tions and no drift was observed.
The 2A standby liquid control system pump relief valve will be checked weekly as stated above.
The first check showed that the relief valve operated correctly.
Good results for the in-terval during which weekly checks are made, should ensure proper operation of the valve for the operating cycle, thus rendering no decreased margin to the safe operation of the unit.
Respectfullg3
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)1enson 4
Station S perintendent BBS:LMK/dkp BBS-73-143
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cc Regional Director Directorate of Regulatory Operations - Region III s
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