ML20084L334
| ML20084L334 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 04/03/1974 |
| From: | Kalivianakis N COMMONWEALTH EDISON CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084L335 | List: |
| References | |
| NJK-74-24, NUDOCS 8305200649 | |
| Download: ML20084L334 (3) | |
Text
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50-265 fC Quad-Clu./ Generating Station L'Dl Post Off4ce Box 216 A
Cordova. !!!inois 61242 J
Telephone 309/654-2241 10s!.d sK NJK-74-24 T pp g g3ps tj j
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April 3, 1974 g
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Mr. John F.
O' Leary, Director Directorate of Licensing-Regulation U. S. Atomic Energy Commission Washington, D.
C.
20545
Reference:
Quad-Cities Nuclear Power Station, Unit 2 Docket No. 50-265, DPR-30, Appendix A, Sections 1.0.A.2, 1.0.A.4, 3.5.A.3, 6.6.B.1 Dear Mr.
O' Leary:
The purpose of this letter is to inform you of the details of an abnormal occurrence which was discovered on March 25, 1974.
Unit 2 low pressure coolant injection isolation valve, MO 2-1001-29B, would not fully open while attempting to initiate shutdoun cooling.
This occurrence was reported to you by tele-gram on March 26, 1974 and to the Directorate of Regulatory Operations by telephone and telegram also on March 26.
PROBLEM AND INVESTIGATION On March 25, 1974 at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> with unit two shutdown, an l
attempt was made to open LPCI isolation valve MO-2-1001-29B l
to initiate the shutdown cooling mode of the RHR system.
l Double indication was noted for the valve in the control room at panel 902-3, indicating the valve had not fully opened.
l The valve is a motor operated 16 inch gate valve manufactured by the Crane Valve Company with a Limitoroue SMB-4 operator.
Upon investigation it was found that the valve was actually about 60% open.
Attempts to manually open the valve to 100%
failed.
The valve was taken out of service and disassembled for inspection.
The inspection showed the valve stem to be bowed along the threaded portion.that enters the motor opera-tor.
Representatives of the valve vendor were consulted to determine a course of corrective action.
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Mr. J. F. O' Leary April 3, 1974
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- EVALUATIONS AND CORRECTIVE ACTIONS An attempt was made to. straighten the bowed portion of the stem with. a hydraulic press in.tlua station shop.
This proved to be unsuccessful.
A new stem was ordered from the Crane company and checks were made of other nuclear stations likely to have a spare stem of the proper type but none was found.
A new stem of an alloy superior to that of the original stem was manufactured by the Crane Company and delivered to the station on March 29, 1974.
The new stem was; installed and tested according to Quad-cities station Modification Number M-4-2-74-36.
Valve repairs and testing were completed on March 31, 1974.
Unit 2 was returned to power operation later l
that same day.
The exact cause of the bent stem cannot be determined.
Both the torque switches and the limit switches were checked and found to be operating properly.
The last monthly operability check had been performed on March 7, 1974; also the valve had been cycled at 1025 hours0.0119 days <br />0.285 hours <br />0.00169 weeks <br />3.900125e-4 months <br /> on the day of the failure with no reported abnormalities.
SAFETY IMPLICATIONS At the-time of the failure the unit was in the cold shutdown condition.
Since the valve was able to be opened to 60% it was capable of passing approximately 75% of.its rated flow.
Also the valve was last known to be operable eight hours pre-viously.
Since there was no work going on,that had the po-tential to drain water from the reactor vessel, the safety implications of this occurrence were minimal.
The chutdown cooling system was still able to be used by pumping to the "A" recire loop.
CUMULATIVE EXPERIENCE There has been one failure of a valve stem similar to this one.
In October, 1972 a High Pressure Coolant Injection (HPCI) system steam inlet valve was found to have a bent stem.
That failure was found to have been caused by the operator repeat-edly placing the control switch to the closed position while the valve was closed.
This had been done while checking for DC grounds at that time.
The operators have been cautioned not to do this since the time of that failure.
It is not known if the RHR valve had been previously bent, but still operated 4
O O
Mr. J. F. O' Leary April 3, 1974 satisfactorily or if the failure occurred on the day it was discovered.
It is felt that the present valve operability checks are adequate to detect any further failures of this type.
Very truly yours, COMMONWEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION
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Nh N. J.
Kalivianakis Station Superintendent NJK/lk cc:
Region III, Directorate of Regulatory Operations J. G. Abcl i
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