ML19344D357
| ML19344D357 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 02/19/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19344D355 | List: |
| References | |
| NUDOCS 8003120144 | |
| Download: ML19344D357 (2) | |
Text
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F3 JAM 13 nr' SAFETY EVALUATION REPORT CHARGING PUMP INDUCED VIBRATIONS AT ZION STATION DIVISION OF OPERATING REACTORS Introduction Vibrations induced by the operation of positive displacement pumps have been identified as one source of fatigue failure in Charging and Volume Control System (CVCS) piping. On August 31, 1978 NRC requested information on reported pipe cracks in the CVCS due to excessive charging pump induced vibrations.
Comr onwealth Edison Company provided the requested inforrntion in letters dated October 4,1978 and January 23, 1980 for the Zion Unit.ios,1 and 2.
Descriotion and Evaluation Zion Unit Nos.1 and 2 have the identical arrangement of charging pumps.
Each plant has two centrifugal charging pumps and one positi.ve displacement pump.
Eacr. cf the two centrifugal pumps is capable of handling the maximum rated let-down or purification flow by itself. Therefore, only one centrifugal pump is used to provide the full charging flow and the reactor coolant pump seal water supply during normal plant operations as well as the maximum letdown or purifica-tion ficw. A second pump is used as a standby. The positive displacement pump is a backup pump and is only capable of providing the charging flow and the reactor coolant pump seal water supply during nomal plant operations.
It is nor ally used only to hydrotest the reactor coolant system. The safety injection fun:tions of the Emergency Core Cooling System are accomplished by the Centri-fugal pumps.
Ear'y plant operations indicated the existence of excessive vibrations in the positive displacement pump discharge lines. A field study made by Southwest Research Institute at Zion Station showed that the peak to peak pressure pulsations ranged from a maximum of 920 psi, at 49 Hz to a minimum of 200 psi at 54 Hz for Uni: 'o. 2.
The suction line pulsations were not severe. The peak to peak value ran;e: from 16 psi at 3 Hz to 1 psi at 40 Hz for Unit No. I and 8 psi at 1 Hz to i psi at 3 Hz. Two pulsation dampeners, one for each plant, were installed in the discharge lines as a result of the study. The dampeners were of the Greer Hycraulic, Inc.
Pulse-Tone 21/2-gallon bladder type design, with a maximum wor?.ing pressure of 2800 psi to provide a 2% attenuation (or about 100 psi peak to peak). The dampeners were installed in 1978 on both Units.
A se:cnd field study by Southwest Research Institute was made in October 1979 to.erify the performance of the dampeners. The maximum discharge pulsation 'n U r.i :
- s.1 was found to be 40 psi instead of the 920 psi in the previous study.
Tni: is about 1.3% of the normal operating pressure of 2250 psi.
Suction
- i. 21: ions were also reduced due to s. aller discharge pulsations.
0003120 199-I
2 rE!!s1:7.! 13 us Conclusion The installed dampeners at Zion Unit Nos.1 and 2 reduce the excessive pressure fluctuation in the CVCS lines. Our review of field study data verifies that the modifications are effective. The system performance is acceptable and will not likely cause fatigue failures in the positive displacement pump lines.
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