ML20086C117
| ML20086C117 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 03/16/1976 |
| From: | Schwalje E Public Service Enterprise Group |
| To: | Knuth D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20086C120 | List: |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8311220576 | |
| Download: ML20086C117 (2) | |
Text
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O PS$G Pubhe' Service E'ectric and Gas Company 80 Park Place Newark, N.J. 07101 Phone 201/622-7000 March 16, 1976 hg S
Dr. Donald F.
Knuth, Director Q
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Nuclear Regulatory Commission
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7920 Norfolk Avenue 4
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Dear Dr. Knuth:
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3/4" PIPE FAILURE - RHR SYSTEM NO. 1 UNIT
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SALEM NUCLEAR GENERATING STATION DOCKET NO. 50-272 On February 26, 1976 a verbal report was made to Region 1, Office of Inspection and Enforcement, advising that a failure of a 3/4" vent line in the RHR System occurred during the performance of a hot functional test.
This report was in accordance with provision of 100FR50.55(e).
The following is a detailed analysis and report on the 3/4" pipe failure in the RHR System:
While testing unde r Startup Procedure 50.10, " Solid System Pressure Control," during Hot Functional Testing, excessive vibration was observed in a 2" interconnecting line between the RHR and CVC systems.
This vibration caused the failure by cracking of a 3/4" pipe nipple to which vent valve llRH57 was connected.
The cause of the vibration was control valve 1CV8 (a 2" globe valve, air to open) in the above mentioned inter-connecting line, which controls the rate of flow from the RHR system to tbe CVCS letdown path.
Valve 1CV8 was in its closed position.
It was discovered, however, that 1CV8 was not fully seated because of miscalibration of the air signal to the valve operator.
At the time of this occurrence 75 gpm of letdown flow was passing through the CVC letdown path.
No. 11 and 12 RHR pumps were pumping Reactor Coolant through the Reactor Vessel.
RCS pressure was 350 psig and RCS temperature was between 100 and 150 F.
As valve 1CV8 was not fully seated, it allowed considerable flow to pass from the discharge of the RHR pumps and into the CVCS letdown piping through 1CV8.
As the flow increased, 1CV8 began to oscillate, transmitting considerable vibration to llRH57 through interconnecting piping.
Valve llRH57, a 3/4" vent valve, 8311220576 760316 gDRADOCK05000 ggg The Energy People COPY SENT REGI s aw _ - - -
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F. Knuth 2-3/16/76 was mounted on a 3/4" Schedule 40 pipe nipple connected to a tee in the 2" interconnecting piping.
The transmitted vibration caused a considerable moment at the valve, which resulted in the nipple cracking in the heat affected zone of one weld.
Corrective action consisted of replacing the 3/4" vent pipe nipple with a 2" pipe nipple and a 2" x 3/4" reducing insert.
The air signal to the 1CV8 operator was recalibrated to allow the valve to seat fully.
In addition, a radiograph of the 1CV8 valve body was taken and it was discovered that the valve was installed backwards.
Valve 1CV8 will be reinstalled in its correct position after Hot Functional Testing.
Valve llRH57 is located in a portion of the RHR system, which is normally isolated from the remainder of the system.
Had this failure occurred during plant operations, it would not have affected the safety functions of the RHR or CVCS systems.
This failure then would not have affected the safety of the operating staff or the general public.
If you desire additional information on this subject, we will be pleased to discuss it with you.
Very truly yours, b
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E. N.
Se alje Manager of Quality Assurance Engineering & Construction Depar tmen t CC Mr.
J.
P. O'Reilly King of Prussia, Pa.
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