ML20137U846
| ML20137U846 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  |
| Issue date: | 02/03/1986 |
| From: | Corbin McNeil Public Service Enterprise Group |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| NUDOCS 8602190350 | |
| Download: ML20137U846 (3) | |
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Public Service Electric ae.d Gas -
Cornpany Corbin A. McNeill, Jr.
Public Service Electric and Gas Conany P.O. Box 236,Hancocks Bridge, NJ 08038 609 339-4800 Vics President -
- Nuclear February 3, 1986 Dr. Thomas E. Murley, Administrator U.
S. Nuclear Regulatory Commission l
Office of Inspection and Enforcement Region I 631 Park Avenue l
King of Prussia, Pennsylvania 19406 l
Dear Dr. Murley:
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SIGNIFICANT CONSTRUCTION DEFICIENCY INADEQUATE POWER TO TRANSMITTERS HOPE CREEK GENERATING STATION On January 15, 1986, a verbal report was made to Region I, Office of Inspection and Enforcement representativa, Mr. R.
Puhrmeister, advising of a construction deficiency concerning misoperation of Tobar pressure transmitters.
The following information is provided in accordance with 10C?R50.55(e).
j Description of the Deficiency l
During startup testing activities, it was found that previously calibrated Tobar pressure transmitters exhibited erratic output signals.
Further investigation determined that the power supply circuit impedance exceeded Tobar's specified maximum of 400 ohms at 24 VDC.
The higher impedance resulted in voltage drops to approximately 18 VDC, measured at the transmitter terminals.
Tobar transmitters, bench calibrated at 24 VDC, will not operate properly when the power supply voltage drops below 20 VDC.
Startup Deficiency Report (SDR) No. ZC-0068 was initiated to document and control the deficiency.
Bechtel, our Architect / Engineer, has determined that the problem is unique to class lE analog circuits utilizing Tobar transmitters, powered by Bailey Signal Resisting Units (SRU).
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Dr. T.
E. Murley 2
2-3-86 Safety Analysis The Tobar transmitters serve three basic functions, as follows:
A.
Provide process information to assist the operator during normal and emergency modes of operation.
L B.
Monitor system or component process conditions and initiate automatic interlocks for system / component protection (e.g.,
trip pump on low suction pressure).
C.
Provide process information to process control loops.
For each of these functions, we have identified at least one case where, without operator action, the misoperation of the Tobar transmitter could have affected the safe operation of the plant.
A description of one such case is provided below:
Station Service Water System (SSWS) - Pressure transmitters PT-2356A1, A2, and A3 (Loop A) and PT-2356B1, B2, and B3 l
(Loop B) monitor the discharge line from the Station Auxil-iaries Cooling System (SACS) heat exchangers to the cooling tower.
Down?tream of system isolation valves HV-2357A and B,
the 3ines are downgraded to non-Q.
Should these lines fail and cause blockage, the outlet pressure from the SACS heat exchangers will increase.
Under these conditions, the pressure transmitters, arranged in a 2 out of 3 logic, will automatically open yard dump valves HV-2356A and B (Note per DITS 3.9, sudden blockage will cause a rupture disc installed in parallel to the yard dump valve to rup-ture, thus obviating the need to open HV-2356A and B).
Should this interlock fail to operate and the blockage does not cause the rupture disc to rupture, SSWS flow through the SACS heat exchangers will cease.
This will lead to eventual overheating of SACS Loops A and B and the subse-quent loss of cooling to the SACS loads (of primary concern would be the Residual Heat Removal (RHR) heat exchangers).
Based upon the above analysis, we conclude that the subject defi-ciency is reportable in accordance with 10CFR50.55(e).
Corrective Action In accordance with the disposition of SDR ZC-0068, a Design Change Package (DCP-7153) has been issued'to modify the power supply circuits to the Tobar transmitters.
The modification
6; Dr. T..E.lMurley-3-
2-3 I i-bypasses'a-150 ohm current' limiting resistor in the Bailey-SRU with a fused circuit, thus reducing overall loop impedance and providing_ sufficient voltage'.to' ensure correct operation of the transmitters.
l f-Sincerely, f
C Office of Inspection and Enforcement
. Division of Reactor Construc' ion Inspection t
Washington, D.;C. 20555 NRC Resident Inspector - Hope Creek P.
O.
Box 241 Hancocks Bridge, NJ 08038 l
Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, GA 30339 l
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