ML20002E134
| ML20002E134 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 01/16/1981 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-SSINS-9145 NUDOCS 8101260491 | |
| Download: ML20002E134 (6) | |
Text
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t SOUTH CAROLINA ELECTRK: a GAS COMPANY i
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CotuMe A south CAnouMA 29218 T. c. mewets. an.
January 16, 1981
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Wct pets.ocer ano Geove Esseut'wr NvCuae Ortestions Mr. James P. O'Reilly, Director 1
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U. S. Nuclear Regulatory Commission Region II, Suite 3100 101 Marietta Street, N.W.
l Atlanta, Georgia 30303 Subj ect: Virgil C. Summer Nuclear Station Docket No. 50/395 RE: Westinghouse Separation (NRC Inspectors Open Item #395/80-2-2),
Separation Requirements for Redundant Class lE Circuits Internal to Process Control Cabinets.
Dear Mr. O'Reilly:
The presence of a Train "A" (red) cable in the Channel IV (yellow) Protection Control Cabinet was questioned by an NRC Inspector. The circuit in question was "CRR 1A" which runs between the Reactor Trip Switchgear (Train "A") and the Protec-tion Set Cabinets XPN 7004 (Channel IV) for the Turbine inpulse interlock.
The circuit is a red colored circuit and is run separated up to the yellov XPN 7004 Cabinet. Within the cabinet no separation is maintained between CRR 1A and Channel IV circuits.
The termination points for this circuit are adjacent to channel IV inputs.
l GAI and Westinghouse have evaluated this condition. Westinghouse's evalua-tion is contained in letter #CGWS-1030, dated 5/27/80 (attached).
The letter shows that there is no credible fault of failure which could threaten to degrade the minimum degree of channel or train redundancy.
Concerns over the lack of redundant power supplies to these loops were addressed in an earlier letter to GAI (letter #CGWG 1943, dated 5/21/79).
Because of the above evaluatione it can be concluded that the lack of separation for CRR 1A does not constitute a substantial safety hazarl and there-fore is not a reportable significant deficiency.
Very truly yours, f
f T. C. Nichols, Jr.
3r ib JAW:TCN:glb Attachment cc:.Page Two 4) i 8101260
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Mr. James P. O'Reilly January 16, 1981 Page Two ec:. B. A. Bursey V. C. Summer G. H. Fischer W. A. Williams, Jr.
T. C. Nichols, Jr.
E. H. Crews, Jr.
D. A. Nauman O. S. Bradham O. W. Dixon, Jr.
J. B. Knotts, Jr.
- j R. B. Clary
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A. R. Koon A. A. Smith J. L. Skolds I&E (Washington)
Document Management Branch (55e/21/LER Only)
NPCF/Whitaker File B. Kane J
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CGWS-1030
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Westinghouse Water Reactor N 2 3C S
Electric Corporation Divisions Bcx355 Pitts0urpPennsylvania15230 May 27, 1980 Mr. C. A. Price, Manager S.0. CGE-1000 Nuclear Engineering South Carolina Electric- & Gas Company Ref:(a)CGWG-1943,5/21/79 P. O. Box ;764 (b)CGWS-985,3/06/80 i
Columbia SC 29218
Dear Mr. Price:
SOUTH CAROLINA ELECTRIC & GAS COMPANY VIRGIL C. SUMMER NUCLEAR STATION Wiring Separation Issue Clarification The reference (b) letter forwarded the Westinghouse position on a question raised by the NRC inspector concerning the wiring of the Turbine Impulse Interlock from the switchgear to Protection Set IV. Subsequently, the inspector reviewed our response and expressed some concern regarding its adequacy.
Based on discussions with Westinghouse site personnel, it is our understanding that the inspector's concern was not related to the routing of wiring between the reactor trip switchgear (train oriented) and process cabinets (protection set oriented) where both are powered from the same bus which in this case is "B."
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- Rather, the concern is associated with the case where the reactor trip syftch #
gear is being powered from the "A" bus and connected to process cabinet IIIGhich is powered from the "B" bus. This raises a question as to the possibili fy of a fault in the "A" bus switchgear propagating into a "B" bus process cabinet and defeating the "B" source.
To respond to this concern, it is first necessary to understand the design of the process equipment. The relay card perfonning the interlock function has the incoming power (24/26 VDC) source fused on the card. The card frame which contains the card and distributes the 24/26 VDC is also fused. The cabinet power supply which provides the 24/26 VDC to the cards has a DC breaker at the output. Also, the AC source to the cabinet power supplies has a breaker locaced in the cabinet. The combination of these current limiting devices limit the propagation of the fault.
In addition, an uncleared DC short in the process cabinet will not bring down the AC source of supply because the ferroresonant transformer in the cabinet power supply provides a fold over which limits the DC current to approximately 45 amps (unfiltered) for as long as the short circuit is applied. This is reflected as an approximate 30%
increase on the primary (AC) side which is an insignificant load increase on the 117 VAC bus.
s.o.s.a o. e O
RECEIVED '
JUN 111980 l
FILE NO.
NR ENG W g
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, C. A. Price 2
CGWS-1030 For the reasons noted above, 'a fault (short or induced voltagd) initiated in the reactor trip switchgear would not negate the bus for the interfacing process cabittet. Further there is little likelihood that the process cabinet in total would be affected. Finally, since redundancy is factored into the overall systems design, the loss of the cabinet would not create a loss in safety.
Should you have any questions or comments, please advise.
Very truly yours, WESTINGHOUSE E,CJ!QC CORPORATION
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y R. A. Stoug, Project Engineer SCE&G Project RAS:gcc cc:
C. A. Price il
- 0. W. Dixon ll H. T. Babb ll E. Wielkopolski 4L T. C. Nichols, Jr. IL E. H. Crews il R. C. Holzwarth ll D. A. Nauman ll H. Radin ll
- 0. S. Bradham il.
Plant Numerical Records System ll Nuclear Project Central File IL W. A. Williams, Jr. lL f
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Wes11nghouse Water Reactor PM SystesDvm Efectric Corporation Divisions sa333 PittshgnPemsytvania15230 May 21, 1979 CGWG-1943 Mr. E. Wielkopolski i
Gilbert Associates, Inc.
S.0. CGEM-320 P. O. Box 1498 525 Lancaster Avenue 3
Reading, Pennsylvania 19603
Dear Mr. Wielkopolski:
SOUTH CAROLINA ELECTRIC & GAS COMPANY VIRGIL C. SUMMER NUCLEAR STATION 7300 Series Process Cabinets I)uring a meeting at the Virgil C. Summer site on April 4,1979, GAI per-sonnel requested that Westinghouse provide the status of action items D and E3 in the meeting minutes attached to CGGS-18072 dated March 28, 1979. These action items are both related to the, subject system.
The second part of item E3 noted that Gilbert had not received any formal response to the comments they had on the turbine impulse chamber pressure loops. Accordingly, Westinghouse was requested to respond to these com.lents, which concern the channel assignments (3 and 4) for the two loops and the fact that inverters 3 and 4 are both fed from the Train B OC battery.
However, the Westinghouse NSSS process control block diagram 1080932, sheet 4, shows the channel 3 loop (PY/446) receiving a signal from the Train A reactor trip switchgear.
We have reviewed the above cortments and based on this review, we consider there should not be a separation problem with the present design. This consideration is based on the fact that the interfacing signals between the process cabinets and the reactor trip switchgear are electrically isolated in the reactor trip switchgear.
Further, we assume Gilbert has maintained channelized cable separation for the external cables between the process cabinets and the reactor trip switchgear.
From a safety standpoint, it is acceptable to have both channels P-446 and P-447 fed from the Train 8 power source. The permissive, P-13, derived from these channels negates certain protective functions at low -
turbine impulse chamber pressure.
Each channel feeds a redundant "0R" gate. Loss of Train B power source to the process cabinets removes the permissive.
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E. Wielkopolski CGWG-1943 Item D and the first part of item E3 identified certain hardware and soft-ware changes which Gilbert considers should be made. Accordingly, Westing-house was asked whether these changes could be included with the package of changes listed in the attachment to CGWS-822. We have reviewed this
. situation and detemined that these changes cannot be included with the changes listed in the attachment to CGWS-822. Therefore, should you desire these changes to be made at a later date, please advise and we will be pleased to provide a proposal.
I It should be noted, however, that these changes as well as those identified in CGGW-1329 and CGGW-1334 will have to be reviewed in some detail before they can be incorporated. The reason for this is that the cabinets have to be checked for available space and we must be certain that the DC power supplies are still adequate because they are rapidly approaching their maximum supply capacity.
Should you have any questions or comments, please advise us.
Very truly yours, WE'STIllGHOUSE E.E RIC CORPORATICN R. A. Stough, Project Engineer SCE&G Project
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E. Wielkopolski, 4L
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H. T. Babb, IL I
- 0. W. Dixon, IL E. H. Crews, IL T. C. Nichols, Jr.,1L D. A. Nauman, IL H. Radin, IL IL
$ NUEL'eWJf^eE{l Records System, ILR. C. Holzwart C
Plant flumerica W. A. Williams, Jr., IL t
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