ML18009A874
| ML18009A874 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 04/23/1991 |
| From: | Vaughn G CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NLS-91-113, NUDOCS 9104240422 | |
| Download: ML18009A874 (6) | |
Text
ACCELERATED DISTRIBUTION DEMONS TION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:9104240422 DOC.DATE: 91/04/23 NOTARIZED: YES FACIL:50-400 Shearon Harris Nuclear Power Plant, Unit 1, Carolina AUTH.NAME AUTHOR AFFXLIATION VAUGHN,G.E.
Carolina Power 6 Light Co.
RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
DOCKET g
05000400
SUBJECT:
Requests review 6 approval of rev to commitment re Residual I
Heat Removal Sys Autoclosure Interlock deletion.Per 901116 ltr.
D DISTRIBUTION CODE:
A061D COPIES RECEIVED:LTR
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8 TITLE: OR/Licensing Submittal:
Loss of Residua Heat Removal (RHR) GL-87-12 NOTES:Application for permit renewal filed.
05000400 A
RECIPIENT ID CODE/NAME PD2-1 LA BECKER,D XNTERNAL: ACRS NRR TRAMMELL,C NRR/DST 8E2 OGC/HDS 1 RES/DSIR/EXB EXTERNAL: NRC PDR COPXES LTTR ENCL 1
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NOTE TO ALL"RIDS" RECIPIENTS:
A D
D PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAMEFROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!
TOTAL NUMBER OF COPIES REQUIRED:
LTTR 20 ENCL 17 V
G. E. VAUGHN Vice President Nuclear Senrices Department Carolina Power & Light Company P.O. Box 1551 ~ Raieigh, N.C. 27602 Itm'R 2 3Ig SERIAL:
NLS-91-113 10 CFR 50.90 United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 RESIDUAL HEAT REMOVAL AUTO CLOSURE INTERLOCK DELETION Gentlemen:
Carolina Power
& Light Company (CP&L) hereby requests NRC review and approval of a revision to a commitment made in conjunction with the Shearon Harris Nuclear Power Plant (SHNPP) Residual Heat Removal System Autoclosure Interlock (RHR-ACI) deletion.
Approval of this request is necessary to complete installation of the RHR-ACI deletion modification during the current refueling outage.
By letter dated November 16,
- 1990, CP&L requested the deletion of the technical specification requirements for the Residual Heat Removal System AutoClosure Interlock feature.
The request was approved by NRC on March 4, 1991.
The basis for deleting the interlock was a generic analysis sponsored by the Westinghouse Owner's Group (WOG) and documented in WCAP-11736-A.
The generic analysis was supplemented by SHNPP specific applicability reviews by CP&L.
As a part of NRC's approval of the generic WCAP, the staff identified five specific "plant improvements" that licensees should include in their requested technical specification changes.
NRC staff position Item (5) requested that licensees verify that the RHR suction valve operators should be sized so that the valves cannot be opened against full system pressure.
Carolina Power
& Light Company responded that the SHNPP RHR isolation
'valve operators have the capability of opening the valves against high differential pressures.
- However, CP&L committed to provide an equivalent to the requested undersizing of the motor operator.
The valve actuators would be adjusted to meet the intent of the NRC position.
Specifically, the opening torque switch setting would be reset to allow valve opening under design basis conditions, yet be low enough so that the actuator 9g04240422 91000400 I
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'ocument Control Desk NLS-91-113 / Page 2
would not allow the valve to open when high differential pressure
- exists, such as would occur at full RCS pressure.
During the implementation of this modification in the ongoing refueling
- outage, the results of the Motor Operated Valve (MOV) diagnostic testing program for these valves have indicated that the valve's unseating thrust loads are dominated by forces attributed to "wedging loads",
stem and friction loads and other valve factors, and are not influenced significantly by the fluid differential pressure across the valve.
We have noted a similar tendency in other Westinghouse Flex Wedge gate valves tested per our MOV testing program (Generic Letter 89-10, "Safety Related Motor Operated Valve Testing and Surveillance" ).
Due to the numerous component tolerances involved, it is not possible to achieve an ideal setting as was previously envisaged.
As a result, it is not possible to adjust the open torque limit switch such that the valve cannot be opened against full RCS pressure while still allowing operation at its design basis conditions.
The existing RHR suction isolation valves at SHNPP have the capability of opening against high differential pressure.
- However, downsizing of the actuators is not warranted since the valve thrust loads attributable to fluid differential pressure are not significant enough when compared to other valve considerations in the overall sizing of the actuator.
Therefore, a valve operator sized to ensure operation with design conditions while preventing opening under full system pressure is not feasible.
In addition, maintaining the size of the actuator in conjunction with the capability to manually bypass the torque switch at any time during the valve travel, provides assurance that the valves will perform their critical function when called upon.
This philosophy is consistent with CP6L commitments to Regulatory Guide 1.106 "Thermal Overload Protection for Electric Motors or Motor Operated Valves" as documented in the SHNPP Final Safety Analysis Report.
Therefore, CPSL proposes to restore the valve open torque switch and bypass circuitry to its original configuration as it relates to the RHR ACI deletion.
It should be noted that valve actuator sizing was not credited within the PRA discussed in the WOG report.
Rather it was mentioned as a note of conservatism (Sections 3.1, 7.3, 7.5.1, and 9.0).
Neither the results nor the conclusions of the report are affected by actuator sizing and its capability to open under high differential pressures.
Therefore, the basis and conclusions reached in WCAP-11736-A remain applicable to the Shearon Harris Nuclear Power Plant as presented in the technical specification change request.
Likewise, this proposed change does not affect the significant hazards consideration or the environmental consideration included in the technical specification change.
Independent of actuator sizing, SHNPP does have multiple means to ensure that the RHR suction isolation valves are not opened inadvertently while the RCS is at normal operating pressures.
These include redundant and
Document Control Desk NLS-,91-113 / Page 3
diverse open permissive (pressure)interlocks, an additional interlock while at power between the RHR isolation valves and the Refueling Water Storage Tank (RWST) discharge line valve, removal of motor operator power, and strict procedural controls regarding valve alignment and operation.
The'hearon Harris Nuclear Power Plant is currently in Refueling Outage No. Three with the reactor fuel stored in the Fuel Handling Building pools.
Refueling of the reactor vessel is anticipated to be completed as early as April 27, 1991.
Entry into Mode 4, Hot Shutdown, is anticipated as early as May 6, 1991 at which time one Emergency Core Cooling System train is required operable.
Therefore, to avoid any adverse impact on refueling or the restart schedule, CP&L requests an expeditious review and approval of this request to support Mode 4 entry.
In summary, it is CP&L's position that downsizing or modifying the RHR suction isolation valve actuator is neither warranted or feasible.
This does not change the results or conclusions of the analyses that were performed in support of the RHR-ACI deletion.
Multiple features are retained to prevent inadvertent opening of the RHR suction isolation valves which include: redundant and diverse open permissive (pressure) interlocks, RWST-RHR suction valve position interlocks, removal of power to the suction isolation valves and strict operator procedures regarding valve alignment and operation.
Please refer any questions regarding this submittal to Mr. Steven Chaplin at (919) 546-6623.
Yours very truly,
~~K G.
E. Vaughn GEV/SDC CC:
Mr. R. A. Becker Mr. J.
E. Tedrow Mr. Dayne H. Brown Mr. S.
D. Ebneter G.
E. Vaughn, having been first duly sworn, did depose and say that the information contained herein is true and correct to the best of his information, knowledge and belief; and the sources of his information are officers, employees, contractors, and agents of Carolina Power
& Light Company.
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