ML15117A282

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Summary of 950119 Meeting W/Util Re Questions Concerning Design & Technical Details of Proposed Modification to Provide Over Frequency Protection for Plant Emergency Power Paths
ML15117A282
Person / Time
Site: Oconee  
Issue date: 01/26/1995
From: Wiens L
Office of Nuclear Reactor Regulation
To:
Office of Nuclear Reactor Regulation
References
NUDOCS 9502030314
Download: ML15117A282 (24)
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Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 January 26, 1995 LICENSEE:

Duke Power Company FACILITY:

Oconee Nuclear Station, Units 1, 2, and 3

SUBJECT:

SUMMARY

OF JANUARY 19, 1995, MEETING WITH DUKE POWER COMPANY ON PROPOSED MODIFICATION TO THE OCONEE EMERGENCY ELECTRICAL SYSTEM On January 19, 1995, NRC staff members met with representatives of Duke Power Company (DPC) toldiscuss questions the staff had identified concerning the design and technical details of a proposed modification to provide over frequency protection for the Oconee emergency power paths. The specific staff questions are included as Enclosure 1. A list of meeting attendees is included as Enclosure 2. Copies of the licensee's handouts are included as.

The licensee's presentation opened with a brief description of the Oconee onsite electrical system. The design basis for the Keowee emergency power system was then presented as the ability to provide emergency power to the Oconee Nuclear Station within the committed time under all applicable conditions assuming a single failure. After some discussion, the licensee stated the position that the switchyard yellow bus is part of the onsite power system at all times. Thus, a component failure which could cause a loss of this bus would be considered the single failure of the onsite electrical system. In addition, the licensee stated that any single failure was assumed to occur simultaneously with the initiating event. The licensee then described two vulnerabilities which could prevent meeting this design basis and the administrative controls in place to address these vulnerabilities.

The modification being reviewed by the NRC staff is intended to correct these vulnerabilities.

Each of the remaining questions were addressed in order. The responses to these questions will be formally submitted by the licensee. The staff requested additional information related to the bench-marking of the computer model used to calculate the load rejection response of the Keowee units, verification of the adequacy of the administrative limits applied to the output power of the Keowee units, and the manufacturer's specifications for the transfer and retransfer relays. The staff also requested information on 9502030314 950126 PDR ADOCK 05000269 January 26, 1995 the accuracy of indications available to operators which would be used to ensure compliance with the Keowee administrative limits. The licensee agreed to provide this information to the staff. It was also agreed that the NRC reviewers would visit the site, if necessary, after receipt of this information to complete their review. After confirming Which additional information was needed by the staff, th, meeting was adjourned.

eonard A. Wiens, Senior Project Manager Project Directorate 11-3 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287

Enclosures:

1. Staff Questions
2. Meeting Attendees
3. Handouts cc w/enclosures:

See next page DISTRIBUTION w/enclosures 1 & 2 NRC & Local PDRs WRussell/F. Miraglia, 0-12 G18 RZimmerman, 0-12 G18 S. Varga G. Lainas OGC, 0-15 B18 E. Jordan, T-4 D18 ACRS (4), TWF G. Tracy, 0-17 G21 E. Merschoff, RH C. Berlinger, 0-7 E4 E. Weiss, 0-7 E4 F. Burrows, 0-7 E4 V. Beaston, 0-7 E4 B. Raughley, T-4 A9 W. Poertner, RH M. Shymlock, RH F. Ashe, 0-7 E4 D. Nguyen, 0-7 E4 S. Rosenberg, 0-10 E4 DISTRIBUTION w/enclosures 1, 2. & 3 Docket FTi1e E. Merschoff, RII PD23 R/F L. Wiens To receive a copy of this document, indicate in the box:

"C" = Copy without attachment/enclosu e "E" = Copy with attachment/enclosure "N" = N y

OFFICE LA:PD23:DRPE E

PM:PD23:DRPE E D:PD23:

EELB I

NAME LBerr LWiens:cw HBerlow CBerlinger DATE

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-2 the accuracy of indications available to operators which would be used to ensure compliance with the Keowee administrative limits. The licensee agreed to provide this information to the staff. It was also agreed that the NRC reviewers would visit the site, if necessary, after receipt of this information to complete their review. After confirming which additional information was needed by the staff, the meeting was adjourned.

Leonard A. Wiens, Senior Project Manager Project Directorate 11-3 Division of Reactor Projects -

I/II Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287

Enclosures:

1. Staff Questions
2. Meeting Attendees
3. Handouts cc w/enclosures:

See next page

Duke Power Company Oconee Nuclear Station cc:

A. V. Carr, Esquire Mr. Ed Burchfield Duke Power Company Compliance 422 South Church Street Duke Power Company Charlotte, North Carolina 28242-0001 Oconee Nuclear Site P. 0. Box 1439 J. Michael McGarry, III, Esquire Seneca, South Carolina 29679 Winston and Strawn 1400 L Street, NW.

Ms. Karen E. Long Washington, DC 20005 Assistant Attorney General North Carolina Department of Mr. Robert B. Borsum Justice Babcock & Wilcox P. 0. Box 629 Nuclear Power Division Raleigh, North Carolina 27602 Suite 525 1700 Rockville Pike Mr. G. A. Copp Rockville, Maryland 20852 Licensing - ECO50 Duke Power Company Manager, LIS 526 South Church Street NUS Corporation Charlotte, North Carolina 28242-0001 2650 McCormick Drive, 3rd Floor Clearwater, Florida 34619-1035 Dayne H. Brown, Director Division of Radiation Protection Senior Resident Inspector North Carolina Department of U. S. Nuclear Regulatory Commission Environment, Health and Route 2, Box 610 Natural Resources Seneca, South Carolina 29678 P. 0. Box 27687 Raleigh, North Carolina 27611-7687 Regional Administrator, Region II U. S. Nuclear Regulatory Commission Mr. J. W. Hampton 101 Marietta Street, NW. Suite 2900 Vice President, Oconee Site Atlanta, Georgia 30323 Duke Power Company P. 0. Box 1439 Max Batavia, Chief Seneca, South Carolina 27679 Bureau of Radiological Health South Carolina.Department of Health and Environmental Control 2600 Bull Street Columbia, South Carolina 29201 County Supervisor of Oconee County Walhalla, South Carolina 29621

AGENDA QUESTIONS

1.

LER 93-01 states that a load rejection test was performed on October 25, 1992-, and that the results of that test indicate that calculations used to establish acceptable Keowee operating limits (power, head, number of operating hydro units) are conservative.

Please provide the detail test results and discuss how they validate and relate to the calculations and results discussed in Duke's letter to the staff dated January 4, 1995.

Also, during the EDSFI conducted at Oconee, the inspection team was supplied with results from load rejection tests conducted during initial start-up, February 18 to April 15, 1971.

Please discuss how these results relate to the calculations and their results discussed in the January 4, 1995, letter. Discuss results from any other load rejection events or tests.

Duke's letter dated January 4, 1995, states that Evaluation KC Unit 1-2 0106 used a bench-marked computer model.

Please discuss what means were used to bench-mark this model.

2.

EDSFI inspection report for Oconee raised the issue of possible adverse effects on the Keowee auxiliary equipment during overvoltage/

overfrequency transients related to Keowee load rejection scenarios (Finding 2).

Duke letter dated November 1, 1994 (on corrective action for EDSFI findings) states-that analyses of the overvoltage/

overfrequency effects on the Keowee auxiliaries will not be completed until June 1, 1995. Please discuss how satisfactory operation of Keowee auxiliaries following load rejection scenarios is ensured without supporting tests or analyses being available.

Duke's letter of January 4, 1995, states that during overspeed transient Keowee output voltage remains relatively constant. Discuss voltage control circuits and any limitations for their operation.

3.

LER 93-01 discusses a scenario whereby the Keowee units could trip on overspeed. The LER implies that the setpoint for this trip is 140% of rated speed but no time delay value is discussed. Duke's letter of January 4, 1995, implies that the time delay may be 30 seconds but no setpoint for the overspeed is provided. Please provide the specific setpoints and time delays associated with all overspeed trips (normal and emergency) and discuss any corrective action associated with the overspeed trips resulting from the load rejection scenario in the LER.

ENCLOSURE 1

-2

4.

LER 93-01 references FSAR Section 15.14.3.3.6 as containing the requirements that ECCS flow be established within 48 seconds for the LOCA/LOOP scenario. Please provide a detailed discussion (using detailed timelines) of the sequence of events for a worst-case load rejection/overfrequency scenario which includes the worst-case values (considering uncertainties) for undervoltage relay reset, frequency relay setpoints (pickup and reset) and associated time delays, breaker closure times, retransfer startup time delays, etc. Compare this to the worst case sequence for a non-overfrequency scenario to provide the basis for margin between the current FSAR analyses and a worst-case load rejection scenario. Discuss any modifications and/or administrative controls that have been or will be implemented that ensure the analysis of FSAR Section 15.14.3.3.6 remains bounding.

5.

Duke's letter of January 4, 1995, states that overhead circuit parameters were used in lieu of the corresponding underground path parameters. Please provide detailed justification for the validity of this approach.

6.

Discuss the design basis for the Keowee/Oconee units, how commercial operation of the Keowee units fits into the design basis, how the load rejection/overspeed/overfrequency event impacts that design basis, and how the modifications and adminstrative controls ensure that the design basis is met.

MEETING ATTENDEES KEOWEE MODIFICATION REVIEW MEETING January 19, 1995 NAME ORGANIZATION owz

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Oconee Emergency Power Modification NRC-Duke Request For Additional Information Meeting January 19, 1995

Agenda

  • Introduction Oconee Power System Overview
  • Response to Request For Additional Information
  • Summary Oconee Emergency Power Modification Slide 1

Oconee Power System Overview Oconee Generator Through The Normal Auxiliary Transformer 230kV Switchyard Through The Startup Transformer One Keowee Unit Is Aligned Through The Overhead Path And Startup Transformer One Keowee Unit Is Aligned Through The Underground Path And Transformer CT4 The Dedicated 100 kV Path From A Lee Combustion Turbine Through Transformer CT5 Central Switchyard Through Transformer CT5 Any One Of The Above Can Power Both Main Feeder Busses Oconee Emergency Power Modification Slide 2

OCONEE NUCLEAR STATION Power System 230/525KV Keowee Lee Switchyards Hydroelectric CT Generators Generators 4 Double Circuit

-.44C) 230KV Lines IO 3 525KV Lines ovwhead iununuili muunuuuma nn ul nnuu nninanisi u

nnununsl un.nIai UJNIT su lu IIK 1 ~ ~~ 1 1 K1 SWICHYARD 1 T CT1 Keowe*

NORMAL STARTUP Lidwgrmwnd T SOU E

SOCE Feedor CT4 CT5

( To CT2 STANDB SKI IS SLI SL2 Al 11 1 A2 182 TOUNIT 2 TO UNIT 3 MAIN FEEDER MAI FEEDER N1 N2 MAINFEEDER El E2 Sl S2 MFc2 Oconee Emergency Power Modification Slide 3

Response to RAls

  • Keowee Emergency Power System Design Basis
  • Load Rejection Test Results
  • Analysis Of Operation Of Keowee Auxiliaries Following A Load Rejection
  • Keowee Overspeed Trip Setpoints Sequence Of Events Following A Keowee Load Rejection
  • Validation For The Use Of Overhead Circuit Parameters In Lieu Of The Corresponding Underground Path Parameters Oconee Emergency Power Modification Slide 4

Keowee Emergency Power Design Basis

  • Design Basis For The Keowee Emergency Power System Is To Provide The Emergency Power Needs For ONS Within The Committed Time Under All Applicable Conditions Assuming A Single Failure
  • FSAR Design Criterion
  • The Design of Keowee Is Such That It Can Perform Its Design Basis Function Whether Starting From Commercial Operation Or Standby Oconee Emergency Power Modification Slide 5

Keowee Emergency Power Design Basis Two Vulnerabilities Have Been Identified In The Keowee Emergency Power System And Are Currently Under Administrative Controls Zone Overlap Problem

  • Failure To Meet Single Failure Criterion
  • Overspeed/Overfrequency Problem
  • Failure To Meet Single Failure Criterion
  • Failure To Meet Design Basis Committed Time
  • Proposed Modification Will Correct The Above Identified Vulnerabilities Allowing Keowee To Meet Its Design Basis Oconee Emergency Power Modification Slide 6

Load Restrictions On Keowee

  • Spring 1971 Three 66MW Load Rejections for Startup
  • Oct. 25, 1992 Load Rejection Test at 79MW
  • Jan. 1993 66MW Load Restriction Established
  • Feb. 1993 LER 93-01 Rev. 0 Issued
  • March 6, 1993 Load Rejection Testing Performed 1 Unit Rejecting from 75MW, 85MW and 93MW
  • May 22, 1993 Emergency Startup Testing
  • June 1993 New Limits for Keowee Generation Issued
  • Dec. 1994 Calculation for Modification Completed Oconee Emergency Power Modification Slide 7

Keowee Auxiliaries Analysis

  • The Proposed Modification Will Eliminate The Overfrequency Concerns By Preventing The Auxiliaries From Being Exposed To Overfrequency Conditions
  • Therefore, No Analysis Of The Overfrequency Effects On The Keowee Auxiliaries Will Be Necessary
  • Keowee Output Voltage Is Controlled By The Voltage Regulator Independent Of Frequency Oconee Emergency Power Modification Slide 8

Keowee Overspeed Trip Setpoints

  • The Purpose Of The 140% Speed Switch Contact Discussed In The LER Was To Provide Governor Failure Protection
  • Inadequate Design Which Resulted In The Overspeed Problem
  • Proposed Modification Eliminates Overspeed Problem While Maintaining Governor Failure Protection
  • Currently, Administrative Limits In The Keowee Modes Of Operation Procedure Preclude An Overspeed Trip Following A Load Rejection Oconee Emergency Power Modification Slide 9

.Keowee Load Rejection Sequence Basis For This Modification Is To Ensure That The Keowee Emergency Power System Meets Its Design Basis The Committed Time Of 48 Seconds For ECCS Injection Is Described In The FSAR

[Keowee/EPSL Time] + [MOV Stroke Time] < 48 Seconds

[Keowee/EPSL Time] < 33 Seconds Review Of The Worst Case Load Rejection And Non-Load Rejection Scenarios Indicates That The Committed Time Will Be Met Following Implementation Of The Modification The Administrative Limits In The Keowee Modes Of Operation Procedure Will Be Revised With The Implementation Of The Modification Oconee Emergency Power Modification Slide 10

PRE-MODIFICATION KEOWEE/EPSL SEQUENCE OF EVENTS FOR NON-LOAD REJECTION SCENARIO KEOWEE UNITS NOT PREVIOUSLY ONLINE @ T=O OH PATH ACBRO.OSES t "52 TIMERS TNEOUT

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BDTHMEOWEE BKRREC.OSE STARTUP COMMlOTED TIME U(MU TMERS TIME DELAY FOR LOCAUNiTO START (6.5 1 0.5 sec)

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LOCA UNIT LOOP SK A SBKA UNITS"E" CSE BRKSCLOSE TRANsFEm TO STANDBY TIME DELAY LOCA UNIT (10.0 0.5 sec)

LOCA UNIT "E" BKRS XFER TO STBY 27E RELAYS CLOSE&

PERMISSWVE RESET EUR NB LOCA UNITk LOADSHED T-1 T-B.5 T-11 T.15 T25 T.33 T-0 LOCA/LOOP START (SECONDS)

Oconee Emergency Power Modification Slide 11

PROPOSED MODIFICATION NSM-ON-52966 KEOWEE/EPSL SEQUENCE OF EVENTS FOR NON-LOAD REJECTION SCENARIO KEOWEE UNITS NOT PREVIOUSLY ONLINE @ T=O OH PATH ACS COSES "52 TIMERS TMEOUT RTRIN:BE BOTH IEOWEE BKR RECLOSE ST COMMTED TIME UNITS EMER.

TERSSTARTUP FOR LOCA UNIT TO START (9.0 +/- 0.5 sec)

(5.0 05 sec)

ENERGEMs LOCA UNIT LOOP SK & S BKR UNITS"E" CLOSE BRKSCLOSE TRANSFER.

TO STANDBY TIME DELAY LOCA UT (10.0 0.5 sc)

LOCA UNIT EBKRS LOCA UNIT XFER TO STBY 27E RELAYS

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LOADSHED PRPAISSWE RESET ENEME B

T-1 T-9 T-11 T-15 T-20 T-33 T-0 LOCAILOOP EIMEENCY START (SECONDS)

Oconee Emergency Power Modification Slide 12

PRE-MODIFICATION KEOWEE/EPSL SEQUENCE OF EVENTS FOR WORST CASE LOAD REJECTION SCENARIO KEOWEE UNITS ONLINE (GENERATING MAX MW) (a T=O KEOWEEOH BKR CLOSES COMMITTED TIME FOR LOCA UNIT TO S2 TIMERS TIE OUT 98R FE-CLOSE KEOWEE OH GBs TIMRS TRPPED F (6.5 1 0.5 sec)

TO GRID @T0 RENFER STARTUP TIME DELAY tacAUNIT SK (1o.o f o.s sec)

AND S BKRS C LDSE TRA.NSFER TO LOOP STANDBY A

UNITS E TIME DElAY BRKS CLOSE (10.0 1 0.5 sec)

LOCA LIT XFER TO STBY LOCA UNIT 'E" PERMISSIVE BKRS CLOSE &

LOCAUNIT 27E RELAYS ENEFIGEMFB LOA DNI RESET T-1 T615 T-1I T-24.2 T-33 T. 34.2 LOCALOOP START (SECONDS)

Oconee Emergency Power Modification Slide 13

PROPOSED MODIFICATION NSM-ON-52966 KEOWEE/EPSL SEQUENCE OF EVENTS FOR WORST CASE LOAD REJECTION SCENARIO KEOWEE UNITS ONLINE (GENERATING MAX MW) a T=O wCA UNIT SK AND S 91(S CLOSE C MMITTED TIME FOR LOCA UNIT TO "S2" TIMERS IENERGR2EMFBs TNE OUT PRESELECTED BR RECLOSE KEOWEE GBs Q.OSE ALL KEOWEE GBs TRPPED F GM (9.0 +/- 0.5 sec)

TOGRKD@T-0 RETRASFE TO

"* TIMERS KEDWE UNITS STARTUP TNE OUT RETURN TO TIME DELAY KR PERMISSIVE

<110%SPEED (5.0 t 05 sec)

TIMERS (11.0 1 0.5 sec)

"81 FREOUENCY LOOP RELAY PKEUP UNITS E

@110%RATED BRKS(COSE LOCA UNIT XFER TO STBY LOCA UNIT "E" BKRS CLOSE &

27E RELAYS ENfREMFB LOCAUNIT RESET LOADSHED T-1 T-2 T-9 T-11 T-22 T-26 T-31 T-33 T-0 LOCA/LOOP START (SECONDS)

Oconee Emergency Power Modification Slide 14

OP/O/A/2000/041 s of s ENCLOSURE 4.9 GENERATOR OPERATING LIMITS 74Mw Keowee Operating Chart c7o 69 665

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Oconee Emergency Power Modification Slide 15

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Underground Overfrequency Simulation

  • Since The Underground Path Model Was Not Yet Developed, The Overhead Model Was Used As A Test Case To Simulate The Emergency Loading Of The Underground Path
  • Validation Of The Use Of Overhead Path Parameters For This Test Case Is Not Necessary Since The Conclusion Was Unfavorable Oconee Emergency Power Modification Slide 16
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