ML20057E916

Summary of 930913 Meeting W/Westinghouse Owners Group in Rockville,Md Re Rod Control Sys Program in Response to Generic Letter 93-04 Rod Control System Failure & Withdrawal of Rod Control Cluster Assemblies

ML20057E916
Person / Time
Issue date:	10/05/1993
From:	Alexion T Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
GL-93-04, GL-93-4, NUDOCS 9310130370
Download: ML20057E916 (28)

Text

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UNITED STATES

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October 5, 1993 WESTINGHOUSE OWNERS GROUP

SUMMARY

OF MEETING ON SEPTEMBER 13, 1993, REGARDING WESTINGHOUSE OWNERS GROUP UPDATE ON R0D CONTROL SYSTEM PROGRAM, IN RESPONSE TO GENERIC LETTER 93-04 On September 13, 1993, representatives of the Westinghouse Owners Group (WOG) met with the NRC staff to present an update on their Rod Control System Program, in response to Generic Letter 93-04, " Rod Control System Failure and Withdrawal of Rod Control Cluster Assemblies." Meeting attendees are listed in Enclosure 1.

Slides presented by WOG are in Enclosure 2.

The Owners Group summarized their activities thus far. These included current order failure assessment, the test program and rod control performance history review.

Their conclusion of the overall WOG program was that General Design i

Criterion (GDC) 25 continues to be met. The WOG has, however, identified two options to enhance reliability. Option A consists of new current order surveillance and current order timing changes. Option B consists of the new current order surveillance and new safety analyses.

At the conclusion of the meeting, the staff indicated that:

1) the failure rate data and system test data provided by the WOG do not demonstrate compliance with GDC 25, 2) the reliability enhancement options are a reasonable approach to resolution, and 3) any licensee stating that they meet j

GDC 25 without adopting one of the enhancements will need to provide substantial justification.

V

((}1 fib Thomas W. Alexion, Project Manager Project Directorate IV-1 Division of Reactor Projects - III, IV, V Office of Nuclear Reactor Regulation

Enclosures:

1.

List of attendees 2.

Slides l

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9310130370 931005 I

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October 5, 1993 WESTINGHOUSE OWNERS GROUP

SUMMARY

OF MEETING ON SEPTEMBER 13, 1993, REGARDING WESTINGHOUSE OWNERS GROUP UPDATE ON R0D CONTROL SYSTEM PROGRAM,-IN RESPONSE TO J

GENERIC LETTER 93-04 On September 13, 1993, representatives of the Westinghouse Owners Group (WOG) met with the NRC staff.to present an update on their Rod Control System Program, in response to Generic Letter 93-04, " Rod Control System Failure and Withdrawal of Rod Control. Cluster. Assemblies." Meeting attendees are listed.

in Enclosure 1.

Slides presented by WOG are in Enclosure 2.

The Owners Group summarized their activities thus far. 'These included current'.

l order. failure assessment, the test program and rod control performance history

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review. Their conclusion of the overall WOG program was that General Design Criterion (GDC) 25 continues to be met. The WOG has, however, identified two options to enhance reliability. Option A consists of new current order-j surveillance and current order timing changes. Option B consists of the new.

current order surveillance and new safety analyses.

At the conclusion of.the meeting, the staff indicated that:

1) the failure rate data.and system test data provided by the WOG do not demonstrate i

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compli.ance with-GDC 25, 2) the reliability enhancement options are a t

reasonable approach to resolution, and.3)- any licensee stating that they meet GDC 25 without adopting one of the enhancements will need to provide _-

substantial justification.

i ORIGINAL SIGNED BY:'

Thomas W. Alexion, Project Manager Project Directorate IV-1 Division of Reactor Projects - III, IV, V Office of Nuclear Reactor Regulation

Enclosures:

1.

List of attendees 2.

Slides av 0FC LA:PD4-l' PM:P M LSRX?nk SL h BC,:,SI/B E;DSSA ),

DPD4-1_a NAME Phoohdn TAlexi'$h MChaIterton RPerch RJ b s bANab WBecNer DATE 9 /T/93 9/N/93 9/k/93' 9/22/93 M 93 f/8/93

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V 0FFICIAL RECORD COPY Document Name: W0GSepl3.mts l

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September 13, 1

3 Meeting with WOG - Update on Ray r

'rol System Program list of At' w e, j

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Name Oraanization Phone Tom Alexion NRC/NRR

-301-504-1326 l

Ashok Thadani NRR 301-504-2884 Tim Collins NRR 301-504-2897 Hukam Garg NRR 301-504-2929 l

Margaret Chatterton NRR 301-504-2889 Robert Perch NRR 301-504-3236 Daniel Risher.

M 412-374-5774 Daniel Huegez Wolf Creek 316-374-5424 l'

Dimitri Gournelos M

-316-636-6834 Larry Walsh NAES Corp. (WOG Chair) 603-474-9521 Bryce Shriver Virginia Power (WOG SEES Chair) 804-273-2721 1

Steve Fowler M Reliability Engineering 412-374-6071 l

Tony Baker M Nuclear Safety 412-374-5818 Mark Proviano W Safety Licensing 412-374-5651 Chris Vertes M Transient Analysis

_412-374-4481 Bob Eliasz Rochester Gas & Electric 716-724-8075 Dave Campbell M WOG Project Office' 412-374-6206 James J. Raleigh Southern Technical Services 301-652-2500'

-i Roger Huston TVA David 0 Best PSE&G.

301-770-6790 609-339-1957 Clair Edgar RG&E 315-524-4446 Bert Yates UE 314-554-3573 Steve Mannon PSE&G - Salem. Licensing 609-339-1129 Joe Wilder Rochester Gas & Electric 315-524-4446 George Wrobel Rochester Gas & Electric

716-724-8070 l

Harry Majors Southern Nuclear Operating Co.

205-877-7079-Terry Hampster NAESCO 603-474-9521 Robert A. Gwinn NAESCO 603-474-9521 Anthony Pfeffer SERCH Licensing-Bechtel 301-417-8816 Jacob Zimmerman NRR 301-504-2426 Greg Rawa Rochester Gas & Electric 315-524-4446 j

James Stone NRC/NRR/PDI-2 301-504-1419 Al Johnson

'NRC/NRR/PDI-3 301-504-1497 Jeffrey Bass W Licensing '

414-221-2002 j

412-374-4262 l

Roger Newton WEPC i

2 WESTINGHOUSE OWNERS GROUP i

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UPDATE ON ROD CONTROL SYSTEM EVENT i

September 13, 1993 1:00 - 4:00 i

ROOM 4B11, White Flint i

Rockville, MD WOG-NRC Meeting 9/13/93:1

1 AGENDA FOR SEPTEMBER 13, 1993 WOG/NRC MEETING ON WOG RESPONSE TO NRC GENERIC LETTER 93-04 i

INTRODUCTION

- Roger Newton, WOG PURPOSE i

e-WOG ACTIVITY

SUMMARY

GDC 25 DETERMINATION / BASES SAFETY SIGNIFICANCE OF POTENTIAL ASYMMETRIC ROD MOTION i

e PROGRAM CONCLUSION I

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ROD CONTROL SYSTEM

- Bryce Shriver, WOG EVALUATION PROGRAM SAFETY ASSESSMENT OF

- Dave Huegel, E ROD CONTROL-FAILURES RECOMMENDATION OF

- Roger Newton, WOG ENHANCEMENTS WOG RECOMMENDATIONS TO UTILITIES WOG FUTURE ACTIONS WOGWRC Meeting 9/13/93:2 i

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1 INTRODUCTION e

OPENING REMARKS e

MEETING PURPOSE PURPOSE e

SUMMARIZE WOG ACTIVITIES e

PRESENT THE GDC 25 DETERMINATION AND BASES REITERATE THAT THERE IS NO SAFETY SIGNIFICANCE WITH AN ASYMMETRIC ROD WITHDRAWAL-e DISCUSS THE WOG EVALUATION PROGRAMS e

DISCUSS SAFETY ASSESSMENT OF FAILURES e

PRESENT WOG RECOMMENDATIONS e

SUMMARIZE WOG FUTURE ACTIONS i

WOG-NRC Meeting 9/13/93:3

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SUMMARY

OF WOG ACTIVITIES i

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June 14 WOG/NRC Meeting in Bethesda, Md i

1 June 25 WOG RRG Letter issued to all members outlining RRG effort related to Salem Rod Control System Event (OG-93-39) 1 July 9 WOG/NRC Meeting in Rockville, Md l

July 14 WOG Request to NRC for Schedular Relief on GDC-25 Determination'(OG-93-44) l July 26 NRC Letter granting relief i

July 30 WOG 45 day generic response transmitted to all j

members (OG-93-53)

August 5 45 day response submitted to NRC August 5 WCAP-13803 transmitted to NRC (OG-93-55)

August 9-11 Rod control testing performed at Salem Training j

Center September 3 WOG Status Report sent to NRC (OG-93-75)

September 9 WOG 90 day generic response transmitted to all

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members (OG-93-77) j September 13 WOG/NRC Meeting in Rockville, Md September 20 90 day licensee response due to NRC WOG-NRC 1.lecting 9/13/93:4 4

GDC 25 DETERMINATION THE WOG HAS MADE THE DETERMINATION THAT GDC 25 CONTINUES TO BE MET BASES SINGLE FAILURE -

All CRDMs in a given group receive the same signals.

CARD FAILURE

~2.1 E-4 Failures /

FREQUENCY Critical Reactor Year

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~2.6 E-5 Salem-Type Failures /

Critical Reactor Year i

l ACCEPTANCE CRITERIA -

Satisfy the appropriate criterion based on frequency of occurrence i

WOG-NRC Meeting 9/13/93:5 l

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SAFETY SIGNIFICANCE OF POTENTIAL ASYMMETRIC ROD MOTION f

FOR SALEM-TYPE FAILURE EVENTS EXTREMELY LOW PROBABILITY OF OCCURRENCE FAILURE IS DETECTABLE THROUGH EXISTING TECH SPEC SURVEILLANCE THREE - DIMENSIONAL SAFETY ANALYSES DEMONSTRATED THAT ALL AFFECTED WESTINGHOUSE PLANTS WOULD CONTINUE TO MEET DNB DESIGN BASIS WOG-NRC Meeting 9/13/93:6

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WOG PROGRAM CONCLUSION q

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GDC 25 CONTINUES TO BE MET i

WOG GENERATED 2 OPTIONS TO ENHANCE t

RELIABILITY t

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m OPTION A -

New Current Order Surveillance.and Current Order Timing Changes j

u OPTION B -

New Current Order Surveillance and New Safety Analyses j

l WOG-NRC Meeting 9/13/93:7

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WOG ROD CONTROL SYSTEM EVALUATION PROGPdM PURPOSE:

Determine the types of motion that can occur when CRDMs are subjected to corrupted current orders j

PROGRAM ELEMENTS:

Current Order Failure Assessment Test program Rod Control Performance History Review ORGANIZATION:

Directed by the WOG System & Equipment Engineering Subcommittee Managed by SE&E Chairman, Bryce Shriver, Virginia Power Participation by several other utilities Included Westinghouse Rod Control and CRDM expertise WOG-NRC Meeting 9/13/93:8

CURRENT ORDER FAILURE ASSESSMENT:

FOCUS:

Identify corruptions of current orders that have the potential to result in non-uniform rod motion within a group of rods PURPOSE:

Determine what single failure modes exist that can corrupt the e

current orders Determine the effects of the corrupted current orders on rod e

motion CONCLUSIONS:

Only 6 types of Logic Cabinet circuit cards can corrupt current orders.

Identical corrupted current orders are applied to all rods in the affected group.

No failures result in rod motion unless a demand signal is present.

For no failure modes is the ability of the Reactor Protection e

System to trip the reactor compromised.

WOG-NRC Meeting 9/13/93:9

CURRENT ORDER FAILURE ASSESSMENT (CONT):

CONCLUSIONS (CONT):

e Failure modes exist that affect one group and have the potential to result in less than the complete group of rods to move in the demanded direction.

The Salem-type failure is the only mode where rods can move in the opposite direction than demanded (with standard timing).

Other failure modes exist that can corrupt the current orders, but e

which result in normal rod motion USES OF FAILURE ASSESSMENT RESULTS:

e Determine which failure modes should be included in test program Assess significance of reported failures e

Determine effects of recommended current order timing changes e

WOG-NRC Meeting 9/13/93:10 l

i ROD CONTROL SYSTEM TEST PROGRAM:

1 1

FOCUS:

Perform tests in a training facility rather than an actual plant to l

determine the key parameters that affect rod motion in the presence of corrupted current orders PURPOSE:

Determine why CRDMs, when subjected to Salem-like corrupted current orders, respond inconsistently Observe how CRDMs respond to certain failure modes, where i

analysis was inconclusive Provide a basis for identifying where plant response may result in inconsistent motion in the presence of corrupted current orders j

CONCLUSIONS:

Rods can move inconsistently to Salem-type corrupted current orders Timing changes can prevent rod movement in the presence of the Salem-type failure WOG-NRC Meetmg 9/13/93:11 I

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ROD CONTROL SYSTEM TEST PROGRAM: (CONT) i USES OF TEST RESULTS:

Correlate test results of dry CRDM response times to CRDMs e

in wet, plant conditions (plant response is slower) 1 l

Verify feasibility of timing order change i

e Verify Failure-Assessment effects on CRDM response l

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INDUSTRY PERFORMANCE REVIEW:

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-i FOCUS:

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o Rod Control System Logic Cabinet failures i

Plant events where rods moved incorrectly.

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e PURPOSE:

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Collect information on Rod Control System performance, concentrating on Logic Cabinet failures:-

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PC cards, pcwer supplies, wiring and connectors 1

e From initial criticality to May 1993 e

Identify operational events where:

o Less than full group moved' t

Rods were stuck i

Rods were misaligned i

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i INDUSTRY PERFORMANCE REVIEW: (CONT) i i

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CONCLUSIONS:

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In addition to Salem, only one other event where 1 rod moved i

out when group moved in -- due to incorrectly wired CRDM l

i and caught during pre-operational testing Salem event represents failure rate of 2.6E-5 critical reactor i

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years j

l Only 8 card failures (including Salem) in over 270 million j

critical card hours had potential to cause less than entire group j

i to move when motion demanded (failure rate of 2.lE-4/ critical i

reactor years)

Forty-one card failures were associated with cards that can corrupt current orders j

i Total of 189 Logic Cabinet circuit card failures reported (failure j

rate of 4.9E-3/ critical reactor years)

WOG-NF.C Meeting 9/13/93:14

1 SAFETY ASSESSMENT OF ROD CONTROL SYSTEM FAILURES l

POTENTIAL FAILURE SCENARIOS IDENTIFIED FROM l

FAILURE ASSESSMENT i

l DEMONSTRATE TH.AT POTENTIAL FAILURE l

l SCENARIOS ARE BOUNDED BY EXISTING LICENSING BASIS EVENTS l

I WOG-NRC Meeting 9/13/93:15 l

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POTENTIAL FAILURE SCENARIOS b

Failures Rod Demand Failure Scenario 1*

IN or OUT One group IN, Other group OUT i

2 IN or OUT One group stationary, Other group IN or OUT reliably 3

OUT One group OUT reliably, Other group one rod to entire group OUT reliably j

4 IN One group IN reliably, Other group one rod to entire group IN reliably 5

OUT One group OUT reliably, Other group rods move OUT reliably, remain stationary or ratchet IN 6

IN One group IN reliably, Other group rods move IN, remain stationary or ratchet IN 7

IN or OUT One rod to entire group move OUT or remain stationary (Salem failure) 8 IN or OUT No effect on rod motion until second failure created (if second failure -

rods may move IN and/or OUT)

Similar to Ginna failure scenario WOG-NRC Meeting 9/13/93:16

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SAFETY ASSESSMENT OF POTENTIAL t

FAILURE SCENARIOS i

Failure Detectable Bounded by 1

Yes Dropped Rod event 2

Yes Dropped Rod / Rod Misalignment events 3

Yes Dropped Rod event 4

Yes Rod Misalignment event 5

Yes Dropped Rod event 6

Yes Dropped Rod / Rod Misalignment events 7

Yes WCAP-13803, Revision 1 8

Yes*

No effect l

With new current order surveillance in place l

WOG-NRC Meeting 9/13/93:17

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SAFETY ASSESSMENT CONCLUSIONS Scenarios 1-6 are bounded by;RCCA Misalignment or Dropped Rod events (DNB events).

Scenario 7 (Salem-type incident) shown to meet DNB Design Basis using 3-D analysis methods (WCAP-13803, Revision 1) or can be precluded by current order timing adjustments.

Scenario 8 does not result in any improper RCCA movement.

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l WOG-NRC Meeting 9/13/93:18

I CONCLUSIONS OF OVERALL

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WOG PROGRAM e

GDC 25 CONTINUES-TO BE MET m

SINGLE FAILURE EFFECTS a

CARD FAILURE FREQUENCY m

ACCEPTANCE CRITERIA e

RECOMMENDATIONS OF ENHANCEMENTS m

OPTION A -

New Current Order Surveillance and Current Order Timing Changes m

OPTION B -

New Current Order Surveillance and New Safety Analyses WOG-NRC Meeting 9/13/93:19 i

I RECOMMENDED SURVEILLANCE TESTING GOAL:

To ensure that those potential single failurt.s that corrupt current orders but do not result in rod mis-stepping _are' detected.

METHOD:

Record the current orders being applied to each group of I

CRDMs and compare them to the design current orders.

PROCEDURE:

1.

Perform recording during post-refueling rod drop testing.

2.

Monitor the current being applied to each CRDM coil from Power Cabinet test points provided for this purpose.

j 3.

Make recording of both withdrawal and insertion sequences for each group of CRDMs.

4.

Compare the recordings to design current traces.

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WOG-NRC Meeting 9/13/93:20 l

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RECOMMENDED TIMING CHANGE i

GOAL:

Ensure that, when Salem-like corrupted current orders are.

present, affected control rods.will not move.

Ensure that the current order timing change has no impact 'on' o

normal Rod Control System operation.

METHOD:

With the revised timing, the lift coil energizes and raises the movable gripper assembly prior to the movable gripper engaging the drive rod.

Timing chariges are accomplished on the Logic Cabinet decoder e

cards, designed for this purpose.

I PROCEDURE:

1.

Advance the lift current order for insertion sequence.

2.

Retard the movable current order for withdrawal sequence.

3.

Retard the remaining withdrawal current orders to maintain normal timing relationship.

WOG-NRC Meeting 9/13/93:21 -

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RECOMMENDED SAFETY ANALYSIS GOAL:

To ensure that if Salem-type corrupted current orders are l

present, the limiting asymmetric rod withdrawal event meets the DNB Design Basis using three-dimensional analpical methods.

METHOD:

A)

WCAP-13803, Revision 1, OR B)

Plant-specific LOFT 5 Analyses PROCEDURE:

A. 1.

Submit WCAP-13803, Rev 1, for NRC review /

approval A. 2.

Continue to Assess Asymmetric Rod Withdrawal as a Licensing Basis Event OR B. 1.

Submit plant-specific LOFT 5 Analyses for NRC review / approval B. 2.

Continue to Assess Asymmetric Rod Withdrawal as a Licensing Basis Event WOG-NRC Meetirg 9/13/93:22

WOG RECOMMENDATIONS TO UTILITIES AFFECTED WESTINGHOUSE PLANTS CONTINUE TO' MEET GDC 25 (OR EQUIVALENT)

THE WOG HAS IDENTIFIED 2 OPTIONS TO ENHANCE RELIABILITY TECHNICAL MEETING FOR ALL UTILITIES AT 4:30 IN W ROCKVILLE OFFICE

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l WOG-NRC Meeting 9/13/93:23 i

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WOG FUTURE ACTIONS e

PRIMARY ACTIVITY Demonstrate that recommended timing changes will preclude rod motion for a Salem-type failure and have no impact on normal operation.

e TRANSMITTALS TO UTILITIES Results of timing demonstration at an operating plant a

Directions on new surveillance testing a

Westinghouse Technical Bulletin for new timing changes a

WOG-NRC Meeting 9/13/93:24 l

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DISTRIBUTION - Meetina Summary

Docket File

NRC & Local PDRs PD4-1 Reading T. Murley/F. Miraglia J. Partlow J. Roe E. Adensam H. Rood T. Alexion P. Noonan OGC E. Jordan E. Rossi Receptionist OWFN NRC Participants ACRS (10)

V. McCree, EDO L. Plisco, EDO G. Grant, ED0 J. Mitchell, EDO R. Cooper, RI E. Merschoff, RIl E. Greenman, RIII A. B. Beach, RIV K. Perkins, RV l

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