ML20133N149

Informs of Periodic Review of Low Priority GSI to Identify New Info Which May Warrant Reassessment of Issue,As Requested in 950118 Memo

ML20133N149
Person / Time
Issue date:	04/07/1995
From:	Jordan E NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:	Beckjord E NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
Shared Package
ML20133N127	List: ML20133N124 ML20133N149
References
CON-NRC-04-97-036, CON-NRC-4-97-36, REF-GTECI-107, REF-GTECI-156, REF-GTECI-NI, TASK-107, TASK-156, TASK-OR NUDOCS 9701230176
Download: ML20133N149 (1)

Text

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f NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Serpan (

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MEMORANDUM T0:

Eric S. Beckjord, Director ,

Office of Nuclear Regulatory Research FROM:

irector ff c or Analysis and Evaluation of erational Data l

SUBJECT:

PERIODIC REVIEW 0F LOW PRIORITY GENERIC SAFETY ISSUES In response to your subject memorandum of January 18, 1995, we have reviewed the list of low priority generic safety issues to identify new information which may warrant reassessment of the issue.

We identified only one, G1 107, which may be affected by the results of an ongoing AE00 study. We also have planned a study of dc power which will be broader in scope than G1 156.3.6.2.

Generic Safety issue 107 Main Transformer Failures AE0D has a study on grid performance in progress. This study includes transformer failures caused by grid problems or grid problems due to transformer failures. Our review of operating experience indicates that transformer failures in the past several years suggest a failure rate that is a factor of about 3 greater than the base case failure frequency used in GI 107.

I Generic Safety Issue 156.3.6.2 Emergency DC Power AE0D has published a program plan for evaluation of dc power systems.

The objective of this study would be to evaluate recent operating experience for dc power systems and draw conclusions about the i

effectiveness of applicable requirements and industry actions for these The scope of this program systems in light of the operating is beyond that in G1 156.3.6.2 experience.which only addresses the concern tha safety-related de power system bus voltage monitoring and annunciation We provided a may not adequately notify operators of dc bus status.

copy of our program plan for de power systems in a March 2, 1995, memo from Charles E. Rossi to Lawrence C. Shao (among others) of your office.

cc: W. T. Russell, NRR L. C. Shao, RES M. W. Hodges, RES T. T. Martin, RGN-1 S. D. Ebneter, RGN-Il J. B. Martin, RGN-Ill L. J. Callan, RGN-IV 9701230176 970108 PDR CONTR NRC-04-97-036 PDR

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MEMORANDUM TO: Dptd h Norftseef Directw Office 'of'N0ttear Regulatory Research William T. Russell, Director ,[AJ FROM:

Office of Nuclear Reactor Regulation

SUBJECT:

PERIODIC REVTEW OF LOW-fRIORITY GENERIC ISSUES NRR has reviewed the list containing all low-priority generic safety issues (GSIs) provided in your memorandum dated February 16, 1996, to determine whether there is any new information that would necessitate The review resultedreassessment of in recommending the original prioritization cvaluations.that two GSIs be raised in priority to me and two GSIs be combined into one. The bases for these recommendations arj given below. l GSI A TORNADO MISSILES '

This issue should be closed as resolved, based on SECY-93-087, " Policy, i Technical, and Licensing Issues Pertaining to Evolutionary NUREG-1503, and Evaluation

" Final Safety Advanced Light- l Water Reactor Designs," April 2, 1993:

Report Related to the Certification of the Advance Boiling Water Reactor Design," July 1994; and NUREG/CR-4661, "Toraado climatology of the United States," May 1986. basis tornado wind speed-(which is the ir, tent of A-38) nuclear power plants. See also our safety evaluation (Attachment 1) for ,

WNP-2, which also' allowed a reduction in design basis tornado wind speeds.

REC 0t#4ENDATION: ISSUE SHOULD BE CLOSED GSI 81 - IMPACT OF LOCKED D0 ORS AND BARRIERS ON PLANT Issues 81 and 122.3 have been reviewed, and there is no new information that Since these issues are would necessitate reassessment of these issues. essentially the same into Issue 81. Issue 122.3 should then be considered closed.

RECOMMENDATION: INTEGRATE ISSUE 122.3 INTO ISSUE 81 AND CONSIDER ISSUE 122.3 CLOSED CONTACT: Tom Greene, PECB/DRPM/NRR (301) 415-1175 9 4 c % =i & W ^ 3,,.

I gm] 11,19rg D. L. Morrison ESI 107 - MAIN TRANSFORMER FAILURES This issue was very close to being prioritized Medium but further analysis (including consideration of potential benefits from station blackout On March 17, resolution) resulted in it being given a Low Priority ranking.

1996, the Electrical Engineering Branch provided a brief report (Attachment This 2) to the Director of ADT on recent events involving transformer failures.

report is being provided to RES for your consideration.

RECOMMENDATION: RAISE PRIORITY TO MEDIUM GSI 122.3 - PHYSICAL SECURITY SYSTEM RESTRAINTS See GSI 81.

SSI 152 - DESIGN BASIS FOR VALVES THAT MIGHT BE SUBJECT TO S BLOWOOWN LOADS A motor-operated valve (MOV) testing program conducted by the Electric Power Research Institute (EPRI) has provided significant information regarding In the performance of safety-related gate, globe and butterfly valves.

particular, EPRI found that a high percentage of gate valves wer during blowdown testin Although EPRI tested only one globe valve predict the thrust requirements.under high temperature and blowdown cond '

significantly higher thrust requirements than predicted.

load-sensitive behavior (or rate of loading) can reduce actuator thrust ' output The Nuclear Energy Institute submitted EPRI Topical under dynamic conditions.

Report TR-103237, "EPRI M0V Performance Prediction Program," describing the methodology developed by EPRI to predict dynamic thrust and torque requirements for gate, globe, and butterfly valves without dynamic tests by licensees. The staff has prepared a safety evaluation which approves the topical report for use and reference with certain conditions and limitations.

EPRI has provided the results of its MOV test to licensees through industry meetings. The NRC staff has disseminated the results Someof the EPRI licensees have H0V test program to licensees through notices and public meetings. Based on the already incorporated this information into their M0V programs.EP

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Ag-il 11,1993 D. L. Morrison valves (principally gate valves), we request that you re-evaluate the priority level of GSI 152, ' Design Basis for Valves that might be subject to Significant Blowdown Loads."

RECOMMENDATION: RAISE PRIORITY TO NEDIUM Attachments:

1. Safety Evaluation for Revised Tornado Design Criteria at Washington Nuclear Power Project No. 2 (WNP 2)(TAC FM88626), memorandum to James W. Clifford, POIV-2/NRR from Conrad E. McCracken, Plant Systems Branch /NRR dated November 27, 1995 '

2. Transformer Failures, note to Ashok Thadani, ADT/NRR thru Gus C. Lainas, DE/NRR, from Jose Calvo, EELB/DE/NRR, dated March 7,1996 l

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James W. Clifford, Senior Project Manager MEMORANDUM TO: Project Directorate IV-2 Division of Reactor Project > ill/IV Office of Nuclear Reactor Regulation Conrad E. McCracken, Branch Chief FRON:

Plant Systems Branch Division of Systems Safety and Analysis Office of Nuclear Reactor Regulation

SUBJECT:

SAFETY EVALUATION FOR REVISED TORNADO DE WASHINGTON NUCLEAR POWER PROJECT NO. 2 (WNP-2)

(TAC No. M88626)

WPPSS Nuclear Power Project No. 2 (WNP-2)

Plant Name: Washington Public Power Supply System (WPPSS)

Licensee:

Status: Ccaplete 10, 1995 The Plant Systems Branch (SPLB) reviewed the licensee's OctoberThe licensee' request to revise the tornado design criteriaAsfor WNP-2.for a result l criteria were overly con <ervative relative to the -lant location. is l l

of our review we concluded that the licensee's proposed acceptable.

j If you have any questions regarding this evaluation for our conclusion. 425-3285.

please contact Bil' leFave at We consider our efforts on Our SALP input is also provided as Attachment 2. ,

TAC No. M88626 to be complete.

Docket No. 50-397 Attachments: As stated (2)

SPLB R/F Plant R/F Docket File JLyons DISTRIBUTION:_ Central File GHubbard SWest WLeFave DOCUMENT NAME: G:\SECTIONA\LEFAVE\WNP88626

• see previous concurrence SPLB:DSSA h S

• SPLB:DSSA

• SPLB:DSSA CEMcCracken GTHubbard WLeFave 11/)//95 11/27/95 11/27/95

'0FFICIAL RECORD COPY Attactrent 1

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION DIVISION OF SYSTEM SAFETY AND ANALYSIS PLANT SYSTEMS BRANCH REVISED TORNADO DESIGN CRITERIA WASHINGTON PUBLIC POWER SUPPLY SYSTEM NUC DOCKET NO 50-397

1.0 INTRODUCTION

Washington Public Power Supply System design (WPPSS By letter dated October 10, 1995 or the licensee) requested the staff's approval to revise The WNP-2 the tornado criteria for the Nuclear Power Project Unit 2 plant, (WNP The proposed 300 miles per hour (mph) rotational and 60 mph translational. submittal 10, 1995 h would change, as requested in the Octobercriteria to establish the total des (160 mph rotational and 40 mph translational).

design basis tornado characteristics (for the tornado intensity regio which WNP-2 is located) accepted by the staff in theRep Design, NUREG-IS03, July 1994.

2.0 EVALUATION The current licensing basis tornado design criteria for WNP-2 i are ba Region I plant site as defined in Regulatory Guide (RG) 1.76 " Des Tornado for Nuclear Power Plants." The licensee's d in RG because it is located in Region Ill as defined in RG 1.76 for a design basis Region III tornado.

design criteria is consistent with the design basis characteristi Table 2-1 of NUREG-1503 establishes The revised by the staff in NUREG-1503. design-basis tornado characteristics licensee's proposed revision is consistent with that table.

In NUREG-1503, the staff refers to SECY-93-087, "Reactor Policy, Techn id Light-Wat Licensing Issues Pertaining to Evolutionary and Advanced (ALWR) speeds.

Designs," dated April 2, 1993, as ahasbasis f d data which positions in RG 1.76 using the considerable quantityis of This reevaluation torna o discussed become available since RG 1.76 l was developed.y of the Contiguous United St in NUREG/CR-4661, " Tornado Climato og May 1986.

Based on the updated tornado data and the analysis provide NUREG/CR-4661, the staff concluded (SECY-93-087) hour (Km/hr)that it is for reduce the tornado design basis wind speeds h is t states east of the Rocky Moun;ains. licensee's i proposed.

The ih reduc acceptable for WNP-2 which is located west of the ATTACHMENT 1

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the 200 mph tornado are also acceptable because they are consistent with t design-basis tornado characteristics found acceptable to the staff in Table 2-1 of NUREG-1503.

The licensee has also proposed The a new (new to WNP-licensee has used i velocities based on the reduced wind speed of 200 mph.

j Missile (SRP).

Spectrum II identified in Section 3.5.1.4 of the S the SRP, the staff concludes that it is acceptable.

' It should also be recognized that the tornado design basis requirements have l been used in establishing structural requirements (minimum concrete wall thicknesses) for the protection of safety related structures, systems, and 1

l components against effects Specifically, not covered some explicitly aviation in review guidance such (general l RGs or the Standard Review Plan. i missiles have been reviewed and evaluated routinely b i

Therefore, j

into account the existence of the tornado protection requi criteria, the licensee should perform an analysis under 10 CFR Part 50.59, to verify that the structures are adequate (minimum wall thickness) to protect i

against other postulated site-specific hazards or loads that may have been  :

l 4 previously subsumed within the tornado design basis.

3.0 CONCLUSION

1 Based on the above evaluation, the staff concludes that the licensee'sbas l proposed revised criteria for the dag.7 the guidelines of RG 1.76 regardit.) ?t2 missile spectrum The and with the l '

revised design-basis tornado characteristics set forth l

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J NOTE TO: Ashok Thadani, ADT/NRR 1

i THRU: Gus C. Lainas, DE/NRR 5 FROM: Jos6 Calvo EELB/DE/NRR f7(C i

SUBJECT:

TRANSFORMER FAILURES f

By a note dated February 6, 1996, you requested DE to investigate and report back findings /reconsnendations on transformer failures.

The Electrical Engineering Branch (EELB) has searched for events from 1980 through 1995 involving transformer failures through NUDOCS, LERs, preliminary notices, morning reports, event notifications, circulars, bulletins and Information Notices. The events are associated with all types of transformers including high-volta 9e (main, unit auxiliary and start-up) and low-voltage  ;

transformers. In addition, we investigated other information including NSAC-182 (March 1992), " Losses of Offsite Power in Nuclear Power Generating Stations," NUREG-1299 (March 1991), " Review of Licensee's Renewal, Nuclear Plant Aging Research (NPAR)," and NUREG-09331ssue 107, " Main Transformer Failures." A Table of Events is attached.

The following is the summary by year of the number of transformer failures and consequential reactor trips.

TRANSFORMER Fall 0RES REACTOR TRIPS MILS 3 2 1996 thru 3/1/96 3 1995 5 1 1 1994 1 1 1993 3 1992 5 8 5 1991 0 1990 0 1 1 1989 4 1988 4 1

1987 2 1

1 1986 0 1985 0 1

1 1984 0 1

1983 0 1

1980 CONTACT: Narinder Trehan, EELB/NRR 415-2777 I

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The following findings were made regarding the transformer related events:

1. In the last 5 months there have been 6 events involving loss of high voltage transformers. (Note: The recent Catawba and Calvert Cliffs events were included in the attached table for information only, however, they did not involve transformer failures and were not counted in the above summary.)

2. In NUREG-1299, " Review of Licensee's Renewal, Nuclear Plant Aging G I' d Research (NPAR)," NPRDS showed that 13 percent of the transformer )';

• failures were age-related. y. -

3. Transformer failure rates may not be changing when considering events back into the 80s.

With respect to recomendations there is a Generic Issue (GSI-107, " Main Transformer Failures") that was ranked LOW; however it was borderline to MEDIUM. It appears that it was ranked LOW because of the perceived potential benefits of the SB0 rule implementation. The prioritization was done around .

1990/91. We are currently responding to the RES request to review low- I priority generic safety issues. We will provide this information to RES for l potential repriortization of the issue.

Attachment:

Transformer Failures Table DISTRIBUTION EELB R/F BSheron

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TRANSFORMER FAILURES TABLE -

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i DATE PtANT Transformer DESCRIPTION l Fea/Rx Trip l 2/27/96 Calvert Cliffs 2 No/Yes Trip occurred while troubleshooting )

on one of 500 kV breakers in the switchyard was in progress causing loss of all four RCPs. The unit responded as designed except that one of rupture discs on the main turbine ruptured. This event did not involve transformer failure.

2/25/96 Psio Verde 1 Yes/No Lightning struck Phase C of the Main Power Transformer (MPT).

Flames were observed in the bushings and were self extingushed. Turbine tripped and reactor runback to 8%. Two holes were observed in the isophase bus duct.

Catawba 2 No/Rx T Ground on phases X & Z of the 22 2/6/96 kV isophase buses. Resister wall bushings for phases X & Z used to l l

connect protective relaying Potential Transformers to Isophase buses were damaged. This event did not l

involve transformer failure.

Perry 1 No/ Refuel Explosion in Start-up (SAT)

Outage transformer during refueling and 1]fel* 6 maintenance. Deluge protection operated.

Yes/ Refuel Loss of MPT oil cooling due to 2/4/96 LaSalle 1 Outage failure of cable feeding to cooling fans resulting in high oil temperature. A missing cap from conduit carrying cable was missing.

Water had frozen resulting in cable failure.

Yes/No One of two SATs as weil as high 1/18/96 Braidwood 2 voltage breaker damaged.

Yes/Ilx T A phase of main power transformer 12/18/95 South Texas 1 (MPT) had a ground fault.

Deblo Canyon 1 Yes/No During refuehng, an explosion and 10/21/95 fire occurred at UAT. A grounding i breaker was acculently left connected to bus causing a ground fault.

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I DATE PLANT Transformer DESCRIPTION Fes/Rx Trip 8/22/95 Cook 1 Yes/No Output bushing for Phase 2 on MPT f ailed. MPT has been installed to replace a previously damaged MPT and was being tested prior to service. A crack in the bushing was found and was replaced.

7/30/95 Grand Gulf Yes/Rx T MPT and main generator trip due to fadure of CT on A phase of generator output breaker CT replaced.

6/25/95 South Texas 2 No/Rx T MPT locked out due to pilot wire relay trouble (failure of capacitor) 6/18/95 Seabrook Yes/No 13.8 kV non safety transformer failed due to inadequate design 4/5/94 Braidwood 2 Yes/Rx T Reactor tnp due to a fault on 8 phase of MPT. Extensive damage Replaced with spare. Oil sample done every 6 months.

4/3/94 Zion 1 No/No Replaced MPT and replaced main i generator Isophase Bus duct fire.

6/13/93 Quad Cities 2 Yes/Rx T Internal arcing in MPT initialed l deluge system. Oil was black. MPT replaced.

9/22/92 Fitzpatrick No/No Load Center transformer ground fault. Loss of UPS.

7/4/92 Peach Bottom Yes/No 230 kV auto transformer failed due to arcing.

Zion Yes/Rx T Phase C of MPT, transformer failure 9/22/92 with oil fire Deluge system oper. l MFT significantly damaged, isophase bus was significantly damaged from explosion of MPT -

bus duct flash over, main gen Phase C bushings were damaged. MFT replaced.

4/24/92 San Onofre 2 Yes/No Failure of transformer 2813X.

Replaced.

Yes/Rx T Failure of MPT on 8 phase due to 1/9/92 Cienton intemel fault.

Vogtle ' Yes/Rx T Failure of MPT on 8 phase due to 1/4/92 intomal fault. MPT was found smoking heavily. Replaced.

Yes/Rx T Lightning struck on 8 phase of MPT.

6/16/91 Salem 1

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1 DATE PtAs. . Yransformer DeoCRIPTION Fe3/Rx Trip l

j: 4/29/91 Maine Yankee Yes/Rx T One of two MPTs had intomal fault -

j fault current caused arcing between i neutral bus & neutral bus enclosure

{ damaand neutral bushina - fire i

activated deluge system. MPT i replaced.

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! 3/20/91 Indian Point 2 Yes/No Loss of power to all 6.9 kV caused j by PT failure - 138 kV normal power j lost.

4 10/11/91 Peach Bottom Yes/No Failed static inverter transformer.

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I 8/13/91 Nine Mile Point 2 Yes/Rx T Reactor scram due to transformer j failure, and loss of UPS.

i 3/13/91 Vermont Yankee Yes/Rx T One phase of MPT failed due to j short.

2/15/91 Peach Bottom Yes/Rx T Failure of MFT due to fadure of cooling system which caused transformer overheat, causing sudden pres. trip. Deluge system did not activate. No cooling fans were available due to loss of power. MPT was found smoking. Deluge system was manually started.

8/28/91 Crystal River 3 Yes/No 480 V ESF transformer failed, replaced. )

6/25/89 Oyster Creek Yes/Rx T Fault in MPT spare installed.

12/26/88 Nine Mile Poirit 2 No/No Explosion of CT in offsite switchyard .

10/16/88 Braidwood 1 Yes/Rx T PT failure on 138 kV offsite line.

Reactor tripped on RCP low flow.

8/13/88 Maine Yankee Yes/Rx T Fault in MPT.

7/6/88 Palo Verde Yes/Rx T 138 kV UAT explosion and fire caused by brittle and cracked insulation.

3/29/88 Oconee 2 No/No SAT CT fault.

1/10/88 Grand Gulf 1 Yes/Rx T HV WDG. fault on MPT - MPT replaced.

7/20/87 Wolf Creek Yes/Rx T PT fadure caused pernal LOOP.

7/4/87 Palisades Yes/No Fault on SAT 12.

5/31/86 NA2 Yes/Rx T Fadure of 120 V Vital ac bus transformer, reactor tnoped.

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DATE PLAN Transformer DEdCRIPTION Fn2/Rx Trio  ;

12/2/85 Wolf Creek No/No Loss of ESF transformer due to PT failure.

6/20/83 Salem 2 No/No 460V transformer fault and fire due to failure of transformer neutral I wdg.

11/4/84 Duane Amold Yes/Rx T UAT fault caused by short in the HV wdg.

7/3/83 Three Mile Island 2 Yes/No Medium Voltage transformer failure I due to insulation failure.

1/17/80 Kewaunee Yes/No Reserve Aux. Transformer failed. ]

No cause given.

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October 7, 1996 l

PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-II-96-069 ,

.This preliminary notification constitutes EARLY notice of events of POSSIBLE l safety or.public interest significance. The information is as initially received without verification or evaluation, and is basically all that is known by Region II staff in Atlanta, Georgia on this date. )

1 Facility Licensee Emercency Classification Tennessee Valley Authority X Notification of Unusual Event sequoyah 1 2 Alert goddy-Daisy, Tennessee Site Area Emergency 1

dockets: 50-327,50-328 General Emergency Not Applicable Bubject: SEQUOYAH POTENTIAL TRANSFORMER EXPLOSION IN THE SWITCHYARD 3n October 5, 1996, at 1:13 p.m., a potential transformer (PT) in the 3equoyah 500 kv switchyard exploded, causing a loss of the switchyard Bus 1. Switchyard relays sensed the electrical fault as designed, and power circuit breakers opened to clear the differential fault. The units experienced various control board alarms but no plant equipment was effected. Both Sequoyah units continued to operate at full power. Oil from the faulted PT sprayed onto the gravel in the switchyard and ignited juring the event. The fire was extinguished in approximately.16 minutes.

there were no injuries. At 2:12 p.m., the licensee declared and exited pn Unusual Event due to an explosion within the protected area.

$n addition, shrapnel from the explosion damaged the 500 kv to 160 kv ,

%ntertie transformer, as well as other components in the switchyard such ins insulators.

l The licensee has developed plans for damage assessment, repairs,

$nvestigation, and root cause analysis. TVA has had some media interest

$n the evemt and will respond to further inquiries but does not plan a press release.

The NRC Senior Resident Inspector responded to the site to review limmediate licensee activities. Additional NRC review of the issue is bngoing.

The State of Tennessee was notified.

This information is current as of 9:00 a.m., on October 7, 1996.

d bontact: Mark S. Lesser (404)331-0342 a

a phj01j((4T961007 PNO-II-96-069 PDR ;p.

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