ML20128Q243

Discusses Concerns Raised During 960722 AEOD Program Review Re Reportability of Reactor Trip Breaker Problems at Plants

ML20128Q243
Person / Time
Site:	Catawba, McGuire, Mcguire
Issue date:	08/01/1996
From:	Jordan E NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:	Ebneter S, Lieberman J, Russell W NRC (Affiliation Not Assigned), NRC OFFICE OF ENFORCEMENT (OE), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20128Q247	List: ML20128Q243 ML20129H740
References
NUDOCS 9608050142
Download: ML20128Q243 (5)

Text

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J'patcy"'o, y- . UNITED STATES l

j .. 'L/ j NUCLEAR REGULATORY COMMISSION l

$. 'C WASHINGTON, D.C. 20555-0001 )

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l l l August 1, 1996 i

l MEMORANDUM T0: Stewart D. Ebneter l Regional Administrator, Region II l

l William T. Russell, Director l l Office of Nuclear Reactor Regulation 1 James Lieberman, Director OfficejfsEnforcement FROM: 4dwa Lb n7 Director Office' or Analysis and Evaluation of Operational Data

SUBJECT:

REPORTABILITT OF REACTOR TRIP BREAKER I PROBLEMS AT MCGUIRE AND CATAWBA l I have recently become sensitized to recent instances of reactor licensees l failing to report non-emergency events, conditions, or defects and of numerous

" retractions" of reports via " loopholes."

l l

I discussed my concerns during the AE00 program review on July 22, 1996.

Absent plant specific correction, an error becomes that licensee's practice.

Generically, an NRC failure to revise guidance or requirements where different l interpretations are reasonable leads to continued failure to report and hence, i lost opportunities for corporate learning. I do not advocate getting tangled I in esoterics of reporting, but I plan to illuminate each flagrant instance for l appropriate action and followup.

On June 12, 1996, McGuire Unit 2 experienced a failure of the shunt trip function in a bypass RTB. The failure occurred during surveillance testing while the plant was shutdown. It was attributed to breakage / cracking of phenolic material in secondary contact disconnect assemblies. (Apparently a piece of the phenolic material fell into a specific contact and blocked its l

operation.)

! Similar breakage / cracking of the phenolic material in secondary contact disconnect assemblies was then found in many other RTBs and/or RTB bypass breakers at McGuire and Catawba. One RTB at McGuire Unit 2 was on the verge of failure. (Apparently this breaker tripped on test because it was being held together by the breaker cubicle; however, the phenolic disconnect assembly essentially fell apart when the breaker was racked out for inspection, which was the last step of the test.) Additional details are provided in a draft Information Notice that R- II provided to NRR and AE00 on July 12, 1996 (see Attachment 1).

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t S. Ebneter, et. al. On June 26, 1996, the licensee provided an ENS notification and submitted a special report oncerning the initial failure at McGuire Unit 2. The ENS report was then -etracted on July 1, 1996 (see Attachments 2 and 3). The retraction was i de by the licensee on the grounds that the general Salem ATWS requirements hau aeen removed from the McGuire Unit 2 technical specifications (TS) and no specific reporting requirement is contained in the license.

However, we understand from discussions with the McGuire Licensing Project Manager that a related reporting requirement was included in the McGuire Unit 2 license as part of the TS change.

Isolated or random RTB failures are not specifically reportable' under 10 CFR l 50.72 and 50.73. This example at McGuire is not isolated or random and it is l important that RTB failures continue to be reported under license conditions or (TS) as highlighted by the McGuire event to assure that generic i implications are identified as early as possible, j l

We understand that McGuire Unit 2 has a license condition requiring that the l licensee preserve the evidence and report the failure of any RTB or RTB bypass

! inservice or in testing (on either the undervoltage coil or the shunt coil).

I This is what would be expected as a result of followup actions taken in response to the Salem ATWS event in 1983. However, McGuire Unit I does not have a similar license condition, which raises a question as to other plants. 1 To ensure that RTB failures are reported in the future, I recommend that it be ,

l confirmed that license conditions continue to require reporting of RTB failures, particularly when and if the TS are modified to remove such l requirements from the TS. An alternative is to invoke reporting criteria of Part 21 regarding a defect in a basic component that could create a  ;

! substantial safety hazard. Another alternative is for AE0D to revise 50.72, 50.73, and NUREG-1022 to clearly include single RTB breaker failures or to i assure that such failures are captured in the reliability data rule. Please l l

advise by August 30, 1996 of your plans or recommendations (specific to McGuire and generic).

If you or your staff have any questions on this subject, please contact me at 415-7472 or Dennis Allison of my staff at 415-6835.

l Attachments: As stated l

l cc: J. Taylor, ED0 A. Beach, Rill

! J. Milhoan, ED0 L. Callan, RIV H. Miller, RI

' It can be argued that the initial failure et McGuire Unit 2, which is associated with broken and cracked phenolic disconnect I assemblies in many other breakers, one of which was on the vorge of failure, is reportable under 10 CFR 50.72(b)(2Hiii) and 50.73(a)(2)(v),

• Event oi Condition that Alone Could Prevent... " A senifer example, copied from previous guidance, is Example 8, page 72, NuREG-1022, flev.1, Second draft. That example involves a pinnp bearing seizure due to improper lubrication. The redundant pump was also lubricated 'rnproperty (i.e., in the same condition). To apply this reporting criterion, there should generally be a reasonable expectation of preventing fulfihent of the safety function.

l l

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l UNITED STATES I

NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 July ??, 1996 NRC INFORMATION NOTICE 96-??: P0TENTIAL FAILURE OF REACTOR TRIP BREAKER SECONDARY CONTACT DISCONNECT ASSEMBLY DUE TO CRACKING 0F PHEN 0LIC MATERIAL Addressees l

All holders of operating licenses or construction permits for nuclear power reactors.

Purpose l The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice l to alert addressees to the possible failure of reactor trip breakers to properly function due to cracking or breakage of the secondary contact disconnect l assemblies. The disconnect assemblies are made from a phenolic material and I

provide circuit connections between the control and monitoring devices on the breaker and external control circuits. Breakage or partial cracking of these assemblies may prevent the breaker from performing its design function or other l secondary functions provided by the breaker position status. It is expected that recipients will review this information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice are not NRC requirements; therefore, no specific action or written response is required.

Description of Circumstances t

l On June 12, 1996, during reactor trip breaker (RTB) testing at McGuire Unit 2, l a Westinghouse Pressurized Water Reactor (PWR), the licensee (Duke Power Company) identified that one of the bypass RTBs failed to open electrically when the local shunt trip push button was depressed. The breaker was later verified to open mechanically. The McGuire Unit 1 and Unit 2 RTBs and bypass RTBs are i Westinghouse model DS-416 equipped with four secondary contact disconnect I assemblies, each containing eight spring loaded contacts, mounted on the upper rear portion of the breaker. The shunt trip, undervoltage trip and open/ closed monitoring circuits for the breakers are wired through these assemblies. During subsequent inspection of _the RTB, a small piece of the assembly was found. The licensee postulated that the fragment may have lodged in the secondary contact disconnect assembly, preventing good electrical connection for the local shunt trip pushbutton circuit. The assemblies are made of a molded, cellulose-filled, phenolic material that appears to have low impact strength and may be highly

, susceptible to chipping or cracking. McGuire Unit 2 was in cold shutdown (MODE

5) at the time of discovery. The postulated root cause of the chipped assembly was determined to be mechanical damage during maintenance or initial installation.

4

On July 1, 1996, while performing extent of condition inspections of the remaining Unit 1 and Unit 2 RTBs, the licensee discovered that an entire l

. secondary contact disconnect assembly on a Unit 1 RTB was broken in half and one of the spring loaded finger contacts had fallen out in the breaker cubicle during the breaker inspection. Unit I was operating at 100% at the time of discovery.

The licensee inspected the internals of the breaker cubical for damage. No damage to the cubicle was identified. The licensee replaced the failed breaker with an available bypass RTB. Required retesting of the replacement breaker was completed and the RTB was placed in service. The postulated root cause of the cracked assembly was determined to be stress induced from over- torquing of the block to breaker mounting bolts during replacement of the assembly in September 1994.

Based on the situation identified at McGuire, the licensee performed additional inspections of RTB assemblies at Catawba. Evidence of RTB secondary contact disconnect assembly cracking was also discovered.

Discussion In 1993, Westinghouse issued a revised technical manual for a variety of breakers including the DS-416 model. The revised manual specified a torque value for the secondary contact disconnect assemblies to breaker mounting bolts. Licensee's should review the maintenance history of applicable breakers to determine if inappropriate torque values have been used during replacement or initial installation of the subject secondary contact disconnect assemblies. In addition, inspection of the disconnect assemblies may be warranted to determine if any other cracking problem exists.

Information Notice (IN 95-19), Failure of Reactor Trip Breaker to Open Because of Cutoff Switch Material Lodged in the Trip Latch Mechanism, was issued on March 22, 1995, to alert licensee's of a related problem involving breakage of phenolic material in RTB subcomponents.

The majority of the reactor trip breaker failures at power reactors have been caused by problems with relatively small electrical subcomponents in the breaker assembly, rather than the malfunction of the main breaker mechanism itself. The failures identified at McGuire and Catawba involving cracking of breaker phenolic material may represent a generic concern of the subcomponent structural integrity of reactor trip and other important breakers. Proper care of these components during routine and corrective maintenance could prevent similar problems at other i facilities.

This information notit.e requires no specific action or written response. If you have any questions about the information in this notice, please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

l Brian K. Grimes, Director Division of Project Support Office of Nuclear Reactor Regulation Technical contacts: S. Shaeffer, Region II M. Sykes, Region II (704) 875-1681 (704) 875-1681

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, 7:F. SITE NRC PERSONNEL WERE NOTIFIED ON 06/I3/96. THIS NOTIFICATICN {

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THE :?CENSEE IS RETRACTING THIS EVENT BECAUSE THE LICENSE CONDITION TO l

! REPORT ANY FAILURES ASSOCIATED WITH REACTOR TRIP BYPASS BREAKERS IS NO

! LONGER PART OF TF' LICENSEE'S LICENSE OR TECHNICAL SPECIFICATIONS.

THE L:CENSEE NTIFIED THE NRC RESIDENT INSPECTOR AND PLANS TO SUBMIT is RET 4ACT:DN CF A WRITTEN FOLLOWUP NOTIFICATION AN ABSTRACT OF A SPECIA*.

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DUKE POWER DATE: June 26, 1996 l

U.S. Nuclear Regulatory Commission  ;

l Document Control Desk i Washington, D.C. 20555

Subject:

McGuire Nuclear Station Unit 2 i Special Report 96-03 Problem Investigation Process No.: 2-M96-1690 l

Gentlemen: I 1

Pursuant to McGuire Nuclear Station (License Condition 2.C(12 C attachJd is (Special Report 96-03)concerning Failure Of Reactor Trip Bypass l Breaker 2A Due To An Unknown, Possible Material Deficiency. This event ,

is considered to be of no significance with respect to the health and I safety of the public.

1 Very truly jours, j l

cb Mu

.C. McMeekin JWP/bcb h

Attachment l l

cc: Mr. S.D. Ebneter INPO Records Center Administrator, Region II Suite 1500 ,

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U.S. Nuclear Regulatory Commission 1100 Circle 75 Parkway 101 Marietta St., NW, Suite 2900 Atlanta, GA 30339 Atlanta, GA 30323 Mr. Victor Nerses Mr. George Maxwell U.S. Nuclear Regulatory Commission NRC Resident Inspector Office of Nuclear Reactor Regulation McGuire Nuclear Station Washington, D.C. 20555 4

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96G7030084760626 1

PDR ADOCK 05000370 S PDR I

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. bxc D. L. Wnish (EC11C) '

, Z. L. Taylor (CNS)

!, G . 1A . Copp (EC050)

J. I. Glenn (MG02ME)

P. R. Herran (MG0lVP)

C. B. Davis (MG01CP) l l J. E. Burchfield (ONS Reg Compliance)

G. H. Savage (EC06E) ,

i G. B. Swindlehurst (EC11-0842)

• l C. M. Misenheimer (EC08I)

R. F. Cole (EC05N)

J. M. Frye (EC05N) l T. G. Becker (PB02L)

P. M. Abraham (EC08I)

R. B. White (MG01VP)

L. V. Wilkie (ONO3SR)

D. P. Kimball (CN05SR)

K. L. Crane (MG01RC)

R. N. Casler (EC05N)

NSRB Support Staff (EC05N) i i

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, 1 NAC F OEW)66 U S NUCLE AP RE GULATORY CouMf SS'ON

• AFMOVED EY ose. NO 3%0104 EAPIRES IWJets

• E ST' MATE D BUADEN PE R RE SPONSE 6TO COMP V WITH THIS WANDA'Opv iN50evAfiON COLLECTION REOUEST 60 0 HR$

Sif PORYED LE SSONS LE ARNED AFiE INCORPORATED INTO THE LICENSEE EVENT REPORT (LER) uCENS No aaOctSS AND FED SAC ToiNDUSTRv FOa*Aa0 CouMENTS AEGAADtNG 8uRDEN E STIMATE TO THE INFORMATiON AND PECOAC5 vaNAGEMENT 8AANCHIT-6 F331 U S NUCLE AR AEGULa f 0A. COvv'SS80% W ASHINGTON DC201554001 AND TO THE P APE ACA* NE DUCTION PROJECT (3160 ci",si Of FICE OF WANAGEVE NT aND BODGE Y WASH'NGTON DC 20503 F ACILITY NAME (1) DW E T NUVBER .2) PAGEf33 McGuire Nuclear Station. Umt 2 05000370 10F 1 TITLE (4)

Fadure Of Reactor Trip Bypass Breaker 2A Due To An Unknown, Possible Material Deficiency EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) l wa n. one OTHER FACILITIES INVOLVED (8) t es as es as se xt =w an s.m wmm oar vtam sacv'v =auf DOCKET NUM8ER($1

= ween asuussa l N/A 05000 I . .

t l 06 12 96 N/A N/A N/A 06 26 96 05000 OPERATING THIS AEPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CI'A (CAcca one or me,c of the followin(7)(11 l MODE (9) 5 20 402:bt 20 405(c) 50 73:aH23ovt 73 7f(b)

POWER 20 405(a 41)(4 50 36(c)(1) 50 73ian2;iv) 73 71(c)

LEVEL (10) 0 *. 20 405 aHijo.) 50 36(c)(2) 50 73 rail 2nww x OTHER (Speedyin p'" 42 T 20 405< au t Hml 50 73(a)(210) 50 73(an2nvmW Ai Abstract Desow and 20 400an is0vi 50 73(aK2)h) 50 73;an2iivumBi in Terf NRC Form u  ?- 20 4354a u_1 wvi 50 73<ait2)(m) 50 73 anPai 366A)

LICENSEE CONTACT FOR THIS LE A 812' i- NAME i TELEPHONE NUMBE A l AAE A CODE l '

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-J. W. Pitesa l (704) 875 4768 COMPLETE ONE LINE FOR E ACH COMPONENT F AILUAE DESCAIBED IN THIS AEPOAT 8131 CAUSE Sv5ffu COMPONE NT MANUFACTURER REPORTABLE W CAUSE SYSTEM COMPONENT MANUFACTUAER REPORTABLE

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ABK CKTBAk W120 YES t>

SUPPLEMENTAL REPOAT EXPECTED it4) EXPECTED MONTH DAY YEAR SUBMISSION x YE S rY ves conwere frPECTFD SUButSSf0N DA7El NO DATEtt5) C7 26 96 4 85 TRACT (tirrut so f 400 spaces r e approrernare<y f,treen sengee-space rmewntren I, nest (16)

Unit Status: Unit 2 was in Mode 5, Cold Shutdown, at 0 percent Reactor power.

($pecial Report 96-0 Dis being submitted in accordance with McGuire Nuclear 5t::. tion , un3.t 2, (Uicense Condition 2.C(12)D Evcnt

Description:

During tne Unit 2 Train A SSPS Monthly Test on June 12, 1996, it was discovered that Unit 2 Bypass Reactor Trip Breaker BYA would not open electrically in the test position. The breaker failed to open on several attempts.

Evcnt Cause A cause of Unknown, Possible Material Deficiency has been

assigned. Investigation revealed that a piece of the block for the Breaker l Secondary Contact Assembly was chipped off. It was also noted that contact 4 l (unrelated to the Shunt Trip Circuitry in question) was deformed / bent in such a manner that the position of the contact was higher than the other contacts in the assembly.

Corrective Action: The chipped block was replaced with a new block assembly from the warehouse. In addition, the shunt trip ceil was replaced as a conservative measure. The breaker was re-tested and placed back in service.

Inspections were performed on 6 of the 7 remaining reactor trip breakers on  !

both units, looking for chipped blocks as well as deformed' bent contacts. I

'The remaining breaker is scheduled to be inspected in early July, 1996. A i thorough cause investigation will be completed by Ju;y 26. 1996.  !

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