ML18101B231

LER 95-029-01:on 951219,all 4 Kv Vital Busses Declared Inoperable.Caused by Inadequate Initial Design of GE Type Sbm Switches by Mfg.Replaced All Suspect Switches in 4 Kv switchgear.W/960215 Ltr

ML18101B231
Person / Time
Site:	Salem
Issue date:	02/15/1996
From:	Hassler D, Warren C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-95-029, LER-95-29, LR-N96041, NUDOCS 9602220115
Download: ML18101B231 (6)

Text

OPS~G Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge. New Jersey 08038-0236 Nuclear Business Unit FEB 1 5 1996 LR-N96041 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Gentlemen:

LER 272/95-029-01 SALEM GENERATING STATION - UNIT 1

.FACILITY OPERATING LICENSE NO. DPR-70 DOCKET NO. 50-272 This Licensee Event Report entitled "GE SBM Control Switch Degradation" is being submitted pursuant to the requirements of t'.1.e Code of Federal Regulations 10CFR5 0. 73 (a) ( 2) (v) .

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General Manager -

Salem Operations A::tachment S:JRC Mtg.96-018 JSH/tcp C Distribution LER File 3.7 9602220115 960215 PDR ADOCK 05000272 S PDR 220(41 95-2168 REV. 6;94

• Attachment A The following items represent commitments that Public Service E=_ectric & Gas (PSE&G) made to the Nuclear Regulatory Commission (NRC) relative to this LER (272/95-029-01). The commitments are as follows:

1. All suspect SBM switches installed in 4 KV vital busses will be replaced with switches of an improved design prior to Mode 6 entry.

2. All suspect SBM switches installed in 4 KV group busses will be replaced with switches of an improved design prior to Mode 2 entry.

3. An overall review to determine whether SBM switches are used in other applications is being conducted, and any suspect switches identified will be changed out. The review portion will be completed by February 29, 1996.

NRCFORM366 (4-95)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

• APPROVED BY OMB NO. 3150-0104 EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS.

REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED BACK* TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (T-G F3~, U.S. NUCLEAR (See reverse for required number of REGULATORY COMMISSION, WASHINGTON, DC 20 55-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150--0104), OFFICE OF digits/characters for each block) MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAlllE (1) DOCKET NUllBER (2) PAGE (3)

SALEM GENERATING STATION - UNIT 1 05000272 1 OF4 TITLE (4)

GE SBM Control Switch Degradation EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR I SEQUENTIAL NUMBER IREVISION NUMBER MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 05000 12 19 95 95 - 029 - 01 02 15 96 FACILITY NAME DOCKET NUMBER 05000 OPERATING 6 THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more) (11)

MODE (9) 20.2201(b) 20.2203(a)(2)(v) 50. 73(a)(2)(i) 50. 73(a)(2)(viii)

POWER 0 20.2203(a)(1) 20.2203(a)(3)(i) 50. 73(a)(2)(ii) 50. 73(a)(2)(x)

LEVEL (10) 20.2203(a)(2)(i) 20.2203(a)(3)(ii) 50. 73(a)(2)(iii) 73.71 20.2203(a)(2)(ii) 20.2203(a)(4) 50.73(a)(2)(iv) OTHER 20.2203(a)(2)(iii) 50.36(c)(1) x 50. 73(a)(2)(v) Spec~in or in Abstract below C Form 366A 20.2203(a)(2)(iv) 50.36(c)(2) 50. 73(a)(2)(vii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Dennis v. Hassler, LERC Coordinator 609-339-1989 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS TO NPRDS

'YES SUPPLEMENTAL REPORT EXPECTED (14)

(If yes, complete EXPECTED SUBMISSION DATE).

I XINO EXPECTED SUBMISSION DATE (15)

MONTH DAY YEAR ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On December 19, 1995, all 4 KV vital buss es were declared inoperable per Technical Specifications at both Salem units 1 and 2 after an inspection of circuit breaker limit switches revealed cam follower cracking. No equipment malfunctions or plant transients occurred, because the single actual failure occurred during routine post modification testing. At the time of the discovery, both units were in an extended outage with all fuel removed from the reactor vessels; Technical Specification mode "undefined".

The root cause of this occurrence was inadequate ir.i ti al design of General Electric type SBM switches by the manufacturer. A contributing cause was a narrowly focused review of NRC IN 80-13. Corrective actions will include replacing all suspect switches in 4, KV switchgear, vital and group buss es and other plant applications.

This event is reportable in accordance with 10 CFR 50.73 (a) (2) (v) , any event or condition that alone could have prevented fulfillment of a safety function.

NRC FORM 366 (4-95)

NRC FORM 366A (4-95)

• LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

• U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) 05000272. YEAR I SEQUENTIAL NUMBER IREVISION NUMBER 2 OF 4 SALEM GENERATING STATION - UNIT 1 95 -- 029 - 01 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

PLANT AND SYSTEM IDENTIFICATION Westinghouse - Pressurized Water Reactor Emergency Onsite Power Supply System {EK/-}*

• Energy Industry Identification System (EIIS) codes and component function identifier codes appear in the text as {SS/CC}

IDENTIFICATION OF OCCURRENCE Discovery Date: December 19, 1995 CONDITIONS PRIOR TO OCCURRENCE The plants were defueled at the time of discovery.

There were no structures, components, or systems that were inoperable at the start of each event that contributed to the event.

DESCRIPTION OF OCCURRENCE During the current Unit 1 outage, a design change for the replacement of 52HL high limit switch (General Electric type SBM) mechanical linkages on 4KV vital bus breakers was implemented. During post modification testing, an electrical failure of the lA vital bus high limit switch occurred. The defective switch was replaced, and an investigation was initiated to determine the cause of the failure. Subsequent intrusive, visual inspection of the disassembled switch revealed subsurface cracking on the polycarbonate contact support armature, labeled as the cam follower by the manufacturer.

To determine whether a generic issue might be involved, and to define the possible extent of the problem, two additional steps were taken. First, an Operating Experience search was conducted. Second, additional 52HL limit switches installed on 4KV vital bus breakers were inspected. Cracks similar in appearance were observed on some switches, both at Salem and at other facilities, and as a result all 4KV vital busses were declared inoperable at both Salem Units 1 and 2 on December 19, 1995.

NRC FORM 366A (4-95)

NRC FORM 366A (4-95)

• LICENSEE EVENT REPORT (LER)

• U.S. NUCLEAR REGULATORY COMMISSION TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) 05000272 YEAR I SEQUENTIAL NUMBER IREVISION NUMBER 3 OF 4 1

SALEM GENE.£\_:- '.'ING STATION - UNIT 1 95 - 02 9 - 01 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

CAUSE OF OCCURRENCE The root cause of this occurrence was inadequate initial design of General Electric type SBM switches by the manufacturer. A contributing cause was a narrowly focused review of NRC IN 80-13. The original General Electric SBM switches used were commercially supplied and dedicated. The current Operational Experience Feedback Program reviews items marked either for BWR or PWR. However, the Operating Experience Feedback Program in place at Salem during the early 1980's did not review the operating experience being generated for General Electric SBM switch failures because they were written specifically for BWRs. The then existing program did not require that applicability to PWRs be considered. In 1989, NRC IN 80-13 entitled General Electric Type SBM Control Switches Defective Cam Followers was reviewed. The review focused on ensuring that hydrocarbon cleaners had not been used (which had been identified as a potential cause of cracking), but did not consider that other cracking mechanisms might exist.

PRIOR SIMILAR OCCURRENCES A review of LERs for Salem Units 1 & 2 did not identify any prior occurrences within the last two years.

SAFETY SIGNIFICANCE Although the safety significance of a single switch failure is low, the cracking was found to be generic. The switches found with cracks remained functional. There have not been any cam follower failures at Salem prior to the one experienced, and General Electric failure data published with the original General Electric Service Information Letter estimated failure I rates ~t that time to be less than .03 % of switctes installed. A review lof operating experience at other plants did not reveal any instances of lsBM switch failure due to cracking. A review of the subject cam followers by Seismic Engineers concluded that due to the relatively low mass of the contact assembly, as compared to the cam follower itself, seismic forces would not be expected to further propagate pre-exi~ting cracks. SBM switches now in use are subjected to more comprehe~sive testing including accelerated aging. Based on the above, the health and safety of the public were not affected.

NRC FORM 366A (4-95)

NRC FORM 366A (4-95)

• LICENSEE EVENT REPORT (LER)

• U.S. NUCLEAR REGULATORY COMMISSION TEXT CONTINUATION it---------F_A_C_ILITY NAME (1) DOCKET NUMBER (2) LER NUiollBER (6) PAGE (3) 05000272 YEAR I SEQUENTIAL NUMBER IREVISION NUMBER 4 OF 4 SPJ1EM GENERATING STATION - UNIT 1 95 - 02 9 - 01 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

CORRECTIVE ACTIONS

1. All SBM 'switches installed in 4 KV vital busses will be replaced with switches of an improved design prior to Mode 6 entry.

2. All SBM switches installed in 4 KV group busses will be replaced with switches of an improved design prior to Mode 2 entry.

3. An overall review to determine whether SBM switches are used in other applications is being conducted, and any suspect switches identified will be changed out. The review portion will be completed by February 29, 1996.

All switches identified under this review that are installed on a vital bus will be changed out prior to Mode 6 entry. All switches identified under this review that are installed on a group bus will be changed out prior to Mode 2 entry.

NRC FORM 366A (4-95)