ML18101B186

LER 95-029-00:on 951219,4 Kv Vital Buses Declared Inoperable.Caused by Inadequate Initial Design of GE Type Sbm Switches by Mfg.All Suspect Switches in 4 Kv Switchgear, Vital & Group Busses Replaced

ML18101B186
Person / Time
Site:	Salem
Issue date:	01/18/1996
From:	MORTARULO M Public Service Enterprise Group
To:
Shared Package
ML18101B185	List: ML18101B184 ML18101B186
References
LER-95-029-01, LER-95-29-1, NUDOCS 9601230102
Download: ML18101B186 (4)

Text

.> I NRCFORM388 U.S. NUCLf:AR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-01<M (4-96) EXPIRES 04/30198 ESTIMATED BURDEN PER RESPONSE TO COMPLY . WITH THIS MANDATOR\'

INFORMATION COLLECTION REQUEST: llO.O HRS. LICENSEE EVENT REPORT (LER) REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION (See reverse for required number of AND RECORDS MANAGEMENT BRANCH REGULATOR\'

DC , AND TO digits/characters for each block) THE PAPERWORK REDU PROJECT OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, 20503. FACILITY NAllE (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 (8) REPORT DATE (7) OTHER FACILITIES INVOLVED (8) YEAR I FACILITY NAME DOCKET NUMBER MONTH DAY YEAR SEQUENTIAL I REVISION MONTH DAY YEAR NUMBER NUMBER 05000 12 19 95 95 029 00 01 18 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) 50.38(c)(1) x 50.73(a)(2)(v) Abetractbelow Of' C Form 386A 20.2203(a)(2)(iv) 50.36(c)(2) 50.73(a)(2)(vii)

LICENSEE CONTACT FOR THIS LER (12) NAME TELEPHONE NUMBER (Include ArH Code) Mike Mortarulo, Electrical/I&C Systems Supervisor 609-339-2741 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE 1:i1,11111111111 CAUSE SYSTEM COMPONENT llANUFACTURER REPORTABLE TONPRDS TONPRDS :::::::::.::::::::::::::::::::

B EB SWGR G082 y I

-:-:*:*:*:*:*:*:-:-:-:-:-:-:

SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR IYES INO SUBMISSION X (If yea, complete EXPECTED SUBMISSION DATE). DATE (15) 02 16 96 ABSTRACT (Limit to 1400 spaces, I.e., approximately 15 single-spaced typewritten iinea) (18) 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 initial design of General Electric type SBM switche's 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 swi tchgea*r, vital and group buss es and other plant applications.

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

9601230102 960117 PDR ADOCK 05000272 NRC FORM 366 (4-95) s PDR

.* -NRC FORM 366A (4-95) U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER (2) LER NUMBER (6) 05000272 YEAR I SEQUENTIAL I REVISION NUMBER NUMBER SALEM GENERATING STATION -UNIT 1 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/-}* 95 -029 -00 PAGE (3) 2 OF 4 *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, lqpeled 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 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) U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER (2) LER NUMBER (6) 05000272 YEAR I SEQUENTIAL I REVISION NUMBER NUMBER SALEM GENERATTNG STATION -UNIT 1 qc:; -029 -00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) CAUSE OF OCCURRENCE PAGE (3) 3 OF 4 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 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 rates at that time to be less than .03 % of switches installed.

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-existing cracks. SBM switches now in use are subjected to more comprehensive 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) U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER (2) LER NUMBER (6) 05000272 YEAR I SEQUENTl;.L I REVISION NUMBER NUMBER SALEM GENERATING STATION -UNIT 1 95 -029 -00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) CORRECTIVE ACTIONS PAGE (3) 4 OF 4 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. Ah 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)