ML18102A230

LER 96-009-00:on 960530,concluded Potential Common Mode Failure for 4 Kv Magne-Blast Breakers.Caused by Misalignment of Breaker Mechanism & Internals.Assessed Breaker Mechanism Misalignment for Each breaker.W/960701 Ltr

ML18102A230
Person / Time
Site:	Salem
Issue date:	07/01/1996
From:	Garchow D, Hassler D Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-96-009-01, LER-96-9-1, LR-N96184, NUDOCS 9607080199
Download: ML18102A230 (6)

Text

OPS~G

• Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038-0236 Nuclear Business Unit JUL 011996 LR-N96184 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Gentlemen:

LER 272/96-009-00 SALEM GENERATING STATION - UNIT 1 FACILITY OPERATING LICENSE NO. DPR-70 DOCKET NO. 50-272 This Licensee Event Report entitled "Potential Common Mode Failure for 4KV Magne-Blast Breakres" is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR50. 73 (a) (2) (i) (B).

Sincerely,

\)cwJ) (-_ 910JL~~,1J David F. Garchow General Manager -

Salem Operations Attachment SORC Mtg. 96-0 DVH/tcp C Distribution LER File 3.7 9607080199 960701 PDR ADOCK 05000272 8 PDR 1l1c power is in \Our hand..'

95-2168 REV. 6/94

Document Control Desk LR-N96184 Attachment A The following item represents the commitments that Public Service Electric

& Gas (PSE&G) made to the Nuclear Regulatory Commission (NRC) relative to this LER (272/96-009-00). The commitments are as follows:

For Salem Unit 2 Corrective Actions 1 - 4 will be completed for each breaker prior to that breaker being required to be operable.

1. Breaker mechanism misalignment will be assessed for each breaker.

2. A high speed video camera will be used to determine that the breaker adjustments are satisfactory. The breakers will not be returned to operable status without GE concurrence that the adjustment program and methodology is satisfactory.

3. Procedure changes that incorporate the video acceptance criteria and short term mechanical acceptance criteria will be implemented.

4. The breaker contact velocity will be verified to meet the vendor specifications for opening and closing.

5. An INPO Network TI item was issued on March 15, 1996 and an INPO Network OE notification was issued on May 13, 1996.

6. For Salem Unit 1, the corrective action may be replacement of the breakers, implementation of a modification to resolve the problem, or implementation of Corrective Actions 1 - 4. The selected corrective action will be implemented for each breaker prior to that breaker being required to be operable.

NRCFORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (4-95) EXPIRES 04130198

-. ESTIMATED BURDEN PER RESPONSE TO COMPLY WTTH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS.

REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE LICENSEE EVENT REPORT (LER) LICENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (T~ ~~NUCLEAR (See reverse for required number of REGULATORY COMMISSION, WASHINGTON, DC , AND TO THE PAPERWORK REDUCTION PROJECT (3150-4104), OFFICE OF digits/characters for each block) MANAGEMENT AND BUDGET, WASHINGTON, DC 20603.

FACILITY NAME (1) DOCKET NUMBER (2) PAGE(3)

Salem Generating Station, Unit 1 05000272 1 OF 4 TITLE (4)

Potential Common Mode Failure for 4KV Magne-Blast Breakers EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR I SEQUENTIAL NUMBER

'REVISION NUMBER MONTH DAY YEAR FACILITY NAME Salem, Unit 2 DOCKET NUMBER 05000311 05 30 96 96 - 009 - 00 07 01 96 FACILITY NAME DOCKET NUMBER 05000 OPERATING N 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) S~~ln 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 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 TONPRDS TONPROS I

B EB BKR G080 y SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR SUBMISSION

'YES (If yes, complete EXPECTED SUBMISSION DATE). XINO DATE (15)

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

On May 30, 1996 a root cause investigation concluded that the General Electric (GE) Magne-Blast 4 KV breakers have a potential common mode failure mechanism which could jeopardize their fast closure capability. A total of five GE Magne-Blast breakers on 4 KV power systems failed during the period of January - March 1996. Four of the five breakers had been refurbished or overhauled by the vendor within the previous 18 months. I The failures occurred during the first load energization in the breaker cubicle, or during cycling in the "test" position in the cubicle, or when shop tested in the Maintenance Controls Breaker Shop. A misalignment of the breaker mechanism and internals developed over the years of operation. This misalignment created unequal forces during closure and caused the latching mechanism prop to impact the prop pin causing it to bounce out of position.

This event is reportable in accordance with 10 CFR 73(a) (2) (v); any event or condition that alone could have prevented the fulfillment of the safety function of systems that are needed to shutdown the reactor and maintain it in a safe shutdown condition and mitigate the consequences of an accident.

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 SE,fill,i~:fL I':m"~~ 2 OF 4 Salem Generating Station, Unit 1 96 - 009 - 00 TEXT (If more space is required, uae additional copies of NRC Form 366A) (17)

PLANT AND SYSTEM IDENTIFICATION Westinghouse - Pressurized Water Reactor 4KV Breakers {-/BKR}*

• Energy Industry Identification system (EIIS) codes and component function identifier codes appear as (SS/CCC)

CONDITIONS PRIOR TO OCCURRENCE At the time of identification, Salem Units 1 and 2 were shutdown and defueled.

DESCRIPTION OF OCCURRENCE On May 30, 1996 a root cause investigation of General Electric (GE) Magne-Blast 4 KV breakers concluded that a potential common mode failure mechanism exists, which could jeopardize the fast reliable closure capability of safety related circuit breakers. A total of five GE Magne-Blast breakers on 4 KV power systems failed during the period of January - March 1996. Four of the five breakers had been refurbished or overhauled by the vendor within the previous 18 months.

The failures occurred during the first load energization in the breaker cubicle, or during cycling in the "test" position in the cubicle, or when shbp tested in the Maintenance Controls Breaker Shop. The failure mode was repeatable in some instances. The breakers tripped to a non-latched (open) position with the closing springs charged for another operation. The trips did not result in any relay flag/target drops or annunciation indicating electrical protective circuit actuation. For the breakers that were tested in their cubicle, the close signal was initiated from the control room bezel push-button.

The Magne-Blast breakers are 1200 and 2000 amp frame size, high momentary and 4000 volt rating. The breakers are pre-1985 design vintage and were manufactured by GE. The breakers are vertically mounted in the cubicle. The operating mechanism for the breakers is attached to the front of the breaker frame and includes two closing springs and one opening spring for the 1200 amp size, and two closing springs and two opening springs for the 2000 amp frame size breakers.

When a breaker is installed into a cubicle and its 125 VDC control power is energized, the closing springs are charged by the charging motor and the closing mechanism moves to the reset position. When a closing demand is provided, the closing mechanism rolls forward as the closing springs are discharged with the prop sliding under the pin (prop pin) which is mounted to the linkage arms of the closing latch. As the pin reaches its maximun height (maximum gap), the prop falls into position under the pin assisted by the tension in the prop NRC FORM 366A (4-95)

.. I (4-95)

NRC FORM 366A LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

• U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1)

Salem Generating Station, Unit 1 DOCKET NUMBER (2) 05000272 YEAR 96 -

LER NUMBER (6)

I SE.fillri:J~AL I 009

==

00 3

PAGE (3)

OF 4 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

DESCRIPTION OF OCCURRENCE (cont'd) springs. Then the pin drops down on top of the prop to complete the latching of the breaker in the closed position. If the prop fails to achieve the position under the pins, the breaker fails to latch closed and the breaker falls back open.

CAUSE OF OCCURRENCE The cause of the failure of the prop to achieve the required position under the prop pin is a misalignment of the breaker mechanism and internals which has developed over the years of operation. This misalignment creates unequal forces during closure and causes the latching mechanism prop to impact the prop pin causing it to bounce out of position.

Mechanical energy through the breaker from the following sources disrupts prop and prop pin sequence, such that the prop pin forces the prop away from the desired latching position:

• Primary contacts closing

• Primary contact arms hitting the buffer blocks

• Overtravel of the arcing contacts into the metal divider in the female arcing contact(s)

These sources of disruption cause what is referred to as "bounce". "Bounce" is either a stall or change of direction of the prop pin during its travel.

"Bounce" is primarily caused by compression of the primary (main) contact springs and cannot be eliminated, but its effects can be minimized.

PRIOR SIMILAR OCCURRENCES In the past two years, there have not been any Salem LERs that addressed breaker failures.

SAFETY CONSEQUENCES AND IMPLICATIONS There were no safety consequences for this occurrence since the breaker failures were found while the plant was in a defueled condition. However, the implications are that this is a potential common mode failure which could jeopardize the fast closure capability of safety related circuit breakers. The operability of the AC Power Sources at Salem Unit 1 and 2 insures power will be available to supply safety related equipment. In the event safety related equipment is required to start, but is prevented from starting due to a single 0 circuit breaker failing to latch closed, redundant safety equipment would be available. Since the failure mode of the circuit breakers, failing to latch closed, has been identified in more than one circuit breaker at Salem, it is possible that during an event, more than one channel of safety related equipment could be affected. For this occurrence, the public health and safety was not affected.

NRC FORM 366A (4-95)

f 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)

Salem Generating Station, Unit 1 00 96 - 009 TEXT (tf more space is required, use additional copies of NRC Form 366A) (17)

CORRECTIVE ACTIONS For Salem Unit 2 Corrective Actions 1 - 4 will be completed for each breaker prior to that breaker being required to be operable.

1. Breaker mechanism misalignment will be assessed for each breaker.

2. A high speed video camera will be used to determine that the breaker adjustments are satisfactory. The breakers will not be returned to operable status without GE concurrence that the adjustment program and methodology is satisfactory.

3. Procedure changes that incorporate the video acceptance criteria and short term mechanical acceptance criteria will be implemented.

4. The breaker contact velocity will be verified to meet the vendor specifications for opening and closing.

5. An INPO Network TI item was issued on March 15, 1996 and an INPO Network OE notification was issued on May 13, 1996.

6. For Salem Unit 1, the corrective action may be replacement of the breakers, implementation of a modification to resolve the problem, or implementation of Corrective Actions 1 - 4. The selected corrective action will be implemented for each breaker prior to that breaker being required to be operable.

10CFR21 REPORTING 10CFR21 requirements are met by this LER.

NRC FORM 366A (4-95)