ML18102A307

Corrected LER 96-014-00:on 960717,potential Hydrogen Embrittlement on 4kV Breaker Parts Identified.Root Cause Investigation Being Conducted.All NLI Refurbished Breakers Removed Except 2B4D from Vital Loads

ML18102A307
Person / Time
Site:	Salem
Issue date:	08/16/1996
From:	Hassler D Public Service Enterprise Group
To:
Shared Package
ML18102A306	List: ML18102A305 ML18102A307
References
LER-96-014-01, LER-96-14-1, NUDOCS 9608200201
Download: ML18102A307 (4)

Text

NRC FORM 366 U.S.NU R REGULATORY COMMISSION OVED BY OMB NO. 3150--0104 (4-95) EXPIRES 04/30198 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS.

REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE Ll.CENSEE EVENT REPORT (LER) LICENSING PROCESS ANO FED BACK TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (T-8 F33), U.S. NUCLEAR (See reverse for required number of REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF digits/characters for each block) MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

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

SALEM GENERATING STATION, UNIT 1 05000272 1 OF 4 TITLE (4)

Potential Hydrogen Embrittlement on 4KV Breaker Parts EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR I SEQUENTIAL NUMBER

'REVISION NUMBER MONTH DAY YEAR Salem unit2 05000311 07 17 96 96 - 014 - 00 08 16 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) x 50. 73(a)(2)(i) 50.73(a)(2)(viii)

- .. ER 0 20.2203(a)(1) 20.2203(a)(3)(i) 50. 73(a)(2)(ii) 50. 73(a)(2)(>e)

LCVCL (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) x OTHER 20.2203(a)(2)(iii) 50.36(c)(1) 50. 73(a)(2)(v) Spec~in Abstract below or in C Form 366A 20.2203(a)(2)(iv) 50.36(c)(2) 50. 73(a)(2)(vii) Part 21 LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Dennis v. Hassler, LER 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 TONPRDS TONPRDS

'YES SUPPLEMENTAL REPORT E~.?ECTED (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 July 17, 1996 a failure of a roll pin securing a spring for a latch pawl on a 4KV breaker was reviewed and a detennination made that the failure of this pin could cause the breaker to fail. :Further investigation revealed that the roll pin failed as a result of hydrogen errbrittlement. The roll pin failure was an unexpected occurrence and consequently detennined that this condition could place the plant in an unanalyzed condition. Later, an issue involving pemanently applied lubricant which was inadvertently removed from the breakers was identified. This also could potentially affect breaker operation.

The cause of the cracked roll pin was the lack of, knowledge of plating induced hydrogen errbrittlement. The Nuclear Logistics Inc.-~porated (NLI) persor..r::..~ involved in the NLI procedure developnent were not aware that zinc plating of hardened steel parts could produce hydrogen embrittlement and subsequent cracking. The cause of the lubricant being inadvertently rerroved from breaker parts is also due to the lack of knowledge by NLI personnel. NLI is a PSE&G approved vendor for safety related work. Corrective actions include issuance of a stop work order on NLI's breaker activities and replacement of the affected parts and reapplication of the lubricant.

This event is reportable in accordance with 10 CFR 50.73(a) (2) (ii); any event or condition that resulted in the plant being in an unanalyzed condition and in accordance with 10 CFR 21.2 (c).

NRC FORM 366 (4-95) 9608200201 960813 PDR ADOCK 05000272 s PDR

NRC FORM 366A .S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION 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 96 - 014 00 TEXT (If more space is required, use 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 corrponent 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 July 17, 1996 a failure of a roll pin securing a latch pawl on a 4KV breaker was reviewed and a determination made that the failure of this pin could cause the breaker to fail. Further investigation revealed that the roll pin failed as a result of hydrogen ernbrittlernent. The roll pin failure was an unexpected occurrence, and consequently determined that this condition could place the plant in an unanalyzed condition.

Public Service Electric & Gas (PSE&G) contracted with Nuclear Logistics Incorporated (NLI) to overhaul/refurbish 4 KV breakers for Salem Units 1 and 2. NLI is a PSE&G approved vendor for safety related work. NLI utilized clear zinc plating on a number of breaker parts that had been heat treated to a hardness of RC 60. The plated areas should have been masked off so that the hardened surfaces were not subjected to the acid and zinc plate baths. Acid cleaning and electroplating generates hydrogen, which can diffuse into the metal. This can result in instant cracking or delayed cracking. The cracking is not normally dependent on the operating load.

On May 1, 1996 a lockwasher holding the breaker lower arc chutes cracked and broke on site. The remainder of the breaker washers were visually checked and no other similar washers were found. The crack appeared to have been caused by hydrogen ernbrittlement induced when the lockwasher was zinc plated. This condition was reported to the industry through INPO OE 7875 dated June 5, 1996.

During the first week of May, the circuit breakers which were at the Texas facility of NLI were inspected and no problems related to plating or lockwashers were found. PSE&G then asked for u corrplete list of breaker parts that were zinc plated. The list was develc~cd but it did not include the roll pins used on the breakers, including the ratchet drive pawl roll pins. During the same time frame, the vendor reported that the ratchet drive pawl in some circuit breakers was chipping. Efforts then were started to remove all hardened steel parts which were zinc plated by NLI with the intention of replacing them with new unplated parts. When the new parts became unavailable, NLI and PSE&G agreed on an alternate solution to the plating problem: the parts would be heat treated to relieve hyd~ogen induced stress and reinstalled in the circuit breakers. Both NLI and PSE&G agreed that no further zinc plating would be performed. Circuit breakers were then delivered to Salem and some were installed in the plant.

NRC FORM 366A ("-95}

"NRC FORM 366A NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) 05000272 YEAR I SEQUENTIAL NUMBER IREVISION NUMBER 3 OF 4 Salem Generating Station, Unit 1 96 - 014 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

DESCRIPTION OF OCCURRENCE (CONT'D)

On July 16, 1995, a circuit breaker in the Salem breaker shop was being tested prior to installation in the plant. A circuit breaker was found to have its inner latch pawl spring hanging down. The latch pawl itself was not engaging the ratchet wheel. Further inspection revealed that the roll pin that fits inside the bottom of the pawl return spring had broken along its longitude axis. The roll pin that broke normally serves to keep the bottom of the pawl return spring in the proper position. The support plate in which the roll pin is mounted and the roll pin itself appear to have been plated.

Subsequent to the above, an issue involving inadvertently removed lubricant was identified. This was identified during a visual inspection of an NLI rebuilt circuit breaker. The procedures for refurbishment of 4KV circuit breakers included acid cleaning and zinc plating of some mechanical parts. The original equipment manufacturer design included a lubricant which was baked-on some moving parts. The baked-on lubricant (rnol:Ybdenum disulfide) was meant to last the life of the circuit breaker. The molybdenum disulfide is a dry baked-on lubricant that is applied to various rotating and rubbing surfaces on the breaker. This lubricant is applied to minimize component wear. The acid cleaning and zinc plating performed by NLI removed the original baked on lubricant. After the zinc plating of parts was discontinued, the cleaning/polishing process used by NLI still resulted in the removal of the original baked on lubricant.

The effect of the above described problems is that all NLI circuit breakers which had parts zinc plated must be removed from the plant for parts replacement. There were 15 breakers that were involved in the plating issue, and an additional four breakers involving the inadvertent removal of the lubricant. Eleven of the 19 breakers were installed in the plant in vital load cubicles. The buses where these breakers were installed were not operable but were considered available. One of the 11 installed breakers, 2B4D, is currently installed in a vital application and is supplying loads (e.g.

spent fuel pool cooling pump). At the time the broken roll pins.were found, it was not considered prudent, based on existing plant conditions, to remove this breaker. Also, an evaluation determined that failure of the plated roll pins in the breaker would not preclude this breaker from opening/tripping. A contingency plan has been approved for replacement of this breaker and it is expected to be removed in the near future.

CAUSE OF OCCURRENCE The cause of the cracked roll pin was the lack of knowledge of plating induced hydrogen ernbrittlement. The NLI procedure development and subsequent reviews failed to associate zinc plating of hardened steel parts *.:ith hydrogen embrittlement. The NLI personnel involved in the NLI procedure were not aware that zinc plating of hardened steel parts could produce hydrogen ernbrittlement and the subsequent cracking. The cause of the lubricant being inadvertently removed from breaker parts is also due to the lack of knowledge by NLI personnel.

NRC FORM 366A (4-95}

NRC FORM 366A

• NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) 05000272 YEAR I SEQUENTIAL NUMBER

• IREVISION NUMBER 4 OF 4 Salem Generating Station, Unit 1 96 - 014 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

PRIOR SIMILAR OCCURRENCES In the past two years, there has been one Salem LER that addressed breaker failures. LER 272/96-009-00 addressed a potential common mode failure mechanism for 4KV breakers due to misalignment of the breaker mechanism. The plating and lubrication issues discussed in this LER (272/96-014-00) were discovered as a result of the same overhaul work that identified the plating problem discussed above.

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 and the buses are not operable.

However, the implications are that this is a potential common mode failure which could jeopardize the operability of safety related circuit breakers. The operability of the AC Power Sources insures power will be available to supply safety related equipment. In the event safety related equipment "ls required to start, but is prevented from starting due to a single circuit breaker failing, redundant safety equipment would be available. However, it is possible that during an event, more than one channel of safety related equipment could be affected.

The breaker installed in 2B4D was in the closed position and the roll pin was not cracked or missing. The capability to open or trip the circuit breaker was reviewed and was determined not to be corrpromised. The health and safety of the public were not affected by this occurrence.

CORRECTIVE ACTIONS

1. Removed all NLI refurbished breakers, except 2B4D, from vital loads. Breaker 2B4D will be removed when its loads are available to be transferred to another bus.

"2. A QA stop work order was issued to NLI on July 26, 1996.

3. The circuit breakers will be sent for replacement and refurbishment. This will be corrpleted for each breaker prior to that breaker being required to be operable.

4. Further corrective actions will be taken as a result of the root cause evaluation currently being conducted. Significant corrective actions that affect the discussion in this LER, if any, will be reported in a supplement to this LER.

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

NRC FORM 366A (4*95)