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Hazardous Problem of ABB breakers as described and illustrated by the utility, Dominion Nuclear Connecticut to the US NRC on March 13, 2015: “DOMINION NUCLEAR CONNECTICUT. INC. MILLSTONE POWER STATION UNIT 3 10 CFR PART 21 REPORT OF BINDING IN ABB K-L CLOSE LATCHES (PART NUMBER 716610K01)”
[Note what looks like green patina on the defective one: https://en.wikipedia.org/wiki/Patina
The material doesn’t appear appropriate for something so important as a nuclear power station. It’s apparently supposed to be new, or almost new. So, why does it have the green patina? ]
Swedish Swiss ABB clearly has dangerous issues with quality assessment-quality control, at least as recently as last year.
From the Dominion Report:
“For this type of breaker, after opening, the closing spring charging motor runs to charge the closing springs and configure the breaker for the next closing demand. With a stuck or bound secondary close latch, the breaker would trip open on demand, the springs would recharge, and the breaker would reclose. If the trip signal was still present, the breaker would trip again and reclose again. This cycle would continue until the charging motor failed or the associated control power fuses blew. The safety significance of this condition is that circuit breakers credited to open and isolate failed components, protect electrical containment penetrations, prevent emergency diesel generator overloading, or perform other opening control functions, would not perform their intended safety function… The first defective secondary close latch was identified by DNC on January 12, 2015 during a circuit breaker overhaul. On February 24, 2015, DNC concluded that the defect could create a substantial safety hazard, as defined in 10 CFR Part 21, and the responsible company officers were notified. An initial notification of this defect in a basic component was provided to the NRC Operations Center on February 25, 2015 (Reference: Event Notification (EN) 50848).
A total of seven defective secondary close latches, Part No. 716610K01, were identified by DNC (one found during overhaul of a MPS3 K600 breaker and six identified in the warehouse). The seven defective secondary close latches were from Batch Nos. 0000150471 and 0000153854. These secondary close latches are used in ABB K-Line circuit breakers. At MPS3, K-Line circuit breakers are used to open and isolate failed components, protect electrical containment penetrations, prevent emergency diesel generator overloading, and perform other opening control functions.” http://www.nrc.gov/docs/ML1507/ML15079A398.pdf
But, Look What ABB Concludes and How Different Their Images Are:
On June 1, 2015, ABB wrote: “This letter provides notification of a failure to comply with specifications associated with a secondary close latch, part number 716610K01… During installation of a primary close latch and subsequent bench testing at a nuclear utility, mechanical binding was observed between the primary and secondary close latches. This binding prevented the breaker from operating. […]
Based on our investigation and analysis, it has been determined that the failure mode reported is not intermittent in nature. Additionally, there have been no reported in-service field failures due to the oversized feature. Thus, a breaker that is currently operating in switchgear or on the test bench can be left in service with the installed latches.” http://www.nrc.gov/docs/ML1515/ML15155A579.pdf (And what if you need to operate the breaker? Isn’t that what it’s for? It’s worse than having the closure in a double door stick when it’s about to storm! Were defects acceptable when original Swiss Brown Boveri (BBC)-the BB in ABB- was making parts for Nazi submarines?)
Below the ABB pages see more examples of defective breakers constituting nuclear safety concerns, followed by the Dominion complaint document for the record. There are cover letters found at NRC links in both instances.
Yellow Highlight; Red Underline added to Original: http://www.nrc.gov/docs/ML1515/ML15155A579.pdf
Westinghouse had Issues with Stuck Latches and They were a Safety Problem. Why Does ABB Think It’s OK?
Indian Pt 1998: “Auxiliary Feedwater Pump 21, which is an engineered safety feature (ESF), did not operate as expected during the performance surveillance test PMT-1 70… The root cause analysis initiated by Con Edison in connection with this event indicates that the failure of the Auxiliary Feedwater Pump 21 DB-50 supply breaker to close was due to inertial latch binding. This binding was caused by spalling or breaking away of the surface coating on the shaft pin and possibly on the female surface of the bushing of the latch.” http://www.nrc.gov/docs/ML1004/ML100431145.pdf
December 28, 2015 Exelon reported re Three Mile Island that a jammed breaker caused a fire: “On 12/04/07 following four years of service, Three Mile Island (TMI) maintenance personnel performed a scheduled preventive maintenance (PM) activity onthe breaker. During the PM the operating mechanism was found “hung up”. The breaker was successfully cycled several times during the PM performance; however, due to the jamming/hanging up of the operating mechanism during the PM, the breaker was shipped to Westinghouse for repair … The failure of the breaker to fully open resulted in the energized component, “A” train of the Decay Heat Closed Cooling Water System motor (DC-P-lA), to experience “single phasing” (e.g., loss of a single phase of power) which resulted in an increase in motor current. The increase in current ultimately led to a failure of motor insulation causing phase-to-phase and phase-to-ground faults. The fault caused the motor to catch fire. An operator attempted to manually open the breaker. The mechanical binding of the breaker caused the Shunt Trip Actuation (STA) coil to remain energized. This led to damage in the STA coil and resulted in smoke and flames observed. Manual operation of the breaker trip button failed to open the breaker. This required Operations to de-energized the safety related 480V bus to remove power from the failed breaker. De-energizing the safety related 480V bus resulted in entering a significant station risk condition and multiple Limiting Conditions for Operation (LCOs) for de-energized equipment.” http://www.nrc.gov/docs/ML1536/ML15363A009.pdf
From the US NRC, Schneider Electric Latch Problem is a Safety Hazard. The above example suggests that the recommended manual operations might not be a solution for direct safety reasons, as well as indirect ones; being impractical for workers:
“Notification Date: 05/12/2016, Notification Time: 19:23 [ET]
Event Date: 05/10/2016, Event Time: [CDT]”
“PART 21 – INITIAL NOTIFICATION OF MASTERPACT BREAKER FAIL TO CLOSE
The following information was a licensee received facsimile;
“Pursuant to 10CFR 21.21(d)(3)(ii), AZZ/NLI is providing written notification of the identification of a potential defect or failure to comply….
“On the basis of our evaluation, it has been determined that there is sufficient information to determine if the subject condition is left uncorrected could potentially create a Substantial Safety Hazard or could create a Technical Specification Safety Limit violation as it relates to the subject plant applications. The plants will need to evaluate their application to determine if the identified condition could have an impact to the plant operation…. “Schneider Electric (SE) performed testing of three Masterpact NW08 breakers (operated to beyond design life) and duplicated the fail to close condition as described by the plant. It was determined that a standing close signal with a trip/open signal applied is determined to be the root cause of the fail to close issue. The SE testing confirms that the presence of this condition can cause the breaker anti-pump latch to receive excessive forward pressure. When the nose of the latch impacts the close coil plunger, it will ‘rock’ up in the rear, catching on the top of the mechanism plate. Once the close voltage is removed, and the plunger retracts, the latch may or may not let go. If the latch does not release, then application of the close coil voltage will simply activate the close coil plunger and without the latch underneath the plunger, the breaker will not close.… “The circuit breaker will continue to operate if this condition is present however there may need to be human interaction with the circuit breaker by manually pressing the trip/open button on the front of the circuit breaker to free the mechanism.” http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2016/20160513en.html
Serial No. 15-109 Docket No. 50-423 Attachment 1,
Yellow Highlight-Red Underline Added. 10 CFR Part 21 Report Defect Identified in ABB K-Line Breaker Secondary Close Latches (Part Number 716610K01) http://www.nrc.gov/docs/ML1507/ML15079A398.pdf