Information Notice 1994-54, Failures of General Electric Magne-Blast Circuit Breakers to Latch Closed: Difference between revisions
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{{#Wiki_filter:UNITED | {{#Wiki_filter:UNITED STATES NUCLEAR REGULATORY | ||
COMMISSION | |||
===OFFICE OF NUCLEAR REACTOR REGULATION=== | |||
WASHINGTON, D.C. 20555 August 1, 1994 NRC INFORMATION | |||
NOTICE 94-54: FAILURES OF GENERAL ELECTRIC MAGNE-BLAST | |||
CIRCUIT BREAKERS TO LATCH CLOSED | |||
==Addressees== | ==Addressees== | ||
All holders of operating licenses or construction permits for nuclear | All holders of operating | ||
licenses or construction | |||
permits for nuclear power reactors.PurDose The U.S. Nuclear Regulatory | |||
Commission (NRC) is issuing this information | |||
notice to alert addressees | |||
to a condition | |||
in which certain General Electric (GE) medium-voltage | |||
Magne-Blast | |||
circuit breakers may begin to randomly fail to latch closed. It is expected that recipients | |||
will review the information | |||
for applicability | |||
to their facilities | |||
and consider actions, as appropriate, to avoid similar problems. | |||
However, suggestions | |||
contained | |||
in this information | |||
notice are not NRC requirements; | |||
therefore, no specific action or written response is required.Description | |||
of Circumstances | |||
The Maine Yankee Atomic Power Station (Maine Yankee) and the Millstone | |||
Nuclear Power Station (Millstone) | |||
have recently experienced | |||
failures of safety-related | |||
GE Magne-Blast | |||
4160-Vac circuit breakers to latch closed (also called "going trip-free"). | |||
Failures occurred during post-overhaul, preoperational, and in-service | |||
surveillance | |||
testing. At Maine Yankee, failures occurred shortly after an overhaul of the breakers, during troubleshooting | |||
of an indirectly | |||
related problem with limit switches. | |||
The affected breakers have failed to latch on a random basis during up to about two-thirds | |||
of attempted | |||
closures, both electrically | |||
and manually. | |||
At both plants, the affected breakers were among those recently overhauled | |||
by the GE Apparatus | |||
Service Division of Philadelphia, with quality assurance | |||
coverage provided by GE Nuclear Energy (NE) Power Delivery Services (PDS) of King of Prussia, Pennsylvania. | |||
Failure analysis, inspection, and testing of one of the affected breakers from Maine Yankee were performed | |||
at the GE Apparatus | |||
Service Division under the direction of GE NE PDS and the design engineer from the breaker manufacturer, GE Specialty | |||
Breaker Plant. The results were consistent | |||
with onsite testing at both Millstone | |||
and Maine Yankee. The failure analysis activities, observed by NRC and licensee representatives, identified | |||
the primary failure mode, apparent principal | |||
root causes, and the most effective | |||
remedies.9407270127 PmR 2 -O5M qq9 o(up&LB} b gl~lIX v\ | |||
IN 94-54-August 1, 1994 Discussion | |||
The breaker models considered | |||
to be potentially | |||
affected at the present time include (1) Type AM-4.16-350-1H | |||
and (2) Type AM-4.16-250-6, -7, -8, or -9HB.GE is currently | |||
evaluating | |||
other Magne-Blast | |||
models for potential susceptibility. | |||
Among these models, only breakers equipped with one prop reset spring (prop spring), and in which all "Tuf-Loc" (Teflon-coated | |||
fiberglass) | |||
bushings (especially | |||
the prop bushings) | |||
have been replaced with aluminum-bronze | |||
bushings, have recently experienced | |||
unreliable | |||
latching.However, it should be noted that this failure ultimately | |||
results from a combination | |||
of contributing | |||
factors and not all breakers of the potentially | |||
affected type and configuration | |||
are prone to failure. In addition, there have been a few instances (although | |||
not recently) | |||
of one-prop spring breakers with Tuf-Loc prop bushings that have failed to latch due to other unsatisfactory | |||
conditions | |||
within the breaker such as excessive | |||
wear, hardened or insufficient | |||
lubrication, and/or being severely out of adjustment. | |||
No failures are known to GE or the NRC to occur in breakers equipped with two prop springs (included as original equipment | |||
since 1968, or added during maintenance | |||
or repair). The failure analysis testing appeared to confirm the GE position that breakers with two prop springs should not experience | |||
this problem. The details of the failure mode are discussed | |||
in Attachment | |||
1 to this information | |||
notice.Attachment | |||
2 shows the prop springs.It should be noted that, depending | |||
on the severity of the various contributing | |||
conditions, the onset of failure to latch reliably in these breakers may vary, and a breaker that has successfully | |||
passed rigorous post-maintenance | |||
testing and further receipt inspection | |||
and preoperational | |||
testing may subsequently | |||
start failing to latch reliably in service. In recent instances, failures to latch have begun to occur after about 35-50 operations (cycles) following overhaul or repair of the operating | |||
mechanism. | |||
Once started, the failure frequency | |||
has been observed during testing, to vary from 1 failure to latch in as many as 50 consecutive | |||
operations | |||
to 16 failures in 24 attempts. | |||
The operating | |||
characteristics | |||
of a given breaker (in particular, adequacy and consistency | |||
of prop action as explained | |||
in Attachment | |||
1) can indicate the likelihood | |||
of unreliable | |||
latching. | |||
According | |||
to GE, the desired prop action positions | |||
the prop fully forward against its stop, thus providing | |||
maximum engagement | |||
under the prop pin (called prop wipe). However, affected breakers that start (or are likely to start) failing to latch reliably typically exhibit inconsistent (and often less than the design minimum) prop wipe even when they do latch.The NRC and licensees | |||
have expressed | |||
concerns regarding | |||
increased | |||
suscepti-bility to unwanted tripping with less than minimum design prop wipe caused by vibration | |||
or shock (e.g., during a seismic event). The Magne-Blast | |||
design engineer has stated that because of the geometry and magnitude | |||
of forces acting on the prop, once the mechanism | |||
has successfully | |||
latched (even if only barely), it would be extremely | |||
unlikely for the shocks or vibration | |||
associated | |||
with seismic events to cause the prop to move backwards | |||
and olut from under the prop pin. Nevertheless, a breaker that is latched, but with less than the design minimum prop wipe, is not in a condition | |||
for which it was analyzed or in which it was tested during seismic qualification. | |||
IN 94-54 August 1, 1994 Normal prop wipe can be confirmed | |||
with the breaker in its cubicle and closed (in test position if necessary) | |||
in most installations | |||
by visual inspection (using an inspection | |||
mirror and light) without having to get too close to energized | |||
components | |||
or hazardous | |||
mechanism | |||
parts if the switchgear | |||
cabinet door can be opened with appropriate | |||
safety precautions. | |||
Pending issuance of a service advice letter (SAL) by the manufacturer | |||
on this problem or a safety communication | |||
by GE NE, Attachment | |||
2 illustrates | |||
an inspection | |||
hole in the right side of the mechanism | |||
frame through which the prop and prop pin position may be viewed. While the fully forward prop position (to the stop) is the desired condition (maximum wipe), the absence of failures to latch along with consistent | |||
and greater than minimum allowed prop wipe is, according | |||
to GE, indicative | |||
of continued | |||
reliable latching. | |||
However, because minimum prop wipe is not a published | |||
design specification, and because certain other factors (e.g., opening spring adjustment) | |||
may influence | |||
latching reliability, GE has requested | |||
that any licensee experiencing | |||
Magne-Blast | |||
breaker latching problems or noticing changed, inconsistent | |||
or apparently | |||
abnormally | |||
low prop wipe, particularly | |||
following | |||
overhaul or repair including | |||
prop bushing replacement, contact GE NE PDS at (610) 992-6049.Pending installation | |||
of a second prop spring in affected breakers, Maine Yankee has shifted, to the extent possible, its available | |||
dual prop spring breakers to locations | |||
where operability | |||
requires assured latching reliability | |||
for closure or reclosure | |||
during a design-basis | |||
event. For the remaining potentially | |||
affected breakers, Maine Yankee is planning expedited | |||
inspections | |||
with the assistance | |||
of GE NE PDS to aid in its operability | |||
determinations. | |||
===Related Generic Communications=== | |||
Information | |||
Notice 84-29, "General Electric Magne-Blast | |||
Circuit Breaker Problems," dated April 29, 1984.Information | |||
Notice 90-41, "Potential | |||
Failure of General Electric Magne-Blast | |||
Circuit Breakers and AK Circuit Breakers," dated June 12, 1990.Information | |||
Notice 93-91, "Misadjustment | |||
Between General Electric 4.16-KY Circuit Breakers and Their Associated | |||
Cubicles," dated December 3, 1993.Information | |||
Notice 94-02, "Inoperability | |||
of General Electric Magne-Blast | |||
Breaker Because of Misalignment | |||
of Close-Latch | |||
Spring," dated January 7, 1994. | |||
IN 94-54: August 1, 1994 This information | |||
notice requires no specific action or written response. | |||
If you have any questions | |||
about the information | |||
in this notice, please contact one of the technical | |||
contacts listed below or the appropriate | |||
Office of Nuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, Director Division of Operating | |||
===Reactor Support Office of Nuclear Reactor Regulation=== | |||
Technical | |||
contacts: | |||
Stephen Alexander, NRR (301) 504-2995 Kamalakar | |||
Naidu, NRR Sikindra Mitra, NRR (301) 504-2980 (301) 504-2783 Attachments: | |||
1. Details of Failure Mode and Contributing | |||
Factors 2. Magne-Blast | |||
Prop Mechanism | |||
Diagram 3. List of Recently Issued NRC Information | |||
Notices 47 g ^d AnJ-L | |||
Attachment | |||
1 IN 94-54 August 1, 1994 DETAILS OF THE FAILURE MODE AND CONTRIBUTING | |||
FACTORS The cause of the failures to latch cited in the body of the Information | |||
Notice is related to a component | |||
of the Type ML-13 breaker operating | |||
mechanism | |||
called the prop (see Attachment | |||
2). The breaker will fail to latch closed when the prop does not travel forward fast enough (relative | |||
to the motion of the closing linkage) to be in the proper position under the prop pin of the closing linkage as it rises above then descends onto the prop during the closing cycle (whether manually or electrically | |||
initiated). | |||
Absent a trip condition | |||
upon closing, the prop is permitted (by the rotation of the main cam) to be pulled forward under the prop pin by the prop reset spring (or springs when two are fitted). If the slower speed of the prop relative to the pin is such that the pin passes down in front of the prop instead of landing on top of it (called latching) | |||
as it is supposed to, the linkage will"collapse" causing the moving contact arms to immediately | |||
drop down to the open position. | |||
This condition | |||
or action is also called the trip-free condition | |||
because it occurs in the same manner as if a trip signal were present at the breaker tripping mechanism | |||
when the breaker attempts to close, thus preventing | |||
the prop from moving forward and latching.According | |||
to GE, and as apparently | |||
confirmed | |||
by testing, several conditions | |||
must be present to render a given breaker susceptible | |||
to this failure mode.Most fundamental | |||
are the individual | |||
breaker model and configuration, mechanism type, and vintage. Within these constraints, certain modifications | |||
or upgrades that have (or have not) been performed | |||
on a given breaker influence its susceptibility. | |||
Finally, the condition | |||
of the breaker mechanism | |||
in terms of age and type of moving parts, wear, lubrication, and adjustment | |||
can ultimately | |||
be the determining | |||
factor with regard to latching reliability. | |||
Due to their particular | |||
combination | |||
of operating (opening and closing) spring configurations, all 4.16-kilovolt (Kv)-rated, vertical-lift, air-magnetic (Magne-Blast) | |||
breakers of 350-million | |||
volt-ampere (MVA) interrupting | |||
rating (Type AM-4.16-350-1H) | |||
that are fitted with only one prop spring are considered | |||
by GE to be potentially | |||
affected. | |||
Also potentially | |||
affected, owing also to their particular | |||
operating | |||
spring configurations, are those 4.16-Kv, 250-MVA-rated Magne-Blast | |||
breakers with one prop spring that have a 78-kilo-ampere (kA) close-latch | |||
rating (called a "high momentary" rating), which includes Models AM-4.16-250-6, -7, -8, or -9HB (the "H" suffix indicates | |||
the ML-13 type mechanism | |||
and the "B" indicates | |||
the high momentary | |||
rating).Within this population, the major factor determining | |||
susceptibility | |||
is the number of prop springs installed. | |||
With one anomalous | |||
exception (a breaker suspected | |||
of being grossly out of adjustment), only breakers with one prop spring have thus far been reported to experience | |||
unreliable | |||
latching.Breakers of these models built before about 1968 were originally | |||
fitted at the factory with a single prop spring. After this time, breakers with close and latch ratings of 77 Ka or 78 Ka were factory fitted with two prop springs, in order, according | |||
to GE, to make the breakers less sensitive | |||
to fit and adjustment | |||
tolerances | |||
and to facilitate | |||
factory setup. The failure analysis testing indicated | |||
that breakers built with or modified subsequently | |||
to add a second (upper) prop spring, and that are not otherwise | |||
in severely out of tolerance | |||
condition, should not be susceptible | |||
to this failure mode. | |||
Attachment | |||
1: IN 94-54 August 1, 1994 The breaker manufacturer, in GE Service Advice Letter (SAL) No. 073-348.1, issued in December 1990, recommended | |||
replacement | |||
of the main (lower) prop spring with an improved spring (called the "gold" prop spring because of the color of its cadmium plating). | |||
NRC Information | |||
Notice 90-41, "Potential | |||
Failure of General Electric Magne-Blast | |||
Circuit Breakers and AK Circuit Breakers," also addressed | |||
this problem. The gold prop spring has been fitted in breakers built since 1971, due to fatigue failures reported in the original spring. Although SAL 073-348.1 did describe the dual prop spring configuration, it did not address the addition of a second prop spring. See Attachment | |||
2.Recent breaker overhauls/repairs | |||
that included replacement | |||
of the Tuf-Loc (Teflon-coated | |||
fiberglass) | |||
prop bushings with aluminum-bronze | |||
prop bushings, in conjunction | |||
with cleaning and relubrication | |||
of the closing linkage and renewal of worn parts have not been demonstrated | |||
conclusively | |||
to be the sole cause of the recently reported failures to latch. However, they appear to have been the common precipitating | |||
events. In breakers of the affected models with one prop spring that have had all the Tuf-Loc bushings (except for the prop bushings) | |||
replaced with aluminum-bronze, the recently reported failures to latch have begun to occur after about 35-50 operations (cycles) after completion | |||
of overhaul or repair that included replacement | |||
of the Tuf-Loc prop bushings with aluminum-bronze. | |||
Since 1975, these breakers have been fitted with aluminum-bronze | |||
sleeve bearings or bushings in their mechanisms (except for the prop bushings) | |||
for improved wear characteristics. | |||
Many of the older Magne-Blast | |||
breakers, in accordance | |||
with GE SAL 073-318.1 (and .1A), issued in 1977, and 318.2, issued in 1979, have had their original Tuf-Loc bushings replaced with the aluminum-bronze | |||
bushings. | |||
IE Information | |||
Notice 84-29, "GE Magne-Blast | |||
Circuit Breaker Problems," also addressed | |||
this issue. The factory bushing replacement | |||
kits, supplied under catalog no. 0156C9403G001, did not include replacement | |||
bushings for the prop. Hence, most prop bushing replacements | |||
have been performed | |||
only recently.When other conditions | |||
in a breaker are conducive | |||
to marginal latching, it appears that the new bushings, in conjunction | |||
with reduced friction in the closing linkage from the overhaul, cleaning and new lubricant, may shift the force and speed balance in the mechanism. | |||
The shift can be sufficient | |||
to speed up the motion of the closing linkage and prop pin relative to the prop (which also may actually be slightly retarded) | |||
beyond design margins. Under these conditions, a single prop spring can no longer move the prop forward fast enough to latch reliably, or if it does latch, to ensure the desired prop wipe. Where the second prop spring has been installed | |||
in conjunction | |||
with the mechanism | |||
overhaul, failure to latch reliably in the manner described | |||
herein has not been reported, and according | |||
to GE, as confirmed | |||
by testing, would not be expected to occur. Disassembly | |||
and detailed inspection | |||
of the Maine Yankee breaker operating | |||
mechanism | |||
after testing revealed no additional | |||
significant | |||
factors contributing | |||
to the failures to latch experienced | |||
by the test breaker.Therefore, the test results appear to have confirmed | |||
the factors to which close-latch | |||
reliability | |||
is most sensitive. | |||
Attachment | |||
2 1, IN 94-54 August 1, 1994 Page 1 of I MAGNE-BLAST | |||
OPERATING | |||
MECHANISM | |||
PROP DIAGRAMS 1.2.3.4.5.5A.6.7.8.9.10.11.12.13.14.15.16.17.Handle Trip Coil Support Trip Coil Trip Armature PROP SPRING SECOND PROP SPRING (if fitted)Cam Follower Roller Trip Shaft Trip Latch Trip Latch Roller Roller Support Crank Shaft Cranks PROP PIN PROP Drive Shaft Cam PROP BUSHING FRONT OF BREAKER Figure 1 (Adapted From Figure 7 of GE Instruction | |||
Book GEI-88761) | |||
Figure 2: Right Side View of ML-13 Operating | |||
Mechanism (From Figure 4 of GE Instruction | |||
Book GEI-88761) | |||
Attachment | |||
3' IN 94-54 August 1, 1994 LIST OF RECENTLY ISSUED NRC INFORMATION | |||
NOTICES Information | |||
Date of Notice No. Subject Issuance Issued to 91-45, Supp. 1 Possible Malfunction | |||
of Westinghouse | |||
ARD, BFD, and NBFD Relays, and A200 DC and DPC 250 Magnetic Contactors | |||
07/29/94 All holders of OLs or CPs for nuclear power reactors.94-42, Supp. 1 Cracking in the Lower Region of the Core Shroud in Boiling-Water | |||
Reactors 07/19/94 All holders for boiling (BWRs).of OLs or CPs water reactors 94-53 94-52 94-51 94-50 94-49 Hydrogen Gas Burn Inside Pressurizer | |||
During Welding Inadvertent | |||
Containment | |||
Spray and Reactor Vessel Draindown | |||
at Millstone Unit 1 Inappropriate | |||
Greasing of Double Shielded Motor Bearings Failure of General Electric Contactors | |||
to Pull in at the Required Voltage Failure of Torque Switch Roll Pins Snubber Lubricant Degradation | |||
in High-Temperature | |||
===Environments=== | |||
Unanticipated | |||
and Unin-tended Movement of Fuel Assemblies | |||
and other Components | |||
due to Improper Operation | |||
of Refueling Equipment 07/18/94 07/15/94 07/15/94 07/14/94 07/06/94 06/30/94 06/28/94 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.94-48 94-13, Supp. 1 OL = Operating | |||
License CP = Construction | |||
Permit | |||
IN 94-54 August 1, 1994 This information | |||
notice requires no specific action or written response. | |||
If you have any questions | |||
about the information | |||
in this notice, please contact one of the technical | |||
contacts listed below or the appropriate | |||
Office of Nuclear Reactor Regulation (NRR) project manager.orig /s/'d by CIGrimes/for | |||
Brian K. Grimes, Director Division of Operating | |||
===Reactor Support Office of Nuclear Reactor Regulation=== | |||
Technical | |||
contacts: | |||
Stephen Alexander, NRR (301) 504-2995 Kamalakar | |||
Naidu, NRR (301) 504-2980 Sikindra Mitra, (301) 504-2783 NRR Attachments: | |||
1. Details of Failure Mode and Contributing | |||
Factors 2. Magne-Blast | |||
Prop Mechanism | |||
Diagram 3. List of Recently Issued NRC Information | |||
Notices*SEE PREVIOUS VIB:DRIL SAlexander* | |||
05/19/94 CONCURRENCE | |||
VIB:DRIL KNaidu*04/14/94 SC/VIB:DRIL | |||
GCwal ina*05/19/94 TECHED MMejac*04/18/94 C/VIB:DRIL:NRR | |||
LNorrholm* | |||
05/24/94 D/DRIL:NRR | |||
CERossi*05/27/94 EELB:DE:NRR | |||
SMitra*07/06/94 C/EELB:DE:NRR | |||
CBerlinger* | |||
07/11/94 OGCB:DORS:NRR | |||
PWen*07/13/94 AC/OGCB:DORS:NRR | |||
ELDoolittle* | |||
07/14/94 D/:DORS:NRR | |||
BKGrimes(Y- | |||
1 07D OT/94 NAM DOCUMENT NAME: OFFICIAL RECORD COPY 94-54. IN NOTE: The PMs for Maine Yankee (E. Trottier) | |||
and Millstone-1 (J. Andersen)have been informed of the development | |||
of this information | |||
notice, and their comments have been incorporated. | |||
Steve Alexander | |||
of the Vender Inspection | |||
Branch has the technical | |||
accuracy of this information | |||
notice.been incorporated. | |||
consulted | |||
with GE on GE's comments have Peter Wen, 7/13/94 IN 94-XX July XX, 1994 This information | |||
notice requires no specific action or written response. | |||
If you have any questions | |||
about the information | |||
in this notice, please contact one of the technical | |||
contacts listed below or the appropriate | |||
Office of Nuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, Director Division of Operating | |||
===Reactor Support Office of Nuclear Reactor Regulation=== | |||
Technical | |||
contacts: | |||
Stephen Alexander, NRR (301) 504-2995 Kamalakar | |||
Naidu, NRR Sikindra Mitra, NRR (301) 504-2980 (301) 504-2783 Attachments: | |||
1. Details of Failure Mode and Contributing | |||
Factors 2. Magne-Blast | |||
Prop Mechanism | |||
Diagram 3. List of Recently Issued NRC Information | |||
Notices*SEE PREVIOUS VIB:DRIL SAlexander* | |||
05/19/94 CONCURRENCE | |||
VIB:DRIL KNaidu*04/14/94 SC/VIB:DRIL | |||
GCwal ina*05/19/94 TECHED MMejac*04/18/94 C/VIB:DRIL:NRR | |||
LNorrholm* | |||
05/24/94 D/DRIL:NRR | |||
CERossi*05/27/94 AO/ :DORS:NRR E 4 ff^1ttl e 07/" /4 EELB:DE:NRR | |||
SMitra*07/06/94 C/EELB:DE:NRR | |||
CBerlinger* | |||
07/11/94 OGCB: QRS:NRR PWen tV\1 07/13 /94 D/:DORS:NRR | |||
BKGrimes 07/ /94 4 DOCUMENT NAME: GEMAGNET.IN | |||
OFFICIAL RECORD COPY NOTE: The PMs for Maine Yankee (E. Trottier) | |||
and Millstone-I (J. Andersen)have been informed of the development | |||
of this information | |||
notice, and their comments have been incorporated. | |||
Steve Alexander | |||
of the Vender Inspection | |||
Branch has consulted | |||
with GE on the technical | |||
accuracy of this information | |||
notice. GE's comments have been incorporated. | |||
Peter Wen, 7/13/94 IN 94-XX July XX, 1994 Normal prop wipe can be confirmed | |||
with the breaker in its cubicle and closed (in test position if necessary) | |||
in most installations | |||
by visual inspection (using an inspection | |||
mirror and light) without having to get too close to energized | |||
components | |||
or hazardous | |||
mechanism | |||
parts if the switchgear | |||
cabinet door can be opened with appropriate | |||
safety precautions. | |||
Pending issuance of a service advice letter (SAL) by the manufacturer | |||
on this problem or a safety communication | |||
by GE NE, Attachment | |||
2 illustrates | |||
an inspection | |||
hole in the right side of the mechanism | |||
frame through which the prop and prop pin position may be viewed. While the fully forward prop position (to the stop) is the desired condition (maximum wipe), the absence of failures to latch along with consistent | |||
and greater than minimum allowed prop wipe is, according | |||
to GE, indicative | |||
of continued | |||
reliable latching. | |||
However, because minimum prop wipe is not a published | |||
design specification, and because certain other factors (e.g., opening spring adjustment) | |||
may influence | |||
latching reliability, GE has requested | |||
that any licensee experiencing | |||
Magne-Blast | |||
breaker latching problems or noticing changed, inconsistent | |||
or apparently | |||
abnormally | |||
low prop wipe, particularly | |||
following | |||
overhaul or repair including | |||
prop bushing replacement, contact GE NE PDS at 610-992-6049. | |||
Pending installation | |||
of a second prop spring in affected breakers, Maine Yankee has shifted, to the extent possible, its available | |||
dual prop spring breakers to locations | |||
where operability | |||
requires assured latching reliability | |||
for closure or reclosure | |||
during a design-basis | |||
event. For the remaining potentially | |||
affected breakers, Maine Yankee is planning expedited | |||
inspections | |||
with the assistance | |||
of GE NE PDS to aid in its operability | |||
determinations. | |||
NRC Information | |||
Notice 94-XX, issued May XX, 1994, discusses | |||
other recently identified | |||
problems impacting | |||
Magne-Blast | |||
operability, related to defective and improperly | |||
installed | |||
GE CR2940 limit switches.This information | |||
notice requires no specific action or written response.If you have any questions | |||
about the information | |||
in this notice, please contact one of the technical | |||
contacts listed below or the appropriate | |||
Office of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKGRIMES Brian K. Grimes, Director Division of Operating | |||
===Reactor Support Office of Nuclear Reactor Regulation=== | |||
Technical | |||
contacts: | |||
Stephen Alexander, NRR Kamalakar | |||
Naidu, NRR (301) 504-2995 (301) 504-2980 Sikindra Mitra, NRR (301) 504-2783 Attachments: | |||
1. Details of Failure Mode and Contributing | |||
Factors 2. Magne-Blast | |||
Prop Mechanism | |||
Diagram 3. List of Recently Issued NRC Information | |||
Notices VIB:DRIL VIB:DRIL SC/VIB:DRIL | |||
SAlexander* | |||
KNaidu* GCwalina*05/19/94 04/14/94 05/19/94 C/VIB:DRIL:NRR | |||
D/DRIL:NRR | |||
EELB:DE(PR, 1 LNorrholm* | |||
CERossi* Smitya afb'05/24/94 05/27/94 cuff /94 OGCB:DORS:NRR | |||
AC/OGCB:DORS:NRR | |||
D7:DORS:NRR | |||
PWen BKGrimes 07/ /94 07/ /94 07/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: I*See previous concurrence | |||
TECHED MMejac*04/18/94 C/EELB:DE:N | |||
f )Cjerlinger | |||
OV/tt/94 MAGNE3AT.GE | |||
IN 94-XX May XX, 1994 Normal prop wi can be confirmed | |||
with the breaker in its cubicle and closed (in test position if necessary) | |||
in most installations | |||
by visual inspection (using an inspectio | |||
mirror and light) without having to get too close to energized | |||
components | |||
r hazardous | |||
mechanism | |||
parts if the switchgear | |||
cabinet door can be opened wit appropriate | |||
safety precautions. | |||
Pending issuance of a service advice letter (SAL) by the manufacturer | |||
on this problem or a safety communication | |||
by GE NE, Attchment | |||
2 illustrates | |||
an inspection | |||
hole in the right side of the mechanism | |||
ame through which the prop and prop pin position may be viewed. While the fully forward prop position (to the stop) is the desired condition (maximum wipe), the absence of failures to latch along with consistent | |||
and greater than minim allowed prop wipe is, according | |||
to GE, indicative | |||
of continued | |||
reliable la thing. However, because minimum prop wipe is not a published | |||
design specificatio, and because certain other factors (e.g., opening spring adjustment) | |||
may i'hluence | |||
latching reliability, GE has requested | |||
that any licensee experiencing | |||
14 gne-Blast | |||
breaker latching problems or noticing changed, inconsistent | |||
or appare tly abnormally | |||
low prop wipe, particularly | |||
following | |||
overhaul or repair in uding prop bushing replacement, contact GE NE PDS at 610-992-6049. | |||
Pending installation | |||
of a second prop sprin in affected breakers, Maine Yankee has shifted, to the extent possible, its aailable dual prop spring breakers to locations | |||
where operability | |||
requires assured latching reliability | |||
for closure or reclosure | |||
during a design-basis | |||
event. For the remaining potentially | |||
affected breakers, Maine Yankee is plannin expedited | |||
inspections | |||
with the assistance | |||
of GE NE PDS to aid in its operabilMty | |||
determinations. | |||
NRC Information | |||
Notice 94-XX, issued May XX, 1994, discusles | |||
other recently identified | |||
problems impacting | |||
Magne-Blast | |||
operability, rela ed to defective and improperly | |||
installed | |||
GE CR2940 limit switches.This information | |||
notice requires no specific action or w *tten response.If you have any questions | |||
about the information | |||
in this notice, lease contact one of the technical | |||
contacts listed below or the appropriate | |||
Of ce of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKGRIMES Brian K. Grimes, Director Division of Operating | |||
===Reactor Support Office of Nuclear Reactor Regulation=== | |||
Technical | |||
contacts: | |||
Stephen Alexander, NRR Kamalakar | |||
Naidu, NRR (301) 504-2995 (301) 504-2980 Attachments: | |||
1. Details of Failure Mode and Contributing | |||
Factors 2. Magne-Blast | |||
Prop Mechanism | |||
Diagram 3. List of Recently Issued NRC Information | |||
Notices VIB:DRIL VIB:DRIL SC/VIB:DRIL | |||
SAlexander* | |||
KNaidu* GCwalina*05/19/94 04/14/94 05/19/94 C/VI BDRIL:NRR | |||
D/D I *N ChftA EELB:DE:NRR | |||
LN I film SMitra'05JK 1 /94 05/17g 4\ 05/ /94 OGCB:DORS:NRR | |||
AC/OGCB:DORS | |||
:NRR D/:DORS:NRR | |||
PWen AJKugler BKGrimes 05/ /94 05/ /94 05/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: I*See previous TECHED MMeJac*04/18/94 C/EELB:DE:NRF | |||
CBerlinger | |||
05/ /94 concurrence | |||
MAGNE3AT.GE | |||
IN 94-XX May XX, 1994 Normal prop wipe can be confirmed | |||
with the breaker in its cubicle and closed (in test position if necessary) | |||
in most installations | |||
by visual inspection (using an inspection | |||
mirror and light) without having to get too close to energized | |||
components | |||
or hazardous | |||
mechanism | |||
parts if the switchgear | |||
cabinet can be opened with appropriate | |||
safety precautions. | |||
Pending issuance of a serv' advice letter (SAL) by the manufacturer | |||
on this problem or a safety communic ion by GE NE, Attachment | |||
2 illustrates | |||
an inspection | |||
hole in the right side the mechanism | |||
frame through which the prop and prop pin position may be viewed. hile the fully forward prop position (to the stop) is the desired condition | |||
aximum wipe), the absence of failures to latch along with consistent | |||
and grea than minimum allowed prop wipe is, according | |||
to GE, indicative | |||
of continue reliable latching. | |||
However, because minimum prop wipe is not a published | |||
desig specification, and because certain other factors (e.g., opening spring adjus ent) may influence | |||
latching reliability, GE has requested | |||
that any licensee e eriencing | |||
Magne-Blast | |||
breaker latching problems or noticing changed, inconsiste | |||
or apparently | |||
abnormally | |||
low prop wipe, particularly | |||
following | |||
overhaul o repair including | |||
prop bushing replacement, contact GE NE PDS at 215-992-6049. | |||
Pending installation | |||
of a secon rop spring in affected breakers, Maine Yankee has shifted to the extent possibe, its available | |||
dual prop spring breakers to locations | |||
where operability | |||
quires assured latching reliability | |||
for closure or reclosure | |||
during a design-b is event. For the remaining potentially | |||
affected breakers, Maine Yankee planning expedited | |||
inspections | |||
with the assistance | |||
of GE NE PDS to aid in it operability | |||
determinations. | |||
NRC Information | |||
Notice 94-XX, issued May XX, 19 , discusses | |||
other recently identified | |||
problems impacting | |||
Magne-Blast | |||
operab ity, related to defective and improperly | |||
installed | |||
GE CR2940 limit switches.This information | |||
notice requires no specific ac ion or written response.If you have any questions | |||
about the information | |||
in th notice, please contact one of the technical | |||
contacts listed below or the appro late Office of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKGRIMES Brian K. Grimes, Directo Division of Operating | |||
===Reac or Support Office of Nuclear Reactor Regulation=== | |||
Technical | |||
contacts: | |||
Stephen Alexander, NRR Kamalakar | |||
Naidu, NRR (301) 504-2995 (301) 504-2980 Attachments: | |||
1. Details of Failure Mode and Contributing | |||
Factors 2. Magne-Blast | |||
Prop Mechanism | |||
Diagram 3. List of Recently Issued NRC Information | |||
Notices VIB:DRIL VIB:DRIL SC V :DRIL TECHED S~lexanderl'J | |||
K &aicu , G & S1na MMejac*05/(9/94 04/ W 94* O'5/94 04/18/94 C VIB:DRIL:NRR | |||
D/DRIL:NRR | |||
EELB:DE:NRR | |||
CIEELB:DE:NRR | |||
===Lgrrholm CERossi SMitra Caerlinger=== | |||
05/ /94 05/ /94 05/ /94 05/ /94 OGCB:DORS:NRR | |||
AC/OGCB:DORS:NRR | |||
D/:DORS:NRR | |||
PWen AJKugler BKGrimes 05/ /94 05/ /94 05/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNE3AT.GE | |||
<&c rfmtC'al Cak"vyc.t | |||
IN 94-XX April XX, 1994 Prop wipe can be etermined | |||
in most installations | |||
by visual inspection | |||
without having to get too lose to hazardous | |||
mechanism | |||
parts if the switchgear | |||
cabinet door can be opened fely. Pending issuance of a SAL by the manufacturer | |||
on this problem (and/or Service Information | |||
Letter by GE NE), Attachment | |||
2 illustrates | |||
one locatlo where the prop position may be seen. While fully forward prop position (t the stop) is the desired condition (maximum wipe), the absence of failures to latch along with consistent | |||
and greater than minimum allowed prop wipe is according | |||
to GE, indicative | |||
of continued reliable latching. | |||
However, cause minimum prop wipe is not a published design specification, and becau certain other factors (e.g. opening spring adjustment) | |||
may influence | |||
latchin reliability, GE has requested | |||
that any licensee experiencing | |||
Magne-Blast | |||
eaker latching problems or noticing changed, inconsistent | |||
or what appear to be abnormally | |||
low prop wipe, parti-cularly following | |||
prop bushing replacemnt, contact GE NE PDS at 215-992-6049. | |||
In the meantime, pending installat | |||
n of a second prop spring in its affected breakers, Maine Yankee has shift to the extent possible, its available | |||
dual prop spring breakers to loca Ions where operability | |||
requires assured latching reliability | |||
for closure or closure during a design basis event. For the remaining | |||
suspect breakers, Mane Yankee has undertaken | |||
expedited | |||
inspections | |||
with the assistance | |||
of G E PDS to aid in its operabil-ity determinations. | |||
NRC Information | |||
Notice 94-X issued April XX, 1994, dis-cusses other recently identified | |||
problems impactin Magne-Blast | |||
operability, related to defective | |||
and improperly | |||
installed | |||
GE CR 940 limit switches.This information | |||
notice requires no specific ac on or written response.If you have any questions | |||
about the information | |||
in thi notice, please contact the technical | |||
contacts listed below or the appropriate | |||
ffice of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKGRIMES Brian K. Grimes, Directo Division of Operating | |||
Reac or Support Office of Nuclear Reactor R ulation Technical | |||
contacts: | |||
Stephen Alexander, NRR (301) 504-2995 Kamalakar | |||
Naidu, NRR (301) 504-2980 Attachments: | |||
1. Details of Failure Mode and Contributing | |||
Factors 2. Magne-Blast | |||
Prop Mechanism | |||
Diagram 3. List of Recently Issued NRC Information | |||
Notices VIB:DRIL VIB:DRIL SC/VIB:DRIL | |||
TECHED Salexander | |||
Knaidu Gcwalina 41./V (,AA-04/ /94 04/ /94 04/ /94 04/AR/94 C/VIB:DRIL:NRR | |||
D/DRIL:NRR | |||
EELB:DE:NRR | |||
C/EELB:DE:NRR | |||
Lnorrholm | |||
===CERossi SMitra Cberlinger=== | |||
04/ /94 04/ /94 04/ /94 04/ /94 OGCB:DORS:NRR | |||
AC/OGCB:DORS:NRR | |||
D/:DORS:NRR | |||
PWen AJKugler BKGrimes 04/ /94 04/ /94 04/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNBLST.IN | |||
IN 94-XX April XX, 1994 Prop wipe can be termined in most installations | |||
by visual inspection | |||
without having to get too c eto hazardous | |||
mechanism | |||
parts if the switchgear | |||
cabinet door can be opened sa ly. Pending issuance of a SAL by the manufacturer | |||
on this problem (and/or a rvice Information | |||
Letter by GE NE), Attachment | |||
2 illustrates | |||
one location ere the prop position may be seen. While fully forward prop position (to t stop) is the desired condition (maximum wipe), the absence of failures to lat h along with consistent | |||
and greater than minimum allowed prop wipe is, a cording to GE, indicative | |||
of continued reliable latching. | |||
However, bec se minimum prop wipe is not a published design specification, and because ertain other factors (e.g. opening spring adjustment) | |||
may influence | |||
latching eliability, GE has requested | |||
that any licensee experiencing | |||
Magne-Blast | |||
breker latching problems or noticing changed, inconsistent | |||
or what appears o be abnormally | |||
low prop wipe, parti-cularly following | |||
prop bushing replacem t, contact GE NE PDS at 215-992-6049. | |||
In the meantime, pending installatlo | |||
of a second prop spring in its affected breakers, Maine Yankee has shifte to the extent possible, its available | |||
dual prop spring breakers to loca ions where operability | |||
requires assured latching reliability | |||
for closure or eclosure during a design basis event. For the remaining | |||
suspect breakers, M ne Yankee has undertaken | |||
expedited | |||
inspections | |||
with the assistance | |||
of G NE PDS to aid in its operabil-ity determinations. | |||
NRC Information | |||
Notice 94- , issued April XX, 1994, dis-cusses other recently identified | |||
problems impact g Magne-Blast | |||
operability, related to defective | |||
and improperly | |||
installed | |||
GE R2940 limit switches.This information | |||
notice requires no specific ction or written response.If you have any questions | |||
about the information | |||
in \this notice, please contact the technical | |||
contacts listed below or the appropri te Office of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKG IMES Brian K. Grimes, irector Division of Operat ng Reactor Support Office of Nuclear Reactor Regulation | |||
Technical | |||
contacts: Stephen Alexander, NRR (301) 504-2995 Kamalakar | |||
Naidu, NRR (301) 504-2980 Attachments: | |||
1. Details of Failure Mode and Contributing | |||
Factors 2. Magne-Blast | |||
Prop Mechanism | |||
Diagram 3. List of Recently Issued_ RC Information | |||
Notices VIB:DRIL VIB:DRI SC/VIB:DRIL | |||
Salexand 9k Knaidu Gcwalina 04//5'/94 | |||
04/14/94 s '4, 04/ /94 C/VIB:DRIL:NRR | |||
D/DRIL:NRR | |||
EELB:DE:NRR | |||
Lnorrholm | |||
CERossi SMitra 04/ /94 04/ /94 04/ /94 OGCB:DORS:NRR | |||
AC/OGCB:DORS:NRR | |||
D/:DORS:NRR | |||
PWen AJKugler BKGrimes 04/ /94 04/ /94 04/ /94 TECHED 04/ /94 C/EELB:DE:NRR | |||
Cberlinger | |||
}} | 04/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNBLST.IN}} | ||
{{Information notice-Nav}} | {{Information notice-Nav}} |
Revision as of 13:58, 31 August 2018
UNITED STATES NUCLEAR REGULATORY
COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 August 1, 1994 NRC INFORMATION
NOTICE 94-54: FAILURES OF GENERAL ELECTRIC MAGNE-BLAST
CIRCUIT BREAKERS TO LATCH CLOSED
Addressees
All holders of operating
licenses or construction
permits for nuclear power reactors.PurDose The U.S. Nuclear Regulatory
Commission (NRC) is issuing this information
notice to alert addressees
to a condition
in which certain General Electric (GE) medium-voltage
Magne-Blast
circuit breakers may begin to randomly fail to latch closed. It is expected that recipients
will review the information
for applicability
to their facilities
and consider actions, as appropriate, to avoid similar problems.
However, suggestions
contained
in this information
notice are not NRC requirements;
therefore, no specific action or written response is required.Description
of Circumstances
The Maine Yankee Atomic Power Station (Maine Yankee) and the Millstone
Nuclear Power Station (Millstone)
have recently experienced
failures of safety-related
GE Magne-Blast
4160-Vac circuit breakers to latch closed (also called "going trip-free").
Failures occurred during post-overhaul, preoperational, and in-service
surveillance
testing. At Maine Yankee, failures occurred shortly after an overhaul of the breakers, during troubleshooting
of an indirectly
related problem with limit switches.
The affected breakers have failed to latch on a random basis during up to about two-thirds
of attempted
closures, both electrically
and manually.
At both plants, the affected breakers were among those recently overhauled
by the GE Apparatus
Service Division of Philadelphia, with quality assurance
coverage provided by GE Nuclear Energy (NE) Power Delivery Services (PDS) of King of Prussia, Pennsylvania.
Failure analysis, inspection, and testing of one of the affected breakers from Maine Yankee were performed
at the GE Apparatus
Service Division under the direction of GE NE PDS and the design engineer from the breaker manufacturer, GE Specialty
Breaker Plant. The results were consistent
with onsite testing at both Millstone
and Maine Yankee. The failure analysis activities, observed by NRC and licensee representatives, identified
the primary failure mode, apparent principal
root causes, and the most effective
remedies.9407270127 PmR 2 -O5M qq9 o(up&LB} b gl~lIX v\
IN 94-54-August 1, 1994 Discussion
The breaker models considered
to be potentially
affected at the present time include (1) Type AM-4.16-350-1H
and (2) Type AM-4.16-250-6, -7, -8, or -9HB.GE is currently
evaluating
other Magne-Blast
models for potential susceptibility.
Among these models, only breakers equipped with one prop reset spring (prop spring), and in which all "Tuf-Loc" (Teflon-coated
fiberglass)
bushings (especially
the prop bushings)
have been replaced with aluminum-bronze
bushings, have recently experienced
unreliable
latching.However, it should be noted that this failure ultimately
results from a combination
of contributing
factors and not all breakers of the potentially
affected type and configuration
are prone to failure. In addition, there have been a few instances (although
not recently)
of one-prop spring breakers with Tuf-Loc prop bushings that have failed to latch due to other unsatisfactory
conditions
within the breaker such as excessive
wear, hardened or insufficient
lubrication, and/or being severely out of adjustment.
No failures are known to GE or the NRC to occur in breakers equipped with two prop springs (included as original equipment
since 1968, or added during maintenance
or repair). The failure analysis testing appeared to confirm the GE position that breakers with two prop springs should not experience
this problem. The details of the failure mode are discussed
in Attachment
1 to this information
notice.Attachment
2 shows the prop springs.It should be noted that, depending
on the severity of the various contributing
conditions, the onset of failure to latch reliably in these breakers may vary, and a breaker that has successfully
passed rigorous post-maintenance
testing and further receipt inspection
and preoperational
testing may subsequently
start failing to latch reliably in service. In recent instances, failures to latch have begun to occur after about 35-50 operations (cycles) following overhaul or repair of the operating
mechanism.
Once started, the failure frequency
has been observed during testing, to vary from 1 failure to latch in as many as 50 consecutive
operations
to 16 failures in 24 attempts.
The operating
characteristics
of a given breaker (in particular, adequacy and consistency
of prop action as explained
in Attachment
1) can indicate the likelihood
of unreliable
latching.
According
to GE, the desired prop action positions
the prop fully forward against its stop, thus providing
maximum engagement
under the prop pin (called prop wipe). However, affected breakers that start (or are likely to start) failing to latch reliably typically exhibit inconsistent (and often less than the design minimum) prop wipe even when they do latch.The NRC and licensees
have expressed
concerns regarding
increased
suscepti-bility to unwanted tripping with less than minimum design prop wipe caused by vibration
or shock (e.g., during a seismic event). The Magne-Blast
design engineer has stated that because of the geometry and magnitude
of forces acting on the prop, once the mechanism
has successfully
latched (even if only barely), it would be extremely
unlikely for the shocks or vibration
associated
with seismic events to cause the prop to move backwards
and olut from under the prop pin. Nevertheless, a breaker that is latched, but with less than the design minimum prop wipe, is not in a condition
for which it was analyzed or in which it was tested during seismic qualification.
IN 94-54 August 1, 1994 Normal prop wipe can be confirmed
with the breaker in its cubicle and closed (in test position if necessary)
in most installations
by visual inspection (using an inspection
mirror and light) without having to get too close to energized
components
or hazardous
mechanism
parts if the switchgear
cabinet door can be opened with appropriate
safety precautions.
Pending issuance of a service advice letter (SAL) by the manufacturer
on this problem or a safety communication
by GE NE, Attachment
2 illustrates
an inspection
hole in the right side of the mechanism
frame through which the prop and prop pin position may be viewed. While the fully forward prop position (to the stop) is the desired condition (maximum wipe), the absence of failures to latch along with consistent
and greater than minimum allowed prop wipe is, according
to GE, indicative
of continued
reliable latching.
However, because minimum prop wipe is not a published
design specification, and because certain other factors (e.g., opening spring adjustment)
may influence
latching reliability, GE has requested
that any licensee experiencing
Magne-Blast
breaker latching problems or noticing changed, inconsistent
or apparently
abnormally
low prop wipe, particularly
following
overhaul or repair including
prop bushing replacement, contact GE NE PDS at (610) 992-6049.Pending installation
of a second prop spring in affected breakers, Maine Yankee has shifted, to the extent possible, its available
dual prop spring breakers to locations
where operability
requires assured latching reliability
for closure or reclosure
during a design-basis
event. For the remaining potentially
affected breakers, Maine Yankee is planning expedited
inspections
with the assistance
of GE NE PDS to aid in its operability
determinations.
Related Generic Communications
Information
Notice 84-29, "General Electric Magne-Blast
Circuit Breaker Problems," dated April 29, 1984.Information
Notice 90-41, "Potential
Failure of General Electric Magne-Blast
Circuit Breakers and AK Circuit Breakers," dated June 12, 1990.Information
Notice 93-91, "Misadjustment
Between General Electric 4.16-KY Circuit Breakers and Their Associated
Cubicles," dated December 3, 1993.Information
Notice 94-02, "Inoperability
of General Electric Magne-Blast
Breaker Because of Misalignment
of Close-Latch
Spring," dated January 7, 1994.
IN 94-54: August 1, 1994 This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, Director Division of Operating
Reactor Support Office of Nuclear Reactor Regulation
Technical
contacts:
Stephen Alexander, NRR (301) 504-2995 Kamalakar
Naidu, NRR Sikindra Mitra, NRR (301) 504-2980 (301) 504-2783 Attachments:
1. Details of Failure Mode and Contributing
Factors 2. Magne-Blast
Prop Mechanism
Diagram 3. List of Recently Issued NRC Information
Notices 47 g ^d AnJ-L
Attachment
1 IN 94-54 August 1, 1994 DETAILS OF THE FAILURE MODE AND CONTRIBUTING
FACTORS The cause of the failures to latch cited in the body of the Information
Notice is related to a component
of the Type ML-13 breaker operating
mechanism
called the prop (see Attachment
2). The breaker will fail to latch closed when the prop does not travel forward fast enough (relative
to the motion of the closing linkage) to be in the proper position under the prop pin of the closing linkage as it rises above then descends onto the prop during the closing cycle (whether manually or electrically
initiated).
Absent a trip condition
upon closing, the prop is permitted (by the rotation of the main cam) to be pulled forward under the prop pin by the prop reset spring (or springs when two are fitted). If the slower speed of the prop relative to the pin is such that the pin passes down in front of the prop instead of landing on top of it (called latching)
as it is supposed to, the linkage will"collapse" causing the moving contact arms to immediately
drop down to the open position.
This condition
or action is also called the trip-free condition
because it occurs in the same manner as if a trip signal were present at the breaker tripping mechanism
when the breaker attempts to close, thus preventing
the prop from moving forward and latching.According
to GE, and as apparently
confirmed
by testing, several conditions
must be present to render a given breaker susceptible
to this failure mode.Most fundamental
are the individual
breaker model and configuration, mechanism type, and vintage. Within these constraints, certain modifications
or upgrades that have (or have not) been performed
on a given breaker influence its susceptibility.
Finally, the condition
of the breaker mechanism
in terms of age and type of moving parts, wear, lubrication, and adjustment
can ultimately
be the determining
factor with regard to latching reliability.
Due to their particular
combination
of operating (opening and closing) spring configurations, all 4.16-kilovolt (Kv)-rated, vertical-lift, air-magnetic (Magne-Blast)
breakers of 350-million
volt-ampere (MVA) interrupting
rating (Type AM-4.16-350-1H)
that are fitted with only one prop spring are considered
by GE to be potentially
affected.
Also potentially
affected, owing also to their particular
operating
spring configurations, are those 4.16-Kv, 250-MVA-rated Magne-Blast
breakers with one prop spring that have a 78-kilo-ampere (kA) close-latch
rating (called a "high momentary" rating), which includes Models AM-4.16-250-6, -7, -8, or -9HB (the "H" suffix indicates
the ML-13 type mechanism
and the "B" indicates
the high momentary
rating).Within this population, the major factor determining
susceptibility
is the number of prop springs installed.
With one anomalous
exception (a breaker suspected
of being grossly out of adjustment), only breakers with one prop spring have thus far been reported to experience
unreliable
latching.Breakers of these models built before about 1968 were originally
fitted at the factory with a single prop spring. After this time, breakers with close and latch ratings of 77 Ka or 78 Ka were factory fitted with two prop springs, in order, according
to GE, to make the breakers less sensitive
to fit and adjustment
tolerances
and to facilitate
factory setup. The failure analysis testing indicated
that breakers built with or modified subsequently
to add a second (upper) prop spring, and that are not otherwise
in severely out of tolerance
condition, should not be susceptible
to this failure mode.
Attachment
1: IN 94-54 August 1, 1994 The breaker manufacturer, in GE Service Advice Letter (SAL) No. 073-348.1, issued in December 1990, recommended
replacement
of the main (lower) prop spring with an improved spring (called the "gold" prop spring because of the color of its cadmium plating).
NRC Information
Notice 90-41, "Potential
Failure of General Electric Magne-Blast
Circuit Breakers and AK Circuit Breakers," also addressed
this problem. The gold prop spring has been fitted in breakers built since 1971, due to fatigue failures reported in the original spring. Although SAL 073-348.1 did describe the dual prop spring configuration, it did not address the addition of a second prop spring. See Attachment
2.Recent breaker overhauls/repairs
that included replacement
of the Tuf-Loc (Teflon-coated
fiberglass)
prop bushings with aluminum-bronze
prop bushings, in conjunction
with cleaning and relubrication
of the closing linkage and renewal of worn parts have not been demonstrated
conclusively
to be the sole cause of the recently reported failures to latch. However, they appear to have been the common precipitating
events. In breakers of the affected models with one prop spring that have had all the Tuf-Loc bushings (except for the prop bushings)
replaced with aluminum-bronze, the recently reported failures to latch have begun to occur after about 35-50 operations (cycles) after completion
of overhaul or repair that included replacement
of the Tuf-Loc prop bushings with aluminum-bronze.
Since 1975, these breakers have been fitted with aluminum-bronze
sleeve bearings or bushings in their mechanisms (except for the prop bushings)
for improved wear characteristics.
Many of the older Magne-Blast
breakers, in accordance
with GE SAL 073-318.1 (and .1A), issued in 1977, and 318.2, issued in 1979, have had their original Tuf-Loc bushings replaced with the aluminum-bronze
IE Information
Notice 84-29, "GE Magne-Blast
Circuit Breaker Problems," also addressed
this issue. The factory bushing replacement
kits, supplied under catalog no. 0156C9403G001, did not include replacement
bushings for the prop. Hence, most prop bushing replacements
have been performed
only recently.When other conditions
in a breaker are conducive
to marginal latching, it appears that the new bushings, in conjunction
with reduced friction in the closing linkage from the overhaul, cleaning and new lubricant, may shift the force and speed balance in the mechanism.
The shift can be sufficient
to speed up the motion of the closing linkage and prop pin relative to the prop (which also may actually be slightly retarded)
beyond design margins. Under these conditions, a single prop spring can no longer move the prop forward fast enough to latch reliably, or if it does latch, to ensure the desired prop wipe. Where the second prop spring has been installed
in conjunction
with the mechanism
overhaul, failure to latch reliably in the manner described
herein has not been reported, and according
to GE, as confirmed
by testing, would not be expected to occur. Disassembly
and detailed inspection
of the Maine Yankee breaker operating
mechanism
after testing revealed no additional
significant
factors contributing
to the failures to latch experienced
by the test breaker.Therefore, the test results appear to have confirmed
the factors to which close-latch
reliability
is most sensitive.
Attachment
2 1, IN 94-54 August 1, 1994 Page 1 of I MAGNE-BLAST
OPERATING
MECHANISM
PROP DIAGRAMS 1.2.3.4.5.5A.6.7.8.9.10.11.12.13.14.15.16.17.Handle Trip Coil Support Trip Coil Trip Armature PROP SPRING SECOND PROP SPRING (if fitted)Cam Follower Roller Trip Shaft Trip Latch Trip Latch Roller Roller Support Crank Shaft Cranks PROP PIN PROP Drive Shaft Cam PROP BUSHING FRONT OF BREAKER Figure 1 (Adapted From Figure 7 of GE Instruction
Book GEI-88761)
Figure 2: Right Side View of ML-13 Operating
Mechanism (From Figure 4 of GE Instruction
Book GEI-88761)
Attachment
3' IN 94-54 August 1, 1994 LIST OF RECENTLY ISSUED NRC INFORMATION
NOTICES Information
Date of Notice No. Subject Issuance Issued to 91-45, Supp. 1 Possible Malfunction
of Westinghouse
ARD, BFD, and NBFD Relays, and A200 DC and DPC 250 Magnetic Contactors
07/29/94 All holders of OLs or CPs for nuclear power reactors.94-42, Supp. 1 Cracking in the Lower Region of the Core Shroud in Boiling-Water
Reactors 07/19/94 All holders for boiling (BWRs).of OLs or CPs water reactors 94-53 94-52 94-51 94-50 94-49 Hydrogen Gas Burn Inside Pressurizer
During Welding Inadvertent
Containment
Spray and Reactor Vessel Draindown
at Millstone Unit 1 Inappropriate
Greasing of Double Shielded Motor Bearings Failure of General Electric Contactors
to Pull in at the Required Voltage Failure of Torque Switch Roll Pins Snubber Lubricant Degradation
in High-Temperature
Environments
Unanticipated
and Unin-tended Movement of Fuel Assemblies
and other Components
due to Improper Operation
of Refueling Equipment 07/18/94 07/15/94 07/15/94 07/14/94 07/06/94 06/30/94 06/28/94 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.94-48 94-13, Supp. 1 OL = Operating
License CP = Construction
Permit
IN 94-54 August 1, 1994 This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.orig /s/'d by CIGrimes/for
Brian K. Grimes, Director Division of Operating
Reactor Support Office of Nuclear Reactor Regulation
Technical
contacts:
Stephen Alexander, NRR (301) 504-2995 Kamalakar
Naidu, NRR (301) 504-2980 Sikindra Mitra, (301) 504-2783 NRR Attachments:
1. Details of Failure Mode and Contributing
Factors 2. Magne-Blast
Prop Mechanism
Diagram 3. List of Recently Issued NRC Information
Notices*SEE PREVIOUS VIB:DRIL SAlexander*
05/19/94 CONCURRENCE
VIB:DRIL KNaidu*04/14/94 SC/VIB:DRIL
GCwal ina*05/19/94 TECHED MMejac*04/18/94 C/VIB:DRIL:NRR
LNorrholm*
05/24/94 D/DRIL:NRR
CERossi*05/27/94 EELB:DE:NRR
SMitra*07/06/94 C/EELB:DE:NRR
CBerlinger*
07/11/94 OGCB:DORS:NRR
PWen*07/13/94 AC/OGCB:DORS:NRR
ELDoolittle*
07/14/94 D/:DORS:NRR
BKGrimes(Y-
1 07D OT/94 NAM DOCUMENT NAME: OFFICIAL RECORD COPY 94-54. IN NOTE: The PMs for Maine Yankee (E. Trottier)
and Millstone-1 (J. Andersen)have been informed of the development
of this information
notice, and their comments have been incorporated.
Steve Alexander
of the Vender Inspection
Branch has the technical
accuracy of this information
notice.been incorporated.
consulted
with GE on GE's comments have Peter Wen, 7/13/94 IN 94-XX July XX, 1994 This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, Director Division of Operating
Reactor Support Office of Nuclear Reactor Regulation
Technical
contacts:
Stephen Alexander, NRR (301) 504-2995 Kamalakar
Naidu, NRR Sikindra Mitra, NRR (301) 504-2980 (301) 504-2783 Attachments:
1. Details of Failure Mode and Contributing
Factors 2. Magne-Blast
Prop Mechanism
Diagram 3. List of Recently Issued NRC Information
Notices*SEE PREVIOUS VIB:DRIL SAlexander*
05/19/94 CONCURRENCE
VIB:DRIL KNaidu*04/14/94 SC/VIB:DRIL
GCwal ina*05/19/94 TECHED MMejac*04/18/94 C/VIB:DRIL:NRR
LNorrholm*
05/24/94 D/DRIL:NRR
CERossi*05/27/94 AO/ :DORS:NRR E 4 ff^1ttl e 07/" /4 EELB:DE:NRR
SMitra*07/06/94 C/EELB:DE:NRR
CBerlinger*
07/11/94 OGCB: QRS:NRR PWen tV\1 07/13 /94 D/:DORS:NRR
BKGrimes 07/ /94 4 DOCUMENT NAME: GEMAGNET.IN
OFFICIAL RECORD COPY NOTE: The PMs for Maine Yankee (E. Trottier)
and Millstone-I (J. Andersen)have been informed of the development
of this information
notice, and their comments have been incorporated.
Steve Alexander
of the Vender Inspection
Branch has consulted
with GE on the technical
accuracy of this information
notice. GE's comments have been incorporated.
Peter Wen, 7/13/94 IN 94-XX July XX, 1994 Normal prop wipe can be confirmed
with the breaker in its cubicle and closed (in test position if necessary)
in most installations
by visual inspection (using an inspection
mirror and light) without having to get too close to energized
components
or hazardous
mechanism
parts if the switchgear
cabinet door can be opened with appropriate
safety precautions.
Pending issuance of a service advice letter (SAL) by the manufacturer
on this problem or a safety communication
by GE NE, Attachment
2 illustrates
an inspection
hole in the right side of the mechanism
frame through which the prop and prop pin position may be viewed. While the fully forward prop position (to the stop) is the desired condition (maximum wipe), the absence of failures to latch along with consistent
and greater than minimum allowed prop wipe is, according
to GE, indicative
of continued
reliable latching.
However, because minimum prop wipe is not a published
design specification, and because certain other factors (e.g., opening spring adjustment)
may influence
latching reliability, GE has requested
that any licensee experiencing
Magne-Blast
breaker latching problems or noticing changed, inconsistent
or apparently
abnormally
low prop wipe, particularly
following
overhaul or repair including
prop bushing replacement, contact GE NE PDS at 610-992-6049.
Pending installation
of a second prop spring in affected breakers, Maine Yankee has shifted, to the extent possible, its available
dual prop spring breakers to locations
where operability
requires assured latching reliability
for closure or reclosure
during a design-basis
event. For the remaining potentially
affected breakers, Maine Yankee is planning expedited
inspections
with the assistance
of GE NE PDS to aid in its operability
determinations.
NRC Information
Notice 94-XX, issued May XX, 1994, discusses
other recently identified
problems impacting
Magne-Blast
operability, related to defective and improperly
installed
GE CR2940 limit switches.This information
notice requires no specific action or written response.If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKGRIMES Brian K. Grimes, Director Division of Operating
Reactor Support Office of Nuclear Reactor Regulation
Technical
contacts:
Stephen Alexander, NRR Kamalakar
Naidu, NRR (301) 504-2995 (301) 504-2980 Sikindra Mitra, NRR (301) 504-2783 Attachments:
1. Details of Failure Mode and Contributing
Factors 2. Magne-Blast
Prop Mechanism
Diagram 3. List of Recently Issued NRC Information
Notices VIB:DRIL VIB:DRIL SC/VIB:DRIL
SAlexander*
KNaidu* GCwalina*05/19/94 04/14/94 05/19/94 C/VIB:DRIL:NRR
D/DRIL:NRR
EELB:DE(PR, 1 LNorrholm*
CERossi* Smitya afb'05/24/94 05/27/94 cuff /94 OGCB:DORS:NRR
AC/OGCB:DORS:NRR
D7:DORS:NRR
PWen BKGrimes 07/ /94 07/ /94 07/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: I*See previous concurrence
TECHED MMejac*04/18/94 C/EELB:DE:N
f )Cjerlinger
OV/tt/94 MAGNE3AT.GE
IN 94-XX May XX, 1994 Normal prop wi can be confirmed
with the breaker in its cubicle and closed (in test position if necessary)
in most installations
by visual inspection (using an inspectio
mirror and light) without having to get too close to energized
components
r hazardous
mechanism
parts if the switchgear
cabinet door can be opened wit appropriate
safety precautions.
Pending issuance of a service advice letter (SAL) by the manufacturer
on this problem or a safety communication
by GE NE, Attchment
2 illustrates
an inspection
hole in the right side of the mechanism
ame through which the prop and prop pin position may be viewed. While the fully forward prop position (to the stop) is the desired condition (maximum wipe), the absence of failures to latch along with consistent
and greater than minim allowed prop wipe is, according
to GE, indicative
of continued
reliable la thing. However, because minimum prop wipe is not a published
design specificatio, and because certain other factors (e.g., opening spring adjustment)
may i'hluence
latching reliability, GE has requested
that any licensee experiencing
14 gne-Blast
breaker latching problems or noticing changed, inconsistent
or appare tly abnormally
low prop wipe, particularly
following
overhaul or repair in uding prop bushing replacement, contact GE NE PDS at 610-992-6049.
Pending installation
of a second prop sprin in affected breakers, Maine Yankee has shifted, to the extent possible, its aailable dual prop spring breakers to locations
where operability
requires assured latching reliability
for closure or reclosure
during a design-basis
event. For the remaining potentially
affected breakers, Maine Yankee is plannin expedited
inspections
with the assistance
of GE NE PDS to aid in its operabilMty
determinations.
NRC Information
Notice 94-XX, issued May XX, 1994, discusles
other recently identified
problems impacting
Magne-Blast
operability, rela ed to defective and improperly
installed
GE CR2940 limit switches.This information
notice requires no specific action or w *tten response.If you have any questions
about the information
in this notice, lease contact one of the technical
contacts listed below or the appropriate
Of ce of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKGRIMES Brian K. Grimes, Director Division of Operating
Reactor Support Office of Nuclear Reactor Regulation
Technical
contacts:
Stephen Alexander, NRR Kamalakar
Naidu, NRR (301) 504-2995 (301) 504-2980 Attachments:
1. Details of Failure Mode and Contributing
Factors 2. Magne-Blast
Prop Mechanism
Diagram 3. List of Recently Issued NRC Information
Notices VIB:DRIL VIB:DRIL SC/VIB:DRIL
SAlexander*
KNaidu* GCwalina*05/19/94 04/14/94 05/19/94 C/VI BDRIL:NRR
D/D I *N ChftA EELB:DE:NRR
LN I film SMitra'05JK 1 /94 05/17g 4\ 05/ /94 OGCB:DORS:NRR
AC/OGCB:DORS
- NRR D/:DORS:NRR
PWen AJKugler BKGrimes 05/ /94 05/ /94 05/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: I*See previous TECHED MMeJac*04/18/94 C/EELB:DE:NRF
CBerlinger
05/ /94 concurrence
MAGNE3AT.GE
IN 94-XX May XX, 1994 Normal prop wipe can be confirmed
with the breaker in its cubicle and closed (in test position if necessary)
in most installations
by visual inspection (using an inspection
mirror and light) without having to get too close to energized
components
or hazardous
mechanism
parts if the switchgear
cabinet can be opened with appropriate
safety precautions.
Pending issuance of a serv' advice letter (SAL) by the manufacturer
on this problem or a safety communic ion by GE NE, Attachment
2 illustrates
an inspection
hole in the right side the mechanism
frame through which the prop and prop pin position may be viewed. hile the fully forward prop position (to the stop) is the desired condition
aximum wipe), the absence of failures to latch along with consistent
and grea than minimum allowed prop wipe is, according
to GE, indicative
of continue reliable latching.
However, because minimum prop wipe is not a published
desig specification, and because certain other factors (e.g., opening spring adjus ent) may influence
latching reliability, GE has requested
that any licensee e eriencing
Magne-Blast
breaker latching problems or noticing changed, inconsiste
or apparently
abnormally
low prop wipe, particularly
following
overhaul o repair including
prop bushing replacement, contact GE NE PDS at 215-992-6049.
Pending installation
of a secon rop spring in affected breakers, Maine Yankee has shifted to the extent possibe, its available
dual prop spring breakers to locations
where operability
quires assured latching reliability
for closure or reclosure
during a design-b is event. For the remaining potentially
affected breakers, Maine Yankee planning expedited
inspections
with the assistance
of GE NE PDS to aid in it operability
determinations.
NRC Information
Notice 94-XX, issued May XX, 19 , discusses
other recently identified
problems impacting
Magne-Blast
operab ity, related to defective and improperly
installed
GE CR2940 limit switches.This information
notice requires no specific ac ion or written response.If you have any questions
about the information
in th notice, please contact one of the technical
contacts listed below or the appro late Office of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKGRIMES Brian K. Grimes, Directo Division of Operating
Reac or Support Office of Nuclear Reactor Regulation
Technical
contacts:
Stephen Alexander, NRR Kamalakar
Naidu, NRR (301) 504-2995 (301) 504-2980 Attachments:
1. Details of Failure Mode and Contributing
Factors 2. Magne-Blast
Prop Mechanism
Diagram 3. List of Recently Issued NRC Information
Notices VIB:DRIL VIB:DRIL SC V :DRIL TECHED S~lexanderl'J
K &aicu , G & S1na MMejac*05/(9/94 04/ W 94* O'5/94 04/18/94 C VIB:DRIL:NRR
D/DRIL:NRR
EELB:DE:NRR
CIEELB:DE:NRR
Lgrrholm CERossi SMitra Caerlinger
05/ /94 05/ /94 05/ /94 05/ /94 OGCB:DORS:NRR
AC/OGCB:DORS:NRR
D/:DORS:NRR
PWen AJKugler BKGrimes 05/ /94 05/ /94 05/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNE3AT.GE
<&c rfmtC'al Cak"vyc.t
IN 94-XX April XX, 1994 Prop wipe can be etermined
in most installations
by visual inspection
without having to get too lose to hazardous
mechanism
parts if the switchgear
cabinet door can be opened fely. Pending issuance of a SAL by the manufacturer
on this problem (and/or Service Information
Letter by GE NE), Attachment
2 illustrates
one locatlo where the prop position may be seen. While fully forward prop position (t the stop) is the desired condition (maximum wipe), the absence of failures to latch along with consistent
and greater than minimum allowed prop wipe is according
to GE, indicative
of continued reliable latching.
However, cause minimum prop wipe is not a published design specification, and becau certain other factors (e.g. opening spring adjustment)
may influence
latchin reliability, GE has requested
that any licensee experiencing
Magne-Blast
eaker latching problems or noticing changed, inconsistent
or what appear to be abnormally
low prop wipe, parti-cularly following
prop bushing replacemnt, contact GE NE PDS at 215-992-6049.
In the meantime, pending installat
n of a second prop spring in its affected breakers, Maine Yankee has shift to the extent possible, its available
dual prop spring breakers to loca Ions where operability
requires assured latching reliability
for closure or closure during a design basis event. For the remaining
suspect breakers, Mane Yankee has undertaken
expedited
inspections
with the assistance
of G E PDS to aid in its operabil-ity determinations.
NRC Information
Notice 94-X issued April XX, 1994, dis-cusses other recently identified
problems impactin Magne-Blast
operability, related to defective
and improperly
installed
GE CR 940 limit switches.This information
notice requires no specific ac on or written response.If you have any questions
about the information
in thi notice, please contact the technical
contacts listed below or the appropriate
ffice of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKGRIMES Brian K. Grimes, Directo Division of Operating
Reac or Support Office of Nuclear Reactor R ulation Technical
contacts:
Stephen Alexander, NRR (301) 504-2995 Kamalakar
Naidu, NRR (301) 504-2980 Attachments:
1. Details of Failure Mode and Contributing
Factors 2. Magne-Blast
Prop Mechanism
Diagram 3. List of Recently Issued NRC Information
Notices VIB:DRIL VIB:DRIL SC/VIB:DRIL
TECHED Salexander
Knaidu Gcwalina 41./V (,AA-04/ /94 04/ /94 04/ /94 04/AR/94 C/VIB:DRIL:NRR
D/DRIL:NRR
EELB:DE:NRR
C/EELB:DE:NRR
Lnorrholm
CERossi SMitra Cberlinger
04/ /94 04/ /94 04/ /94 04/ /94 OGCB:DORS:NRR
AC/OGCB:DORS:NRR
D/:DORS:NRR
PWen AJKugler BKGrimes 04/ /94 04/ /94 04/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNBLST.IN
IN 94-XX April XX, 1994 Prop wipe can be termined in most installations
by visual inspection
without having to get too c eto hazardous
mechanism
parts if the switchgear
cabinet door can be opened sa ly. Pending issuance of a SAL by the manufacturer
on this problem (and/or a rvice Information
Letter by GE NE), Attachment
2 illustrates
one location ere the prop position may be seen. While fully forward prop position (to t stop) is the desired condition (maximum wipe), the absence of failures to lat h along with consistent
and greater than minimum allowed prop wipe is, a cording to GE, indicative
of continued reliable latching.
However, bec se minimum prop wipe is not a published design specification, and because ertain other factors (e.g. opening spring adjustment)
may influence
latching eliability, GE has requested
that any licensee experiencing
Magne-Blast
breker latching problems or noticing changed, inconsistent
or what appears o be abnormally
low prop wipe, parti-cularly following
prop bushing replacem t, contact GE NE PDS at 215-992-6049.
In the meantime, pending installatlo
of a second prop spring in its affected breakers, Maine Yankee has shifte to the extent possible, its available
dual prop spring breakers to loca ions where operability
requires assured latching reliability
for closure or eclosure during a design basis event. For the remaining
suspect breakers, M ne Yankee has undertaken
expedited
inspections
with the assistance
of G NE PDS to aid in its operabil-ity determinations.
NRC Information
Notice 94- , issued April XX, 1994, dis-cusses other recently identified
problems impact g Magne-Blast
operability, related to defective
and improperly
installed
GE R2940 limit switches.This information
notice requires no specific ction or written response.If you have any questions
about the information
in \this notice, please contact the technical
contacts listed below or the appropri te Office of Nuclear Reactor Regulation (NRR) project manager.ORIG /S/'D BY BKG IMES Brian K. Grimes, irector Division of Operat ng Reactor Support Office of Nuclear Reactor Regulation
Technical
contacts: Stephen Alexander, NRR (301) 504-2995 Kamalakar
Naidu, NRR (301) 504-2980 Attachments:
1. Details of Failure Mode and Contributing
Factors 2. Magne-Blast
Prop Mechanism
Diagram 3. List of Recently Issued_ RC Information
Notices VIB:DRIL VIB:DRI SC/VIB:DRIL
Salexand 9k Knaidu Gcwalina 04//5'/94
04/14/94 s '4, 04/ /94 C/VIB:DRIL:NRR
D/DRIL:NRR
EELB:DE:NRR
Lnorrholm
CERossi SMitra 04/ /94 04/ /94 04/ /94 OGCB:DORS:NRR
AC/OGCB:DORS:NRR
D/:DORS:NRR
PWen AJKugler BKGrimes 04/ /94 04/ /94 04/ /94 TECHED 04/ /94 C/EELB:DE:NRR
Cberlinger
04/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNBLST.IN