Information Notice 2003-18, General Electric Type Sbm Control Switches with Defective Cam Followers
| ML032520011 | |
| Person / Time | |
|---|---|
| Issue date: | 09/26/2003 |
| From: | Beckner W NRC/NRR/DIPM |
| To: | |
| References | |
| IN-03-018 | |
| Download: ML032520011 (10) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001 September 26, 2003 NRC INFORMATION NOTICE 2003-18: GENERAL ELECTRIC TYPE SBM CONTROL
SWITCHES WITH DEFECTIVE CAM
FOLLOWERS
Addressees
All holders of operating licenses for nuclear power reactors, except those who have
permanently ceased operations and have certified that fuel has been permanently removed
from the reactor vessel.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to inform
addressees of recent and long-term operational experience with control switches and relays
incorporating a polycarbonate plastic material manufactured by General Electric known as
Lexan. 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
On January 5, 2003, at Calvert Cliffs Unit 1, an emergency diesel generator (EDG) output
breaker failed to close on demand. The licensee found that a single block module (SBM) type
auxiliary switch on the General Electric (GE) Magne-Blast type breaker had a broken cam
follower. The cam follower consists of a steel pivot pin centered in clear Lexan. The pin had
sheared and fallen to the bottom of the switch. At the pin location, the Lexan was cracked
with some pieces missing. Because the cam follower was broken, contact 152/b in the closing
coil circuit failed open, preventing the completion of the logic permitting closure of the breaker.
The licensee inspected individual breaker components affected by this deficiency. Of the 24 breakers inspected, 5 had defective SBM switches. At Unit 1, the defective switches were on
the EDG output breaker discussed above and a service water pump breaker; at Unit 2, a
service water pump breaker, a high-pressure injection system breaker, and an EDG output
breaker. All these switches had noticeably cracked Lexan but were not in as bad a condition
as the switch on the Unit 1 EDG output breaker. The licensee replaced these switches with GE
Type SB-12 switches. Both SBM and SB-12 switches contain Lexan cam followers but the
SB-12 switch was fabricated with Lexan not exposed to hydrocarbons, a potential failure
mechanism discussed in Information Notice 80-13, "General Electric Type SBM Control
Switches with Defective Cam Followers.
Background
In 1976, GE recognized this problem (GE Service Information Letter [SIL] No. 155). The SIL
stated that the material used for the cam followers prior to July 1972 was an acetyl resin
composition called Delrin. Delrin is easily distinguishable by its milky opaque appearance
from the clear Lexan. The SIL recommends replacement of the SBM switches in safety
applications. GE replaced Lexan in these switches with Valox, which has a white opaque
appearance similar to Delrin.
No failures of SBM switches have been reported attributable to cam followers made of Delrin
or Valox. However, properties of these or related materials have been discussed in NRC
generic communications, as noted below.
The cause of the Lexan failures was believed to be exposure of the switches to hydrocarbon
chemicals during manufacture or maintenance. With respect to the manufacturing process, switches made between July 1972 and May 1975 were believed to be suspect. GE SIL No. 155 provided date codes to aid in the identification of suspect switches.
The Maine Yankee licensee had previously (in 1972) experienced failures of SBM switches
during maintenance when using contact cleaner and discontinued use of any type of contact
cleaner on SBM switches.
In 1976, GE supplemented SIL No. 155, adding a recommendation to inspect all SBM switches
that have polycarbonate cam followers and to replace those found to have severely cracked
cam followers.
In 1979, GE again supplemented SIL No. 155, reminding BWR operators of the need to inspect
the SBM switches according to Supplement 1 and discussing manufacturing changes made
since January 1976: discontinuing use of nonvirgin Lexan materials, discontinuing use of
hydrocarbons, and reducing stress during roll pin insertion.
In 1980, NRC issued Information Notice 80-13 to describe the SBM switch cam follower defects
found at Cooper and Diablo Canyon Unit 1. These switches are used broadly and thus
represent a potential common-mode failure affecting multiple safety-related systems. At
Cooper, SBM switches are used primarily as hand control switches in the control room. At
Diablo Canyon Unit 1, they provide auxiliary contacts in three switch applications on 4 kV and
12 kV Magne-Blast breakers: a breaker-mounted auxiliary switch, a cell-mounted auxiliary
switch, and a cell interlock switch. These defects were described as severe cracking with a
rock salt appearance that could ultimately progress to mechanical failure.
Additional, more recent operating experience may be cited. In 1998, the Perry licensee
mistakenly determined that IN 80-13 and SIL No. 155 did not apply to local control switches on
installed ABB HK breakers. The licensee committed to reevaluate the applicability and take
appropriate corrective action.
In 1996, the LaSalle licensee experienced problems while downshifting the recirculation pump.
The licensee failed to take appropriate corrective action for safety-related SBM switch
degradation concerns identified in 1979, 1990, and 1995. Also in 1996, the Turkey Point licensee observed that a 4 kV bus clearing relay failed to actuate
in test. An intake cooling water system pump motor breaker stationary switch failed to operate
its contacts as required. The licensee found a cracked internal cam follower on this switch.
The licensee also observed that all four 4 kV buses contained SBM switches but concluded that
all four 4KV buses were operable, characterizing the problem as an isolated random failure and
noting the manufacturers assessment that the switches would function 45,000 cycles with
existing cracks and the licensees plans to replace the switches at the next opportunity.
In 1995, the Maine Yankee licensee found three broken cam followers in SBM switches on
medium-voltage breakers. Two did not prevent switch function and the third affected only a
spare contact. The licensee did not identify a safety concern but did identify a need for more
effective communications with GE, including obtaining an index of all GE service letters to
evaluate against the affected components in the plant.
Also in 1995, the Pilgrim licensee encountered an SBM switch cam follower failure of the high- pressure coolant injection system suction valve from the torus. A similar failure occurred in
1992. The NRC cited the licensee for not promptly correcting the 1992 failure and noted that
the 1995 failure was corrected satisfactorily. Previous similar failures at this plant can be cited
as well: a core spray inboard injection valve in 1988, and a hydrogen analyzer sample flow line
in 1993.
In 1994, the Cooper licensee inspected 130 SBM switches and found cracking, opaqueness, and missing pieces of cam followers on 34 of them.
In 1992, the Fort Calhoun licensee experienced a failed switch for a raw water pump because
of a cracked cam follower. At the time, the licensee was replacing switches with open cracks or
missing pieces.
Discussion
Though failure of SBM switches because of cracked or broken cam followers was noted some
30 years ago, problems persist. Guidance on avoiding the problem is available.
Licensees have found SBM switches with degraded Lexan cam followers of the affected date
codes among their stored components in addition to those installed in the plant. In addition to
replacing the affected switches in service, licensees have determined that eliminating affected
switches, whether degraded or not, from the stored components effectively prevents inadvertent
use of such defective switches.
Other operating experience that differs from the above in one or more respects might
nevertheless apply to the general problem of degradation of plastic materials used in nuclear
power plants. Degradation of Delrin-related materials in applications different from control
switches is described in NRC Information Notices 83-45 and 92-85. Thermal properties of
Valox or related material are discussed in NRC Bulletin 78-01.
In 2003, NRC inspectors at the Surry plant learned of degradation of zippertubing, a plastic
product of Zippertubing Company, used to bundle electric cable inside the safety injection
cabinets at both Units 1 and 2. This product was qualified and delivered as part of the original equipment during plant construction. Zippertubing sold the product as ZIP-31 at that time, discontinued its manufacture 10-12 years ago, and now markets a similar product as ZIP-41.
The Surry licensee removed this covering. This operating experience relates to NRC
Information Notice 91-20 "Electrical Wire Insulation Degradation Caused Failure in a Safety- Related Motor Control Center.
In 2002, the San Onofre licensee reported degradation of contacts due to excessive use of
Inhibisol, a cleaning solvent based on trichloroethane (TCE). The cleaning solvent caused the
plastic housing for the contacts to break down. Over time, small amounts of the plastic came
loose and interfered with the contacts, resulting in linestarter degradation and the failure of
safety-related valves. The NRC issued Information Notice 2003-06, "Failure of Safety-Related
Linestarter Relays at San Onofre Nuclear Generating Station. Information Notice 93-76,
"Inadequate Control of Paint and Cleaners for Safety-Related Equipment, may also apply.
In 1995, the Browns Ferry licensee reported GE Type HFA 51 Series AC relay failures involving
shorting of coil wire insulation made of nylon or Lexan. After its review, the licensee replaced
308 such relays at Unit 3. The NRC issued Information Notice 81-01, "Possible Failures of
General Electric Type HFA Relays and Bulletin 84-02, "Failures of General Electric Type HFA
Relays in Use in Class 1E Safety Systems.
This information notice requires no specific action or written response. If you have any
questions about this notice, contact one of the persons listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
/RA/
William D. Beckner, Chief
Reactor Operations Branch
Division of Inspection Program Management
Office of Nuclear Reactor Regulation
Technical Contacts: Vernon Hodge, NRR Joe O'Hara, Region I
301-415-1861 410-495-4669 E-mail: cvh@nrc.gov E-mail: jmo@nrc.gov
Stephen Alexander, NRR
301-415-2995 E-mail: sda@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
ML032520011 *See previous concurrence
DOCUMENT NAME: C:\ORPCheckout\FileNET\ML032520011.wpd
OFFICE IROB:DIPM Tech Editor IEPM:DIPM RGN-I RGN-I
NAME CVHodge* PKleene* SAlexander* JOHara JTrapp
DATE 09/08/2003 08/29/2003 09/08/2003 09/15/2003 09/15/2003 OFFICE SC:IROB:DIPM BC:IROB:DIPM
NAME TReis WDBeckner
DATE 09/25/2003 09/26/2003 / /2003 / /2003 / /2003
Attachment 1 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
_____________________________________________________________________________________
2003-17 Reduced Service Life of 09/29/2003 All holders of operating licenses
Automatic Switch Company for nuclear power reactors.
(ASCO) Solenoid Valves With
Buna-N Material
2003-16 Icing Conditions Between Pending All 10 CFR Part 72 licensees and
Bottom of Dry Storage System certificate holders.
and Storage Pad
2003-15 Importance of Followup 09/05/2003 All holders of operating licenses
Activities in Resolving for nuclear power reactors except
Maintenance Issues those who have permanently
ceased operation and have
certified that fuel has been
permanently removed from the
reactor vessel.
2003-14 Potential Vulnerability of Plant 08/29/2003 All holders of operating licenses
Computer Network to Worm for nuclear power reactors, Infection except those who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel.
2003-13 Steam Generator Tube 08/28/2003 All holders of operating licenses
Degradation at Diablo Canyon for pressurized-water reactors
(PWRs), except those who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor.
Note: NRC generic communications may be received in electronic format shortly after they are
issued by subscribing to the NRC listserver as follows:
To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the following
command in the message portion:
subscribe gc-nrr firstname lastname
______________________________________________________________________________________
OL = Operating License
CP = Construction Permit