Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
January 16, 1978
IE Bulletin No. 78-01
FLAMMABLE CONTACT-ARM RETAINERS IN G.E. CR120A RELAYS
Description of Circumstances:
On April 18, 1977, a fire was discovered in a relay cabinet in the Peach
Bottom Unit 3 facility. The fire damaged eight relays, type CR120A,
manufactured by the General Electric Company. The fire was investigated by
the licensee, the Philadelphia Electric Company who concluded that it was
caused by an overheated relay coil that ignited the relay's plastic
contact-arm retainer. Subsequently, on July 29, 1977, fire damage was
discovered in a relay cabinet during surveillance testing in the Peach
Bottom Unit 2 facility. This fire damaged 18 G.E. type CR120A relays.
Discussion:
The investigation revealed that the relay's contact-arm retainer was made
from Celcon M90 Acetal Copolymer which is a flammable material. In June
1972, this material was changed to Valox 310-SED, which is self
extinguishing and flame resistant. Both materials are white and have the
same surface appearance. A G.E. Service Information Letter SIL-NO-229 (a
copy of the text is attached for information) indicates that there is no
generic overheating problem with this type relay. However, they. recommend
that BWR owners replace the contact-arm retainer of all relays (including
BOP applications) marked with manufacturers date code between E.D. (May
1968) and A.J. (January 1973) with the improved, self extinguishing flame
resistant contact arm retainers.
Action To Be Taken By Licensees And Permit Holders:
Licensees of power reactor facilities with an operating license and
construction permit holders shall take the following actions:
1. Determine if you have installed G.E. type CR120A relays in
safety-related equipment or in areas wherein fires have the potential
for damaging safety equipment. Also determine if you have such relays
in spares inventory or on order.
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IE Bulletin No. 78-01 January 16, 1978
2. Identify all of the relays that have Celcon contact-arm retainers.
3. For those relays which have Celcon retainers, develop a program for
their replacement with Valox retainers. The program should include:
a. Identification of the location of the relays
b. The schedule for the replacement of the Celcon retainers
c. The procedure that will be used to perform the replacement,
including the means that you will use to differentiate between the
Valox and Celcon retainers.
4. For facilities with an operating licensee a report of the above
actions, including the date(s) when they will be completed, shall be
submitted within 30 days of receipt of this Bulletin.
5. For facilities with a construction permit, a report of the above
actions, including the date(s) when they will be completed, shall be
submitted within 60 days of receipt of this Bulletin.
Reports should be submitted to the Director of the appropriate NRC Regional
Office. A copy of your report should be sent to the U.S. Nuclear Regulatory
Commission, Office of Inspection and Enforcement, Division of Reactor
Operations Inspection, Washington. D.C. 20655.
Approved by GAO, B-180225 (R0072); clearance expires 7-31-80. Approval was
given under a blanket clearance specifically for identified generic
problems.
Attachment:
Copy of Text of General
Electric Service
Instruction Letter
(SIL)-SIL-No. 229
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(COPY OF TEXT OF GE SIL-No. 229)
FWD. BY LTR MFN 373-77
8-10-77
IMPROVED CONTACT ARM RETAINERS FOR TYPE CR120A RELAYS
Recently, at an operating BWR a small electrical fire occurred in a relay
panel. The purpose of this Service Information Letter is to discuss this
occurrence and to recommend an improved contact arm retainer for certain
CR120A relays to help avoid or mitigate this type of occurrence.
DISCUSSION
In a relay panel at an operating BWR, one relay, Type CR120A, overheated,
subsequently ignited, and resulted in seven other similar relays in the
proximity being burned. No definite cause could be determined for the relay
overheating. Moreover, subsequent investigation concluded that there is no
generic overheating problem with relays of this type.
The investigation also noted that the contact arm retainers of these relays,
and of relays manufactured between May 1968 and June 1972, were made of
Celcon M90 acetal copolymer which is flammable. In June 1972 this material
was changed to Valoz 310-SEO which is self extinguishing and flame
resistant. .
RECOMMENDED ACTION
General Electric recommends that BWR owners replace the contact arm
retainers of all Type CR120A relays (including those in B.O.P. applications)
marked with a manufacturing date code between ED (May 1968) and AJ (January
1973) with the improved, self extinguishing flame resistant contact arm
retainers, as follows:
1. For four pole CR120A relays use replacement contact arm retainer Part
No. 55650378P3.
2. For two pole adder CR120A relays use replacement contact arm retainer
Part No. 55501383P3.
3. For two pole CR120A relays use replacement contact arm retainer Part
No. 55651401P3.
Attachment 1
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(Copy of Text of GE SIL-No. 229 - Continued)
BWR owners should survey CR120A relay applications throughout their plants,
in both the nuclear steam supply system (NSSS) and balance-of-plant (BOP),
to ascertain the total amount of contact am retainers required for each type
of relay. Upon notification of their requirements, NEDs' Spare and Renewal
Parts service will furnish BWR owners the requested amount of replacement
parts.
Contact your local General Electric service representative for additional
information and for assistance in obtaining the recommended replacement
parts.
(Copy) Attachment
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