Bulletin 84-02: Failures of General Electric Type HFA Relays in Use in Class 1E Safety Systems
SSINS No.: 6820
OMB No.: 3150-00012
Expiration Date: 4/30/85
IEB 84-02
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
February 3, 1984
IE BULLETIN NO. 84-02: FAILURES OF GENERAL ELECTRIC TYPE HFA RELAYS IN
USE IN CLASS 1E SAFETY SYSTEMS
Addressees:
All holders of nuclear power reactor operating licenses (OLs) or
construction permits (CPs) for action.
Purpose:
One purpose of this bulletin is to inform licensees and CP holders about
recent HFA relay failures that indicate they are similar in nature to
previous HFA relay failures reported in several General Electric (GE)
Service Advice Letters (SALs) and Service Information Letters (SILs) which
were issued to end-users in 1980 and 1982. (See Attachments to this
bulletin.) Another purpose of this bulletin is to ask licensees and CP
holders to inform the NRC about their plans, including schedules, for
implementing the manufacturer's recommendations discussed in the subject GE
letters. In addition, licensees are asked to provide information concerning
their plans to upgrade surveillance and to justify continued operation in
the interim.
Description of Circumstances:
During 1983, the NRC has received reports of several Class 1E relay failures
at the Duane Arnold, Pilgrim, and Hatch nuclear power reactor plants. The
subject relays are identified as GE type HFA 51 Series AC, using Lexan as
the coil spool material. These latest failures indicate that this model HFA
relay is still being used in safety-related systems at most boiling water
reactors (BWRs) and pressurized water reactors, including the reactor
protection systems at BWR nuclear power plants.
The recently reported relay failures all involved relays that were
continuously energized in ac circuits and failed to open when de-energized.
GE states the cause of failure of continuously energized HFA ac excited
relay applications is the deterioration of the coil wire insulation as a
result of the effects of aging. Failure mechanism begins with wire
insulation failure resulting in shorted turns, causing increased coil
temperature and eventual coil failure.
8402090031
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IEB 84-02
March 12, 1984
Page 2 of 6
In the event of failure, coil temperature can reach a level which can
vaporize the insulating materials and can melt the coil spool. These
materials may deposit on cooler surfaces of the relay and cause armature
damage and/or fail to make a contact circuit.
Approximately 25 failures of normally energized safety-related HFA relays
have been reported to the NRC in the past 2-1/2 years, six of these have
occurred since August 1983. GE believes that these recent failures are the
result of the above-mentioned end-of-life situation. According to GE, some
commercial ac rated HFA relays (predating the Century Series available since
1978) manufactured with standard Class A insulation (nylon or Lexan coil
spools and standard temperature wire) which are continuously energized can
fail in approximately 10-12 years. Many of the licensed facilities are now
approaching this time period, thus increasing the likelihood of concurrent
failures. This potential for concurrent failure may be considered a
precursor of ATWS (anticipated transient without scram), since concurrent
failure of certain safety-related relays at nuclear power plants could
result in failure of the reactor trip function.
Background:
Failures of HFA relays have been reported to the NRC since 1973, and GE has
responded to these failures by issuing SALs from the Power Systems
Management Department located in Philadelphia, Pennsylvania, and/or SILs
from its Nuclear Energy Products Division located in San Jose, California.
These GE letters discuss the relay failures and recommend replacing subject
relays with relays considered more suitable. Additionally, the NRC has
issued IE Bulletin 76-02 and Information Notices 81-01 and 82-13 referencing
these GE letters. Licensees began replacing HFA relays in 1976 in response
to IE Bulletin 76-02. IE Bulletin 76-02 referenced GE SAL 152.1 which
recommended replacing relay coils. At that time, the relay coil of the HFA
relay was wound on nylon spools. Winding failures occurred because of a
moisture/halogens problem and affected mostly dc-excited normally
de-energized relays. GE recommended replacing the nylon coil spool with one
made of Lexan material. Subsequently the Lexan coils exhibited extensive
cracking, which is considered a major precursor to the current HFA relay
failures.
To resolve the Lexan spool cracking problem, GE Philadelphia issued SAL
152.2 in 1980 recommending that end-users replace the Lexan spool-type HFA
relay with their new "Century Series" HFA relay. The Century Series relay
uses a high-temperature-rated plastic material called "Tefzel" for coil
spool construction and high-temperature coil wire, and employs a
vacuum-impregnated insulation. According to GE this relay has been both
environmentally and seismically qualified to the latest applicable IEEE
standards and has been subjected to an accelerated life test which verified
a continuously energized relay life in excess of 40 years.
In addition to SAL 152.2, other documents which recommended that end-users
replace the relays having a Lexan coil spool with the newer Century Series
HFA relay are: GE SAL 152.2A, 1982; SIL No. 44, Supplements 2 and 4, 1981
and 1982, respectively; and NRC documents IN 81-01 and IN 82-13 issued in
1981 and
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IN 84-02
March 12, 1984
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1982, respectively. It should be noted that the SILs from GE (San Jose)
offered an alternative to replace the existing coil spools with the Century
Series Tefzel coil spool only, not the complete relay unit. The NRC believes
that these two methods of replacement are equivalent.
Additionally, since past relay failures appear to be more predominant in
normally energized ac circuits, it is suggested that affected licensees
develop plans with replacement schedules which ensure that these types of
applications are the first to be replaced with either the complete Century
Series HFA relay or the Century Series Tefzel coil spools or equivalent.
Copies of the above-mentioned GE SALs and SILs are attached for your
information and use. The NRC IEB 76-02, IN 81-01, and IN 82-13 can be
obtained from your local public document room.
Actions for All Holders of Operating Licenses or Construction Permits:
Since GE asserts that the new Century Series HFA relay has been successfully
tested to the environmental and seismic requirements specified in
IEEE-323-1974 and IEEE-344-1975 Standards, this relay, or one of equal
qualification, may be an acceptable replacement for Lexan/Nylon HFA relay
now in service at many nuclear power plants. However, the licensee is
responsible for determining that all safety grade equipment in the plant,
including relays, is qualified for its intended service. That is, the
licensee must establish and document that the service life and reliability
of the relay is acceptable, and that the relays have been qualified for the
environmental and seismic conditions that this equipment may encounter at
its installed location in the plant.
1. Plants in Operation
a. Develop plans and schedules for replacing (1) nylon or Lexan coil
spool-type HFA relays used in normally energized safety-related *
applications and (2) nylon coil spool-type HFA relays used in
normally de-energized safety-related applications. The
replacement relays and any replacements made in the future should
meet the requirements of the applicable IEEE standards. The
replacement program for energized and de-energized relays should
be performed on a "best efforts" basis during plant outages of
sufficient duration. The entire replacement program should be
completed within two years from the date of this bulletin.
* For the purpose of the applicable actions of this bulletin,
"safety-related" constitutes those systems covered by the definition
given in 10 CFR Part 100, Appendix A Sections III.(c)(1), III.(c)(2),
and III.(c)(3). In assessing the impact of Lexan/Nylon coil spool-type
HFA relay in other systems at their facilities, licensees should
consider the provisions of GDC 1 to 10 CFR Part 50, Appendix A.
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IEB 84-02
March 12, 1984
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The replacement schedule should consider the following recommended
priority:
Nylon or Lexan normally energized in the reactor trip system
Nylon or Lexan normally energized in other safety-related applications
Nylon normally de-energized in the reactor trip system
Nylon normally de-energized in other safety-related applications
b. During the period before relay replacement, develop and implement
surveillance plans that include:
(1) Monthly functional tests of all reactor trip system normally
energized relays that verify relay contacts change state
when the relay coil is de-energized;
(2) Visual inspections of all safety-related normally energized
relays as soon as practical upon receipt of this bulletin.
Thereafter, similar inspections should be accomplished in
conjunction with the monthly functional test. These visual
inspections should verify that relay coils are not
deteriorating (e.g., inspect coil bobbins for visible cracks
or melting), and should confirm cleanliness of the relay
pole pieces.
c. Provide a basis for continuing operation for the period of time
until the normally energized relays are replaced. This basis
should include a discussion of those measures addressed in Items
1a and 1b and any other preventive and/or corrective measures
taken or planned.
d. Provide a written report of the above actions, including
schedules for completion. This report is to be submitted to the
NRC within 120 days of receipt of this bulletin.
2. Plants Under Construction
a. Provide plans and schedules for replacing both normally energized
and normally de-energized HFA relays as specified by this
bulletin in item 1a which are used in safety-related systems at
your facility(ies). Your schedule shall ensure that these relays
are replaced before the scheduled date for OL issuance or within
two years from the date of this bulletin, whichever is longer. If
these relays are not planned to be replaced before OL issuance,
item 1b shall be implemented at the time of license issuance and
a response to item 1c is required.
b. Provide a written report of the actions specified in Item 2a.
This report is to be submitted to the NRC within 120 days of
receipt of this bulletin.
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March 12, 1984
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3. If your plant does not use or plan to use the nylon or Lexan-type GE
HFA relays in the safety-related systems discussed above, a negative
response is requested within 120 days of receipt of this bulletin, and
no further action is required.
4. If your plant uses or plans to continue to use the nylon or Lexan-type
HFA relay in systems other than those safety-related applications
defined in this bulletin, then the appropriate administrative controls
dealing with maintenance, storage, and handling of spare parts at your
facility must be revised to ensure that the older and problematic HFA
relay coils are not inadvertently used as a replacement part in
safety-related applications in future maintenance efforts at your
facility(ies).
Although the specific details involving the identified relay failures
described above may not directly apply to your facility(ies), you are asked
to review the general concerns expressed in the bulletin for applicability
at your facility(ies). For example, if a different type of relay is used for
the same safety functions described in this bulletin, or relays with similar
materials are used for other safety-related functions, past operating
history and the manufacturer's recommendations should be reviewed to
determine if additional action is appropriate. Your response should describe
the results of the review, and, if the general concerns apply, you should
describe the short-term and long-term corrective actions to be taken and the
schedules thereof.
The written report required shall be submitted to the appropriate Regional
Administrator under oath or affirmation under provisions of Section 182a,
Atomic Energy Act of 1954, as amended. Also, the original copy of the cover
letters and a copy of the reports shall be transmitted to the U.S. Nuclear
Regulatory Commission, Document Control Desk, Washington, DC 20555 for
reproduction and distribution.
This request for information was approved by the Office of Management and
Budget under a blanket clearance number 3150-0011 which expires April 30,
1985. Comments on burden and duplication may be directed to the Office of
Management and Budget, Reports Management, Room 3208, New Executive Office
Building, Washington, DC 20503.
Although no specific request or requirement is intended, the following
information would be helpful to the NRC in evaluating the cost of this
bulletin:
1. Staff time to perform requested review.
2. Staff time spent to prepare requested documentation.
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IEB 84-02
March 12, 1984
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If you have any questions regarding this matter, please contact the Regional
Administrator of the appropriate NRC Regional Office or the technical
contact listed below.
Richard C. DeYoung, Director
Office of Inspection and Enforcement
Technical Contact: V. D. Thomas, IE
301-492-4755
Attachments:
1. GE SALs and SILs
2. List of Recently Issued IE Bulletins
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