United States Nuclear Regulatory Commission - Protecting People and the Environment

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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                                                             March 12, 1984 
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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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                                                             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. 
.

                                                             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
Page Last Reviewed/Updated Tuesday, July 23, 2013