Bulletin 88-03: Inadequate Latch Engagement in HFA Type Latching Relays Manufactured by General Electric (GE) Company

                                                       OMB No.: 31500011 
                                                       NRCB 88-03

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                      OFFICE OF NUCLEAR REACTOR REGULATION
                             WASHINGTON, D.C.  20555

                                 March 10, 1988


NRC BULLETIN NO. 88-03:  INADEQUATE LATCH ENGAGEMENT IN HFA TYPE
                         LATCHING RELAYS MANUFACTURED BY GENERAL
                         ELECTRIC (GE) COMPANY 


Addressees: 

All holders of operating licenses or construction permits for nuclear power 
reactors. 

Purpose: 

The purpose of this bulletin is to request that licensees perform inspections 
to ensure that all GE latching-type HFA relays installed in Class 1E (safety-
related) applications have adequate latch engagement and that those relays 
which fail to meet acceptance criteria be repaired or replaced. 

Description of Circumstances: 

GE Meter and Control Business Department (MCBD) investigated a report dated 
October 7, 1987 from their Nuclear Energy Business Operation that certain 
latch-type relays supplied by GE with Certificates of Conformance, qualifying 
them to the requirements of IEEE-323, "IEEE Standard for Qualifying Class 1E 
Equipment for Nuclear Power Generating Stations," which includes IEEE-344, 
"IEEE Recommended Practices for Seismic Qualification of Class 1E Equipment 
for Nuclear Power Generating Stations," were malfunctioning.  MCBD informed 
the NRC of this problem in accordance with 10 CFR Part 21 on November 12, 1987 
(attached) and sent a letter dated November 16, 1987 to all purchasers of HFA 
151B, 154B, and 154E type latching relays who had specified Class 1E or 
equivalent on their purchase order.  Although GE reported that they have 
informed all their customers who purchased the relays as Class 1E components, 
there may be "Other Equipment Manufacturers" who purchased these relays as 
commercial grade components and then installed them in panels and certified 
them as Class 1E components on the basis of analysis.  GE MCBD has halted 
production of these relays pending resolution of this problem. 

The NRC believes that the operability of all HFA 151B, HFA 154B and HFA 154E 
relays with a manufacturing date code prior to November, 1987 has been brought 
into question and therefore the relays should be inspected.  Also, the 
following 





8803040062
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additional latching-type HFA relays which were not qualified to IEEE-323 by 
GE, but which may have been qualified and used by "Other Equipment 
Manufacturers" in Class 1E, (safety-related) applications may also be suspect: 

          Non-Century Series                      Century Series

          Types HFA 54                            HFA 154

                HFA 74                            HFA 174

                HFA 51B                           HFA 151B

                HFA 71B                           HFA 171B

In GE latching-type HFA relays, when the coil is energized, the armature 
operates a latch which locks in the change in the state of the contacts and 
holds them in that state once the relay is de-energized until such time that 
the relay is mechanically or electrically reset.  GE MCBD determined that when 
the relay is energized, with the armature in the latched position, each leg of 
the U-shaped latch should engage the top of the armature by the required 
minimum of 1/32 inch.  With less than 1/32 inch latch engagement, it is possi-
ble that the relay could unlatch prematurely.  GE MCBD concluded that two 
circumstances can cause latch engagement to be less than 1/32 inch:  
(1) Insufficient clearance between the top of the relay armature and the top 
of the moving contact carrier and, (2) Insufficient tension provided by the 
formed leaf spring that rotates the latch to its fully engaged position, which 
may permit the spring to relax before full engagement between the latch and 
the armature is achieved. 

Actions Requested: 

Addressees should complete the actions described below for all latching-type 
HFA relays in Class 1E (safety-related) applications no later than restart 
following the next refueling outage scheduled to begin 30 days or more from 
receipt of this bulletin.  

1)   In accordance with the GE recommendation contained in Attachment 1, 
     measure the distance between the top of the molded contact carrier and 
     the top of the relay armature.  This distance should be a minimum of 1/32 
     inch.

2)   In accordance with the GE recommendation contained in Attachment 1, with 
     the armature fully depressed against the pole piece, check to see if the 
     latch is fully rotated by pulling up on the latch assembly.  If the latch 
     is fully rotated, there should be no motion of the latch, since the latch 
     should be held against the armature by spring tension.

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                                                            March 10, 1988
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3)   Repair or replace any relay which fails the above inspections, such that 
     the relay satisfies the GE criteria. 

4)   Inspect all existing spare HFA relays as above.  Future spares received 
     should be inspected prior to their installation if manufactured prior to 
     November 1, 1987.  

Reporting Requirements:

Records of inspection and corrective actions in response to this bulletin 
shall be documented and maintained in accordance with plant procedures for 
Class 1E equipment.  Any addressee who does not have HFA type latching relays 
subject to this bulletin shall provide a letter to the NRC stating this fact 
within 120 days of receipt of this bulletin.  Addressees who do have HFA type 
latching relays subject to this bulletin including those who have previously 
responded to the GE SAL shall provide letters of confirmation of completion of 
the inspections.  These letters shall include the number of relays of each 
type inspected, the number of relays of each type requiring corrective actions 
due to item 1 under Actions Requested, and the number of relays of each type 
requiring corrective actions due to item 2 under Actions Requested.  These 
letters of confirmation shall be submitted to the NRC within 30 days of com-
pletion of the inspections.

The letter of confirmation shall be submitted to the appropriate Regional 
Administrator under oath or affirmation under the provisions of Section 182a, 
Atomic Energy Act of 1954, as amended, including the provisions of 10 CFR 
50.54(f).  In addition, the original copy of the cover letter and a copy of 
any attachment shall be transmitted to the U. S. Nuclear Regulatory 
Commission, Document Control Desk, Washington, D.C.  20555, for reproduction 
and distribution.

This request for information was approved by the Office of Management and 
Budget under blanket clearance number 31500011.  Comment on burden and 
duplication should be directed to the Office of Management and Budget, Reports
Management, Room 3208, New Executive Office Building, Washington, D.C., 20503.

Although no specific request or requirement is intended, the following 
information would be helpful to the NRC in evaluating the cost of implementing 
this bulletin: 

1.   Staff time to perform the requested inspections and corrective actions.

2.   Staff time to prepare the requested documentation.

3.   Additional cost incurred as a result of the inspection findings (e.g., 
     costs of corrective actions, costs of downtime).

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If you have any questions about this matter, please contact one of the techni-
cal contacts listed below or the Regional Administrator of the appropriate 
regional office. 




                              Charles E. Rossi, Director 
                              Division of Operational Events Assessment 
                              Office of Nuclear Reactor Regulation


Technical Contacts:  K. R. Naidu, NRR
                     (301) 492-9659

                     E. T. Baker, NRR
                     (301) 492-4783


Attachments:  
1.  GE letter dated November 12, 1987 
2.  List of Recently Issued NRC Bulletins