United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 82-13: Failures of General Electric Type HFA Relays

                                                            SSINS No.: 6835 
                                                            IN 82-13 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555 

                                May 10, 1982 

Information Notice No. 82-13:   FAILURES OF GENERAL ELECTRIC TYPE HFA 
                                   RELAYS  

Addressees:  

All holders of a nuclear power reactor operating license (OL) or 
construction permit (CP). 

Purpose:  

This inforation notice is provided as an early notification of a potentially 
significant problem pertaining to General Electric type HFA relays with 
LEXAN or NYLON coil spools in safety related systems. It is expected that 
addressees will review the information for applicability to their 
facilities. No specific action or response is required at this time. 

Description of Circumstances: 

NRC IE Inforation Notice 81-01, dated January 16, 1981, alerted licensees 
and holders of construction permits of LEXAN coil spool surface cracking. 
General Electric Service Inforation tetter (SIL) No. 44 Supplement 2 dated 
February 1981 directed to all boiling water reactor (BWR) owners and General 
Electric Service Advice PSM 152.1 dated April 28, 1976 directed to all 
General Electric ,(GE) customers advised them of the coil cracking problem 
and recommended replacing cracked LEXAN and NYLON coil spools with new 
Century Series "TEFZEL" coil spools or replacement of the entire relay with 
a HFA Century Series relay. 

Recently, in addition to the previously identified cracking problem, there 
have been several instances of melting of LEXAN and NYLON coil spool 
material. The licensee reports listed below are some reported instances, of 
melting in HFA relays: 

1.   Monticello - Northern States Power Company reported on November 6, 1981
     that during cold shutdown, a GE type 12HFA 51A49F relay pertaining to 
     primary containment isolation system logic circuit failed to  open when
     deenergized. 

     Follow-up investigation indicated that partial melting of the NYLON 
     coil spool prevented the relay from moving to the deenergized position 
     for several minutes after the coil was deenergized. Several switches in 
     series with the relay coil circuit were burned-out and had to be 
     replaced. 

2.   Millstone 1 - Northeast Nuclear Energy Company reported on February 24,
     1982 that during a routine surveillance one GE type HFA relay 
     associated with the containment isolation logic circuit stayed in the 
     energized position when deenergized. As discussed below, melted LEXAN 
     material 

8202040146  
.

                                                           IN 82-13 
                                                           May 10, 1982  
                                                           Page 2 of 3 

     was found to be the cause. The relay deenergizes to cause main steam 
     isolation valve closure on main steam ine high radiation. The logic 
     requires one of two channels in each of two trip systems to deenergize 
     and cause the isolation. The other three channels were operable, 
     therefore, an actual high main streamline radiation level would have 
     resulted in valve closure. 

3.   Brunswick 2 - Carolina Power & Light Company reported on February 4, 
     1982 that during the functional performance test of the primary 
     containment isolation system main streamline high flow channel it was 
     discovered that the main streamline high-flow channel "C" logic would 
     not actuate. The details of this failure are somewhat different than 
     the failures observed at Monticello and Millstone 1. In Brunswick 2, 
     the armature apparently did move to the deenergized position. However, 
     melted insulation from the relay coil of the actuation relay GE Model 
     12HFA 5lA49F had coated the relay contacts, preventing electrical 
     contact. Like the Millstone 1 event, the remaining main streamline high 
     flow channels "A", "B" and "D" were operable and would have initiated 
     isolation upon an actual high flow condition. 

During earlier surveillance and coil replacement programs, testing did not 
identify a failure in the mechanism which would prevent the relay contacts 
from opening. Subsequent evaluation of the Millstone l relay by GE Power 
Systems Management Business Department in Philadelphia, led to the following
analysis: A piece of the spool flange fell into the gap between the open 
armature and pole face. When the relay was energized the armature attempted 
to close but was prevented from sealing against the pole face due to the 
piece of spool flange in the air gap. At this point, the contacts could have
been just touching. This created a fixed air gap in the magnetic circuit. 
The increase in the current caused by an air gap produced an excessive 
temperature rise in the coil. This excessive temperature rise, thru 
conduction and convection to the armature assembly and shading ring and 
eventually the piece of spool flange caused the loose piece of spool flange 
and remaining spool flange to soften, melt and move. As the piece of spool 
flange in the gap melted, the air gap closed permitting the normally open 
contacts to fully close. In addition, the closure of the gap reduced the 
current to normal. This reduction in current caused a lower temperature and 
melted LEXAN then hardened and created a bond between the armature and the 
pole face. Thus, when the coil was deenergized the return spring force was 
not enough to break this bond. Subsequent testing of the coil shows that the
coil is in normal operating condition (no shorted turns). 

Although the examples cited above relate to BWRs, the. GE type HFA relays 
are also commonly used in the safety system logic circuits of pressurized 
water reactors (PWRs). The above information identifies means whereby the 
function of a major safety-related system can be jeopardized or compromised 
by relay malfunctions. 

GE has notified its BWR and PWR customers of its findings and has reiterated
the need for periodic visual inspections. In addition, GE has also amplified
its earlier recommendations. In the event that cracked spools or evidence of
overheating is observed, GE recommends that either the entire  
.

                                                           IN 82-13  
                                                           May 10, 1982  
                                                           Page 3 of 3 

relay be replaced with a HFA Century Series relay or that the LEXAN or NYLON
1 coil spool be replaced with Century Series TEFZEL coil spools. 

If you have any questions regarding this matter, please contact the Regional
Administrator of the appropriate NRC Regional Office, or this office. 

                                   Sincerely, 


                                   Edward L. Jordan, Director 
                                   Division of Engineering and  
                                     Quality Assurance 
                                   Office of Inspection and Enforcement 

Technical Contact:  W. Laudan 
                    301-492-4766 

Attachment: 
Recently Issued IE Information Notices 

Page Last Reviewed/Updated Tuesday, November 12, 2013