Home > NRC Library > Document Collections > General Communications > Information Notices > 1981 > IN 81-01
SSINS No.: 6835 Accession No.: 8011040254 IN 81-01 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C. 20555 January 16, 1981 Information Notice No. 81-01: POSSIBLE FAILURES OF GENERAL ELECTRIC TYPE HFA RELAYS Purpose: The intent of this Information Notice is to alert licensees and holders of construction permits of a potentially generic problem involving defective coil spools used in General Electric (GE) type HFA relays. Such defective relays were recently found at Turkey Point Unit 4 (Docket No. 50-250). Description of Circumstances: The defective coil spools are fabricated of either black or clear Lexan, a polycarbonate material that is susceptible to surface cracking when exposed to hydrocarbons. The concern here is that such surface cracks could ultimately deteriorate to such a degree that relay actuation would be blocked by the resultant debris, thereby inhibiting a required safety function. Indications of the above mentioned cracks were recently detected on the HFA relays used to sequence the emergency loads on the diesel generators at Turkey Point Unit 4 upon a loss-of-coolant accident coincident with a loss of offsite power. After detecting the cracks, the spare coils in the storeroom were inspected and, although these coils are new units, one was found to be cracked. The possible failures of GE type HFA relays highlights two salient points: (1) HFA relays have had a long history of failures (e.g., GE has issued several Service Information Letters (SIL) addressing these relays, the oldest one of which dates back to 1973, and it is anticipated that GE will issue a new SIL in the near future addressing this new concern); (2) the cracking phenomena seems to be similar to that experienced on the cam followers used on GE type SBM switches (e.g., these cam followers are fabricated of Lexan, and after their exposure to hydrocarbons during fabrication or during maintenance severe cracking resulted. See Information Notice No. 80-13 for additional details.) The above information identifies means whereby the integrity of a major safety-related system can be jeopardized or compromised by the blocking of relay actuation. Accordingly, this Information Notice is provided as an early notification of a possibly significant matter that is still under review by the NRC staff. Recipients should, therefore, review the information for possible applicability to their facilities. Although no specific action or response is requested at this time, further licensee actions may be requested or required pending the outcome of the NRC staff evaluation. If you have any question regarding this matter, please contact the director of the appropriate NRC Regional Office.
Page Last Reviewed/Updated Thursday, March 29, 2012