United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9905110120

An EDISON INTERNATIONAL [Servicemark] Company

Dwight E. Nunn
Vice President

May 5, 1999

U. S. Nuclear Regulatory Commission

Attention: Document Control Desk
Washington, D.C. 20555


Subject: 10CFR Part 21 Notification - Potter & Brumfield Relays
San Onofre Nuclear Generating Station, Units 2 & 3

In accordance with 10CFR 21.21 (d)(3) and 21.21 (d)(4), the attachment to this letter reports a defect found in Potter and Brumfield (P&B) relays. Sixteen P&B relays, model KUP93-14A32-120, were supplied in lot "913501" by the vendor as commercial grade items and were dedicated for nuclear service at San Onofre Nuclear Generating Station by Southern California Edison (SCE). SCE's laboratory analyses of four of these relays determined the contact pads were insufficiently welded to their contact arms and could become detached. Based on a review of relay failure history, SCE has concluded the insufficient contact pad welding is limited to lot 913501.

SCE replaced these relays with new P&B relays which have contact pads that are riveted to their contact arm, thus precluding contact pad detachment.

My signature below satisfies the notification requirements of 10CFR21.21 (d)(4). If you require any additional information, please contact me or Mr. Ken Slagle at (949) 368-6631.


Attachment 1

cc: E. W. Merschoff, Regional Administrator, NRC Region IV
J. A. Sloan, NRC Resident Inspector, San Onofre Units 2 and 3
L. Raghavan, NRC Project Manager, San Onofre Units 2 and 3
Institute of Nuclear Power Operations (INPO)
P. O. Box 128
San Clemente, CA 92674-0128
Fax 949-368-1490

Attachment 1 10 CFR Part 21 Report on P&B Relays Page 1 of 2
A. Component Supplier
Potter & Brumfield (A Siemens Co.)
200 South Richland Creek Drive
Princeton, Indiana 47671
(812) 386-2211
B. Nature of defect:
On March 30, 1999, SCE opened the shipping box for new relays, P&B Model Number KUP93-14A32-120, and found one contact pad was detached from its contact arm in three relays. A review of relay failure history recognized that, in December of 1998, this same type of relay had failed after 3 years of service. A total of 16 relays from lot "91 3501 " were purchased from Potter & Brumfield as commercial grade items in 1991 and dedicated by SCE for safety related applications.
Each relay contains three contact arms with each having four contact pads for a total of twelve contact pads. One of the twelve contact pads was missing in the middle moving arm at the normally closed contact position in these four relays. Laboratory analysis determined that the contact pads were inadequately fused to the contact arms. Microscopic inspection found only a small weld area between the contact pad and its mating surface on the contact arm. This same condition also existed on the remaining contact pads, although they were still attached. Without a contact pad, there was no make-up connection to close on demand. Therefore, the cause of the defect was insufficient welding of the contact pads to the contact arm.
C. Date defect discovered:
SCE discovered this deviation on March 30, 1999, prior to replacement of the relays during preventative maintenance for auxiliary building emergency chiller. On April 29, 1999, SCE completed an evaluation and concluded this condition constitutes a defect of a basic component.

Attachment 1 10 CFR Part 21 Report on P&B Relays Page 2 of 2
D. Component location:
A total of 16 relays are installed in each train of auxiliary building emergency chillers, SA1513ME335 and ME336. Eleven of the 16 relays in each train are used for alarming functions only; the remaining 5 relays are used for control functions.
E. Corrective actions:
  • The installed relays from lot "913501" were replaced with new P&B relays containing contact pads which are riveted to their contact arms.
  • One of the new replacement relays was checked for contact pad-to-contact arm bond integrity. Microscopic inspection found that the new P&B relays have contact pads which are riveted to the contact arm instead of welded. This bonding method does not allow the contact pads to become disengaged from their contact arms.
  • This defect was determined to be specific to lot 913501 based on the following actions.
          1. A pull test to check contact bonding integrity was performed on six other relay lots. The contact pads could not be dislodged from their contact arms.
          2. One relay from lot "E9120" was also randomly selected for laboratory analysis. Microscopic inspection found that the contact pads had been firmly fused to the contact arms and could not be dislodged from their contact arms.
          3. A review of relay failure history indicated that no similar failures have occurred at San Onofre from P&B manufacturing lots other than lot 913501.
  • SCE will enhance the dedication plan for control relays to measure the contact resistance on all relay contacts.
F. Other pertinent information:
SCE has not supplied this type of component nor has knowledge of it's use at another facility. However, this type of component may have also been dedicated for nuclear use by another facility.

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