United States Nuclear Regulatory Commission - Protecting People and the Environment

Morning Report for September 29, 1999

                       Headquarters Daily Report

                         SEPTEMBER 29, 1999

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                    REPORT             NEGATIVE            NO INPUT
                    ATTACHED           INPUT RECEIVED      RECEIVED

HEADQUARTERS        X
REGION I                               X
REGION II                              X
REGION III                             X
REGION IV                              X
PRIORITY ATTENTION REQUIRED  MORNING REPORT - HEADQUARTERS SEP. 29, 1999

MR Number: H-99-0087

                           NRR DAILY REPORT ITEM
                           GENERIC COMMUNICATIONS



Subject: Part 21 - Update on contact output isolator relays

VENDOR: Foxboro                     PT21 FILE NO: 99-35-0, 99-29-0

DATES OF DOCUMENTS: 07/09/99        ACCESSION NUMBER:
                    09/03/99
                    09/13/99

SOURCE DOCUMENT:    EN 35906        REVIEWER: REXB, V. Hodge
                    EN 36122
                    EN 36122 update

On July 9, September 3, and September 13, 1999, the vendor, Foxboro,
reported several potential defects in relays contained in contact output
isolator cards.

The July 9, 1999, report involved the cards, described below, using
relays manufactured by Potter & Brumfield [MR H-99-0078]. The tin-plated
contact support arms could develop leakage paths between adjacent
metallic surfaces because of growth of tin whiskers. In telephone
discussions, Foxboro provided additional information.

Between December 1, 1981, and December 31, 1993, Potter & Brumfield
manufactured these relays with pure tin plated contact support arms
instead of wetted tin plated contact arms. During the service life, in a
low voltage, low current application, whisker-type growth was observed in
the region of the contact plates. The whisker-type growth could result in
the inadvertent failure of the relays. Potter & Brumfield discontinued
manufacturing these relays after 1993.

Foxboro sent notification letters to its customers, referencing purchase
order number, sales order number, quantity, and contact output isolator
model number. Foxboro stated that it would provide replacement relays for
units manufactured during the affected period.

The September 3, 1999, report involved these same cards but using relays
manufactured by Communications Instruments [MR H-99-0080]. Repair
residual material on the contact armature plate could result in relay
failure. In telephone discussions, Foxboro provided additional
information.

The relays were to be assembled using non-adhesive Mylar insulation held
in place by rivets. During the initial assembly, this insulation was
inadvertently torn away from the rivets. During rework of the relays, the
torn-away insulation was replaced with a piece of adhesive- based Mylar
insulation. Foxboro later found that the adhesive migrated from the Mylar
to the upper coil region of the relay, captured, and held the relay
contacts in the energized condition even after the coil was deenergized.


HEADQUARTERS      MORNING REPORT     PAGE  2          SEP. 29, 1999
MR Number: H-99-0087 (cont.)

On September 13, 1999, Foxboro updated the September 3, 1999, report.
Concerning this problem with adhesive Mylar insulation, Foxboro
determined that affected relays display a manufacturer's date code in the
range 9806 to 9933.

An additional problem was found involving these same cards using the same
Communications Instruments relays. In an affected relay, poor solder
joint connections may exist between external pins 5 and 6 and the
internal copper base-plate. Foxboro determined that affected relays
display a manufacturer's date code in the range 9801 to 9936.

Foxboro sent notification letters to its customers, referencing purchase
order number, sales order number, quantity, and contact output isolator
model number. Foxboro stated that it would provide replacement relays for
units manufactured during the periods affected.

The affected relays are described as follows:

Foxboro Designation                         NO152CK
Potter & Brumfield Designation              R10-T0154-3
Communications Instruments Designation      41JO-500G-BSL
Action                                      single-pole, double-throw
Installation                                N-A0-L2C-R contact output
                                            isolator card

Foxboro Designation                         CO147SS
Potter & Brumfield Designation              R10-T0346-1
Communications Instruments Designation      42JO-500G-SIL
Action                                      double-pole, double-throw
Installation                                N-A0-L2C-R with Nuclear
                                            Engineering Change Existing
                                            Product (NECEP) 10273 contact
                                            output isolator card

Typical applications of these isolator cards include reactor protection
systems, reactor control systems, balance of plant systems such as main
condenser indication and feedwater control, and
anticipated-transient-without-scram systems.
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