Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
April 18, 1988
Information Notice No. 88-14: POTENTIAL PROBLEMS WITH ELECTRICAL RELAYS
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is being provided to alert recipients to potential
problems involving HFA, PVD 21B, PVD 21D, and HGA relays manufactured by
General Electric Company (GE), as described below. Although some of these
problems are several years old, they are included because utilities are still
identifying problems discovered while implementing advice issued by GE in the
early 1980s. The specific problem with the HFA relays concerns mechanical
binding in the relay caused by incorrect location of a stop tab that is welded
to the armature. The problems with the PVD 21B, PVD 21D, and HGA concern
their seismic capability. It is expected that licensees will review this
information for applicability to their facilities and consider actions, as
appropriate, to avoid similar problems. However, suggestions contained in
this information notice do not constitute NRC requirements; therefore, no
specific action or written response is required.
Description of Circumstances:
a. HFA Relays
In June 1986, Duane Arnold Energy Center reported that HFA relays were
not resetting. GE determined, after investigation, that mechanical
binding in the relays prevented the normally closed contacts from making
contact when the relays were de-energized. This was caused by the
incorrect location of a stop tab that is welded to the armature. The
incorrect location, combined with possible movement of the magnetic
assembly, causes the armature binding. In July 1986, TVA experienced
similar problems.
On July 21, 1986, the GE Meter and Control Business Division (MCBD),
Malvern, Pennsylvania, issued a 10 CFR Part 21 report to the NRC. On
November 14, 1986, MCBD issued Service Advice Letter (SAL) 188.1, which
instructed recipients to test the relay to identify and correct improper
operation. The SAL stated that MCBD could not determine when the stop
tab problem had begun, but that relays manufactured between January 1983
and October 1986 were suspect. Date codes were provided that could be
8804110009
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April 18, 1988
Page 2 of 4
used to identify potentially affected relays. However, on June 5, 1987,
Pilgrim implemented SAL 188.1 and identified several improperly operating
relays which were manufactured outside the suspected date codes.
In view of this, all HFA relays may be suspect. Additionally, the NRC
recently issued NRC Bulletin 88-03, "Inadequate Latch Engagement in HFA
Type Latching Relays Manufactured by General Electric (GE) Company,"
March 10, 1988, regarding problems from inadequate latch engagement.
b. PVD 21B and PVD 21D Relays (see Attachment 1)
In 1977, GE listed the seismic capability of the normally open contacts
of the PVD 21B and PVD 21D differential relays as 6g zero period
acceleration (ZPA) with the relay energized and the contacts closed. The
tripping of each of these relays in response to differential over current
is by a "low set" voltage unit, device 87L, and a "high set" current
unit, device 87H. Device 87L is an instantaneous voltage unit that has
its coil connected across the dc terminals of a full wave rectifier
device. Device 87L has two sets of normally open contacts, one of which
is connected in parallel with the contacts of the seal-in unit. Device
87H is an instantaneous overcurrent unit, with its coil connected in
series with thyrite discs; it has a single set of normally open contacts.
Originally, GE published data which implied that the seismic capability
of 6g ZPA applied equally to both 87H and 87L functions. In 1983, GE
revised the seismic capabilities as follows: the capability of the 87L
function remained at 6g ZPA, and the capability of the 87H function was
reduced to 2g ZPA. GE stated that the 87H set of normally open contacts
is generally wired in parallel with both the open 87L contacts and the
open 87L seal-in contacts when the PVD relay is used to trip a circuit
breaker. GE stated that the 87H function of the PVD is less sensitive
than the 87L function (it requires more operating signal). As a result,
opening the normally open 87H contacts for a time greater than 2 milli-
seconds as a consequence of a seismic event between 2g and 6g ZPA should
not interfere with tripping the circuit breaker because the parallel 87L
contact would remain closed up to 6g ZPA. In view of the 2g ZPA seismic
capability of the 87H contact, GE recommended the application be checked
if the 87H contacts are used separately for any functions other than
tripping.
c. HGA Relays (see Attachment 1)
During a re-evaluation of qualification data for relays used in nuclear
Class 1E systems, MCBD determined that the seismic data for HGA 11 and
HGA 111 relays published in MIL No. RS77-3, dated March 25, 1977, were in
error. The incorrect data were revised in MIL No. 82-12, dated July 26,
1982. Specifically, MIL No. RS77-3 listed the seismic capability of the
normally closed contacts of ac-rated HGA 11 or HGA 111
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April 18, 1988
Page 3 of 4
relays at 1.0g ZPA when the relays were in the de-energized state. The
dc-rated relays were listed at 1.5g ZPA for the same condition. The re-
vised seismic capability of the normally closed contacts of both ac and
dc HGA 11 and HGA 111 relays in the de-energized state is less than 0.5g
ZPA.
GE has conducted studies to determine design changes that could improve
the seismic capability of the normally closed contacts when the relay is
de-energized. Additionally, a separate study considered the seismic
capability of alternate HGA relay models as a means for improving the
seismic capability of normally closed contacts with the relay
de-energized. At this time, GE has no plans for development of an HGA
relay with improved seismic capability.
On the basis of the above information, GE recommends that Class 1E cir-
cuits using normally closed contacts of HGA 11 and HGA 111 relays, with
the relay de-energized, be evaluated for the effect on the entire circuit
of an HGA 11 or HGA 111 contact opening longer than 2 milliseconds.
On June 24, 1987, Duane Arnold reported to the NRC (1) that, based on the
revised data, HGA 11 relays providing critical functions in the core
spray, low pressure coolant injection, high pressure coolant injection,
and reactor core isolation cooling systems at Duane Arnold have
indeterminate qualification, and (2) that the relays were being replaced.
Discussion:
a. HFA Relays
For HFA relays, in addition to SAL 188.1, GE issued the following SALs:
(1) SAL 139.2, dated April 28, 1976. This SAL superseded SAL 139.1,
dated September 5, 1973.
(2) SAL 152.1, dated April 28, 1976.
(3) SAL 152.2, dated November 3, 1980.
(4) SAL 152.2A, dated March 12, 1982.
(5) SAL 169.1, dated May 28, 1982.
b. PVD 21 Relays
For PVD 21 relays, GE issued SAL 174.1 dated April 11, 1983. This SAL
provided clarification of the seismic capability of the 87H and 87L
contacts.
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April 18, 1988
Page 4 of 4
Most plants using PVD and HGA style relays are subject to the verification of
seismic adequacy of mechanical and electrical equipment under Unresolved
Safety Issue (USI) A-46 (as outlined in Generic Letter 87-02). However, PVD
and HGA style relays have also been found in newer plants that are not subject
to Generic Letter 87-02 (e.g., Susquehanna Unit 2 LER 86-024-000).
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contact 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 Contact: K. R. Naidu, NRR
(301) 492-0980
Attachments:
1. General Electric Letter to NRC
dated February 24, 1983
2. List of Recently Issued NRC Information Notices
. Attachment 2
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April 18, 1988
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
88-13 Water Hammer and Possible 4/18/88 All holders of OLs
Piping Damage Caused by or CPs for nuclear
Misapplication of Kerotest power reactors.
Packless Metal Diaphragm
Globe Valves
88-12 Overgreasing of Electric 4/12/88 All holders of OLs
Motor Bearings or CPs for nuclear
power reactors.
88-11 Potential Loss of Motor 4/7/88 All holders of OLs
Control Center and/or or CPs for nuclear
Switchboard Function Due power reactors.
to Faulty Tie Bolts
88-10 Materials Licensees: Lack 3/28/88 All NRC licensees
of Management Controls Over authorized to use
Licensed Programs byproduct
material.
87-44, Thimble Tube Thinning in 3/28/88 All holders of OLs
Supp. 1 Westinghouse Reactors or CPs for nuclear
power reactors
that employ a
Westinghouse NSSS.
88-09 Reduced Reliability of 3/18/88 All holders of OLs
Steam-Driven Auxiliary or CPs for nuclear
Feedwater Pumps Caused power reactors.
by Instability of Woodward
PG-PL Governors
88-08 Chemical Reactions with 3/14/88 All NRC licensees
Radioactive Waste generating or pro-
Solidification Agents cessing low level
radioactive waste.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit
