Bulletin 83-01: Failure of Reactor Trip Breakers (Westinghouse DB-50) to Open on Automatic Trip Signal
SSINS No.: 6820
OMB No.: 3150-00012
Expiration Date: 04/30/85
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
February 25, 1983
IE BULLETIN NO. 83-01: FAILURE OF REACTOR TRIP BREAKERS (WESTINGHOUSE
DB-50) TO OPEN ON AUTOMATIC TRIP SIGNAL
All pressurized water nuclear power reactor facilities holding an operating
license (OL) for action and to other nuclear power reactor facilities for
The purpose of this bulletin is to inform CP holders and licensees about
recent failures of W DB type circuit breakers to trip open on receipt of an
automatic trip signal from the reactor protection system (RPS) and to
require action of all operating pressurized water reactors to assure proper
operation of those breakers in the future.
Description of Circumstances:
On February 25, 1983, during startup of the Salem Unit 1 plant, both DB-50
RPS breakers failed to open automatically upon receipt of a valid trip
signal on low-low steam generator level.
This failure to trip has been attributed to sticking of the undervoltage
trip attachment. The reactor was tripped manually from the control room
about 30 seconds after the automatic trip signal was generated. The manually
initiated trip was accomplished by the shunt relays installed in each DB-50
In some reactor protection system designs, the automatic protection signals
are fed only to the undervoltage (UV) trip attachment of the reactor trip
breakers; the manual signals are fed both to the UV trip and to a shunt trip
coil of each breaker.
In the recent past, on two separate occasions, one RPS breaker at the Salem
facility failed to open automatically due to binding of the UV trip
attachment. These events have been reported in LER's 82-072/03X-1 and
83-001/03L. In addition, on February 22, 1983, Salem Unit 1 tripped on
low-low steam generator level; however, since the operator manually tripped
the reactor at a time almost coincidental with the automatic trip signal,
the actual trip mechanism (manual or automatic) cannot be ascertained.
February 25, 1983
Page 2 of 3
Similar failures involving the UV trip attachment to the RPS have been
reported to the NRC. These failures only involved one of the two series
breakers, therefore they did not result in a failure to automatically trip
the reactor. Said failures have occurred at H. B. Robinson, Connecticut
Yankee, Prairie Island and St. Lucie in addition to those at Salem. As a
result of these events, the NRC issued IE Bulletin No. 71-02 and IE Circular
No. 81-12, and Westinghouse issued Technical Bulletin No. NSD-78-74-1 dated
January 11, 1974 and NSD Data Letter 74-2 dated February 14, 1974.
Required Actions for All Holders of Operating Licenses for Pressurized Water
Licensees with W DB type breakers using undervoltage trip attachment in
Reactor Protective System applications are requested to:
1. Perform surveillance test of undervoltage trip function independent of
the shunt trip within 24 hours of receipt of this Bulletin unless
equivalent testing has been performed within 5 days. Those plants for
which on-line testability is not provided may complete this item before
resuming operation or if currently operating, at the next plant
2. Review the maintenance program for conformance to recommended W program
(attachment) including frequency and lubricant applied to trip
mechanism. Verify actual implementation of the W program. If
maintenance including lubrication does not conform, initiate such
maintenance within 5 days of receipt of this bulletin or provide an
alternate maintenance program. Repeat the testing required in item 1
prior to declaring the breaker OPERABLE.
3. Notify all licensed operators of the failure-to-trip event which
occurred at Salem. Review the appropriate emergency operating
procedures for the event of failure-to-trip with each operator upon his
4. Provide written reply within 7 days of receipt of this bulletin,
a. identifying results of testing performed in response to item 1,
b. identifying conformance of maintenance program to W recommendation
and describing results of maintenance performed directly as a
result of this Bulletin in response to item 2,
c. provide statement that provisions are in place to notify licensed
operators of the Salem event and bring to their attention
appropriate failure-to-trip emergency procedures upon their
d. You are reminded of the requirements for prompt notification in
accordance with 10 CFR 50.72 in the event of detecting an
inoperable RPS breaker.
February 25, 1983
Page 3 of 3
PWR Licensees not using the subject undervoltage trip attachment and
therefore not affected by this bulletin shall submit a negative declaration
within 7 days of the receipt of this bulletin.
The written report required shall be submitted to the appropriate Regional
Administrator under oath or affirmation under provisions of Section 182a,
Atomic Energy Act of 1954, as amended. The original copy of the cover
letters and a copy of the reports shall be transmitted to the U. S. Nuclear
Regulatory Commission, Document Control Desk, Washington, D.C. 20555 for
reproduction and distribution.
This request for information was approved by the Office of Management and
Budget under a blanket clearance number 3150-00012 which expires April 30,
1985. Comments on burden and duplication may be directed to the Office of
Management and Budget, Reports Management, Room 3208, New Executive Office
Building, Washington, D.C. 20503.
If you have any questions regarding this matter, please contact the Regional
Administrator of the NRC Regional Office or the technical contact listed
Richard C. DeYoung, Director
Office of Inspection and Enforcement
Technical Contact: I. Villalva, IE
V. Thomas, IE
J. T. Beard, NRR
1. Transcription of Westinghouse NSD Ltr. 74-2
2. List of Recently Issued IE Bulletins
February 25, 1983
Verbatim transcription of Westinghouse NSD letter 74-2. Original signed by
W. H. Furfari and Sydney G. Caslake.
NSD DATA LETTER 74-2
FROM : Nuclear Service Division
WIN : 236-4744
DATE : February 19, 1974
SUBJECT : Reactor Trip Breaker
NUCLEAR ENERGY SYSTEMS
Technical Bulletin NSD-TB-74-1 (issued 1/11/74) described a reactor trip
breaker malfunction which occurred at H. B. Robinson station in December of
1973, and recommended certain additional periodic maintenance measures to
improve the reliability of these breakers.
The malfunction (failure to trip during a regularly scheduled periodic test)
was attributed to excessive friction in the linkage of the Undervoltage Trip
Attachment, which is the device that initiates the breaker drop-open action
by elevating the trip bar. The problem was corrected by cleaning and lightly
lubricating certain portions of the linkage.
To preclude the possibility of reoccurrence of this malfunction,
Westinghouse recommends that the reactor trip breakers be given regularly
scheduled periodic inspection/maintenance as described in the Instruction.
Manual and in line with the following guidelines.
1. Scope. These recommendations are intended to apply to Westinghouse
DB-50 (or DB-25) breakers in Reactor Trip applications. Some future
WNES plants will be supplied with Westinghouse Type DS (stored energy)
breakers, which should be maintained in accordance with their
2. Related Operations. It is expected that these inspection and main-
tenance measures would normally be carried out in conjunction with
breaker periodic operational testing or during plant shutdowns.
However, these recommendations in no way are intended to supersede
breaker operational testing commitments and requirements.
3. Frequency. Intervals between maintenance will be influenced by
operating and atmospheric conditions, but we would recommend that
initially it be performed on a semi-annual basis. The period might then
be extended to 9 or 12 months if experience shows this to be
NSD DATA LETTER 74-2 - 2 - February 19, 1974
4. Cleaning. Clean the entire unit by blowing with dry instrument air (or
a hand bellows), followed by vacuum cleaning. Particular attention
should be paid to the cleanness of the undervoltage trip device, which
can be inspected without component disassembly.
5. Solvents. In general, the use of a cleaning solvent is not encouraged
since some can be damaging to electrical components. If there is a
particularly heavy deposit of contaminants, an inert or mild solvent
such as Stoddard solvent could be used if applied sparingly.
6. Lubricants. Although the Instruction Manual (page 5) cautions against
any re-lubrication in the field, the manufacturers have agreed that the
reliability of the breaker is improved by lightly lubricating the
linkage of the undervoltage device occasionally. However, the lubricant
should be applied only sparingly to the front and back faces of the
vertical-traveling latch (interfacing with the flat copper-alloy
A dry or near-dry molybdenum disulfide lubricant should be used.
Technical Bulletin NSD-TB-74-1 indicated Molykote G as a possible
choice. That information is incorrect and is hereby rescinded Molykote
G uses a thickened mineral oil as a vehicle, which would tend to
collect foreign material. A better choice would be Molykote M-88, or
Spray-kote. Both are commercially available Dow Corning products.
7. Inspection. Following the above cleaning and lubrication the entire
breaker should be operationally checked and inspected for broken parts,
loose bolts or excessive wear.
This Date Letter and the above information supersedes Technical Bulletin
NSD-TB-74-1, which is hereby cancelled.
W. H. Furfari
APPROVED: Syndey G. Caslake, Manager
Page Last Reviewed/Updated Wednesday, March 24, 2021