IE Circular 76-04 - Neutron Monitor and Flow Bypass Switch Malfunctions
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D. C. 20555
September 29, 1976
J. P. O'Reilly, Director, Region I
N. C. Moseley, Director, Region II
J. G. Keppler, Director, Region III
E. M. Howard, Director, Region IV
R. H. Engelken, Director, Region V
IE CIRCULAR 76-04 - NEUTRON MONITOR AND FLOW BYPASS SWITCH MALFUNCTIONS
Enclosed is IE Circular No. 76-04 for distribution to all boiling water
reactor facilities with an operating license or construction permit.
This Circular should be forwarded by mail or other means within three
working days of receipt of this memorandum by your office.
Dudley Thompson, Acting Director
Division of Field Operations
Office of Inspection and Enforcement
1. Draft letter to
2. IE Circular 76-04
and Flow Bypass
(Addressees: Reactor Facilities OL and CP Holders)
The enclosed Circular No. 76-04 is forwarded to you as a matter concerning a
possible generic problem relating to reactor safety systems and components.
Any questions regarding this Circular should be directed to this office.
(Director, Regional Office)
Circular No. 76-04
IE Circular No. 76-04 Date: September 29, 1976
NEUTRON MONITOR AND FLOW BYPASS SWITCH MALFUNCTIONS
DESCRIPTION OF CIRCUMSTANCES:
Defective Neutron monitoring bypass switches have been experienced by
General Electric during fabrication of control panels which were designated
for shipment to nuclear power plants. According to GE, switch malfunctions
of this type also were reported from nuclear power plants following their
initial finding. The types of malfunctions experienced were:
1. Failure to move to a positive position.
2. Double contact operation causing an intermittent double bypass action.
The cause of the bypass switch malfunctioning has been identified by the
General Electric Company as improper fabrication (an inadequate weld of
parts of the switch mechanism). This phenomenon occurs after numerous
bending motions and results in improper switch alignment, referred to by GE
as "metal creep."
Portions of a GE service letter containing information about these bypass
switches is attached to this Circular. Further information regarding this
problem can be obtained from General Electric Company, 175 Curtner Avenue,
San Jose, California 95125.
ACTION TO BE TAKEN BY LICENSEES AND PERMIT HOLDERS:
For all boiling water reactor facilities with an operating license or
1. Describe any malfunction experienced by your facility regarding these
switches. Include in your response the approximate date of failure and
any corrective measure taken to resolve the failure.
2. If you have received the attached general Electric service letter (SIL
111, Rev. 1, dated August 29, 1975), describe the actions taken
regarding corrective measures to resolve the bypass control switch
problem as discussed in the attached GE service letter. Include in
your response your means of testing this circuitry to assure
3. If you have not received General Electric SIL 111, Rev 1, describe the
actions planned if switches of the type described in the attached
General Electric service letter are in use of planned for use in
safety-related systems at your facility. Include in your response your
means of testing this circuitry to assure operability.
Reports from facilities with operating licenses should be submitted within
60 days after receipt of this Circular, and reports from facilities with
construction permits should be submitted within 90 days after receipt of
this Circular. Your report should include the date when the above actions
were or will be completed.
Reports should be submitted to the Director of the NRC Regional Office and a
copy should be forwarded to the NRC, Office of Inspection and Enforcement,
Division of Reactor Inspection Programs, Washington, D. C. 20555.
Approval of NRC requirements for reports concerning possible generic
problems has been obtained under 44 U. S. C. 3512 from the U.S. General
Accounting Office. (GAO Approval B-180255 (R0072), expires 7/31/77).
Extract from General Electric SIL 111, Rev. 1.
Page 1 of 2 pages
Extract from General Electric SIL 111, Rev. 1:
NEUTRON MONITOR AND FLOW BYPASS SWITCH MODIFICATION
General Electric has learned of a "metal creep" phenomenon which exists
within the joystick operators of certain control room switches. These
switches are used at most operating GE/BWR plants in the Source Range
monitor (SRM), Intermediate Range Monitor (IRM), Average Power Range Monitor
(APRM) and Rod Block Monitor (RBM) Systems. The switches are also used as
flow bypass switches and in other applications. "Metal creep" is a condition
which occurs in metal after numerous bending motions. This causes the metal
to expand slightly. The problem of "metal creep" with the joystick operator
can result in improper switch alignment. This can cause the switch to make
multiple contacts (characterized by two or more channels being bypassed
simultaneously). Also, the joystick handle may appear to be in a neutral
position while actually the switch contacts (due to "metal creep") are in a
General Electric recommends that the bypass position be verified by the
channel by pass indicator light and/or a computer run whenever these
switches are operated. General Electric also recommends replacement of both
the switch and operator with improved components if problems are
encountered. The replacement switches will vary from one generation of GE
BWR to another. The physical description should include the number of
contact blocks in the switch; the presence or absence of physical barriers
between the contact blocks; and whether or not the switch is enclosed in a
metal box. The new switches contain both physical barriers and a metal
switch enclosure. The part numbers given below may be of assistance in
determining your particular requirements:
Page 2 of 2 Pages
New Part No. Old Part No. Where Used
193B1100G003 193B1100G001 APRM
193B1100G004 193B1100G002 IRM
To provide additional assurance that the RBM and flow bypass switches do not
become improperly aligned due to metal creep, GE recommends implementing the
wiring change given in the table below.
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