Information Notice 1990-44, Dose-Rate Instruments Underresponding to the True Radiation Fields
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
June 29, 1990
NRC INFORMATION NOTICE NO. 90-44: DOSE-RATE INSTRUMENTS UNDERRESPONDING
v
TO THE TRUE RADIATION FIELDS
Addressees
All NRC licensees.
Purpose
This information notice is intended to alert addressees to potential problems
resulting from dose-rate survey instruments underresponding to the true radia- tion fields. It is expected that recipients will review the 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
The Department of Energy (DOE) recently issued a Safety Action Notice that
described an underresponse of two Bicron RSO-5 dose-rate instruments by a
factor of about 100 on the-second range (0-50 mR/h). The problem occurred when
two radiation protection personnel were providing radiation protection coverage
at a DOE contractor facility. A normal reading was observed on the dose-rate
instrument's third range'(0-500 mR/h). No personnel were overexposed to
radiation when these instruments failed. Other instruments which have the same
type of magnet arm switching design as the RSO-5 can have this same type of
problem.
The Instruments were removed from service and were returned to the manufac- turer. Bicron's examination confirmed the effect and found that the failure
had been caused by a change in positioning of the magnet that activates reed
switches in the ion chamber. This magnet moves on a cam-actuated arm, and the
cam is attached to the range switch.
Figure 1 illustrates typical magnet anm
positions for the Bicron RSO series of instruments. At the zero position (one
end) of the range switch rotation, the arm moves the magnet over the zero reed
switch and shorts the electronic input for zeroings Switching from zero to the
first (0-5 mR/h) and second (0-50 mR/h) ranges, the cam moves the end of the
magnet anm to the center position'between the zero and high-range reed
switches,'and neither reed switch Is closed. If the magnet arm is not properly
aligned with the cam at the point of contact, the extra room allowed (play) for
movement of the magnet arm with respect to the cam can result in the magnet at.
/-
IN 90-44 June 29, 1990 the other end of the magnet arm being placed sufficiently past the center
position to close the high-range reed switch upon range switching between the
first (0-5 mR/h) and the second (0-50 mR/h) of the lower two ranges even though
the magnet arm is not supposed to move.
Because of this possible mechanical problem, severe underresponse to the true
radiation fields for these dose-rate survey instruments can occur as a result
of switching between these lower two ranges. This is because when the
high-range reed switch is in the closed position, a different electronic
circuit is actuated which reduces the sensitivity on these ranges by a factor
of about 100. This reduced sensitivity requires a true dose rate of 5,000 mR/h
to produce a full-scale deflection on the second-range (0-50 mR/h) scale or a
true dose-rate of 500 mR/h to produce a full-scale deflection on the
first-range (0-5 mR/h) scale.
The Instrument Engineering Department of'Bicron has included an additional
quality assurance (QA) test to ensure the proper alignment of the magnet arm
with respect to the reed switch and latitude for minor position changes that
might occur.
This QA test is to be performed during the final acceptance test
of a new instrument and again before the new instrument is calibrated for
shipment.
Discussion:
All licensees need to be aware of the potential for underresponse at the lower
two ranges for all magnet arm switching dose-rate instruments.
Failure (i.e.,
high-range reed switch in the open position) at the high-range settings (0-500
mR/h, 0-5,000 mR/h) can only result in overresponse of the instrument. If.
when performing a survey with the instrument, the operator is not sure that
he/she is in a high radiation field, the operator can verify that the instru- ment is not underresponding during these situations by switching to the
high-range settings to quantify the upper limit of the radiation field before
switching to the lower range settings.
This type of instrument problem reinforces the importance of source checking
the instrument for each range before use, consistent with good ALARA (as low as
reasonably achievable) practices.
It is important that licensees also be aware that use of this type of magnet
arm switching instrument in areas with high magnetic fields can inadvertently
actuate the reed switches in the instrument without movement of the magnet arm.
For more information, refer to ANSI N42.17A, NPerformance Specifications for
Health Physics Instrumentation Portable Instrumentation for Use in Normal
Environmental Conditions."
In addition to the Bicron Model RSO-5, malfunctions may also occur for the
following instruments;
0
Bicron Model RSO-50
o
Eberline Model RO-2
0
Eberline Model RO-2A
IN 90-44 June 29, 1990 Since 1982, Eberline has added a pilot hole to the switch shaft to allow the
set screw to align the collar which actuates the magnet arm. Additionally, in
the Eberline design, the magnet arm is straight and the distance between
adjacent positions is greater than in the Bicron instrument. This feature
reduces the probability for indirect switching of a reed switch (as happened
with the two instruments at the DOE contractor facility).
Although the magnet anm is aligned properly at the time of production, this
alignment can shift with time and normal field usage. Therefore, the Depart- ment of Energy Safety Action Notice recommends that all magnet arm switching
dose-rate Instruments be inspected at regular intervals for proper alignment of
the magnet arm. Both Bicron and Eberline have prepared new inspection proce- dures for their instruments. For copies of revised maintenance procedures and
other technical information concerning their instrument, contact the appropri- ate manufacturer at one of the following addresses:
Bicron Corporation
12345 Kingman Road
Newbury, Ohio 44065
Jose h G. Bellian
(216) 564-8000
Eberline Instrument Corporation
504 Airport Road
P.O. Box 2108
Santa Fe, New Mexico 87504-2108
Customer Service, Santa Fe, Kew Mexico
Robert Montaya
1-800-234-4212
Customer Service, Columbia, South Carolina
John Witzell
1-800-274-4212 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact the
technical contact listed below or the appropriate NRR project manager.
s E. Ross, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact:
Joseph C. Wang, NRR
(301) 492-1848 Attachments:
1. Figure 1, Typical Magnet Arm Position, RSO Instruments
2. List of Recently Issued NRC Information Notices
lI
I;1 Typical "CE
. Position For
Zero Reed
-
Switch Closure.
.37 Mu
.375"
Min.
Typical -B1 Position For
-
High Range Reed
SWitch Closure.
C
Figure 1, Typical Magnet Arm Position, RSO Instruments
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-
1_
Attachment 2
IN 90-44 June 29, 1990
-
, LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Notice No.
SubJect
Date of
t
Issuance
Issued to
V
.
90-43
90-32, Supp. 1
90-42
90-41
90-40
Mechanical Interference
With Thermal Trip Function
in GE Molded-Case Circuit
Breakers
Surface Crack and Subsurface
Indications in the Weld of
a Reactor Vessel Head
Failure of Electrical Power
Equipment Due to Solar
Magnetic Disturbances
Potential Failure of General
Electric Magne-Blast
Circuit Breakers and AK
Circuit Breakers
6/29/90
6/19/90
6/19/90
6/12/90
6/5/90
6/1/90
5/29/90
Results
Testing
Valves
of NRC-Sponsored
of Motor-Operated
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All fuel facility
and materials
licensees.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors, and
10 CFR 70 licensees.
Recent Problems With Service
Water Systems
Requirements for Processing
Financial Assurance Submittals
for Decommissioning
90-38
90-37 Sheared Pinion Gear-to-Shaft '5/24/90
Keys in Limitorque Motor
Actuators
90-36
Apparent Falsification of
State of Connecticut
Weight Certificates
5/24/90
OL = Operating License
CP = Construction Permit
IN 90-44 June 29, 1990 Since 1982, Eberline has added a pilot hole to the switch shaft to allow the
set screw to align the collar which actuates the magnet arm. Additionally, in
the Eberline design, the magnet arm is straight and the distance between
adjacent positions is greater than in the Bicron instrument.
This feature
reduces the probability for Indirect switching of a reed switch (as happened
with the two instruments at the DOE contractor facility).
Although the magnet arm is aligned properly at the time of production, this
alignment can shift with tilpe and normal field usage. Therefore, the Depart- ment of Energy Safety Action Notice recommends that all magnet arm switching
'
dose-rate instruments be inspected at regular intervals for proper alignment of
the magnet arm.
Both Bicron and Eberline have prepared new inspection proce- dures for their instruments.
For copies of revised maintenance procedures and
other technical information concerning their instrument, contact the appropri- ate manufacturer at one of the following addresses:
Bicron Corporation
12345 Kingman Road
Newbury, Ohio 44065
Joseph G. Bellian
(216) 564-8000
Eberline Instrument Corporation
504 Airport Road
P.O. Box 2108
Santa Fe, New Mexico 87504-2108 Customer Service, Santa Fe,
Robert Montaya
1-800-234-4212 Customer Service, Columbia,
John Witzell
1-800-274-4212 New Mexico
South Carolina
This Information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact the
technical contact listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact:
Joseph C.lWang, NRR
(301) 492-1848 Attachments:
1. Figure 1, Typical Magnet Arm Position, RSO Instruments
2. List of Recently Issued NRC Information Notices
Document Name:
INFO NOTICE - WEN, WANG
- Transmitted by memo for C. E. Rojs4Wieme.E 4 J. Congel dated May 23, 1990
- SEE PREVIOUS CONCURRENCES AJ7Di£
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- C/OGCB:DOJEA:NRR **RPB:ADM
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06/15/90
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06/15/90
05/11/90
.05/11/90
05/21 90
05/23/90
IN 90-XX
June xx, 1990 Since 1982, Eberline has added a pilot hole to the switch shaft to allow the
set screw to align the collar which actuates the magnet anm. Additionally, in
the Eberline design, the magnet arm is straight and the distance between
adjacent positions is greater than in the Bicron instrument. This reduces the
probability for indirect switching of a reed switch (as happened with the two
instruments at the DOE contractor facility).
Although the magnet arm is aligned properly at the time of production, this
alignment can shift with time and normal field usage.
Therefore, the Depart- ment of Energy Safety Action Notice recommends that all magnet arm switching
dose-rate instruments be inspected at regular intervals for proper alignment of
the magnet arm.
Both Bicron and Eberline have prepared new inspection proce- dures for their instruments.
For copies of revised maintenance procedures and
other technical information concerning their instrument, contact the appropri- ate manufacturer at one of the following addresses:
Bicron Corporation
12345 Kingman Road
Newbury, Ohio 44065
Joseph G. Bellian
(216) 564-8000
Eberline Instrument Corporation
504 Airport Road
P.O. Box 2108
Santa Fe, New Mexico 87504-2108
Customer Service, Santa Fe, New Mexico
Robert Montaya
1-800-234-4212
Customer Service, Columbia, South Carolina
John Witzell
1-800-274-4212 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact the
technical contact listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact:
Joseph C. Wang, NRR
(301) 492-1147 Attachments:
1. Figure 1, Typical Magnet Arm Position, RSO Instruments
2. List of Recently Issued NRC Information Notices
- Transmitted by memo for C. E. Rossi from F. J. Congel datd ay 23 1990
Document Name:
INFO NOTICE - WEN, WANG
D/DOEA:NRR
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JEWigginton
LJCunnilngham
FJCongel
06/1S/90
05/11/90
05/11/90
05/21/90
05/23/90
V
May 23, 1990
MEMORANDUM FOR:
FROM:
SUBJECT:
Charles E. Rossi, Director
Division of Operational Events Assessment, NRR
Frank J. Congel, Director
Division of Radiation Protection
and Emergency Preparedness, NRR
INFORMATION NOTICE: "DOSE-RATE SURVEY INSTRUMENTS
UNDERRESPONDING TO THE TRUE RADIATION FIELDS"
Please issue the enclosed Information Notice.
All regional offices and NMSS have had the opportunity to comment on
document and all comments received have been considered in preparing
notice. In accordance with NRC Inspection Manual Chapter 0720, both
(Eicron and Eberline) comments have also been considered.
this
the
vendors'
Completed copies of the "Headquarters Daily Report Form" and the "Generic
Communications Index Input Form" are also enclosed.
/s/
Frank J. Congel, Director
Division of Radiation Protection
and Emergency Preparedness, NRR
Enclosures:
As stated
Contact: Joseph C.
492-1147 Wang, NRR
DISTRIBUTION:
F. Congel
J. Cunningham
J. Wigginton
J. Hickey
PRB R/F
T. Essig
R. Anderson
Central Files
R. Erickson
R. Barrett
- . Wang As
- See previous concurrence
SFC
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- 5/21/90
- 5/t3/9O
OFFICIAL RECORD COPY
Document Name: ROSSI MEMO/INFO NOTICE
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