EH-0135 Radiation Survey Meter
ENVIRONMENT, SAFETY & HEALTH
SAFETY ACTION
Assistant Secretary for U.S. Department of Energy
Environment, Safety & Health Washington, D.C. 20585
DOE/EH-0135 Issue No. 90-2 February 1990
Radiation Survey Meter
Product:
Bicron RSO-5 Dose Rate Instrument
Problem:
A Bicron RSO-5 Dose Rate Meter responded incorrectly on the second (0-50 mR/h)
scale after causing a full-scale deflection on the first (0-5 mR/h) scale.
The problem occurred when two health physics personnel were providing
radiation protection coverage for Instrument Maintenance personnel, who were
checking criticality alarms at a DOE contractor facility. A normal reading
was observed on the dose rate instrument's third scale (0-500 mR/h). No
personnel overexposure to radiation occurred due to these instrument failures.
Another problem developed when the above instrument was improperly tagged with
a health physics material transfer tag instead of one that reads
"Defective--Do Not Use!" The facility had no governing health physics
procedure for tagging defective instrumentation.
A day later a second instrument experienced the same malfunction, was tagged,
and removed from service.
Cause:
The instruments were taken out of service and returned to the manufacturer.
Bicron's examination of the two RSO-5 dose rate meters, which were sent back
for warranty repair, revealed the root cause of the failure to be the
misalignment of the magnetic arm which activates reed switches in the ion
chamber. This alignment resulted in improper range switching.
The Instrument Engineering Department of Bicron evaluated the magnitude of the
above-mentioned problem and took appropriate actions, including installation
of a set screw that maintains alignment of the magnetic arm. Bicron also has
added another quality assurance step to its final check-out. They will check
the sensitivity of magnetic switching related to the alignment of the various
components in their dose rate instruments to be sure they are within
acceptable tolerances.
Action:
All magnetic arm design radiacs should be removed from service and inspected
for proper alignment of the magnetic arms and the presence of set screws to
maintain the proper positioning of the magnetic arms. For a more thorough and
technical discussion of this issue, inspection procedures, and corrective
action, contact Dale Fleming (Pacific Northwest Laboratory (PNL)) at FTS
444-3468, COM 509-375-3468, Ken Swinth (PNL) at FTS 444-3773, COM
509-375-3773.
American National Standards Institute (ANSI) Standard N 323 requires
calibration of dose rate instruments at least annually. This incident
indicates frequent calibration may be needed. DOE contractors may want to
consider revising their internal procedures to require more frequent
calibration.
In addition to the Bicron Model RSO-5, malfunctions may occur in the following
instruments or other instruments using this type of magnetic arm design.
Bicron Model RSO-50
Bicron Model RSO-500
Eberline Model RO-2
Eberline Model RO-2A
(NOTE: Dose rate instrumentation such as Bicron RSO-5 with magnetic scale
switching cannot be used in areas with high magnetic fields.)
If a malfunction occurs, return the instrument(s) to the appropriate
manufacturer.
Bicron Corporation
12345 Kingsman Road
Newbury, OH 44065
PH: 216-564-2251
Eberline Instrument Corporation
504 Airport Road
P.O. Box 2108
Santa Fe, NM 87504-2108
PH: 505-471-3232
As always, this office encourages your comments and suggestions on our
bulletins; and if you have experienced similar problems with instruments of
this type, we would appreciate hearing about them.
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This publication is one of several series of bulletins published so that DOE
program managers and contractors can share information about potential
occupational safety problems relevant to DOE operations. For more information
or additional copies, contact Eleanor Crampton, Performance Evaluation
Division, Office of Safety Compliance, Assistant Secretary for Environment,
Safety & Health, U.S. Department of Energy, Washington, DC 20545; telephone
FTS 233-3732, Commercial (301) 353-3732.
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