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Surface Contamination Monitors - doe-std-1128-98_ch10069
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DOE Standard Guide of Good Practices for Occupational Radiological Protection In Plutonium Facilities
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Instrument Calibrations and Testing - doe-std-1128-98_ch10071


DOE-STD-1128-98
Criticality Alarm Systems. ANSI/ANS 8.3 (ANSI, 1986a) discusses the
performance and design criteria for criticality accident alarm systems.
The criteria include the following:
-- Criticality alarm systems shall be designed to detect immediately the
minimum accident of concern; the minimum accident may be
assumed to deliver the equivalent of an absorbed dose in free air of
20 rad at a distance of 2 meters from the reacting material within 60
seconds.
-- Systems shall be designed so that instrument response and alarm
latching shall occur as a result of radiation transients of 1-
millisecond duration. The alarm signal shall be for evacuation
purposes only and of sufficient volume and coverage to be heard in
all areas that are to be evacuated. Very high audio background noise
in some areas may require that the alarm be supplemented with
visual signals; however, high background noise is a dangerous
situation that should be prevented by design. Instrument response to
radiation shall be calibrated periodically to confirm the continuing
performance of the instrument. The calibration interval may be
determined on the basis of experience but shall be no less frequent
than annually. Tests should be performed at least monthly and the
results of testing should be documented.
The standard does not quantify criteria for reliability or the rejection of
false alarms. Consideration should be given to the avoidance of false
alarms as accomplished by providing reliable single detector channels or
by requiring concurrent response of two or more detectors to initiate the
alarm. (ANSI 1986a).
Fixed Nuclear Accident Dosimeters. All DOE facilities that have
sufficient quantities and kinds of fissile material to potentially constitute
a critical mass, such that the excessive exposure of personnel to radiation
from a nuclear accident is possible, shall provide nuclear accident
dosimetry for those personnel (10 CFR 835.1304). Requirements for
fixed nuclear accident dosimeters are found in DOE Order 420.1A
(DOE, 2003a).
Effluent Monitors. Facilities that deal with unencapsulated plutonium
should have continuously operating effluent monitors to determine
whether or not plutonium is being released to the environment. Effluent
monitor criteria is found in IEC Publications 761-1 and 761-6 (IEC,
1983) and ANSI N42.18 (ANSI, 1974b) and should be performed.
Similar to airborne contamination monitors, effluent monitors should be
tested for air in-leakage at least annually or when seals or "O" rings are
replaced.
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