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DOE-STD-1128-98
Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities
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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