Criticality Accident Alarm Systems (CAAS)

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

Criticality Accident Alarm Systems (CAAS). See section 7.0 for discussion of nuclear

criticality safety, including CAAS.

Fixed Nuclear Accident Dosimeters. All DOE facilities that have sufficient quantities and kinds

of fissile material to potentially constitute a critical mass should provide nuclear accident dosimetry.

Requirements for fixed nuclear accident dosimeters are found in 10 CFR 835.1304 and DOE Order

420.1A, Facility Safety (DOE 2002).

Effluent Monitors. Facilities should evaluate potential emissions in accordance with

ANSI/HPS N13.1 to determine the need for stack sampling and/or monitoring.

Other Emergency Instrumentation. Other emergency instrumentation should provide ranges for

all radiation dose rates and contamination levels potentially encountered at the time of an accident.

Normally, dose rate capabilities from a few millirem per hour to a few hundred rem per hour should be

required while capability requirements for the contamination level may range upward from

200 dpm/100 cm2 for alpha contaminants and 100 dpm/100 cm2 for beta-gamma emitters. Performance

specifications for emergency radiological monitoring instrumentation can be found in ANSI N320-1979,

Performance Specifications for Reactor Emergency Radiological Monitoring Instrumentation (ANSI 1975)

and BNWL-1742, Technological Consideration in Emergency Instrumentation Preparedness. Phase II-B -

Emergency Radiological and Meteorological Instrumentation for Mixed Oxide Fuel Fabrication Facilities

(Andersen et al. 1974).

Instrument Calibrations and Testing

Radiation doses and energies in the work areas should be well characterized. Calibration of

instruments should be conducted where possible under conditions and with radiation energies similar to

those encountered at the work stations. Knowledge of the work area radiation spectra and instrument

energy response should permit the application of correction factors when it is not possible to calibrate

with a source that has the same energy spectrum. All calibration sources should be traceable to recognized

national standards. When the work areas have been well characterized, the calibration facility used by the

uranium facility should be set up to represent as closely as possible the work area's radiation fields.

DOE G 441.1-7, Portable Monitoring Instrument Calibration Guide (DOE 1999i) and ANSI N323

provide guidance on radiation monitoring instrument calibration. The reproducibility of the instrument

readings should be known prior to making calibration adjustments. This is particularly important if the

instrument has failed to pass a periodic performance test (i.e., the instrument response varies by more than

20% from a set of reference readings using a check source) or if the instrument has been repaired. The

effect of energy dependence, temperature, humidity, ambient pressure, and source-to detector geometry

should be known when performing the primary calibration. Primary calibration should be performed at least

annually.

Standards referenced in Section 3.5.2 discuss specific performance testing of radiation detection

instruments. Testing procedures in these standards should be used for periodic requalification of

instruments or detailed testing of instruments.

The calibration of photon monitoring instruments over the energy range from a few keV to 300 keV

is best accomplished with an x-ray machine and appropriate filters that provide known x-ray spectra from a

few kiloelectron volts to approximately 300 keV. Radionuclide sources should be used for higher

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