Instrument Calibrations and Testing - STD-1128-98master0083

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

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 (ANSI, 1975b) and

BNWL-1742 (Andersen et al., 1974).

3.5.3 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. Neutron energy

spectral information is considered particularly important because neutron instruments and

dosimetry are highly energy-dependent.

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

plutonium plant should be set up to represent as closely as possible the work area's radiation

fields. Californium-252 or PuBe calibration sources should be used for work areas that

process plutonium metal and plutonium oxide because their neutron energy distribution is

similar to those compounds. Facilities that process PuF4 should use a PuF4 source. Most

work areas at processing plants are high-scatter areas and thus have significant quantities of

low-energy neutrons. Because it may not be feasible to have sources and scatter geometries

representative of all work locations at the facility, it should be important to determine

specific spectra and correction factors for work locations to correct for the calibration.

Scatter conditions should be taken into account when setting up a calibration facility. The

effect of room scatter in a neutron calibration facility can be significant and may account for

as much as 20% of the measured dose equivalent rate. The Schwartz and Eisenhauer (1982)

methods should be used to correct for room scatter.

ANSI N323 (ANSI, 1997b) provides requirements on the calibration of portable

instruments. 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-

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