Instrument Calibrations and Testing - doe-std-1128-98

DOE-STD-1128-98

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-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.

3-23