Portable Survey Instruments --Beta Radiation Response

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiation Protection in Uranium Facilities

6.3.1 Portable Survey Instruments --Beta Radiation Response

The primary exposures of concern when handling bare uranium materials come from the beta

radiation. The accuracy and precision of survey instruments used for measurement of beta radiation

fields depend upon some or all of the following factors:

beta energy response,

angular response of instrument,

source-detector geometry factors, and

detector construction (window thickness, etc.).

6.3.1.1 Energy Dependence

Most commercially-available radiation survey instruments under-respond to beta radiation fields

from uranium. Figures 6-4 and 6-5 show the beta and gamma spectra measured with a tissue equivalent

plastic scintillation. Table 6-6 presents typical survey instrument response to uranium fields specifically. At

best, typical "beta correction factors" (true dose rate/indicated dose rate) are on the order of 1.5 to 2.

This under-response is due primarily to a) the angular response of the detector and b) attenuation of the

dose-rate by the detector window and the sensitive volume of the detector.

Figure 6-4. Meter Readings for a Depleted Uranium Ingot

6-11