Field Tests of a Portable Tissue Equivalent Survey Meter for Monitoring Mixed Beta/Gamma Radiation Fields.

摘要

A portable radiation survey meter that provides a tissue equivalent response to photons and beta particles has been designed and field tested. The detector is a very thin plastic scintillator that closely simulates the actual geometry and scattering properties of the relevant skin tissues. The meter reads out the D(0.07) dose rate directly, and indicates the tissue dose rates at other depths with the use of tissue equivalent filters of appropriate thicknesses. Data are presented which compare the D(0.07) and D(10) dose rates recorded by the Tissue Equivalent (TE) survey meter with dose rates recorded by two commercial ion chamber meters for a number of laboratory and field sources. Most commercial ion chamber meters fail to respond adequately to the extreme off-axis beta particles from extended beta sources, and hence require the application of large beta correction factors to change the instrument reading to the true D(0.07) dose rate. The tissue equivalent survey meter exhibits an angular response to beta particles that is very similar to the angular response of an extrapolation chamber. Consequently, there is close agreement between the TE meter and extrapolation chamber readings for a wide variety of beta and mixed beta/gamma radiation fields. D(0.07), D(3), and D(10) dose rates, measured with the INEL TE meter at a number of typical work stations, are presented.