Comparative investigation of airborne and ground-based radiometric survey techniques
Date
2014-03-05
Authors
Larkin, James Francis Shenton
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Abstract
An investigation was undertaken to compare airborne and ground-based
radiometric survey techniques and to compare and contrast their relative merits
and how they can be used in determining the environmental distribution of
environmental radioisotopes, particularly those in the decay chains of 238U, 232Th
and 40K.
Before a detailed investigation was done of the survey techniques, it was
necessary to look at the underlying physical principles of detection of ionizing
radiation and the types of detector that are generally used in these different types
of survey techniques.
Having looked at the physics of detection, a detailed examination of the potential
distribution of these environmental radioisotopes was undertaken.
In these surveys, an assumption is often made, that the daughter isotopes in a
decay chain are in secular equilibrium with one another. This assumption was
examined and the various possible ways in which secular equilibrium could break
down were considered, these included looking at biological, meteorological and
chemical processes.
Only after all the influences on assumptions used in these survey processes and
the physical limitations on the measurements taken during surveys were
considered, was a comparison made of a set of airborne and ground-based
measurements taken at a chosen survey site compared. These measurements
compared uranium, thorium and potassium activity concentrations, which had
been determined by the two survey techniques, and a correlation was found
particularly when the uranium measurements were examined.