Masters Theses

Date of Award

5-1998

Degree Type

Thesis

Degree Name

Master of Science

Major

Nuclear Engineering

Major Professor

Laurence F. Miller

Committee Members

Lawrence W. Townsend, Mike Elam

Abstract

This thesis addresses the problem of determining the dose rate that an artifact is exposed to while buried in soil. The determination of this dose rate is critical to obtaining an accurate age estimate for an artifact using the Thermoluminescent (TL) Dating technique. Determining the dose rate requires a two step process involving the measurement of the soil activity, and then calculation of the dose rate from this measured activity. For this paper soil samples taken from the Wickliffe Mound site located in Western Kentucky.

The activity of the soil is measured using a High Purity Germanium (HPGe) gamma spectrometry system. Specifically, the activity of each of the naturally occurring radionuclides (Th-232,U-238, and K-40) are determined. These measured activities are then converted into dose rate factors (DRF's) are then calculated for each of the nuclides in these decay chains. These calculated factors are compared to existing data used for typical dating applications.

The gamma spectrometry measurements resulted in a calculation of soil activity that produced results that are consistent with known data. In addition, the spectra produced by the different soil samples are consistent and in reasonable agreement. The calculation of dose rate factors produced results that are within 10% of previously published data for five out of six calculated DRF's. The exception to this is with the K-40 gamma DRF, which varies 14%.

The results of this paper warrant the conclusion that the use of the equipment and techniques used here would be suitable for dose rate determination of soil. Although the error estimation would seem to be high in some instances, it is within the range of previously published data in the field of Radiation Damage Dating.

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