Masters Theses

Date of Award

12-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Nuclear Engineering

Major Professor

Laurence F. Miller

Committee Members

Peter Groer, Dave Simpson

Abstract

Criticality accident personnel dosimetry involves the evaluation of high doses in mixed fields of gamma rays and neutrons. Those who work in areas where there is potential for a criticality accident or other extremely high neutron doses need dosimeters, such as thermoluminescent dosimeters, capable of measuring doses associated with these scenarios. In order for a dosimeter to be used in these areas, it must be characterized for accident or high level neutron dosimetry. Panasonic thermoluminescent dosimeters (TLDs), using lithium tetraborate, have been characterized for accident and high level neutron dosimetry.

The characterization of these dosimeters includes calculating the dosimeter's response to neutrons, determining the dosimeter's response to various possible accident scenarios, and evaluating TLD's response at high doses.

An accurate determination of neutron dose is complicated by the fact that dose per source neutron is a strong function of energy. Correction factors for dose and for the dosimeter's response are obtained for 115 different spectra, and these effects are incorporated into a single spectral correction factor (SCF) for each spectrum. These SCFs should be improved, however, to correct for neutrons scattered from the body. Also, a linear combination of element responses to bare, D2O-moderated, and polyethylene- moderated californium-252 and americium-241/beryllium are used to obtain some spectral information from any unknown spectrum.

Since accident dosimetry involves extremely high doses, the element responses have been tested for linearity from one to one thousand rad with D2O-moderated 252Cf. Corrections for element responses due to doses above ten rad have been determined.

Results from this study demonstrate that Panasonic dosimeters, using lithium tetraborate, can be used by personnel who work in areas where there is a possibility for a criticality accident.

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