Masters Theses

Date of Award

12-1997

Degree Type

Thesis

Degree Name

Master of Science

Major

Nuclear Engineering

Major Professor

John T. Mihalczo

Committee Members

L. F. Miller, B. R. Upadhyaya, T. E. Valentine

Abstract

A method has been developed and successfully applied to measure uranium deposits in process gas piping at a former uranium enrichment plant. No apriori information other than material composition was required in order to accurately determine the deposit distribution or density. The density of uranium is directly related to its hydration which has significant nuclear criticality safety impacts for large deposits. A 252Cf source was used that provides two independent and simultaneous measurements in order to characterize the deposit. The first measurement was a transmission measurement using high energy fission neutrons, and can be shown to be independent of the deposit hydration and insensitive to geometrical effects of the deposit location with respect to the source and detectors. The second measurement was a gamma ray transmission measurement whose characteristics are a function of the deposit thickness and hydration. Using the deposit thickness from the neutron measurement, the second measurement was then used to determine the deposit hydration. Measurements used to determine the spatial profile of the deposit indicated a volume of 195,000 cm3, yielding a deposit mass of 978 ± 37 kg of uranium based on an average H/U of 3.4 ± 0.25, where the uncertainty is the standard deviation of the mean. Measurements showed that the deposit had adhered to the top of the pipe in some locations contrary to expectation, and was later verified by an intrusive view into the pipe with a fiber optic camera. At the time of the intrusive look estimates of the H/U ratio based on the color of the deposit were 3.0 to 3.5, closely correlating the measured results.

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