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Date of Award

6-1980

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

Supervisor

Dr. Henry P. Schwarcz

Co-Supervisor

Dr. Derek C. Ford

Abstract

The mining operations at the Greyhawk Uranium Mike began in 1956 and were discontinued in 1959. As a consequence of the mining opeartions, a waste rock pile (pegmatite granite and gabbro) was developed at the site. These rocks have subsequently undergone weathering processes and consequently introduced leachate into the aquifer.

The uranium content and uranium isotope ratio (²³⁴U/²³⁸U) of the Greyhawk ground waters were measured utilising the analytical methods of isotope dilution and alpha- particle spectrometry. Uranium contents range from about 1.2 to as high as 380 ppb. Most samples at deep sampling points (>7m) are usually anomalously high. This suggests that a plume of uranium-rich water possibly emanating from the waste rock source is migrating in the deeper part of the aquifer. The high uranium content in the waters at greater depths may also be attributed to leaching of the buried bedrock surface by acid water of the waste dump. This U-rich water also has distinctly higher ²³⁴U/²³⁸U ratios. The samples at the water table closest to the waste rock source also showed quite significant concentration of uranium. Uranium in these waters occurs predominantly as stable and soluble uranyl carbonate complexes; part of the dissolved uranium is taken by the porous medium as it passes through, as shown by high concentrations of leachable uranium on the sediment of the aquifer.

Generally, the Greyhawk ground waters have a relatively low ²³⁴U/²³⁸U ratio which ranges between 0.95 and 1.85. Most samples have U ratios between 1.00 and 1.30. Migration of ²³⁴U-enriched water was observed at intermediate and bottom depths of the aquifer. The spatial distribution of isotope ratios in the aquifer indicates the migrating path of the contaminants emanating from the waste rock source. The enrichment of ²³⁴U over ²³⁸U is probably due to preferential leaching of ²³⁴U from the waste rock as well as from the bedrock.

The thermal neutron activation-delayed neutron counting technique is also applied to the analysis of uranium content in the water. The technique is non-destructive, rapid, moderately accurate and precise and appears satisfactory for uranium prospecting purposes.

The possibility of applying combined fission track and alpha track counting technique to determine isotopic ratios (²³⁴U/²³⁸U) is investigated in this programme. The ratios obtained by this technique are promising and generally are in good agreement with those determined on an alpha-particle spectrometry. This technique has a great potential in the determinations of ²³⁴U/²³⁸U ratio in natural water. However, some improvements on the technique are still needed to make the method more reliable, quantitative and rapid.

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