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Title: Production of radionuclides in the earth and their hydrogeologic significance, with emphasis on chlorine-36 and iodine-129

Thesis/Dissertation ·
OSTI ID:5542108

Equilibrium radionuclide concentrations are calculated as a function of depth for a variety of rock types. Production mechanisms include fissioning of heavy radionuclides; spallation by cosmic-ray nucleons; capture of neutrons, {alpha}-particles, muons and protons; and photonuclear reactions. Calculations indicate that deep subsurface production of {sup 3}H, {sup 14}C, {sup 85}Kr and {sup 99}Tc is generally below detection but that deep production of {sup 36}Cl, {sup 39}Ar, {sup 81}Kr and {sup 129}I establishes limits to age-dating of water in most rocks. Parameters for estimating production of {sup 10}Be, {sup 22}Na, {sup 26}Al, {sup 32}Si, {sup 41}C and {sup 79}Se are included in appendices. Concentrations of {sup 36}Cl and {sup 129}I in ground water from the Stripa granite, Sweden, were determined by accelerator mass spectrometry. {sup 129}I values range from 1000 to 200,000 atoms/ml, compared to an estimated background concentration in pre-1945 water of 20 atoms/ml. The high levels are attributed to production by spontaneous fission of {sup 238}U in the granite (44 ppm U). The validity of using {sup 36}Cl/Cl ratios as a monitor of deep lithospheric neutron fluxes was tested by measuring the ratios in Cl extracted from Stripa granite. The average ratio agrees with ratios calculated based on rock chemistry and on the measured neutron flux. {sup 129}I and {sup 36}Cl were also measured in uranium ores from the Koongarra and Ranger deposits, N.T., Australia. Samples from the oxidized ore zone contain only 6-23% of the {sup 129}I contents predicted for equilibrium, suggesting preferential loss of {sup 129}I relative to U during weathering. {sup 36}Cl is produced as a result of high neutron fluxes in the ore.

Research Organization:
Arizona Univ., Tucson, AZ (USA)
OSTI ID:
5542108
Resource Relation:
Other Information: Thesis (Ph. D.)
Country of Publication:
United States
Language:
English

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