Nature`s uncommon elements: Plutonium and technetium

Journal Article · Fri Jan 01 04:00:00 EST 1999 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(98)00282-8· OSTI ID:347940

Curtis, D; Fabryka-Martin, J; Dixon, P ^[1]; Cramer, J ^[2]

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1. Los Alamos National Lab., NM (United States). Chemical Science and Technology Div.
2. Atomic Energy of Canada Ltd., Pinawa, Manitoba (Canada). Whiteshell Lab.

Natural {sup 99}Tc and {sup 239}Pu were measured in ores from the Cigar Lake uranium deposit, in which U concentrations ranged from 0.3 to 55 wt%. Atomic ratios ranged from 1.4 {times} 10{sup {minus}12} to 51 {times} 10{sup {minus}12} for {sup 99}Tc/U and 2.4 {times} 10{sup {minus}12} to 44 {times} 10{sup {minus}12} for {sup 239}Pu/U. Measured concentrations are compared to those expected if the ores had behaved as closed systems with respect to U and its products. Under conditions of secular equilibrium in closed systems, {sup 99}Tc and {sup 239}Pu concentrations are solely a function of the neutron flux, U content, and decay rates. The neutron production rate and physical and chemical parameters that control the in situ neutron flux were measured in several samples. Neutron transport modeling of the sample environs using the MCNP code indicated that about half of the samples showed apparent excesses of {sup 99}Tc and {sup 239}Pu beyond the amounts predicted for secular equilibrium. Although production by neutron-capture on {sup 98}Mo complicates the accuracy of the {sup 99}Tc predictions, the excess quantities nonetheless strongly suggest the redistribution of these elements within the deposit. The failure to observe complementary deficiencies within the deposit suggests that the redistribution processes enriched the elements, removing small proportions of the elements from large uraniferous masses of rock, and concentrating them in smaller, less uraniferous, masses. The consistency of {sup 239}Pu/U and {sup 99}Tc/U ratios in bulk rock suggests that the redistribution processes observed at Cigar Lake are highly localized and in no case result in large-scale losses or gains of these nuclear products from the deposit as a whole.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• OSTI ID: 347940
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 2 Vol. 63; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
ELEMENT ABUNDANCE
ENVIRONMENTAL TRANSPORT
EXPERIMENTAL DATA
GEOCHEMISTRY
NATURAL OCCURRENCE
PLUTONIUM 239
SASKATCHEWAN
TECHNETIUM 99
URANIUM DEPOSITS