L7 - Uranium Flashcards
What is the primary use of uranium?
As fuel for nuclear power generation.
What type of uranium is stable in reducing conditions?
Uranous (U⁴⁺), which is relatively insoluble
What type of uranium is stable in oxidizing conditions?
Uranic (U⁶⁺), which is soluble and forms stable aqueous complexes and minerals
What is the dominant process that concentrates uranium in granitic rocks?
Igneous processes associated with the lithophile behavior of uranium
Write the equation for radiometric dating
N=N0⋅e −λt , where N is measured radioactive nuclides, N0 is original nuclides, λ is the decay constant, and t is time.
What are the conditions required for uranium to sustain a nuclear chain reaction?
Enriched 235U (>3–4% for reactors, >90% for weapons) and a critical mass.
What are the main uranium minerals?
Uraninite (UIVO 2), Pitchblende (UIV 3 O8), Brannerite, Carnotite, and Autunite
Which countries are the top uranium producers as of 2021?
Kazakhstan (46%), Canada (10%), and Australia (8%).
Which country has the largest identified recoverable uranium resources?
Australia, with 28% of the world’s identified resources.
What are the main types of uranium deposits?
Magmatic, magmatic-hydrothermal, sedimentary, unconformity-related, placer, roll-front, and weathering deposits.
What are unconformity-related deposits?
Deposits at the boundary of Proterozoic sediments and basement rocks, with hydrothermal fluid circulation at redox fronts (e.g., Athabasca Basin).
What is a roll-front deposit?
A deposit formed by oxidizing groundwater interacting with reducing agents, precipitating uranium at a curved redox front.
Where are placer deposits commonly found?
In quartz-rich conglomerates like Witwatersrand (South Africa) and Eliot Lake (Canada).
Where is the natural nuclear reactor located?
Oklo, Gabon, in a Proterozoic sedimentary basin
What are the conditions for natural reactor criticality?
High 235U/ 238U ratio, >10–20% uranium concentration, minimum ore thickness >50 cm, and high water/rock ratios.
How long did chain reactions occur in the Oklo natural reactor?
Between 20,000 and 600,000 years
What temperature range did the Oklo natural reactor maintain?
Core temperatures below 1,000°C with a gradient of 100°C/m
What are the main methods of uranium mining?
Open-pit, underground mining, and in-situ leaching (ISL).
What is the primary environmental hazard associated with uranium mining?
Radon gas exposure and radioactive dust.
What are the environmental concerns with uranium tailings?
Radiation hazards, groundwater contamination, and ease of airborne dispersion in powdered form
What is the enrichment level of uranium for reactor fuel?
3-4% 235U
What is the enrichment level of uranium for weapons?
over 90% 235U
what is yellowcake?
a concentrated uranium product (ammonium diuranate) containing 70-90% U3O8
Why are uranium deposits associated with redox processes?
Uranium changes oxidation states, precipitating at redox fronts, concentrating the element.
What geological processes helped form uranium-rich sandstone deposits?
Hydrothermal fluid circulation and the interaction of oxidizing and reducing conditions
What insight do natural reactors provide about Earth’s history?
They demonstrate past conditions of uranium enrichment, changes in Earth’s atmosphere, and natural chain reaction physics
