L7 - Uranium

Question 1

What is the primary use of uranium?

Answer 1

As fuel for nuclear power generation.

Question 2

What type of uranium is stable in reducing conditions?

Answer 2

Uranous (U⁴⁺), which is relatively insoluble

Question 3

What type of uranium is stable in oxidizing conditions?

Answer 3

Uranic (U⁶⁺), which is soluble and forms stable aqueous complexes and minerals

Question 4

What is the dominant process that concentrates uranium in granitic rocks?

Answer 4

Igneous processes associated with the lithophile behavior of uranium

Question 5

Write the equation for radiometric dating

Answer 5

N=N0⋅e −λt , where N is measured radioactive nuclides, N0 is original nuclides, λ is the decay constant, and t is time.

Question 6

What are the conditions required for uranium to sustain a nuclear chain reaction?

Answer 6

Enriched 235U (>3–4% for reactors, >90% for weapons) and a critical mass.

Question 7

What are the main uranium minerals?

Answer 7

Uraninite (UIVO 2), Pitchblende (UIV 3 O8), Brannerite, Carnotite, and Autunite

Question 8

Which countries are the top uranium producers as of 2021?

Answer 8

Kazakhstan (46%), Canada (10%), and Australia (8%).

Question 9

Which country has the largest identified recoverable uranium resources?

Answer 9

Australia, with 28% of the world’s identified resources.

Question 10

What are the main types of uranium deposits?

Answer 10

Magmatic, magmatic-hydrothermal, sedimentary, unconformity-related, placer, roll-front, and weathering deposits.

Question 11

What are unconformity-related deposits?

Answer 11

Deposits at the boundary of Proterozoic sediments and basement rocks, with hydrothermal fluid circulation at redox fronts (e.g., Athabasca Basin).

Question 12

What is a roll-front deposit?

Answer 12

A deposit formed by oxidizing groundwater interacting with reducing agents, precipitating uranium at a curved redox front.

Question 13

Where are placer deposits commonly found?

Answer 13

In quartz-rich conglomerates like Witwatersrand (South Africa) and Eliot Lake (Canada).

Question 14

Where is the natural nuclear reactor located?

Answer 14

Oklo, Gabon, in a Proterozoic sedimentary basin

Question 15

What are the conditions for natural reactor criticality?

Answer 15

High 235U/ 238U ratio, >10–20% uranium concentration, minimum ore thickness >50 cm, and high water/rock ratios.

Question 16

How long did chain reactions occur in the Oklo natural reactor?

Answer 16

Between 20,000 and 600,000 years

Question 17

What temperature range did the Oklo natural reactor maintain?

Answer 17

Core temperatures below 1,000°C with a gradient of 100°C/m

Question 18

What are the main methods of uranium mining?

Answer 18

Open-pit, underground mining, and in-situ leaching (ISL).

Question 19

What is the primary environmental hazard associated with uranium mining?

Answer 19

Radon gas exposure and radioactive dust.

Question 20

What are the environmental concerns with uranium tailings?

Answer 20

Radiation hazards, groundwater contamination, and ease of airborne dispersion in powdered form

Question 21

What is the enrichment level of uranium for reactor fuel?

Answer 21

3-4% 235U

Question 22

What is the enrichment level of uranium for weapons?

Answer 22

over 90% 235U

Question 23

what is yellowcake?

Answer 23

a concentrated uranium product (ammonium diuranate) containing 70-90% U3O8

Question 24

Why are uranium deposits associated with redox processes?

Answer 24

Uranium changes oxidation states, precipitating at redox fronts, concentrating the element.

Question 25

What geological processes helped form uranium-rich sandstone deposits?

Answer 25

Hydrothermal fluid circulation and the interaction of oxidizing and reducing conditions

Question 26

What insight do natural reactors provide about Earth’s history?

Answer 26

They demonstrate past conditions of uranium enrichment, changes in Earth’s atmosphere, and natural chain reaction physics