Low Carbon Energy Flashcards
What percentage of the world’s electricity is powered by nuclear energy?
9%
What isotope is used in nuclear fission reactors?
Uranium-235
What is the crustal abundance of uranium?
2.7ppm
What minerals can contain uranium?
Zircons and apatite
What are some ores of uranium?
Uraninite (UO2) and pitchblende (U3O8)
What is the primary formation of uranium?
Majority forms during late-stage crystallisation of igneous rocks
What is the secondary formation of uranium?
The oxidation (typically by water) of U4+ ions to U6+ ions, which form uranyl ions (UO2)2+ which are leached and transported through groundwater where it either forms a placer deposit (separation by density) or is precipitated out of uranium and back into a solid (hydrogenic)
When do roll-front deposits form?
With movement through porous rock like sandstone, where dissolution and deposition along a curved front occur
What is in-situ leaching mining?
The injection of solution that oxidises, solubilises and binds the uranium, which is then pumped out (sulphuric acid commonly used)
What is considered a high grade ore of uranium and what is the purification and dynamic treatment process?
Anything >0.1%, it is crushed and ground mechanically before chemically processed with solutions
What is the treatment process for low grade uranium ore?
Acid heap leaching: solution application to large mound of ore, drainage to form pregnant leach solution (PLS), recirculation to improve concentration before chemical extraction, stripping and drying to form “Yellow cake”
What is yellow cake?
Solid obtained uranium containing 75% uranium but only 0.7% U-235, remainder is U-238.
What is the enrichment process for uranium?
Fluorine is added to yellow cake to form UF6, with both isotopes, then they undergo gas diffusion and U-235 moves through a membrane more as it is smaller to increase concentrations this is to form the fuel rod with concentrations of 3.5%
What happens during nuclear fission of U-235?
U-235 collision with a neutron causes it to split into two lighter atoms, and causes the release of two neutrons and large amounts of energy. The neutrons are typically absorbed by the fuel rods.
How long is spent fuel radioactive for?
Over 10,000 years
How much carbon is needed to produce the same amount of energy that 1g of U-235 can produce?
2.5tonnes
What are fissile vs fertile isotopes?
Fissile will undergo fission itself, whereas fertile can be converted by neutron capture to an isotope which is fissile
What is alpha decay?
The release of a helium nuclei (alpha particle), with a decay energy of 3.5-6MeV. They are heavy and highly charged so interact readily with matter, however they can only travel 5cm in air. Occurs in heavy atoms (>200Au)
What is beta decay?
beta decay is the release of an electron (beta particle), β particles have a range of energies a few keV (3H) up to 2-3 MeV (90Y). They have low mass, medium energy. Less damaging (less ionising power) but can travel 3m in air. Occur in lighter, neutron-rich nuclei.
What is gamma decay?
The emission of a higher energy photon (acts as a wave). Can travel very far but low ionising power. Occurs in excited nuclei, commonly after alpha or beta decay.
What is high level waste from nuclear radiation?
Produces radioactivity and heat, from reprocessing spent fuel, nitric acid solutions and glasses.
What is intermediate level waste from nuclear radiation?
High radioactivity but little heat, steel, graphite, concrete, cement and sand, sludges etc from buildings
What is low level waste from nuclear radiation?
Wastes less than 4 GBqs per tonne of alpha activity or 12 Gbq per tonne of beta/gamma activity
Plastics, paper and metal, soils, building materials and plant.
What is very low level waste from nuclear radiation?
Controlled or general landfill depending on volume
