Week 3- Energy and environmental pollution Flashcards
1
Q
What is significant about U-235?
A
It’s fissile and is used for fuel for nuclear power plants
2
Q
Biggest majority of costs for nuclear power plant construction?
A
Home office services
3
Q
% of naturally occurring U that is U-235
A
0.7%
4
Q
Main element used in nuclear power generation?
A
Uranium
5
Q
Main ores containing Uranium?
A
Uraninite (UO2) and Carnontite (Potassium and Uranium Vanadate)
6
Q
What is used to separate ores containing uranium from impurities?
A
Crushing annd flotation
7
Q
Stages of Uranium abstraction
A
- Mining
- Refining
- Enrichment
- Fuel Fabrication
- Reactor use
- Reprocessing
8
Q
2 main oxidation states of uranium ores?
A
+IV and +VI
9
Q
Solubility of +IV oxidation vs +VI oxidation?
A
+IV oxidation is very insoluble. +VI is very soluble
10
Q
What oxidation state are most minerals in?
A
+IV oxidation - insoluble
11
Q
How to extract Uranium?- Refininf
A
- Oxidation (air or bacteria)
-UO22+= extracted using sulphuric acid - Organic solvent used to separate uranium
12
Q
How is Uranium precipitated?- Refining
A
By increasing the pH to 6.5-8
13
Q
Tailing wastes:
A
Fine-to-coarse particles in a water slurry; contains radioactive elements
14
Q
Environmental impact of Radium (Ra-226)
A
Highly soluble and can leach out of the waste materials
15
Q
Environmental impact of Radon (Rn-222)
A
Gaseous and can diffuse out of the waste materials
16
Q
What do waste waters contain?
Mining/Nucleur
A
- Ra-226
- Dissolved heavy metals (non-radioactive) and sulphuric acid
17
Q
Enrichment of Uranium
A
235U = 3%
238U = 97%
18
Q
Enriched Uranium Fuel Rod
A
Sent to nucleur power
plants to generate power
19
Q
Enriched uranium- Enrichment
A
A type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation.
20
Q
What does THORP stand for?
A
Thermal oxide reprocessing plant
21
Q
Process of reprocessing fuel rods?
A
- Storage of fuel rods under water for 6-12 months
- Fuel rods are chopped into 3-5 cm pieces (Spent Fuel)
22
Q
Types of waste produced from Spent Fuel
A
- Cladding (nitric acid)
- Fission Products (hydrocarbons, radioactive phosphates)
- Nitric acid: Hydrocarbons; radioactive phosphates
23
Q
2 products of spent fuel
A
- Uranyl nitrate
- Plutonium nitrate
24
Q
How can uranyl nitrate and plutonium nitrate be reprocessed?
A
Purification and conversion to oxide
25
Separation of U and Pu from fission products?
- Extractant (TOGDA) added to mixture of organic solvent and aqueous solution
- Uranium and plutonium go into the organic layer
- Fission products stay in the
aqueous layer
26
Intermediate level liquid waste (ILLW)
* <4x104 GBq/m3
* <0.5% of uranium and <0.2% of plutonium that has been recycled
27
High level liquid waste (HLLW)
* ~107 GBq/m3
* <0.5% of uranium and <0.2% of plutonium that has been recycled
28
High level solid waste (HLSW)
* cladding from the fuel rods etc. (doesn’t dissolve during reprocessing)
29
Which type of waste produces most of the radioactive hazard?
The lowest volume waste- HLW
30
Current storage procedure of intermediate level liquids?
Neutralised and stored on-site in steel canisters
31
Vitrification
Encased in glass
32
Current storage procedure of high level liquid waste?
Vitrified and is stored on-site in steel canisters
33
Current storage procedure of high level solid waste?
Stored on-site in steel canisters
34
Considerations that need to be made when considering deep disposal?
- Geological stability
-Absence of large fractures
- Impermeability of the repository matrix to surface water
-Negligible groundwater circulation in the vicinity of the repository
- Good heat conductivity of the repository solid matrix
35
Deep disposal UK- involving a multibarrier containment system:
- physical (steel containers/cement grout)
- chemical (cement backfill)
- geological (stable rocks
36
Physical containment- deep disposal
Interim surface storage in steel or concrete boxes
37
Swiss cheese model:
Using physical chemical and geological methods in combination to account for failure at each phase
38
Geological isolation- deep disposal
No backfill
39
Chemical conditioning- deep disposal
- Alkaline sorbing
- Cement based backfill method
40
Geological containment- deep disposal
Low water flow and physical stability
41
Issues with deep disposal UK
Highly fractured rock (Borrowdale Volcanics) meaning potential movement of water through repository
42
Deep disposal method - Sweden
Based on 3 protective barriers- encapsulated in copper, then places in crystalline basement embedded in bentonite clay and sealed
43
Waste Isolation Pilot Plant (WIPP)
Waste contained underneath salt bed in steel canisters however the salt bed is not water free.
44
What is Radiosynthesisλ
When organisms these organisms appear to perform radiosynthesis, using pigments such as melanin to convert gamma-radiation into chemical energy
45
Half Life Equation
A=λN(t)
46
What is alpha emission?
4He (2 protons and 2 neutrons)
These result in a mass number change
47
What is Beta emission?
Electrons – atomic number changes but not mass number
48
What is the biological half-life of radiocaesium in humans?
The biological half-life in humans is about 90 days, depending on age, diet, and metabolism.
49
How does radiocaesium return to the atmosphere?
It can be resuspended as dust particles during wind erosion, agricultural activities, or forest fires.
50
What role does potassium play in radiocaesium uptake?
Potassium reduces plant uptake of radiocaesium because both are chemically similar and compete for the same uptake channels.
51
How does radiocaesium enter soils?
Radiocaesium deposits onto soil through atmospheric fallout. It binds strongly to soil particles, especially clay.
52
What is the primary atmospheric pathway for radiocaesium?
Radiocaesium can be released into the atmosphere and transported long distances before depositing on land and water via precipitation
53
What type of soil particles most strongly adsorb Cs-137?
Clays, especially those with high cation exchange capacity (CEC) like illite, vermiculite, and smectite, are particularly effective at adsorbing Cs-137.
54
Why do clays have a strong affinity for radiocaesium?
Clays have negatively charged surfaces that attract positively charged ions (cations) like Cs⁺. Cs-137 is adsorbed onto these surfaces, especially at specific frayed edge sites (FES).
55
What are Frayed Edge Sites (FES) in clays, and why are they important?
FES are high-affinity sites on weathered clay minerals where potassium and cesium ions are selectively adsorbed. These sites tightly bind Cs⁺, making it less bioavailable
56
Can radiocaesium become permanently fixed in soil?
Over time, Cs-137 can become fixed in interlayer sites of certain clays, becoming practically non-exchangeable and largely immobilized.
57
How does Radioceasium mobilise during winter/spring rainfall events?
Rain flushes immobilised Cs137 in clays which are then up taken into grasses. Cs137 uptake is mediated by competition with K+ ions
58
How can climate change result in the continued impact of legacy radionuclides in the environment?
Forest fires can alter soil organic matter and facture clay minerals
This leads trapped radionuclides to be susceptible to being washed out with rain
Radionuclides can also be suspended and transported regionally through thermals and atmospheric currents
59
What is peak demand in electricity supply?
It’s the highest level of electricity demand in a given period, such as during evenings or extreme weather.
60
What does intermittent mean in the context of energy sources?
It refers to energy sources like solar and wind that don’t generate electricity continuously due to changing environmental conditions.
61
What are the stages of nuclear processing?
Mining → Refining → Enrichment → Reprocessing → Disposal
62
What happens during the mining stage of the nuclear fuel cycle?
Uranium ore is extracted from the earth, typically from open-pit or underground mines.
63
What radioactive waste is produced during mining?
Tailings – leftover radioactive material and rock, which can contaminate soil and water.
64
What occurs during the refining stage?
Uranium is oxidised from insoluble U(IV) to soluble U(VI) (UO₂²⁺) using air or bacteria.
Sulphuric acid extracts UO₂²⁺ into solution.
An organic solvent separates uranium from other metals.
Uranium is precipitated by raising pH to 6.5–8, then heated to produce purified uranium oxide (yellowcake).
65
What is the goal of the enrichment stage?
To increase the proportion of U-235 in uranium for use in reactors (from ~0.7% to 3–5%).
66
What waste is produced during enrichment?
Depleted uranium (U-238 tails) and chemically contaminated materials.
67
What is reprocessing in the nuclear fuel cycle?
The chemical treatment of spent fuel to recover unused uranium and plutonium.
68
What radioactive waste comes from reprocessing?
High-level liquid waste, fission products, and contaminated cladding.
69
What types of disposal are used for nuclear waste?
Surface storage (temporary), and deep geological disposal (permanent).
70
Name four barriers used in the multi-barrier concept.
1. Waste form (glass/ceramic)
2. Engineered containers (e.g., copper)
3. Buffer materials (e.g., bentonite clay)
4. Stable host rock (e.g., granite)
71
Is Thorium-232 (²³²Th) fissile or fertile?
It is fertile, meaning it can absorb a neutron and convert into a fissile isotope (Uranium-233).
72
How does Thorium-232 become a fissile fuel?
²³²Th + n → ²³³Th
²³³Th → (β decay) → ²³³Pa
²³³Pa → (β decay) → ²³³U (fissile)
²³³U undergoes fission, releasing energy and neutrons.
73
What are the advantages of using Thorium (²³²Th) as a nuclear fuel?
More abundant than uranium (3× more than ²³⁵U)
Produces less plutonium and waste
Reduces long-term storage needs
Many thorium reactors use non-water coolants, allowing higher efficiency
74
What are the disadvantages of using Thorium (²³²Th) as a nuclear fuel?
Requires expensive testing and licensing, needing strong business and government support
Higher fuel fabrication and reprocessing costs than traditional reactors
Uranium-232 is produced, emitting gamma rays and potentially enabling nuclear weapons development
75
What is the main advantage of using lithium-ion batteries for grid-scale storage?
Lithium batteries have a high energy density, fast charge/discharge times, and are currently the most efficient and widely deployed option for storing electricity on a large scale.
76
What are the environmental impacts of using lithium-ion batteries in grid-scale storage?
Mining for lithium, cobalt, and nickel creates environmental degradation and pollution.
Toxic waste is produced during the manufacturing and disposal of batteries.
Carbon footprint from mining and transportation adds to environmental damage
77
What is the economic challenge of using lithium-ion batteries for large-scale storage?
The initial cost of production and raw materials (lithium, cobalt) can be high.
Supply chain issues and resource limitations can increase prices over time.
78
How can lithium-ion battery storage benefit the economy despite its environmental costs?
It can lower energy costs by providing efficient peak shaving and grid stability, reducing reliance on fossil fuels.
It provides new business opportunities in battery production, installation, and maintenance.
79
How does grid-scale energy storage help with renewable energy integration?
It allows intermittent energy sources like solar and wind to be stored when they generate excess power and released when needed, improving grid reliability and reducing fossil fuel dependence.
80
What is the vanadium redox flow battery (VRFB)?
It’s a type of rechargeable battery that uses vanadium ions in a liquid electrolyte to store and release energy, making it ideal for large-scale energy storage applications.
81
Why is vanadium important in energy storage?
Vanadium redox flow batteries can store large amounts of energy over long periods.
They are scalable, have a long cycle life, and can be used for grid stabilisation.
They are non-toxic and safe compared to some other energy storage solutions.
82
Why are VRFB batteries useful?
They are
better at delivering a consistent amount of
power over significantly longer periods.
83
What are the advantages of vanadium redox flow batteries (VRFBs) over lithium-ion batteries?
Longer cycle life (can last 10,000+ cycles)
Scalable for large storage systems
No degradation from deep cycling
Safe and non-flammable, unlike lithium-ion batteries
84
What are some challenges of using vanadium in energy storage?
High cost of vanadium can make VRFBs more expensive than other energy storage systems.
Limited supply of high-purity vanadium can constrain widespread adoption.
85
What is the chemical property of vanadium that makes it useful in batteries?
Vanadium can exist in multiple oxidation states (V²⁺, V³⁺, V⁴⁺, V⁵⁺), allowing it to store energy in redox reactions, which is key for the functioning of vanadium redox flow batteries.
86
How is Lithium Brine formed
Formed in Bolivian salt flats from the evaporation of mineral rich groundwater (from volcanic rocks) concentrating lithium groundwater and other salts in shallow subsurface layers over time
87
How is lithium extracted from lithium brine?
Lithium brine is pumped to the surface and left to evaporate.
It is then filtered and placed into another evaporation pool for 12-18 months.
Lithium carbonate can then be extracted
88
Cons of lithium extraction from lithium brine
- Land use
- High water usage
- CO2 emissions
- Removes potential geothermal water
- Toxic chemicals
89
Cons of secondary mineral use in batteries?
Generates more tailings - mining globally produces 250m3 of tailings
Socially- thousands die due to damage of mining and have been displaced
90
Rio Doce dam failure- environmental impact
* Extensive river pollution
* Habitat destruction
* Long term ecological harm to Rio Doce basin
91
Rio Doce dam failure- health impact
Exposure to contaminated water/soil= increased risk of diseases
92
Rio Doce dam failure- Economic consequences
Local economies disrupted e.g. fisheries/tourism/agriculture
93
Geopolitical and social justice implication of trace metals?
Mining of CO- modern slaver/child labour
PO4 minerals in geopolitically unstable regions
94
Methods of metal recovery for Lithium batteres
Pyrometallurgy- relies on combusting Li material in furnaces >1000 C
Hydrometallurgy- recovers desired metals via leaching in acid/basic aqueous solution
Biometallurgy
95
What is the solution to unreliability of renewable energy sources ?
Grid scale storage
96
Direct recycling of LIBs
Direct reuse of the cathode/anode a=material from electrodes of spent LIBs after reconditioning
97
Identify the two primary sources of lithium-ion battery materials for recycling.
Sources: Defective scrap material from battery manufacturing (e.g., off-spec cathode powder, trimmings).
End-of-life (EoL) batteries (e.g., "dead" batteries from consumer electronics, EVs, workplaces)
98
Describe the waste streams generated by LIB recycling.
- Black mass
- Copper and aluminum foils
- Separators
- Other plastics
- Steel canisters
- Electrolyte
- Wastewater
- Slag
- Toxic gases: From pyrometallurgy (e.g., dioxins, furans) or electrolyte vaporization.
99
What is the role of pretreatment in LIB recycling, and what waste streams are produced?
Role: Discharges and separates batteries for safe material recovery.
Waste Streams: Black mass, Cu/Al foils, plastic separators, steel casings, electrolyte vapors, conductive solution waste.
100
What are the environmental and health risks of mismanaging LIB waste streams?
Risks: Electrolyte vapors (flammable/toxic), black mass (heavy metal contamination), wastewater (acid pollution), slag (leaching), toxic gases (carcinogenic).
Mitigation: Proper storage, regulated recycling, universal waste standards.
101
Chemicals generated from landfill fires associated with LIBs
HF,SO2,CO,VOC
102
Why is HF so toxic?
Reacts with Ca in the blood
103
Technical solutions to managing Li battery waste fires?
- Complete discharging= no excess of energy, immobilisation of Cu on Al foil
- Removal of flammable electrolyte from battery= reduced fire risk
- Using additional liners (e.g. bentonite clay) capab;e of binding heavy metals meaning no transport through landfill layers
104
Overall what kind of loop needs to be created to manage Li battery hazards?
Closed loop system
105
How do VRFBs work?
They use ion redox reactions in separate electrolyte tanks with a membrane separating anolyte/catholyte
106
What are VRFBs suitable for?
Large scale energy storage
107
Efficiency of VRFBs?
65-85% round trip efficiency.
>10000 life cycles with minimal degradation
108
Negative Environmental impact of VRFBs?
- Sulphuric acid is a risk
- Vanadium mining can lead to habitat destruction , water contmaination and GHGs
- Potentially toxic to aquatic organisms and mammals
109
Positive Environmental impact of VRFBs?
- Vanadium electrolytes= recyclable and reusable
- Carbon footprint= lower impact than LIBs due to longevity and risk
