Lecture 21 - The Next Generation of Nuclear Power
约 800 个字 预计阅读时间 3 分钟
- Speaker: Prof. James Marrow
Background
What are the primary uses of energy?
- Energy consumption
- Electricity generation
Key drivers for energy supply strategy include:
- World economic growth
- Climate change
Energy Consumption
UK per capita energy consumption
Energy inputs: \(125 \text{kWh}/\text{d}\)
- Electrical appliances: \(18 \text{kWh}/\text{d}\)
- Heating: \(40 \text{kWh}/\text{d}\)
- Transport: \(40 \text{kWh}/\text{d}\)
- Losses in conversion to electricity
Electricity Generation
Coal and natural gas are projected to remain significant sources of electricity generation.
World Economic Growth
Energy is a strategic resource and plays a crucial role in global politics.
The global population and economic wealth are forecast to increase.
The global population will continue to rise, driving an increased demand for energy.
Climate Change
It is unequivocal that atmospheric \(\ce{CO2}\) levels are increasing.
In the long term, the Earth's climate will adapt to these elevated \(\ce{CO2}\) levels.
Nuclear Energy
- Nuclear Fission
- Safe, zero carbon
- Challenges include waste management, uranium supply, and the proliferation of nuclear weapons.
- Nuclear Fusion
- Safe, unlimited energy
- No practical applications have been realised to date.
Nuclear Fission
Criticality is achieved when a self-sustaining nuclear chain reaction occurs within a mass of fissile material.
Methods for controlling a nuclear reactor include:
- Moderator: Reduces the energy of neutrons to facilitate the fission reaction.
- Reflectors: Redirect neutrons back into the reactor core.
- Control Rods: Regulate the neutron population to control the reaction rate.
Moderation
The likelihood of fission is governed by the cross-section, which is a function of neutron energy.
- Incident neutron energy - \(E_{0}\)
- Energy after collision - \(E\)
- Mass of the moderating atom - \(A\)
Common moderator materials include:
- Hydrogen: Water (light water)
- Deuterium: Water (heavy water)
- Carbon: Graphite
- Beryllium: Rarely used (cost/toxic)
- Lithium: Molten salt
- Boron: Used as a dopant
Reflection
Reflectors minimise neutron leakage from the reactor core.
- Elastic scattering of neutrons
- Conservation of neutron kinetic energy
Heavy atoms with low neutron absorption cross-sections are ideal.
Examples include graphite, beryllium, lead, steel, and tungsten carbide.
A widely used reactor design is the Pressurised Water Reactor (PWR). In this design, water in the primary loop does not boil; instead, steam is generated in the secondary loop via a heat exchanger to drive the turbine.
Materials Aging
Examples include corrosion, stress corrosion cracking, embrittlement, reheat cracking, swelling, and pellet-clad interactions.
Exposure to irradiation, elevated temperatures, and extended time periods can alter the microstructure and properties of materials.
Accurate prediction, monitoring, and inspection are essential for ensuring safe and economically viable operation.
Fuel ageing influences burn-up, thereby impacting the economic viability of power generation.
Many reactor components can be, and have been, economically replaced or repaired.
Fast Breeders
Fuel breeding involves the production of new fissile material, which can be reprocessed into fuel.
Waste management considerations include:
- Utilisation of a range of fissile metals
- \(\ce{U}\), \(\ce{Pu}\), LWR fuel waste
- Nuclear weapons waste
Each fast breeder reactor generates fuel for subsequent reactor generations.
Alternative Hydrogen Production
- Photoelectrolysis
- Solar-powered photovoltaics
- Electrolysis of water
- Thermochemical water splitting
- Requires temperatures of approximately 1000℃, which can be reduced through chemical cycles.
- Solar and geothermal energy sources
- Nuclear VHTR
- Biomass conversion
- Photosynthesis by microbes (catalytic)
- Hydrogen production from biomass
- Thermal biomass conversion
- Conversion via thermal methods such as pyrolysis or gasification
These processes typically require heat energy or electrical input.
Advanced Reactor Systems
Small Modular Reactors
- 300 MWe to 800 MWe
- Advantages:
- Easier entry to market and financing
- Scope for innovative manufacturing (in-factory)
- Economies of mass production (NOAK) and standardisation
- Faster construction, greater deployability/integration with grid
- Disadvantages:
- Overall economics of scale
- Licensing challenges (currently unresolved)
- Example: Light Water Reactor (LWR), Gas Fast Reactor (GFR), Molten Salt Reactor (MSR), High Temperature Gas Reactor (HTGR and VHTR)
Generation IV Systems
Generation IV systems are anticipated to be operational by 2040.
These systems are crucial for long-term energy security and the hydrogen economy. Fast breeder reactors (e.g., SFR) generate fuel and consume high-level waste, while high-temperature reactors (e.g., VHTR) provide process heat.
Prototypes of Generation IV systems were operational during the 1970s.
Power generation necessitates the development of new materials to ensure economic viability and scalability.
Nuclear Fusion
The fusion of deuterium and tritium is regarded as the most feasible fusion reaction.
Materials within a fusion reactor are subjected to high fluxes of high-energy neutrons.
However, several critical questions must be addressed before nuclear fusion can be practically implemented:
- Is nuclear power different from other forms of energy generation?
- How can the safe and economically viable operation of next-generation nuclear plants be ensured?
- What, ultimately, will be the amount of nuclear waste generated?
- What role will nuclear fission play in the 21st and 22nd centuries?