Nuclear Power Structure, Uses & Future

Nuclear PowerStructure, Uses & Future By Jack Percival

The Process

Inside the Fission Reactor • U-235 is usually main reactant in the core • U-238 makes up majority of mass, but very little of energy directly (about 95-98% of mass is U-238) • U-238 can absorb a neutron and through series of β- decays, will become Pu-238 • Pu-238 is a fissile element and can also be used in core • Products of Fission are always radioactive • They contribute some extra energy to the core when they decay • Also represent the main problem with waste

The Fission Process

Internal Structure

Overall Structure

In detail: Moderators • Reactions are made possible by moderators • They absorb the Kinetic Energy from the neutrons through elastic collisions • This means they are slow enough to cause more fission • Key ideas for a good moderator: • High Density Chemically Stable • Low Atomic Weight High Boiling Point • Low Neutron Absorption Inexpensive • For these reasons there are 3 typical moderators • Graphite, Light Water, and Heavy Water • Light water is most common because it fits all of the properties the best while being the cheapest

In detail: Control Rods • Have absorption range similar to the output of core • They can been move up and down in order to control the absorption • This takes away neutrons from being to react with uranium in core • This slows down fission rate, or can completely shut down the core in an emergency • As the neutrons are absorbed they cannot go on to react- this is the control mechanism for the reactor

In detail: Steam and Water • Reactions heat the water which is being pumped into the reactor • This is then passed close to water not under pressure, which turns into steam • This prevents all the water becoming radioactive • The coolant water is usually from the nearby water sources, sometimes the sea • This steam drives the turbine • The turbine is used to produce electricity

In detail: Containment & Safety • Core will automatically shut itself down once a temperature range is breached • Control Rods are inserted to start • Moderator is then “poisoned” by injecting boric acid • Heat exchangers are used to prevent any radioactive material from escaping • Shell around core strong enough to withstand a full airline collision and even a light missile attack • Not even severe earthquakes have been able to crack these shells

Advantages & Disadvantages

Nuclear Power: Advantages • Nuclear power costs comparatively little in ongoing costs • Does not produce smoke or carbon dioxide, only stream, so it does not contribute to the “greenhouse effect”. • Produces huge amounts of energy from small amounts of fuel. • Produces small amounts of waste. • Reliable

Nuclear Power: Disadvantages • Although not much waste is produced, it is very, very dangerous. It must be sealed up and buried for many years to allow the radioactivity to reduce to a safe level • Nuclear power is reliable, but a lot of money has to be spent on safety - if it does go wrong, a nuclear accident can be a major disaster. • Very expensive set up costs and lengthy process • Seen as a possible terrorist target • Has a “NIMBY” effect • Very expensive to decommission • Long payback time • Not harnessing the true energy from the process – relatively inefficient • Non-renewable fuel supplies

Nuclear Fusion: The Future

Nuclear Fusion: The Basics • Stellar nuclear fusion 4H →He • High Energy production • Nuclear fusion power uses Deuterium and Tritium isotopes of Hydrogen

Nuclear Fusion: Today • Whilst a reactor is being built in France, high scale power production is still a long way off • Fusion requires conditions of a very high temperature and pressure, similar to those found in the core of the sun • These situations are near impossible to produce on earth, therefore scientists are looking for a solution – Cold fusion • Whilst this has been done, it has only been produced in small amounts, not enough for large scale power production

Thank You For Listening

Nuclear Power Structure, Uses & Future