Nuclear Fuel
Civil nuclear power is electric generated in a nuclear reactor from a fissionable metal such as uranium. Uranium has 92 protons and 146 neutrons, totalling 238 in total thus is called U-238.
Within each atom’s nucleus a “nuclear reaction” occurs when neutrons smash into the nucleus of the uranium atoms, splitting apart the nuclear bonds to release energy. These split roughly in half, releasing energy and neutrons in the process.
Inside the fuel we observe an exothermic (exo = giving out; thermic = of heat) chain reaction, producing significant amounts of heat which can be harnessed. The neutrons ejected can go on to sustain what what we call a chain reaction by the fission of more atomic nuclei.
Most nuclear fuel comes from uranium – as ceramic uranium dioxide pellets which are contained in metal rods inside the core of the reactor. The reactor produces energy by splitting the uranium atoms, and when most of the uranium atoms have been split, the residual material is removed from the reactor and stored in water pools to displace the heat generated from the waste and to protect employees from the radiation.
How it Works
One of the fundamental laws of nature is that energy cannot be made or destroyed, just transformed from one form into another. In the reactor, the fuel generates heat, then either water or gas is pumped through pipes around the reactor to take the heat away, and this hot gas then heats water to make steam. The heated water becomes highly pressurised in the pipes, and powerful enough to turn an axle with a coil on it. When this rotates between large magnets it moves electrons in the copper wire placed within that magnetic field and the result is an ‘alternating current’ of electricity in the copper wire, enough for distribution.
So, above we see, from start to finish, the energy conversion is from nuclear in the fuel, to heat in the reactor, to mechanical in the generator, to electrical in the transformer. Some of this dissipates by way of friction etc along the way, which means that a nuclear power plant will work with an overall energy efficiency of around 40% max.
Modern nuclear power stations use similar turbines and generators as conventional power stations but for a more explanation of the technical details, see How a nuclear energy plant works | Orano.
Nuclear energy:
Pros
- ‘High density’ energy source: produces a million times more energy than fossil fuels due to the tiny size of the nucleus from which the energy is obtained
- Tiny footprint in terms of fuel, technology requirement and land requirement
- Does not create pollutants such as smoke or carbon dioxide
- Produces small amounts of well managed waste
- Reliable, with an average capacity factor of 92%, necessary for ‘base load’ electricity supply
- High return on investment long term, ideal for pensions
Cons
- Due to public misapprehension and fearmongering, a lot of money has to be spent – even wasted on meeting strict, even non evidence based commissioning, operational & decommissioning safety criteria
- Governments are put off by high start up cost of new builds and reluctant to invest in long term projects
- Cultural shift is difficult because other methods of generating energy provide more jobs due to the high life cycle impact
Interesting facts
Nuclear power is generated using Uranium, a metal mined in various parts of the world. The first civil nuclear fission reactor had to be based on uranium-235, because no other fissile material exists in nature.
As an electricity source, civil nuclear power has been viable only in the last 60 years and currently supplies 11% of the world’s electricity needs.
It must be stressed that the process and technology to produce an atomic bomb is now very different from the production of civil nuclear power. Uranium processed for electricity generation is not useable for weapons. Many countries have a civil nuclear programme but no weapons programme.
Yet because first nuclear power plant for electricity in the UK was effectively a by-product from the production of man-made weapons grade materials used in nuclear arms, many people are still mistrustful towards the nuclear industry.
Some military ships and submarines have nuclear power plants for engines.
The People’s Republic of China has initiated a research and development project in the use of thorium fuel instead of uranium, which has potential non-proliferation and economic advantages, despite significant design challenges.
Further references:
What is nuclear energy, and how is nuclear power made? | EDF