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Asked by anon-306373 on 7 Dec 2021.
Question: how do you make a nuclear reactor
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Imagine that you are boiling water, the nuclear reactor is doing the same thing! We construct a big boiler filled with water, and boil the water using the heat from fuel rods. Then the steam drives a generator to produce electricity.
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Dimitris Samaras answered on 7 Dec 2021: last edited 7 Dec 2021 12:08 pm
A nuclear reactor needs to maintain and contain a chain reaction on a stable and controllable manner. The most common by far, and at the moment only type of reactor that is used for commercial energy generation, is the fission reactor.
A fission reactor uses most likely uranium as fuel. Uranium undergoes fission, splitting into two smaller nuclei, releasing two to three neutrons and heat along the process. The heat produced is taken away from the fuel by a coolant. Worldwide the most common coolant is water; gases can be used instead, such as carbon dioxide (which is what most British reactors utilise at the moment).
This coolant then transfers heat to a secondary water circuit, which boils and becomes steam, which will then be used to rotate turbines. The rotation of these turbines is what will produce electricity (by means of magnets inside a coil, similarly to other rotational power generators and other sources of electricity production from heat – coal, oil, gas, etc.)
To sustain the fission reaction, neutrons have to be slowed down (as they will not produce further splittings in uranium if they remain fast): to that end we use moderators, materials that will decelerate neutrons to allow them to sustain a chain reaction. In water-cooled reactors, the very same water act simultaneously as a moderator. In a gas-cooled reactor (such as those in the UK), graphite is utilised as a moderator instead.
Another vital component is the control rods: these absorb neutrons readily, so by inserting them inside the reactor the power output is reduced – removing them increases power. Suitable materials here are boron, cadmium, and silver, among others.
Last but certainly not least, you would need structural materials such as concrete and steel. These would have to have specific characteristics, so that they can withstand heat and radiation.
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Alex Clyne answered on 7 Dec 2021:
It varies depending on what type of reactor it is – Advanced Gas-Cooled reactors (which are currently operating in the UK) are made up of bricks of graphite (yes, the same material in pencils!). The fuel we put in the reactor (usually uranium) slides in gaps between these bricks. The fuel comes in the shape of pellets stacked on top of each other. All of this is put inside a reactor pressure vessel. These pressure vessels are either made of steel or concrete and are usually very thick, for protection!
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Tom Ross answered on 7 Dec 2021:
A nuclear reactor works similarly to other coal and natural gas reactors – the nuclear fuel gets hot, heats some water which turns into steam and turns a turbine, generating electricity.
So to make a very basic reactor, you would need nuclear fuel (for example uranium), water, and a turbine. In reality this setup wouldn’t work very well, and you would need to add lots of other bits and pieces to control the reaction, but in general these are the basic components of every reactor.
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Caroline Roche answered on 7 Dec 2021:
The first step is to decide what type of reaction you want, fission (what the current power stations use) or fusion (currently just experimental reactors). Then you can choose your reactor type (It can be big like the new one at Hinkley Point C that they are building or smaller like the ones in submarines). The type of reactor you choose will determine what fuel you need and where you build your reactor.
Then you submit lots of paperwork to get approval. You will submit a design and show how you will prove that it is safe. You will also need to show how you will take care of your reactor (it can last for more than 50 years if you take good care of it) and clean up after your reactor once you have finished with it (how is used fuel going to be stored, what will you do with any wastes generated and how will you return the site to what it was before).
Once approved you can start making your reactor.
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Marianne Morris answered on 7 Dec 2021: last edited 7 Dec 2021 6:27 pm
To make a nuclear reactor… you will need some fuel, some neutrons and something called a moderator (which is a material that slows the neutrons down to the right speed for a reaction). If any of these three components are missing, you cannot create a sustainable nuclear reaction.
Only certain metals will work as a nuclear fuel – they need to be ‘fissile’. This means that when a fuel atom absorbs a neutron, it causes the atom to become so unstable that it splits (fissions) into two smaller atoms and, in doing so, releases energy and (very importantly) more neutrons that can go on to cause further atoms to fission and create a chain reaction.
That’s all you need for a reactor – if you want to harness the energy that is released, then you need to build a power station to go with the reactor. The energy produced by the fissions can be used to transfer heat to a boiler full of water. The heated water turns to steam and this drives a turbine very fast. If you have learnt about electricity induction you will know that when a magnetic field is moved inside a conductor it induces an electrical current in the conductor. As the steam turbine spins, it is connected to a generator, which is a fancy name for a device that converts mechanical (rotational) energy into electrical energy, usually by rotating a magnet very fast inside big coils of wire.
On a large scale, this is how we make the electricity that powers everything around us. The only thing that changes is the initial source of heat or energy (e.g. wind, water) that is used to drive the turbine.
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Gavin Thomson answered on 9 Dec 2021:
Several answers have covered the kind of nuclear fission reactors often used in power generation, including in the UK and their basics.
Nuclear Fusion is another class of reactor and that is currently received renewed interest and I think one of the other scientists is doing some materials research. This kind of technology is sometimes referred to in the press as copying the processes that happen in the sun.
I don’t understand so much about fusion but if you’re interested in learning about an area of scientific challenge then thats a good one. For example, part of the requirement is to develop a plasma (the state beyond gas) which I remember means more than a million degrees celsius and then you have to contain it under pressure (magnetic fields are common) and of course extract energy from the reactions. Scientists in the UK have been working on nuclear fusion for decades but it still has decades to go I think. Its pretty interesting to think about the technical challenges they face and how they are attempting to solve them.
Thats a lot of what science is about to me. Problem solving. -
Robert Alford answered on 14 Dec 2021:
I quite like this virtual reality video from EDF to help answer this
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