With so many amazing entries this year, I couldn’t possibly let you miss out on some of the brilliant science writing I received. Here is our first runner-up, Daniel who is just 12 years old and from the UK. He has written about how nuclear reactors work.
How a Nuclear Reactor works
How a nuclear reactor works is very complicated, so I’ll try to explain it as simply as possible. The idea of a nuclear reactor is to use heat and water to create steam to spin a turbine, therefore generating electricity. I am going to focus on 3 different types of reactor: Pressurised water reactors, Boiling water reactors and Pressurised heavy water reactors. I will explain how all of these work in a fun but scientific way.
How does it even work? Imagine microscopic floating balls full of electricity, these are Neutrons, and are packed full to the brim of energy. Then imagine another set of floating balls, these are Uranium atoms. If these collide, then they split and release a tremendous amount of energy. Imagine this as a mission the two have to complete: “Fission is the Mission”. The amount of heat and energy these release (520°F) converts water to steam. The steam is used to power a turbine that generates electricity.
Pressurised water reactors (PWR) work by pumping water from reservoirs into cooling towers where they are cooled down. This water is then pumped into a pipe running into a condenser. This condensed water is pumped through the reactor’s core where it cools the reactor down. Afterwards it is pumped into a turbine that spins it and the energy that this creates generates electricity. The now pressurised water is pumped into a steam generator where it evaporates into steam. But what happens to the rest of the water? The steam is directed back into the condenser where it is recycled.
How a disaster can occur: An incident occurred with a PWR, forcing the surrounding areas to be evacuated. The reactor was operating at 97% when a malfunction in the secondary area of the reactor (condenser area). The coolant temperature going into the reactor began to rise. This caused the reactor to shut itself down automatically, but the pressure relief valve failed to close, not allowing the pressure to be released. The panels in the control room failed to show this. The heat in the reactor built up, damaging it severely. This led to a partial meltdown – where the reactor itself sinks through the ground.
Control Rods: Control rods are used to control stability in the reactor core and keep it calm. They are often made of Boron, Cadmium, Silver or Indium. When these are lowered, they can absorb many Neutrons but still won’t start fission. When the control rods are inserted into the reactor, they can either increase or decrease the power of the Uranium atoms fission. However if they are taken out altogether, then the control room loses the ability to apply the “brakes”. If they are taken out, the power can rocket, steam builds up and ruptures the control rods, therefore a potential nuclear disaster.
Boiling water reactor (BWR): A Boiling water reactor is very similar to a PWR but it boils the water as it goes through the reactors core and is converted into steam that spins a turbine which activates a generator. The steam is then recycled and re-used for the reactor. Pressurised Heavy Water Reactor (PHWR): A Pressurised heavy water reactor functions very similarly to a pressurised water reactor, however it uses heavy water (D2O) to keep the reactor cool and pressurise it to stop it from boiling. The heavy water then evaporates into steam which turns a turbine, activating a generator and generates electricity. The heavy water is then condensed back into a liquid and recycled.
My personal opinion: I have mixed feelings about the use of nuclear power. One side believes it is easy and cheap however, the other tells me that nuclear energy shouldn’t be played with. After all, the effects and aftermath can be devastating. (Note from A Short Scientist – although there have been nuclear disasters in the past, there have been huge improvements in safety. Nuclear power is also a carbon neutral energy alternative).