Question: what research have you done to develop a clean and safe energy source for the future

Luke Humphrey answered on 15 Mar 2022:

Hey ZaynabP, I work for UKAEA: a public sector (i.e. government) research institution. We are researching fusion energy: the process which powers the stars. Put simply, if two atoms collide with enough speed, they fuse together to make a larger atom, and often release energy (depending on the ingredients). This happens in the core of stars, releasing the energy required to stop the stars from collapsing under their own weight. The reason stars can remain stable for so long is because there is a lot of energy released for a tiny amount of hydrogen fuel. However, hydrogen only fuses when the atoms collide with enough force, which means either high pressure or high temperature. The stars use gravity and their immense scale to create conditions for fusion, but if we want to do it on earth we need an alternative method.

The reason we want to use fusion to generate electricity is because it does not emit carbon dioxide, like burning bio or fossil fuels, but it can generate a lot of energy efficiently and reliably unlike classic renewables like wind and solar power which rely on the weather being suitable. In the future, we will have a mix of fusion and renewables, but hope to stop using fossil fuels and nuclear fission. Note that both fission and fusion are nuclear power sources because they generate energy from nuclear reactions. However, fusion is much safer and more desirable than fission for a few reasons:
1. If something goes wrong like an earthquake, a fusion reaction will naturally cool down and become an inert (harmless) gas, wheras a fission reaction can “runaway” into a chain reaction which can be extremely dangerous.
2. Fusion only creates a small quantity of radioactive waste, which can be stored sustainably in lead while we wait for it to become safe. Fission produces a much larger quantity of radioactive waste, and that waste remains radioactive for 100s of times longer, making it unsustainable to store.
3. The elements required for fusion are far more abundant on Earth than the rare elements required or fission, and are generally safer to handle.

Specifically, we are developing a method of nuclear fusion called “magnetic confinement”. When you heat a gas enough, it can become a “plasma”, the fourth state of matter alongside solids, liquids, and gasses. Plasmas are similar to gasses, but the electrons are no longer bound to their atoms, which means particles in a plasma are “charged”. Importantly, this means we can control them using magnets. We use a large device called a “tokamak”. This is a donut-shaped reactor which uses extremely strong magnets to confine a hydrogen plasma in a ring shape. The magnets repel the plasma from all angles, so it has nowhere to go but around the ring. As the plasma particles whoosh around the ring, they collide, and fuse, and release energy in the form of heat.

Part of the challenge of making a useful fusion reactor is finding a way to extract that heat and use it to make electricity. At the same time, we need to keep the reactor components cool enough to not melt! So far, I’ve been doing a lot of work on this issue, working on the design of pipes that move water through the reactor to extract the heat.

In truth, my work can get very specific. I’ve spent the last 6 months investigating the sensitivity of the pipes in a single design to vibrations might be caused by the water flow. (If the water flow is too fast, it will break the pipes, if it’s too slow, the reactor will get too hot). A lot of science can get very detailed and specific like this, and sometimes it is hard to remember the big picture, so thank you for reminding me!