For most of us, a freezer doesn’t do anything more than give us a convenient source of ready meals or allow us to store the produce from our gardens or allotments to tide us over the winter.
But in industrial applications, freezers do much more than that. Processes such as blast-freezing, for example, allow large quantities of food to be frozen quickly, ensuring that it reaches the shops or restaurants in peak condition.
Freezing on a large scale, however, doesn’t come much bigger that that taking place at the International Thermonuclear Experimental Reactor (ITER) being built in the south of France. ITER is a fusion reactor, and if it’s successful the technology could solve most of the world’s energy problems, and without producing harmful radioactive waste.
Hotter Than the Sun
Bottle coolers and conventional freezers from suppliers such as Fridge Freezer Direct may well keep things cold, but we’re talking about serious cooling performance here. Nuclear fusion uses the same process that powers the sun. But while the sun burns at a mere 15 million degrees Celsius, the hydrogen plasma within ITER will be at around 10 times that temperature.
Such high temperatures would mean the sides of the reactor itself melting if the heated gas touched them, so the plasma is held in a vacuum using a magnetic field. Even so, the electromagnets used to generate the field need to be kept cool, and that’s where the need for a big freezer comes in.
Parts of the system need to be cooled down to minus 269 Celsius – only fours degrees above absolute zero, the lowest temperature possible.
So How’s It Done?
In order to cool the reactor core effectively, ITER uses a ‘cryostat’ – a massive stainless-steel structure surrounding the core. This is turn is linked to three interconnected cooling systems. The first uses water passed through a heat exchanger, and this will remove most of the heat. Next comes a liquid nitrogen system, which is then followed by a liquid helium system to provide cooling down to the very low levels required.
Although other locations such as the Hadron Collider at CERN have similar cooling needs, the difference with ITER is that it uses a single plant, making it the biggest freezer in the world.
As well as providing cooling for the magnets, the cryoplant system also helps to maintain the vacuum around the reactor’s plasma core. Any gases and vapours inside the reactor will be attracted to the cold pumps and condense on the surface.
Of course, all of this is very advanced technology involving massive technical challenges. For that reason, we won’t see the world’s biggest freezer in action for a while yet. The first test reactions at ITER aren’t expected to happen before 2023. It’s also an example of international collaboration, with the project being jointly funded by China, India, Japan, Russia, South Korea, the United States and the European Union. With a total cost of around 15 billion euros for the whole project, it’s a bit more expensive than your home freezer too