What Are Nuclear Reactors and Why Are There so Many in France?

You may have heard the term 'power plant station', or seen a few big and odd-shaped buildings/towers releasing high amounts of steam on a trip through the rural suburbs, but you may not be entirely aware of what those machines are actually for...

Well, those nuclear power plant stations have buildings/towers called nuclear reactors, which are the heart of one of the most reliable, carbon-free sources of energy used in the world today. To put it simply, nuclear reactors produce electricity from steam, which is then distributed across the country into places like our homes for us to use. Did you know France currently has 56 operable reactors today, around 430 worldwide.

The first power plant station operations were developed during the 1950s, and at present nuclear power provides around 10% of electricity globally. However, some countries such as France rely more heavily on nuclear power, which currently accounts for a whopping 70% of the country's annual electricity production!

The most common and commercial types of nuclear reactors used today are called 'Pressurised Water Reactors' (PWRs). These are fuelled by uranium atoms - derived from enriched uranium pellets stacked together in the reactor core - to generate nuclear chain reactions that produce heat to turn into electricity. This heat is absorbed by a coolant - generally made of pressurised water to prevent boiling which is also used as a moderator - located inside the primary circuit. This coolant travels through the reactor, while heating up an outer water circuit which boils into steam. This steam then blows into and turns a turbine connected to a power generator, which produces electricity ready for distribution.

According to the Nuclear Energy Institute (NEI), "One uranium fuel pellet creates as much energy as one ton of coal, 149 gallons of oil or 17,000 cubic feet of natural gas". This makes it an incredibly green and sustainable form of renewable energy that reduces irreparable damage to our environment by using a uranium source that has a 92% capacity factor, as well as the potential to be reused and recycled, even after five years of usage inside a reactor! France is one of the main countries alongside Japan that works to carry out safe and regulated storage, disposal, and recycling practices for nuclear waste especially through companies such as Orano. You can have a look at this video to watch exactly how they recycle nuclear waste in their facility in Normandy.

The nuclear chain reactions, which occur inside the reactor through a process called nuclear fission, are created when a particle (such as a neutron) is struck into and absorbed by another atom's nucleus (uranium) causing the atom to split into two parts, otherwise known as 'fission products'. The first sources of neutrons fired inside the reactor usually derive from spontaneous fission, radioactive decay or external neutron accelerators.

The splitting uranium atoms release massive amounts of energy and heat, alongside a few extra neutrons. As the fission products have a smaller mass than the uranium atom itself, the extra mass has to be released somehow - in this case, in the form of extra neutrons. These extra neutrons then strike into other uranium atoms inside the reactor, causing further fission to occur and sustain a consistent nuclear chain reaction of rapid heat production.

Additionally, control rods are placed into the reactor core to absorb extra neutrons and regulate reaction speed. When the first splits happen, the extra neutrons are released at extremely high speeds, creating a harsher and more unstable environment for fission to take place. Control rods increase the absorption rate the further into the reactor they are, reducing the number of neutrons available for further fission. This is important as the power-output of the reactor can be slowed and balanced for more stability and consistency, as well as the control rods being inserted rapidly into the reactor to reduce fission to its minimum level, effectively shutting the reactor down as a safety procedure if needed.

There are many other types of nuclear reactors, such as Boiling Water Reactors (BWRs) and Heavy Water Reactors (HWRs), but all 56 reactors operating in France today are various types of Pressurised Water Reactors (PWRs). However, France is currently experimenting with a completely different type, which is said to be the largest nuclear reactor currently in construction in the entire world! This reactor is is named ITER, and focuses on another process called nuclear fusion, which is a process still in experimentation and is not being used in any operable reactors to date. A statement updated on August 3, 2023 by the International Atomic Energy Agency revealed that, 'ITER will start conducting its first experiments in the second half of this decade and full-power experiments are planned to commence in 2036... an electricity-producing fusion power plant could be built and operating by 2050.'

Nuclear fusion is the process that happens inside stars, most significantly in the sun, which uses its own gravitational pull to fuse hydrogen atoms together to form helium atoms. This is known as hydrogen fusion or hydrogen burning. This process occurs inside the sun's core, which is infernally hot, meaning it can override the repelling positive charges of hydrogen atoms and squeeze them together, fusing them and creating a burst of energy. This is the process responsible for the enormous energy output that powers the sun as well as providing the solar system with immense light and heat, allowing life to exist here on earth. How amazing!

Unfortunately, we cannot produce a replica of this at such a colossal scale on earth, which is why nuclear fusion reactors are the next best invention for this in development today. They have been made and proven to work on a smaller scale, but the main problem in the industry is that, while nuclear fission generates more energy than it consumes, scientists still haven't found a way to make nuclear fusion renewable or profitable as a result of underfunding. However, this is changing, thanks to a new breakthrough from the Lawrence Livermore National Laboratory in California. As of December 5, 2022, their latest fusion ignition experiment succeeded in yielding '3.15 megajoules (MJ) of fusion energy from a laser input of 2.01 MJ'. This is an extremely significant development in nuclear fusion reactors, because even though this energy output was not nearly enough to compensate the 300 million MJ and expenses invested in order to power the experiment, it is still a huge step towards ensuring that nuclear fusion becomes a sustainable as well as a profitable source of renewable energy.

So it looks like France's decision to invest in nuclear reactors will pay off in the long term, especially as Europe comes to grips with an enormous energy crisis. The next time you pass a nuclear reactor on a trip through the French countryside, you'll have at least some sense of the complex processes going on inside - and in the world at large.