The climate is changing, and as a result, many people are hard at work looking for alternative sources of power to lower the emissions of greenhouse gases like CO2. Nuclear energy is one such alternative energy source that has been part of the United Stages energy mix for decades.
That said, there remain many questions about nuclear energy, including which option — nuclear fusion vs. nuclear fission — is the most viable in the foreseeable future.
Let’s learn more about nuclear fission vs. fusion, how these two power sources are alike, how they’re different, and how they can be used to fuel our clean-energy future.
First, the Basics: What Is An Atom?
Understanding the nuclear reactions involved in both fusion and fission is easier if you have a refresher on the structure of atoms. An atom is the basic unit of matter —anything with mass and takes up space is made up of atoms.
Most of the physics relevant to nuclear energy deal with changes to atomic nuclei. A nucleus is made up of positively-charged protons and neutrally-charged neutrons (meaning they have no charge). The nucleus is orbited by a cloud of electrons, which are negatively charged.
For any given atom, the number of protons determines what element it is. Hydrogen atoms always have one proton while helium atoms always have two, and so on.
The number of neutrons can vary from one atom to the next, however, and these are known as isotopes. For instance, deuterium and tritium are two isotopes of hydrogen. They each contain one proton but different numbers of neutrons — deuterium has one neutron and tritium has two.
With this context established, we can turn to a discussion of nuclear fusion.
What Is Nuclear Fusion Energy?
Nuclear fusion is a technical term for fusion reactions in which two light nuclei combine together into one heavier nucleus. Because smaller, lighter nuclei are fusing into a single nucleus, the process is called fusion. These nuclear reactions release energy, which can be harvested to provide power wherever it is needed.
Although nuclear fusion can occur among many different elements, today many researchers are looking at the so-called deuterium-tritium [DT] fusion reaction, a reaction that occurs between two isotopes of hydrogen.
The DT reaction creates a neutron, a helium atom, and a large amount of energy. It produces more energy than most other kinds of fusion reactions (and at lower temperatures than other elements), which is why it’s of so much interest to researchers.
What Is Nuclear Fission Energy?
Nuclear fission is a technical term for fission reactions in which one heavier nucleus is broken down into multiple lighter nuclei. Unlike nuclear fusion, which fuses nuclei, nuclear fission splits them apart. This is achieved by firing a neutron at an atom of an element like uranium-235. The neutron must be traveling quickly enough to overcome the atom’s binding energy, causing the protons and neutrons in the atom’s nucleus to come apart.
The fission products that result from this process then cause a chain reaction, in which the original atom is broken apart with a neutron, which releases more high-energy neutrons that disintegrate more atoms, and so on.
Fission reactions produce an enormous amount of energy that can in turn be used to generate electricity that powers homes and businesses.
How Do Fission and Fusion Both Produce Energy?
Both fusion and fission are nuclear processes that produce an enormous amount of energy through different physical mechanisms. It’s worth understanding how these mechanisms are different, as it plays a key role in their respective advantages and disadvantages.
Nuclear Fission
In today’s world, nuclear technology relies entirely on nuclear fission, so we’ll start by describing how nuclear fission produces energy.
The process takes place in a nuclear reactor inside a nuclear power plant. The high temperatures that result from a fission reaction in the reactor core are used to heat water in the power plant, which creates steam. This steam is then used to spin a turbine, the blades of which are attached to generators that produce electricity.
In some nuclear power plants, the steam is then sent to a different structure called the “cooling tower,” where it’s cooled and condensed back into liquid water. Since the water is continuously reused in this setup, the amount of water used is kept relatively low.
Other nuclear power plants that don’t have a cooling tower will instead utilize water from nearby sources, such as rivers, lakes, or the ocean.
Nuclear Fusion
Nuclear fusion power is a more speculative technology that is currently being actively developed by physicists and other scientists. Fusion power relies on nuclear fusion reactions, in which smaller nuclei are manipulated under extremely high temperatures to fuse into larger atoms. This occurs in fusion reactors, and it releases an enormous amount of energy that can be harnessed and put to work.
However, reaching those incredibly high temperatures for extended periods of time has proven to be difficult. There has been some progress though: In 2022, physicists in China broke a nuclear fusion record with an “artificial sun” that reached 70 million degrees Celisius (126 million degrees Fahrenheit), which is about five times hotter than the sun’s core. It lasted for a total of 17 minutes.
How Much Energy Comes From Nuclear Fission and Nuclear Fusion?
As of 2022, there were 28 U.S. states using nuclear power in 54 different nuclear power plants. Because three of these plants have three reactors and 32 have two reactors, there were a total of 92 nuclear reactors in operation. Since 1990, these power plants have been generating around 20% of the electricity used in the U.S.
Globally, there are 33 countries using nuclear power, and in about half of those countries, nuclear power accounts for at least one-fifth (20%) of the total energy mix.
The story is different with nuclear fusion. Fusion was discovered almost a century ago, back in the 1930s. Though research has been ongoing, today there are just 20 fusion reactors globally, all working to develop the technology needed to create and control the high temperatures that fusion relies on.
The biggest such prototype is being created in southern France by the International Thermonuclear Experimental Reactor (ITER). This consortium, established with funding from 35 countries after a 1958 Atoms for Peace conference, is working to build a “tokamak” fusion reactor. This reactor gets its name from the machines it uses to create a magnetic field powerful enough to maintain control over charged particles during fusion.
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Though fusion reaction has yet to prove commercially viable, over the past couple of years a number of startling breakthroughs have been achieved, leaving many to wonder if we might not be on the cusp of an atomic energy renaissance.
For example, in late 2022, a team of scientists at California’s Lawrence Livermore National Laboratory (LLNL) used a technique called inertial confinement fusion to successfully get more energy out of a fusion reaction than is put in.
Long considered a holy grail in fusion science, this watershed moment prompted the U.S. Department of Energy to commit to investing over $600 million in further research. If it becomes possible to build a commercial fusion reactor, it could revolutionize the world’s production of energy.
What Do Nuclear Fission and Fusion Have in Common?
When it comes to fission vs. fusion, both rely on principles of nuclear physics to generate energy. Nuclear fission relies on the energy released when a larger atom is broken down into smaller atoms, and nuclear fusion relies on the energy released when smaller atoms are built up into larger ones.
There are, however, important differences. While nuclear fission has been operating commercially for decades, nuclear fusion is still in the planning and development phase, and it remains unclear when it will be ready for widespread use.
Does Fission or Fusion Produce Nuclear Waste?
Nuclear fission creates power by bombarding uranium with neutrons until it splits, releasing energy.
Fission creates two major kinds of fission products. The first kind consists of lighter elements, such as cesium-137 and strontium-90, which result when a heavy uranium atom breaks down into smaller elements. These are highly radioactive and will gradually “decay” — i.e. lose their dangerous radioactivity — over a period of a few decades.
The second kind consists of heavier “transuranic” elements, such as plutonium. These result when the neutrons given off by fission are captured by other uranium atoms, producing a bigger element. These are much less radioactive than the lighter fission products, but they also take thousands of years to decay.
Both types of waste must be stored in a way that protects people from exposure to radiation. Even short exposures to highly-radioactive waste can be fatal, or can lead to health problems such as cancer later on.
Fusion, on the other hand, is different. One of its great advantages is that it does not produce the type of nuclear waste that fission creates. The byproducts of nuclear fusion only need to be stored for a century or less, and in some cases, can even be recycled for use in new nuclear power plants.
Is Fusion Energy More Powerful Than Fission?
When it comes to fission vs. fusion, which is more powerful? Though today’s nuclear fusion designs are not yet commercially viable, nuclear fusion could produce as much as quadruple the amount of power generated by nuclear fission, meaning that nuclear fusion is substantially more powerful than fission.
Is a Nuclear Bomb Fission or Fusion?
Since the development of atomic energy, there have been concerns about its weaponization. These concerns were born out when the United States infamously dropped atomic bombs on Hiroshima and Nagasaki in the closing years of World War II. Those bombs were based on nuclear fission.
But it’s vital to remember that there’s an enormous difference between nuclear power and nuclear weapons. A nuclear reactor cannot explode like a nuclear bomb, which has to be built in a special way with certain materials to be effectively weaponized.
Fission vs. Fusion: Diving Deeper Into Nuclear Energy
In the ongoing effort to mitigate our dependence on fossil fuels, reduce emissions, and develop renewable energies, nuclear power continues to be a high-interest option that could potentially supply cheap, clean, abundant energy to many. That said, there are also ongoing concerns about nuclear waste and aging power plants.
In the meantime, you can learn more about renewable energy sources for the future and how it might carry us into the years ahead.
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