Fission Energy

Nuclear Energy: Fission and Fusion

Nuclear energy is produced through either nuclear fission or nuclear fusion.

In nuclear fission, an atom's nucleus is split into smaller nuclei. This process releases energy that can be harnessed to produce electricity, as well as heat.

Nuclear fusion, on the other hand, involves joining two nuclei from two atoms, to form a larger nucleus into one atom. This process also releases energy, but it has not yet been successfully harnessed for commercial use.

Both nuclear fission and nuclear fusion are environmentally friendly sources of energy, as they produce little to no greenhouse gas emissions. However, nuclear power plants (fission) do generate radioactive waste, which must be carefully managed to prevent environmental contamination. Moreover, the commissioning and decommissioning of nuclear facilities take a long time (up to 30 years!). Additionally, nuclear ores are exhaustible resources.

Fission Neutron Energy Spectrum

Fission nuclear energy comes from a free neutron (a subatomic particle) colliding with an atom (a collection of subatomic particles). In nuclear fission, a nucleus splits into two smaller nuclei and releases energy in the form of photons and neutrons.

These neutrons need to have energy above a certain value (measured in mega electron volts, or MeV) in order to produce reactions. The resulting neutrons produce two main types of energy:

• kinetic (movement) - fast neutrons

• thermal (heat) - slow neutrons

More specifically, in order to induce fission, the neutron must have enough energy to overcome the electrostatic repulsion between the protons in the nucleus. This can be accomplished by either:

• bombarding the nucleus with high-energy neutrons (thermal fission)

• using lower-energy neutrons that are moderators to slow down the neutrons before they strike the nucleus (fast fission).

Once fission has been induced, the resulting nucleus will be highly unstable and will often decay rapidly, releasing additional neutrons that can induce fission in other nuclei, resulting in a self-sustaining chain reaction.

We could also look at dividing fission into the photons energy region and the particles energy region. The photons energy region comprises energy such as gamma radiation. The particles energy region is determined by the maximum kinetic energy of the heaviest charged particle emitted in the reaction, such as an alpha particle.²

The energy spectrum of these fission neutrons is important for understanding the fission process and for applications, such as reactor design and nuclear waste transmutation.

The fission neutron energy spectrum can also be divided into three regions:

• prompt

• thermal

• epithermal

Prompt fission neutrons are released with energies of up to about 2 MeV; they are produced by the decay of excited nuclei created in the fission process.³

Thermal fission neutrons are emitted with energies of up to about 0.5 eV; they result from the thermal motion of nuclei in the fissioning system.

Epithermal fission neutrons have energies of up to about 10 keV; they are produced by neutron scattering in the fissioning system. Each region of the fission neutron energy spectrum has different characteristics that affect the fission process and its applications.

The energy released by fission can be harnessed for both peaceful and military purposes. In nuclear power plants, fission is used to generate electricity, while in nuclear weapons, it is used to create an explosive force.

Extracting these resources

Both thorium and uranium need to be extracted from beneath the surface. Uranium and thorium extraction are the processes of mining and concentration.

Polymer adsorption is when water or air is passed through a bed of polymer beads, and the uranium or thorium contained are adsorbed onto the surface of the beads. Uranium and thorium can also be mined from phosphate deposits, or extracted from coal ash (a by-product of coal combustion).

Fission Energy Pros and Cons

Nuclear fission, when compared to fossil fuels such as coal, is a cleaner source of energy. It produces no greenhouse gases or air pollution during its operation.

Pros

Nuclear fission is an efficient way to produce electricity. One nuclear reactor can generate the same amount of electricity as several coal-fired power plants. Another strong point is that it is a reliable source of energy. Renewable energies such as wind and solar tend to be intermittent, whereas a nuclear power station is entirely controllable and predictable in terms of energy tempering and output.

Another interesting aspect is that nuclear fission is a scalable source of energy, meaning that it can be built to meet increasing demands for electricity. While presently not 100% of the uranium, thorium, etc. harvested can be extracted, the extraction capabilities of energy from the radioactive ores are becoming better.

However, there are also disadvantages to nuclear fission.

Cons

First and foremost, nuclear energy comes from radioactive ores, which are not renewable. What exists in our Earth's crust was created during the primordial exhalation of the Universe! We are able to manufacture or exploit various forms of radioisotopes (most elements can be made radioactive through induced radioactivity), but we still need raw uranium or thorium material.

The first major disadvantage to society is the risk of nuclear accidents.

While accidents are rare, meltdowns and the escaping of radioactive isotopes means they can be carried away by the elements, such as wind and water, over great distances.

The fear or real risks of nuclear accidents can have detrimental impacts on citizens, especially where the measures to contain radioactive material in the case of an accident are not easy to take.

Energy grid limitations are critical in delivering high energy density sources to the general population. If the energy grid is old and cannot support a heavy electricity load, high energy production becomes futile because it cannot be transported to a source that desires to use it.

Another disadvantage is that nuclear waste can be difficult and expensive to store safely.

Finally, nuclear proliferation is a concern because the technology needed to build a nuclear weapon can also be used to build a nuclear power plant.

Despite these disadvantages, nuclear fission is an efficient source of energy that has many potential applications. It significantly reduces the overreliance on the more pollutive fossil fuels such as coal.

Uses of Nuclear Fission Energy

Nuclear fission reactions are carefully controlled in nuclear power plants so that they do not become nuclear explosions. In a typical nuclear power plant, nuclear fuel rods are inserted into a reactor, which is then filled with water. When the reactor is turned on, the nuclear reactions take place and generate heat, which is used to create steam.⁵ The steam turns turbines, which generate electricity. Nuclear power plants can provide a large amount of electricity for the grid, but they also come with some risks. If the nuclear reactions are not carefully controlled, they can lead to nuclear accidents, like the one that occurred at Chernobyl in 1986.

Nuclear energy can be used to generate electricity and propel spacecraft, or to power nuclear weapons and powerful explosions. In addition, nuclear fission can be used for medical purposes, such as cancer treatment.

If not properly controlled, nuclear fission can result in a nuclear accident, which can release harmful radiation into the environment.

Amount of Energy in Fission

The exact amount of energy released by fission depends on the particular nuclei involved. The reaction's products can be diverse. The formulas below show that Ba (Barium), Kr (Krypton), Zr (Zirconium), Te (Tellurium), and others, can result from Uranium 235. "n" refers to neutrons.

Plutonium-239 and thorium-232 are also used in fission processes, but thorium is naturally found in larger quantities. Some of these elements are created by humans, whereas some are naturally found within the Earth. Usually, the natural sources are uranium, thorium, and their decay elements like radon, whereas plutonium or caesium are man-made, created in nuclear reactors or as by-products in nature from explosions.

Countries around the world like France choose to operate on nuclear power plants. Undoubtedly, nuclear fission plays an important role in providing electricity for the population and economic activities. It is currently one of the few energy-dense alternatives we have to fossil fuels, which can help us achieve climate change prevention targets!