Radiation From the Nucleus and Nuclear Energy

Nuclear radiation is emitted from the nucleus of unstable atoms (radioisotopes) that are striving to become more stable.
In all nuclear transformations, atomic and mass numbers are conserved.
The half-life of an isotope refers to the time it takes for half of a group of unstable nuclei to decay. It is different for every isotope. The shorter the half-life of an isotope, the greater the activity — that is, the greater the number of decays per second. Activity decreases over time as less and less of the isotope remains. Activity is measured in becquerels (Bq).
Isotopes may pass through a sequence of decays in order to become stable. Such a sequence is called a decay chain, or decay series.
The force that holds nucleons together in the nucleus of an atom is called the strong nuclear force. It acts over a very short distance and is strong enough to overcome the electrostatic force of repulsion that exists between the protons of a nucleus when nucleons are very close together.

There are four types of nuclear decay: 𝛼, β −, β + and 𝛾 radiation.
𝛼 particles are released during 𝛼 decay. 𝛼 particles are relatively slow-moving particles that are equivalent to a helium nucleus and can be represented as 42He24He. After 𝛼 decay, the mass number of the daughter nucleus is four less than that of the parent nucleus, and the atomic number is two less.
β −particles are released in β − decay. β − particles are high-speed electrons released from the nucleus when a neutron transforms into a proton, an electron and an electron antineutron. After β − decay, the mass number of the daughter nucleus is the same as that of the parent nucleus, but the atomic number is one more than that of the parent nucleus.

10n→ 11p+0−1e+ν¯+energy01�→ 11�+−10�+�¯+energy

β + particles are released in β +decay. β + particles are high-speed positrons emitted with a neutrino from the nucleus when a proton transforms into a neutron. The atomic number of the daughter nucleus is one less than the parent nucleus; the mass number remains the same.

11p→ 10n+0+1e+ν+energy11�→ 01�++10�+�+energy

𝛾 radiation is electromagnetic radiation that is emitted when an excited nucleus becomes more stable. 𝛾 rays are emitted during 𝛼 and 𝛽 decay.

The effect of radiation exposure can range from nausea to death. The amount of radiation energy received by each kilogram of living tissue is measured in gray (Gy), but this value does not take into account the type of radiation that has been absorbed. Each type of radiation has a different effect because of its ionising power.
Equivalent dose measures the radiation energy absorbed by each kilogram of biological tissue and its effect by taking into account the form of radiation energy absorbed. Equivalent dose is measured in sievert (Sv).
Different tissues and organs have different radio sensitivities. This is reflected in the effective dose, which is the sum of the tissue-equivalent doses weighted by the weighting factors.
The Australian average annual radiation dose is approximately 1.5–2 mSv, most of which is from background radiation.

Mass and energy are equivalent and related by Einstein’s mass–energy equivalence equation E = mc2.

The nuclei of different atoms have varying degrees of stability. The binding energy of a nucleus is the energy required to completely separate a nucleus into individual nucleons. Therefore, the binding energy is a measure of the stability of a nucleus. Iron-56 is commonly thought to be the most stable of all nuclei.
In order for a nucleus to become more stable, it emits energy called nuclear energy. The amount of energy released corresponds to the difference between the mass of the particles before and after the release of energy, according to E = mc2.
Fusion reactions generally occur between small nuclei that form nuclei that are smaller than iron. Fusion occurs in the Sun, where hydrogen nuclei are converted into helium nuclei, resulting in large amounts of energy being released.
Fission reactions occur when a large nucleus is split into smaller, more stable fission fragments that have a higher binding energy per nucleon.

Fission reactions occur when a nucleus is split into smaller, more stable fission fragments. If every neutron released in fission is free to initiate more fission reactions, an uncontrolled chain reaction occurs. Controlled chain reactions occur when some of the free neutrons are absorbed by non-fissionable substances.
Moderators are used to slow down fast-moving neutrons.
Control rods consist of neutron-absorbing material, such as boron or cadmium, and are used in nuclear reactors to regulate the rate of nuclear fission.
The amount of uranium-235 in natural uranium is not enough to sustain a chain reaction; the percentage of uranium-235 needs to be increased to 1–4 per cent for use in nuclear reactors.
Enrichment is the process of increasing the percentage of uranium-235 in a sample of uranium to enable it to sustain a chain reaction.
A critical mass is needed for a sustainable chain reaction.
The nuclear fusion reaction between deuterium and tritium is a possible energy source.