Nuclear & Radiochemistry — 60 Terms Defined

Neutron-to-Proton Ratio Nuclear & Radiochemistry Dimensionless The ratio of neutrons to protons in a nucleus, the principal determinant of its stability and decay mode. N / Z

Nuclear Binding Energy Nuclear & Radiochemistry MeV The energy that would be required to separate a nucleus completely into its individual protons and neutrons. E = Δm c²

Nuclear Chain Reaction Nuclear & Radiochemistry Dimensionless A self-sustaining sequence of fissions in which neutrons released by one event trigger further events. k = neutrons produced / neutrons lost

Nuclear Chemistry Nuclear & Radiochemistry Dimensionless The study of changes that occur in atomic nuclei and of the properties of radioactive substances.

Nuclear Cross Section Nuclear & Radiochemistry barn A measure of the probability that a particular nuclear reaction will occur between a nucleus and an incident particle. σ, measured in barns

Nuclear Fission Nuclear & Radiochemistry MeV The splitting of a heavy nucleus into two lighter nuclei with the release of neutrons and a large amount of energy. ²³⁵U + n → fragments + 2–3n + energy

Nuclear Fuel Enrichment Nuclear & Radiochemistry Dimensionless The process of increasing the proportion of a fissile isotope above its natural abundance.

Nuclear Fusion Nuclear & Radiochemistry MeV The combining of light nuclei into a heavier one, releasing energy. ²H + ³H → ⁴He + n + 17.6 MeV

Nuclear Isomer Nuclear & Radiochemistry MeV A nucleus in a long-lived excited state that decays to its ground state by gamma emission. denoted with m, e.g. ⁹⁹ᵐTc

Nuclear Reactor Nuclear & Radiochemistry MW A device in which a controlled nuclear chain reaction generates heat for power or produces radioisotopes.

Nuclear Stability Nuclear & Radiochemistry Dimensionless The tendency of a nucleus to persist without undergoing radioactive decay.

Nuclide Nuclear & Radiochemistry Dimensionless A distinct species of atom characterised by a specific number of protons and neutrons in its nucleus. ᴬ_Z X

Parent and Daughter Nuclide Nuclear & Radiochemistry Dimensionless The nuclide undergoing decay and the nuclide produced by that decay. parent → daughter + radiation

Penetrating Power Nuclear & Radiochemistry mm The depth to which a given type of radiation can travel into a material before being absorbed.

Positron Emission Nuclear & Radiochemistry MeV Radioactive decay in which a proton converts into a neutron, emitting a positron and a neutrino. p → n + e⁺ + ν

Radiation Dose Nuclear & Radiochemistry Gy A measure of the energy deposited in matter by ionising radiation. D = E / m

Radioactive Activity Nuclear & Radiochemistry Bq The number of nuclear disintegrations occurring in a sample per unit time. A = λN

Radioactive Decay Series Nuclear & Radiochemistry Dimensionless A sequence of successive radioactive decays leading from a long-lived parent to a stable end product.

Radioactive Half-Life Nuclear & Radiochemistry s The time required for half the nuclei in a radioactive sample to decay. t½ = 0.693 / λ

Radioactive Tracer Nuclear & Radiochemistry Bq A radioisotope introduced into a system so that its pathway can be followed by detecting its radiation.

Radioactive Waste Nuclear & Radiochemistry Bq/kg Material containing radionuclides for which no further use is foreseen and which requires controlled disposal.

Radioactivity Nuclear & Radiochemistry Bq The spontaneous emission of particles or electromagnetic radiation from unstable atomic nuclei.

Radiocarbon Dating Nuclear & Radiochemistry years A dating technique that determines the age of organic material from its residual carbon-14 content. t = (t½ / 0.693) ln(N₀/N)

Radioisotope Nuclear & Radiochemistry Dimensionless An isotope of an element whose nucleus is unstable and undergoes radioactive decay.