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Nuclear & Radiochemistry

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Nuclear & Radiochemistry

Alpha Decay

Radioactive decay in which a nucleus emits a helium-4 nucleus, losing two protons and two neutrons.

ᴬ_Z X → ᴬ⁻⁴_Z₋₂ Y + ⁴₂He MeV
Nuclear & Radiochemistry

Artificial Radioactivity

Radioactivity in nuclides created by bombarding stable nuclei with particles rather than found in nature.

Bq
Nuclear & Radiochemistry

Background Radiation

The ionising radiation always present in the environment from natural and artificial sources.

mSv/year
Nuclear & Radiochemistry

Band of Stability

The region on a plot of neutron number against proton number within which stable nuclides are found.

Dimensionless
Nuclear & Radiochemistry

Becquerel

The SI unit of radioactivity, equal to one nuclear disintegration per second.

1 Bq = 1 s⁻¹ Bq
Nuclear & Radiochemistry

Beta-Minus Decay

Radioactive decay in which a neutron converts into a proton, emitting an electron and an antineutrino.

n → p + e⁻ + ν̄ MeV
Nuclear & Radiochemistry

Binding Energy per Nucleon

The nuclear binding energy divided by the number of nucleons, measuring the stability of a nucleus.

BE/A MeV/nucleon
Nuclear & Radiochemistry

Breeder Reactor

A reactor that produces more fissile material than it consumes by converting fertile nuclides.

²³⁸U + n → ²³⁹Pu Dimensionless
Nuclear & Radiochemistry

Cloud Chamber

A device that reveals the paths of ionising particles as visible trails of condensed vapour.

Dimensionless
Nuclear & Radiochemistry

Control Rod

A movable rod of neutron-absorbing material used to regulate the rate of a nuclear chain reaction.

Dimensionless
Nuclear & Radiochemistry

Critical Mass

The minimum mass of fissile material needed to sustain a nuclear chain reaction.

kg
Nuclear & Radiochemistry

Curie

The older unit of radioactivity, defined as the activity of one gram of radium-226.

1 Ci = 3.7 × 10¹⁰ Bq Ci
Nuclear & Radiochemistry

Decay Constant

The probability per unit time that a given nucleus will decay.

λ = 0.693 / t½ s⁻¹
Nuclear & Radiochemistry

Electron Capture

Radioactive decay in which a nucleus absorbs an inner-shell electron, converting a proton into a neutron.

p + e⁻ → n + ν MeV
Nuclear & Radiochemistry

Gamma Emission

The release of high-energy electromagnetic radiation from a nucleus dropping to a lower energy state.

ᴬ_Z X* → ᴬ_Z X + γ MeV
Nuclear & Radiochemistry

Geiger–Müller Counter

An instrument that detects ionising radiation through the avalanche of ionisation it triggers in a low-pressure gas.

counts/s
Nuclear & Radiochemistry

Gray

The SI unit of absorbed radiation dose, equal to one joule of energy deposited per kilogram of matter.

1 Gy = 1 J/kg Gy
Nuclear & Radiochemistry

Ionising Radiation

Radiation with enough energy to remove electrons from atoms, creating ions.

eV
Nuclear & Radiochemistry

Isotope Dilution Analysis

A quantitative technique in which a known amount of labelled isotope is added and the resulting dilution measured.

n_unknown = n_spike(R_spike/R_mix − 1) mol
Nuclear & Radiochemistry

Law of Radioactive Decay

The principle that the rate of decay is proportional to the number of undecayed nuclei present.

N = N₀ e^(−λt) Dimensionless
Nuclear & Radiochemistry

Magic Numbers

Particular numbers of protons or neutrons that give a nucleus exceptional stability.

2, 8, 20, 28, 50, 82, 126 Dimensionless
Nuclear & Radiochemistry

Mass Defect

The difference between the mass of a nucleus and the sum of the masses of its constituent nucleons.

Δm = Zm_p + Nm_n − m_nucleus u
Nuclear & Radiochemistry

Moderator

A material used in a reactor to slow fast neutrons to energies at which fission is far more probable.

Dimensionless
Nuclear & Radiochemistry

Neutron Emission

The direct ejection of a neutron from an extremely neutron-rich nucleus.

ᴬ_Z X → ᴬ⁻¹_Z X + ¹₀n MeV