Radiation and Nuclear Physics Glossary

These flashcards cover key concepts related to radiation and nuclear physics, defined clearly for study and revision.

activity

The number of nuclei that decay per unit time in a sample, equal to λN.

acute dose

A radiation dose received over a short period of time.

ALARA

An acronym for As Low As Reasonably Achievable; the principle that radiation doses should be minimized.

alpha (α) particle

A particle composed of two neutrons and two protons, emitted from the nucleus of an atom.

annihilation

When a charged particle and its antiparticle come together, destroy each other, and release energy.

annual limit on intake (ALI)

The derived limit for radioactive material intake by an adult worker in a year.

atomic mass unit (amu)

A unit defined by the mass of carbon-12, equal to one-twelfth of the mass of a neutral atom of C-12.

atomic number (Z)

The number of protons in the nucleus of an atom.

attenuation

The process by which a radiation beam's intensity is reduced in material.

background radiation

Ionizing radiation from sources other than the one under consideration.

backscattering

The reflection of particles toward their original location.

becquerel (Bq)

A unit of measure for radioactivity, equal to one disintegration per second.

beta (β) particle

A high-speed particle, identical to an electron or positron, emitted from the nucleus.

binding energy

Energy that holds a nucleus together.

biological half-life

The time required for the body to eliminate half of a substance by biological processes.

bremsstrahlung

X-rays produced by the acceleration or deceleration of charged particles.

cell effect

The decrease in reactivity with increased temperature due to energy transfer.

Cherenkov radiation

The blue halo produced by electrons traveling faster than light in water.

chronic dose

A radiation dose received over an extended period.

committed dose equivalent (CDE)

The dose equivalent received by organs from radioactive material intake over fifty years.

committed effective dose equivalent (CEDE)

The sum of products of weighting factors and CDE for irradiated organs.

control rods

Materials used to control chain reactions in a reactor by absorbing neutrons.

Compton scattering

A photon strikes an atom and transfers energy to an electron.

decay constant

The probability that a nucleus will decay in a given time interval.

decay series

A sequence of decay events where unstable atoms produce other unstable atoms.

deep-dose equivalent (DDE)

The dose equivalent at a tissue depth of 1 cm from external radiation.

deterministic effect

Effects directly related to dose received, becoming more severe with higher doses.

delayed neutron

A neutron that comes from the decay of a fission fragment.

Dose equivalent

The product of absorbed dose in tissue and a quality factor.

electron

An elementary particle with a negative charge and minimal mass.

electron capture

A mode of radioactive decay where an orbital electron is captured by the nucleus.

exposure

A measure of a photon’s ability to produce ionizations in air.

fission

The breaking apart of atomic nuclei.

fissionable

A nuclide that can undergo fission by absorbing a neutron.

gamma (γ) radiation

Electromagnetic waves emitted from the nucleus of an atom.

genetic effects

Effects observed in the offspring of individuals who received an agent.

gray (Gy)

A unit measuring absorbed dose, equal to one joule absorbed per kilogram.

half-life

The time taken for half of a sample of nuclide to decay.

health physics

An interdisciplinary science focused on radiation protection for humans and the environment.

ionization

The process of removing an electron from an atom, creating an ion.

isotope

Nuclides with the same number of protons but different numbers of neutrons.

linear energy transfer (LET)

Average energy lost per unit distance by particles as they pass through material.

neutron activation analysis

An analytical tool to determine the kinds of atoms present in a sample.

non-ionizing radiation

Radiation without enough energy to remove tightly bound electrons from atoms.

nucleus

The center of an atom, composed of protons and neutrons.

pair annihilation

When a particle and its antiparticle collide and produce a photon.

photoelectric effect

A process where a photon transfers all its energy to an orbital electron.

radiation

Energy in transit in the form of high-speed particles and electromagnetic waves.

radius (of a particle)

The average distance a particle penetrates into material.

rem (roentgen equivalent mammal)

A unit for equivalent dose in human tissue, relating absorbed dose to biological damage.

stochastic effects

Effects based on probabilities with no threshold, increasing with dose.

threshold dose

The minimum dose needed to observe a specific deterministic radiation effect.

X-rays

Photons emitted due to energy changes in electrons within atoms.