Activity. Number of disintegrations of the nucleus of a radioactive atom per unit of time. Measured in Becquérel.
Alpha (Radiations). Low energy corpuscular radiation with high ionisation capacity.
Atom. The smallest part of an element that keeps the typical features of the element itself
Atomic number. The atomic number of an element is given by the number of electrons of its atom and is indicated with the letter Z.
Average-life. Average life duration of a radionuclide. It is the opposite of the decay constant.


Becquérel. From the name of the French Physicist who discovered uranium radiations. Unit of measurement of the activity. Corresponds to one disintegration per second.
Beta (Radiations). Corpuscular radiations, constituted of high speed electrons.


Calibration factor (Dimensionless).  Multiplication factor to apply to the value read by the instrument.
Calibration factor F. Multiplication factor to apply to the value read by the instrument to obtain the reference value.
Contamination meter. Instrument for evaluation of surface contamination Used in nuclear medicine, radiochemical laboratories and any place where alpha, beta or gamma emitter isotopes are handled.


Decay constant. It is the probability that a radioactive atom decays within the unit of time. It is usually indicated with the Greek letter
Decay time. Time necessary for a radionuclide, decaying according to an exponential law, to reduce its activity of the initial value by half.
Delayed effects. These effects show after years or even tens of years from the irradiation. They have a probablistic character and do not require a particular dose threshold to the exceeded. They are called probabilistic (or stochastic) as it is not certainly possible to blame them on irradiation, but it is possible to establish a statistical correlation between their appearance and exposure to radiation. Among the delayed effects, genetic effects are notably high, referring to offspring.
Dose absorbed. Energy absorbed by a body exposed to a beam of radiation.
Dose calibrator. Instrument for controlling the dose of radio medicines intended to be introduced into the human body.
Dosimetry. Measurement and evaluation of the exposure to ionising radiation in living and work environments and the dose absorbed by one or more individuals


Electrometer. Electric instrument used to measure the radiation values based on the measurement of the potential difference.
Electron Negatively charged particle found in the external part of the atom. Its mass is very small with respect to the total weight of the atom, enclosed in maximum part of the nucleus.
Exposure dose. Capacity of the electro-magnetic radiation to produce ionisation in air.


Gamma (rays). High energy electro-magnetic radiation.
Geiger-Muller. Radiation counter similar to the ionisation chamber, in which however the passage of ionising radiation causes a discharge between two electrodes, between which a high electric potential difference is realised. A high sensitivity results, but also the impossibility to discriminate the energy of the incident radiation.


Hands, feet and clothing. Instrument for measuring alpha, beta or gamma radiation in the body or clothing.


Immediate effects. Somatic effects of the radiation, they depend on the quantity of dose absorbed and occur when this exceeds a certain threshold value. Within a short period the individuals irradiated start to show the symptoms of irradiation, which get worse as the dose increases. The immediate effects can be clearly recognised on the person exposed and it is always possible to establish a connection between dose and effect.
Ionisation chamber. Ionising radiations detector. Measures the ionisation produced in a gas by measuring the charges produced on the passage of the radiation.
Ionisation. Loss or acquisition phenomenon of an electric charge by an atom or a molecule. Can be caused by the passage of high energy radiation through the material.
Ionising radiation. Radiation able to cause the ionisation phenomenon of the material means passed through.
Ions. Atom or molecule that has lost or acquired one or more electrons, thus modifying their total electric charge.
Irradiation. Exposure to ionising radiation. It can be natural (produced by cosmic rays, the ground or radioisotopes present naturally in the human body) or artificial (caused by radiation coming from non-natural sources, such as X ray tubes, nuclear reactors, radioactive fall-out, sources used professionally in various sectors).
Isotopes. Atoms with the same atomic number, but different mass number, i.e. different number of neutrons in the nucleus.


Mass number. Indicates the total number of protons and neutrons in the nucleus of the atom. It is indicated with the letter A.
Multimeter. Instrument used to detect large quantity measurements, as for example Doses, time and kilovolts.


Neutron. Particle without charge. Along with the proton it contributes to the nuclear structure of the atom.
Nuclide. Atom characterised by a mass number A and charge number Z


Passive dosimeter. Device used to measure the radiation from ionising radiation. (the values can be supplied for the following measurements: Exposure, Kerma in air, Ambient Dose Equivalent and Personal Dose Equivalent). Usually used to monitor the persons whose work activity envisions the risk of absorbing doses of ionised radiation.
Photon. Basic unit (“quantum”) of electromagnetic radiation.
Proton. Particle with positive charge that stays, along with the neutron, in the nucleus inside the atom.


Qualified expert. Specialist that has specific know-how regarding radiation, able to perform adequate surveillance and protection actions


Radiation. Energy that propagates in space without significant transport of material also without the support of a material means.
Radioactive contamination. Pollution of an object, of an environment or living organism with radioactive substances.
Radioactive decay. Decrease of the activity of a radioactive material through time due to disintegration of the atoms of the substance.
Radioactivity. Condition of the nucleus of an atom with unbalanced number of neutrons and protons. The nucleus tends to re-balance the proportion between its nucleons by disintegrating some of them and emitting particles and/or radiation.
Radioisotope. Radioactive isotope of a certain chemical element. Because the radioactivity involves only the atomic nucleus and not the electronic cloud, the chemical features of a radioisotope are identical to those of the corresponding stable element.
Radioprotection. Group of materials and procedural Standards to be used to guarantee the protection of persons from the noxious effects of ionising radiation.
Radiotoxicity. Toxicity due to the ionising radiation emitted by a radioactive nuclide, in relation to the features of the metabolism of the element or organism and its chemical-physical state.


Shielding. Attenuation of the ionising radiation energy at levels compatible with a suitable reduction of the risk levels.


Whole-body radiation meter. Instrument for measuring ionising radiation. They detect the presence of radiation and quantify the value.


X (Rays). Electromagnetic radiation. They are produced in nature during the decay of some atomic nuclei or due to deceleration radiation and artificially in X ray tubes.