absorbed dose

A measure of the energy from ionising radiation deposited in a unit mass of any specified material. The unit of absorbed dose is the Gray.

absorption

Process where material in contact with the skin may pass through the pores on the skin's surface and enter the bloodstream. Identified as a possible route for contaminant entry into the body.

accuracy

Level of agreement between true value and observed value.

activation

Process where a neutron is captured by a nucleus to form a new isotope (often a radionuclide).

activation product

An isotope created by activation.

activity

See radioactivity.

activity concentration

Terminology used to describe radioactivity levels relative to the mass or volume of the sample matrix (eg Bqkg^-1 in soil, BqL^-1 in water).

ALARP

As Low As Reasonably Practicable - a standard for assessing necessary control measures taking into account the practicalities of the task in hand. Note: "reasonably practicable" has a defined legal meaning in the UK. ALARP incorporates this legal meaning as opposed to any other meaning that may be implied from technical publications such as those by the International Commission on Radiological Protection (ICRP).

alpha (a) decay

A form of radioactive decay resulting in the emission of a positively charged particle (a helium nucleus).

anthropogenic radionuclides

Artificially produced radionuclides, by means of activation or nuclear fission.

Approved Dosimetry Service (ADS)

A dosimetry service approved by HSE (or a body specified by HSE) for measuring, assessing and recording radiological doses to workers.  The aim of approval is to ensure, as far as is possible, that doses are assessed on the basis of accepted national standards.

atmospheric fallout

Widespread dispersion of radionuclides. Normally refers to the effects of nuclear weapons testing or events with global impact such as Chernobyl.

averaging volume

The volume of waste over which the activity concentration is measured and averaged to give an average activity concentration for waste sentencing purposes.

background radiation

Radiation from naturally occurring radionuclides, and from man-made sources (such as global fallout as it exists in the environment from the testing of nuclear explosive devices or from nuclear accidents like Chernobyl) that are not under the control of the cognisant organisation.

Becquerel (Bq)

The International System (SI) unit of activity equal to one nuclear transformation (disintegration) per second.

beta (b) decay

A form of radioactive decay resulting in the emission of an electron or positron.

classified worker

A category of worker defined under the Ionising Radiations Regulations 1999. Any person who, during the course of their work, is likely to receive an annual effective dose in excess of 6 mSv or three-tenths of the appropriate dose limit should be a classified worker.

conceptual model

A textual or schematic hypothesis of the sources and nature of contamination on a site, the pathways and migration mechanisms by which it may be transported, and the receptors that may be affected.

contaminant

An undesirable concentration or quantity of a substance, or activity concentration of a radionuclide, present in water, atmosphere or soil.

contamination

Presence of substances or agents as a result of human activity. Note that there is no assumption in this definition that harm results from the presence of the contamination.

controlled area

Any area where the annual effective dose to persons working there is likely to exceed 6 mSv or three-tenths of the appropriate dose limit.

controlled waste

Defined for the purposes of the Environmental Protection Act 1990 as comprising household, commercial and industrial waste. Excludes certain categories of waste, such as radioactive waste.

controlled waters

Defined in Part III (Section 104) of the Water Resources Act 1991, this embraces territorial and coastal waters, inland fresh waters, and groundwaters.

cosmogenic radionuclides

Radionuclides produced by the interaction of cosmic rays with terrestrial matter (eg in the atmosphere).

cross-contamination

A process whereby, during a series of intrusive investigations or within a single investigation, contaminated material from one area comes into contact with material from another area, thereby potentially affecting the results of any analyses being carried out.

daughter nuclide

see decay product.

decay chain

A series of radionuclides, each of which decays into the next radionuclide in the series until a stable nuclide is reached.

decay product

The nuclide produced following a radioactive decay. Also called a daughter nuclide.

discharge

Any emission of a contaminant into the environment.

dose constraint

A target maximum individual dose set by an employer or Radiation Protection Adviser for any project involving the use of ionising radiations. The target is set on the basis of what can be achieved by best practice and helps to keep doses ALARP.

effective dose

The damage sustained by a body by an equivalent dose. Takes into account the susceptibility of different organs to damage from ionising radiation.

equivalent dose

The sum of the corrected doses (see quality factor) for each type of radiation. Takes into account the different amounts of damage done by different radioactive decay types. The unit of equivalent dose is the Sievert.

exempt waste

Radioactive waste that is exempt from some or all of the requirements of the Radioactive Substances Act 1993. Such wastes are defined in Exemption Orders made under the Act. See also SoLA.

Exemption Orders

Subsidiary legislation, operating under the Radioactive Substances Act 1993, that "exempts" certain materials and forms up to prescribed activity concentrations from some or all of the requirements of the Act.

external radiation

Radiation from a source outside the body.

fission product

A nuclide produced as a result of nuclear fission.

gamma (g) radiation

Penetrating high-energy, short-wavelength electromagnetic radiation (similar to X-rays) emitted during radioactive decay. Gamma rays are very penetrating and require dense materials (such as lead or steel) for shielding.

gas-filled detector

Radiation detector consisting of a tube filled with ionisable gas. When the gas is ionised by radiation, the ions are detected by electrodes.

geophysics

The science of detecting geological structure and buried objects using a variety of (normally non-intrusive) investigative techniques.

geotechnical testing

Determination of the physical properties of soil/rock.

gray (Gy)

The unit of absorbed energy (Jkg^-1).

groundwater

All water that is below the surface of the ground in the saturation zone and is in direct contact with the ground or subsoil.

half-life

The time required for one-half of the atoms of a particular radionuclide present to disintegrate.

harm

Adverse effect on the health of living organisms, or other interference with ecological systems of which they form a part, and, in the case of humans, including property.

hazard

The potential for harm posed by a contaminant or circumstance, taking no account of the likelihood of exposure.

hectare

A unit of area, equivalent to 10 000 m².

heterogeneous

Material with areas of different composition within its volume.

hold point

Exposure limit specified for a particular project, which cannot be exceeded without re-assessment of working practices, including any PPE and RPE requirements.

homogeneous

Material of uniform composition throughout its volume.

hot spot

An area containing elevated contaminant concentration or activity concentration relative to the surrounding area.

HSE

The Health and Safety Executive.

ingestion

Contaminant entering the stomach and gastrointestinal tract through eating contaminated food or hand to mouth contact.

inhalation

Breathing contaminant (eg particulate material, vapour, gas) in through the mouth or nose.

injection

Contaminant entering the body tissue and blood stream directly through cuts and abrasions.

internal radiation dose

Dose received internally to the body via inhalation, absorption, ingestion or injection routes.

ionising radiation

Any form of radiation that is capable of ionising matter. Typically this ionisation takes the form of displacing an electron from an atom.

irradiation

The process of subjecting an entity to radiation.

LLW

Low-level radioactive waste.

made ground

Ground produced by infilling with material from outside the site or from another part of the site. Typically this could include rubble, gravel or sand or waste materials.

MOX

Mixed oxide fuel. A fuel for nuclear reactors that contains both uranium and plutonium oxides.

naturally occurring radionuclides

Radionuclides and their associated progeny produced during the formation of the earth or by interactions of terrestrial matter with cosmic rays.

neutron

Uncharged particle, constitutes approximately 50 per cent by mass of most atomic nucleii.

neutron flux

A measurement of the intensity of a neutron source (measured in Jcm^-2s^-1 or neutrons cm^-2s^-1).

NII

Her Majesty's Nuclear Installations Inspectorate (part of the HSE).

nuclear fission

Process by which an atom splits into two or more pieces, each of which is an entirely separate nuclide.

pathway

A mechanism or route by which a contaminant can reach, or be made to affect, a receptor.

permeability

The relative ease with which a porous medium can transmit a fluid under a hydraulic gradient.

pollutant linkage

The relationship of a contaminant, a pathway and a receptor.

PPE

Personal Protective Equipment - equipment used as a "last line of defence" to prevent a person from being exposed to a contaminant or contaminants.

precision

Level of agreement within a series of measurements of a parameter.

primordial radionuclides

Radionuclides produced during the initial formation of the earth. Those of the radionuclides that remain have very long half-lives.

putrescible waste

Organic waste that may decompose or rot.

quality factor

A factor applied to the absorbed dose in tissue to take account of the different levels of harm inflicted by different types of radioactive decay. Used to calculate equivalent dose.

radiation

Normally used in place of ionising radiation, radiation is the emission of energy by means of particles or waves.

Radiation Protection Adviser (RPA)

An appointment required under the Ionising Radiations Regulations 1999 for all companies involved in work with ionising radiations. The RPA is registered with the HSE and provides advice on all aspects of radiological protection. The RPA will set dose constraints on workers and specify hold points for use during the work.

Radiation Protection Supervisor (RPS)

An appointment required under the Ionising Radiations Regulations 1999 for all companies involved in work with ionising radiations. An RPS must have received training related to radiological protection and ensures that the specified safety restrictions are observed.

radioactive decay

The spontaneous transformation of an unstable atom into one or more different nuclides accompanied by either the emission of energy and/or particles from the nucleus, nuclear capture or ejection of orbital electrons, or fission. Unstable atoms decay into a more stable state, eventually reaching a form that does not decay further nor has a very long half-life.

radioactive material

Often used to describe any material containing radionuclides. The statutory definition of radioactive material is given in the Radioactive Substances Act 1993 (see Box 4.5).

radioactivity

The mean number of nuclear transformations occurring in a given quantity of radioactive material per unit time. The International System (SI) unit of radioactivity is the Becquerel (Bq).

radionuclide

An unstable nuclide that undergoes radioactive decay.

receptor

An entity (persons, living organisms, ecological systems, controlled waters, atmosphere, structures, utilities) that may be adversely affected by a contaminant.

risk

An assessment of the potential for harm or damage posed by a contaminant or circumstance taking account of the likelihood, or probability, of occurrence. Risk is the product of hazard and probability.

risk assessment

Process of establishing the existence, nature and significance of risk.

RPE

Respiratory Protective Equipment - any equipment designed to prevent a person from inhaling airborne contaminants.

sampling

Methods and techniques used to obtain a representative sample of the material under investigation.

scintillation detector

Radiation detector relying on the property of certain materials to fluoresce when ionised by radiation. The light produced is measured using a photomultiplier.

SEPA

Scottish Environmental Protection Agency.

Sievert

The name for the International System (SI) unit of equivalent dose or effective dose.

SNIFFER

Scotland & Northern Ireland Forum For Environmental Research.

SoLA

Substances of Low Activity Exemption Order. This specifies activity concentrations of radionuclides that are deemed to be exempt from all provisions of the Radioactive Substances Act 1993.

source

A contaminant which is in, on or under the land and which has the potential to cause harm to an identified receptor or to cause pollution of controlled waters.

special waste

Controlled waste of any kind that is or may be so dangerous or difficult to keep, treat or dispose of that special provision is required to deal with it.

supervised area

Any area where the annual effective dose to persons working there is likely to exceed 1 mSv or one-tenth of the appropriate dose limit.

topographical survey

A survey of the physical features of a site in three dimensions.

whole body dose

See effective dose.