Glossary

Activation

The capture of a free neutron by a stable non-radioactive atom, causing it to become radioactive. See What is radioactive waste?

ADU

Ammonium Diuranate

AETP

Active Effluent Treatment Plant (at reactor site)

AEWTP

Active Effluent Waste Treatment Plant (at reactor site)

AGR

Advanced Gas-cooled Reactor

AWE

Previously the Atomic Weapons Establishment, now known as AWE.  AWE develops nuclear warheads for the UK’s deterrent at Aldermaston and Burghfield in Berkshire

BAESM

BAE Systems Marine Ltd.; a company that designs, manufactures and services naval ships and submarines

BCD

Burst Cartridge (Can) Detection

Becquerel

Bq; the standard international unit of measurement of radioactivity – corresponding to one decay per second (see also kBq, GBq and TBq).

BEIS

The Department for Business, Energy & Industrial Strategy is a ministerial department that brings together responsibilities for business, industrial strategy, science, innovation, energy, and climate change.

BEP

Box Encapsulation Plant (at Sellafield)

BEPO

British Experimental Pile O.  Air-cooled graphite-moderated pile (at Harwell site; shut down in 1968)

Beta particle

Particle emitted from parent nucleus in beta decay with corresponding neutrino. Beta- decay results in electron emission with an antineutrino and Beta+ decay results in positron emission with a neutrino

Beta/gamma activity

Radioactivity associated with the emission of beta particles and/or gamma radiation

BPS

Berkeley Power Station

BTC

British Technology Centre (at Sellafield). Now known as National Nuclear Laboratory, Central Laboratory

C & M

Care and Maintenance

Capping material

Cement or other substance forming inactive cover over conditioned waste in a container

CCP

Cartridge Cooling Pond

CEGB

Central Electricity Generating Board

Characterisation

The process of assessing the composition of radioactive materials and wastes, and classifying them based on their levels of radioactivity, and physical and chemical properties

CHILW

Contact Handled Intermediate Level Waste

Clifton Marsh

Landfill site (near Preston)

Conditioned volume

The volume of waste after conditioning, consisting of the waste material and encapsulating matrix

Conditioned waste

Radioactive waste that has undergone conditioning

Conditioning

The process used to prepare waste for long-term storage and/or disposal by converting it into a solid and stable form, e.g. by encapsulation in cement

Conditioning matrix

The material used to contain and/or stabilise waste for disposal.  This may be cement, glass or polymer.

Contamination

Radioactive particles that have accumulated on an exposed surface by contact with a radioactive material or waste. See What is radioactive waste?

Controlled burial

The authorised disposal of some LLW, arising principally in the non-nuclear sector, at suitable landfill sites that possess good containment characteristics.

Crud

Any deposits of impurity or corrosion product within a reactor, storage vessel or chemical plant.

CVCS

Chemical Volume and Control System (PWR station)

CXPP

Chapelcross Process Plant.

DCIC

Ductile Cast Iron Container

DCP

Dounreay Cementation Plant.

Decommissioning

The process whereby a nuclear facility, at the end of its economic life, is taken permanently out of service and its site made available for other purposes

Decommissioning waste

Wastes arising after the shutdown of a facility associated with the use or handling of radioactive materials.  They can consist of plant or equipment, building debris and material from the clean-up of surrounding ground.

Depleted uranium

Uranium where the uranium 235 isotope content is below the naturally occurring 0.72% by mass.

DFR

Dounreay Fast Reactor (shut down in 1977)

DIDO

Heavy-water cooled and moderated materials testing reactor (at Harwell site; shut down in 1990).

Disposal

The emplacement of waste in a suitable facility without intent to retrieve it. (Retrieval may be possible but, if intended, the appropriate term is storage.)

DMTR

Dounreay Materials Test Reactor

DNLEU

Depleted, Natural and Low Enriched Uranium

Dragon

Experimental high temperature reactor project sited at Winfrith and funded by the Organisation for Economic Cooperation and Development (shut down in 1976).

DU

Depleted Uranium

EA

Environment Agency; the leading public body for protecting and improving the environment in England See How are sites regulated?

EARP

Enhanced Actinide Removal Plant (at Sellafield)

EAST

External Active Sludge Tanks (at Winfrith)

EFDA

European Fusion Development Agreement

Electron

Negatively charged fundamental particle in orbit about an atomic nucleus

Enriched uranium

Uranium where the uranium-235 isotope content is above the naturally occurring 0.72% by mass.

Enrichment

The process of increasing the abundance of fissionable atoms in natural uranium.

ENSREG

European Nuclear Safety Regulators Group

Euratom

European Atomic Energy Community

Ex situ

‘Off the site’ (in the context of waste disposal)

FED

Fuel Element Debris

FGMSP

First Generation Magnox Storage Pond (at Sellafield).

FHP

Fuel Handling Plant (at Sellafield)

Fission

Spontaneous or induced fragmentation of heavy atoms into two (occasionally three) lighter atoms, accompanied by the release of neutrons and radiation.

Fission products

Atoms, often radioactive, resulting from nuclear fission.

Flatrol

Type of railway wagon.  It is used for transporting fuel flasks.

Floc

A product of flocculation, a process that separates suspended contaminants from a liquid.

Fuel cladding

The metal casing around the fuel

Fuel stringer

A string of fuel element assemblies for an AGR.

Fusion

The process of fusing two or more atoms to form a heavier atom, releasing large amounts of energy. This is essentially the same process that occurs in the Sun.

GBq

Gigabecquerel, one thousand million (109) Becquerels.

GDA

Generic Design Assessment.

GDF

Geological Disposal Facility

GE Healthcare Ltd

A company that provides products and services for use in healthcare and life science research.  This includes radioisotopes for medical and research users.

Geological disposal

A long-term waste management option involving the emplacement of radioactive waste in an engineered underground geological disposal facility, where the geology (rock structure) provides a barrier against the escape of radioactivity and there is no intention to retrieve the waste once the facility is closed.

GLEEP

Graphite Low Energy Experimental Pile.  Low energy, graphite reactor (at Harwell site; shut down in 1990).

Government

A collective term for the central government bodies responsible for setting radioactive waste management policy within the UK.  It comprises the UK Government, the Scottish Government and the devolved administrations for Wales and Northern Ireland.

Grout

Material (typically cement) used to immobilise radioactive waste

Grouting

Process of immobilising radioactive waste in cement

HA

High Activity

HAL

Highly Active Liquor

Half life

The time it takes for the amount of radioactivity to decrease by 50%.

HAW

Higher Activity Waste.

HEU

Highly Enriched Uranium.  Uranium where the uranium-235 isotope content is 20% by mass or more.

Hex

Uranium Hexafluoride

HF

Hydrogen Fluoride

HLW

High Level Waste

HMNB

Her Majesty’s Naval Base

HVVLLW

High Volume Very Low Level Waste

IAEA

International Atomic Energy Agency; An international organisation working for the safe, secure and peaceful uses of nuclear science and technology

IFP

Insoluble Fission Products

ILW

Intermediate Level Waste.

In situ

‘On the site’ (in the context of waste disposal)

Irradiated fuel

Fuel that is being or has been used to power nuclear reactors.

ISO

International Organisation for Standardisation

Isotope

Atoms of the same element which have the same number of protons but different number of neutrons

IWS

Integrated Waste Strategy

JET

Joint European Torus – the internationally funded fusion project sited at Culham.

kBq

Kilobecquerel, one thousand (103) Becquerels.

LA

Low Activity

LAEMG

Low Active Effluent Management Group area (at Sellafield).

LA-LLW

Low Activity Low Level Waste

LAW

Lower Activity Waste

LETP

Liquid Effluent Treatment Plant

LEU

Low Enriched Uranium.  Uranium enriched in U-235 to less than 20% by mass.

LLLETP

Low Level Liquid Effluent Treatment Plant

LLRF

Low Level Refuelling Facility.

LLW

Low Level Waste

LLWR

The Low Level Waste Repository, south of Sellafield in Cumbria, has operated as a national disposal facility for LLW since 1959.

LQA

Land Quality Assessment

LSA

Low Specific Activity.

LWR

Light Water Reactor.

m3

Cubic metres – a measure of volume

MA

Medium Active

MAC

Miscellaneous Activated Component.

Magnox

An alloy of magnesium used for fuel element cladding in natural uranium fuelled gas-cooled power reactors. Also a generic name for this type of reactor.

MBGWS

Miscellaneous Beta Gamma Waste Store.

MBq

Megabecquerel, one million (106) Becquerels.

MCI

Miscellaneous Contaminated Items.

MEB

Multi-Element Bottle.  Container used to hold irradiated LWR fuel in cooling ponds prior to reprocessing.

MEP

Magnox Encapsulation Plant (at Sellafield).

MMMF

Man-Made Mineral Fibre

MOD

Ministry of Defence; UK government ministerial department

MODIX

Multi-stage Oxidative Decontamination with Ion-Exchange.  A process used, among other things, to clean the pressure vessels and primary circuit pipework of nuclear submarines prior to refuelling.

MOX

Mixed Oxide.  Refers to nuclear fuel consisting of uranium oxide and plutonium oxide for use in reactors.

MRWS

Managing Radioactive Wastes Safely

mSv

milliSievert, one thousandth of a Sievert

MTR

Materials Testing Reactor.

MWP

Minor Waste Producers

NDA

Nuclear Decommissioning Authority.  A non-departmental public body responsible for overseeing the decommissioning and cleanup of 17 of the UK’s civil public sector nuclear sites.

NDS

Commercial disposal service formerly operated by AEA Technology Harwell, sometimes referred to as the National Disposal Service.

NE

Not Estimated

NEA

Nuclear Energy Agency

Nimonic

An alloy of the elements nickel, chromium and other minor constituents.

NNL

National Nuclear Laboratory Limited.  A Government owned science and technology services company. 

NORM

Naturally Occurring Radioactive Material. These are materials that typically accumulate as scale on pipework during the extraction of oil and gas, and have raised levels of naturally occurring radioactivity

NRTE

Naval Reactor Test Establishment (at Vulcan, Dounreay)

NRW

Natural Resources Wales; Welsh Government Sponsored Body, responsible for making sure that the environment and natural resources of Wales are sustainably maintained, sustainably enhanced and sustainably used, now and in the future. See How are sites regulated?

NU

Natural Uranium

Nuclear fuel

Fuel used in a nuclear reactor.  Most fuel is made of uranium, and produces heat when the uranium atoms split into smaller fragments.

Nuclear fuel cycle

The sequence of activities involved in the production and use of nuclear fuel. See How is radioactive waste produced?

OECD

Organisation for Economic Co-operation and Development

ONR

Office for Nuclear Regulation; Organisation responsible for efficient and effective regulation of the nuclear industry, holding it to account on behalf of the public. See How are sites regulated?

Operational waste

Wastes arising from the day-to-day operations of a facility associated with the use or handling of radioactive materials.

Ore

Any naturally occurring mineral from which economically valuable constituents (e.g. metals) can be extracted.

Oxide

A chemical compound of oxygen and another element. For example, rust is an iron oxide which is a compound of iron and oxygen

Packaged volume

The volume of waste after packaging, consisting of the waste material, any encapsulating matrix, any capping grout and ullage, and the container.

Packaged waste

Radioactive waste that has undergone Packaging.

Packaging

The loading of waste into a container for long-term storage and/or disposal.  In most but not all cases this includes conditioning.

PCD

Primary Circuit Decontamination.

PCM

Plutonium Contaminated Material.

PFR

Prototype Fast Reactor (at Dounreay site; shut down in 1994)

PIE

Post Irradiation Examination, of fuel elements etc.

PLUTO

Heavy-water cooled and moderated materials testing reactor (at Harwell site; shut down in 1990).

Plutonium

A radioactive element created in nuclear reactors.  It can be separated from spent nuclear fuel by reprocessing.  Plutonium is used as a nuclear fuel, in nuclear weapons and as a power source for space probes.

POCO

Post Operational Clean Out.  Activity after final shutdown that prepares a plant for decommissioning.

Pond furniture

Various storage racks, skips, frames, containers and MEBs used for storing irradiated fuel in cooling ponds.

Pu

Plutonium.

PuO2

Plutonium dioxide

PWR

Pressurised Water Reactor

PWTP

Pond Water Treatment Plant (at reactor sites)

R&D

Research and Development

Radiation

The process of emitting (radiating) energy in the form of particles or electromagnetic waves. See What is radiation?

Radioactive decay

The splitting of an unstable nucleus, releasing energy in the form of particles (alpha and beta), neutrons or electromagnetic energy (gamma rays)

Radioactivity

A property possessed by some atoms that split spontaneously, with release of energy through emission of a sub-atomic particle and/or radiation.

Radiopharmaceuticals

Drugs that contain radioactive materials

Radionuclide

A general term for an unstable nuclide that emits ionising radiation (e.g. cobalt-60).

Raffinate

A solution resulting from a solvent extraction process.  The term is applied to the aqueous solution of fission products (liquid HLW) remaining after the extraction of uranium and plutonium in the first stage or irradiated fuel reprocessing.

Reprocessing

The chemical extraction of reusable uranium and plutonium from waste materials in spent nuclear fuel.

RHILW

Remote Handled Intermediate Level Waste.

RRF

Residue Recovery Facility (at Capenhurst)

RRMPOL

Rolls-Royce Marine Power Operations Ltd.; a company that designs, supplies and supports marine power and propulsion systems

RV

Resin Vault (at Trawsfynydd).

RWM

Radioactive Waste Management; A subsidiary of the Nuclear Decommissioning Authority (NDA) responsible for the delivery of a geological disposal facility

Safeguards

Nuclear safeguards are measures to verify that countries abide by their commitments to use nuclear material for declared peaceful purposes.

Safety case

A set of documents that describe the radiological hazards in terms of a facility or site and operation. It also includes the measures that prevent or mitigate against harm

SDP

Sodium Disposal Plant (at Dounreay)

SDP

Submarine Dismantling Project

Sealed radioactive sources

Container of enclosed radioactive material used in medicine, agriculture, industry and other industries

SEP

Silo Emptying Plant (at Sellafield)

SEPA

Scottish Environment Protection Agency; Scotland’s principal environmental regulator, protecting and improving Scotland’s environment. See How are sites regulated?

SETP

Segregated Effluent Treatment Plant (at Sellafield).

SGHWR

Steam Generating Heavy Water Reactor (at Winfrith site). Shut down in 1990.

Sievert

Sv; the standard international unit of measurement for ionising radiation dose

SIXEP

Site Ion Exchange Plant (at Sellafield)

SLC

Site Licence Company

Small users

Organisations that use radioactive materials and create radioactive wastes that are not part of the nuclear sector licensed under the Nuclear Installations Act 1965 (as amended), including hospitals, universities and industrial undertakings.

SMP

Sellafield MOX Plant

Spent fuel

Fuel that has been used in nuclear reactors that is no longer capable of efficient fission due to the loss of fissile material. 

SPF

Sand Pressure Filter

SPP

Sludge Packaging Plant (at Sellafield)

Storage

The emplacement of waste in a suitable facility with the intent to retrieve it at a later date.

Supercompaction

A general term that describes the reduction in bulk volume by the application of high external force.  It differs from routine compaction methods by using hydraulic equipment capable of exerting forces of 1,000-2,000 tonnes, and the original container (metal drum or box) is supercompacted along with its contents.  Waste is often precompacted into steel drums or boxes prior to supercompaction of the drum or box.

SWR

SIXEP Waste Retrieval

TBq

Terabecquerel, one million million (1012) Becquerels.

Tc

Technetium, an element atomic number 43.

te

Tonnes

tHM

Tonnes of heavy metal.  A unit of mass used to quantify uranium, plutonium and thorium including mixtures of these elements.

Thorium

Thorium is a naturally occurring radioactive element that can be mined, extracted and processed to make fuel for certain reactors. 

Thorp

Thermal Oxide Reprocessing Plant (at Sellafield site)

THTR

Thorium High Temperature Reactor

TILWSP

Transportable Intermediate Level Waste Solidification Plant.

Treatment

A process that changes the state or form of radioactive waste to facilitate its future management.  It may or may not serve to put the waste into its finally conditioned form.

Tritiated

Containing tritium

Tritium

An isotope of hydrogen (H-3) having a radioactive half-life of about 12 years.

TSSBN

Trident Ship Submersible Ballistic Nuclear.  A nuclear powered submarine with Trident ballistic nuclear missiles.

tU

Tonnes of Uranium – a measure of mass.

U-235

Uranium-235 is the main fissile isotope of uranium. Natural Uranium typically contains 0.72% by weight of U-235.

U3O8

Triuranium octoxide

UF4

Uranium tetrafluoride

UF6

Uranium hexafluoride

Ullage

The space remaining within a container above the conditioned waste matrix and any capping material.

Unirradiated fuel

Fuel that has not yet been used to power nuclear reactors. 

United Kingdom Atomic Energy Authority

A public body that manages the UK fusion research programme and operates the Joint European Torus (JET).  Originally formed in 1954 to carry out nuclear research for the UK Government.

UO2

Uranium dioxide

UO3

Uranium trioxide

Uranium

A radioactive element that occurs in nature.  Uranium is used for nuclear fuel and in nuclear weapons.

Vitrification

The process of converting materials into a glass or glass-like form.  Vitrification is the process used at Sellafield to convert liquid HLW from spent fuel reprocessing into a borosilicate glass.

VLLW

Very Low Level Waste

Vulcan 

The Naval Reactor Test Establishment (NRTE), located adjacent to the Dounreay site on the north coast of Scotland.

WAC

Waste Acceptance Criteria

WAGR 

Windscale Advanced Gas-cooled Reactor (shut down in 1981)

WAMAC

Waste Monitoring and Compaction facility (at Sellafield site)

Waste hierarchy

The waste hierarchy sets out the priority order for managing waste materials based on their environmental impacts

Waste package

A container and its content of conditioned radioactive waste.

WCH

Waste Characterisation form.  The WCH is part of the LLWR’s waste acceptance procedure.  It has replaced the Waste Stream Characterisation Document (WSCD).

WEP

Wastes Encapsulation Plant (at Sellafield)

WETP

Winfrith East Treatment Plant

WPEP

Waste Packaging and Encapsulation Plant (at Sellafield)

WRACS

Waste Receipt Assay Characterisation and Supercompaction facility (At Dounreay)

WRAT

Waste Requiring Additional Treatment

WSDS

Waste Stream Data Sheets

WTC

Waste Treatment Complex (at Sellafield)

WVP

Waste Vitrification Plant (at Sellafield)

Yellowcake

Concentrated uranium oxide obtained through the milling of uranium ore in the form of a yellow powder. It is the raw material for making nuclear fuel.

ZEBRA

Zero Energy Breeder Reactor Assembly.  ZEBRA was a fast reactor that operated from 1962 to 1982 at Winfrith. 

Zenith reactor

A research reactor at Winfrith that has been decommissioned. 

Zircaloy

An alloy of the element zirconium used for the cladding of nuclear fuel – particularly in water reactors.