Glossary - UK Radioactive Waste & Materials Inventory

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).
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.
DESNZ	Department for Energy Security & Net Zero.
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	His 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.
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.
NRS	Nuclear Restoration Services.
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?
NWS	Nuclear Waste Services.
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).
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 (UKAEA)	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.

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