Scotland's higher-activity radioactive waste policy: supplementary information

SECTION 4 GLOSSARY

Accessible environment

Those parts of the environment in contact with or readily available for use by humans.

Active institutional control

Control of a disposal site for solid radioactive waste by an authority or institution authorised under RSA 93, involving monitoring, surveillance and remedial work as necessary, as well as control of land use.

Activity

The number of atoms of a radioactive substance which decay (radioactive decay) by nuclear disintegration each second. The unit of activity is the Becquerel (Bq).

Advanced Gas-cooled Reactor ( AGR)

The reactor type used in the UK's second generation nuclear power plants.

ALARA (as low as reasonably achievable)

The ALARA principle is contained in the Euratom Basic Safety Standards Directive 96/29, which is transposed into UK law. Essentially, it means that all reasonable steps should be taken to protect people. In making this judgement, factors such as the costs involved in taking protection measures are weighed against benefits obtained, including the reduction in risks to people.

Alpha radiation

Alpha radiation takes the form of particles (helium nuclei) ejected from a decaying (radioactive) atom. Alpha particles cause ionisation in biological tissue which may lead to damage. The particles have a very short range in air (typically a few cm) and alpha particles present in materials that are outside of the body are prevented from causing biological damage by the superficial dead skin cells, but become significant if inhaled or swallowed.

Annual dose constraint

A restriction on annual dose of 0.3 millisieverts (mSv) to an individual from a single source of radiation exposure, applied at the design and planning stage of any activity to ensure that when aggregated with doses from all sources, excluding natural background and medical procedures, the dose limit (1mSv per annum) is not exceeded. The UK dose constraint derives from international advice.

Assay methods

Methods used to estimate the total radionuclide content of a waste type. This includes external measurements of dose rate at the surface of the waste and sampling of the waste itself.

Assessed radiological risk

See Radiological risk.

Authorised discharge limit

A limit on the discharge of one or more specified radionuclides to air or water in accordance with an authorisation under RSA 93.

Backfill

The materials used to fill in and close off the void areas or an underground repository, such as vaults, silos, and drift tunnels, which usually occurs after the radioactive waste has been emplaced; thus "backfilling the waste".

Baseline inventory

An estimate of the higher activity radioactive waste and other materials that could be regarded as wastes.

Becquerel (Bq)

The standard international unit of radioactivity equal to one radioactive decay per second. Becquerels are abbreviated to Bq. Multiples of Becquerel's commonly used to define radioactive waste activity are: kilobecquerels (kBq) equal to 1 thousand Bq; megabecquerels ( MBq) equal to 1 million Bq; gigabecquerels ( GBq) equal to 1 thousand million Bq; terabecquerels ( TBq) equal to 1 million million Bq.

Biosphere

That part of the environment normally inhabited by living organisms. In practice, the biosphere is generally taken to include the atmosphere and the Earth's surface, including the soil and surface water bodies, seas and oceans and their sediments. There is no generally accepted definition of the depth below the surface at which soil or sediment ceases to be part of the biosphere, but this might typically be taken to be the depth affected by basic human actions, in particular farming.

Borehole

A cylindrical excavation, made by a drilling device. Boreholes are drilled during site investigation and testing and can also be used for waste emplacement in repositories and monitoring.

Borehole disposal

The concept of disposing of some forms of radioactive waste in extremely deep boreholes, a number of kilometres down in the Earth's crust.

Best Practicable Environmental Option ( BPEO)

In the context of authorisations under Radioactive Substances Act 1993 ( RSA93), for nuclear sites, the options' assessment method currently used is Best Practicable Environmental Option ( BPEO). BPEO was described by the Royal Commission on Environmental Pollution, Twelfth Report (Cm 210) 1988 as "…. the outcome of a systematic and consultative decision-making procedure which emphasises the protection and conservation of the environment across land, air and water. The BPEO procedure establishes, for a given set of objectives, the option that provides the most benefit or least damage to the environment as a whole, at acceptable cost, in the long-term as well as in the short term". A BPEO study is usually carried out by or on behalf of the waste producer and assessed by the relevant environment agency as a basis for its regulatory decision-making.

Best Practicable Means ( BPM)

BPM is a term used by the Environment Agency ( EA) and Scottish Environment Protection Agency ( SEPA) in authorisations issued under the Radioactive Substances Act. Essentially, it requires operators to take all reasonably practicable measures in the design and operational management of their facilities to minimise discharges and disposals of radioactive waste, so as to achieve a high standard of protection for the public and the environment. BPM is applied to such aspects as minimising waste creation, abating discharges, and monitoring plant, discharges and the environment. It takes account of such factors as the availability and cost of relevant measures, operator safety and the benefits of reduced discharges and disposals. If the operator is using BPM, radiation risks to the public and the environment will be ALARA.

Beta radiation

Beta radiation takes the form of particles (electrons) emitted from the nucleus of a decaying (radioactive) atom. Beta particles cause ionisations in biological tissue which may lead to damage. Most beta particles can pass through the skin and penetrate the body, but a few millimetres of low density materials, such as aluminium, will generally stop them.

Beta/gamma radiation

Beta radiation is usually accompanied by the emission of gamma rays, hence the term "beta/gamma radiation".

Chapelcross

Site of a Magnox power station (four reactors) in Dumfriesshire that opened in 1959. It was the first nuclear power station in Scotland. Operations ceased in June 2004.

Clean-up

The decontamination and decommissioning of a nuclear licensed site.

Closure

Technical and administrative actions to put a Disposal facility in its intended final state after the completion of waste Emplacement.

Cm2919

The Command White Paper "Review of Radioactive Waste Policy - Final Conclusions" (1995); although to an extent overtaken by events, this remains an important statement of the UK Government's position on radioactive waste.

Collective radiological impact

An indicator of the total radiological consequences from a particular source of exposure on a defined population over some period of time.

Concentrate and contain

A term normally used to describe a form of management for radioactive waste where radioactivity is concentrated and contained to prevent its migration into the environment and facilitate its management.

Conceptual model

A set of qualitative assumptions used to describe a system, or part of a system, in the real world.

Conditioned waste

Radioactive waste that has been treated or processed by converting it to a solid stable form in preparation for long-term storage or disposal.

Conservative (of assumptions and data)

Selection of cautious assumptions, or worst case data values, for the purposes of modelling.

Consignment

Any load of radioactive material, packaged or unpackaged, that is presented for transport.

Consignor (of waste)

An organisation or person that sends waste to a facility for disposal.

Controlled burial

Also known as "special precautions burial". A process of disposal for solid LLW that has an activity level above that which would allow it to be disposed of as VLLW. Controlled burial takes place at landfill sites used for the deposit of substantial quantities of ordinary refuse but which are approved for the disposal of radioactive substances. Controlled burial has various limitations placed on its use in terms of maximum activity per waste container, type of container, surface dose rate of container, and depth of burial beneath earth or ordinary waste.

Criticality

The point at which a nuclear chain reaction occurs as a result of the concentration of certain types of radioactive materials.

Decay chains

These generally refer to the three naturally occurring series of radionuclides, all of which start with a single parent nuclide (uranium-238, uranium-235 and thorium-232) each of which decays via a number of radioactive daughters of different half lives and activity type (i.e. alpha or beta/gamma radiation), eventually ending with stable nuclides of lead.

Decay storage

The process of allowing material containing short-lived radionuclides to decay (see half life) so that the final waste is less radioactive and easier to dispose of as radioactive waste, or until the point where the waste becomes exempt from specific regulatory requirements. Used extensively in hospitals and research establishments, and to some extent by the nuclear industry.

Decision point

A point defined in a voluntary agreement where a developer would seek regulatory agreement before proceeding with an activity. This would generally be before decisions by the developer to invest substantial amounts of time and resources.

Decommissioning

The process whereby a nuclear facility, at the end of its economic life, is taken permanently out of service. The term "site clean-up" is sometimes used to describe the work undertaken to make the site available for other purposes.

Decommissioning wastes

These wastes are produced during the dismantling of nuclear facilities, and make up the bulk of the higher activity waste that will be produced in Scotland. The majority of these wastes are made up of graphite, metals and concrete, from reactors and will need to be managed when the reactors are dismantled.

Decontamination

Removal or reduction of radioactive contamination.

Delicensing

The process of removal from regulatory control by the Health and Safety Executive, of a nuclear site, which has been licensed under the Nuclear Installations Act 1965.

Depleted uranium

Uranium containing a lesser mass percentage of uranium-235 than in natural uranium.

Deterministic assumption

Fixed assumption, taken to have a probability of 1, made for the purpose of exploring, developing, or establishing the environmental safety case.

Developer (of a disposal facility)

The organisation responsible for developing a disposal facility before waste disposal begins.

Devolved administrations

Collective term for the Scottish Government, Welsh Assembly Government and the Department of Environment Northern Ireland.

Dilute and disperse

A term normally describing a form of management for radioactive waste where radioactivity is released from a facility as a gas or liquid and is diluted in the air or marine environment.

Disposability

The degree to which packaged conditioned waste meets the standards for final disposal.

Disposal

In the context of solid waste, disposal is the emplacement of waste in a suitable facility without intent to retrieve it at a later date; retrieval may be possible but if retrievability is intended, the appropriate term is storage.

Disposal facility (for solid radioactive waste)

An engineered facility for the disposal of solid radioactive wastes.

Disposal system

All the aspects of managing the waste, the disposal facility and its surroundings that affect the radiological impact.

Dose

A general term used as a measure of the dose absorbed by man from radiation, measured in sieverts, and its sub-multiples (millisieverts - mSv - equal to one thousandth of a sievert, or microsieverts, equal to one millionth of a sievert). Radiation dose is received from many sources - of the average annual dose of 2.6 mSv, 85 per cent comes from natural background radiation, 14 per cent from medical sources and the remaining one per cent from miscellaneous man-made sources.

Dose guidance level (for human intrusion)

In the context of near-surface disposal facilities, the dose standard against which the radiological consequences of human intrusion are assessed. It indicates the standard of environmental safety expected but does not suggest that there is an absolute requirement for this level to be met.

Dounreay

Located in Caithness on the north coast of Scotland, the site was established on a former naval base as the centre for UK fast reactor research. It is now engaged on a major decommissioning and site restoration programme to deal with the legacy of past operations.

Drigg

Site of the National Low Level Waste repository in Cumbria.

Emplacement (of waste in a disposal facility)

The placement of a waste package in a designated location for disposal, with no intent to reposition or retrieve it subsequently.

Encapsulation

Immobilisation of waste by mixing it with a matrix material within a container in order to produce a more solid and stable waste form.

Energy Act 2004

An Act of Parliament which, inter alia, established the NDA and set out its duties and responsibilities for the decommissioning and clean-up of the UK's public civil nuclear sites.

Environment Act 1995

An Act of Parliament which established the Scottish Environment Protection Agency ( SEPA) in Scotland and the Environment Agency ( EA) in England and Wales.

Environmental Impact Assessment ( EIA)

A legal requirement under EU Directive 85/337/ EEC (as amended) for certain types of project, including various categories of radioactive waste management project. It requires information on the environmental impacts of a project proposal to be submitted by the developer and evaluated by the relevant competent authority (the planning authority, HSE or other regulators concerned).

Environmental safety

The safety of people and the environment both at the time of Disposal and in the future.

Environmental safety case

The collection of arguments, provided by the developer or operator of a disposal facility, that seeks to demonstrate that the required standard of Environmental safety is achieved.

Environmental safety culture

The characteristics and attitudes of organisations and individuals that ensure that the protection of people and the environment receives proper attention.

Environmental safety functions

The various ways in which components of the disposal system may contribute towards environmental safety, e.g. the host rock may provide a physical barrier function and may also have chemical properties that help to retard the migration of radionuclides.

Environmental safety strategy

An approach or course of action designed to achieve and demonstrate environmental safety.

Euratom Treaty

The legislative basis for the activities of European Union countries in the nuclear energy field.

European Commission ( EC)

The executive body of the European Union. Its primary roles are to propose and implement legislation, and to act as guardian of the treaties which provide the legal basis for the European Union.

European Union ( EU)

The European Union of countries of which the United Kingdom is a member. The EU issues its own legislation which the UK, as a member state, is obliged to follow.

Exemption Order ( EO)

The Radioactive Substances Act 1993 ( RSA93) makes provision for certain low activity materials and wastes, when used for certain purposes and when managed in particular ways, to be exempt from particular regulatory provisions made under the Act.

Exempt waste

Radioactive wastes are considered exempt from regulatory control if they fall outside the scope of RSA 93 or there is an extant exemption order.

Exposed group

For a given source, any group of people within which the exposure to radiation is reasonably homogeneous; where the exposure is not certain to occur, the term 'potentially exposed group' is used.

Fission

Fission is the splitting of a nucleus into two or more pieces which can produce further chain reactions.

Fit for purpose

A term applied to waste disposal facilities which are engineered to a degree that is commensurate with the types of wastes they will receive.

Fuel/Nuclear Fuel

Material containing fissile nuclides which, in a reactor, produces the neutrons necessary to sustain a neutron chain reaction.

Fusion

A nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy

Gamma radiation

An electromagnetic radiation similar in some respects to visible light, but with higher energy. Gamma rays cause ionisations in biological tissue which may lead to damage. Gamma rays are very penetrating and are attenuated only by shields of dense metal or concrete, perhaps some metres thick, depending on their energy. Their emission from a radionuclide during radioactive decay is usually accompanied by particle emission (beta or alpha particles ).

Geological disposal

A long term management option involving the emplacement of radioactive waste in an engineered underground geological disposal facility or repository, 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.

Groundwater pathway

When water flows underground, it finds a route through the rock via cracks and fissures to flow to its destination. This is termed the groundwater pathway; drinking water is frequently obtained by drilling into underground reservoirs on the groundwater pathway. This is one route through which radioactivity from a geological depository could be brought back to the surface.

Grouting

A means of encapsulating radioactive waste by mixing it with, for example, cementatious material.

Guidance on Requirements for Authorisation ( GRA)

A 2009 document issued by the EA, SEPA and DOE Northern Ireland entitled "Near -surface Disposal Facilities on Land for Solid Radioactive Wastes".

Half-life

The time required for one half of the atoms of a given amount of a particular radionuclide to disintegrate through radioactive decay. Each radionuclide has a unique half-life, and half lives vary from fractions of a second through to many thousands of years.

Hazard

A property or situation that in certain circumstances could lead to harm.

Heat generating waste

Waste that generates heat above a particular level as it decays, a specific attribute of High Level Radioactive Waste. The heat generated decreases with time.

High Level Waste ( HLW)

Radioactive wastes in which the temperature may rise significantly as a result of their radioactivity, so this factor has to be taken into account in the design of storage or disposal facilities.

Higher activity radioactive waste - definition for Scottish Government higher activity waste policy

It includes the following categories of radioactive waste: high level waste, intermediate level waste, a small fraction of low level waste with a concentration of specific radionuclides.

Highly enriched uranium

Uranium in which the proportion of the isotope uranium-235 has been increased above a concentration of 20%.

Hold point

A point defined in an appropriate regulatory document, beyond which an activity must not proceed without regulatory approval. A hold point would generally be before a decision by the developer to invest substantial amounts of time and resources.

Human intrusion

Any human action that accesses the waste or that damages a barrier providing an environmental safety function after the period of authorisation.

Hunterston A

A Magnox power station in Ayrshire which opened in 1964 and ceased operation in 1989.

Immobilisation

Conversion of waste into a less mobile or non-mobile form by, for example, grouting or encapsulation.

Incineration

A waste treatment process of burning combustible waste which reduces its volume and produces residues which contain the original radioactivity although at a higher concentration.

Integrated Waste Strategies ( IWS)

An integrated waste strategy is not a legal requirement but is required of contractors working under the auspices of the NDA. It covers solid radioactive waste in all waste categories (i.e. LLW, ILW, HLW).

Intergenerational equity

An ethical concept which means the consideration by the present generation who have created (and benefited from use of) radioactive materials, of the role of future generations in the management of long lived radioactive waste.

Intermediate level waste ( ILW)

Radioactive wastes exceeding the upper activity boundaries for LLW but which do not need heat to be taken into account in the design of storage or disposal facilities.

Inventory limits

Limits and conditions set by the regulators on volumes, radionuclides and/or activity concentrations for waste disposal.

Ionisation

When radiation (alpha, beta, and gamma activity) interacts with matter, it can cause atoms and molecules to become unstable (creating ions). This process is called ionisation. Ionisation within biological tissue from radiation is the first stage in radiation leading to possible change or damage within the tissue.

Ionising radiation

Radiation that produces ionisation in matter, for example alpha particles, beta particles, gamma rays, x-rays and neutrons. When radiations such as these pass through the tissues of the body, they have sufficient energy to damage DNA.

Ionising Radiations Regulations 1999 ( IRR99)

The main legal requirements, enforced by the HSE, concerning the control of exposure to radiation arising from the use of radioactive materials and radiation generators in work activities.

Landfill

The disposal of waste by shallow burial. Modern landfills are lined to reduce seepage of material from the site into the environment, and once full, are capped to reduce rainfall entering the site. The EU Directive on the landfill of waste (Council Directive 99/31/ EC) set targets for the reduction of biodegradable municipal waste sent to landfill.

Legacy waste

Radioactive waste which already exists or which will arise from current (as at 2009) planned nuclear site operations.

Liabilities

The costs involved in decommissioning; the processing, long term management, storage and final disposal of waste materials and spent fuel; and the environmental remediation of nuclear sites.

Low Level Waste Repository ( LLWR)

The Low Level Waste Repository near the village of Drigg in West Cumbria has operated as a disposal site since 1959.

London Dumping Convention

The London Convention of 1972 is an international treaty that limits the wastes that can be disposed of at sea.

Long lived waste

Radioactive waste that contains radionuclides that have a half-life or more than 30 years.

Low Level Waste ( LLW)

LLW is defined as "radioactive waste having a radioactive content not exceeding 4 gigabecquerels per tonne ( GBq/te) of alpha or 12 GBq/te of beta/gamma activity".

Luminising

The process of using a radionuclide with a material that emits light when irradiated, for example, radium was used in old watches and instrument dials so their numbers could be seen as a green glow in the dark.

Magnox

The magnesium alloy used as a cladding material in Magnox fuel.

Magnox reactor

A term for the first generation of British power reactors (at Berkeley, Bradwell, Calder Hall, Chapelcross, Dungeness A, Hinkley Point A, Hunterston A, Oldbury, Sizewell A, Trawsfynydd and Wylfa) from the use of "Magnox" as the cladding material

Managing Radioactive Waste Safely ( MRWS)

A phrase covering the whole process of public consultation, work by CoRWM,

and subsequent actions by Government, to identify and implement the option, or combination of options, for the long term management of the UK's higher activity radioactive waste.

Maritime and Coastguard Agency ( MCA)

Body with responsibility for developing, promoting and enforcing high standards of marine safety within British territorial waters and ports.

Millisievert (mSv)

See dose

Mixed Oxide Fuel ( MOX)

Nuclear fuel consisting of uranium oxide and plutonium oxide for use in nuclear reactors.

Model

A representation or description of a system (or part of a system) in the real world, designed to show or explore how the system would behave under specified conditions.

Moderator

A substance used in a nuclear reactor to slow down fast neutrons

Monitoring

Taking measurements to demonstrate compliance with regulatory requirements and to provide reassurance to the public. This may include measuring levels of radioactivity in samples taken from the environment, and also measuring geological, physical and chemical parameters that are relevant to Environmental safety and that might change as a result of construction and operation of any facility for radioactive waste treatment, storage or disposal.

MOX (Mixed Oxide Fuel)

Fuel made up of around 95% uranium and 5% plutonium.

Multi barrier concept

Two or more natural or engineered barriers used to isolate radioactive waste in, and prevent radionuclide migration from a repository.

Multiple-function environmental safety approach

An approach to Environmental safety which relies on multiple Environmental safety functions.

NDPB (Non-Departmental Public Body)

A non-departmental public body ( NDPB) is a national or regional public body, working independently of ministers to whom they are nevertheless accountable.

Near-surface disposal facilities

Facilities located at the surface of the ground or at depths down to several tens of metres below the surface. Near-surface facilities may use the geology (rock structure) to provide an environmental safety function, but some may rely solely on engineered barriers.

Neutrons

Elementary particles of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen

New build

New build of a nuclear power station.

Non-Governmental Organisations ( NGOs)

In its broadest sense, a non-governmental organisation is one that is not directly part of the structure of Government.

Non-nuclear industry waste

Non-nuclear industry waste is a general term for the radioactive waste produced by those industries and organisations that use radioactive materials but are not involved in the production or nuclear energy or nuclear weapons. These industries are typically in the medical, educational, industries and oil and gas sectors. The nature of non-nuclear industry radioactive waste and the radionuclides contained in it vary widely because of the wide-ranging use of radioactive substances in the non-nuclear industry.

Non-nuclear premises

Premises registered by one of the environment agencies to keep and use radioactive materials or authorised to accumulate or dispose of radioactive waste under the Radioactive Substances Act 1993. Non-nuclear premises include hospitals, universities and some industrial premises. Non-nuclear premises are not licensed by the Nuclear Installations Inspectorate (part of HSE).

Nuclear energy

Energy obtained by nuclear fission or fusion.

Nuclear fission

See fission

Nuclear fuel cycle

All nuclear fuel related operations associated with the production of nuclear energy, including: the mining and milling of ores, enrichment, manufacture or fuel, operation of nuclear reactors, spent fuel reprocessing, and all related radioactive waste management activities.

Nuclear fusion

See fusion

Nuclear Installations Act 1965 ( NIA65)

UK legislation which provides for the operation and regulation of nuclear installations within the UK.

Nuclear licensed site

Any site which is the subject of a licence granted by the Nuclear Installations Inspectorate (part of HSE) under the Nuclear Installations Act 1965. Nuclear licensed sites include nuclear power stations, nuclear fuel production and reprocessing sites, sites undertaking storage of and/or research into nuclear materials, and major plant producing radioisotopes.

Nuclear Safeguards

Measures to verify that States comply with their international obligations not to use nuclear materials (plutonium, uranium and thorium) for nuclear explosives purposes. Global recognition of the need for such verification is reflected in the requirements of the Treaty on the Non-Proliferation of Nuclear Weapons ( NPT) for the application of safeguards by the International Atomic Energy Agency ( IAEA). Also, the Treaty Establishing the European Atomic Energy Community (the Euratom Treaty) includes requirements for the application of safeguards by the European Commission.

Nuclear safety case

Documentation provided by a nuclear site licensee to demonstrate that the site meets the nuclear safety requirements of the Nuclear Installations Inspectorate (part of HSE).

Nuclear security

Protection of nuclear licensed sites and the nuclear material on them. This includes, for example, physical protection, the roles of security guards and the UK's Civil Nuclear Constabulary, protection of sensitive data and technologies, and the trustworthiness of the individuals with access to them.

Nuclear technology

Technology that involves the reactions of the nuclei of atoms. It forms the basis for nuclear power plants and supporting research and operations.

Nuclear waste

A general term for the radioactive waste produced by those industries involved with nuclear energy and nuclear weapons' production.

Nuclide

An atom specified by its atomic number and atomic mass.

Operational Environmental Safety Case

The compilation of documents prepared for consideration by the EA, demonstrating that the public are sufficiently protected whilst the LLWR near Drigg is under institutional control, from hazards which may arise as a result of the disposal of radioactive wastes on the site, in accordance with an authorisation under RSA93.

Operational wastes

These radioactive wastes are produced during the research or power production activities that take place on the nuclear sites. Examples of operational waste include laboratory consumables or fuel debris, which is produced during the management of spent fuel and comprises parts of the fuel casings.

Operator (of a disposal facility)

The organisation responsible for operating a disposal facility after waste emplacement has begun. This operator will need to hold an authorisation under RSA 93.

Optimisation

Optimisation is the process of ensuring that all radiation exposures of the public are as low as reasonably achievable (see ALARA). Optimisation is achieved by employing best practicable means ( BPM). Optimisation, justification and limitation are the three key principles of radiation protection recommended by the International Commission on Radiological Protection in 1990 and which form the basis of European Community and UK legislation.

Options assessment

See Best Practicable Environmental Option

OSPAR (Oslo - Paris convention)

Convention which established requirements on the level of nuclear and non-nuclear discharges to the marine environment of the North East Atlantic, the North Sea and the Irish Sea.

Overpacking

A secondary outer container for one or more waste packages, used for handling, transport, storage and/or disposal.

Packaged radioactive waste

The loading of waste into a container for long term storage and/or disposal. In most cases this included conditioning of the waste and is in accordance with the requirements for handling, transport, storage and /or disposal.

Partitioning

The separating out, by physical and chemical methods, or radioactive elements contained in a waste stream to permit their further treatment.

Passive safety

The need to provide and maintain a safety function by minimising the need for active safety systems, monitoring or prompt human intervention. Requires radioactive wastes to be immobilised and packaged in a form that is physically and chemically stable. The package should be stored in a manner that is resistant to degradation and hazards, and which minimises the need for control and safety systems, maintenance, monitoring and human intervention.

Period of authorisation

The period of time while disposals are taking place and any period afterwards while the site is under active institutional control.

Planning authorities

A general term for those regional planning bodies and local authorities throughout the UK who are responsible for the preparation of planning strategies and for determining applications for construction and operation of waste treatment and disposal facilities that may be sited in their area of responsibility.

Plutonium

A radioactive element occurring in very small quantities in nature in uranium ores but mainly produced artificially, e.g. in nuclear reactors. Plutonium can be separated from spent nuclear fuel by reprocessing. Plutonium can be used in nuclear fuel, in nuclear weapons and as a power source for space probes.

POCO (Post Operational Clean Out)

The first stage in preparing nuclear plant for care and maintenance after operations have ceased.

Post-Closure Safety Case

The compilation of documents prepared for consideration by the environment agencies, demonstrating that the public will be sufficiently protected after the period of institutional control, from hazards which may arise as a result of the disposal of radioactive waste at the LLWR near Drigg, in accordance with an authorisation under RSA93.

Potential exposure (to ionising radiation)

Exposure to ionising radiation that is not certain to occur.

Potentially exposed group

See Exposed group.

Pressurised Water Reactor ( PWR)

Reactor type using ordinary water under high pressure as coolant and neutron

moderator. PWRs are widely used throughout the world for electricity generation. The Sizewell B reactor in Suffolk is of this design.

Probability distribution (of dose)

A distribution of exposures to ionising radiation that expresses the probability that a given exposure or range of exposures will occur.

Prospective dose

An assessed dose of the future radiological impact of proposed discharges of

radioactive waste into the environment.

Proximity principle

The Proximity Principle is a key element of EU environmental and municipal waste management policy. It was introduced in Article 5 of the Waste Framework Directive (75/442/ EEC as amended by Directive 91/156/ EEC) in 197, and is incorporated into UK waste strategy documents (see ref 11 in the Policy Statement). It means to enable waste to be disposed of in one of the nearest appropriate installations.

Radiation stability

The ability of a material to withstand radiation damage.

Radioactive decay

The process by which radioactive material loses activity, e.g. alpha activity naturally. The rate at which atoms disintegrate is measured in Becquerels.

Radioactive half-life

See half-life.

Radioactive material

Material designated in national law as being subject to regulatory control because of its radioactive properties.

Radioactive Substances Act 1993 ( RSA 93)

UK legislation which governs the keeping and use of radioactive material and the accumulation and disposal of radioactive waste. The Radioactive Substances Act is regulated by the environment agencies, i.e. SEPA in Scotland, the EA in England and Wales and the NIEA in Northern Ireland.

Radioactive waste

Any material contaminated by or incorporating radioactivity above certain thresholds defined in legislation, and for which no further use is envisaged, is known as radioactive waste.

Radioactively contaminated land

Land that is contaminated with radioactivity from past practices or work activities, or from the after-effects of radiological incidents, and which may give rise to harm to people. Intervention should be considered for land which is contaminated to the extent that a dose of 3mSv/year may be received by any individual.

Radioactivity

Atoms undergoing spontaneous random disintegration, usually accompanied by the emission of radiation.

Radioisotope

Different radioactive forms of the same element, for example caesium-134 and caesium-137 are both radioisotopes of the element caesium.

Radiological capacity of a disposal facility

An inventory of radioactive material that a facility is capable of accepting based on the environmental safety case.

Radiological risk

The probability per unit time that an individual will suffer a serious radiation-induced health effect as a result of the presence of a radiation source, for example, a disposal facility. In this context, a serious radiation-induced health effect includes three components: (a) fatal cancer adjusted for loss of life expectancy; (b) non-fatal cancer adjusted for life impairment; and (c) severe heritable effects. Radiological risk can only be assessed and not measured.

Radionuclide

A term which refers to a radioactive form of an element, for example, carbon-14 and caesium-137.

Reactor core

That part of the reactor which contains the fuel elements

Reactor pressure vessel

A reactor vessel designed to withstand a substantial operating pressure

Regulators

Those bodies responsible for the regulation of the nuclear industry and non-nuclear industry.

Regulatory Impact Assessment ( RIA)

The RIA is a requirement of Government. It is a tool designed for delivering better regulation, and the RIA process is aimed at helping Government departments deliver successful policy. It is an analysis of the likely impacts of a policy change and the range of options for implementing it. It considers: any form of regulation (for example, formal legislation, codes of practice or information campaigns); the full range of potential impacts (economic, social and environmental); and where the impact may fall (business, the public sector, the voluntary sector or other groups). RIA should be carried out for all policy changes, whether European or domestic, which could affect the public or private sectors, charities, the voluntary sector or small businesses.

Repository

A permanent disposal facility for radioactive wastes.

Reprocessing

A physical or chemical separation operation to extract uranium or plutonium for re-use from spent nuclear fuel.

Retrievability

A characteristic of the design of the waste package and/or the disposal facility that facilitates recovery of waste after emplacement.

Reversibility

denotes the possibility of reversing one or a series of steps in repository planning or development at any stage of the programme. This implies the review and, if necessary, re-evaluation of earlier decisions, as well as the means (technical, financial, etc.) to reverse a step. Reversibility denotes the fact that fallback positions are incorporated in the disposal policy and in the actual technical programme. Reversibility may be facilitated, for example, by adopting small steps and frequent reviews in the programme, as well as by incorporating engineering measures. In the early stages of a programme, reversalof a decision regarding site selection or the adoption of a particular design option may be considered. At later stages, during construction and operation, or following emplacement of the waste, reversal may involve the modification of one or more components of the facility, or even the retrieval of waste packages from parts of the facility.

(see Ref 62 above)

Risk

The chance that someone or something that is valued will be adversely affected by a hazard, where a hazard is the potential for harm that might arise, for example, from ionising radiation.

Risk assessment

An assessment of radiological risk.

Risk guidance level

A level of radiological risk from a disposal facility which provides a numerical standard for assessing the environmental safety of the facility after the period of authorisation.

Risk informed

The concept that risk calculations from proposed waste management practices should be part of the process for securing safety and determining best options for managing the waste.

Risk target

A level of radiological risk from a single disposal facility which provides a numerical standard for assessing the long term performance of the facility.

Safety case

A 'safety case' is the written documentation demonstrating that risks associated with a site, a plant, part of a plant or a plant modification are as low a reasonably practicable and that the relevant standards have been met. Safety cases for licensable activities at nuclear sites are required as license conditions under the NIA65.

Scenario

A postulated or assumed set of conditions and/or events.

Sealed source

A source whose structure is such as to prevent, under normal conditions of use, any dispersion of the radioactive substances into the environment.

Seismic survey

A technique for determining the detailed structure of the rocks underlying a particular area by passing acoustic shock waves into the rock strata and detecting and measuring the reflected signals.

Sellafield

NDA owned nuclear licensed site in Cumbria comprising nuclear fuel storage, reprocessing and manufacturing facilities.

Separated plutonium

Plutonium that has been separated from spent nuclear fuel by reprocessing.

Short-lived nuclides

Radioactive nuclides with a half-life of less than 30 years. Thus, radioactive waste described as short-lived would reduce in activity by a factor of 1000 within 300 years.

Short-lived waste

Radioactive waste that contains radionuclides that have half lives of 30 years or less, for which there is negligible heat output and the alpha emitting radionuclides are present at concentrations below 400 Bq/g and it is free of beta emitting radionuclides of half lives above 30 years.

Sievert

The S.I. unit of radiation dose; one millisievert (mSv) is a thousandth of a sievert and one microsievert (_Sv) is one millionth of a sievert.

Site

For a disposal facility, the piece of land where the facility is, or is intended to be, located. More generally, the piece of land where one or a number of sources of radioactivity are, or are intended to be, located.

Site characterisation

Surface and sub-surface investigations to determine the suitability of a site for a disposal facility for solid radioactive waste and to gather information about the site to support an environmental safety case.

Site constraint

The site-related dose constraint applies to the aggregate exposure resulting from discharges from a number of sources with contiguous boundaries at a single location. It includes the radiological impact of current discharges from the entire site, but excludes the impact of direct radiation and historical discharges. The site constraint of 0.5 mSv/year applies irrespective of whether different sources on the site are owned and operated by the same or by different organisations.

Special precautions burial

See controlled burial

Specific activity

Of a radionuclide, the activity per unit mass of that nuclide; of a material, the activity per unit mass or volume of the material in which the radionuclides are essentially uniformly distributed.

Spent fuel (Spent nuclear fuel)

Used fuel assemblies removed from a nuclear power plant reactor.

Staged authorisation

A regulatory process in which a developer of a disposal facility for solid radioactive waste must not proceed beyond predefined hold points without approval of the relevant environment agency.

Stakeholders

In the context of this document, people or organisations, having a particular knowledge of, interest in, or be affected by, radioactive waste, examples being the waste producers and owners, waste regulators, non-Governmental organisations and local communities and authorities.

Step-wise process

A process in which the regulator would agree with the developer a number of decision points (or steps) during development of a disposal facility for solid radioactive waste, beyond which an activity may not proceed without agreement from the regulator .

Storage

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

Strategic Environmental Assessment ( SEA)

SEA refers to the type of environmental assessment legally required by the Environmental Assessment (Scotland) Act 2005 in the preparation of certain plans, programmes and strategies. The authority responsible for the plan, programme or strategy must prepare an environmental report on its likely significant effects, consult the public on the report and the plan or programme proposals, take the findings into account, and provide information on the plan or programme as finally adopted.

Structural integrity

The ability of an engineered structure to function safely and reliability throughout its life.

Substitutions

The contractual arrangements by which wastes resulting from reprocessing carried out in the UK for overseas customers can be retained and other wastes - equivalent in radiological terms - can be returned. If implemented, substitution would mean that the UK would retain some overseas-owned ILW and LLW and return an additional amount of HLW together with the overseas-owned HLW due, in any case, to be returned.

Sustainable development

A principle underpinning planning. It is the idea of ensuring a better quality of life for everyone, now and for future generations. A widely used definition was drawn up by the World Commission on Environment and Development in 1987: "development that meets the needs of the present without compromising the ability of future generations to meet their own needs".

Thermal stability

The ability of a material to withstand damage caused by heat or changes in temperature.

Thorium

A naturally occurring, weakly radioactive element and an alternative to uranium as a nuclear fuel.

Transmutation

The conversion of one element into another. Transmutation is under study as a means of converting longer-lived radionuclides into shorter-lived or more manageable radionuclides.

Tritium

A radioactive isotope of hydrogen with a mass about three times that of ordinary hydrogen

UK Radioactive Waste Inventory

A compilation of data on UK radioactive waste holdings, produced about every three years. The latest version, for a holding date of 1 April 2007, was published in June 2008. It was produced by Defra and the NDA. It is the latest public record of information on the sources, quantities and properties of Low Level Waste ( LLW), Intermediate Level Waste ( ILW) and High Level Waste ( HLW) in the UK. It comprises of a number of reports and additional detailed information on the quantities and properties of radioactive wastes in the UK that existed at 1 April 2007 and those that were projected to arise after that date.

Unconditioned waste

Radioactive waste in its initially generated state, prior to its preparation and packaging for longer term storage and/or disposal in a solid and stable form.

Uranium

A radioactive element commercially extracted from uranium ores. By nuclear fission (the nucleus splitting into two or more nuclei and releasing energy) it is used as a fuel in nuclear reactors to generate heat.

Very Low Level Waste ( VLLW)

Covers wastes with very low concentrations of radioactivity. It arises from a variety of sources, including hospitals and the wider non-nuclear industry. Because VLLW contains little total radioactivity, it has been safely treated as it has arisen by various means, such as disposal with domestic refuse directly at landfill sites or indirectly after incineration.

Vitrification

Process of incorporating materials into molten glass. Vitrification is a technology applied to the solidification of liquid high level waste from the reprocessing of spent fuel.

Waste acceptance criteria

Quantitative and/or qualitative criteria, specified by the operator of a disposal facility and approved by the regulator for radioactive waste to be accepted for disposal.

Waste characterisation

Determination of the physical, chemical and radiological properties of waste.

Waste consignment

Any waste sent by a consignor to a disposal facility.

Waste form

Waste in its physical and chemical form after treatment. The waste form is a component of the waste package.

Waste hierarchy

A hierarchical approach to minimise the amounts of waste requiring disposal. The hierarchy consists of non-creation where practicable; minimisation of arisings where the creation of waste is unavoidable; recycling and reuse; and, only then, disposal.

Waste manager

Any organisation that currently has responsibility for the safe and environmentally responsible disposition of specific radioactive wastes in accordance with regulatory requirements, and the funding thereof. The organisation may or may not equate to the waste producer, who generated the waste in the first instance, as the responsibilities listed above may have passed to another organisation in the interim.

Waste package

The Waste form and any container(s) and internal barriers (e.g. absorbing materials and liner), prepared in accordance with requirements for handling, transport, storage and disposal.

Waste producer

The organisation that produced radioactive waste in the first instance. The waste producer may or may not equate to the current waste manager, as responsibility for the waste may have been passed to another organisation in the interim.

Waste stream

This is a convenient way of grouping types of wastes together which have similar physical, chemical or radionuclide properties. This process is comparable to how domestic waste can be divided into separate groups, such as paper to be recycled or garden waste to be composted. For radioactive materials this gives us a range of broad groupings which then allows for a collective method of treatment, packaging and disposal appropriate to a waste stream's specific properties. The decommissioning of a large nuclear reactor would be likely to result in the creation of a number of waste streams, e.g. graphite from the core, activated steel.