| " 10-6"
| Often proposed as the standard design criterion for a nuclear waste repository: the risk of death to an individual in the critical group of one in one million per year (ie 10-6). On the same basis as the criterion was derived the risk from natural background radiation is about one in ten thousand.
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| ACSNI | Advisory Committee on the Safety of Nuclear Installations (renamed NuSAC in July 1997).
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| AECL | Atomic Energy of Canada Limited.
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| AGR | Advanced Gas cooled Reactor.
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| Anaerobic | In the absence of free oxygen.
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| Becquerel | The standard unit of radioactivity , equal to one nuclear disintegration per second. A becquerel (Bq) is a very small unit and when discussing radioactive waste the term terabecquerel is often more appropriate: one terabecquerel (TBq) = 1012 Bq; ie a million million disintegrations per second.
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| BGS | British Geological Survey.
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| BNFL | British Nuclear Fuels plc (previously British Nuclear Fuels Ltd).
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| CANDU | Canadian Deuterium Uranium water-cooled reactor type. The fuel consists of un-enriched ceramic uranium oxide pellets within zirconium alloy tubes.
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| Cmnd | Government command paper.
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| COLA | Consortium of Opposing Local Authorities.
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| Committed waste | Waste which cannot be avoided. It will be created even if the entire nuclear industry were to cease operation immediately: the waste either already exists or will result from the decommissioning of existing installations.
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| CORE | Cumbrians Opposed to a Radioactive Environment.
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| Critical group | The group of people who, on basis of age, living habits and place of residence, receive the highest radiation dose. (This may be an existing or hypothetical group.)
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| Decommissioning | The term decommissioning is used in a generic sense to cover all of the procedures undertaken once a nuclear installation has ceased operating. Decommissioning therefore covers processes such as defuelling reactors, cleaning and making safe an installation (which could include a long period of safe storage on site), dismantling, removal work and waste conditioning prior to storage or disposal.
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| Depleted uranium | Uranium consisting predominantly of non-fissile uranium.
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| DETR | Department of the Environment Transport and Regions.
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| DTI | Department of Trade and Industry.
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| EURATOM | European Atomic Energy Community.
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| Fissile | Refers to a radionuclide which can break into two large fragments accompanied by the release of free neutrons and large amounts of energy. A few man-made radionuclides are so unstable that they fission spontaneously; others can do so if the nucleus captures a neutron.
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| Fission products | The atomic fragments resulting from nuclear fission. For instance, the two large atomic fragments produced by the fission of uranium-235 might be isotopes of tin and molybdenum, which themselves are likely to be highly radioactive.
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| GRA | Guidance on Requirements for Authorisation (for disposal facilities on land for LLW and ILW). A document outlining safety standards for disposal.
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| Half life | The time required for half of the atoms in a sample to decay or transform. For example: the radionuclide krypton-85 has a half-life of 3,934.4 days and decays to the stable isotope rubidium-85 by emitting a beta particle; after one period of 3,934.4 days, 50 per cent of the initial krypton-85 atoms in a sample will have become rubidium-85; after ten half lives (107 years, 9½ months) the sample will contain just 0.1 per cent krypton-85, and 99.9 per cent rubidium-85.
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| HLW | High Level radioactive Waste. Highly active heat generating waste that normally continues to generate heat for several centuries. A high level of shielding and heat dissipation is required during handling, transportation, and storage (and disposal). Its thermal power is above 2 kW per m3. It may take many thousands, or millions, of years for the radioactivity of HLW to decay to background levels.
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| HSE | Health and Safety Executive.
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| IAEA | International Atomic Energy Agency.
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| ILW | Intermediate Level radioactive Waste. Waste in which radioactivity levels exceed the upper boundaries for LLW. Some of it requires shielding. Heat generation usually less than 2kW per m3 but may require provision for heat dissipation during storage (or disposal).
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| Intergenerational equity | The concept that future generations should not have to bear the costs and consequences of actions which were of benefit mainly to present and previous generations.
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| LLW | Low Level radioactive Waste. Radioactive materials other than those suitable for disposal with ordinary refuse, but containing less than 4 x109 Bq per tonne of alpha activity or less than 12 x 109 Bq per tonne of beta/gamma activity. Does not require shielding during normal handling and transportation.
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| Magnox | Reactor type using uranium metal fuel rods enclosed in a cladding of magnesium alloy.
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| MoD | Ministry of Defence. |
| MOX | Mixed Oxide Fuel (a mixture of plutonium oxide and uranium oxides).
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| MTR | Materials Testing Reactor.
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| NCNI | National Campaign for the Nuclear Industry.
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| NEA | OECD Nuclear Energy Agency.
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| NERC | Natural Environment Research Council.
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| NGO | Non Governmental Organisation.
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| NII | Nuclear Installations Inspectorate (part of the HSE).
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| NIMBY | Not In My Back Yard. Referring to objections to activities nearby, e.g. planned nuclear installations, or motorways.
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| Nirex | United Kingdom Nuclear Industry Radioactive Waste Management Executive.
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| NRPB | National Radiological Protection Board.
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| NSC | National Steering Council for Nuclear Free Local Authorities.
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| NuSAC | Nuclear Safety Advisory Committee (originally ACSNI).
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| OECD | Organisation for Economic Co-operation and Development.
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| Palaeoclimatic | Concerned with the climate in the geological past.
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| Partitioning | Specifically the separation of certain radionuclides from other wastes so that they may be subjected to transmutation.
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| Probabilistic assessment | In the case of a repository, a safety assessment that takes into account the probabilities and consequences of events and processes that could lead to radionuclide releases, or influence release rates, and also takes account of uncertainties in estimating probabilities and consequences.
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| POST | Parliamentary Office of Science and Technology.
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| PWR | Pressurised Water Reactor.
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| R&D | Research and Development.
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| Radionuclide | Any nuclide (isotope of an element) which exhibits radioactivity (ie can undergo spontaneous disintegration, releasing an alpha-particle, a beta-particle or a gamma-ray).
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| RCEP | Royal Commission on Environmental Pollution.
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| RCF | Rock Characterisation Facility (specifically the one planned in Cumbria).
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| RWMAC | Radioactive Waste Management Advisory Committee.
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| RWPG | Radioactive Waste Policy Group (in the DETR).
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| SAP | Safety Assessment Principles (for nuclear plants).
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| SEPA | Scottish Environment Protection Agency.
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| Sievert | A measure of radiation dose which takes into account the type of radiation involved, the energy deposited in the tissues irradiated, and the sensitivity of the different body tissues to radiation. Typically, doses are expressed in terms of micro sieverts (µSv). 1 sievert = 1 million µSv. A dose of around 6.5 Sv, delivered over a few minutes or hours, will lead to death from acute radiation sickness within a few weeks. The annual average dose to an individual in the United Kingdom is 2,200 µSv from natural radiation and 400 µSv from man-made radiation, (of which 370 µSv is from medical uses of radiation and radioactive materials).
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| SKB | Svensk Kärnbränslehantering AB (Swedish nuclear fuel and waste management company).
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| Subduction zone | Area of the Earth's surface where one tectonic plate is over-ridden by another: typically an oceanic plate will subduct beneath a continental plate. It has been suggested that depositing nuclear waste in or on a plate that is being subducted will lead to it being transported into the mantle and thus out of the biosphere.
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| Terabecquerel | 1012 Becquerels.
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| THORP | Thermal Oxide Reprocessing Plant (at Sellafield). Oxide fuel is used in AGRs, PWRs and other light water reactors.
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| Transmutation | Process by which radionuclides are bombarded with neutrons (either in a reactor or a particle accelerator) and are converted into shorter-lived or stable nuclides.
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| UKAEA | United Kingdom Atomic Energy Authority, now known only by its acronym.
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| URL | Underground Research Laboratory.
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| Vitrification | The process by which radioactive waste (typically HLW) is immobilised in borosilicate glass.
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| VLLW | Very Low Level radioactive Waste. Formally defined as material in which each 0.1 m3 contains less than 4 x 105 Bq of beta/gamma activity or single items which contain less than 4 x 104 Bq of beta/gamma activity. This waste can be disposed of at landfill sites without special treatment.
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| WIPP | Waste Isolation Pilot Plant. An underground waste repository built in salt deposits in New Mexico US for military nuclear waste.
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