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Absorbing rods – movable elements of CPS (see CPS) made of neutron-absorbing material that affects reactivity and is used to control power of nuclear reactor (see also control rods).
B
Becquerel (Bq) – the SI unit of radioactive isotopes activity named after A. Becquerel, a French physicist; 1 Bq equals one transformation per second.
BN (FNR) – a fast neutron reactor where sodium is used as primary and secondary coolant while water and steam are used as tertiary coolants. In Russia it is operated at Beloyarsk NPP.
Breeder (or Breeder-reactor) – a fast neutron reactor where nuclear fuel breeding, i.e. fuel production, takes place (see Breeder).
Burnable absorber – materials introduced in the critical system that actively absorb neutrons, compensate for excessive critical mass of the fissile material at the initial phase of the system operation and is burn out with time.
Burnup fraction – a fraction of an initial number of nuclei of a given type that went through nuclear transmutation in a reactor due to an impact of neutrons (MWt x day/kgU).
Burnup of nuclear fuel – reduction of concentration of any nuclide in nuclear fuel resulted from nuclear transmutations of this nuclide during the reactor operation.
BWR (Boiling Water Reactor) – tank-type boiling water reactor where water is used as the coolant.
C
Ceramic fuel – nuclear fuel that consists of refractory compounds, for example, oxides, carbides, nitrides.
Chain nuclear reaction – a sequence of heavy atom nuclei fission reaction when they react with neutrons or other elementary particles resulting in generation of more light nuclei, new neutrons or other elementary particles and nuclear power release. The reaction is called damping, self-sustained or divergent depending on the average number of reactions.
Channel reactor – a nuclear reactor which core contains the fuel with circulating coolant in separate leaktight fuel channels capable of withstanding high pressure of the coolant.
Closed nuclear fuel cycle – a nuclear fuel cycle where spent nuclear fuel removed from the reactor is reprocessed to recover uranium and plutonium for refabrication of nuclear fuel.
Control (absorbing) rods – rods made of the material absorbing neutrons which can be used to moderate or stop a chain reaction in a reactor; a constituent of CPS (see CPS).
Conversion – a chemical process to transform U3O8 into UF6 preparatory to enrichment.
Cooling pond – a storage facility with water located on a reactor site of a nuclear power plant for temporary storage of spent nuclear fuel.
Core – the main part of a nuclear reactor where controlled chain reaction occurs. This is the reactor section the nuclear fuel is loaded to.
CPS – reactor control and protection system.
D
Depleted uranium – uranium where U-235 isotope content is less than in natural uranium (less than 0.7%) which is also an enrichment by-product of the fuel cycle; it can be blended with highly enriched uranium to fabricate nuclear fuel.
Dry conversion – a method to fabricate uranium dioxide powder.
Dry storage facility – a storage facility for nuclear fuel (usually, spent nuclear fuel) without the use of water.
E
EGP - graphite channel power reactor with steam overheat; operated at Bilibino NPP.
Enriched nuclear fuel – nuclear fuel containing more fissile nuclides than the source natural material.
Enriched uranium - uranium where U-235 to U-238 ratio has been increased above the natural 0.7%. Normally, reactor-grade uranium is enriched to about 3.5% U-235 while weapons-grade uranium contains more than 90% U-235.
Enrichment of uranium (uranium ore) – a set of processes related to treatment of the uranium-containing minerals to separate the uranium from the other minerals of the ore and to increase the U-235 to U-238 ratio. The enrichment process includes ore grinding and milling as well as various chemical processes to separate the uranium from waste called tails. Enrichment by in-situ leaching includes chemical processes to separate uranium from the solution.
Environmental safety – environmental protection level against adverse impacts of nuclear facilities; features of such facilities are to avoid damage to the environment.
Experimental reactor – see Research reactor.
F
FA (abbr. “fuel assembly”) – nuclear fuel arrangement consisting of a bundle of fuel rods, CPS channels (see CPS), spacing grids, tailpiece and cap (and, in some cases, – a shroud tube).
FAG – a fuel rod made as a leaktight tube where fuel pellets made of uranium dioxide admixed with gadolinium oxide are emplaced.
“FA-Square” - a fuel assembly of western design which has a square in section.
First criticality – a NPP commissioning stage that includes reactor fuelling, reaching of criticality and implementation of necessary physical experiments at the power level.
FNF (abbr. “fresh nuclear fuel”) – new (unirradiated) nuclear fuel.
FR (abbr. “fuel rod”) – a fuel element made as a leaktight tube where fuel pellets made of uranium dioxide are emplaced.
Fuel campaign – a period of time within which the fuel stays a reactor which operates at nominal power without refuelling.
Fuel fabrication – nuclear fuel fabrication, typically, as ceramic pellets enclosed into metal tubes which are subsequently assembled into fuel assemblies.
Fuel pellet – a pellet made of compressed uranium dioxide. It is the basis of nuclear fuel and placed inside FR (see FR).
G
Gaseous diffusion separation technology – an isotope separation process based on different diffusion speeds of gases of different molecular mass through a microporous wall; used for uranium enrichment.
H
Highly enriched uranium – uranium containing isotope uranium-235 equal to or more than 20% by mass.
Hydrometallurgical processing of uranium ore – extraction of uranium or its compounds from the natural ore using water solutions of chemical reagents followed by selective uranium extraction from these solutions. It is a basic method of chemical enrichment of uranium ore and production of uranium concentrate which changes the minerals’ composition.
I
IAEA (International Atomic Energy Agency) - the world´s center of cooperation in the nuclear field. It was set up in 1957 within the United Nations family. The Agency works with its Member States and multiple partners worldwide to promote safe, secure and peaceful nuclear technologies.
INES (International Nuclear Event Scale) – the scale, introduced to rate significance of nuclear events. It includes 8 levels (zero level plus seven hazard levels).
ITER (International Thermonuclear Experimental Reactor) – the reactor which is being constructed on the basis of the tokamak by the international group of scientists under the auspices of the IAEA. It is planned to be a prototype of the world’s first thermonuclear power plant so-called DEMO.
L
Low enriched uranium – enriched uranium a lesser mass percentage of isotope U-235 than 20%.
M
Marine propulsion reactor – a nuclear reactor generating power for a vessel to move.
Megawatt (MW) – a unit of power equal to 106 watts. MW(e) relates to electrical power of the generator, MW(t) means thermal power of the reactor or heat source (for example, total power of the reactor itself is, usually, by three times more than electrical power).
Mining method – a traditional underground method for extraction of different ores, including uranium ore.
MOX-fuel (Mixed Oxide Fuel) – the mixed (usually, on the basis of uranium and plutonium) oxide nuclear fuel.
MPC – mining and processing combine.
N
Natural uranium – naturally occurring uranium with an isotopic composition of about 0.7% U-235. It can be used as a fuel in heavy water-moderated reactors.
NFC – nuclear fuel cycle. A set of activities aimed at providing the functioning of nuclear power. It includes extraction and processing of uranium ore, fuel fabrication and its transportation to NPP site, SNF storage and reprocessing. NFC is called open if the SNF disposal is envisaged; if the fuel reprocessing and reuse is planned for, it is called the closed one.
Nozzle – an element (part) of the fuel assembly.
NPI – nuclear power installation. NPP – nuclear power plant, an industrial facility for electricity generation.
Nuclear breeding – nuclear fuel reproduction with a conversion ratio higher than 1, i.e. when fissile material is produced more than used in the reactor.
Nuclear fuel – a fissile material which has undergone necessary fabrication processes and been formed in such a way as to be loaded into a reactor.
Nuclear legislation – a set of laws and legal acts establishing public relations in the use of atomic energy.
Nuclear material – any special source radioactive material (plutonium-239, uranium-233, uranium enriched in isotope U-235 etc.).
Nuclear power – a branch of the power engineering which uses atomic energy for electricity and heat generation.
Nuclear-powered vessel – a common name for vessels with a nuclear power installation.
O
Open mining – traditional ore mining method.
Open nuclear fuel cycle – nuclear fuel cycle where the spent nuclear fuel unloaded from the reactor is not reprocessed and considered radioactive waste.
P
Plutonium – a nuclear material with atomic mass of 239 and half-life of 24.4 thousand years which is produced artificially by neutron irradiation of uranium-238.
Power reactor – a nuclear reactor designed for electricity generation.
Power unit – one of the NPP reactors with necessary additional equipment.
Propulsion reactor – a nuclear power reactor used as a power source for conveyance (vessel) movement.
PWR (abbr. Pressurized Water Reactor) - a western design pressurized water reactor similar to VVER reactors.
R
Rad - the off-system unit for absorbed radiation dose; 1 rad = 0.01 grays.
Radiation safety – a system of measures providing for the protection of nuclear facility personnel and population against radiation consequences.
RBMK reactor – high-power channel-type reactor. It is single-circuit water-cooled graphite-moderated power reactor.
Recovered uranium – uranium extracted from SNF by radiochemical treatment for the reuse in nuclear reactor (regenerated/return fuel).
Refuelling – operations carried out with refuelling machines to replace the spent fuel; the fuel irradiation level at which the refuelling is carried out depends on the fuel composition after irradiation, permissible operation period and reactivity change.
Rem (roentgen equivalent man) – an off-system unit of dose equivalent, equal to 0.01 Sv.
Research reactor – a nuclear reactor used for basic and applied research and generation of radioactive isotopes (see also Experimental reactor).
S
Secondary nuclear fuel – this includes plutonium-239 and uranium-233 generated in nuclear reactors from uranium-238 and thorium-232 when absorbing neutrons.
Sievert (Sv) - the SI unit of equivalent dose and effective dose; named after G.R. Siewert, a Swedish scientist.
SNF (abbr. “spent nuclear fuel”) – fuel (fuel assemblies) which has lost its properties after stayed in the reactor and should be removed from it for subsequent reprocessing or disposal.
Spacing grid – a fuel assembly component.
Source material – a material containing uranium or thorium with such isotopic ratio as occurring in natural uranium or thorium; uranium depleted by isotope uranium-235; any of the above mentioned substances in any physical or chemical form.
T
Tails – waste generated during the uranium extraction from the ore in the process of its enrichment.
Transport container – a container used for safe transportation of the spent fuel and high-level nuclear waste.
U
Underground (heap) leaching – a minerals (including uranium) mining method by recovering the minerals from porous orebodies by chemical leaching without physical excavation.
Uranium (U) – chemical radioactive element (metal) with atomic number of 92.
Uranium-233 – artificial uranium isotope with the half-life of 1.6x105 years resulted from transmutation of thorium-232 after neutron capture; it is attributed to fissile nuclides.
Uranium-235 - natural uranium isotope with atomic mass of 235 and half-life of 7.1x108 years; it is the only naturally occurring fissile material.
Uranium-238 - natural uranium isotope with atomic mass of 238 and half-life of 4.5x109 years; it can be used as a breeder material for plutonium-239 generation.
Uranium carbides – uranium and carbon compounds. They are electricity conductive, have high strength, thermal and chemical stability. Uranium carbides enriched in uranium–235 are used as nuclear fuel.
Uranium concentrate – a product generated during hydrometallurgical reprocessing of uranium ore and containing up to 70-90 % of uranium mass as a mixture of oxides with the generic chemical formula U3O8.
Uranium dioxide – a chemical compound, the basic element of nuclear fuel. Uranium dioxide powder is used for fuel pellet fabrication.
Uranium hexafluoride – a chemical uranium compound which under certain conditions can be in gaseous state. It is used as a feed material for fabrication of enriched uranium fuel.
Uranium ore – ore which uranium assay is above the cut-off grade.
Uranium oxide (U3O8) – a non-stoichiometric compound which has several modifications depending on preparation conditions and is generated during oxidation of uranium dioxide in the air and air calcination of any uranium oxide, uranium hydroxide or nitrate and volatile base or acid.
Uranium oxide fuel – nuclear fuel consisting of pellets made of uranium dioxide with 2-4% enrichment by U-235 which are sintered under high pressure and temperature; used for light water reactors.
V
VVER reactor – water-water power reactor where water is used both as the coolant and moderator of neutrons. It is the most widely-used type of reactors at Russian NPPs. There are two modifications of this reactor type: VVER-440 and VVER-1000.
W
Wet storage facility – a nuclear fuel storage facility (typically, spent fuel) where water is used.
Z
Zircaloy - zirconium-stannum alloy; a structural material used in the nuclear technology for fuel claddings.
Zirconium – a chemical element (metal) with low absorbing capacity for thermal neutrons. It is used in nuclear machine engineering.
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