Glossary
A B C D E F G H I J K M N O P R S T U V W Y
Activation product: A radioactive nuclide created by neutron radiation in the reactor.
Activity: The number of spontaneous nuclear disintegrations in radioactive matter within a certain time. The unit of radioactivity, the becquerel (Bq), equates to one disintegration per second.
ALARA (As Low As Reasonably Achievable): An internationally used principle regulating the amount of radiation doses at nuclear power plants.
Alpha-active element: A radioactive element that emits an alpha particle upon decomposing. An alpha particle consists of two protons and two neutrons.
Background radiation: Radiation emanating from natural sources, such as radon from the soil, radiation from space and radioactive materials in one's own body.
Becquerel (Bq): The unit expressing the activity of a radioactive substance. 1 Bq is equal to one spontaneous nuclear disintegration in the substance per second.
Beta-emitting substance: Radioactive material that emits negatively charged particles (electrons).
BOD7ATU: The biological oxygen demand in wastewater.
BWR, Boiling water reactor: A light-water reactor in which water used as the coolant boils as it passes through the reactor core. The steam generated rotates the turbines.
Capacity factor: The fi gure depicting the production at a power plant e.g. for one year. The capacity factor is the energy produced in a year by a power plant as a percentage of the energy it would have produced had it been operating at full capacity for the entire year.
Carbon-14: Carbon-14 is a long-lived, naturally occurring, beta-emitting radioisotope created by cosmic rays in the earth's atmosphere. It is also formed in a nuclear reactor when the oxygen in the coolant is activated. Carbon-14 then enters the atmosphere bound to carbon dioxide.
Control rod: A rod holding material that absorbs neutrons. It regulates the number of neutrons in the reactor core and thus the power of the reactor. A power plant reactor has a large number of control rods.
Decibel, dB: Noise is measured by a decibel scale expressing sound intensity.
Dose rate: A dose of radiation per time unit (for example, mSv/h) expressing the amount of radiation a person is exposed to within a certain period of time.
DNV: DNV Certification Oy/Ab is an accredited verifi er of TVO's environmental operations.
EIA, Environmental Impact Assessment: An assessment of environmental impacts that is required for all major ventures that are likely to have an effect on the environment.
EMAS: Eco-Management and Audit Scheme.
Euratom: A unit of the EU Commission that supervises nuclear material.
Fission products: The medium-heavy nuclei produced in nuclear fission. They are usually radioactive.
Fuel element: An element formed by fuel rods.
Fuel element rod: A slender metal tube holding fuel tablets. The fuel inside the tube is generally uranium oxide crushed into tablets.
Gamma radiation: Electromagnetic radiation emitted during alpha and beta decay.
Gigawatt, GW: A unit of power. One gigawatt is a million kilowatts.
GRI (Global Reporting Initiative): Reporting guidelines for social responsibility that were approved by a meeting of the UN in Johannesburg in 2002. The reporting covers a company¿s financial, human and environmental responsibility.
Half-life time: The time it takes for the activity of a radioactive isotope to be reduced to half the original.
IAEA: International Atomic Energy Agency.
INES (International Nuclear Event Scale): A seven-level scale used internationally to depict the seriousness of accidents and incidents at nuclear power plants. The lower levels (1-3) depict incidents that have weakened plant safety and the upper levels (4-7) accidents that could cause emissions into the environment that require protective measures against radiation.
Iodine: From the point of view of radiation safety, the most important isotope of iodine among fi ssion products is iodine-131, which has a half-life of eight days.
Ion-exchange resins: Substances used to remove impurities from water.
ISO 9001 standard: International standard for quality management systems.
ISO 14001 standard: A standard for the management of environmental matters that is widely used in various parts of the world.
Isotope: Atoms of the same element differing from each other in the number of neutrons in their nucleus. Almost all natural elements occur as more than one isotope.
KPA: Interim storage for spent fuel.
ManSievert, manSv: The unit used to indicate the collective radiation dose received by a certain number of people.
MTT: MTT Agrifood Research Finland.
Megawatt, MW: A unit of power. One megawatt equals 1,000 kilowatts, or one million watts.
Noble gas: The name for certain gases rarely found in the atmosphere. The noble gases are helium (He), neon (Ne) argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn).
Nuclide: A type of atom or nucleus with a specifi c number of protons and neutrons.
Occupational accident: An accident which occurs at work or on the way home from work or vice versa and which causes an absence of at least one day.
PWR, Pressurized water reactor: A light-water reactor with such a high reactor pressure that water used as the coolant does not boil in the reactor. The hot water is conducted from the reactor to a steam generator in which the water in the secondary circuit evaporates and the steam is led to rotate the turbine.
Radiation: Electromagnetic waves or particle radiation consisting of the smallest particles of matter.
Radioactive operating waste: Waste such as plastic, paper and cloth generated during maintenance work at the power plant. The volume can be reduced by baling.
SAHARA (Safety As High As Reasonably Achievable): An internationally used principle emphasizing safety at a nuclear power plant.
Sievert (Sv): A radiation dose unit indicating the biological effects of radiation. As it is a very large unit, millisieverts (1 mSv = 0.001 Sv) and microsieverts (1 µSv = 0.001 mSv) are more commonly used.
STUK: Finnish Radiation and Nuclear Safety Authority. STUK is the authority that regulates the Finnish nuclear energy sector.
Tritium: Tritium is a hydrogen isotope with a nucleus consisting of one proton and two neutrons. The nucleus is called tritium.
TW, terawatt: A unit of power. One terawatt equals one billion kilowatts.
TWh, terawatt-hour: A unit of energy. One terawatt-hour equals one billion kilowatt hours.
Uranium: An element with the chemical symbol U. Uranium comprises 0.0004% of the earth's crust. All uranium isotopes are radioactive. Natural uranium is mostly in the form of isotope U-238, which has a half-life of 4.5 billion years. Only 0.72% of natural uranium is in the form of isotope U-235, which can be used as a nuclear fuel.
VLJ repository: A repository for low and intermediate-level radioactive waste.
VTT: Technical Research Centre of Finland.
WANO: The World Association of Nuclear Operators.