Glossary
Gamma Radiation Highly penetrating, short wavelength radiation emitted from the nuclei of atoms. It is stopped by an adequate thickness of lead, concrete or other materials.
Geiger CounterAn instrument for detecting and measuring ionizing radiation. It contains a gas-filled tube which discharges electrically when ionizing radiation passes through it.
Half-lifeThe time over which the atoms of a particular radioactive nuclide decay to half their original intensity of emitted radiation. The half-life is a characteristic property of each radioactive isotope.
Heavy WaterHeavy water or deuterium oxide (D20) is a natural form of water used to lower the energy of neutrons in a reactor. It is heavier than normal water by about 10%, and occurs in minute quantities (about one part heavy water per 7,000 parts water). CANDU reactors use heavy water as both moderator and coolant. Heavy water is one of the most efficient moderators, and enables the CANDU design to use natural uranium fuel.
IAEAThe International Atomic Energy Agency is an agency set up by the United Nations to monitor and promote the peaceful uses of nuclear energy.
IonAn atomic particle, atom or molecule that is electrically charged.
Ionizing RadiationAny type of radiation that can, directly or indirectly, change the electric charges of atoms or molecules. It is produced when radionuclides decay.
IsotopeDifferent forms of atoms of the same element. They have the same number of protons in their nuclei but a different number of neutrons (the same atomic number but different atomic weights). Uranium-238 and uranium-235 are isotopes of uranium. Isotopes may be stable (not spontaneously decaying) or unstable (spontaneously decaying, emitting ionizing radiation).
KilowattKilowatt (KW) is a metric measurement of power, and is equal to 1,000 watts.
Kilowatt-HourThe basic unit of electric energy equal to one kilowatt of power supplied to or taken from an electric circuit steadily for one hour. A kilowatt-hour (KWH) is 1,000 watt-hours.
MACSTORMACSTOR (Modular Air-Cooled STORage) units were developed by AECL as safe, highly-efficient, above-ground modules for storing used fuel from CANDU and other types of reactors.
MegawattMegawatt (MW) is a unit of power, is equal to one million watts, and refers to the heat output of a reactor. MWe refers to electrical output.
ModeratorModerators are used to lower ("moderate") the energies of a portion of the neutrons emitted by fissioning uranium atoms, to increase their probability of hitting another uranium atom to cause further fissioning. Graphite and light water are frequently used as moderators. CANDU reactors use heavy water as the moderator.
NeutrinoAn electrically neutral particle with negligible mass. It is produced in many nuclear reactions such as in beta decay.
NeutronOne of the basic particles which make up an atom. A neutron and a proton have about the same weight, but the neutron has no electrical charge.
NG CANDUNext-generation CANDU
NRUThe 200-megawatt National Research Universal research reactor at Chalk River Laboratories. It started up in 1957 and currently produces about 60% of the world's supply of molybdenum-99, a critical isotope used for medical diagnostic purposes.
NRXThe 42-megawatt National Research Experimental research reactor at Chalk River Laboratories. It operated from 1947 until 1993 and was one of the most powerful research reactors in the world.
Nuclear EnergyNuclear energy is the energy stored in the bonds of the sub-atomic particles in the nucleus of atoms.
Nuclear ReactorA device in which a fission chain reaction can be initiated, maintained, and controlled. Its essential components are fissionable fuel, moderator, shielding, control rods, and coolant.
NucleusThe core of the atom, where most of its mass and all of its positive charge is concentrated. Except for hydrogen, it consists of protons and neutrons.
NuclideAny species of atom that exists for a measurable length of time. A nuclide can be distinguished by its atomic weight, atomic number, and energy state.