Radioactivity - Law Dictionary Search Results
Home Dictionary Name: radioactivityradioactivity
a form of instability which is a property of the atomic nuclei of certain isotopes which causes a spontaneous change in the structure of the nucleus accompanied by emission of energetic radiation The radiation emitted is usually sufficient to cause ionization in matter through which it passes and is therefore called ionizing radiation The radiation emitted by most radioactive substances is one of three types alpha rays beta rays or gamma rays Some chemical elements have no stable isotopes and these are referred to as radioactive elements and the element itself is said to possess radioactivity...
Fissile material and radioactive material
Fissile material and radioactive material, shall have same meaning assigned to these expressions in the Atomic. Energy Act, 1962 (33 of 1962). [Weapons of Mass Destruction and Their Delivery Systems (Prohibition of Unlawful Activities) Act, 2005 (21 of 2005), s. 4(e)]...
Half life
the time it takes for one half of a substance decaying in a first order reaction to be destroyed For radioactive substances it is the time required for one half of the initial amount of the radioactive isotope to decay The half lifeis a measure of the rate of the reaction being observed For processes that are true first order processes such as radioactive decay the half life is independent of the quantity of material present and it is thus a constant The time it takes for one half the remaining quantity of a radioactive isotope to decay will be the same regardless of how far the decay process has advanced Some chemical reactions are also first order and may be characterized as having a half life However for chemical reactions the half life will depend upon temperature and in some cases other environmental conditions whereas for radioactive isotopes the rate of decay is largely independent of the environment...
Radon
An intensely radioactive gaseous element produced by the radioactive decay of radium 226 which is the main isotope of radium found in pitchblende Chemically it is an inert noble gas Its atomic symbol is Rn It has an atomic number of 86 The radon isotope produced by decay of radium has an atomic weight of 222017 and this isotope decays by alpha emission with a half life of 382 days Numerous other isotopes have been observed all radioactive and all having half lives shorter than that of radon 222 Radon was discovered by M and Mme Curie of Paris in their studies of the radioactive substances in pitchblende Radon was originally called radium emanation or exradio...
Mesothorium
a radioactive isotope of radium radium 228 with a half life of 58 years Also called mesothorium 1 or mesothorium I to distinguish it from a subsequent decay product mesothorium II actinium 228 It was discovered in 1907 by Otto Hahn as a decay product of thorium produced by decay of thorium 232 Mesothorium 1 radium 228 in turn produces actinium 228 mesothorium 2 as the first product of its radioactive decay and the actinium 228 in turn decays quickly half life of 6 hours to thorium 228 which is also called radiothorium the thorium 228 has a half life of 191 years shorter than that of the radium 228 It was discovered and named before full recognition of the nature of isotopes of the elements and was distinguished from other variants of radium by its half life and mode of production and decay It was also cheaper to prepare than other short lived radium isotopes and was thus sold commercially for use eg in making watch dials readable in the dark by painting the hands and hour marks with a ...
Gamma ray
A very penetrating electromagnetic ray not appreciably deflected by a magnetic or electric field emitted by radioactive substances Gamma rays are photons of electromagnetic radiation having a wavelength shorter than that of X rays i e shorter than 01 nanometer and are correspondingly more penetrating than X rays In addition to being given off in certain types of radioactive decay they may be found in cosmic radiation though they are largely absorbed by the earths atmosphere Gamma ray detectors orbited above the atmosphere have found bursts of gamma radiation in some cases associated with visually observed supernova explosions but in most cases from unidentified sources...
radiothorium
an earlier name for the thorium isotope thorium 228 given by its discoverer Otto Hahn It is a radioactive substance formed as one of series of products in the chain of radioactive decay of thorium Its immediate predecessor in the chain is Actinium 228 and it decays by alpha emission to radium 224 with a half life of 191 years The name radiothorium was given prior to the full understanding of the nature of isotopes of elements...
radon
radon a radioactive gas found in some homes that, if occurring in strong enough concentrations, can cause health problems. Source: U.S. Department of Housing and Urban Development ...
berkelium
a chemical element of the transuranic series Chemical symbol Bk atomic number 97 atomic weight 247 It is a radioactive element with no stable isotopes the longest lived isotope is of mass number 24707 decaying by alpha emission with a half life of 1400 years The isotope with atomic weight 249 has a half life of 314 days and was isolated in weighable quantities...
Beta rays
a form of ionizing radiation emitted by radioactive substances such as radium more penetrating than alpha rays and consisting of negatively charged electrons The electrons are the same kind of particle as those of cathode rays but have much higher velocities about 35000 to 180000 miles per second They are readily deflected by a magnetic or electric field...
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