studying the phenomenon of radioactivity, every scientist refers to this as the most important characteristic of its half-life.As is known, the law of radioactive decay states that every second in the world there is a disintegration of atoms, and the quantitative characteristic of these processes is directly related with the number of atoms.If for a certain period of time decay occurs half of all of the available number of atoms, the decay of the remaining ½ of the atoms would require the same amount of time.It is this time interval is called the half-life.Different elements it is different - from thousandths of milliseconds to billions of years, as, for example, when it is about a half-life of uranium.
Uranium is the heaviest of all existing elements in the natural state in the world, it is generally the most beautiful object for the study of radioactivity.This element was discovered in 1789 by German scientist M. Klaproth, who named it in honor of the recently discovered planet Uranus.The fact that uranium is radioactive, it was accidentally found at the end of the XIX century French chemist Becquerel.
The half-life of uranium is calculated using the same formula as the similar periods of other radioactive elements:
T_ {1/2} = au ln 2 = frac {ln 2} {lambda},
where «au» -the average lifetime of an atom, «lambda» - the main decay constant.Since ln 2 is about 0.7, the half-life of only 30% on average shorter than the total lifetime atom.
Despite the fact that to date, scientists have known 14 of uranium isotopes, they are found in nature only three: uranium-234, uranium-235 and uranium-238.The half-life of uranium is different: the case for U-234 he is "only" 270 thousand years, and a half-life of uranium-238 exceeds 4.5 billion.The half-life of uranium-235 is in the "middle ground" - 710 million years.
It is worth noting that the radioactivity of uranium in vivo is high enough to, for example, to light a photographic plate in just one hour.At the same time it should be noted that in all of the uranium isotope U-235 is only suitable for producing fillings for a nuclear bomb.The fact is that the half-life of uranium-235 in a commercial environment is less intense than his "brothers", and therefore the output of unnecessary neutrons are minimal.
The half-life of uranium-238 is significantly more than 4 billion years old, but he is now widely used in the nuclear industry.So as to start a chain reaction of fission of the nuclei of heavy elements required a significant amount of energy neutrons.238 is used as the protection devices and fission.However, most of the mined uranium-238 is used for the synthesis of plutonium used in nuclear weapons.
long half-life of uranium scientists use to calculate the age of the individual minerals and celestial bodies in general.Uranium clocks are fairly universal mechanism for such calculations.At the same time, it was calculated to age more or less accurately, it is necessary to know not only the quantity of uranium in different breeds, and the ratio of uranium and lead as the final product, which is converted into uranium core.
There is another way to calculate the rocks and minerals, it is associated with the so-called spontaneous fission of uranium nuclei.As is well known, as a result of spontaneous fission of uranium in vivo the particles with tremendous force bombarded a number of substances are, reserving special tracks - tracks.
It is for the number of tracks, knowing the half-life of uranium, the researchers conclude, and the age of a rigid body - whether it be an ancient breed or relatively "young" vase.The fact is that the age of an object is directly proportional to the quantitative indicators of uranium atoms, the nucleus is bombarded it.
