Studying the phenomenon of radioactivity, every scientistrefers to such an important characteristic of it as a half-life. As is known, the law of radioactive decay says that every second in the world there is a decay of atoms, while the quantitative characteristics of these processes are directly related to the number of available atoms. If for a certain period of time half of all the available quantity of atoms disintegrates, then the decay of ½ from the remaining atoms will require the same amount of time. This time period is called the half-life period. For different elements it is different - from a thousandths of a millisecond to billions of years, as, for example, when it comes to the half-life of uranium.
Uranium, as the heaviest of all existing inthe natural state of the elements on Earth, is in general the most beautiful object for studying the process of radioactivity. This element was discovered back in 1789 by the German scientist M. Klaproth, who gave him the name in honor of the newly discovered planet Uranus. The fact that uranium is radioactive was accidentally established at the end of the 19th century by the French chemist A. Becquerel.
The half-life of uranium is calculated by the same formula as similar periods of other radioactive elements:
T_ {1/2} = au ln 2 = frac {ln 2} {lambda},
where "au" is the average lifetime of the atom, "lambda" is the basic decay constant. Since ln 2 is approximately 0.7, the half-life is only 30% shorter on average than the total lifetime of the atom.
Despite the fact that to date, scientists14 isotopes of uranium are known, in nature they are found only three: uranium-234, uranium-235 and uranium-238. The half-life of uranium is different: for U-234 it is "only" 270 thousand years, and the half-life of uranium-238 exceeds 4.5 billion. The half-life of uranium-235 is in the "golden middle" - 710 million years.
It should be noted that the radioactivity of uranium innatural conditions is high enough and allows, for example, to light the photographic plates within just an hour. At the same time, it should be noted that in all uranium isotopes only U-235 is suitable for making a filling for a nuclear bomb. The thing is that the half-life of uranium-235 in industrial conditions is less intense than its "counterparts," and therefore the output of unnecessary neutrons is minimal here.
The half-life of uranium-238 is significantlyexceeds 4 billion years, but it is now actively used in the nuclear industry. So, in order to launch a chain reaction in the fission of heavy nuclei of this element, a significant amount of neutron energy is needed. Uranium-238 is used as a protection in the apparatus of fission and synthesis. However, most of the uranium-238 produced is used for the synthesis of plutonium used in nuclear weapons.
The duration of the half-life of uranium scientistsare used to calculate the age of individual minerals and celestial bodies as a whole. Uranium clock is quite a universal mechanism for this kind of calculations. At the same time, for the age to be calculated more or less accurately, it is necessary to know not only the amount of uranium in these or those rocks, but also the ratio of uranium and lead as the final product into which uranium nuclei are converted.
There is another way of calculating rocks and minerals,it is connected with the so-called spontaneous fission of uranium nuclei. As is known, as a result of spontaneous fission of uranium in natural conditions, its particles with colossal force bombard nearby substances, leaving behind a special traces - tracks.
It is by the number of these tracks, knowing at the same timethe half-life of uranium, scientists, and conclude about the age of a solid body - whether it's an ancient breed or a relatively "young" vase. The thing is that the age of the object is directly proportional to the quantitative index of uranium atoms whose nuclei have bombarded it.
