types of radioactivity rikhvanov leonid p., professor, dsc in geology and mineralogy nadeina luiza...
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Types of radioactivity
Rikhvanov Leonid P., professor,DSc in Geology and MineralogyNadeina Luiza V., associate professor,PhD in Philology
TOMSK -2015
RADIOACTIVITY (from Latin radio — radiate the beam and
activus — active), spontaneous transformation unstable atom
nuclei in atom nuclei of other elements, conducting by emission
of particles or gamma quantum.
There are three types of radioactivity. Gamma rays come from the nucleus of the atom of a radioactive isotope. They are the most energetic and most penetrating of all radiation. Some radiation travel as particles not waves and is also emitted by the radioactive isotope. One is alpha particles that lose energy quickly. A hand or thin piece of paper stops it. Beta particles are high speed electrons that travel close to the speed of light and can penetrate a hand but not concrete.
When an atom undergoes radioactive decay, it emits one or more forms of
radiation with sufficient energy to ionize the atoms with which it interacts.
Ionizing radiation can consist of high speed subatomic particles ejected from the
nucleus or electromagnetic radiation (gamma-rays) emitted by either the
nucleus or orbital electrons.
The time in which half the atoms of a particular radioactive
nuclide disintegrate. It is called half life. The half-life is a
characteristic property of each radioactive isotope. During one half life
from 100 atoms of radionuclides only 50 ones remain. Different
radionuclides have got various speed of half life.
Element Half life Iodine-131 8,04 days Krypton-85 10,72 yearsTritium 12,3 yearsStrontium-90 28,5 years
Caesium-137 30 yearsCarbon-14 5370 years
Iodine -129 17 million years
All radioactive elements decompose due to a law of radioactive decay:
N = No * е-λtwhere Nо – number of radioactive atoms in initial time of appearance nuclide (tо);е - base of the natural logarithm (2,718);λ- constant of radioactive decay; it is different for various radionuclides; t - time, passed from (to).Constant of radioactive decay identifies so-called half life (T):Т= ln2/λ = 0,693/λ.Half life Т½ is one of main characteristics of radioactive substance.
Natural Anthropogenic
Long-lived 235,238,234U, 232Th, 40K, 87Rb, l52Sm, l87Re, 138La,l 76Lu и др.
Fission-fragment elements
134,137Cs, 90Sr, 106Ru, l4lCe, l40La, l47Nd, 99Tc, l47Pm and others
Short-lived and medium-lived
uranium series: radon and etc.thorium series: thoron and etc. Actinouranium series: actinon and etc.
Activation products 54Fe, 60Co, 65Zn, 22Na, 32P
и т.д.
Constantly forming in nature as a result of nuclear reactions with protons, neutrons and other particles of earth and cosmic origin
14N (n,p) - 14С (5,8*103years)6Li (n) - 3H (12,3 years)2Н (n,у) - 3Н2Н (n,p) - 3Н238U (n,у) - ß - 237Np- ß - 239Pu (negligibly small quantities).Spontaneous decay 238U leads to formation of 90Sr, 99Тс, 147Рm and etc.
Elements of nuclear addition
reaction
Neptunium (Np)Plutonium (Pu)Americium (Am)Curium (Сm)Berkelium (Bk)Californium (Cf)Mendelevium (Md) and etc.
Radioactive elements classification
Fission-fragment elements
Образование осколочных радионуклидов
Nuclear fission induced by neutrons is the most important source of artificial radionuclides. This process is
used to obtain energy in modern nuclear reactors. Nuclear fission gives also the main portion of
radionuclides at explosion of nuclear charges.
Transuranium radioactive elements – chemical elements with atomic
number more than uranium-92, forming as a result of neutron
absorption according to the formula:
β β
βn,γ+ ( ) n,γ
All known radioactive elements should be divided into two groups natural and anthropogenic.
Natural radioactive elements can be divided into:
Fission-fragment (uranium-235 nuclei fission products under thermal neutrons effect): 90Sr, 134Cs, 137Cs, 140La, 131I, 129I, 99Tc, 106Ru, 141Ce
Activation products– due to interaction neutrons, gamma-quanta and etc. with substance:
56Fe, 22Na, 60Co, 65Zn, 32P
Transuranuim radioactive elements – chemical elements with atomic number more than uranium-92:
240Pu, 239Pu, 239U, 239Np, 247Cm, 241Am
Fission radioactive elements
The main most dangerous radioactive elements and their properties
element Half life Type of decay
ActivityКи/g
Emit energy
Alpha Beta Gamma
Krypton-85 10,72 years β
Iodine-131 8,04 days β
Iodine-129 17million years
β
Strontium-90 28,5 years β
Caesium-137 30 years β-γ
Lanthanum-138 100 billion years
β
Europium-152 13,3 years γ