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