Understand ability of atomic kernels to break up with emission of certain particles as radioactivity. Radioactive decay becomes possible when it goes with energy allocation. This process is characterized by isotope life time, type of radiation and energy of the let-out particles.
What is radioactivity
On radioactivity in physics understand instability of kernels of a number of atoms which is shown in their natural ability spontaneously to break up. This process is followed by emission of ionizing radiation which is called radiation. Energy of particles of ionizing radiation can be very big. By means of chemical reactions radiation cannot be caused.
Radioactive materials and technical installations (accelerators, reactors, the equipment for x-ray manipulations) are radiation sources. Radiation exists only until absorption in substance.
Radioactivity is measured in becquerels (Bq). Quite often use other unit – curie (Ki). The activity of a source of radiation is characterized by number of disintegrations in a second.
Measure of the ionizing impact of radiation on substance is the exposition dose, most often it is measured in X-rays (P). One X-ray – very big size. Therefore in practice most often use million or thousand shares of X-ray. Radiation in critical doses can quite become the cause of radiation sickness.
The concept of a half-life period is closely connected with a concept of radioactivity. So call time for which the number of radioactive kernels decreases twice. Each radionuclide (appearance of radioactive atom) has the half-life period. It can be equal to seconds or billions of years. For scientific research that principle is important that the half-life period of the same radioactive material is constant. To change it it will not turn out.
General information about radiation. Types of radioactivity
At synthesis of substance or its disintegration there is an emission of the elements making atom: neutrons, protons, electrons, photons. Say at the same time that there is a radiation of such elements. Similar radiation is called ionizing (radioactive). Other name of this phenomenon – radiation.
Understand process at which substance radiates elementary charged particles as radiation. The type of radiation is defined by those elements which are radiated.
Call ionization process of formation of the loaded ions or electrons of neutral molecules or atoms.
Radioactive radiation is divided into several types which are caused by microparticles, various by the nature. The substance particles participating in radiation possess different power influence, different penetration. Action of radiation will be a miscellaneous also biological.
When speak about types of radioactivity, understand types of radiation as them. In science carry the following groups to them:
- alpha radiation;
- beta radiation;
- neutron radiation;
- gamma radiation;
- x-ray radiation.
Alpha radiation
This type of radiation arises in case of disintegration of isotopes of the elements which are not differing in stability. So call the radiation of heavy and positively charged alpha particles. Them are helium atomic nuclei. Alpha particles can turn out at disintegration of difficult atomic nuclei:
- thorium;
- uranium;
Alpha particles are distinguished by big weight. Speed of radiation of this look is rather low: it is 15 times lower than the speed of light. At contact with substance the heavy alpha particles enter collision with its molecules. There is an interaction. However particles lose energy therefore their penetration is very small. Alpha particles the simple sheet of paper can detain.
And still in interaction with substance of an alpha particle cause its ionization. If it is about cages of a living organism that alpha radiation is capable to damage them, destroying at the same time fabrics.
Alpha radiation has the smallest penetration among other types of ionizing radiation. However consequences of impact of such particles on living tissue it is considered the heaviest.
The living organism of this type can receive radiation dose if radioactive elements get in an organism with food, air, water, through wounds or cuts. When radioactive elements get in an organism, they by means of a blood-groove are carried by all its parts, collect in fabrics.
Certain types of radioactive isotopes can exist long time. Therefore at hit in an organism they can cause in cellular structures very serious changes – up to full regeneration of fabrics.
Radioactive isotopes cannot come out an organism. The organism is not able to neutralize, acquire, process or utilize such isotopes.
Neutron radiation
So the technogenic radiation which arises at atomic explosions or in nuclear reactors is called. Neutron radiation does not possess a charge: Facing substance, it very poorly interacts with parts of atom. The penetration of this type of radiation is high. Materials in which there is a lot of hydrogen can stop it. It can be, in particular, the container with water. Neutron radiation also hardly gets through polyethylene.
When passing through biological fabrics the neutron radiation is capable to cause to cellular structures very serious damage. It has essential weight, speed is much higher than it, than at alpha radiation.
Beta radiation
It arises at the time of transformation of one element into another. Processes at the same time go in the atomic nucleus that leads to changes in properties of neutrons and protons. At this type of radiation the neutron turns into a proton or a proton in a neutron. Process is followed by the radiation of a positron or electron. Speed of beta radiation is close to the speed of light. Elements which are radiated by substance carry the name of beta particles.
At the expense of the high speed and the small sizes of emitted particles the beta radiation has high penetration. However its ability to ionize substance several times is less, than at alpha radiation.
Beta radiation without any work gets through clothes and somewhat – through living tissues. But if particles meet on the way dense structures of substance (for example, metal), they begin to interact with it. At the same time beta particles lose a part of the energy. Completely the metal leaf thickness in several millimeters is capable to stop such radiation.
Alpha radiation is dangerous only at direct contact with radioactive isotope. And here beta radiation can do harm to an organism at distance in several dozen meters from a radiation source. When radioactive isotope appears in an organism, it tends to accumulation in bodies and fabrics, damaging them and causing significant changes.
Separate radioactive isotopes of beta radiation have the long period of disintegration: having got to an organism, they can quite irradiate it over the years. Cancer can be a consequence of it.
Gamma radiation
So call the power radiation of electromagnetic type when substance lets out photons. This radiation accompanies disintegration of atoms of substance. Gamma radiation is shown in the form of electromagnetic energy (photons) which is released during change of a condition of an atomic nucleus. Gamma radiation has the speed equal to the speed of light.
When there is a radioactive decay of atom, another is formed of one substance. Atoms of the turned-out substances are energetically unstable, they are in the so-called excited state. When neutrons and protons influence at each other, protons and neutrons come to a state at which forces of interaction become balanced. Atom throws out surplus of energy in the form of gamma radiation.
Its penetration is high: gamma radiation without effort gets through clothes and living tissues. But to it to pass through metal much more difficult. The thick layer of concrete or steel can stop such type of radiation.
The main danger of gamma radiation is that it is capable to overcome very long distances, making at the same time strong impact on an organism for hundreds of meters from a radiation source.
X-ray radiation
Understand the electromagnetic radiation having an appearance of photons as it. X-ray radiation arises in case of transition of an electron from one atomic orbit to another. In the characteristics such radiation is similar to gamma radiation. But its penetration is not so high, wavelength in this case is more.
One of sources of x-ray radiation is the Sun; however the atmosphere of the planet gives sufficient protection against this influence.