Radioactivity | | | | | |
| | | | | | |  Automatic translation | | | | | | Ionizing radiation and radioactive | | Updated May 20, 2012 | | Category: Nuclear physics |  | | | | | The cell is the basic unit of living systems, it is the elementary particle of life.
Each cell is in a fabric which itself is an organ that performs a function. The cell obeys a manufacturing plan contained in the molecule of deoxyribonucleic acid, or DNA, present in all living cells.
At the microscopic level, cells are composed of atoms in electromagnetic balance, it is what makes the matter remains coherent.
Radioactivity is a phenomenon that occurs in the nucleus of atoms deep.
Ionizing radiation Ionization is the act of removing or adding electrical loads to an atom. The atom that loses or wins loads, is more in balance electric it is called ion. Ionizing radiation or radioactive, can tear off electrons from the biological material, if the energy of radioactive particles is greater than the binding energy of electrons. Dividing cells are most vulnerable to high radiation, for example, hematopoietic stem cells contained in the bone marrow that give rise to all blood cells.
To extract nuclear energy, engineers used a special radio-isotope, the nucleus of uranium 235, to break easily in its nucleus. Indeed its nucleus is unstable, it decays naturally, ie the cohesive force is not sufficient to hold the protons and neutrons.
Naturally it ejects particles and produces radioactive neutron radiation and energy.
When a neutron is sent on a core of uranium 235, it makes it even more unstable it becomes fissile and breaks into two parts.
| | This fission releases particles of ionizing radiation and high energy.
The "disintegration" (transformation of matter into energy), a radioactive nucleus such as uranium, causes the emission of high energy radiation.
These decays are accompanied by emission of gamma rays, whose wavelengths are shorter than those of X-rays, on the order of 10-9 meters, which makes it dangerous because it crosses the field.
Gamma rays produce damage similar to those produced by X-ray or ultraviolet (burns, cancer and genetic mutations).
Radioisotopes natural are, americium-241, antimony 125, carbon 14, cesium 134, 135 and 137, chlorine 36, cobalt 60, 242 and curium 244, iodine 129, 131 133, 85 and krypton-89, phosphorus 32, 239 and plutonium-241, polonium-210, potassium 40, radium 226 and 242, ruthenium 106, selenium 75, Sulphur 35, strontium-90, thorium 234, 3 tritium, uranium 235 and 238. nota : The DNA, genetic information and heredity, produces occasional errors, most mistakes are bad, but sometimes these genetic mutations, produce beneficial effects, which allow the system to continue its evolution in an environment that is favorable... | | * The electromagnetic spectrum includes all windows of light. Maxwell found that light is an electromagnetic wave and there is no reason to limit the wavelength thereof at the interval corresponding to the spectrum of visible light, the spectrum is light. The electromagnetic wavelengths vary between 10-16 m and several thousands of kilometers. Over the wavelength is shorter, the frequency is high. The highest is that of gamma rays. | | | | | | | | Sources of radiation | | | | | | | | | | The main source of radioactivity is natural.
It comes mainly from radon, a radioactive gas produced by the decay of uranium present in certain rocks such as granite.
We are exposed to radon, very variable, from 1 to 100 milli Sievert per year, it represents the largest share of human exposure, 42% of total exposure.
In addition to building materials, plaster, brick, concrete, 0.1 to 1000 mSv / year.
Cosmic rays are also a source of natural radiation, particularly at altitude. The dose is around 0.3 mSv / year, but it increases with air travel.
About 10% of the radiation received by a person from his own body, mainly due to the decay of carbon 14 and potassium 40. However, the main medical irradiation, received at radiographs. It represents about 50% of the average exposure to natural radiation.
During a medical scanner, the patient receives an average dose of 0.05 mSv for a local review, 25 mSv for a CT scan of the skull and 150 mSv for a whole body scanner.
It is recommended not to exceed three per year exams body.
Coal contains potassium, uranium and thorium, concentrated by a factor of 10 in the ashes and part of this radioactivity is found in the smoke and slightly increases the exposure of the order of micro-sievert per year . | | Human activities, such as fallout from nuclear weapons testing, fallout from nuclear accidents, increase the annual dose received by the world's population.
Earth, despite its magnetic shield, is continuously irradiated by a stream of particles, cosmic rays, high energy from outer space and the Sun.
This cosmic radiation remains very low at sea level The radioactive dose rate is measured in Gy / h (gray per hour), formerly the rad / h (rad per hour).
The equivalent dose is measured in Sv / h (sievert per hour).
The French nuclear sites are organized into zones corresponding to the doses. The Blue Zone (2.5 to 7.5 mSv / h), the green zone (7.5 to 25 mSv / h), the yellow zone (25 mSv / h 2 mSv / h, the orange zone (2 to 100 mSv / h), the red zone (> 100 mSv / h). The natural environment emits radiation ranging from 0.2 mSv / h to 1 mSv / h.
The dose rate that produces hazardous biological effects is from 1 mSv / h, that is to say "yellow zone". nota : the isotope 14 of carbon content in the air and living organisms, remains roughly constant over time. Only after the death of the organism, the concentration of C14, decreases in its tissues.
This property is used for dating the time of death if it does not exceed 50 000 years. | | 
* Pictogram launched by the IAEA, which poses a risk of danger of death or serious injury.
The effects of ionizing radiation, to its macroscopic manifestation is a complex process, the dose-effect relationship has a direct impact on policies for radiation protection and public health.
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