Nuclear radiation . shows the characteristics of this type of radiation . It occurs when there is a mass-energy surplus in a nucleus . The emission of particles from an unstable nucleus is called radioactive decay .
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- 1 Types of decay
- 2 Matter and radiation
- 3 Methods of energy transfer
- 4 Effects of radiation
- 5 Sources
Types of decay
- Emission of atoms with two protons and two neutrons . These particles are identical to helium nuclei (4He).
- There are two types of decay, beta positive and beta negative. Positive beta is an emission from a positron accompanied by an antineutrino . The negative beta is the emission of an electron accompanied by a neutrino .
- It is the emission of very high frequency photons . The radioactive atom remains the same, but with a lower energy state .
Matter and radiation
The radiation is used for example in radiography and radiotherapy . Radiography studies the ways in which X-rays penetrate different materials. The radiation therapy seeks to eliminate malignant tissues by applying radioactivity.
The most common effects of radiation are ionization and atomic excitation of the material, all of which can be followed by chemical changes. The alpha particles are positively charged and large mass. As they penetrate matter, they electrically attract nearby electrons as they pass , producing ionization of these atoms. When a radioactive atom generates any positron , the positron temporarily associates with an electron , forming an “atom” called a positronium , in which the electron and the positron rotate around each other. Positronium has a half-life of 10 ^ (- 10) seconds. Then the two particles are annihilated by emitting gamma rays .
The X – ray and gamma having no load, can not be eliminated by the ionization through a material. They suffer other mechanisms that in the end make them disappear, transferring their energy by three different methods. These methods are the photoelectric effect , theCompton effect and pair production.
Energy transfer methods
- Photoelectric effect
The photon encounters an electron from the material in question, transferring all its energy to it, disappearing the original photon.
- Compton effect
The photon collides with an electron, the electron only acquires part of the photon’s energy , the rest of the energy is carried away by another photon of lower energy and diverted
- Pair production
It happens when a photon approaches the electric field of a nucleus , the photon becomes an electron-positron pair . The positron at the end of its path forms a positronium and then they annihilate producing two annihilation photons . The neutrons have no electric charge , but are affected by the nuclear force . Neutrons do not ionize due to not interacting with electrons , the only effect they can produce is to impact nuclei, causing nuclear reactions or elastic dispersions .
The damaging effects of ionizing radiation in a living organism are mainly due to the energy absorbed by the cells and the tissues that form it. This energy is absorbed by ionization and atomic excitation , produces chemical decomposition of the molecules present. At less than 100 mSv, no clinical response is expected. When increasing the dose, the organism presents different manifestations until it reaches death. The average lethal dose is that at which fifty percent of the irradiated individuals die, this is 4 Sv (4000 mSv). Sometimes large doses of radiation can be applied to limited areas (as in radiation therapy), causing only local damage.
When ionizing radiation strikes a living organism, reactions at the cellular level are primarily in the membranes, the cytoplasm, and the nucleus . The interaction in the membranes produces alterations of permeability, which means that they can exchange fluids in larger amounts than normal. The cell does not die but its multiplication functions are not carried out. In the event that the interaction is in the cytoplasm , whose main substance is waterAs it is ionized, unstable radicals are formed. Some of these radicals tend to bind to form water molecules and molecules of hydrogen (H), which are not harmful to the cytoplasm. Others combine to form hydrogen peroxide (H2O2), which does cause disturbances in cell function . The most critical situation arises when hydronium (HO) is formed, which causes poisoning . When ionizing radiation reaches the nucleus of the cell , it can cause alterations in genes and even breakdown of chromosomes, causing that when the cell divides it does so with different characteristics from the original cell.
Cells can experience increased or decreased volume, death, a dormant state, genetic mutations, and cancer . These radioactive properties can become beneficial, it is the case of radiotherapy that uses high doses of radiation to eliminate malignant tissues in the body. However, due to the nature of radioactivity, it is unavoidable to affect other nearby healthy organs.
Damage to germ cells will result in damage to the individual’s offspring. Biological effects can be classifiedin somatic and hereditary. Damage to the genes of a somatic cell can cause damage to the daughter cell, but would be a non-inherited somatic effect . Genetic damage is the effect of mutation on a chromosome or a gene , this leads to an inherited effect only when the damage affects a germ line. The syndrome of acute radiation is the set of symptoms that people intensely irradiated throughout the body. It consists of nausea , vomiting , anorexia , weight loss, fever, and intestinal bleeding .
The effects of radioactivity on local parts can be erythema or necrosis of the skin , hair loss , necrosis of internal tissues , temporary or permanent sterility , abnormal reproduction of tissues such as the epithelium of the gastrointestinal tract , abnormal organ function hematopoietic ( bone marrow and spleen ), or functional disturbances of the nervous system and other systems.