Radioactivity .
Can be considered a natural physical phenomenon by which some bodies or chemical elements, called radioactive radiation sources that have the ability to impress photographic plates, ionized gases, to produce fluorescence, through opaque to ordinary light, etc. Because of that ability, they are often called ionizing radiation (in contrast to non-ionizing). The electromagnetic radiation may be emitted in the form of X-rays or gamma rays or corpuscular, such as helium nuclei, electrons and positrons, protons or other. In short, a phenomenon that occurs in the nuclei of certain elements, which are capable of developing into nuclei of atoms of other elements.
The radioactivity ionizes it crosses. One exception is the neutron, which has no charge, but ionizes the matter indirectly. In radioactive decays have various types of radiation: alpha, beta, gamma and neutrons. In this process, the nuclei of atoms of elements decay with formation of new nuclei that correspond to new elements and release energy.
Classes radiation .
It was found that radiation can be of three different classes, known as particle decays and radiation:
• Alpha particle: They are positively charged particles flows consist of two protons and two neutrons (helium nuclei). Are deflected by electric and magnetic fields. They are a little sharp, but very ionizing. They are very energetic. They were discovered by Rutherford, who posed as alpha particles through a thin glass and trapped in a discharge tube. This type of radiation emitted nuclei of heavy elements near the end of the periodic table (A> 100). These cores have many protons and the electric repulsion is very strong, so you tend to get N approximately equal to Z, and for that emits an alpha particle. In the process shows a lot of energy, which is converted into kinetic energy of the alpha particle, so that these particles come out with very high speeds.
• Beta decay: They are streams of electrons (negative beta) and positrons (positive beta) resulting from the decay of neutrons or protons in the nucleus when it is in an excited state. Is deflected by magnetic fields. Is more pervasive, although the ionization power is not as high as that of alpha particles. Therefore, when an atom ejects a beta particle, its atomic number increases or decreases one unit (due to the proton won or lost). There are three types of beta radiation, beta radiation, "which is the spontaneous emission of electrons from the nuclei, the beta radiation +, in which a proton from the nucleus disintegrates and gives rise to a neutron, a positron or Beta + particle and a neutrino, and finally the electron capture that occurs in nuclei with excess protons, in which the nucleus captures an electron from the electronic bark, which is attached to a proton to give a neutron core.
• Gamma radiation: It is electromagnetic waves. This is the most penetrating radiation. When electromagnetic waves of short wavelengths have greater penetration and requires very thick layers of lead or concrete to stop them. In this type of radiation does not lose its core identity, but it is clear from the energy left over to move to another lower energy state by emitting gamma rays, or high-energy photons. This type of emission accompanies alpha and beta. Because it is so pervasive and so energetic, it is the most dangerous type of radiation.
Use reactors in Japan.
The nuclear power reactors that were affected by the earthquake are boiling water and are designed to withstand earthquakes of 7.5 degrees. The magnitude reached by the largest earthquake in Japan in the last 140 years, completely overcame. However, nuclear plants resisted well.
A nuclear plant has a water container, thanks to nuclear fission, it becomes steam, passes through a turbine, generating electricity and then converted back into water, to repeat the cycle.
As part of an accident prevention program, when an earthquake starts, the reactor automatically shuts down. It happened in Japan. Then begins a core cooling, necessary even when off the reactors. In the case of disaster, the need for cooling engines were affected by the earthquake and were not working.
How do we affect the release of radioactivity?
• The effects of radiation on living organisms are harmful to their physical integrity. They can be immediate or delayed, depending on the dose. When the human body suddenly receive high radiation doses, death can occur. High amounts received in small fractions spaced late effects, such as leukemia, cancer, cataracts and other degenerative processes. Low doses and spread out over time can cause late effects or abnormalities in future generations.
• It should be noted himself genetic effects of radioactivity, which threaten plant populations, animals and even humans. Certain anomalies in some wading birds in the Arctic regions have been explained by some scholars as a result of radioactive contamination.
• Environmentally, the consequences of nuclear disasters and the use of atomic bombs are disastrous. Radioactive isotopes, whose half-life is sometimes of millions of years, enter the biogeochemical cycles and are collected by agencies through selective metabolic processes. As for example with radioactive iodine-as could be demonstrated on the island of Rongelap, old people whose children suffered mostly major disruptions because of the radioactive clouds from there came to nuclear tests conducted in Bikini Atoll. Indeed, radioactive iodine, following the normal metabolic pathways of iodine, comes to the thyroid gland, where it accumulates making serious disruption of their operations, and delays as well as derangements of the growth of malignant tumors in the gland.
Japan and Chernobyl .
• The accident at the Chernobyl NPP in 1986 (Ukraine) was the most serious happened so far.
• Both this event as Fukushima (Japan) have been classified as level 7, the maximum on the INES scale.
• In Fukushima nobody was killed by direct exposure to radiation from the plant.
• Both accidents have different elements and that emissions outside Fukushima equivalent to 10% of those released by the reactor 4 at Chernobyl (Ukraine).
• Chernobyl exploded inside.
• On April 26, 1986 was declared the alert level 7 after the explosion of reactor number 4 of the Chernobyl plant in Ukraine (which then belonged to the USSR). This is the main difference between the Chernobyl accident and Fukushima. Japan has not yet been given for an explosion of that magnitude in the core of a nuclear reactor.
• Was the equipment itself, operating in central Ukraine that caused (unintentionally) the disaster, while in Japan, a strong earthquake of magnitude 9 on the Richter scale left without power in Fukushima and tsunami damaged diesel generators that supply electricity to the plant when it ceases to receive from abroad. This triggered a series of hydrogen explosions that hit the outside of the reactor structure.
• In Chernobyl reactor explosion occurred when he was in full operation, while in Fukushima Units 1, 2 and 3 were arrested immediately after the earthquake.
• The Soviet authorities began evacuating people in the vicinity of the Chernobyl plant 36 hours after the accident. A month later, all the inhabitants who had lived within a radius of 30 kilometers of the plant had been displaced. However, the radiation affected a much larger area than the area evacuated.
• In Japan, the evacuation radius increased, the day after the accident, 10 to 20 kilometers and Nipponese authorities carried out an emergency plan to try to prevent a greater extent, the population exposure to radioactive materials .
• "Prevention in Chernobyl was much lower than in Japan. "
• There is no comparison to Chernobyl, which was a 3.200MW reactor that exploded while working at full capacity. The three reactors in Japan were at 500MW each and were successfully extinguished with the first tremors of the earthquake. Once it fails, its output is reduced to 5% or 25MW.
"With the damaged systems, the material continues to heat up and produce steam and pressure. The pressure needs to be freed. The two explosions were controlled to release the pressure, did not go by themselves. "
