THE RADIOACTIVITY
The radioactivity it can be considered a natural physical phenomenon by the one which some bodies or chemical elements, radioactive calls, emit radiations that have the property of impressing photographic badges, to ionize gases, to produce fluorescence, to cross opaque bodies to the ordinary light, etc. due to that capacity, you/they is usually denominated radiations ionizantes (in contrast with the non ionizantes). The emitted radiations can be electromagnetic, in form of rays X or rays gamma, or corpuscular, like they can be nuclei of helium, electrons or positrones, protons or others. In summary, it is a phenomenon that happens in the nuclei of certain elements that are able to become nuclei of atoms of other elements.
The radioactivity ionizes the means that through.A exception constitutes it the neutron that doesn't possess load, but it ionizes the matter in form insinuation. In the radioactive disintegrations several radiation types are had: alpha, beta, gamma and neutrons.
The radioactivity is a property of the isotopes that you/they are "unstable", that is to say that stay in a state excited in its electronic or nuclear layers, with that that, to reach its fundamental state, they should lose energy. They make it in electromagnetic emissions or in emissions of particles with a certain kinetic energy. This takes place varying the energy of their electrons (emitting rays X) or of their nucleones (I line gamma) or varying the isotope (when emitting from the nucleus electrons, positrones, neutrons, protons or heavier particles), and in several successive steps, with what a heavy isotope can finish becoming one much slighter, as the uranium that, with lapsing of the centuries, it finishes becoming lead.
The radioactivity takes advantage for the obtaining of nuclear energy, it is used in medicine (radiotherapy and radiodiagnóstico) and in industrial applications (measures of thickness and densities, among other).
The radioactivity can be:
Natural: manifested by the isotopes that are in the nature.
Artificial or induced: manifested by the radioisotopes taken place in artificial transformations.
Natural radioactivity
In 1896 Henri Becquerel discovered that certain salts of uranium emit radiations spontaneously, when observing that they veiled the photographic badges wrapped in black paper. He/she made rehearsals with the mineral in hot, in cold, powdered, dissolved in acids and the intensity of the mysterious radiation was always the same one. Therefore, this new property of the matter that received the radioactivity name, didn't depend on the physical form or chemistry in which were the atoms of the radioactive body, but rather it was a property that resided in the same interior of the atom.
The study of the new phenomenon and their later development owes himself almost exclusively to Marie's marriage and Pierre Curie who found other radioactive substances: the torio, the polonio and the radius. The intensity of the emitted radiation was proportional to the quantity of present uranium, for that that Marie Curie deduced that the radioactivity is an atomic property. The phenomenon of the radioactivity originates exclusively in the nucleus of the radioactive atoms. It is believed that he/she originates due to the interaction neutron-proton. When studying the radiation emitted by the radius, he/she was proven that it was complex, because when applying him a field magnetic part of her he/she strayed of their trajectory and another part nr.
Soon it was seen that all these reactions come from the atomic nucleus that Ernest described Rutherford in 1911 who also demonstrated that the radiations emitted by the salts of uranium can ionize the air and to produce the discharge of loaded bodies electrically.
With the use of the neutrino, particle described in 1930 by Wolfgang Pauli but non measure but up to 1956 for Clyde Cowan and their collaborators, it was able to be described the radiation beta.
In 1932 James Chadwick discovered the existence of the neutron that Pauli had predicted in 1930, and immediately later Enrico Fermi discovered that certain radiations not emitted in phenomena very common of disintegration they are in fact neutrons.
Artificial radioactivity
The artificial radioactivity, also called induced radioactivity, he/she takes place when certain stable nuclei are bombarded with appropriate particles. If the energy of these particles has an appropriate value, they penetrate the bombarded nucleus and they form a new nucleus that, in the event of being unstable, he/she disintegrates later radioactively. It was discovered by the husbands Jean Frédéric Joliot-Curie and Irène Joliot-Curie, bombarding nuclei of boron and of aluminum with particles alpha. They observed that the bombarded substances emitted radiations after moving away the body radioactive originator of the bombing particles.
In 1934 Fermi it was in an experiment bombarding nuclei of uranium with the recently discovered neutrons. In 1938, in Germany, Lise Meitner, Otto Hahn and Fritz Strassmann verified the experiments of Fermi. In 1939 they demonstrated that a part of the products that you/they appeared when carrying out these experiments was barium. Very soon they confirmed that it was been of the division of the nuclei of uranium: the first experimental observation of the fission. In France, Jean Frédéric Joliot-Curie discovered that, besides the barium, secondary neutrons are emitted in that reaction, that makes feasible the reaction in chain.
Also in 1932, Mark Oliphant speculated on the coalition of slight nuclei (of hydrogen), and soon after Hans Bethe described the operation of the stars with base in this mechanism.
The study of the radioactivity allowed a bigger knowledge of the structure of the atomic nucleus and of the subatomic particles. The possibility opened up of transforming some elements into others. Even reality the ancestral dream of the alchemists was made of creating gold starting from other elements... although in practical terms it is not profitable.
NATURE OF THE RADIOACTIVITY
The radiations can be:
Rays Alpha (a)
These rays are formed by material particles that present two units of positive electric load and four units of mass. They are lightly deviated by the action of intense magnetic forces. They can ionize the gases and to penetrate in the matter. They are stopped or absorbed when he/she puts on before them a metallic sheet. Their initial speed varies from 109 cm. / s up to 2 x 109 cm. / s.
Rays Beta (b)
The particles that conform to the Rays Beta are from a smaller mass to that of the rays alpha and they are of unit of load negative. They are projected to big speeds, although this depends on the origin source and in occasions they are emitted to a next speed to that of the light (3×1010 cm. / s).
Rays Gamma (g)
Their nature is different to the rays alpha and beta, since they don't experience deviation before the electric and/or magnetic fields. Although they have a smaller wave longitude that the rays X, acts like an electromagnetic radiation of same nature. They can cross lead sheets and it travels big distances in the air. Their nature is ondulatoria and he/she doesn't have electric load, neither mass. Their ionization capacity is weaker in comparison with the rays alpha and beta.
It is undeniable that the radiation affects to the organisms. It can make sick them or to cure. It can be administered as any medicine, or to have lethal effects. It depends of how it is used.
We know that the ionization that takes place can give place to chemical transformations in the matter. If it is alive matter, they necessarily interfere these changes with the vital functions of the cells that you/they receive radiation. Also, as some radiations they can penetrate in the body, this effects can take place in organs or in cells of very diverse functions.
To have a comparison point, let us think of a burn of Sun. The solar rays, mainly the ultraviolet one, they take place in the skin effects that all to know us; at some time we have felt the ardor of a burn for exhibition in the sun too lingering. He/she is due to the chemical changes induced in the skin that inclusive they can kill to the cells, as well as we all have experienced when coming off the useless skin then. Now then: the skin is designed to support these effects, because, when being damaged, easily it can be replaced by new cells that in turn assume the vital function of protecting to the rest of the organism. The radiations ionizantes that penetrate in the body can cause equivalent damages in the fabrics, but not only of the skin, but of the whole body. These damages can be permanent if they happen in organs that are not regenerated, as the brain.
The effects that the radiation takes place in the organisms have been classified in four groups: those that produce cancer, the genetic mutations, the effects in the embryos during the pregnancy and the burns for excessive exhibitions. The first two groups generally happen when the received doses are small, but lingering. The third, in a stage of the life in that the organism is specially sensitive to be reproducing its cells to quick rhythm. The room happens in accidents or in the nuclear explosions. Many studies have been made on how each one of these cases it is presented under diverse circumstances.
I USE OF THE REACTORS IN JAPON
THEY PURIFY IN JAPAN IT DILUTES RADIO-ACTIVE FOR USE IN REACTORS
The workers in the nuclear plant of Fukushima in Japan have begun the works of transferring radio-active water toward an installation of waste treatment. The task will facilitate the repairs in the cooling system. Meanwhile the possible coalition has been informed in the reactors but the graveness of the damage is ignored.
It is alone a step in the long process to solve the crisis.
The Agency of Nuclear and Industrial Security of Japan pointed out that the water contaminated in the base of the reactor number two will be removed by stages but as soon as possible to avoid its filtration to the ocean.
The quantity of liquid is of 70 thousand tons that which would take several months in moving away. The material then will stay in a deposit in the plant. The place was flooded as a consequence of the tsunami but it was possible to drain in order to win space for the water with a bigger radiation level.
JAPAN | CHERNOBYL |
The situation in Japan is completely desperate. The only of the three reactors of the power station of Fukushima that seemed to work correctly, the number 2, it is the one that finally has converted in a very real possibility a nuclear catastrophe. At the last moment of the night the engineers continued working to contrarreloj to cool the nucleus of the reactor and to avoid so it exploded due to the high temperature. But they didn't achieve it. An explosion was listened to come from the reactor 2, this dawn. And the same Japanese government admitted that a part of the structure of contention of the reactor seems to be damaged, insinuating that it is possible a radio-active escape. The deflagration exploded part of the primary container of the nucleus and it caused a flight of an uncertain quantity of radioactive material, according to the Agency of Nuclear Security. The agency Kyodo informed that the radiation levels "they overcame the legal limit" after the explosion. It is more, superior radiation levels to the normal thing arrived last night to so alone to 100 km of Tokyo, in the prefecture of Ibaraki, located among Fukushima, where he/she is the power station nuclear accident victim, and the Japanese capital, Kyodo affirmed. France was the first country in lifting the alert voice about the danger. For the president of the Authority of the Nuclear Security (ASN), André-Claude Lacoste, "there is not doubt that he/she has already taken place a coalition principle", and it elevated the level of alert up to 5 or even 6. The catastrophe of Chernobyl registered a level 7, the maximum of the scale. Fukushima has already surpassed the level of radiation of the power station of "Three Mile Island", American power station that in 1979 it suffered the partial coalition of the nucleus of the reactor. The alert is world. Europe ordered yesterday to revise all its atomic power stations. (To see P. 20) "AT global level, the radioactive waste in the environment are important", the ASN impacted. " We are before a crisis that could last weeks", it highlighted. According to the agency Kyodo, the radiation detected yesterday in the plant of Fukushima is double the maximum seen up to now, according to an information facilitated by the Tokyo Electric Power, landlady of the installation. Japan has already requested officially help to the International Agency of the Atomic Energy, in short that he/she sends a team of experts to try to brake the disaster. The most serious thing is that the problems in the reactor number 2 could have been avoided. In fact, they seem the work of a saboteur more than of a group of nuclear experts. The crisis began soon after the explosion in the building of the reactor 3 at first hour of the morning that had already been premature. What nobody had foreseen is that the deflagration damaged the system of refrigeration of the number 2 that until then it worked without problems. Soon several trucks of firemen began to pump water of the sea to avoid a sobrecalentamiento of the nucleus, but one of them was left without fuel. There were not enough water and the bars of uranium that feed the reactor they were exposed during two and a half hours, an extremely serious situation that, according to some experts, it can only drive to the coalition of the nucleus of the reactor. Also, the steel frame that protects the nucleus was also damaged by the explosion. They didn't tranquilize the nuclear engineer's words a lot Masahi Goto who explained to the BBC that the reactor of Fukushima uses blended oxide as fuel, and that the coalition point for a later nuclear explosion is lower than in other plants where conventional fuel is used. It is more, if it happened an explosion, Goto said, "the plutonium could be spread around an area double big one that in a conventional nuclear explosion". "The nucleus of the reactor is not prepared to support earthquakes or tsunamis, and its manufacturers knew it." For the expert, "next 24 hours are critical." Now, those responsible for Fukushima are come before the tesitura from cooling the reactors without having trucks cistern. One of the measures that were shuffling at the last moment is to make holes in the walls of the reactors for despresurizarlos, that if, with the price of having to loose to the atmosphere radioactive vapor. The sensation that the Japanese government is hiding information more evident yesterday it was made among the citizens. Fukuyama "it won't end in a similar situation to that of Chernobyl", he/she insisted yesterday from Tokyo the government's spokesman, Yukio Edano who had denied that the reactor number 2 will suffer an explosion like it had already happened on Saturday to the 1 and on Sunday at the 3. On the other hand, the Tokyo Electric Power remembered that if the feared coalition of the nucleus of the reactor takes place he/she doesn't mean that everything is lost. There are two barriers of security to maintain the radiation inside the plant. The first one is the frame that wraps the reactor, and the second are the building in yes, built totally of cement. If also that it failed, then yes that would not have returned behind to the catastrophe. | The Chernobyl disaster (locally, Chornobyl Catastrophe) was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine (officially Ukrainian SSR), which was under the direct jurisdiction of the central Moscow's authorities. An explosion and fire released large quantities of radioactive contamination into the atmosphere, which spread over much of Western USSR and Europe. It is considered the worst nuclear power plant accident in history, and is one of only two classified as a level 7 event on the International Nuclear Event Scale (the other being the Fukushima I nuclear accidents).[1] The battle to contain the contamination and avert a greater catastrophe ultimately involved over 500,000 workers and cost an estimated 18 billion rubles, crippling the Soviet economy.[2] The disaster began during a systems test on Saturday, 26 April 1986 at reactor number four of the Chernobyl plant, which is near the city of Prypiat and within a close proximity to the administrative border with Belarus and Dnieper river. There was a sudden power output surge, and when an emergency shutdown was attempted, a more extreme spike in power output occurred, which led to a reactor vessel rupture and a series of explosions. These events exposed the graphite moderator of the reactor to air, causing it to ignite.[3] The resulting fire sent a plume of highly radioactive smoke fallout into the atmosphere and over an extensive geographical area, including Pripyat. The plume drifted over large parts of the western Soviet Union and Europe. From 1986 to 2000, 350,400 people were evacuated and resettled from the most severely contaminated areas of Belarus, Russia, and Ukraine.[4][5] According to official post-Soviet data,[6][7] about 60% of the fallout landed in Belarus. The accident raised concerns about the safety of the Soviet nuclear power industry, as well as nuclear power in general, slowing its expansion for a number of years and forcing the Soviet government to become less secretive about its procedures.[8][notes 1] Russia, Ukraine, and Belarus have been burdened with the continuing and substantial decontamination and health care costs of the Chernobyl accident. A report of the International Atomic Energy Agency,[7] examines the environmental consequences of the accident. Estimates of the number of deaths potentially resulting from the accident vary enormously: Thirty one deaths are directly attributed to the accident, all among the reactor staff and emergency workers.[9] A UNSCEAR report places the total confirmed deaths from radiation at 64 as of 2008. The World Health Organization (WHO) suggests it could reach 4,000.[10] A 2006 report predicted 30,000 to 60,000 cancer deaths as a result of Chernobyl fallout.[11] A Greenpeace report puts this figure at 200,000 or more.[12] A Russian publication, Chernobyl, concludes that 985,000 excess deaths occurred between 1986 and 2004 as a result of radioactive contamination On 26 April 1986, at 01:23 (UTC+3), reactor four suffered a catastrophic power increase, leading to explosions in its core. This dispersed large quantities of radioactive fuel and core materials into the atmosphere[14]:73 and ignited the combustible graphite moderator. The burning graphite moderator increased the emission of radioactive particles, carried by the smoke, as the reactor had not been encased by any kind of hard containment vessel. The accident occurred during an experiment scheduled to test a potential safety emergency core cooling feature, which took place during the normal shutdown procedure. The attempted experiment Even when not actively generating power, nuclear power reactors require cooling, typically provided by coolant flow, to remove decay heat.[15] Pressurized water reactors use water flow at high pressure to remove waste heat. After an emergency shutdown (SCRAM), the core still generates a significant amount of residual heat, which is initially about seven percent of the total thermal output of the plant. If not removed by coolant systems, the heat could lead to core damage.[16][17] The reactor that exploded in Chernobyl consisted of about 1,600 individual fuel channels, and each operational channel required a flow of 28 metric tons (28,000 liters (7,400 USgal)) of water per hour.[14]:7 There had been concerns that in the event of a power grid failure, external power would not have been immediately available to run the plant's cooling water pumps. Chernobyl's reactors had three backup diesel generators. Each generator required 15 seconds to start up but took 60–75 seconds[14]:15 to attain full speed and reach the capacity of 5.5 MW required to run one main cooling water pump.[14]:30 imperative to put those fires out and protect the cooling systems of reactor 3.[14]:42 Inside reactor 3, the chief of the night shift, Yuri Bagdasarov, wanted to shut down the reactor immediately, but chief engineer Nikolai Fomin would not allow this.[why?] The operators were given respirators and potassium iodide tablets and told to continue working. At 05:00, however, Bagdasarov made his own decision to shut down the reactor, leaving only those operators there who had to work the emergency cooling systems.[14]:44 |
NUCLEAR REACTORS JAPAN
CHERNOBYL
CHERNOBYL
