Radioactividad (Eng.)

Archivo:Radioactive.svg
Traditional Symbol used to indicate the presence of radioactivity.

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...RADIOACTIVITY...
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The discovery of radioactivity in 1986 by Henry Becquerel, and subsequent study undertaken by himself and by the Curies, show the items massivest  continuously emit a type of radiation. The study of the components of this radiation, the laws of disintegration of the constitution of atomic nucleous and reactions nuclear, constitute the body of knowledge of nuclear physics.
What is IT? 
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It is the property of some substances to emit radiation. Becquerel,  studying fluorescence, found that some substances emitted spontaneously,without previous stimulation, and continuously, radiation. As was new the discovery og X-rays, he thought the emition of radioactive substances was similar radiation. Today we know  radiation includes gamma rays and two types of particles leaving large speed: α and β. Gamma radiation are electromagnetic waves (more energy than X-rays). Indeed, including the light radiation, photons contain behave like particles. Alpha and beta particles have an associated wave. Becquerel studied the potential of X-rays with substances.
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The radioactivity (or 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.
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Radioactivity
ionize the place that through .Neutron is the exception., which has no charge, but ionizes the matter indirectly. In radioactive decays have various types of radiation: alpha, beta, gamma and neutrons.
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Radioactivity is a property of the isotopes that are "unstable", ie, that remain in an excited state in their electronic and nuclear layers, so that to reach its ground state, they must lose energy. They do electromagnetic emissions or particulate emissions with a certain kinetic energy. This occurs by varying the energy of its electrons (emitting X-rays) or its nucleons (gamma ray) or by varying the isotope (the output from the core electrons, positrons, neutrons, protons or heavier particles), and in several successive steps , which a heavy isotope can develop into a much lighter, such as uranium, with the passing of centuries, becoming just lead.
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The radioactivity is used to obtain nuclear energy is used in medicine (radiation therapy and diagnostic radiology) and industrial applications (measurements of thicknesses and densities, etc.).
Components
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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.
Archivo:Alfa beta gamma radiation.svg
Clases de radiación ionizante y cómo detenerla. Las partículas alfa (núcleos de helio) se detienen al interponer una hoja de papel. Las partículas beta (electrones y positrones) no pueden atravesar una capa de aluminio. Sin embargo, los rayos gamma (fotones de alta energía) necesitan una barrera mucho más gruesa, y los más energéticos pueden atravesar el plomo.
 
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Types of radioactivity:
 
. Radioactivity is radiation that is constantly present in the environment and is emitted from a variety of natural and artificial sources. Primary contributions come from:
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*Sources in the earth. These include sources in food and water, which are incorporated in the body, and in building materials and other products that incorporate those radioactive sources.
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*Sources from space, in the form of cosmic rays.
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*Sources in the atmosphere. One significant contribution comes from the radon gas that is released from the Earth's crust and subsequently decays into radioactive atoms that become attached to airborne dust and particulates. Another contribution arises from the radioactive atoms produced in the bombardment of atoms in the upper atmosphere by high-energy cosmic rays.
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Naturally occurring sources are responsible for the vast majority of radiation exposure. However, not including direct exposure from radiological imaging or therapy, about 3%. of background radiation comes from man-made sources such as:
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+Self-luminous dials and signs
+Global radioactive contamination due to historical nuclear weapons testing
+Nuclear power station or nuclear fuel reprocessing accidents
+Normal operation of facilities used for nuclear power and scientific research
+Emissions from burning fossil fuels, such as coal fired power plants
+Emissions from nuclear medicine facilities and patients
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So the radioactivity can be:
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*Natural: manifested by the isotopes found in nature.
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*Artificial or induced, expressed by the radioisotopes produced in artificial transformations.
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Fukushima Daiishi Plant,Japan  Reactor:

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The operator of the troubled Japanese nuclear plant in Fukushima acknowledged Tuesday that, as suspected, experts say fuel also merged two other reactors, as well as the number one, and stated that deliver all the information available to the IAEA.
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"It is also possible that fusion reactors occurred in two three," said a spokesman for Tokyo Electric Power (TEPCO), which just released its latest analysis of the measurements made in Fukushima Daiichi.
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"Most of the fuel has fallen, probably at the bottom (of the pressure vessel), as in the reactor number one," said the spokesman, who dismissed the risk of a new fusion uncontrolled.
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TEPCO had already hinted that a merger had occurred inside the reactors two and three, but it is the first time that is so so.
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The reactors "are being subjected to cooling operations and his condition is stable," the spokesman added.
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The giant tsunami caused on 11 March by a terrible earthquake of magnitude 9 seriously damaged the Fukushima nuclear power plant, disabling the cooling of four of the six reactors at the plant, causing the heating of the fuel rods.
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For several weeks after the disaster of March 11, the operator, as the Japanese government had mentioned only a partial meltdown, saying the reactors were relatively stable and hazardous radioactive leaks had been largely stalled.
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According to latest information released by TEPCO and Nuclear Safety Agency of Japan, the pressure vessel and the reactor containment enclosure 1 "would be damaged and leaks." The state of the reactor vessels 2 and 3 is "unknown", although the confinement enclosure 2 "likely to be damaged and leak."
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Although discovered damage are higher than expected, TEPCO said last week that the timetable for ending the crisis continues, reiterating that will reduce radioactive leaks before July and the temperature of the reactor is stabilized at 100 degrees Celsius before January.
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The Japanese government Tuesday approved the establishment of an independent expert commission to investigate the accident, the worst since the one in Chernobyl (Ukraine) in 1986.
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The commission shall submit a final report within a year.
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On the other hand, a team of a dozen foreign experts of the International Atomic Energy Agency (IAEA) are in Japan to discuss this crisis.
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The Japanese Minister of Economy, Trade and Industry, Banri Kaieda, said Tuesday that his country will give the IAEA all information available about the disaster.
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"We will make available all information we have," said Kaieda the inspection team, which will remain in Japan until June 2 and present the results of his mission at a meeting of ministers of the IAEA in Vienna next month .
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The group is led by Mike Weightman, chief inspector of nuclear installations in Britain, and comprises representatives from 12 countries including the United States, China, France, Russia and South Korea.
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"Our mission is to find information so that we can draw conclusions for all countries to improve nuclear safety," Weightman said after the meeting with the minister.
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Radiation effects on humans and on enviroment:
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Effects on humans:
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Of the 60 contaminants that exist in the reactor core, which would have major consequences for human health would be iodine, strontium 90 and cesium.
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*Iodine affects immediately and leave mutations in the genes from which they can develop thyroid cancer
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*Strontium: It accumulates in the bones for at least 30 years.
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*Cesium: It is deposited in the muscles.

+Other effects:
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-It increases the risk of cancer, especially bone, muscle and brain tumors.
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-Decreases the body's immunity increases the capacity to suffer diseases
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-Change the play, affecting more women than men. An egg fertilized altered by radiation and then generate anomalies in the fetus, even after years.
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Environment:
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Nuclear contamination spread through the air, is deposited on the ground and at sea and joins the nutritional chain of animals, plants and vegetables.
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Source: Eduardo Rodriguez-Farré, Radiation biologist at the Institute of Biomedical Research of Barcelona
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SO:
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The release of large quantities of radioactive material has serious effects on public health and the environment and the radiation does not look or smell, as stated in radiation biologist Eduard Rodríguez-Farré Spanish.
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 At the core of a nuclear reactor from the fission of uranium, there are more than 60 radioactive contaminants, some other long-lived and short, that build up in him being similar to our biological elements.
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 Among them, iodine, strontium 90 and cesium (C-137) are among the most harmful pollutants to human health, increasing the risk of all types of cancer and decrease the body's immunity.
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The condition of iodine is immediate, causes mutations in the genes and increases the risk of cancer, especially thyroid.
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 Cesium is deposited in the muscles, while strontium accumulates in bone for a minimum period of 30 years. Both substances multiply the possibility of cancer of the bone, muscle or brain tumors and other pathologies.
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 Radiation also affect the reproductive system, more women than men. Sperm fully regenerate every 90 days, however, the eggs remain in the ovaries a lifetime and if an egg is altered by radiation and subsequently fertilized will produce malformations in the fetus, even years later.
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 When the main mode of transmission is inhalation, ingestion is only effective iodine tablets. The thyroid is eliminating the excess iodine and thus, when saturated with normal iodine can be inhaled by removing the radioactive iodine.
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 If the contact is through the skin, is removed by washing with detergent as the body, such as hair and nails, and put away clothes.
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 The unit of measurement of the intensity of radiation is the gray (Gy) that quantifies the dose absorbed by living tissue. One gray is equivalent to the absorption of one joule of radiation energy per kilogram of irradiated material. This unit was established in 1975.
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 From the accumulation of a gray of radiation in the human body, there is malaise, headache, nausea, vomiting, fever and diarrhea.
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Between doses of 3 and 5 grays, the equivalent to what is commonly used in radiotherapy, there is bleeding, anemia and infections decreased white blood cells.
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 To exceed six grays, it can cause death within days or within hours, because the effects of radiation are cumulative.
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 With doses of more than 15 grays is inevitably death.
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The most common conditions caused by excessive radiation are cancer, gastrointestinal disorders, disorders of the bone marrow and the reproductive system (infertility, birth defects, ...) and the weakening of the immune system. 
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The environment also suffers from the potential consequences of radiation unleashed by a meltdown, which can affect an area of ​​tens of miles. 
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Nuclear contamination is deposited on the ground and at sea and enters the food chain of living beings through a process of bioaccumulation. Going from about others, including plants, animals and humans.
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In general, the effects of radiation are cumulative and an exhibition, though small and continuous, it is dangerous.
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NUCLEAR Accidents:

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Fukushima (Japan) VS. Chernobyl (Ukraine) :

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Chernobyl (Ukraine)

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Archivo:The dangerous view - Pripyat - Chernobyl.jpg

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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.
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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). 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.
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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.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.According to official post-Soviet data, about 60% of the fallout landed in Belarus.
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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.
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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, 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. 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. A 2006 report predicted 30,000 to 60,000 cancer deaths as a result of Chernobyl fallout. A Greenpeace report puts this figure at 200,000 or more. A Russian publication, Chernobyl, concludes that 985,000 excess deaths occurred between 1986 and 2004 as a result of radioactive contamination.
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Fukushima (Japan)

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The Fukushima Daiichi nuclear disaster (福島第一原子力発電所事故 Fukushima Dai-ichi genshiryoku hatsudensho jiko) is a series of fires, equipment failures and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the 9.0 magnitude Tōhoku earthquake and tsunami on 11 March 2011. The plant comprises six separate boiling water reactors maintained by the Tokyo Electric Power Company (TEPCO). This accident is the largest of the 2011 Japanese nuclear accidents arising from the Tōhoku earthquake and tsunami, and experts consider it to be the second largest nuclear accident after the Chernobyl disaster, but more complex as multiple reactors are involved.
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At the time of the quake, Reactor 4 had been de-fueled while 5 and 6 were in cold shutdown for planned maintenance. The remaining reactors shut down automatically after the earthquake, with emergency generators starting up to run the control electronics and water pumps needed to cool reactors. The plant was protected by a seawall designed to withstand a 5.7 m (19 ft) tsunami but not the 14 m (46 ft) maximum wave which arrived 41–60 minutes after the earthquake.The entire plant was flooded, including low-lying generators and electrical switchgear in reactor basements and external pumps for supplying cooling seawater. The connection to the electrical grid was broken. All power for cooling was lost and reactors started to overheat, owing to natural decay of the fission products created before shutdown. The flooding and earthquake damage hindered external assistance.
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Evidence soon arose of partial core meltdown in Reactors 1, 2, and 3; hydrogen explosions destroyed the upper cladding of the buildings housing Reactors 1, 3, and 4; an explosion damaged the containment inside Reactor 2; multiple fires broke out at Reactor 4. Despite being initially shut down, Reactors 5 and 6 began to overheat. Fuel rods stored in pools in each reactor building began to overheat as water levels in the pools dropped. Fears of radiation leaks led to a 20 km (12 mi) radius evacuation around the plant while workers suffered radiation exposure and were temporarily evacuated at various times. One generator at Unit 6 was restarted on 17 March allowing some cooling at Units 5 and 6 which were least damaged. Grid power was restored to parts of the plant on 20 March, but machinery for Reactors 1 through 4, damaged by floods, fires and explosions, remained inoperable. Flooding with radioactive water continues to prevent access to basement areas where repairs are needed.However, on 5 May, workers were able to enter reactor buildings for the first time since the accident.
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Measurements taken by the Japanese science ministry and education ministry in areas of northern Japan 30–50 km from the plant showed radioactive caesium levels high enough to cause concern. Food grown in the area was banned from sale. Based on worldwide measurements of iodine-131 and caesium-137, it was suggested that the releases of those isotopes from Fukushima are of the same order of magnitude as those from Chernobyl in 1986; Tokyo officials temporarily recommended that tap water should not be used to prepare food for infants.Plutonium contamination has been detected in the soil at two sites in the plant,although further analysis revealed that the detected density are within limits from fallout generated from previous atmospheric nuclear tests. Two workers hospitalized as a precaution on 25 March had been exposed to between 2000 and 6000 mSv of radiation at their ankles when standing in water in Unit 3. Radiation levels varied widely over time and location, from well below 1 mSv/h to slightly over 1000 mSv/h. Normal background radiation varies from place to place but delivers a dose equivalent rate of about 0.3 µSv/h. For comparison, one chest x-ray is about 0.02 mSv and an abdominal CT scan is nominally less than 10 mSv.
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Japanese officials initially assessed the accident as Level 4 on the International Nuclear Event Scale (INES) despite the views of other international agencies that it should be higher. The level was successively raised to 5 and eventually to 7, the maximum scale value. The Japanese government and TEPCO have been criticized for poor communication with the public and improvised cleanup efforts. Experts have said that a workforce in the hundreds or even thousands would take years or decades to clean up the area. On 20 March, the Chief Cabinet Secretary Yukio Edano announced that the plant would be decommissioned once the crisis was over.

Archivo:Logo iso radiation.svg
Nuevo símbolo de advertencia de radiactividad adoptado por la ISO en 2007 para fuentes que puedan resultar peligrosas. Estandard ISO #21482.

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