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This is not necessarily a news thread but I had some questions pertaining to nuclear energy and I've done some googling to find the answers from government sites as well as the EPA and nuclear energy sites. I thought this might be useful in helping us have a better understanding of the nuclear situation in Japan. If you have a question or an answer (or both) feel free to post and share in this thread. I think a bit of knowledge can go a long way.
Q: Where does uranium come from?
A: Small amounts of uranium are found almost everywhere in soil, rock, and water. However, concentrated deposits of uranium ores are found in just a few places, usually in hard rock or sandstone. These deposits are normally covered over with earth and vegetation. Uranium has been mined in Canada, the southwest United States, Australia, parts of Europe, the former Soviet Union, Namibia, South Africa, Niger and elsewhere.
Source: FAQ 2-Where does uranium come from?
Q: Where does plutonium come from?
A: Plutonium is created from uranium in nuclear reactors. When uranium-238 absorbs a neutron, it becomes uranium-239 which ultimately decays to plutonium-239. Different isotopes of uranium and different combinations of neutron absorptions and radioactive decay, create different isotopes of plutonium.
Some of the plutonium-239 in the fuel rods burns (fissions) along with uranium and helps produce heat, which is converted into electricity. As fission continues, the reaction products remain in the fuel pellets and absorb neutrons, slowing ("poisoning") the fission process. Finally, the ratio of poisons to fissional materials reaches a point at which the fuel is said to be "spent" and must be replaced. However, even spent fuel contains some plutonium.
The majority of plutonium was produced for nuclear weapons in several government reactors designed to maximize the production of plutonium. Between 1944 and 1988, the U.S. built and operated these ‘production reactors' at high-security government facilities. In all, the U.S. produced about 100 metric tons of plutonium.
The reactors made plutonium by bombarding special fuel rods containing uranium with neutrons. Once the maximum amount of plutonium was produced, workers removed the fuel rods (now called ‘spent fuel') from the reactor. The spent fuel rods were extremely radioactive, and the process for recovering the plutonium used only remote-controlled equipment.
First workers used strong acid to dissolve the fuel rods. Then they treated the mixture with chemicals to precipitate the plutonium so that it would settle out. The process was very expensive and at the time made plutonium about the most expensive material on earth. This processing also left behind over 100 million gallons of exceedingly hazardous mixed wastes of acids and radioactive fission products. Part of our legacy of nuclear weapons production is dealing with these high-level wastes.
In extremely rare cases, rocks with a high localized concentration of uranium can provide the right conditions for making small amounts of plutonium naturally. This natural process is called spontaneous fission. Only very small (trace) amounts of natural plutonium have ever been found in nature.
Source: Plutonium | Radiation Protection | US EPA
Q: What are the properties of plutonium?
A: Plutonium is a silvery-grey metal that becomes yellowish when exposed to air. It is solid under normal conditions, and is chemically reactive.
Plutonium has at least 15 different isotopes, all of which are radioactive. The most common ones are Pu-238, Pu-239, and Pu-240. Pu-238 has a half-life of 87.7 years. Plutonium-239 has a half-life of 24,100, and Pu-240 has a half-life 6,560 years. The isotope Pu-238 gives off useable heat, because of its radioactivity.
Source: Plutonium | Radiation Protection | US EPA
Q: What is plutonium used for?
A: Plutonium-239 is used to make nuclear weapons. For example, the bomb dropped on Nagasaki, Japan, in 1945, contained Pu-239. The plutonium in the bomb undergoes fission in an arrangement that assures enormous energy generation and destructive potential.
The isotope, plutonium-238, is not useful for nuclear weapons. However it generates significant heat through its decay process, which make it useful as a long-lived power source. Using a thermocouple, a device that converts heat into electric power, satellites rely on plutonium as a power source. Tiny amounts also provide power to heart pacemakers.
Some foreign countries mix isotopes of plutonium and uranium to manufacture special reactor fuel called mixed-oxide fuel, for commercial nuclear power reactors. The plutonium increases the power output. The U.S. does not currently manufacture mixed-oxide fuel, but is funding research in this type of reactor fuel as a means of dealing with excess plutonium in U.S. stockpiles.
Source: Plutonium | Radiation Protection | US EPA
Q: How does plutonium get into the environment?
A: Plutonium was dispersed world wide from atmospheric testing of nuclear weapons conducted during the 1950s and ‘60s. The fallout from these tests left very low concentrations of plutonium in soils around the world.
Nuclear weapons production and testing facilities (Hanford, WA; Savannah River, GA; Rocky Flats, CO; and The Nevada Test Site, in the United States, and Mayak and Semi Plafinsk in the former Soviet Union), also released small amounts. Some releases have occurred in accidents with nuclear weapons, the reentry of satellites that used Pu-238, and from the Chernobyl nuclear reactor accident.
Source: Plutonium | Radiation Protection | US EPA
Q: How does plutonium change the environment?
A: All isotopes of plutonium undergo radioactive decay. As plutonium decays, it releases radiation and forms other radioactive isotopes. For example, Pu-238 emits an alpha particle and becomes uranium-234; Pu-239 emits an alpha particle and becomes uranium-235.
This process happens slowly since the half-lives of plutonium isotopes tend to be relatively long: Pu-238 has a half-life of 87.7 years; Pu-239 has a half-life is 24,100 years, and Pu-240 has a half-life of 6,560 years. The decay process continues until a stable, non-radioactive element is formed.
Source: Plutonium | Radiation Protection | US EPA
Q: How do people come in contact with plutonium?
A: Residual plutonium from atmospheric nuclear weapons testing is dispersed widely in the environment. As a result, virtually everyone comes into contact with extremely small amounts of plutonium.
People who live near nuclear weapons production or testing sites may have increased exposure to plutonium, primarily through particles in the air, but possibly from water as well. Plants growing in contaminated soil can absorb small amounts of plutonium.
Source: Plutonium | Radiation Protection | US EPA
Q: How do I know if I am near plutonium?
A: You must have special equipment to detect the presence of plutonium.
Source: Plutonium | Radiation Protection | US EPA
Q: How does plutonium get into the body?
A: People may inhale plutonium as a contaminant in dust. It can also be ingested with food or water. Most people have extremely low ingestion and inhalation of plutonium. However, people who live near government weapons production or testing facilities may have increased exposure. Plutonium exposure external to the body poses very little health risk.
Source: Plutonium | Radiation Protection | US EPA
Q: What does plutonium do once it gets into the body?
A: The stomach does not absorb plutonium very well, and most plutonium swallowed with food or water passes from the body through the feces. When inhaled, plutonium can remain in the lungs depending upon its particle size and how well the particular chemical form dissolves. The chemical forms that dissolve less easily may lodge in the lungs or move out with phlegm, and either be swallowed or spit out. But, the lungs may absorb chemical forms that dissolve more easily and pass them into the bloodstream.
Once in the bloodstream, plutonium moves throughout the body and into the bones, liver, or other body organs. Plutonium that reaches body organs generally stays in the body for decades and continues to expose the surrounding tissue to radiation.
Source: Plutonium | Radiation Protection | US EPA
Q: How can plutonium affect people's health?
A: External exposure to plutonium poses very little health risk, since plutonium isotopes emit alpha radiation, and almost no beta or gamma radiation. In contrast, internal exposure to plutonium is an extremely serious health hazard. It generally stays in the body for decades, exposing organs and tissues to radiation, and increasing the risk of cancer. Plutonium is also a toxic metal, and may cause damage to the kidneys.
Source: Plutonium | Radiation Protection | US EPA
Q: Is there a medical test to determine exposure to plutonium?
A: There are tests that can reliably measure the amount of plutonium in a urine sample, even at very low levels. Using these measurements, scientists can estimate the total amount of plutonium present in the body. Other tests can measure plutonium in soft tissues (such as body organs) and in feces, bones, and milk. However, these tests are not routinely available in a doctor's office because they require special laboratory equipment.
Source: Plutonium | Radiation Protection | US EPA
Q: What can I do to protect myself and my family from plutonium?
A: Since plutonium levels in the environment are very low, they pose little risk to most people. However, people who live near government weapons production or testing sites may have higher exposure.
Plutonium particles in dust are the greatest concern, because they pose the greatest health risk. People living near government weapons facilities can track radiation monitoring data made available by site personnel. If radiation levels rise, they should follow the radiation protection instructions given by site personnel.
Source: Plutonium | Radiation Protection | US EPA
Q: What is the EPA doing to protect us from plutonium?
A: EPA sets health-based limits on radiation in air, soil, and water. Federal government agencies are required to meet EPA standards the same as commercial industries. Using its authority under the Safe Drinking Water Act, EPA limits the amount of radiation in community water systems by establishing maximum contaminant levels. Maximum Contaminant Levels limit the amount of activity from alpha emitters, like plutonium, to 15 picocuries per liter.
EPA also protects people against exposure from soil and ground water from sites that have been contaminated with plutonium. We set criteria that soil and ground water from the sites must meet before releasing the sites for public use.
Rather than limiting the concentration of plutonium itself, the criteria limit the cancer risk the sites pose. A person's added risk of developing cancer is limited to no more than about 1-in-10,000 and if possible to 1-in-1,000,000, or less. Under the Clean Air Act, EPA limits the dose to humans from radionuclides to 10 millirem from emissions to air.
Additional Information: EPA sets standards for radioactive waste storage and disposal facilities. We can't treat plutonium or other radioactive materials to get rid of their radioactivity. We can only isolate and store them until they decay. The extremely long half-lives of some plutonium radioisotopes make the management of spent nuclear fuel, and wastes from nuclear weapons facilities a difficult problem.
One of EPA's responsibilities has been to develop public health and safety standards for the two major U.S. nuclear waste storage and disposal facilities. The Waste Isolation Pilot Plant in New Mexico stores transuranic wastes. They range from slightly contaminated clothing to barrels of waste so radioactive that it can only be handled with remote control equipment. The proposed Yucca Mountain repository is designed to store high-level radioactive waste and spent nuclear fuel.
EPA also responds to radiation emergencies. Additionally, EPA helps state and local governments during emergencies that involve radioactive materials. We provide guidance on ways to protect people from harmful exposure to radiation. We can also monitor radiation levels in the environment and assess the threat to public health. We also work with international radiation protection organizations to prepare for large scale foreign emergencies such as Chernobyl. EPA also works with law enforcement agencies to develop counter terrorism plans.
Source: Plutonium | Radiation Protection | US EPA
Q: What is the difference between a nuclear bomb and a nuclear reactor?
A: * Nuclear Fission: In nuclear fission, the nuclei of atoms are split, causing energy to be released. The atomic bomb and nuclear reactors work by fission. The element uranium is the main fuel used to undergo nuclear fission to produce energy since it has many favorable properties. Uranium nuclei can be easily split by shooting neutrons at them. Also, once a uranium nucleus is split, multiple neutrons are released which are used to split other uranium nuclei. This phenomenon is known as a chain reaction.
Nuclear Fusion: In nuclear fusion, the nuclei of atoms are joined together, or fused. This happens only under very hot conditions. The Sun, like all other stars, creates heat and light through nuclear fusion. In the Sun, hydrogen nuclei fuse to make helium. The hydrogen bomb, humanity's most powerful and destructive weapon, also works by fusion. The heat required to start the fusion reaction is so great that an atomic bomb is used to provide it. Hydrogen nuclei fuse to form helium and in the process release huge amounts of energy thus producing a huge explosion.
Source: Nuclear Energy
Q: What are the advantages of nuclear energy?
A: o The Earth has limited supplies of coal and oil. Nuclear power plants could still produce electricity after coal and oil become scarce.
o Nuclear power plants need less fuel than ones which burn fossil fuels. One ton of uranium produces more energy than is produced by several million tons of coal or several million barrels of oil.
o Coal and oil burning plants pollute the air. Well-operated nuclear power plants do not release contaminants into the environment.
Source: Nuclear Energy
Q: What are the disadvantages of nuclear energy?
A: * Nuclear explosions produce radiation. The nuclear radiation harms the cells of the body which can make people sick or even kill them. Illness can strike people years after their exposure to nuclear radiation.
* One possible type of reactor disaster is known as a meltdown. In such an accident, the fission reaction goes out of control, leading to a nuclear explosion and the emission of great amounts of radiation.
o In 1979, the cooling system failed at the Three Mile Island nuclear reactor near Harrisburg, Pennsylvania. Radiation leaked, forcing tens of thousands of people to flee. The problem was solved minutes before a total meltdown would have occurred. Fortunately, there were no deaths.
o In 1986, a much worse disaster struck Russia's Chernobyl nuclear power plant. In this incident, a large amount of radiation escaped from the reactor. Hundreds of thousands of people were exposed to the radiation. Several dozen died within a few days. In the years to come, thousands more may die of cancers induced by the radiation.
* Nuclear reactors also have waste disposal problems. Reactors produce nuclear waste products which emit dangerous radiation. Because they could kill people who touch them, they cannot be thrown away like ordinary garbage. Currently, many nuclear wastes are stored in special cooling pools at the nuclear reactors.
o The United States plans to move its nuclear waste to a remote underground dump by the year 2010.
o In 1957, at a dump site in Russia's Ural Mountains, several hundred miles from Moscow, buried nuclear wastes mysteriously exploded, killing dozens of people.
* Nuclear reactors only last for about forty to fifty years.
Source: Nuclear Energy
Q: How does a nuclear reactor work?
A: Most nuclear reactors, including those at Japan's Fukushima Daiichi generating station, are essentially high-tech kettles that efficiently boil water to produce electricity. They rely on harnessing nuclear fission—the splitting of an atom into two smaller atoms, which also yields heat and sends neutrons flying. If another atom absorbs one of those neutrons, the atom becomes unstable and undergoes fission itself, releasing more heat and more neutrons. The chain reaction becomes self-sustaining, producing a steady supply of heat to boil water, drive steam turbines and thereby generate electricity.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: How much electricity does nuclear power provide in Japan and elsewhere?
A: With 54 nuclear reactors generating 280 billion kilowatt-hours annually, Japan is the world's third-largest producer of nuclear power, after the U.S. and France, according to data from the International Atomic Energy Agency. The Fukushima Daiichi station, which has been hit hard by the March 11 earthquake, houses six of those reactors, all of which came online in the 1970s.
Worldwide, nuclear energy accounts for about 15 percent of electricity generation; Japan gets nearly 30 percent of its electricity from its nuclear plants. The U.S. produces more nuclear power overall, but nuclear constitutes a smaller share of its energy portfolio. About 20 percent of U.S. electricity comes from nuclear power plants, making it the third-largest source of electricity in the country after coal (45 percent) and natural gas (23 percent).
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: What fuels a nuclear reactor?
A: Most nuclear reactors use uranium fuel that has been "enriched" in uranium 235, an isotope of uranium that fissions readily. (Isotopes are variants of elements with different atomic masses.) Uranium 238 is much more common in nature than uranium 235 but does not fission well, so fuel manufacturers boost the uranium 235 content to a few percent, which is enough to maintain a continuous fission reaction and generate electricity. Enriched uranium is manufactured into fuel rods that are encased in metal cladding made of alloys such as zirconium.
Reactor No. 3 at the Fukushima Daiichi station runs on so-called mixed oxide (MOX) fuel, in which uranium is mixed with other fissile materials such as plutonium from spent reactor fuel or from decommissioned nuclear weapons.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: How do you turn off a nuclear reaction?
A: Sustained nuclear fission reactions rely on the passing of neutrons from one atom to another—the neutrons released in one atom's fissioning trigger the fissioning of the next atom. The way to cut off a fission chain reaction, then, is to intercept the neutrons. Nuclear reactors utilize control rods made from elements such as cadmium, boron or hafnium, all of which are efficient neutron absorbers. When the reactor malfunctions or when operators need to shut off the reactor for any other reason technicians can remotely plunge control rods into the reactor core to soak up neutrons and shut down the nuclear reaction.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q:
Can a reactor melt down once the nuclear reaction is stopped?
A: Even after the control rods have done their job and arrested the fission reaction the fuel rods retain a great deal of heat. What is more, the uranium atoms that have already split in two produce radioactive by-products that themselves give off a great deal of heat. So the reactor core continues to produce heat in the absence of fissioning.
If the rest of the reactor is operating normally, pumps will continue to circulate coolant (usually water) to carry away the reactor core's heat. In Japan the March 11 earthquake and tsunami caused blackouts that cut off the externally sourced AC power for the reactors' cooling system. According to published reports, backup diesel generators at the power plant failed shortly thereafter, leaving the reactors uncooled and in serious danger of overheating.
Without a steady coolant supply, a hot reactor core will continuously boil off the water surrounding it until the fuel is no longer immersed. If fuel rods remain uncovered, they may begin to melt, and hot, radioactive fuel can pool at the bottom of the vessel containing the reactor. In a worst-case meltdown scenario the puddle of hot fuel could melt through the steel containment vessel and through subsequent barriers meant to contain the nuclear material, exposing massive quantities of radioactivity to the outside world.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: How can a meltdown be averted?
A: The Japanese plant's operators have made a number of attempts to cool the reactors, including pumping seawater into the reactor core to replenish the dwindling cooling fluid. The Tokyo Electric Power Company has also injected boric acid, an absorber of neutrons, into the reactors.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q:
How does this incident compare with Chernobyl or Three Mile Island?
A: At present, three of the reactors at Fukushima Daiichi station are seriously crippled. Units 1 and 3 have experienced explosions that destroyed exterior walls, apparently from buildups of hydrogen gas produced by the zirconium in the fuel rods reacting with coolant water at extremely high temperatures—but the interior containment vessels there thus far seem to be intact. A third explosion was reported March 15 at reactor No. 2, and the situation there appears direr. Pressure in the suppression pool—a doughnut-shaped water vessel below the reactor—dropped after the explosion, indicating that the containment vessel had been compromised.
In reactor Nos. 1, 2 and 3 water levels dropped enough to leave the fuel assemblies temporarily uncovered; those fuel rods are presumed to have suffered damage. And a fire at a pool storing spent fuel rods at dormant reactor No. 4 is posing additional hazards to the few workers remaining at the site.
Japanese officials initially rated the incident a level 4, an "accident with local consequences," on the seven-tier International Nuclear and Radiological Event Scale (INES), but Princeton University physicist Frank von Hippel told The New York Times that the Fukushima Daiichi situation is "way past Three Mile Island already." Three Mile Island, the highest-profile U.S. nuclear accident, was classified level 5—an "accident with wider consequences".
At that Pennsylvania nuclear station in 1979 a cooling malfunction combined with worker error led to a partial meltdown—about half of the reactor core melted and formed a radioactive puddle at the bottom of the steel pressure vessel. The vessel remained intact, but some radiation did escape from the plant into the surrounding environment.
The 1986 Chernobyl accident was far more devastating; it rates as a 7, or a "major accident," on the INES scale. In Ukraine, then part of the Soviet Union, a power surge caused an explosion in one of the plant's reactors, releasing huge doses of radioactive fallout into the air. Two plant workers died within hours, according to the U.S. Nuclear Regulatory Commission; 28 more died in the following months from radiation poisoning. The fallout from Chernobyl was widespread, and the health effects of the disaster are difficult to quantify. A report from the United Nations Scientific Committee on the Effects of Atomic Radiation found that 6,000 individuals who were under the age of 18 in Ukraine, Belarus or Russia at the time of the disaster had by 2006 contracted thyroid cancer, "a substantial fraction" of whom likely contracted the disease due to radiation exposure.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: How is a nuclear plant decommissioned?
A: Because the answer to this is actually quite lengthy, a full explanation of the process can be found here: NRC: Fact Sheet on Decommissioning Nuclear Power Plants
That is all I have time to answer but if anyone here has a question that can be answered or has an answer to share to a question please post or if you have a question and an answer that you think should be shared, please post it as well.
I am not trying to sway anyone from nuclear power has I understand it has it's advantages as well as disadvantages, but my hope is that with a little information sharing maybe we can have a better understanding of what is happening in Japan and have a lesser 'freak out' reaction.
I apologize for the lengthy post, but when it comes to nuclear energy and it's processes, there's seldom a short explanation.
Have a good day,
-Dix
Q: Where does uranium come from?
A: Small amounts of uranium are found almost everywhere in soil, rock, and water. However, concentrated deposits of uranium ores are found in just a few places, usually in hard rock or sandstone. These deposits are normally covered over with earth and vegetation. Uranium has been mined in Canada, the southwest United States, Australia, parts of Europe, the former Soviet Union, Namibia, South Africa, Niger and elsewhere.
Source: FAQ 2-Where does uranium come from?
Q: Where does plutonium come from?
A: Plutonium is created from uranium in nuclear reactors. When uranium-238 absorbs a neutron, it becomes uranium-239 which ultimately decays to plutonium-239. Different isotopes of uranium and different combinations of neutron absorptions and radioactive decay, create different isotopes of plutonium.
Some of the plutonium-239 in the fuel rods burns (fissions) along with uranium and helps produce heat, which is converted into electricity. As fission continues, the reaction products remain in the fuel pellets and absorb neutrons, slowing ("poisoning") the fission process. Finally, the ratio of poisons to fissional materials reaches a point at which the fuel is said to be "spent" and must be replaced. However, even spent fuel contains some plutonium.
The majority of plutonium was produced for nuclear weapons in several government reactors designed to maximize the production of plutonium. Between 1944 and 1988, the U.S. built and operated these ‘production reactors' at high-security government facilities. In all, the U.S. produced about 100 metric tons of plutonium.
The reactors made plutonium by bombarding special fuel rods containing uranium with neutrons. Once the maximum amount of plutonium was produced, workers removed the fuel rods (now called ‘spent fuel') from the reactor. The spent fuel rods were extremely radioactive, and the process for recovering the plutonium used only remote-controlled equipment.
First workers used strong acid to dissolve the fuel rods. Then they treated the mixture with chemicals to precipitate the plutonium so that it would settle out. The process was very expensive and at the time made plutonium about the most expensive material on earth. This processing also left behind over 100 million gallons of exceedingly hazardous mixed wastes of acids and radioactive fission products. Part of our legacy of nuclear weapons production is dealing with these high-level wastes.
In extremely rare cases, rocks with a high localized concentration of uranium can provide the right conditions for making small amounts of plutonium naturally. This natural process is called spontaneous fission. Only very small (trace) amounts of natural plutonium have ever been found in nature.
Source: Plutonium | Radiation Protection | US EPA
Q: What are the properties of plutonium?
A: Plutonium is a silvery-grey metal that becomes yellowish when exposed to air. It is solid under normal conditions, and is chemically reactive.
Plutonium has at least 15 different isotopes, all of which are radioactive. The most common ones are Pu-238, Pu-239, and Pu-240. Pu-238 has a half-life of 87.7 years. Plutonium-239 has a half-life of 24,100, and Pu-240 has a half-life 6,560 years. The isotope Pu-238 gives off useable heat, because of its radioactivity.
Source: Plutonium | Radiation Protection | US EPA
Q: What is plutonium used for?
A: Plutonium-239 is used to make nuclear weapons. For example, the bomb dropped on Nagasaki, Japan, in 1945, contained Pu-239. The plutonium in the bomb undergoes fission in an arrangement that assures enormous energy generation and destructive potential.
The isotope, plutonium-238, is not useful for nuclear weapons. However it generates significant heat through its decay process, which make it useful as a long-lived power source. Using a thermocouple, a device that converts heat into electric power, satellites rely on plutonium as a power source. Tiny amounts also provide power to heart pacemakers.
Some foreign countries mix isotopes of plutonium and uranium to manufacture special reactor fuel called mixed-oxide fuel, for commercial nuclear power reactors. The plutonium increases the power output. The U.S. does not currently manufacture mixed-oxide fuel, but is funding research in this type of reactor fuel as a means of dealing with excess plutonium in U.S. stockpiles.
Source: Plutonium | Radiation Protection | US EPA
Q: How does plutonium get into the environment?
A: Plutonium was dispersed world wide from atmospheric testing of nuclear weapons conducted during the 1950s and ‘60s. The fallout from these tests left very low concentrations of plutonium in soils around the world.
Nuclear weapons production and testing facilities (Hanford, WA; Savannah River, GA; Rocky Flats, CO; and The Nevada Test Site, in the United States, and Mayak and Semi Plafinsk in the former Soviet Union), also released small amounts. Some releases have occurred in accidents with nuclear weapons, the reentry of satellites that used Pu-238, and from the Chernobyl nuclear reactor accident.
Source: Plutonium | Radiation Protection | US EPA
Q: How does plutonium change the environment?
A: All isotopes of plutonium undergo radioactive decay. As plutonium decays, it releases radiation and forms other radioactive isotopes. For example, Pu-238 emits an alpha particle and becomes uranium-234; Pu-239 emits an alpha particle and becomes uranium-235.
This process happens slowly since the half-lives of plutonium isotopes tend to be relatively long: Pu-238 has a half-life of 87.7 years; Pu-239 has a half-life is 24,100 years, and Pu-240 has a half-life of 6,560 years. The decay process continues until a stable, non-radioactive element is formed.
Source: Plutonium | Radiation Protection | US EPA
Q: How do people come in contact with plutonium?
A: Residual plutonium from atmospheric nuclear weapons testing is dispersed widely in the environment. As a result, virtually everyone comes into contact with extremely small amounts of plutonium.
People who live near nuclear weapons production or testing sites may have increased exposure to plutonium, primarily through particles in the air, but possibly from water as well. Plants growing in contaminated soil can absorb small amounts of plutonium.
Source: Plutonium | Radiation Protection | US EPA
Q: How do I know if I am near plutonium?
A: You must have special equipment to detect the presence of plutonium.
Source: Plutonium | Radiation Protection | US EPA
Q: How does plutonium get into the body?
A: People may inhale plutonium as a contaminant in dust. It can also be ingested with food or water. Most people have extremely low ingestion and inhalation of plutonium. However, people who live near government weapons production or testing facilities may have increased exposure. Plutonium exposure external to the body poses very little health risk.
Source: Plutonium | Radiation Protection | US EPA
Q: What does plutonium do once it gets into the body?
A: The stomach does not absorb plutonium very well, and most plutonium swallowed with food or water passes from the body through the feces. When inhaled, plutonium can remain in the lungs depending upon its particle size and how well the particular chemical form dissolves. The chemical forms that dissolve less easily may lodge in the lungs or move out with phlegm, and either be swallowed or spit out. But, the lungs may absorb chemical forms that dissolve more easily and pass them into the bloodstream.
Once in the bloodstream, plutonium moves throughout the body and into the bones, liver, or other body organs. Plutonium that reaches body organs generally stays in the body for decades and continues to expose the surrounding tissue to radiation.
Source: Plutonium | Radiation Protection | US EPA
Q: How can plutonium affect people's health?
A: External exposure to plutonium poses very little health risk, since plutonium isotopes emit alpha radiation, and almost no beta or gamma radiation. In contrast, internal exposure to plutonium is an extremely serious health hazard. It generally stays in the body for decades, exposing organs and tissues to radiation, and increasing the risk of cancer. Plutonium is also a toxic metal, and may cause damage to the kidneys.
Source: Plutonium | Radiation Protection | US EPA
Q: Is there a medical test to determine exposure to plutonium?
A: There are tests that can reliably measure the amount of plutonium in a urine sample, even at very low levels. Using these measurements, scientists can estimate the total amount of plutonium present in the body. Other tests can measure plutonium in soft tissues (such as body organs) and in feces, bones, and milk. However, these tests are not routinely available in a doctor's office because they require special laboratory equipment.
Source: Plutonium | Radiation Protection | US EPA
Q: What can I do to protect myself and my family from plutonium?
A: Since plutonium levels in the environment are very low, they pose little risk to most people. However, people who live near government weapons production or testing sites may have higher exposure.
Plutonium particles in dust are the greatest concern, because they pose the greatest health risk. People living near government weapons facilities can track radiation monitoring data made available by site personnel. If radiation levels rise, they should follow the radiation protection instructions given by site personnel.
Source: Plutonium | Radiation Protection | US EPA
Q: What is the EPA doing to protect us from plutonium?
A: EPA sets health-based limits on radiation in air, soil, and water. Federal government agencies are required to meet EPA standards the same as commercial industries. Using its authority under the Safe Drinking Water Act, EPA limits the amount of radiation in community water systems by establishing maximum contaminant levels. Maximum Contaminant Levels limit the amount of activity from alpha emitters, like plutonium, to 15 picocuries per liter.
EPA also protects people against exposure from soil and ground water from sites that have been contaminated with plutonium. We set criteria that soil and ground water from the sites must meet before releasing the sites for public use.
Rather than limiting the concentration of plutonium itself, the criteria limit the cancer risk the sites pose. A person's added risk of developing cancer is limited to no more than about 1-in-10,000 and if possible to 1-in-1,000,000, or less. Under the Clean Air Act, EPA limits the dose to humans from radionuclides to 10 millirem from emissions to air.
Additional Information: EPA sets standards for radioactive waste storage and disposal facilities. We can't treat plutonium or other radioactive materials to get rid of their radioactivity. We can only isolate and store them until they decay. The extremely long half-lives of some plutonium radioisotopes make the management of spent nuclear fuel, and wastes from nuclear weapons facilities a difficult problem.
One of EPA's responsibilities has been to develop public health and safety standards for the two major U.S. nuclear waste storage and disposal facilities. The Waste Isolation Pilot Plant in New Mexico stores transuranic wastes. They range from slightly contaminated clothing to barrels of waste so radioactive that it can only be handled with remote control equipment. The proposed Yucca Mountain repository is designed to store high-level radioactive waste and spent nuclear fuel.
EPA also responds to radiation emergencies. Additionally, EPA helps state and local governments during emergencies that involve radioactive materials. We provide guidance on ways to protect people from harmful exposure to radiation. We can also monitor radiation levels in the environment and assess the threat to public health. We also work with international radiation protection organizations to prepare for large scale foreign emergencies such as Chernobyl. EPA also works with law enforcement agencies to develop counter terrorism plans.
Source: Plutonium | Radiation Protection | US EPA
Q: What is the difference between a nuclear bomb and a nuclear reactor?
A: * Nuclear Fission: In nuclear fission, the nuclei of atoms are split, causing energy to be released. The atomic bomb and nuclear reactors work by fission. The element uranium is the main fuel used to undergo nuclear fission to produce energy since it has many favorable properties. Uranium nuclei can be easily split by shooting neutrons at them. Also, once a uranium nucleus is split, multiple neutrons are released which are used to split other uranium nuclei. This phenomenon is known as a chain reaction.
Nuclear Fusion: In nuclear fusion, the nuclei of atoms are joined together, or fused. This happens only under very hot conditions. The Sun, like all other stars, creates heat and light through nuclear fusion. In the Sun, hydrogen nuclei fuse to make helium. The hydrogen bomb, humanity's most powerful and destructive weapon, also works by fusion. The heat required to start the fusion reaction is so great that an atomic bomb is used to provide it. Hydrogen nuclei fuse to form helium and in the process release huge amounts of energy thus producing a huge explosion.
Source: Nuclear Energy
Q: What are the advantages of nuclear energy?
A: o The Earth has limited supplies of coal and oil. Nuclear power plants could still produce electricity after coal and oil become scarce.
o Nuclear power plants need less fuel than ones which burn fossil fuels. One ton of uranium produces more energy than is produced by several million tons of coal or several million barrels of oil.
o Coal and oil burning plants pollute the air. Well-operated nuclear power plants do not release contaminants into the environment.
Source: Nuclear Energy
Q: What are the disadvantages of nuclear energy?
A: * Nuclear explosions produce radiation. The nuclear radiation harms the cells of the body which can make people sick or even kill them. Illness can strike people years after their exposure to nuclear radiation.
* One possible type of reactor disaster is known as a meltdown. In such an accident, the fission reaction goes out of control, leading to a nuclear explosion and the emission of great amounts of radiation.
o In 1979, the cooling system failed at the Three Mile Island nuclear reactor near Harrisburg, Pennsylvania. Radiation leaked, forcing tens of thousands of people to flee. The problem was solved minutes before a total meltdown would have occurred. Fortunately, there were no deaths.
o In 1986, a much worse disaster struck Russia's Chernobyl nuclear power plant. In this incident, a large amount of radiation escaped from the reactor. Hundreds of thousands of people were exposed to the radiation. Several dozen died within a few days. In the years to come, thousands more may die of cancers induced by the radiation.
* Nuclear reactors also have waste disposal problems. Reactors produce nuclear waste products which emit dangerous radiation. Because they could kill people who touch them, they cannot be thrown away like ordinary garbage. Currently, many nuclear wastes are stored in special cooling pools at the nuclear reactors.
o The United States plans to move its nuclear waste to a remote underground dump by the year 2010.
o In 1957, at a dump site in Russia's Ural Mountains, several hundred miles from Moscow, buried nuclear wastes mysteriously exploded, killing dozens of people.
* Nuclear reactors only last for about forty to fifty years.
Source: Nuclear Energy
Q: How does a nuclear reactor work?
A: Most nuclear reactors, including those at Japan's Fukushima Daiichi generating station, are essentially high-tech kettles that efficiently boil water to produce electricity. They rely on harnessing nuclear fission—the splitting of an atom into two smaller atoms, which also yields heat and sends neutrons flying. If another atom absorbs one of those neutrons, the atom becomes unstable and undergoes fission itself, releasing more heat and more neutrons. The chain reaction becomes self-sustaining, producing a steady supply of heat to boil water, drive steam turbines and thereby generate electricity.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: How much electricity does nuclear power provide in Japan and elsewhere?
A: With 54 nuclear reactors generating 280 billion kilowatt-hours annually, Japan is the world's third-largest producer of nuclear power, after the U.S. and France, according to data from the International Atomic Energy Agency. The Fukushima Daiichi station, which has been hit hard by the March 11 earthquake, houses six of those reactors, all of which came online in the 1970s.
Worldwide, nuclear energy accounts for about 15 percent of electricity generation; Japan gets nearly 30 percent of its electricity from its nuclear plants. The U.S. produces more nuclear power overall, but nuclear constitutes a smaller share of its energy portfolio. About 20 percent of U.S. electricity comes from nuclear power plants, making it the third-largest source of electricity in the country after coal (45 percent) and natural gas (23 percent).
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: What fuels a nuclear reactor?
A: Most nuclear reactors use uranium fuel that has been "enriched" in uranium 235, an isotope of uranium that fissions readily. (Isotopes are variants of elements with different atomic masses.) Uranium 238 is much more common in nature than uranium 235 but does not fission well, so fuel manufacturers boost the uranium 235 content to a few percent, which is enough to maintain a continuous fission reaction and generate electricity. Enriched uranium is manufactured into fuel rods that are encased in metal cladding made of alloys such as zirconium.
Reactor No. 3 at the Fukushima Daiichi station runs on so-called mixed oxide (MOX) fuel, in which uranium is mixed with other fissile materials such as plutonium from spent reactor fuel or from decommissioned nuclear weapons.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: How do you turn off a nuclear reaction?
A: Sustained nuclear fission reactions rely on the passing of neutrons from one atom to another—the neutrons released in one atom's fissioning trigger the fissioning of the next atom. The way to cut off a fission chain reaction, then, is to intercept the neutrons. Nuclear reactors utilize control rods made from elements such as cadmium, boron or hafnium, all of which are efficient neutron absorbers. When the reactor malfunctions or when operators need to shut off the reactor for any other reason technicians can remotely plunge control rods into the reactor core to soak up neutrons and shut down the nuclear reaction.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q:
Can a reactor melt down once the nuclear reaction is stopped?
A: Even after the control rods have done their job and arrested the fission reaction the fuel rods retain a great deal of heat. What is more, the uranium atoms that have already split in two produce radioactive by-products that themselves give off a great deal of heat. So the reactor core continues to produce heat in the absence of fissioning.
If the rest of the reactor is operating normally, pumps will continue to circulate coolant (usually water) to carry away the reactor core's heat. In Japan the March 11 earthquake and tsunami caused blackouts that cut off the externally sourced AC power for the reactors' cooling system. According to published reports, backup diesel generators at the power plant failed shortly thereafter, leaving the reactors uncooled and in serious danger of overheating.
Without a steady coolant supply, a hot reactor core will continuously boil off the water surrounding it until the fuel is no longer immersed. If fuel rods remain uncovered, they may begin to melt, and hot, radioactive fuel can pool at the bottom of the vessel containing the reactor. In a worst-case meltdown scenario the puddle of hot fuel could melt through the steel containment vessel and through subsequent barriers meant to contain the nuclear material, exposing massive quantities of radioactivity to the outside world.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: How can a meltdown be averted?
A: The Japanese plant's operators have made a number of attempts to cool the reactors, including pumping seawater into the reactor core to replenish the dwindling cooling fluid. The Tokyo Electric Power Company has also injected boric acid, an absorber of neutrons, into the reactors.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q:
How does this incident compare with Chernobyl or Three Mile Island?
A: At present, three of the reactors at Fukushima Daiichi station are seriously crippled. Units 1 and 3 have experienced explosions that destroyed exterior walls, apparently from buildups of hydrogen gas produced by the zirconium in the fuel rods reacting with coolant water at extremely high temperatures—but the interior containment vessels there thus far seem to be intact. A third explosion was reported March 15 at reactor No. 2, and the situation there appears direr. Pressure in the suppression pool—a doughnut-shaped water vessel below the reactor—dropped after the explosion, indicating that the containment vessel had been compromised.
In reactor Nos. 1, 2 and 3 water levels dropped enough to leave the fuel assemblies temporarily uncovered; those fuel rods are presumed to have suffered damage. And a fire at a pool storing spent fuel rods at dormant reactor No. 4 is posing additional hazards to the few workers remaining at the site.
Japanese officials initially rated the incident a level 4, an "accident with local consequences," on the seven-tier International Nuclear and Radiological Event Scale (INES), but Princeton University physicist Frank von Hippel told The New York Times that the Fukushima Daiichi situation is "way past Three Mile Island already." Three Mile Island, the highest-profile U.S. nuclear accident, was classified level 5—an "accident with wider consequences".
At that Pennsylvania nuclear station in 1979 a cooling malfunction combined with worker error led to a partial meltdown—about half of the reactor core melted and formed a radioactive puddle at the bottom of the steel pressure vessel. The vessel remained intact, but some radiation did escape from the plant into the surrounding environment.
The 1986 Chernobyl accident was far more devastating; it rates as a 7, or a "major accident," on the INES scale. In Ukraine, then part of the Soviet Union, a power surge caused an explosion in one of the plant's reactors, releasing huge doses of radioactive fallout into the air. Two plant workers died within hours, according to the U.S. Nuclear Regulatory Commission; 28 more died in the following months from radiation poisoning. The fallout from Chernobyl was widespread, and the health effects of the disaster are difficult to quantify. A report from the United Nations Scientific Committee on the Effects of Atomic Radiation found that 6,000 individuals who were under the age of 18 in Ukraine, Belarus or Russia at the time of the disaster had by 2006 contracted thyroid cancer, "a substantial fraction" of whom likely contracted the disease due to radiation exposure.
Source: What Happens During a Nuclear Meltdown?: Scientific American
Q: How is a nuclear plant decommissioned?
A: Because the answer to this is actually quite lengthy, a full explanation of the process can be found here: NRC: Fact Sheet on Decommissioning Nuclear Power Plants
That is all I have time to answer but if anyone here has a question that can be answered or has an answer to share to a question please post or if you have a question and an answer that you think should be shared, please post it as well.
I am not trying to sway anyone from nuclear power has I understand it has it's advantages as well as disadvantages, but my hope is that with a little information sharing maybe we can have a better understanding of what is happening in Japan and have a lesser 'freak out' reaction.
I apologize for the lengthy post, but when it comes to nuclear energy and it's processes, there's seldom a short explanation.
Have a good day,
-Dix
