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How does nuclear power affect the environment?
What are nuclear reactors?
What are thermal reactors?
What does nuclear fuel look like?
How does a nuclear power plant work?
Can a nuclear plant explode?

What are nuclear reactors?

Reactors use fission to make electricity rather than burn fossil fuels. A nuclear power plant generates electricity using a "reactor," which is a device designed to use the fission process (splitting of atoms) to turn a small amount of mass into energy in a controlled way. Each fission produces energy, neutrons, and waste fission products.

The energy from the fission reaction is removed from the reactor by a coolant to produce steam to drive the turbines of the electric generators. Thus, in a nuclear power plant, fission of nuclear fuel plays the same role as burning of coal, natural gas, or oil plays in fossil fuel power plants. The neutrons cause more fission reactions. There are two types of reactors: thermal spectrum and fast-spectrum, or simply "thermal" or "fast" for short. The difference has to do with the energy level of the neutrons. The Global Nuclear Energy Partnership includes both.

What are thermal reactors?

In a thermal reactor, the neutrons created by fission are slowed down, or moderated, before they cause more fission reactions. Thermal reactors typically use a special type of uranium, called "enriched" in the isotope uranium-235 and certain isotopes of the transuranic elements, called "fissile." Virtually all of the world's 441 operating nuclear power plants are thermal reactors. Most of these are Light Water Reactors (LWRs), which use water to cool the reactor and to moderate (slow-down) neutrons. The two LWR types, boiling water reactors (BWRs) and pressurized water reactors (PWRs), result from early U.S. reactor development programs. LWRs dominate world nuclear energy because their technology is well proven and they have favorable economics compared to other options currently available.

What does nuclear fuel look like?

Nuclear fuel is a solid material like coal or wood. It is not a liquid or a gas like oil or propane. For U.S. nuclear power plants, uranium oxide fuel is made into pellets. The pellets are stacked into long tubes, typically made of an alloy of zirconium metal, to form fuel rods. The fuel rods are bundled together and structurally reinforced to form a fuel assembly. These assemblies are installed in a nuclear reactor. The size and form of a nuclear fuel assembly depends on the type of reactor in which it will be used. There are typically hundreds of fuel assemblies in a single nuclear power plant. How does a nuclear power plant work? Power plants, whether they are coal, gas, oil or nuclear, use steam to make electricity. They operate like a giant tea kettle, turning water into steam which spins giant turbines that power generators to make electricity. The primary difference between fossil and nuclear power plants is that nuclear plants use uranium as the fuel to produce steam instead of burning fossil fuels.

In a nuclear power plant reactor, water is heated by a process called nuclear fission.

* Uranium atoms are split when they are struck by neutrons.
* When the atoms split, they release heat, along with two or three more neutrons.
* These neutrons then strike other uranium atoms, again causing the atoms to split, release heat and again, two or three more neutrons. This is called a chain reaction.

The steam then spins the turbines that are connected to the generators to produce electricity. Can a nuclear plant explode? No, a nuclear explosion cannot occur at commercial nuclear plants.

Fuel for nuclear plant uranium is mined from the earth and then goes through the process of "enrichment." From that process, comes uranium-235 (which makes up approximately 4% of nuclear fuel used at a commercial facility) and uranium-238 (which makes up the other 96% of the fuel). In order to have an explosion, unranuim-235 must make up nearly 100% of the fuel. Scientifically speaking, an explosion at a nuclear facility in the U.S. would counter the laws of physics.

How does nuclear power affect the environment?

Life-Cycle Emissions Analysis

Nuclear power plants do not emit criteria pollutants or greenhouse gases when they generate electricity. The life-cycle emissions from nuclear energy are comparable to other non-emitting sources of electricity like wind, solar and hydropower.

Clean Electricity for Transportation

Research is under way to reduce air emissions from the transportation sector by developing electric vehicles that can run farther and longer between charges. Clean electricity from nuclear plants can make these vehicles truly "clean."

Ecology

Nuclear energy has one of the lowest impacts on the environment of any energy source because it does not emit air pollution, isolates its waste from the environment and requires a relatively small amount of land.

Sustainable Development

Nuclear energy has a vital role to play in providing clean energy for sustainable economic development around the world.

1. Is there a nuclear power plant near where you live? What type is it?
2. Why don't boiling water reactors have steam generators?
3. What is the purpose of a "cooling tower"?
4. What percentage of the electricity in the ______ is produced in nuclear power plants?
5. Name the two types of reactor power plants in operation the ______ What are the basic differences?
What Is Fission? Where Does It Take Place?
Control rods. What are they? How are they used?

The control rods slide up and down in between the fuel assemblies in the reactor core. They control or regulate the speed of the nuclear reaction by absorbing neutrons. Here's how it works: When the control rods absorb neutrons, fewer neutrons hit the uranium atoms thus slowing down the chain reaction.

On the other hand, when the core temperature goes down, the control rods are slowly lifted out of the core, and fewer neutrons are absorbed. Therefore, more neutrons are available to cause fission. This releases more heat energy.

Just as there are different types of houses and cars, there are different types of nuclear power plants that generate electricity. The two basic types being used are the boiling water reactor (BWR) and the pressurized water reactor (PWR). These power plants are often referred to as light water reactors.

Boiling Water Reactor (BWR)

The boiling water reactor operates in essentially the same way as a fossil fuel generating plant. Neither of these types of power plants have a steam generator. Instead, water in the BWR boils inside the pressure vessel and the steam water mixture is produced when very pure water (reactor coolant) moves upward through the core absorbing heat. The water boils and produces steam. When the steam rises to the top of the pressure vessel, water droplets are removed, the steam is sent to the turbine generator to turn the turbine.

Pressurized Water Reactor (PWR)

The pressurized water reactor differs from the BWR in that the steam to run the turbine is produced in a steam generator. Water boils at 212°F or 100°C. If a lid is tightly placed over a pot of boiling water (a pressure cooker), the pressure inside the pot will increase because the steam cannot escape. As the pressure increases, so does the temperature of the water in the pot. In the PWR plant, a pressurizer unit keeps the water that is flowing through the reactor vessel under very high pressure to prevent it from boiling. The hot water then flows into the steam generator where it is converted to steam. The steam passes through the turbine which produces electricity.

Answers to Questions from Transportation of Radioactive Materials Unit Outline:

1. Q: What is the problem with nuclear power plant waste?

A: Some of it is radioactive

2. Q: What three things are involved in transportation of spent fuel assemblies?

A: a. a series of tests to make sure the casks that will be used really work

b. careful loading and inspection for proper installation of the spent fuel cask

c. training of the truck driver on the hazards of radioactive materials, transportation regulations, and emergency procedures.

3. Q: Does the largest percentage of low-level radioactive waste in the U.S. come from nuclear power plants? Where does it come from?

A: No. It comes from hospitals and industry

4. Q: In a test, the contents of a spent fuel cask must remain intact when hit by a train engine traveling at what speed?

A: 80 miles per hour

5. Q: What international organization assigns classifications to all hazardous materials?

A: The United Nations/oic? 6. Q: Name five organizations that develop rules governing transport of radioactive materials.
A: a. Department of Transportation (DOT )
b. Nuclear Regulatory Commission (NRC)
c. Postal Service
d. Department of Energy (DOE)
e. The States
7. Q: How is radioactive material defined for transportation purposes?
A: It is defined as any material which has a specific activity greater than 0.002 microcuries per gram. This definition does not specify a quantity, only a concentration.
8. Q: What are the three basic types of packages used to transport radioactive materials?
A: a. Strong tight containers (designed to survive normal transportation handling)
b. Type A containers (designed to survive normal transportation handling and minor accidents)
c. Type B containers (able to survive severe accidents)
9. Q: Why are labels and markings used on packages containing radioactive materials?
A: Labels are used to visually indicate the type of hazard and the level of hazard contained in the package. Markings are designed to provide an explanation of the contents of a package by using standard terms and codes.
10. Q: What is a carrier? How many classes of carriers are there? What are their names?
A: Vehicles used to transport radioactive materials. There are three classes: common, contract, and private.

Questions

1. What is the problem with nuclear power plant waste?
2. What three things are involved in transportation of spent fuel assemblies?
3. Does the largest percentage of low-level radioactive waste in the _______ come from nuclear power plants? Where does it come from?
4. In a test, the contents of a spent fuel cask must remain intact when hit by a train engine traveling at what speed?
5. What international organization assigns classifications to all hazardous materials?
6. Name five organizations which develop rules governing transport of radioactive materials.
7. How is radioactive material defined for transportation purposes?
8. What are the three basic types of packages used to transport radioactive materials?
9. Why are labels and markings used on packages containing radioactive materials?
10. What is a carrier? How many classes of carriers are there? What are their names?

To make doubly sure that nothing can go wrong, spent fuel casks have been tested under real and possibly extreme accident conditions. For example, in one test a truck carrying a cask crashed into an unyielding cement wall at 85 miles per hour and in another test a cask was broadsided at 100 miles per hour by a 140-ton locomotive pulling three railroad cars. In both instances, the casks did not leak any radioactive waste.

Let's take a close look at how the spent fuel is prepared for shipment. First, the spent fuel assembly from the reactor is placed inside its cask and the cask is sealed. Second, the outside of the cask is cleaned and then measured or surveyed for radioactivity. Third, the cask is loaded onto the truck or train car that will carry it.

However, before shipping can begin the cask must be inspected a second time to make sure that it is properly installed on the vehicle. Finally, the spent fuel cask and the vehicle carrying it must both be labeled.

In addition to all the requirements that casks must meet to be shipped by truck, the truck driver must be trained in the hazards of radioactive materials, transportation regulations, and emergency procedures. The route the truck carrying the cask takes is also given careful consideration to avoid large cities and undesirable road conditions.

Whether high- or low-level wastes are being shipped, how they are packaged is the most important consideration. The three basic types of packages are strong tight containers (STCs), Type A containers, and Type B containers. While the characteristics of STCs are not specified by regulation, types A and B have very specific requirements listed in the Department of Transportation regulations.

An STC is designed to survive normal transportation handling. In essence, if the contained material makes it from point A to point B without being released, the package is classified as being a strong tight container.

A Type A container, on the other hand, is designed to survive normal transportation handling and minor accidents. Type B containers must be able to survive severe accidents.

Fissile materials (spent fuel) that could be involved in a criticality accident also have additional packaging requirements.

Markings on packages, labeling, and placarding on transportation vehicles are also important aspects of the transport of radioactive materials. Markings are designed to provide an explanation of the contents of a package by using standard terms and codes. [Show "Markings"]

Labels are used to visually indicate the type of hazard and the level of hazard contained in a package. Labels rely principally on symbols to indicate the hazard. [Show "Labeling"] Although the package required for transporting radioactive material is based on the activity INSIDE the package, the label required on the package is based on the radiation hazard OUTSIDE the package.

Radioactive material is the only hazardous material which has three possible labels, depending on the relative radiation levels external to the package. Also, labels for radioactive material are the only ones which require the shipper to write some information on the label. The information is a number called the Transport Index (TI), which, in reality, is the highest radiation level at one meter from the surface of the package.

The three labels are commonly called White I, Yellow II, and Yellow III, referring to the color of the label and the roman numeral prominently displayed. A specific label is required if the surface radiation limit and the limit at one meter satisfy the requirements shown on the "Labeling" transparency.

Placards are just bigger labels that are placed on the outside of the vehicle. Unlike labels, there is only one placard and no information need be written on it. [Show "Placarding"] Placards on a vehicle are only required if the vehicle is carrying a package bearing a Yellow III label or is carrying low specific radioactive material.

The outstanding safety record of storing and shipping used fuel is no accident. It is the result of a philosophy that places public safety and environmental protection first, and a practice of controlled handling and packaging of the used fuel so that it cannot harm the workers, the public, or the environment.

Gaseous and liquid radioactive waste, after processing, may be released to the environment. This can result in the exposure of general members of the public. The diagram above shows some of the pathways that could result in the exposure of a member of the public.

Liquid releases could be taken in by the aquatic growth, which could then be consumed by an individual. The water could be used to irrigate crops or processed as drinking water. Also, the individual could receive direct exposure from the release if in the vicinity of the water, such as swimming or sunbathing.

Gaseous releases could result in exposures by being inhaled by the individual. Also, if the individual is the in the vicinity of the release, a direct exposure could be the result.

The transport of solid radioactive waste (radwaste) and fuel also contribute to the exposure of the average individual.

The amount of exposure received due to all of these processes is very small when compared to the average yearly dose received. Also, there are limits on the amount of exposure a member of the public can receive from a nuclear power plant.

Nuclear power plants provide about 17 percent of the world's electricity. Some countries depend more on nuclear power for electricity than others. In France, for instance, about 75 percent of the electricity is generated from nuclear power, according to the International Atomic Energy Agency.

Have you ever wondered how a nuclear power plant works or how safe nuclear power is? In this article, we will examine how a nuclear reactor and a power plant work. We'll explain nuclear fission and give you a view inside a nuclear reactor.

Uranium

Uranium is a fairly common element on Earth, incorporated into the planet during the planet's formation. Uranium is originally formed in stars. Old stars exploded, and the dust from these shattered stars aggregated together to form our planet. Uranium-238 (U-238) has an extremely long half-life (4.5 billion years), and therefore is still present in fairly large quantities. U-238 makes up 99 percent of the uranium on the planet. U-235 makes up about 0.7 percent of the remaining uranium found naturally, while U-234 is even more rare and is formed by the decay of U-238. (Uranium-238 goes through many stages or alpha and beta decay to form a stable isotope of lead, and U-234 is one link in that chain.)

Uranium-235 has an interesting property that makes it useful for both nuclear power production and for nuclear bomb production. U-235 decays naturally, just as U-238 does, by alpha radiation. U-235 also undergoes spontaneous fission a small percentage of the time. However, U-235 is one of the few materials that can undergo induced fission. If a free neutron runs into a U-235 nucleus, the nucleus will absorb the neutron without hesitation, become unstable and split immediately.

uranium-235 nucleus with a neutron approaching from the top. As soon as the nucleus captures the neutron, it splits into two lighter atoms and throws off two or three new neutrons (the number of ejected neutrons depends on how the U-235 atom happens to split). The two new atoms then emit gamma radiation as they settle into their new states. There are three things about this induced fission process that make it especially interesting:

* The probability of a U-235 atom capturing a neutron as it passes by is fairly high. In a reactor working properly (known as the critical state), one neutron ejected from each fission causes another fission to occur.

* The process of capturing the neutron and splitting happens very quickly, on the order of picoseconds (1x10-12 seconds).

* An incredible amount of energy is released, in the form of heat and gamma radiation, when a single atom splits. The two atoms that result from the fission later release beta radiation and gamma radiation of their own as well. The energy released by a single fission comes from the fact that the fission products and the neutrons, together, weigh less than the original U-235 atom. The difference in weight is converted directly to energy at a rate governed by the equation E = mc2.

Something on the order of 200 MeV (million electron volts) is released by the decay of one U-235 atom (if you would like to convert that into something useful, consider that 1 eV is equal to 1.602 x 10-12 ergs, 1 x 107 ergs is equal to 1 joule, 1 joule equals 1 watt-second, and 1 BTU equals 1,055 joules). That may not seem like much, but there are a lot of uranium atoms in a pound of uranium. So many, in fact, that a pound of highly enriched uranium as used to power a nuclear submarine or nuclear aircraft carrier is equal to something on the order of a million gallons of gasoline. When you consider that a pound of uranium is smaller than a baseball, and a million gallons of gasoline would fill a cube 50 feet per side (50 feet is as tall as a five-story building), you can get an idea of the amount of energy available in just a little bit of U-235.

In order for these properties of U-235 to work, a sample of uranium must be enriched so that it contains 2 percent to 3 percent or more of uranium-235. Three-percent enrichment is sufficient for use in a civilian nuclear reactor used for power generation. Weapons-grade uranium is composed of 90-percent or more U-235.

Inside a Nuclear Power Plant

To build a nuclear reactor, what you need is some mildly enriched uranium. Typically, the uranium is formed into pellets with approximately the same diameter as a dime and a length of an inch or so. The pellets are arranged into long rods, and the rods are collected together into bundles. The bundles are then typically submerged in water inside a pressure vessel. The water acts as a coolant. In order for the reactor to work, the bundle, submerged in water, must be slightly supercritical. That means that, left to its own devices, the uranium would eventually overheat and melt.

To prevent this, control rods made of a material that absorbs neutrons are inserted into the bundle using a mechanism that can raise or lower the control rods. Raising and lowering the control rods allow operators to control the rate of the nuclear reaction. When an operator wants the uranium core to produce more heat, the rods are raised out of the uranium bundle. To create less heat, the rods are lowered into the uranium bundle. The rods can also be lowered completely into the uranium bundle to shut the reactor down in the case of an accident or to change the fuel.

The uranium bundle acts as an extremely high-energy source of heat. It heats the water and turns it to steam. The steam drives a steam turbine, which spins a generator to produce power. In some reactors, the steam from the reactor goes through a secondary, intermediate heat exchanger to convert another loop of water to steam, which drives the turbine. The advantage to this design is that the radioactive water/steam never contacts the turbine. Also, in some reactors, the coolant fluid in contact with the reactor core is gas (carbon dioxide) or liquid metal (sodium, potassium); these types of reactors allow the core to be operated at higher temperatures.

Outside a Nuclear Power Plant

Once you get past the reactor itself, there is very little difference between a nuclear power plant and a coal-fired or oil-fired power plant except for the source of the heat used to create steam.

Electricity for homes and businesses comes from this generator at the Shearon Harris plant. It produces 870 megawatts.

Pipes carry steam to power the generator at the power plant.

The reactor's pressure vessel is typically housed inside a concrete liner that acts as a radiation shield. That liner is housed within a much larger steel containment vessel. This vessel contains the reactor core as well the hardware (cranes, etc.) that allows workers at the plant to refuel and maintain the reactor. The steel containment vessel is intended to prevent leakage of any radioactive gases or fluids from the plant.

Finally, the containment vessel is protected by an outer concrete building that is strong enough to survive such things as crashing jet airliners. These secondary containment structures are necessary to prevent the escape of radiation/radioactive steam in the event of an accident like the one at Three Mile Island. The absence of secondary containment structures in Russian nuclear power plants allowed radioactive material to escape in an accident at Chernobyl.

Workers in the control room at the nuclear power plant can keep an eye on the nuclear reactor and take action if something goes wrong.

Uranium-235 is not the only possible fuel for a power plant. Another fissionable material is plutonium-239. Plutonium-239 can be created easily by bombarding U-238 with neutrons -- something that happens all the time in a nuclear reactor.

Subcriticality, Criticality and Supercriticality

When a U-235 atom splits, it gives off two or three neutrons (depending on the way the atom splits). If there are no other U-235 atoms in the area, then those free neutrons fly off into space as neutron rays. If the U-235 atom is part of a mass of uranium -- so there are other U-235 atoms nearby -- then one of three things happens:

* If, on average, exactly one of the free neutrons from each fission hits another U-235 nucleus and causes it to split, then the mass of uranium is said to be critical. The mass will exist at a stable temperature. A nuclear reactor must be maintained in a critical state.

* If, on average, less than one of the free neutrons hits another U-235 atom, then the mass is subcritical. Eventually, induced fission will end in the mass.

* If, on average, more than one of the free neutrons hits another U-235 atom, then the mass is supercritical. It will heat up.

For a nuclear bomb, the bomb's designer wants the mass of uranium to be very supercritical so that all of the U-235 atoms in the mass split in a microsecond. In a nuclear reactor, the reactor core needs to be slightly supercritical so that plant operators can raise and lower the temperature of the reactor. The control rods give the operators a way to absorb free neutrons so the reactor can be maintained at a critical level.

The amount of uranium-235 in the mass (the level of enrichment) and the shape of the mass control the criticality of the sample. You can imagine that if the shape of the mass is a very thin sheet, most of the free neutrons will fly off into space rather than hitting other U-235 atoms. A sphere is the optimal shape. The amount of uranium-235 that you must collect together in a sphere to get a critical reaction is about 2 pounds (0.9 kg). This amount is therefore referred to as the critical mass. For plutonium-239, the critical mass is about 10 ounces (283 grams).

Problems with Nuclear Power Plants

Well-constructed nuclear power plants have an important advantage when it comes to electrical power generation -- they are extremely clean. Compared with a coal-fired power plant, nuclear power plants are a dream come true from an environmental standpoint. A coal-fired power plant actually releases more radioactivity into the atmosphere than a properly functioning nuclear power plant. Coal-fired plants also release tons of carbon, sulfur and other elements into the atmosphere (see this page about coal pollution for details).

Unfortunately, there are significant problems with nuclear power plants:

* Mining and purifying uranium has not, historically, been a very clean process.

* Improperly functioning nuclear power plants can create big problems. The Chernobyl disaster is a good recent example. Chernobyl was poorly designed and improperly operated, but it dramatically shows the worst-case scenario. Chernobyl scattered tons of radioactive dust into the atmosphere.

* Spent fuel from nuclear power plants is toxic for centuries, and, as yet, there is no safe, permanent storage facility for it.

* Transporting nuclear fuel to and from plants poses some risk.

What's a uranium centrifuge?

What is an atomic clock and how does it work?

Q. What are the details on nuclear energy?

A. It is somewhat complicated and depends on facts about nuclear physics and nuclear engineering.

1. Nuclear power can come from the fission of uranium, plutonium or thorium or the fusion of hydrogen into helium. Today it is almost all uranium. The basic energy fact is that the fission of an atom of uranium produces 10 million times the energy produced by the combustion of an atom of carbon from coal.

2. Natural uranium is almost entirely a mixture of two isotopes, U-235 and U-238. U-235 can fission in a reactor, and U-238 can't to a significant extent. Natural uranium is 99.3 percent U-238 and 0.7 percent U-235.

3. Most nuclear power plants today use enriched uranium in which the concentration of U-235 is increased from 0.7 percent U-235 to (nowadays) about 4 to 5 percent U-235. This is done in an expensive separation plant of which there are several kinds. The U-238 "tails" are left over for eventual use in "breeder reactors". The Canadian CANDU reactors don't require enriched fuel, but since they use expensive heavy water instead of ordinary water, their energy cost is about the same.

4. In 1993 there were 109 licensed power reactors in the U.S. and about 400 in the world. They generated about 20 percent of the U.S. electricity. (There are also a large number of naval power reactors.) The expansion of nuclear power depends substantially on politics, and this politics has come out differently in different countries. Very likely, after some time, the countries whose policies turn out badly will copy the countries whose policies turn out well. There are only 104 operating reactors in 2007 and the percent of electricity that was nuclear was about 17.

5. In 2007 five applications were made to the Nuclear Regulatory Commission to construct and operate new nuclear power plants.

6. For how long will nuclear power be available? Present reactors that use only the U-235 in natural uranium are very likely good for some hundreds of years. Bernard Cohen has shown that with breeder reactors, we can have plenty of energy for some billions of year.

Cohen's argument is based on using uranium from sea water. Other people have pointed out that there is more energy in the uranium impurity in coal than could come from burning the coal. There is also plenty of uranium in granite. None of these sources is likely to be used in the next thousand years, because there is plenty of much more cheaply extracted uranium in conventional uranium ores.

7. A power reactor contains a core with a large number of fuel rods. Each rod is full of pellets of uranium oxide. An atom of U-235 fissions when it absorbs a neutron. The fission produces two fission fragments and other particles that fly off at high velocity. When they stop the kinetic energy is converted to heat - 10 million times as much heat as is produced by burning an atom of the carbon in coal. See the supplement for some interesting nuclear details.

8. Besides the fission fragments several neutrons are produced. Most of these neutrons are absorbed by something other than U-235, but in the steady-state operation of the reactor exactly one is absorbed by another U-235 atom causing another fission. The steam withdrawn and run through the turbines controls the power level of the reactor. Control rods that absorb neutrons can also be moved in and out to control the nuclear reaction. The power level that can be used is limited to avoid letting the fuel rods get too hot.

9. The heat from the fuel rods is absorbed by water which is used to generate steam to drive the turbines that generate the electricity.

10. A large plant generates about a million kilowatts of electricity - some more, some less.

11. After about two years, enough of the U-235 has been converted to fission products and the fission products have built up enough so that the fuel rods must be removed and replaced by new ones.

12. What to do with the spent fuel rods is what causes most of the fuss concerning nuclear power.

Q. What about the plutonium?

A. Besides fission products, spent fuel rods contain some plutonium produced by the U-238 in the reactor absorbing a neutron. This plutonium and leftover uranium can be separated in a reprocessing plant and used as reactor fuel. The Japanese had their spent fuel rods reprocessed in Europe and shipped the plutonium back home for use in reactors. This is what Greenpeace was fussing about.

Q. How much plutonium is produced?

A. In terms of nuclear fuel, about 1/4 as much as the U-235 that was in the fuel rods in the first place. Thus running a reactor for four years produces enough plutonium to run it for one more year provided the plutonium is extracted and put into new fuel rods. Newer designs with higher "burnup ratios" get more of their energy from plutonium.

Q. What about nuclear waste?

A. After the fuel has been in the reactor for about 18 months, much of the uranium has already fissioned and a considerable quantity of fission products have built up in the fuel. The reactor is then refueled by replacing about 1/3 of the fuel rods. This generally takes one or two months. {2002 note: Entergy Nuclear, an enthusiastic buyer and operator of American nuclear power plants has been reducing this time for their plants. They refueled their River Bend plant in Louisiana in 17 days and expect to reduce their average refueling outage time to two-three weeks.] Canadian CANDU reactors replace fuel continuously.

When fuel rods are removed from the reactor they contain large quantities of highly radioactive fission products and are generating heat at a high rate. They are then put in a large tank of water about the size of a swimming pool. There they become less radioactive as the more highly radioactive isotopes decay and also generate less and less heat. The longer the spent fuel is stored, the easier it will be to handle, but many reactors have been holding spent fuel so long that their tanks are getting full. They must either send the rods off or build more tanks.

The fuel rods should then be chemically reprocessed. Reprocessing removes any leftover uranium and the plutonium that has been formed. The U.S. shut down its reprocessing plant during the 1970s and hasn't replaced it. European reprocessing plants (Belgium, France, Russia, UK) continue to operate, and the Japanese are building their own - in the meantime sending their spent fuel to Europe for reprocessing. The French plant they use sends their plutonium back to Japan, where the Japanese plan to use it as reactor fuel.

The fission products are then put in a form for long term storage. A large reactor produces about 1.5 tonnes of fission products per year. The fission products are originally in a mixture with other substances, so reprocessing is required to get it down to a 1.5 tonnes. [If the waste is incorporated into a glass, the total weight is 15 tonne. If the density is 3.0 times water, that means the volume of the waste is 0.5 cubic meters, and the volume of the waste glass is about 5 cubic meters. [from Prof. Bernard Cohen] Many schemes for long term storage have been devised, but lawsuits and politics have prevented any of them from being implemented in the United States. Unfortunately, the U.S. is not reprocessing so the volume to be stored is about 10 times larger - still entirely feasible.

The French have decided on a scheme, but I don't know if they have put it into operation. Because the fission products become less radioactive with time, the longer you wait, the easier the task becomes. The Canadians are reviewing a plan for storing waste deep underground in the Pre-Cambrian "Canadian Shield".

The U.S. plan is to store the waste in Nevada in the same area as has been used for underground nuclear tests. This plan is still tied up in long term indecision. A big step forward was taken in 2002 when the President signed a bill to over-rule the objections of the State of Nevada.

Q. Why isn't the U.S. reprocessing?

A. The Carter Administration decided not to reprocess nominally on the grounds that if other countries could be persuaded not to reprocess, the likelihood of nuclear proliferation would be reduced. So far as I know, not one other country has been persuaded, because the economic advantages of reprocessing are so great. The Reagan and Bush Administrations wanted to reprocess, but it would have been politically expensive so they temporized.

Q. What if you don't reprocess?

A. You lose the economic benefit of the plutonium, the spent fuel remains radioactive longer and has to be better guarded, because it contains plutonium. However, there is plenty of uranium for now, so it may not be economic to reprocess at present provided the spent fuel remains available for later reprocessing.

Q. What about breeder reactors?

A. If the reactor design is much more economical of neutrons, enough U-238 can be converted to plutonium so that after a fuel cycle there is more fissionable material than there was in the original fuel rods in the reactor. Such a design is called a breeder reactor. Breeder reactors essentially use U-238 as fuel, and there is 140 times as much of it as there is U-235. The billion year estimates for fuel resources depend on breeder reactors. The French built two of them, the U.S. has a small one, the British built one, the Russians built one and the Japanese are building one.

Breeder reactors seem to be a resource rather than a reserve. They are more expensive than present reactors and maybe will wait for large scale deployment until uranium gets more expensive. This is unlikely to be soon, because large uranium reserves have been discovered in recent years.

Q. What about the Integral Fast Reactor (IFR)?

This was a breeder reactor with reprocessing on site, so no plutonium ever became externally available. It was hoped that it would address the proliferation concerns of the anti-nukes, i.e. it was hoped that they would be appeased. However, as soon as the Clinton Administration came to power, its anti-nukes got the IFR cancelled. Appeasement didn't work this time either. The IFR still has its enthusiasts, and maybe it will be revived.

Q. Can a nuclear plant blow up like a bomb?

A. No. A bomb converts a large part of its U-235 or plutonium into fission fragments in about 10^-8 seconds and then flies apart. This depends on the fact that a bomb is a very compact object, so the neutrons don't have far to go to hit another fissionable atom. A power plant is much too big to convert an important part of its fissionable material before it has generated enough heat to fly apart. This fact is based on the fundamental physics of how fast fission neutrons travel. Therefore, it doesn't depend on the particular design of the plant.

What are the materials needed to make an "atom bomb?"

Uranium-238 and plutonium-239.

Aren't these materials radioactive?

Highly so. Anybody who attempts to use these materials is endangering his/her life.

Q. Can a nuclear plant blow up to a lesser extent?

A. Yes, if it is sufficiently badly designed and operated. The Chernobyl plant reached 150 times its normal power level before its water turned to high pressure steam and blew the plant apart, thus extinguishing the nuclear reaction. This only took a few seconds.

Q. How much of a disaster was that?

A. In terms of immediate deaths it was a rather small disaster. 31 people died. Cave-ins in coal mines often kill hundreds.

However, about 20 square miles of land became uninhabitable for a long time. This isn't a lot.

Fall-out from the Chernobyl explosion will contribute an increase to the incidence of cancer all over Europe. How much of an increase is disputed. Since the increase will be very small in proportion to the amount of cancer, we probably won't know from experience.

The largest estimates are in the low thousands which would make Chernobyl a disaster comparable to the Bhopal chemical plant or the Texas City explosion of a shipload of ammonium nitrate or the Halifax disaster during World War I. On the other hand these large estimates are small compared to the number who have died in each of several recent large earthquakes in countries using stone or adobe or sod houses.

It is comparable to the number killed in coal mining accidents in the Soviet Union over the years Chernobyl was operating.

The large estimates depend on the linear hypothesis which is almost certainly wrong but which is used for regulatory purposes because it is so conservative. The estimates are probably too high by a substantial factor, maybe 10, maybe 100.

However, a recent survey indicates a greatly increased rate of thyroid cancer in children (including three deaths)j in Belarus since the accident. I don't know the total number of cases which would permit comparing Chernobyl with other accidents. Here is more on the Chernobyl accident including links to British, Ukrainian and Russian accounts of the accident and its effects.

Q. What about Western nuclear power plants?

A. The Chernobyl accident depended on the specific characteristics of the RBMK reactors, of which the Soviets built 16 before switching to designs more like those used in the rest of the world. (It may be that the North Korean reactors are similar). The relevant features of RBMK reactors include

* "positive void co-efficient of reactivity". This means that if the reactor gets too hot and some of the water turns to steam, the rate of the nuclear reaction increases. In most other power reactors, the void coefficient is negative. If some water boils the reactor tends to stop.

* RBMK reactors don't have containment shells designed to prevent radioactive materials from getting out.

Q. Yes, but perhaps Western reactors have other faults that might make an accident serious.

A. There are three answers.

* The Three Mile Island accident destroyed the reactor, but the core itself remained confined. Radioactive gases were vented, but there is no accepted evidence that this harmed the public.

* Fault trees for possible failures have been generated and studied. However, there could be something not taken into account.

* At the end of 1998 there were 9012 civilian power reactor years of experience throughout the world, and Chernobyl is the only nuclear power plant accident harming the public. The U.S. Navy has been powering ships with nuclear reactors for 50 years and has had no nuclear accidents.

* In 1999 Japanese technicians mixing up fuel for an experimental reactor violated the safety procedures and created a critical mass of uranium which caused an increasing nuclear reaction until the container with the mixture boiled over and stopped the reaction. Three people were hospitalized, two of whom died. The press, especially AFP which is anti-nuclear billed this as the worst nuclear accident since Chernobyl in 1986. Losing two people in 13 years isn't much.

That's good for an energy source.

Q. Are nuclear power plants perfectly safe?

A. No. Nothing is perfectly safe, but they are safe enough to be relied upon as a source of energy.

Q. What about nuclear waste?

A. The waste consists of the fission products. They are highly radioactive at first, but the most radioactive isotopes decay the fastest. (That's what being most radioactive amounts to). About one cubic meter of waste per year is generated by a power plant. It needs to be kept away from people. After 10 years, the fission products are 1,000 times less radioactive, and after 500 years, the fission products will be less radioactive than the uranium ore they are originally derived from. The cubic meter estimate assumes reprocessing, unfortunately not being done in the U.S.

Q. What about diversion of material from power plants to countries wanting to make bombs?

A. Every country wanting to make bombs has succeeded as far as is known. None have used material produced in power reactors. (Plutonium produced in RBMK reactors may have been used in Soviet weapons. The RBMK was designed as a dual-purpose reactor suitable both for power production and bomb production. For this it was necessary to be able to replace fuel rods while the reactor was operating, and this made the reactor too big for a containment structure, and this is what allowed the radioactivity to spread.)

If the fuel rods are kept in the reactor for the two years or so required for economical power generation, much of the Pu-239 atoms produced absorb another neutron and become Pu-240. It is more expensive to separate the Pu-240 from the Pu-239 than to get Pu-239 from a special purpose reactor in which the fuel rods are removed after a short time. The Pu-240 makes the bomb fizzle if there is very much of it. For more details see the article by Myers.

It seems that some of the Russian PU-239 of which samples were sold in Germany was pure enough so that some isotope separation process was probably used after the plutonium was extracted from the fuel rods.

Q. Are the reserves of uranium adequate for the long term?

A. At present, the reserves of uranium that can be profitably sold at at $50 per pound are enough for at least a hundred years. Since the cost of uranium ore is only 0.04 cents per kilowatt-hour, at the 2001 price of $9 per pound, even large increases in ore cost are affordable without increasing the cost of nuclear generated electricity significantly. At somewhat larger prices than uranium now costs it can be extracted from the sea. Thorium, which is three times as abundant as uranium can also be used in reactors.

Here's a note about nuclear power costs from Professor Bernard Cohen of the University of Pittsburgh.

In the very long term, breeder reactors will be used. These get about 100 times as much energy from a kilogram of uranium as do present reactors. This makes the present stock of uranium go much farther. Indeed all the enriched uranium used in nuclear reactors and all the U-235 used in nuclear weapons has been separated from U-238, and the leftover U-238 is still available. If this U-238 were used to generate energy in breeder reactors and the electricity were sold at present prices, the present American stock of depleted uranium would generate $20 trillion worth of electricity. [Doubtless this number has changed one way or the other since the above was first written. I haven't time to keep updating it.]

Q. What about power from nuclear fusion.

A. Since the 1930s it has been understood that the sun gets its energy by combining hydrogen atoms to get helium. It was immediately apparent that if we could use these nuclear reactions we would have energy for billions of years. At first the problems of getting this energy on earth seemed insuperable, because of the millions of degrees of temperature required to get hydrogen atoms to combine.

In the 1950s it was discovered how to do this in hydrogen bombs by using ordinary nuclear fission bombs to set off the fusion of the hydrogen isotopes of deuterium and tritium. Projects were promptly started for doing this under less violent conditions. After 50 years, fusion reactors may be close to getting more fusion energy out of the reaction that has to be put in. Present proposals use deuterium and lithium-6, as do present hydrogen bombs.

Fusion power has the following possible advantages if it can be made to work.

* The fuel supply is potentially larger. However, the uranium supply seems to be large enough.

* Fission products are not produced, although there will be induced radioactivity in the structures of the plants.

* No material useful for bombs is produced.

Q. Are we ever likely to have nuclear powered cars?

Alas, no, if present nuclear physics is all there is to say about the possibility. A nuclear reactor engine that would provide the right amount of energy for a car could be built and would run fine and would require refuelling only every 5 or 10 years. The only problem is that it would kill the driver, the passengers, and perhaps bystanders. Nuclear reactors, as described above, produce neutrons, which are very penetrating particles and give people radiation sickness if the exposure is substantial. (All our bodies are penetrated all the time by small numbers of neutrons.) Power reactors have several feet of concrete shielding between the active part of the reactor and the operators. A big enough vehicle like an aircraft carrier or a big submarine can afford the shielding. In the 1950s some thought that nuclear aircraft were feasible. Maybe they were, but the projects were abandoned.

Q. What are the arguments against nuclear energy?

A. There are many arguments, some related specifically to nuclear energy and others stemming from more general ideas about society. I have labelled the unrelated arguments and made a few comments to be answered more fully later.

1. The problem of disposal of nuclear wastes hasn't been solved. There are several good technical solutions, but the political problem hasn't been solved in the U.S. [2003: Now the political problem has been solved, but lawsuits will be filed and may hold up the solution for a while. 2010 is now predicted as the time when waste will start being stored in Nevada.]

2. Nuclear energy is uneconomical compared to other sources of energy. It is doing ok.

3. The energy required to build nuclear plants, operate them, and mine and process the uranium may be so large as to cause a net energy deficit. Here's a thorough Energy Analysis of Power Systems including nuclear energy and its competitors. The basic fact about nuclear energy is that the input energy is 4.8 percent of output energy if gaseous diffusion is used to enrich uranium and 1.7 percent if the newer centrifuge technology is used. Another way of looking at the same facts is that if gaseous diffusion is used for enrichment, the energy invested in building the plant is paid back in 5 months, whereas if centrifuges are used the payback time is 4 months.

4. It is bad for humanity to have plenty of energy. - unrelated .

5. Nuclear reactors produce plutonium, and plutonium is terrible because it can be used to make bombs. Safeguards are indeed needed.

* Plutonium is the most poisonous substance known. No it isn't.

* Plutonium symbolizes nuclear war. - unrelated .

6. Nuclear reactors are likely to have accidents with severe consequences for humanity. See above.

7. Radiation from operating nuclear reactors and other activities involved in nuclear energy is dangerous.

8. Energy should be generated locally, even by individual households, rather than by centralized power stations. - unrelated

9. The risk to an individual of harm from a nuclear accident is an involuntary risk, as compared to the much larger risk from driving a car, which is voluntary.

This comparison ignores much larger involuntary risks, e.g. the risk of emphysema from coal burning, the risk of an airplane hitting your house, and the risk of a flood when a dam breaks. Each of these risks is larger and comes from a human activity. There are other large risks, such as that of a flu epidemic, which are only partly caused by human activities - such as allowing international travel or having pre-schools where children transmit infections to each other.

The decision to incur such involuntary risks is a collective decision, made in accordance with laws.

Here are some answers to all the arguments listed (even the ones I have labelled unrelated ) and any more that people suggest. Some will be answered by reference to the literature.

Q. What is likely to happen with nuclear energy?

A. The countries that need it the most will continue to use it. France gets 77 percent of its electricity from nuclear reactors, the rest being hydroelectric. Japan is close to 30 percent and increasing steadily. Japan has little domestic coal and no oil. We have plenty of coal and natural gas, can afford to import more than half of our oil. Therefore, we can afford delays caused by controversy unless we are zapped by the greenhouse effect. However, the counterculture generation is passing through the peak of its political power, and the next generations seem to be more rational about nuclear energy and many other issues.

Therefore, the U.S. is likely to resume building reactors before being driven to it by other countries getting economic advantages.

Here are the references related to nuclear energy.

Q. Is the use of nuclear absolutely essential to the sustainability of progress?

A. Probably not. Solar energy would also work, but at considerably greater cost if relied upon for most of the world's energy.

Q. Then what about giving up on nuclear energy because of the danger of nuclear war?

A. Giving up on nuclear energy is unlikely to reduce the danger of nuclear wars. In fact it is likely to increase the danger, because of the advantage it would give to whoever would first reintroduce nuclear weapons. Also the poorer world that would result from the abandonment of nuclear energy would be more likely to have wars.

Q. What if all energy generated were nuclear?

A. A preliminary page discusses this eventuality. When I get a chance to look up more relevant facts, it will be improved.

Q. What is the current state of nuclear energy in the U.S.?

A. Operating nuclear plants generate 20 percent of U.S. electricity, but no new plants have been ordered in a long time. The Electric Power Research Institute (EPRI) asked utility executives what would make them start ordering nuclear plants again. The 1994 December article Reopening the Nuclear Option by John Douglas in the EPRI Journal gives their answers. It looks difficult but not impossible. "The plants must be simpler and have higher design margins and enhanced safety features; they must be economically competitive with other forms of generation; they must be standardized; and they must be prelicensed by the NRC."

All this presumes that fossil fuels will continue to be available and not restricted too much by worries about global warming. If this changes, the requirements for new nuclear power plants in the U.S. will be greater. Remember that the U.S. is a special case politically and in the availability of natural gas and that other countries are still building nuclear plants.

Let me again remind the reader that all I really need to accomplish with this page is to show that lack of energy will not stop material progress. I do not need to show that nuclear energy is the best short term option, although it probably is.

Q. All this is well and good, but isn't the opposition to nuclear power strong enough to prevent its use?

A. Not when and if refusing to build nuclear plants results in a substantial loss of a country's standard of living. Politicians seem to believe that mentioning nuclear energy is political poison at present. They may be right or it may be just one more superstition prevalent among politicians and their consultants. Recently a taboo against mentioning nuclear energy has developed among scientists - especially those specializing in energy. None of the articles in the recent special issue of Science devoted to energy mentioned nuclear energy - pro or con - even though nuclear energy provides 17 percent of American electricity. Perhaps energy scientists feel that mentioning nuclear energy will have an adverse effect on their grants. Perhaps there is some other reason. To some extent "hydrogen" in the energy literature is a code word for nuclear energy, since many articles promoting hydrogen don't say how else it can be generated economically in the quantities required to run an economy. Recent waves of ideology are strongly involved.

References

There will be references to the pro-nuclear popular literature, the anti-nuclear popular literature and the technical literature.

Q. Is nuclear energy sustainable?

A. Yes. In the short term, probably the next hundred years, there is so much uranium that no-one can profitably prospect for more. In the medium term breeder reactors will extend the energy obtained per kilogram of uranium by a factor of about 100.

Take a look at this.
Nuclear Power Plant

ILLINOIS

To be updated

Nuclear Power Plant, Illinois

Braidwood Generating Station

Byron Generating Station

Clinton Power Station

Dresden Generating Station

LaSalle County Generating Station

Limerick Generating Station

Oyster Creek Generating Station

Peach Bottom Atomic Power Station

Quad Cities Generating Station

Three Mile Island

Zion Generating Station

Description: The Braidwood Station is located in Will County in northeastern Illinois. It serves Chicago and northern Illinois. Braidwood's recent up rates make it the largest nuclear plant in the State. The three largest Illinois' plants, however, are nearly equal (LaSalle is only 2 net megawatts smaller than Braidwood and Byron is only 4 net megawatts less in capacity than LaSalle).The plant has a workforce of 800 employees and contractors with an annual payroll of over $60 million.

Description: The Byron plant contains two light water reactors. The Byron site covers approximately 1,782 acres in a location about 20 miles from Byron in northern Illinois. The twin cooling towers are 495 feet in height. Construction costs total approximately $4.5 billion. The workforce consists of 690 employees and 100 permanent contractors. The payroll is about $60 million.

To be updated

With nuclear power technology today, the typical plant built in the rest of the world is about 1000 Megawatts or even slightly bigger, often about 1200 Megawatts of power. The average demand/generation in all of Kashmir (J&K) is about 1300 megawatts.

Hydro Electric Power potential Kashmir.
22, 000 megawatts.

Q) Is there a nuclear power plant near where you live? What type is it?
Q) Why don't boiling water reactors have steam generators?
Q) What is the purpose of a "cooling tower"?
Q) What percentage of the electricity in the ______ is produced in nuclear power plants?
Q) Name the two types of reactor power plants in operation the ______ What are the basic differences?
Q) What Is Fission? Where Does It Take Place?
Q) What is the problem with nuclear power plant waste?
Q) What three things are involved in transportation of spent fuel assemblies?
Q) In a test, the contents of a spent fuel cask must remain intact when hit by a train engine traveling at what speed?
Q) What international organization assigns classifications to all hazardous materials?
Q) Name five organizations that develop rules governing transport of radioactive materials.
Q) How is radioactive material defined for transportation purposes?
Q) What are the three basic types of packages used to transport radioactive materials?
Q) Why are labels and markings used on packages containing radioactive materials?
Q) What is a carrier? How many classes of carriers are there? What are their names?
Q) What is the problem with nuclear power plant waste?
Q) What three things are involved in transportation of spent fuel assemblies?
Q) Does the largest percentage of low-level radioactive waste in the _______ come from nuclear power plants? Where does it come from?
Q) In a test, the contents of a spent fuel cask must remain intact when hit by a train engine traveling at what speed?
Q) What international organization assigns classifications to all hazardous materials?
Q) What are the details on nuclear energy?
Q) What about the plutonium?
Q) How much plutonium is produced?
Q) What about nuclear waste?
Q) What if you don't reprocess?
Q) What about breeder reactors?
Q) What about the Integral Fast Reactor (IFR)?
Q) Can a nuclear plant blow up like a bomb?
Q) What are the materials needed to make an "atom bomb?"
Q) Are nuclear power plants perfectly safe?
Q) What about diversion of material from power plants to Western White Racist wanting to make bombs?
Q) Are the reserves of uranium adequate for the long term?
Q) What about power from nuclear fusion.
Q) Are we ever likely to have nuclear powered cars?
Q) What is likely to happen with nuclear energy?
Q) Is nuclear energy sustainable?



Q) Name six organizations which develop rules governing transport of radioactive materials.
Q) How is radioactive material defined for transportation purposes?
Q) What are the three basic types of packages used to transport radioactive materials?
Q) Why are labels and markings used on packages containing radioactive materials?
Q) What is a carrier? How many classes of carriers are there? What are their names?
Q) What's a uranium centrifuge?
Q) What is an atomic clock and how does it work?
Q) What is the method of payment?

http://asolutionforpollution.com/solution/faq.html

http://www.howstuffworks.com/nuclear-power.htm

http://www.animatedsoftware.com/environm/no_nukes/nukelist1.htm

http://www.fema.gov/hazard/nuclear/index.shtm