Nuclear power generation has been very controversial.?

Question

Nuclear power generation has been very controversial. Cite the advantages of using nuclear power plants. Research the use of nuclear power for electricity production in the rest of the worl. Compare this to the situation in the USA. Based on what you learn in your research, predict whether nuclear power will made a "comeback" in the USA.

Answer 1

One of the major requirements for sustaining human progress is an adequate source of energy. The current largest sources of energy are the combustion of coal, oil and natural gas. These are discussed in the main page on energy. They will last quite a while but will probably run out or become harmful in tens to hundreds of years. Solar energy will also work but is not much developed yet except for special applications because of its high cost. This high cost as a main source, e.g. for central station electricity, is likely to continue, and nuclear energy is likely to remain cheaper. A major advantage of nuclear energy (and also of solar energy) is that it doesn't put carbon dioxide (CO2) into the atmosphere. How much of an advantage depends on how bad the CO2 problem turns out to be.
Q. What are the details on nuclear energy?

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


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.

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.

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.

In 1993 there were 109 licensed power reactors in the U.S. and about 400 in the world. They generate 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.

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.

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.

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.

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

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

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.

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.

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.

Here's another page on the integral fast reactor..

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.

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.

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.

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. The Princeton Plasma Physics Laboratory has an FAQ about magnetic and inertial fusion. The US Department of Energy has a Fusion energy research site, and there is also a UK fusion energy site.

None of the projects is close to designing a plant.
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.


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.]

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

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.

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

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 .

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

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

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

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.

Dr. H

Answer 2

I think you were meant to answer that question.

Nuclear power is contoversial. It isn't hard to find resources to that effect on the internet. Try Greepeace.

With respect to it making a comeback try thinking along the lines of:

a. Global warming.
b. The geopolitical problems which come with importing all your energy from politically unstable and unfriendly countries.

Answer 3

Why should we do your homework for you? Will you paint my family room if I do?