Imagine an "actinide recycling" campus of nuclear reactors & reprocessing

This thread follows on from many previous threads in this forum.

The first link I found on "actinide recycling" was negative. The site is the Garden State Enviro-net News site. It is a short treatment, and I can see some statements that gloss over details: http://www.gsenet.org/library/16nuc/nucwaste.php ">GSENET

Here is material that I found about actinide recycling: http://www.nae.edu/NAE/naehome.nsf/weblinks/MKEZ-5HUMJH?OpenDocument">Sustainable Energy from Nuclear Fission Power I would imagine that a large area would need to be dedicated to several stages of reaction and reprocessing. The last radioactive material to leave the campus promises to be lower-level and shorter-lived radioactive atoms.

I would have to study this article at length to say I thoroughly understand it. I put it up here for future reference and for comment by the E&E forum.

I always wondered how the French could store their nuclear waste in glass for disposal--it is because it has been reprocessed and reused. It is not the same material as America's nuclear power plants produce.

The author presents the sort of optimistic vision that a engineering professional in the field would make, but does admit that there is some development work that needs to be done: "Realizing the potential of fission energy will require high-conversion reactors and the recycling of fissionable atoms, which in turn will require that some technical and political challenges be met."

edit:typo

Can you repost them?

I would agree strongly with both of your last two paragraphs.

In the very last paragraph I would especially emphasize the word "political." The technical side is being actively addressed in many places around the world, including the internationally co-ordinated Gen IV reactor development program. What you note about the difference between French nuclear "waste" and American nuclear "waste" is almost wholly a function of a political rather than technical decisions.

I would be happy to extend my own opinion, about which I have thought extensively, on what a nuclear campus might look like, should you so desire.

Thank you also for taking the time to investigate my claims on your own.

I saw nuclear technology being discussed on another thread today, so did some searching that led me to those two links, and a number of highly technical links that were quite beyond me. I thought it was worth starting another thread with what I found.

The "nuclear campus " would doubtlessly have several reactors for the different stages and reprocessing facilities. It would take a large land area and need to be near a source of condenser water. It would have to be in the region where the electricity is to be used, therefore within 100 miles of the cities. These proposals for wind farms in Nebraska to serve urban America have a major limitation in that respect--large lengths of big powerlines.

Please enlighten me to whatever extent possible. I am supposed to be studying for a political science exam today and not squinting at equations (especially with this headache and cold I am putting up with).

On that thought, I'll leave you with a quote by John Adams :

"The science of government it is my duty to study, more than all other sciences; the arts of legislation and administration and negotiation ought to take the place of, indeed exclude, in a manner, all other arts. I must study politics and war, that our sons may have liberty to study mathematics and philosophy. Our sons ought to study mathematics and philosophy, geography, natural history and naval architecture, navigation, commerce and agriculture in order to give their children a right to study painting, poetry, music, architecture, statuary, tapestry and porcelain. "

is asking such an excellent questions.

In my view the greatest problem with nuclear energy has always been that it is very, very, high tech, and moreover will probably always remain so. People are naturally inclined to fear what they do not understand under ordinary circumstances. However the circumstances of nuclear energy, it's vast, highly concentrated power, are anything but ordinary. Indeed some of the most dramatic events of the twentieth century have names like these: Hiroshima, Nakasaki, Hydrogen bomb, Cuban Missile Crisis, Three Mile Island, and, of course, Chernobyl. All of these events dominated news coverage in their times and all inspired fear and all have an almost mystical - and to some extent mythological - hold on people's imaginations.

I wish I could direct you to a single source that would do what you ask and provide you a non-technical comprehensive picture. Although I have probably read tens of thousands of pages on the subject of nuclear energy myself; I am a technical guy and I personally love to squint at equations. Off the top of my head though, the best single volume I can suggest that might offer some, if not all, of what you desire is Richard Rhodes's "Nuclear Renewal," Viking Press 1993." Rhodes is the Pulitzer Prize winning author of "The Making of the Atomic Bomb," and "Dark Sun: The Making of the Hydrogen Bomb." (An abused child grown to a man, Rhodes has also written extensively on institutional and personal violence.)

A more recent volume has been published by French Physicist (and Nobel Prize Winner) George Charpak, "Megawatts and Megatons", Knopf, 2001. I have not read the book myself yet (although I have it out of the library) I have read that the level is somewhat technical, on the order of what one might find in Scientific American. I have heard, so as to believe it, that the treatment is balanced.

I could not answer this question without referring to some of the great minds in nuclear science, those of Alvin Weinberg and Bernard L. Cohen. Both have written popular volumes: Weinberg's autobiographical "The First Nuclear Era," is an account of the thinking that went into the design of the first commercial nuclear reactors. It includes gems like an account of his lunch with the moron and misrepresentation specialist Ralph Nader. It also explains why the early engineers did not focus on solutions to the problem of nuclear "waste." (They didn't think it was important.)

Weinberg was fired from his job as the Director of the Oak Ridge National Laboratory for pushing the Molten Salt Reactor (which he helped invent) over the liquid metal breeder reactor. (Your anti-nuclear link has some points that are well made about the latter type of reactor, though some things are missing.) The Molten Salt reactor (or better put, the class of Molten Salt ReactorS) is the key to the future.

Gotta go. I will get back with more.

Health physicist Bernard L. Cohen is one of the pioneers of risk analysis, especially as applied to questions of nuclear vs. non-nuclear options.

The sadly titled: "Nuclear Energy Option: An Alternative for the 90s" (Perseus Publishing, 1990) by Cohen (certainly a prophet without honor) is, sadly, out of print. It remains in a few libraries and can be purchased used in some places. My library sold their copy off, and I'm sorry to say I didn't buy it before they did so.

Here are two of the formal reviews posted on the Barnes and Nobel site:

(quote)

From The Critics
Publisher's Weekly
University of Pittsburgh physicist Cohen provides accessible, scientifically sound risk analyses of the energy options that he believes must be exercised in the next 10 years. This update of his work on public energy policy stands opposed to the stack of recent greenhouse effect-oriented titles by proposing more nuclear power plants (including fuel reprocessing plants) as statistically the safest, most environmentally sound solution. Cohen advances the debate on energy policy for all sides by first quantifying the human health costs of coal- and oil-generated electricity, and by debunking solar technology's deus ex machina role. In this context, Cohen looks at issues surrounding nuclear power since Three Mile Island, such as the ``unsolved problem'' of nuclear waste disposal and the ``China Syndrome.'' Media people especially are urged to re-examine ``nuclear hysteria'' (no one ever writes about `` deadly natural gas,'' Cohen notes), and even anti-nuclear activists will find the study's appendices and notes a sourcebook for the coming round of public policy issues likely to emerge as a result of the Mideast crisis. (Nov.)

Booknews
Cohen (physics and radiation health, U. of Pittsburgh) is an articulate and authoritative defender of nuclear power as both safe, environmentally sound and economically preferable. Referring to radon gas he notes that the radiation risk of nuclear power is equal to staying in an unvented house an extra eight hours per year. Annotation c. Book News, Inc., Portland, OR (booknews.com)

(unquote)

Dr. Cohen, at least in my esoteric little mind, stands among the great thinkers on the subject of nuclear energy and the environment.
He has published extensively in the scientific literature.

Dr. Cohen's work figures prominently in the recent "Risk-Benefit Analysis" (Harvard University Press, 2001) by Harvard Physicist Richard Wilson and Edmund Crouch of Cambridge Environmental.

One of the more fascinating facts in this work concerns the Cassini spaceprobe to Saturn. Over 80 websites back in 1997 were dedicated to stopping Cassini, on the grounds it contained Plutonium and was scheduled to fly by Earth after swinging around Venus for a gravitational push. (The Plutonium isotope was same 238 isotope that also powered the lunar device on Apollo 13 that crashed into the earth in 1970 and for many years was used to power pacemakers.) Dr. Wilson calculates on page 240-241 that the risk of contamination from this probe colliding with the earth on its fly by and actually killing someone was 1 in 100 billion, meaning that if one probe with the same trajectory were launched during each second for three millenia, someone actually might die.

I may be odd, but I think there's something chilling about that calculation.

The Cassini probe, BTW, will enter Saturn's orbit later this year, in a little over three months. It has functioned exactly as designed.

... what political science can tell us about the U.S. establishment's tendency for xenophobia and hostility towards dark-skinned countries, esp. ones that set out to implement powerful technologies.

Politically speaking, how are developing countries going to use nuclear energy as a safety net and a public asset while avoiding the mendacity of the American Right?

I am taking political science at night school so that I can learn how these systems operate so that I can influence them. It is obvious that the political systems of this country have been usurped by nasty, selfish rulers, and I am trying to find a way to bring our political systeme back into alignment. That is why I am studying. This year I plan to work on actual campaigns, either state or national campaigns, depending on where I think I can be effective.

"Point"
Garden State Enviro-net News
"Counterpoint"
Sustainable Energy from Nuclear Fission Power

Even the French don't have any place to store their long term waste. It just stacks up in some temparairy place.

It has no home.

First I will talk about the short term nuclear park of the first kind, the electricity generating park. These will certainly be the first kind of reactors built, to replace the extremely dangerous and currently widely used fuel, coal with a safer cleaner option.

It is highly probable that most of the next series of reactors we will see will be improved versions of the highly reliable and highly successful PWR with which tens of thousands of reactor years of experience has been accumulated. These will probably be the work horse reactors for electrical generation for many years to come, if only because of their extraordinary success.

Probably the major difference that will realized between the existing nuclear program and the future program will be that in the future many of these reactors will have a different fuel than has been historically used. The new fuel configuration will probably be a modification of what is known as the Radowsky concept. This concept is particularly well suited to actinide recycling because it offers a way to 1) burn excess plutonium, 2) extend fuel life because of greater neutron efficiency and because of Thorium breeding, 3) reduce the need (long term) for enrichment strategies. Basically the Radowsky concept (which can be applied with existing PWR's) uses Thorium as a fuel and Plutonium as a starting agent. The plutonium is removed from the recycled fuel (probably alloyed with some existent Uranium) placed back in the reactor and burned. The reduction in the quantity of plutonium in the reactor is reduced in one cycle by between 60% to 80% (negating the necessity for disposal), the energy is recovered, and a new form of U-233 enriched Uranium is recovered for additional recycling in additional fuel cycles. Further, the plutonium that remains behind is much, much less suitable for proliferation diversion, particularly if it has been obtained from recycled Uranium.

97% percent of the fuel removed from a nuclear reactor after a first cycle consists merely of the Uranium that originally came from the mine. (This is NOT new radioactivity: 97% percent of the mass of radioactive material removed from a nuclear reactor is merely material that has been radioactive since the formation of the earth.) This Uranium has an enormous energy content, even without conversion to plutonium. The reason is that PWR type nuclear reactors shut down before their fuel is entirely consumed because some of the fission products, such as Samarium-149, are potent neutron absorbers. PWR, which uses natural water as a moderator, needs fuel that is enriched so that the fissionable nuclei (either Uranium-235 (common today) or Uranium-233 (obtained from Thorium in the future) is about 3-5% in concentration. Because the Uranium is removed before all of the fissionable nuclei are in fact fissioned, it is still usable as a fuel in a reactor of a type different than PWR. To extend the efficiency with which fuel is used, thus minimizing the so-called "waste" the next type of reactor you would want in the series would be a CANDU type reactor. So to begin with a first generation nuclear actinide recycling park would include both a series of PWR reactors and CANDU reactors.

I will discuss CANDU reactors in the next post.

Quote



CANDU/LWR Synergism

"Although little incentive exists for the extraction of fissile material from spent CANDU fuel, based upon its low fissile concentration, the opposite is true for spent LWR fuel. Depending upon initial enrichment and burnup, spent LWR fuel contains about 0.9 wt% U-235 and 0.6% fissile plutonium.

Since the U-235 content exceeds that of natural uranium, CANDU technology offers the unique option of uranium recycling without reenrichment. This "recovered uranium" (RU) fuel cycle would have all the benefits of SEU fuel cycles described above, and would extract at least 25% more energy from the mined uranium going into the LWR fuel cycle. Compared to reenriching the RU for use in an LWR, about twice as much energy can be extracted by burning it without reenrichment in a CANDU reactor.

Twice the energy can also be extracted from burning LWR-recycled plutonium in a CANDU reactor, compared to using an LWR. In general, therefore, CANDU technology is an efficient vehicle for the recovery of fissile material at the back end of the LWR fuel cycle. "



end quote.

The reasons for including highly flexible and reliable CANDU reactors in an Actinide recycling park are given in this excellent essay. There are no equations in the whole thing, just clear explanation of how these fabulous reactors work and what they can do.

http://www.nuclearfaq.ca/brat_fuel.htm

There are two disadvantages of the CANDU reactor design. One is the cost of its heavy water. CANDU reactors require the purest grade of heavy water ever developed, "reactor grade," better than 99.975% pure. Tonnes of this expensive substance are required to fill a CANDU's calandria. Such pure heavy water is expensive because heavy water is chemically indistinguishable from normal water, and mixes easily with it.

but once you have obtained the heavy water, can't it be used for a long time? or does it escape as steam and need constant replenishment?

The second major disadvantage is that since the reactor can use unenriched uranium, the reactor could in principle be used to produce plutonium for nuclear weapons. Canada requires states to agree not to produce nuclear weapons in order to purchase CANDU designs, but the plutonium for the weapons programs of India and North Korea are believed to use reactors similar to CANDU.

is plutonium production just more fear-mongering or a real possibility? (i.e., most of the information that is pulled up in searches suggest that plutonium is reprocessed, not created, in the CANDU reactor)

It sits in pressure tubes and can last essentially for the lifetime of the reactor.

It turns out that hydrogen isotopes are the easiest to separate in the periodic table, because the atomic weight to deuterium is twice that of hydrogen. Ordinary electrolysis results in isotopic fractionation in water. If one electrolyzes water the water left behind in the process is enriched with respect to deuterium. By continually adding water to an electrolysis system, one can obtain very high concentrations of deuterium oxide (heavy water).

Modern CANDU 9 reactors use less heavy water than do earlier designs, but these days the cost of heavy water is not really a huge problem. Nuclear reactors have always required some exotic materials, including Hafnium free Zirconium. Obtaining Hafnium free Zirconium was a huge challenge to nuclear engineers way back in the days of the Manhattan project.

The proliferation concern is real with CANDU reactors and CANNOT be summarily dismissed as an invalid objection to them. It happens that CANDUs are perfectly suited - better than most other reactors -for the destruction of weapons grade fissionable material, but it also happens that they are the best suited commercial reactors - along with the awful RMBK - for making new weapons grade plutonium. This is because CANDUs can be refueled while operating. This makes them more economical, but it also theoretically increases the risk that one can obtain plutonium of any desired isotopic composition.

I personally regard proliferation issues as the most serious risk of nuclear power - although this risk, like others, can be minimized, perhaps even eliminated. This topic is the place to discuss these issues. Since I will talk about the evolution of plutonium in recycling schemes, I will explore this further. I believe that a terrorist risk from someone stealing plutonium from a commercial nuclear facility is absurdly small and is vastly overplayed by the media. I will discuss how can easily the terrorist be made even smaller in the future.

Still an insidious government equipped with CANDUs and sufficient financial resources is a real cause for concern. I note on this point that India's nuclear weapons program probably makes use of CANDU technology. On balance, I believe that CANDUs are reactors that should be built and used because of their many attractive features and their importance to the environment. But even I, Mr. "Big-Bad-Nuclear-is-rosy" will add a caveat for these reactors: Where they are built they should be subject to very careful monitoring by international authorities such as the IAEA. They're great in Canada, Europe, in Japan and many other places. They're not so great in Iran or North Korea or even India. (Whether we like it or not though, India will build them.)

nuclear park, we need understand a little bit about nuclear isotopes in actinides. As one recycles nuclear fuels, the isotopic composition of the actinide elements in the fuels evolves and becomes more complex.

Naturally occurring Uranium consists, for example, consists of three isotopes, Uranium-238, Uranium-234, and Uranium-235. The percentage of the various isotopes in most deposits is this: U-238 99.2745% of the atoms, U-235, 0.720% of the atoms, and U-234, 0.0055%. The half-lives of U-238 and U-235 are 4.468 billion years and 703.8 million years respectively. Both of these isotopes are artifacts of the original supernovae that synthesized all of the elements heavier than boron that now comprise the earth. (As Joni Mitchell said and Dennis Kucinich plagiarized, "We are stardust...")

The isotopic composition of natural Uranium can vary from the precise figures given above. Because Uranium-235 decays much faster than Uranium-238, long ago in geological history, it was present in much greater proportions. Several billion years ago, in fact, the composition of natural Uranium was what we now call "enriched." The percentage of Uranium-235 was greater than 3%. As a result, it actually happened that nuclear reactors, moderated by water, naturally occurred, at a place called Oklo in modern day Gabon. These fossil reactors, about 15 are known, apparently operated for hundreds of thousands of years and today give us important information about the geological behavior of fission products. They were discovered because the Uranium found in mines in Oklo was found to be surprisingly depleted today; Uranium found there has far less Uranium-235 proportionally than one would normally expect.

Both U-235 and U-238 survive only because their half-lives are roughly comparable with the age of the earth (4.5 billion years, in most estimates.) Uranium-234 has a relatively short half-life with respect to the earth, 245,500 years. The 234 isotope exists only because it is in the U-238 decay chain: Uranium-238 spontaneously ejects a helium nucleus to become Thorium-234 which in turn rapidly emits a beta particle (an electron) to become Protactinium-234 which finally emits yet another beta particle to become Uranium-234. We say that Uranium-234 is an element of the U-238 "decay chain."

The other naturally occurring actinide is Thorium-232. It has a half life of 14.05 billion years. Thorium has about ten times the abundance of Uranium in the Earth's crust. In the future it will be a very important nuclear fuel.

There are four possible decay chains; only three occur naturally, the Uranium-235 decay chain, the Uranium-238 decay chain and the Thorium-232 decay chain. The other decay chain, the Neptunium-237 decay chain is now extinct. (It is highly probable that some Plutonium-244 accrued in the proto-earth, but it has now all decayed to Thorium. Besides Plutonium-244 and Neptunium-237, Curium-247 (half-life 15.6 million years) may be another extinct nuclei found in the early earth. It is a member of the Uranium-235 decay chain. If enough Curium-247 survived to accrue in the earth then Plutonium-239 was once found here.)

Most people who know a little about nuclear energy know that of these three naturally occurring Uranium isotopes, only Uranium-235 is immediately useful in nuclear fission reactors. It is the only naturally occurring isotope that can be made to split in such a way that it produces more than two neutrons for each required to split it, i.e. to sustain a chain reaction. Moreover, the isotopic composition of Uranium is such that, because Uranium-235 is so dilute - one needs to take extraordinary means to get a chain reaction to occur.

To use one needs to slow neutrons down (because slow neutrons split atoms more efficiently) without losing them to absorption by elements other than Uranium. There are only two ways to accomplish this in natural Uranium, by use of highly purified graphite as a moderator (or neutron slowing agent), and by the use of heavy water. Both of these avenues have been used in nuclear reactors. The very first nuclear reactor, built by Enrico Fermi in a squash court in downtown Chicago, used graphite. The first large scale reactor, the N-reactor at Handford Washington built for weapons production, also used graphite as a moderator. So did the infamous reactors at Chernobyl and Windscale, in the UK, both of which were destroyed by fires. The other option, heavy water, was first used by the Canadians because they thought Uranium would soon become very expensive. This is the aforementioned CANDU, the reactor I think should be in many nuclear parks. CANDU reactors are extraordinarily safe and extraordinarily efficient; features that are unfortunately off-set by the potential of these reactors to be diverted, in the wrong hands, for weapons manufacture.

Normally we don't bother to use natural Uranium in CANDU or graphite reactors. Using chemico-physical means, we enrich it. We increase the ratio of U-235 to U-238 and throw some of the Uranium-238 away. Uranium-238 that is discarded (not that discarding it is a good idea) is called "Depleted Uranium."

To minimize proliferation risks, I advocate a Thorium based fuel cycle. In this cycle an isotope of Uranium from the extinct Neptunium-237 decay chain, Uranium-233, is created by bombarding Thorium-232 with neutrons produced in a nuclear reactor. The resulting Thorium-233 goes through two beta decays to become Protactinium-233 and Uranium-233, the last of which has better fission properties than does Uranium-235. Two other isotopes are produced when Thorium is so bombarded, Uranium-232 and synthetic (as opposed to natural) Uranium-234.

Further, it does not happen that Uranium-235 fissions every time it is hit with a neutron. Sometimes it merely absorbs the neutron without splitting, creating an isotope that does not exist naturally on earth, Uranium-236. Some of the Uranium-238 also captures neutrons to become Uranium-239. Uranium-239 in turn decays very rapidly through two beta emissions to give the very interesting and famous isotope Pu-239, a member of the U-235 decay chain, and like Uranium-235, very fissionable.

(The important fissionable actinides are in general those that have an even number of protons and an odd number of neutrons.)

This means that if natural Uranium (or depleted Uranium) is continually recycled through nuclear reactors containing Thorium, a new and very different isotopic mixture than normal is obtained. Uranium-235 is depleted by fission and adsorption. The unnatural isotopes Uranium-232, Uranium-233 and Uranium-236 are created. Additional Uranium-234 is created.

A very analogous process takes place when one uses Plutonium-239 to fuel nuclear reactors. Plutonium that has been in a nuclear reactor just once is very different from plutonium that is continuously recycled. This is a very important property that can be exploited for the minimization of proliferation risk, and if I finish this thread, I will probably discuss this matter at length.

Although all of the isotopes of particular elements, most importantly Plutonium and Uranium are chemically the same, their nuclear properties are very different. This places certain physical requirements on the nuclear reactors that use recycled fuel safely. To some extent one can manage to address these requirements in the operation of PWR reactors and CANDU reactors, especially in the latter.

However there is even a better way.

It is for this reason the next reactor I would propose in a nuclear park would be the very flexible, very safe and very interesting Molten Salt Reactor. I will discuss this reactor in my next post to this thread.

A political liberal like myself who favors the expansion of nuclear energy necessarily hangs out in circles where one hears, unfortunately, some pretty formulaic criticisms of nuclear energy.

One of the more curious formulaic objections goes like this: "Nuclear energy is not too cheap to meter." People apparently think that this standard of being too cheap to meter should be applied to nuclear energy because of a remark made by Admiral Lewis L. Strauss, then Chairman of the U.S. Atomic Energy Commission when he was speaking to a convention of science writers in 1954. Actually the Admiral was speaking on the subject of the potential of fusion energy and not fission but this is really of no matter. People somehow feel that because nuclear energy is in fact, not too cheap to meter, that they are perfectly justified in demanding it be shut down. (I seldom hear people ask for the space program to be shut down because Werner Von Braun promised colonies on the moon by the end of the 20th century, but hey, that's another matter.)

Very often anti-nuclear arguments such conversations are accompanied by the statement that solar energy is "free" because there is no meter on sunlight.

We have in fact reproduced such conversations exactly here at DU.

Here is what is happening in these conversations: The argument that solar energy is free focuses exclusively on the cost of the fuel (sunlight) and completely ignores the capital cost of the system that converts the solar energy into usable electricity (the PV cell, storage batteries, etc, etc.) A completely opposite approach is used in describing nuclear energy. The inordinately low cost of the fuel is completely ignored, while the capital cost of the conversion system (the reactor) is the primary focus.

This semantic approach works quite well until someone is asked to take out their wallet and actually buy a solar system, i.e., put their money where their mouth is. Most people, simply because they cannot really afford the capital outlay, do not buy solar cells to power their homes. Instead they buy their power from a power company, power which, in the United States consists of about 20% nuclear energy.

Actually it happens that energy too cheap to meter does not exist anywhere in any form today. This then is another case wherein if we apply the same standard to all other forms of energy that we apply to nuclear, we will be compelled to shut all forms of energy down.

One of the reasons that nuclear energy is much, much, much cheaper than solar energy has to do with the fact that, if one looks at the cost of the fuel and ignores the cost of the reactor, nuclear energy IS "too cheap to meter." That's right folks: If you judged it by the exact same standards as people commonly judge solar energy, solely on the cost of fuel, nuclear energy's practically free. Considering the amount of energy contained in Uranium, prices are very, very low. In fact, the cost of generating nuclear power is almost completely independent of the cost of its fuel.

The reason that Uranium is so cheap has to do with two spectacular failures of nuclear energy: Three Mile Island and Chernobyl. These two events, which I have discussed at length in other threads, made the public worldwide quite leery of nuclear energy, and development of nuclear power was slowed down at the very same time that new reserves of Uranium were being found at a spectacular pace. Since there is lots of Uranium and demand is increasing only slowly, the price of Uranium has fallen. If memory serves me well, its about $15/kg, pretty damn cheap.

Even so, today most nuclear companies don't make very money building reactors. They make their money manufacturing fuel assemblies for existing reactors. Although fuel assemblies last quite some time in ordinary BWR and PWR and CANDU reactors, up to five years with some reshuffling, they are very high precision structures with very rigid specifications. As I've said, the cost of the Uranium going into these assemblies, especially in CANDU type reactors is completely trivial.

Making fuel assemblies adds some cost to nuclear fuel. At the same time it is the source of much of the profit for the supply side of the fuel. A cheap $15/kg material can be made into a value added product (a fuel assembly).

Interestingly enough though there is a way to dispense with making assemblies all together, making the fuel fall even further toward the standard of "too cheap to meter": Simply throw the Uranium without any assemblies at all into a mixture of appropriate salts, let the salts melt from the heat of nuclear reactions, and take the heat out in the form of electricity or motor fuel. In such a system there is very little need for mechanical parts, like control rods, machinery, fuel assemblies, and a whole bunch of other junk that makes a nuclear machine very expensive to build (but not to operate). There is also very little to maintain.

Before you say that such a reactor sounds too good to be true, I will note that one has operated. The MSRE, (Molten Salt Reactor Experiment) ran for quite a number of years at Oak Ridge National Laboratory. Moreover the experiment was a huge success. Despite much lobbying on the part of the director of the Lab, Alvin Weinberg, the project was canceled in favor of the Liquid Metal Breeder Reactor LMBR. As I sit here and contemplate the reason for this folly the cancellation of the MSR program, and indeed it was folly, I have to believe that the necessity for maintaining a heavy infrastructure and the profit had more to do with canceling the project than technical issues. (The other factor probably involved the fact that the MSR is proliferation resistant; not a selling point in a time when the government was looking for ways to make plutonium for nuclear weapons, a task for which LMBR technology is better suited.) You simply could not make as much money pouring powder as you could making assemblies.

Today the MSR is back. It has been selected for development as a part of the international Generation IV nuclear program, the program in which leading countries (including for the time being the United States even though the US is working harder at becoming a trailing country than it is at improved energy options.) Russia, Japan, the Czechs, France and other countries are exploring MSR designs.

The reason for selection of the MSR is very important. The price of nuclear fuel will rise as people grow to accept how safe and clean nuclear energy is relative to their other options. (I am trying as hard as I can to spread the word.) For environmental reasons they will want to minimize the toxicity of nuclear discharges. They will want to expand nuclear energy rapidly, and cheaply at the lowest possible cost using the simplest designs. As the use of nuclear energy rises, however, the price of the fuel will also rise. Therefore future generations will want to keep the fuel cheap by using it more efficiently. (Today only 1% of the energy value of Uranium is recovered; the other 99% is discarded as "waste.") All of these goals are achievable through the use of the MSR.

I will try to follow up with more on this subject in my next post, when I have time.

The most serious criticism of nuclear energy, though certainly not a show stopper from in an energy source risk comparison sense, is that the by-product of a nuclear energy program produces material that is suitable for use in nuclear weapons.

The key element (pun intended) in this concern is the production of Plutonium. Since Seaborg and his colleagues first identified this element using tracer studies of tiny, indeed invisible, quantities, over 1200 Metric Tons of Plutonium has now accumulated on the earth. Of this, roughly 300 metric tons of which was deliberately manufactured for the purpose of making nuclear weapons. The balance of this material is a by-product of nuclear power production.

(A side note: Seaborg's original sample of plutonium is on display at the Museum of American History, a part of the Smithsonian institution in Washington DC. His Nobel Prize medal is also displayed there.)

Glib proponents of the expansion of nuclear energy such as myself often refer to the difference between weapons grade plutonium, which usually consists of plutonium having 95%+ of the fissionable isotope Pu-239, and reactor grade plutonium, wherein the proportion of this isotope is much less, somewhere around 80%. Although people like me often wish to imply that the properties of reactor grade plutonium make it completely unusable in nuclear weapons, we are NOT 100% correct when we say that. The Energy Secretary in the last sane government to occupy the White House, (that would be the Clinton Administration) confirmed what many people have long suspected. In 1963 the United States assembled a nuclear weapon using reactor grade plutonium, having between 15%-20% of the isotope Plutonium-240. Although the explosive yield of the weapon was very much lower, and the assembly very difficult, the bomb did in fact successfully detonate. Therefore it cannot be said that the probability of diversion of plutonium from a commercial nuclear operation is known to be zero. It may be small, but it is not zero.

Plutonium is not only usable in the core of a nuclear weapon however, it is also practical to use it as a nuclear fuel in nuclear power plants. This is in fact, commercial practice in several places. Indeed, most of the energy value found in nuclear fuels in use everywhere, is regarded by many as waste. Only 1% of the total energy available in Uranium is actually recovered at the turbines. The rest of it is generally treated (at least for now) as "waste."

In countries where plutonium is consumed, of course, the volume and mass of plutonium are greatly reduced of course. Not only that, but the isotopic composition is even more "denatured" than it was for the Plutonium used in the test revealed by Mrs. O'Leary. However, it is not true that you can make the percentage of the Plutonium-239 arbitrarily small when one is refueling nuclear reactors, at least when Uranium-238 (the most common isotope) is present. It has been estimated that a continuous plutonium recycling program using thermal reactors will result in plutonium that has the following isotopic composition: Plutonium 238, 4%; Plutonium-239, 45%; Plutonium-240, 20%; Plutonium-241, 10%, and Plutonium-242, roughly 4%. This is actually in some ways, a happy state of affairs: Plutonium-238 and Plutonium-241, present in only small amounts in Mrs. O'Leary's Plutonium, generate lots of heat, making the assembly of nuclear weapons from it even more problematic than it is from current "reactor grade" plutonium. However, a nuclear weapon is a fast fission device; and I will not claim that it is impossible to use such Plutonium in a nuclear weapon.


In the United States, about 2000 MT of Uranium is run through nuclear reactors each year. Of this, about 21 tons are converted into the "trans-Uranium" elements, including Plutonium. Plutonium is in fact by far the vast majority of transuranium elements produced in American "once through" nuclear reactors.

The early workers in the development of nuclear power were all by and large extraordinary geniuses of the first order. Even so, they made several mistakes. One thing that they did not anticipate for instance, was that the element Uranium was actually relatively common, about as common as tin, in fact. In their estimation, the only way to have a sustained nuclear energy program was to recover some of the 99% of the energy in Uranium that we now look to throw away. For this reason, very early in the nuclear era, a main point objective of research was to find a way to get at this energy. This involved converting the non-fissionable Uranium-238 into Plutonium-239, the infamous material whose discovery was announced in the explosion at Nagasaki.

One solution to this problem that they pursued, the solution that was ultimately pursued, was the fast breeder reactor, a reactor that had a core that was bathed in liquid metal, typically sodium or a low melting alloy of sodium and potassium metal. Commercial versions of these reactors, known as LMFBR (liquid metal fast breeder reactors) have been built, but they are, for the time being anyway, commercial failures. Uranium today is actually "too cheap to meter" and the world is already awash in an excess of Plutonium. The problem is not how do we make Plutonium, but how to get rid of, or minimize, the inventory that which we already have.

There are other problems with LMFBRs. One is that the versions that have been commercialized have positive void coefficients in Loss of Cooling Accidents. This means that they lack "passive" safety features, and safety systems must be built in by other means, increasing costs. (The United States designed and tested a fast breeder liquid metal reactor, the IFR, now canceled, that surmounted this problem. The cancellation involved the reality that we don't need more plutonium right now.) Another problem is that the liquid metals in the cores are corrosive and flammable. These problems can be more or less engineered away, as was done with the IFR. However, the (albeit probabilistically small) problem of the suitability of obtained plutonium for nuclear weapons differs with fast reactors: The isotopic composition of Plutonium is much more like Mrs. O'Leary's Plutonium: Plutonium 238, 0.8%; Plutonium-239, 70%; Plutonium-240, 23%; Plutonium-241,3%, and Plutonium-242, roughly 2%. The heat producing isotopes, 238 and 241 are relatively reduced. Therefore the proliferation risk is somewhat increased with fast reactors. (In contrast, it can be shown that the long-term radiotoxicity risk in fast reactors is greatly reduced.)

Fortunately, there is another option to recover 100% of the energy available in actinide elements. This involves the use of the synthetic isotope U-233, which can be obtained from Plutonium. Uranium 233 is like Plutonium-239 in one important way. When it fissions, it releases enough neutrons to 1) fission another atom, i.e. participate in a chain reaction, and 2) convert a non-fissionable nucleus such as Uranium-238 or Thorium-232 into a fissionable nucleus like Plutonium-239 or Uranium-233. There is an important difference though between the situation with these materials though. Plutonium only behaves this way under "fast" conditions, such as those found in the LMFBR. Uranium-233 however behaves this way under thermal conditions such as one obtains in ordinary PWRs and CANDUs. There is one problem though, the time scale on which this breeding occurs is complicated by the existence of intermediates, Neptunium-239 in the Uranium/Plutonium couple, and Protactinium-233 in the Thorium/U-233 couple. Protactinium-233 has a much longer half life than Neptunium 239, about 27 days as compared with 2 days. For this reason, if one wants to "breed" new nuclear fuel, it would be ideal to remove the Protactinium for a while, let it decay, and put it back into the reactor.

One cannot do this in normal reactors, but Alvin Weinberg, the inventor of the Molten Salt Reactor showed back in the 1960s that one could conveniently and quickly manipulate nuclear fuel under continuous conditions using the Molten Salt Reactor. The Molten Salt Reactor is therefore available to assist in the recovery of more of the potential energy found in Uranium and Thorium resources. Moreover, the simplicity and ease with which can this be done is quite remarkable. The flexibility that one obtains in doing this, in determining the isotopic composition of Plutonium, destroying Plutonium (and recovering its energy), and destroying other problematic nuclear materials now considered waste is also extraordinary.

More later.

In a related thread, I have egotistically suggested that this thread might represent a means of technical exposition of how to back one's ideas up.

Note: I have abandoned my promised other posts to this thread on the grounds there was a lack of interest (because my ideas are preternaturally silly and I am in fact a ninth grader).

http://www.democraticunderground.com/discuss/duboard.php?az=post&forum=115&topic_id=6799&mesg_id=7520