Sorensen Rebuttal of IEER/PSR Thorium Paper

Several people who have recently learned about thorium have contacted me with regards to a “fact sheet” about thorium issued by the Institute for Energy and Environmental Research (IEER) and
Physicians for Social Responsibility (PSR) called “Thorium Fuel: No Panacea for Nuclear Power.” The authors of this sheet were Arjun Makhijani and Michele Boyd.

Last year, Dr. Alexander Cannara wrote a letter to IEER/PSR pointing out errors and omissions in the “fact sheet” and requesting IEER/PSR to implement corrections. To the best of my knowledge no amendment or correction was ever issued.

I have taken it upon myself to write a more extended rebuttal to the claims made about thorium by Makhijani and Boyd and submit it to the online community for your consideration. The entirety of their original statement is included in the rebuttal and denoted by italics.

Thorium “fuel” has been proposed as an alternative to uranium fuel in nuclear reactors. There are not “thorium reactors,” but rather proposals to use thorium as a “fuel” in different types of reactors, including existing light-water reactors and various fast breeder reactor designs.

It would seem that Mr. Makhijani and Ms. Boyd are unaware of the work done at Oak Ridge National Laboratory under Dr. Alvin Weinberg from 1955 to 1974 on the subject of fluid-fueled reactors, particularly those that used liquid-fluoride salts as a medium in which to sustain nuclear reactions. The liquid-fluoride reactor was the most promising of these fluid-fueled designs, and indeed it did have the capability to use thorium as fuel. It was not a light-water reactor, nor was it a fast-breeder reactor. It has a thermal (slowed-down) neutron spectrum which made it easier to control and vastly improved the amount of fissile fuel it needed to start. It operated at atmospheric pressure rather than the high pressure of water-cooled reactors. It was also singularly suited to the use of thorium due to the nature of its chemistry and the chemistry of thorium and uranium.

Thorium, which refers to thorium-232, is a radioactive metal that is about three times more abundant than uranium in the natural environment. Large known deposits are in Australia, India, and Norway. Some of the largest reserves are found in Idaho in the U.S. The primary U.S. company advocating for thorium fuel is Thorium Power (www.thoriumpower.com). Contrary to the claims made or implied by thorium proponents, however, thorium doesn’t solve the proliferation, waste, safety, or cost problems of nuclear power, and it still faces major technical hurdles for commercialization.

Mr. Makhijani and Ms. Boyd may wish to update their document since “Thorium Power” is now called “Lightbridge” and no longer advocates for the use of thorium, whereas the community of supporters of liquid-fluoride thorium reactors (LFTR) still maintains strong support for the use of thorium because it is indeed a solution to the issues of proliferation, waste, safety, and cost that accompany the present use of solid-fueled, water-cooled reactors.

Thorium is not actually a “fuel” because it is not fissile and therefore cannot be used to start or sustain a nuclear chain reaction. A fissile material, such as uranium-235 (U-235) or plutonium-239 (which is made in reactors from uranium-238), is required to kick-start the reaction. The enriched uranium fuel or plutonium fuel also maintains the chain reaction until enough of the thorium target material has been converted into fissile uranium-233 (U-233) to take over much or most of the job. An advantage of thorium is that it absorbs slow neutrons relatively efficiently (compared to uranium-238) to produce fissile uranium-233.

On the contrary, thorium is very much a fuel because in the steady-state operation of a LFTR, it is the only thing that is consumed to make energy. Makhijani and Boyd are correct that any nuclear reactor needs fissile material to start the chain reaction, and the LFTR is no different, but the important point is that once started on fissile material, LFTR can run indefinitely on only thorium as a feed—it will not continue to consume fissile material. That is very much the characteristic of a true fuel. “Burning thorium” in this manner is possible because the LFTR uses the neutrons from the fissioning of uranium-233 to convert thorium into uranium-233 at the same rate at which it is consumed. The “inventory” of uranium-233 remains stable over the life of the reactor when production and consumption are balanced. Today’s reactors use solid-uranium oxide fuel that is covalently-bonded and sustains radiation damage during its time in the reactor. The fluoride fuel used in LFTR is ionically-bonded and impervious to radiation damage no matter what the exposure duration. LFTR can be used to consume uranium-235 or plutonium-239 recovered from nuclear weapons and “convert” it, for all intents and purposes, to uranium-233 that will enable the production of energy from thorium indefinitely. Truly this is a reactor design that can “beat swords into plowshares” in a safe and economically attractive way.

The use of enriched uranium or plutonium in thorium fuel has proliferation implications. Although U-235 is found in nature, it is only 0.7 percent of natural uranium, so the proportion of U-235 must be industrially increased to make “enriched uranium” for use in reactors. Highly enriched uranium and separated plutonium are nuclear weapons materials.

Since so many nuclear weapons have already been built and are being decommissioned, one might assume that Makhijani and Boyd would welcome a technology like LFTR that could safely consume these sensitive materials in an economically-advantageous way, beating swords into plowshares and using material that was once fashioned as a weapon as a material that can provide light and energy to billions. Enriched uranium or plutonium can’t simply be “thrown away”. LFTR puts these materials to productive use as they are destroyed in the reactor and uranium-233 is generated.

In addition, U-233 is as effective as plutonium-239 for making nuclear bombs. In most proposed thorium fuel cycles, reprocessing is required to separate out the U-233 for use in fresh fuel. This means that, like uranium fuel with reprocessing, bomb-making material is separated out, making it vulnerable to theft or diversion. Some proposed thorium fuel cycles even require 20% enriched uranium in order to get the chain reaction started in existing reactors using thorium fuel. It takes 90% enrichment to make weapons-usable uranium, but very little additional work is needed to move from 20% enrichment to 90% enrichment. Most of the separative work is needed to go from natural uranium, which has 0.7% uranium-235 to 20% U-235.

In a fluoride reactor, all of the fuel processing equipment will be located in a containment region containing the reactor and its primary heat exchangers, under very high radiation fields, and under the high heat needed to keep the fuel liquid. Once the system is properly designed to direct uranium-233 created in the outer regions of the reactor (the “blanket”) to the central regions of the reactor (the “core”) there will be no possibility of redirection of the material flow. Such a redirection would necessitate a rebuild of the entire reactor and would be vastly beyond the capabilities of the operators. Furthermore, the nature of U-233 removal and transfer from blanket to core involves the operation of an electrolytic cell that will allow very precise control and accountability of the material in question. Unlike solid-fueled reactors the uranium-233 never needs to leave the secure area of the containment building or come in contact with humans in order to continue the operation of the reactor. This is another important point that the authors have failed to distinguish as they have ignored the existence or implications of fluid-fueled thorium reactors.

To claim that uranium-233 is just as effective as plutonium-239 for nuclear weapons is gross simplification bordering on outright deception. They have similar values for critical mass, but this leaves out a very important point. The nuclear reactions that consume uranium-233 also produce small amounts of uranium-232, a contaminant that will later be mentioned by the authors but ignored at this stage of the criticism. U-232 has a decay sequence that includes the hard gamma-ray-emitting radioisotopes bismuth-212 and thallium-208. Indeed, the half-life of U-232 is short enough that this decay chain begins to set up within days of the purification of the uranium, and within a few months that gamma-ray flux from the material is intense. These gamma rays destroy the electronics of a nuclear weapon, compromise the chemical explosives, and clearly signal to detection systems where the fissile material is located. This is one of the key reasons why no operational nuclear weapons have ever been built using uranium-233 as the fissile material.

It has been claimed that thorium fuel cycles with reprocessing would be much less of a proliferation risk because the thorium can be mixed with uranium-238. In this case, fissile uranium-233 is also mixed with non-fissile uranium-238. The claim is that if the uranium-238 content is high enough, the mixture cannot be used to make bombs without a complex uranium enrichment plant. This is misleading. More uranium-238 does dilute the uranium-233, but it also results in the production of more plutonium-239 as the reactor operates. So the proliferation problem remains either bomb-usable uranium-233 or bomb-usable plutonium is created and can be separated out by reprocessing.

In my opinion, mixing uranium-238 with uranium-233 during the normal operation of a LFTR is a bad idea because it compromises the capability of the reactor to “burn” thorium to a degree that it then becomes necessary to add fissile material to keep the reactor running. This is because uranium-238 will absorb many of the neutrons that would otherwise convert thorium into uranium-233, instead converting uranium-238 into plutonium-239. Plutonium-239 is a poor fuel in a LFTR due to the limited solubility of plutonium trifluoride (PuF3) and the poor performance of plutonium in a thermal-neutron spectrum (only 2/3 of the plutonium-239 will fission when struck by a neutron).

But something is possible in the fluid fuel of a LFTR that is impossible in the solid fuel of a conventional reactor with regards to the “downblending” of uranium. Under extreme scenarios, it may be desireable to have a separate supply of uranium-238 inside the reactor containment that could be irreversibly mixed with the uranium-233 in the core. This would have the effect of making the reactor unable to restart, and despite the contention of Makhajani and Boyd, there is no feasible way to isotopically separate uranium-233 (contaminated with uranium-232) from uranium-238 because of the severe gamma radiation that would be emitted during any attempt to separate the isotopes. This approach to “just-in-time” downblending is only possible with fluid fuel, and its absence of consideration in the document again shows that the authors are unaware of the fluid fuel option and its implications.

Further, while an enrichment plant is needed to separate U-233 from U-238, it would take less separative work to do so than enriching natural uranium. This is because U-233 is five atomic weight units lighter than U-238, compared to only three for U-235. It is true that such enrichment would not be a straightforward matter because the U-233 is contaminated with U-232, which is highly radioactive and has very radioactive radionuclides in its decay chain. The radiation-dose-related problems associated with separating U-233 from U-238 and then handling the U-233 would be considerable and more complex than enriching natural uranium for the purpose of bomb making. But in principle, the separation can be done, especially if worker safety is not a primary concern; the resulting U-233 can be used to make bombs. There is just no way to avoid proliferation problems associated with thorium fuel cycles that involve reprocessing. Thorium fuel cycles without reprocessing would offer the same temptation to reprocess as today’s once-through uranium fuel cycles.

Makhijani and Boyd really betray a fundamental lack of understanding of the nature of uranium isotope separation facilities with their simplistic and cursory description of U-233 separation from U-238. Such a process would be so difficult due to the presence of U-232 that it simply would not be considered, even by the hypothetical “suicide” operators that they postulate. Anyone who had invested the large sums of money into a uranium isotope separation system would never risk permanently crippling its ability to operate by introducing U-232-contaminated feed into the system.

Proponents claim that thorium fuel significantly reduces the volume, weight and long-term radiotoxicity of spent fuel. Using thorium in a nuclear reactor creates radioactive waste that proponents claim would only have to be isolated from the environment for 500 years, as opposed to the irradiated uranium-only fuel that remains dangerous for hundreds of thousands of years. This claim is wrong. The fission of thorium creates long-lived fission products like technetium-99 (half-life over 200,000 years). While the mix of fission products is somewhat different than with uranium fuel, the same range of fission products is created. With or without reprocessing, these fission products have to be disposed of in a geologic repository.

Again, the authors make blanket statements about “thorium” but then confine their examination to some variant of solid thorium fuel in a conventional reactor. In a LFTR, thorium can be consumed with exceptionally high efficiency, approaching completeness. Unburned thorium and valuable uranium-233 is simply recycled to the next generation of fluoride reactor when a reactor is decommissioned. The fuel is not damaged by radiation. Thus thorium and uranium-233 would not enter a waste stream during the use of a LFTR.

All fission produces a similar set of fission products, each with roughly half the mass of the original fissile material. Most have very short half-lives, and are highly radioactive and highly dangerous. A very few have very long half-lives, very little radioactivity, and little concern. A simple but underappreciated truth is that the longer the half-life of a material, the less radioactive and the less dangerous it is. Technetium-99 (Tc-99) has a half-life of 100,000 years and indeed is a product of the fission of uranium-233, just as it is a product of the fission of uranium-235 or plutonium-239. Its immediate precursor, technetium-99m (Tc-99m), has a half-life of six hours and so is approximately 150 million times more radioactive than Tc-99.

Nevertheless, it might come as a surprise to the casual reader that hundreds of thousands of people intentionally ingest Tc-99m every year as part of medical imaging procedures because it produces gamma rays that allow radiography technicians to image internal regions of the body and diagnose concerns. The use of Tc-99m thus allows physicians to forego thousands of exploratory and invasive surgeries that would otherwise risk patient health. The Tc-99m decays over the period of a few days to Tc-99, with its 100,000 half-life, extremely low levels of radiation, and low risk.

What is the ultimate fate of the Tc-99? It is excreted from the body through urination and ends up in the municipal water supply. If the medical community and radiological professionals intentionally cause patients to ingest a form of technetium that is 150 million times more radioactive than Tc-99, with the intent that its gamma rays be emitted within the body, and then sees no risk from the excretion of Tc-99 into our water supply, where is the concern? It is yet another example of fear, uncertainty, and doubt that Makhijani and Boyd would raise this issue as if it represented some sort of condemnation of the use of thorium for nuclear power.

If the spent fuel is not reprocessed, thorium-232 is very-long lived (half-life:14 billion years) and its decay products will build up over time in the spent fuel. This will make the spent fuel quite radiotoxic, in addition to all the fission products in it. It should also be noted that inhalation of a unit of radioactivity of thorium-232 or thorium-228 (which is also present as a decay product of thorium-232) produces a far higher dose, especially to certain organs, than the inhalation of uranium containing the same amount of radioactivity. For instance, the bone surface dose from breathing an amount (mass) of insoluble thorium is about 200 times that of breathing the same mass of uranium.

Statements like this really cause me to wonder if Makhijani and Boyd understand the nature of radioactivity. Yes, thorium-232 has a 14-billion-year half-life, which means that the radioactivity of thorium is exceptionally low. It will rise as the decay chain of Th-232 begins to form, but it is still at a very low level. To be concerned with the radioactivity of thorium in spent fuel, while neglecting to mention the five billion kilograms of thorium contained in each meter of the Earth’s continental crust again appears to be another example of fear, uncertainty, and doubt levied unfairly against the use of thorium. The buildup of thorium-228 as part of the decay of thorium will happen on a scale within the Earth’s crust so titanically in excess of any activity on the part of man so as to render that point utterly immaterial to any discussion of thorium as a nuclear fuel.

Since both thorium and uranium are natural and common constituents of the Earth’s crust, discussing a bone surface dose obtained by breathing insoluble thorium—a very strange exposure pathway—and contrasting it with uranium is again utterly immaterial to the use of thorium as a nuclear fuel. Do Makhijani and Boyd mean to say that it would be preferable to be breathing uranium instead? The criticism seems to have no structure.

Furthermore, LFTR will not reject thorium to a waste stream nor generate “spent fuel” in the conventional sense. Thorium remains in the reactor until consumed for energy. At shutdown, unconsumed thorium is transferred to the next generation of reactor.

Finally, the use of thorium also creates waste at the front end of the fuel cycle. The radioactivity associated with these is expected to be considerably less than that associated with a comparable amount of uranium milling. However, mine wastes will pose long-term hazards, as in the case of uranium mining. There are also often hazardous non-radioactive metals in both thorium and uranium mill tailings.

Thorium is found with rare-earth mineral deposits, and global demand for rare-earth mining will inevitably bring up thorium deposits. At the present time, we in the US have the strange policy of considering this natural material as a “radioactive waste” that must be disposed at considerable cost. Other countries like China have taken a longer view on the issue and simply stockpile the thorium that they recover during rare-earth mining for future use in thorium reactors. In addition, the United States has an already-mined supply of 3200 metric tonnes of thorium in Nevada that will meet energy needs for many decades. The issues surrounding thorium mining are immaterial to its discussion as a nuclear energy source because thorium will be mined under any circumstance, but if we use it as a nuclear fuel we can save time and effort by avoiding the expense of trying to throw it away.

Research and development of thorium fuel has been undertaken in Germany, India, Japan, Russia, the UK and the U.S. for more than half a century. Besides remote fuel fabrication and issues at the front end of the fuel cycle, thorium-U-233 breeder reactors produce fuel (“breed”) much more slowly than uranium-plutonium-239 breeders. This leads to technical complications. India is sometimes cited as the country that has successfully developed thorium fuel. In fact, India has been trying to develop a thorium breeder fuel cycle for decades but has not yet done so commercially.

Thorium/U233 reactors like LFTR produce sufficient U-233 to make up for U-233 consumed in the fission process. This may be what the authors meant by “breeding more slowly”, but since they consider plutonium a dangerous substance and eschew the use of nuclear power, it is a wonder why they would consider a reactor that does not produce plutonium as having some sort of deficiency. They neglect to elaborate on what sort of “technical complications” this very attractive feature would entail.

The thorium effort in India has been centered around the use of thorium in solid-oxide form, and has suffered from the deficiencies of using this approach, which are transcended through the use of thorium in liquid fluoride form. This is further evidence that the authors are unaware of the implications of the liquid-fluoride thorium reactor.

One reason reprocessing thorium fuel cycles haven’t been successful is that uranium-232 (U 232) is created along with uranium-233. U-232, which has a half-life of about 70 years, is extremely radioactive and is therefore very dangerous in small quantities: a single small particle in a lung would exceed legal radiation standards for the general public. U-232 also has highly radioactive decay products. Therefore, fabricating fuel with U-233 is very expensive and difficult.

Previously I mentioned the implications of the presence of uranium-232 contamination within uranium-233 and its anti-proliferative nature with regards to nuclear weapons. U-232 contamination also makes fabrication of solid thorium-oxide fuel containing uranium-233-oxide very difficult. In the liquid-fluoride reactor, fuel fabrication is unnecessary and this difficulty is completely averted.

Thorium may be abundant and possess certain technical advantages, but it does not mean that it is economical. Compared to uranium, thorium fuel cycle is likely to be even more costly. In a once-through mode, it will need both uranium enrichment (or plutonium separation) and thorium target rod production. In a breeder configuration, it will need reprocessing, which is costly. In addition, as noted, inhalation of thorium-232 produces a higher dose than the same amount of uranium-238 (either by radioactivity or by weight). Reprocessed thorium creates even more risks due to the highly radioactive U-232 created in the reactor. This makes worker protection more difficult and expensive for a given level of annual dose.

The liquid-fluoride thorium reactor has an exceptionally simple and self-contained fuel cycle that has every promise of being less-expensive than today’s wasteful and complicated “once-through” approach to uranium fuel utilization. Makhijani and Boyd try to assign thorium to the wasteful “once-through” fuel cycle, point out deficiencies, and then condemn thorium as having no promise. This might analogous to putting diesel fuel in a gasoline-powered car and then pointing out how deficient diesel fuel is when the car will no longer operate. It is disingenuous and deceptive, and the kindest thing that can be said is that Makhijani and Boyd are ignorant of the implications of the liquid-fluoride thorium reactor and its fuel cycle, which they should not be if they presume to issue a “position paper” such as this.

Finally, the use of thorium also creates waste at the front end of the fuel cycle. The radioactivity associated with these is expected to be considerably less than that associated with a comparable amount of uranium milling. However, mine wastes will pose long-term hazards, as in the case of uranium mining. There are also often hazardous non-radioactive metals in both thorium and uranium mill tailings.

This is a repeat of the issue previously considered, as is immaterial as a factor for or against the use of thorium in nuclear powered reactors since thorium will be mined anyway during the mining of rare-earth minerals. The only question will be whether the mined thorium will be wasted or not.

In conclusion, Makhijani and Boyd fail to consider the implications of the liquid-fluoride thorium reactor on all aspects relating to the benefits of thorium as a nuclear fuel. They fail to consider its strong benefits with regards to nuclear proliferation, since no operational nuclear weapon has ever been fabricated from thorium or uranium-233. They fail to consider how LFTR can be used to productively consume nuclear weapons material made excess by the end of the Cold War. They fail to consider the reduction in nuclear waste that would accompany the use of LFTR. They fail entirely to account for the safety features inherent in a LFTR—how low-pressure operation and a chemically-stable fuel form allow the reactor to have a passive safety response to severe accidents. They fail to account for the improvement in cost that would be realized if LFTRs were to efficiently use thorium, reduce the need for mining fossil fuels, and increase the availability of energy.

Mr. Makhijani and Ms. Boyd should retract this statement in its entirety as flawed and deceptive to a public that needs clear and accurate information about our energy future.

Comments

comments


23 Replies to "Sorensen Rebuttal of IEER/PSR Thorium Paper"

  • q`Tzal
    March 23, 2011 (2:14 pm)
    Reply

    Their website's agenda is quite clear:
    "Carbon-Free and Nuclear-Free"

    While I like the carbon-free portion I can see from their about page, http://www.ieer.org/ieerinfo.html ,

    that they are subject to the knee jerk reaction that nuclear weapons bring and they are applying that passion to anything nuclear.

    In fact a brief look a their subject headers and "accomplishments" show that their strategy is to attack the nuclear industry at every level and stage.
    From mining, processing, transport, in power plants, weapons on to disposal and reprocessing every single stage is a hazard regardless of the scientific facts involved.

  • Steve Packard
    March 23, 2011 (10:37 pm)
    Reply

    Physicians for Social Responsibility is about as low on the scale of trustworthiness as you can get.

    Based on the name one would think that it's a bunch of doctors who are concerned with social policy, education, protection of civil rights and other things which fall under the heading of "social responsibility."

    Nope. It's a single-issue group that is just a standard issue anti-nuclear interest. Not surprisingly, it was founded by Helen Caldicott.

    As for the IEER being for “Carbon-Free and Nuclear-Free”

    Sorry, I can't agree with either of those. I addition to being for nuclear energy, I'm actually made out of carbon and a few other things, in addition to water.

  • Paul C from Austin
    March 24, 2011 (12:54 am)
    Reply

    So, will the IEER publish your rebuttal? If only on the grounds that this could be considered a peer review of the first publication?

  • Frank Kandrnal
    March 24, 2011 (4:44 am)
    Reply

    Ignorant work of those two authors and the people who take their work for granted makes me want to flip my communicator and say: Please Scotty beam me up, there is no sign of intelligent life down here.

  • donb
    March 24, 2011 (12:53 pm)
    Reply

    There are other errors as well. For example:

    Highly enriched uranium and separated plutonium are nuclear weapons materials.
    Just having separated plutonium doesn't mean you have the material to build a bomb. The mix of plutonium isotopes in spent light water reactor fuel is very hard to handle for bomb-making, just like U-233 with U-232 contamination from a LFTR is very hard to handle. Even if one did construct a bomb using the mixed isotope plutonium, its yield would be low since the fission would start before the plutonium reached optimum configuration, blowing the plutonium pieces apart before they release much energy.

    In addition, U-233 is as effective as plutonium-239 for making nuclear bombs. In most proposed thorium fuel cycles, reprocessing is required to separate out the U-233 for use in fresh fuel. This means that, like uranium fuel with reprocessing, bomb-making material is separated out, making it vulnerable to theft or diversion.
    The LFTR designs I have seen have a breeding ratio very close to 1:1. Any U-233 that might be diverted would have to be replaced with U-235 or plutonium to keep the reactor going to get more U-233. Why go through all the bother of running it through a reactor? According to this paper, enriching U-235 from 20% to 95% is rather easy. And plutonium is bomb material. Why not do it the "easy way"?

    If the spent fuel is not reprocessed, thorium-232 is very-long lived (half-life:14 billion years) and its decay products will build up over time in the spent fuel. This will make the spent fuel quite radiotoxic, in addition to all the fission products in it. It should also be noted that inhalation of a unit of radioactivity of thorium-232 or thorium-228 (which is also present as a decay product of thorium-232) produces a far higher dose, especially to certain organs, than the inhalation of uranium containing the same amount of radioactivity. For instance, the bone surface dose from breathing an amount (mass) of insoluble thorium is about 200 times that of breathing the same mass of uranium.
    So am I to understand that there are no decay products of Th-232 in natural deposits? Let's leave aside the fact the thorium will be recycled to use in the same or other reactors. By using the LFTR, we will remove thorium from the environment. The thorium that does escape the recycling process will be in mixed with fission products that will be put in places much more isolated from the biosphere than the thorium was originally.

    Research and development of thorium fuel has been undertaken in Germany, India, Japan, Russia, the UK and the U.S. for more than half a century. Besides remote fuel fabrication and issues at the front end of the fuel cycle, thorium-U-233 breeder reactors produce fuel (“breed”) much more slowly than uranium-plutonium-239 breeders. This leads to technical complications.
    This is a "damned if you do, damned if you don't" argument. If the breed ratio is close to 1:1, then you have "technical complication". If the breeding ratio is higher, then you have a source for bomb material (see above).

    Reprocessed thorium creates even more risks due to the highly radioactive U-232 created in the reactor. This makes worker protection more difficult and expensive for a given level of annual dose.
    This amounts to another "damned if you do, damned if you don't" argument. If the reprocessing works with highly radioactive materials, it is bad. If the reprocessing works with materials that are not highly radioactive, it is bad because diversion is made easier.

    Finally, the use of thorium also creates waste at the front end of the fuel cycle. The radioactivity associated with these is expected to be considerably less than that associated with a comparable amount of uranium milling. However, mine wastes will pose long-term hazards, as in the case of uranium mining. There are also often hazardous non-radioactive metals in both thorium and uranium mill tailings.
    So (for example) coal mining creates no wastes? It does, and those wastes are mostly hazardous stable elements which pose longer-term hazards (i.e., infinite time) than radioactive elements that become less hazardous with time. If one argues for wind or solar, one has to look at all the mining that goes on for the large amounts of materials required. No energy source is hazards free. But some forms of energy (like nuclear) are less hazardous than others (like coal, oil, gas, wind, solar, hydro). And some forms of nuclear (like the LFTR) are less hazardous than others.

  • Bill Hannahan
    March 24, 2011 (3:06 pm)
    Reply

    It is frustrating to deal with people who start with a conclusion and then set out to construct arguments to support their conclusion, no matter how twisted, one sided or superficial those arguments are.

    It is even more frustrating when they claim to be men and women of science, yet they do not understand, or refuse to apply, the most fundamental principle of good science; the requirement to apply logic to all of the facts and to follow those facts wherever they lead, even if it is not where you expected or wanted to go.

    Kirk, thanks for having the patience to air out this document.

  • Greg Simpson
    March 24, 2011 (7:06 pm)
    Reply

    You said: "Today’s reactors use solid-uranium oxide fuel that is covalently-bonded and sustains radiation damage during its time in the reactor. The fluoride fuel used in LFTR is ionically-bonded and impervious to radiation damage no matter what the exposure duration."

    Uranium oxide has ionic bonds, similar to thorium fluoride. The reason the LFTR fuel is impervious to radiation is that it a liquid. The character of the bonds is an unnecessary complication anyway.

    Technetium-99 sound rather toxic. I would think the amounts used in medicine are much smaller than what reactors produce. I would hope that there are plans to either bury it or transmute it to something else. Probably the same applies to iodine-129.

  • James Peter
    March 25, 2011 (4:44 am)
    Reply

    Kirk says: 'Mr. Makhijani and Ms. Boyd may wish to update their document since “Thorium Power” is now called “Lightbridge” and no longer advocates for the use of thorium, whereas the community of supporters of liquid-fluoride thorium reactors (LFTR) still maintains strong support for the use of thorium because it is indeed a solution to the issues of proliferation, waste, safety, and cost that accompany the present use of solid-fueled, water-cooled reactors.

    lightbridge says: 'Uranium-Zirconium Metal Seed and Thorium-Uranium Oxide Blanket Fuel Design
    Lightbridge’s primary thorium-based fuel design incorporates ?-phase uranium-zirconium metal fuel rods in the seed region and thorium-uranium oxide fuel rods in the blanket region. This fuel design offers enhanced proliferation resistance, a significant reduction in used fuel volume and weight (up to 40% and 70%, respectively) and reduced long-term radio-toxicity (90% reduction) of used fuel. The fuel design also provides improved fuel cycle economics, particularly on the back-end. In some earlier technical publications, this fuel design has also been referred to as Radkowsky Thorium Fuel or RTF.

    I am neither a scientist nor engineer, but does this not contradict what Kirk has said about them not promoting the use of thorium?

  • James Peter
    March 25, 2011 (4:49 am)
    Reply

    response to Bill Hannahan's frustration: this is the circular argument, specious according to the rules of logic, that the liberal, progressive, huddite crowd use routinely, in all their flailings against prosperity and freedom. the battle against them will always be presuppositional, which is why it is in the end a religious war. it is their 'givens' against our 'givens'.

  • Bill Thesling
    March 25, 2011 (2:52 pm)
    Reply

    Hi Kirk,

    I'm nit-picking here, but you math is incorrect on one issue. There is not "five billion kilograms of thorium contained in each meter of the Earth’s continental crust". I calculate 38 Billion Metric Tonnes of Thorium there. 7600 times as much !!! (using only 29% of the earth's surface since the rest is covered by water, 2.7 Metric Tonnes of crust per cubic Meter, and 9.6 milligrams of Thorium per Kilogram of crust and 6,371 Km as the radius of the earth)

  • CP
    March 25, 2011 (8:12 pm)
    Reply

    My question is do these guys – Makhijani and Boyd- have any engineering/physics background? If not I do not consider their arguement.

  • Jeff B.
    March 26, 2011 (10:19 am)
    Reply

    These "concerned doctors" are only concerned with their progressive ideology. Their luddite paroxysms would have the effect of condemning billions more to a world without enough energy for quality life, let alone modern medicine.

    The best thing we can do to help the people of the world is to provide an abundant, low cost, smoke free source of energy. Nuclear holds far more density and promise than any ridiculous wind and solar scheme that the "concerned doctors" might propose.

  • Chris Crowe
    March 26, 2011 (9:47 pm)
    Reply

    I do agree with them on one thing – thorium 232 isn't really a fuel, U233 is the fuel. Its symantics really, but defined this way you can defend saying that Th232 is inert (14B year half life makes it inert in my books) and the fuel loading in the reactor is the relatively small mass of U233 floating around in the larger mass of molten salt and thorium. You have to do a lot of work to turn Th into a fissile fuel.

  • Alex Kovnat
    March 28, 2011 (8:49 am)
    Reply

    On the matter of recycling in general: If we Americans are too hung up about plutonium and U-233, I suggest we ship our used nuclear fuel to Russia, China or France and let them recycle and use the resultant plutonium or U-233 in their own nuclear power programs. The only question is, arrangements of who pays what for what. Should we pay Russia, China or France for taking fission product wastes off our hands, or should they pay us for the energy potential of the plutonium or U-233 in our spent nuclear fuel?

    Regarding Thorium in particular, I think that right now we could incorporate a certain amount of Th in existing light water reactors. Regarding safety: With any nuclear reactors we build, no matter what the coolant, no matter what the neutron spectrum (fast or slow), and no matter what the fuel cycle, perhaps we should design them such that even if a total meltdown were to occur, the radioactive content of the reactor would be kept within the containment structure.

  • robit
    March 28, 2011 (3:02 pm)
    Reply

    I second James Peter's comment that Lightbridge is still pursuing the use of thorium as a fuel.

  • JPerez
    March 28, 2011 (6:36 pm)
    Reply

    Thanks for the post. Very informative. I'd be curious of the effects of boron on reducing radiation.
    By the way, here's a bit of levity I found when searching this morning:
    "The Boron Song" sung by a budding female scientist:
    http://www.youtube.com/watch?v=p9rH1_sxwQ4

  • Chris (Robotbeat)
    March 29, 2011 (5:29 pm)
    Reply

    Thorium is a fertile fuel. Just like gasoline, which needs to be turned into a vapor before it burns (though on a longer time scale). Or like vegetable oil in a vegiesel (you start the vehicle on diesel and switch to vegetable oil after the engine warms up…).

    But anyway, I want to ask a question about thorium and rare earths: For each pound of rare earth metal, how much thorium is dug up along with it? Is around 10% as much a good answer? If so:
    From my calculations, the amount of rare earths needed for a wind mill produces approximately the same amount of thorium (as waste!) as would be needed to produce the same amount of electricity as that wind mill would produce over its entire life.

    If we go to an electric car culture, I think that it'd probably work out in a similar way: the rare earths needed for all the electric cars would produce enough thorium (as waste!) to power them for their lifetimes.

    And I once calculated that there should be enough thorium in the top 1 mile or so of the Earth's crust to power thorium reactors until the Sun makes Earth inhospitable to life (>1 billion years). I.E., it's as renewable as any power source on Earth!

  • Van Varenberg
    April 3, 2011 (10:42 am)
    Reply

    Thanks for this really enlighting review !

  • Tanj
    April 3, 2011 (11:56 pm)
    Reply

    Dismissing technetium 99 by comparing it to medical uses seems exagerated and not setting a good example of proper care. It would seem that about 5% of the U-233 will become Tc-99, which is on the order of 10 kg per year for a 1GW LFTR. That is far different than the nano-grams used in a medical test. However, there is no need to panic. It is a beta emitter easily shielded. Although it is the dominant material in wastes by Bq in the 10,000 to 100,000 year time frame, those Bq (which just means nuclei having a radiation event) are pretty wimpy. You could glassify or ceramicize that 10kg in a ton of glass or ceramic, in pellets that would be tough and safe to handle. As the side effect of generating 8Bn kw/hr, which is around $800 Mn of economic value, it seems quite reasonable to expect that such a modest material handling problem could be funded. Note that we already have around 1500 tons of plutonium, and by implication about 75 tons of Tc99 sitting around the USA today. A full Th economy generating 100GW (a lot more than nuclear today) would eventually add up to the same in 75 years – but minus the 1500 tons of Pu239/40 and the 30,000 tons of fuel rods it is mixed into. 75 tons would fill one modest suburban swimming pool, warm but not melted.

    So, it is an issue. It is not trivial, but not insoluble or even particularily frightening. I thoroughly agree with Sorenson's rebuttal but I think it important to keep everything careful and accurate, in proper perspective.

  • Joergen Geerds
    April 7, 2011 (6:36 pm)
    Reply

    CP: I was also wondering about the background of Arjun Makhijani, but he holds a PhD in nuclear engineering: http://www.ieer.org/ieerstaf.html
    I still don't understand his quite unscientific reasoning, I would have expected more from him and his degree… it almost sounds like a biologist turned young-earth creationist.

  • Kirk Sorensen
    April 8, 2011 (9:25 am)
    Reply

    Thanks for the link to Arjun Makhijani's educational background. Interesting note–his "nuclear engineering" degree is in fusion energy, not fission. The technology space is COMPLETELY different. Guys who do fusion never study neutron transport, criticality, reactor control and stability, and all of the other disciplines that give a FISSION nuclear engineer an understanding of his or her machine.

    I doubt many people ask Makhijani with his "nuclear engineering" PhD how much he knows about fission.

  • E.M.Smith
    April 17, 2011 (12:40 pm)
    Reply

    It looks to me like some slight of hand on the "toxics in the mining waste" topic. Thorium is found in some isolated salts, but most of it is things like monzanite sands, that are mined for "rare earth metals" that are, I think, toxic.
    http://en.wikipedia.org/wiki/Neodymium

    "Neodymium dust and salts are very irritating to the eyes and mucous membranes, and moderately irritating to skin. Breathing the dust can cause lung embolisms, and accumulated exposure damages the liver. Neodymium also acts as an anticoagulant, especially when given intravenously."
    http://en.wikipedia.org/wiki/Niobium

    "Niobium has no known biological role. While niobium dust is an eye and skin irritant and a potential fire hazard, elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless. It is frequently used in jewelry and has been tested for use in some medical implants.

    Niobium-containing compounds are rarely encountered by most people, but some are toxic and should be treated with care. The short and long term exposure to niobates and niobium chloride, two chemicals that are water soluble, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show a median lethal dose (LD50) between 10 and 100 mg/kg.] For oral administration the toxicity is lower; a study with rats yielded a LD50 after seven days of 940 mg/kg"

    So as I read their argument they are saying that Thorium is bad becuase it would require that we deal with horrible rare earth toxic elements… Which ignores that we are seaking out those rare earths to make the magnets needed by the "alternative energy" wind turbines and electric car motors… I'm for using both the Thorium and the rare earths.

    Though not with the toxic legacy that China has from it's rare earth mining for the "green" industry:
    http://www.businessweek.com/news/2011-01-06/rare-

    Side notes:

    We have already made Thorium fueled reactors. It isn't a new thing.
    http://chiefio.wordpress.com/2011/04/12/nuclear-r

    "BORAX-IV, built in 1956, explored the thorium fuel cycle and uranium-233 fuel with a power of 20 MW thermal."

    "In addition to the flexible CANDU, there have been other Thorium reactors over the years. Thorium in reactors is not a new concept, just some folks are talking about it again.
    http://en.wikipedia.org/wiki/THTR-300

    The THTR-300 was a thorium high-temperature nuclear reactor rated at 300 MW electric (THTR-300). The German state of North Rhine Westphalia, in the Federal Republic of Germany, and Hochtemperatur-Kernkraftwerk GmbH (HKG) financed the THTR-300’s construction. […] The THTR was synchronized to the grid for the first time in 1985 and started full power operation in February 1987."

    So the notion that it's a hard thing to do and India is "struggling" is just a falsehood. It has been done with several fule forms. India is taking its time as they needed operational reactors to be on line fast and then wanted to go back and add Thorium reactors. It is a schedule issue, not a technical issue. China, BTW, is manufacturing Thorium Pebble Bed reactors on the German design right now. We, globally, ARE going onto the Thorium fuel cycle. Just not in the west…

  • Larsson
    May 14, 2011 (5:24 pm)
    Reply

    I'm an academic without any background in nuclear science. I'm in favor for green energy and I'm considering to include LFTR to my list for sustainable energy sources. I've done my homework on liquid thorium reactors, both for and against, but I've still got some questions.

    My questions to you proponents are:

    1. What are the downsides?

    2. Assuming an accident. What would happen?

    3. Please give me some worst case scenarios?

    I know the potential benefits of LFTR, I've read the comparisons with light water reactors, fossile fuels and I do understand why relying solely on wind/water/sun is unrealistic today. Claiming that there are no downsides to thorium reactor technology is not an answer. Also, a situation that is saved by the freeze plug is not really an accident and definitely not a worst case scenario.

    That is; Straight answers much appreciated.

    Thanks
    L.


Leave a Reply