Discussion > Thorium question
Please post a working link, EM, and I may try to read it.
michael hart
EM - as mh pointed out your link is incomplete.
I'm well aware that there have been proposals for using accelerators to generate neutrons to produce fission without a chain reaction. And using the energy released to drive the accelerator itself and with surplus available for general consumption.
These seem to be proposals worded with breathless enthusiasm but with key considerations glossed over.
I think the following is probably the sort of thing have in mind:
http://www.ithec.org/Links/Rubbia_ADS.pdf
Does it give any estimates of the ratio of (A) the power needed to drive the accelerator, relative to (B) the power likely to obtained as output electrical power via conventional turbo alternators? If it does, and if A < B, please identify where the error in their working is to be found.
At present these are interesting ideas but no more to be taken seriously than Dan Dare's use of monatomic hydrogen as rocket fuel.
Martin A
EM link is somewhat of a problem to this site's reprint of the address, I'll try it as a quote but then you have to cut and paste to get to it. -
http://mragheb.com/The%20Fusion%20Fission%20Thorium%20Hybrid.pdf
Another link for some up-to-date information on thorium reactor is at -
http://www.world-nuclear.org/info/Current-and-Future-Generation/Thorium/
I'm just a interested bystander in this debate...
tom0mason
There was a brief discussion of thorium-based energy generation on Unthreaded about a month ago, which mentioned a UK effort, ThorEA. ThorEA's approach is use accelerated protons to create neutrons to start the thorium reaction.
More information here and here.
To Martin A's question about energy input, this article suggests a 20 MW accelerator is required for a 600 MW generator.
HaroldW
HaroldW - if those figures are to be believed, then it's an interesting possibility, making it worth reading up.
One might still ask why go to the expense of building, maintaining and providing the power for a 20MW accelerator to produce neutrons, when with a chain reaction, no externally provided neutrons are needed.. The only real benefit I could see stated in the Guardian article was that the reactor could easily be stopped instantly. (I had a feeling of witnessing the phenomenon of science grant chasing in action....)
"It's still nuclear fission, but a crucial safety difference between a conventional nuclear reactor and an ADSR is that in the latter the reaction operates at subcritical levels: it is not self-sustaining. So in the event of a problem, all the operator has to do is switch off the proton beam. Almost immediately, the reaction will cease."
"A crucial safety difference"? I don't think reliably stopping the chain reaction in a conventional reactor presents any real difficulty.
And decay heat from fission products will continue to be generated at a rate proportional to the power level of the reactor irrespective of whether its neutrons came from an external source or from the reactor's own fission. So their statement "Almost immediately, the reaction will cease", whilst not untrue, is definitely misleading.
_______________________________________________________________________
In reading up on thorium power over the past few days, I came across a couple of informative, readable and apparently authoritative papers.
"Liquid Fluoride Thorium Reactors" R Hargreaves and R Moir
Thorium Fueled Underground Power Plant Based on Molten Salt Technology" R W Moir, E Teller
Martin A
Question: Is Thorium the answer?
Answer: Only if we first get honest about nuclear energy!
History:
1. In 1905 Einstein [1] reported that mass (m) is stored energy (E), E = mc^2.
2. In 1913 Bohr [2] concluded mass is concentrated in 0.0000000000001% of the atomic volume.
3. In 1922 Aston [3] reported "powers beyond the dreams of scientific fiction" in the atomic nucleus.
4. In August 1945, energy released from cores of U and Pu atoms destroyed Hiroshima and Nagasaki.
5. In August 1945, did Japan explode an atomic bomb? Did USSR troops capture Japan's facility [4]?
6. After the United Nations was formed (Oct 1945) experimental evidence was hidden that showed [5]:
_ a.) Neutron repulsion is the source of energy in cores of heavy atoms and stars
_ b.) The Sun made our elements, birthed the solar system and sustains our lives
_ c.) Iron-56 is the most abundant and most stable atom in the Earth and the Sun
References:
1. A. Einstein, “Zur Elektrodynamik bewegter Korper” [“On the Electro-dynamics of Moving Bodies”] Annalen der Physik 17 (1905) 891; “Ist die Trägheit eines Körpers von seinem Energie-gehalt abhängig?” [“Is the Inertia of a Body dependent on its Energy-Content?”] Annalen der Physik 18 (1905) 639.
2. N. Bohr, "On the constitution of atoms and molecules," Philosophical Magazine 26, issue 151 (July, 1913): http://www.tandfonline.com/doi/abs/10.1080/14786441308634955
3. Francis William Aston, “Mass spectra and isotopes, Nobel Lecture," (12 December 1922):
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1922/aston-lecture.pdf
4. "Japan Developed Atomic Bomb; Russians Grabbed Scientists," The Atlanta Constitution Headlines (October 3, 1946): http://tinyurl.com/my5zsty http://tinyurl.com/n3agdan
5. Oliver K. Manuel, A Journey to the Core of the Sun - Chapter 2: Acceptance of Reality
https://dl.dropboxusercontent.com/u/10640850/Chapter_2.pdf
The 69-Year Puzzle: https://dl.dropboxusercontent.com/u/10640850/A_69_Year_Puzzle.pdf
Oliver K. Manuel
Martin A
Having watched the links posted by Adrian (thanks for those Adrian) and skimmed through some of the document links, it seems to me that tour question regarding the remaining radioactivity should be available somewhere. One of the issues with Thorium reactors is creation and removal of Protactinium
Wiki says:
Two major protactinium isotopes, 231Pa and 233Pa, are produced from thorium in nuclear reactors; both are undesirable and are usually removed, thereby adding complexity to the reactor design and operation. In particular, 232Th via (n,2n) reactions produces 231Th which quickly (half-life 25.5 hours) decays to 231Pa. The last isotope, while not a transuranic waste, has a long half-life of 32,760 years and is a major contributor to the long term radiotoxicity of spent nuclear fuel
It also says
Twenty-nine radioisotopes of protactinium have been discovered, the most stable being 231Pa with a half-life of 32,760 years, 233Pa with a half-life of 27 days, and 230Pa with a half-life of 17.4 days. All of the remaining isotopes have half-lives shorter than 1.6 days, and the majority of these have half-lives less than 1.8 seconds. Protactinium also has two nuclear isomers, 217mPa (half-life 1.2 milliseconds) and 234mPa (half-life 1.17 minutes).
So it looks like 231Pa is the longest lived of the unwanted by products. I'm unclear how much would be produced if, for instance, the EU decided to produce 50% of it's electricity using Thorium. Although it's unlikely we'll find out the answer that question in my lifetime.
232U is also produced and wiki says this
Uranium-232 has a relatively short half-life (68.9 years), and some decay products emit high energy gamma radiation, such as 224Rn, 212Bi and particularly 208Tl.
The high energy gamma radiation (224Rn?) might be an issue, I haven't looked deeply into though.
The other thing that all references seem to agree on is that there is a lot of Thorium available, and the West hasn't done much research in recent decades. Concentrating on technologies with military applications seems to have, unsurprisingly, driven research for both sides in the Cold War.
Have you found anything on the waste issue?
SandyS
Forgot to add I found this reference too
Irradiated Thorium is more dangerously radioactive in the short term. The Th-U cycle invariably produces some U-232, which decays to Tl-208, which has a 2.6 MeV gamma ray decay mode. Bi-212 also causes problems. These gamma rays are very hard to shield, requiring more expensive spent fuel handling and/or reprocessing.
Now a key question which I don't know is if say the amount of electricity produce using Thorium was several times greater than current nuclear output where the "breakeven" point is.
SandyS
Sandy S
Thanks for that. I found pretty much what I originally asked for. Figure 6 in this paper shows more or less what I was asking for.
I was (still am) interested in forming an opinion on nuclear power via thorium. There seem to be plenty of enthusiasts singing its praises but I have a feeling it is being oversold to some extent. That is, despite some potential advantages, some challenges and dangers may be being understated.
Radioactive wastes from nuclear reactors can be divided into two groups:
[A] Radioactive fission products resulting from the fission of fissile elements to obtain energy.
[B] Transuranic elements with atomic numbers greater than 92, (plutonium, americium, curium, ...), produced mainly by neutron bombardment of uranium 238. The transuranic elements are generally longer lived and even nastier than the radioactive fission products.
Here are the results I have found, comparing light water uranium reactors (LWRs) and molten salt thorium reactors (MSRs). I'm not drawing conclusions at present.
[1] The fission products that need to be disposed of are pretty much the same for LWRs and MSRs, both in quantity and properties. (Because the fissile elements are U-235 and U-233 respectively with about the same energy and spectrum of fission products for each fission.) (Much the same if the LWR also uses Pu-239 from reprocessing.)
[2] The transuranic elements are produced in much greater quantities in LWRs because of the U-238 which is present, which serves no useful purpose but which is transmuted into transuranics by the neutron flux present.
In principle, transuranic elements can be extracted by reprocessing spent fuel and then consumed in LWRs (they are all fissile). But there are arguments against doing so, including nuclear weapon proliferation risks. I think the realistic assumption is that this will not happen, if only because of the costs.
[3] I believe that is generally proposed to extract fission products from MSRs on-site. Doing so routinely in a power station environment will present engineering, organisational, security and operational challenges. It's not obvious to me that they can be solved. (I have visions of Homer Simpson at his place of employment, plus memories of the Sellafield reprocessing mishaps despite Sellafield being at one time the jewel in the crown of the fuel cycle).
[4] I think that the engineering challenges of high power MSRs (such as corrosion issues, maintenance in a radioactive environment, eventual decommissioning) will be great and may take decades to resolve and then to demonstrate their use in production environments.
Martin A
Martin A -
First, thanks for those links of a few days ago (Apr 26 at 11:11 AM). I think your points are well-taken. The main advantage seems to be in waste management, with less waste by volume and a relative paucity of the longer-lived isotopes. However, there still remains a storage problem requiring centuries to wait out the decay of the most common fission products. And I didn't see any discussion of how to convert the waste into store-able units. One would think it's more involved than just opening a tap, draining the liquid into empty tubes and sealing the tops.
I don't know whether your assessment of decades to solve the various engineering problems is accurate, pessimistic, or optimistic. The fact that a thorium reactor has been operated successfully in the past (albeit on a smaller scale) is a plus. The thorium challenges seem to be of the sort which can be overcome with persistence and evolutionary improvements. As opposed to, say, large-scale energy storage for intermittent generators (solar, wind) which seems to require novel breakthroughs.
HaroldW
I posted a query on a thorium reactor discussion group asking whether using an external accelerator made any sense, since a thorium reactor can perfectly well produce its own neutrons without the expense of an external accelerator.
http://energyfromthorium.com/forum/viewtopic.php?f=3&t=4380
The response was pretty well unanimous that the idea makes not sense at all. My two favourite replies were:
"It is a great idea if your specialty is accelerators and you need a new reason for the government to continue your funding"
"Somehow the accelerator driven reactors brings up an image of a huge windmill ventilating a coal furnace. Could be technically feasible but absolutely pointless."
Martin A
Nice graphic here.
http://krausreportingforduty.com/an-ohio-long-term-energy-plan-thorium/
Adrian
THORIUM reactors cannot safely harvest nuclear energy if designed, built and operated by engineers and technicians who have been educated with textbooks published after the Second World War, in which
1. F. W. Aston's rigorously valid equations for nuclear stability based on "nuclear packing fractions" have been replaced by
2. von Weizsacker's invalid equations for nuclear stability based on "nuclear binding energy equations."
Textbooks were changed immediately after WWII to hide from the public the source of energy (NEUTRON REPULSION) that destroyed Hiroshima and Nagasaki [1].
1. Oliver K. Manuel, A Journey to the Core of the Sun - Chapter 2: Acceptance of Reality
https://dl.dropboxusercontent.com/u/10640850/Chapter_2.pdf
The 69-Year Puzzle: https://dl.dropboxusercontent.com/u/10640850/A_69_Year_Puzzle.pdf
Oliver K. Manuel
May 3, 2014 at 7:13 Adrian
Yes, Interesting graphic (and impressive and lucid sales pitch by the attractive presenter in the video).
Nuclear power is with us and it makes sense to look for improvements. I've an open mind on whether liquid salt reactors fueled with thorium or with uranium will be improvement over conventional reactors when all of the costs, risks and benefits are factored in.
The graphic and the sales pitch have (for me) the air of understating the costs and risks of thorium based reactors. But nobody expects a sales pitch to say "here is a list of reasons why you should think twice about buying our product".
Martin A
Don't disagree Martin A.
They key (and hence hugely significant) differences with a LFTR are that there is never any 'coolant' in a proper sense, to be lost from the primary circuit; and that the entire reactor runs as atmospheric pressure (no need for secondary containment, as there is no phase change is in current PWRS after a loss of coolant). And it is 'walk away' safe. The wet chemistry is horrible - key parts of the research still be done - all materials science.
But, we have, literally multiple thousands+ of years of the stuff available, and the waste out the other end represents a solvable engineering/geology problem, unlike the current once thru PWR fuel cycle.
We'll be buying them, modular, from the Chinese in a few decades.
Reliable, low CO2 baseload, which can also do load following, walk away safe. Any Greenie with a science degree should be gagging for it. Oh....
Adrian
I am truly in awe of the knowledge of members in this thread so how do I manage to insert a "Dung was 'ere" without appearing to be a total idiot? Humph!
Well I read Robert Zubrin's book Merchants of Despair, he has a PHD in nuclear engineering so I think I am OK to quote him here. Zubrin estimates that there is enough Thorium to power the world for 10,000 years and enough Uranium for another 4,000 years. On these time scales man will easily have discovered many more ways to extract energy from various other sinks.
Thorium offers a safety blanket to last us until; we find a fuel that bloody environmentalists can not argue with ^.^
Dung
Martin A
Did you read my link?