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PostPosted: Jan 10, 2007 9:49 am 
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WNA News Briefing 07.02 (4 – 9 January 2007)
[NB07.02-13] India: Construction of the country's first advanced heavy water reactor (AHWR), using a thorium fuel cycle, will reportedly start during 2007. Anil Kakodkar, head of India's Department of Atomic Energy (DAE), has stated that a pre-licensing review of the new 300 MWe reactor is currently being undertaken by the Atomic Energy Regulatory Board. The location where the reactor will be built has yet to be announced. (Ux Weekly, 8 January, p3; see also News Briefing 03.40-13)


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PostPosted: Jan 10, 2007 10:30 am 
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Very interesting news--I think this will be one of the largest thorium reactors built up to this point. Do the Indians plan to reprocess the fuel, and is the core flux low enough to enable a conversion ratio greater than or equal to unity?


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PostPosted: Jan 10, 2007 11:29 am 
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According to IAEA-TECDOC-1450, "Thorium fuel cycle — Potential benefits and challenges," the discharge burnup of the fuel is in the range of 20–24 GWd/tonne.
That's pretty low for fuel that has a U233 enrichment of 3.75% and 3%, and 3.25% Pu (there are 452 "fuel clusters," with each one containing 2.3 kg U233 and 1.75 kg Pu).
So they had better reprocess the SNF, with such valuable fuel & low burnup.


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PostPosted: Jan 10, 2007 12:33 pm 
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Oh, so there's a bunch of U-238 in the fuel. In that case they won't be hitting a CR of 1.0, at least not in a highly-thermalized spectrum like an HWR.


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PostPosted: Jan 10, 2007 1:31 pm 
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Kirk Sorensen wrote:
Oh, so there's a bunch of U-238 in the fuel.

Sorry for the confusion -- no, it appears that all the rest is Th (note that I didn't mention U235, which would more clearly imply the presence of U238, when using the term "enrichment").


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PostPosted: Jan 10, 2007 10:06 pm 
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In that case, they might do quite well on the conversion ratio. The presence of plutonium will complicate things, since it's rather messy in a thermal spectrum and formed lots more TRUs (Pu-240, Am-241, Cm-242, etc.)

Wish we could get them turned on to fluoride reactors.


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PostPosted: Jan 14, 2007 3:14 pm 
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I guess no-one has told the Indians about MSRs and fluoride salt processing.....

Quote:
http://www.dae.gov.in/publ/3rdstage.pdf
Shaping the Third Stage of Indian Nuclear Power Programme
<snip>
In order to support fuel cycle of AHWR, several technologies have to be brought to a level of maturity, and some new ones need to be developed.
[....]
The back-end of the fuel cycle is being developed to work out technologies to cater to the special challenges associated with thorium based fuel. Thorium dioxide, or thoria, is a very inert material and one of the major challenges is to make it dissolve, during the spent fuel reprocessing operations. Encouraging results have been obtained in laboratory experiments done at BARC to find a solution to this problem. Programmes have been identified, as a part of the third stage activities, to reach a desirable goal of using all the fissionable materials in the fuel cycle very efficiently while minimising the radiological toxicity of the waste stream.


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PostPosted: Jan 15, 2007 1:22 pm 
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Yeah, thorium dioxide is an exceptionally stable substance. About the only form of thorium even more stable is thorium tetrafluoride.

One of the basic challenges for the other two fluid-fueled reactors that were put forward in the 1950s (the aqueous homogeneous and the bismuth-metal reactor) was the lack of a suitable fluid form of thorium for the blanket. They both had to rely on thorium dioxide in a suspension or a slurry. Functionally, they could figure out ways to pump it around, but when it came to reprocessing, they still have to deal with thorium the same way a solid-fueled reactor would have to.

THOREX was the preferred method for thorium reprocessing in the solid-fueled reactors and in those two fluid-fueled reactors.

But the fluoride reactor was unique in that it could hold thorium in a fluoride form, dissolved in other fluorides, and that the necessary reprocessing steps could be accomplished without changing the chemical form of the thorium.

This is from the summary of TID-8507: The Report of the Fluid-Fueled Reactors Task Force, February 1959, pg 4:

1. The technical feasibility of fuels and materials is a critical factor. At the present state of technology, the MSR has the best possibility of obtaining a satisfactory fuel, if indeed it does not already have a satisfactory fuel. Slurries, as used by the LMFR and AHR require a greater amount of development effort to establish feasibility.The MSR also offers the best possibility for achieving a satisfactory container material since the LMFR and the AHR have difficult materials problems at the present stage of technology. However, the compatibility of molten salt fuel with graphite which is contemplated for use for the internal construction of a reactor still remains to be demonstrated and the problem is judged to be more severe than in the LMFR.

Subsequent to this report in 1959, the MSRE was built and operated from 1965-1969 and conclusively showed that graphite could be compatible with fluoride salts under reactor-type conditions.


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PostPosted: Feb 09, 2007 11:39 am 
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I guess no-one has told the Indians about MSRs and fluoride salt processing.....


Can U Plz Clear In detail on how can MSR Technology be better tha what used by india ?


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PostPosted: Feb 09, 2007 12:44 pm 
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I'm not as expert as Kirk Sorensen, but I'll give it a try.

1. It's safe to operate and maintain: Molten fluoride salts are mechanically and chemically stable at sea-level pressures at intense heats and radioactivity. Fluoride combines ionically with almost any transmutation product, keeping it out of circulation. Even radioactive noble gases come out in a predictable, containable place, where the fuel is coolest and most dispersed, the pump bowl.

2. A molten salt reactor's fuel can be continuously reprocessed with a small adjacent chemical plant. The requirement is a 4-meter-tall molten niobium column to separate proactinium from the fuel salt, and a small vapor-phase fluoride-salt distillation system to remove fission waste products. The amounts involved are about 80kg of waste per year per GW generated, so the equipment is very small. A sparge of fluorine will even remove U233 from the salt. There has to be a small storage facility to let the proactinium from the niobium column decay to U233. A very small reprocessing facility will service a large 1Gw power plant.

3. With continuous reprocessing, a fluid-salt-fueled reactor has >97% burn-up of fuel. This is -very- efficient, compared to -any- system, -anywhere-.

4. The molten-salt-fueled reactor operates much hotter than LWR reactors, near 900C, so that very efficient Brayton cycle (turbine) generators are possible. This is -also- -very- efficient, a -goal- of so-called generation IV reactors. MSRs have -already- reached this goal.

5. MSRs work in small sizes, as well as large, so a utility could easily build several small reactors (say 100Mwe) from income, reducing interest expense and business risks.

6. Molten salt fuel reactors are not experimental. Several have been constructed and operated at high temperatures for extended times, with simple, practical validated designs. There's no need for new science at all, and very little risk in engineering new, larger or modular designs.

Combining 3 to 6, a molten-salt thorium breeder is the most efficient well-developed way of converting a fuel metal into electricity.

7. Extensive validation (fuel rod design validation normally takes -years- and prevents effective deployment of new nuclear technologies) is not needed. The fuel is molten, chemical reprocessing eliminates reaction products, and there are tested fuel mixtures.

8. There's no need for fuel fabrication. This makes the reactors even cheaper to operate. It poses a business challenge to the industry, because reactor manufacturers are customarily paid by fuel fabrication profits. A government agency could, however, type-license a design, and license it to utilities.

9. Molten-fuel reactors can be made inherently safe: Tested fuel-salt mixtures have negative reactivity coefficients, so that they decrease power generation as they get too hot. Most fuel-salt reactor vessels also have a freeze-plug at the bottom that has to be actively cooled. If the cooling fails, the fuel drains to a subcritical storage facility.

10. Continuous reprocessing reduces numerous reactor design issues. For example, the poisoning effects from Xenon-135 are not present. Neutron poisoning from fission products can be continuously mitigated.

11. A fuel-salt reactor is mechanically and neutronically simpler. There are only two items in the core: fuel salts and moderators. This reduces concerns with moderating interactions with positive void coefficients as water boils, chemical interactions, etc.

12. Coolant and piping need never enter the high-neutron-flux zone, because the fuel is used to cool the core. The fuel is cooled in low-neutron-flux heat-exchangers outside the core. This reduces worries about neutron effects on pipes, testing, development issues, etc.

13. The salt distillation process means that chemical separation and recycling of fission products, say for nuclear batteries, is actually cheap. Xenon and other valuable transmuted noble gases separate out of the molten fuel in the pump-bowl. Any transuranics go right back into the fuel for burn-up.

I personally think that a molten chloride fast thorium breeder might be even more efficient, but that is not proven.

Don't confuse molten-salt-fueled reactors (MSFR) with molten-salt-cooled reactors (MSCR), a Gen IV proposal. The MSCR can't reprocess fuel easily and has fuel rods that need to be fabricated and validated, delaying deployment by up to twenty years from project inception.

There are some advantages from Thorium fuel, that the India project might capture:

14. The thorium fuel cycle produces almost no (theoretically none) long-lived transuranic wastes. The fission wastes are less radioactive than natural ores in 300 years. The India proposal may get this, but only by adding a large, expensive fuel reprocessing factory.

15. Thorium can resist proliferation. An easy variation of the thorium fuel cycle contaminates the Th232 fuel with chemically inseparable Th230. The Th230 breeds into U232, which has a powerful gamma emitter in its decay chain (Tl-208) that makes the reactor fuel U233/U232 impractical in a bomb, because it harms electronics.

16. Thorium is more abundant than uranium, especially in India.


Last edited by rgvandewalker on Feb 12, 2007 11:44 am, edited 1 time in total.

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PostPosted: Feb 09, 2007 7:42 pm 
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That's a fantastic description Ray! I would love to use that in a "frequently asked questions" section or something like that...


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PostPosted: Feb 11, 2007 12:09 pm 
Thank You sir.


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 Post subject: Feel free to use it.
PostPosted: Feb 12, 2007 11:39 am 
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Thanks to whomever cleaned-up the inaccurate isotope numbers in my original text. (Mr. Moderator?) Anyway, I gladly release my contribution's copyright under the GPL.


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 Post subject: Great Description!
PostPosted: May 03, 2007 8:04 pm 
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Hi Ray,

I've just started to look around this forum, and have found it very informative. I wanted to say how much I liked your summary.

You know, it seems to me that an article based around that summary for the popular science press (e.g. popular mechanics) would be a great idea. Despite my reasonable proximity to the field (my dad was a nuclear engineer at GE for 20 years), I had the erroneous idea that the nuclear field has been in suspended animation for 30 years. I have been pleasantly surprised over the past couple of years to find out how many very interesting concepts have been proposed of late.

In short, I think it would be a good idea to get the public excited about the recent technological advances, with the hopes eventually of getting more support for the technology.

Best regards, Honzik

PS. I think the efficiency thing is particularly striking. At first glance I dismissed this as unimportant, after all, nuclear reactions can produce a lot of heat cheaply, so why worry about efficiency? After I thought a bit more about this, I realized that a jump in efficiency from 33% to 50% is huge. A 1 gW plant at 33% efficiency dumps 2gW of heat flux into the environment, while a plant with 50% efficiency dumps 1 gW of heat flux . That means that the efficient reactor needs half the cooling machinery (e.g. towers) all things being equal. (And things are not equal, because it is possible to dump heat at a higher temperature with the MSBRs; this makes it possible to dump the heat more effectively). Secondly, 2 gW of power versus 3 gW of power means that 33% less nuclear waste is being produced, again, all things being equal. (And, again, things aren't equal because MSBRs don't produce a lot of waste to being with.)

All said, this is quite simply fantastic!


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PostPosted: Aug 21, 2007 6:38 pm 
jaro wrote:
I guess no-one has told the Indians about MSRs and fluoride salt processing.....


I wonder if the choice of reactor type is tied to using imported fuel and non-proliferation controls, and the form of fuel that other countries are willing export to India. Thorium oxide mixed with plutonium and uranium oxides are supposedly difficult to process due to chemical stability of thorium oxide the radioactive decay components of the small amount of U232 produced. Maybe this was discussed with the US beforehand, and it was agreed that the US would be willing to accept the export of this. The agreement certainly doesn't look like one that India and the US suddenly came up with out of the blue.

I think the political dynamics of the agreement is that India probably will have enough plutonium for it's weapons needs in a few years, and it will pursue that anyway and the US realized there is nothing the US can do about it. However for civil nuclear power generation it will take maybe 30-40 years at least for India to build enough of a stockpile of U233 for it's thorium based civil power generation needs. If India cannot secure it's growing energy needs from nuclear generation, then it will need to cosy up to oil producers like Iran, and Russia to secure supplies, and this will oblige India to side with those countries rather than US on international issues. I think the US is therefore very keen from strategic considerations, on the nuclear export deal to ensure India's energy independence from countries potentially hostile to the US. A secondary factor is India's greenhouse gas generation capability without nuclear generation. The fact that Thorium U233 based reactors are proliferation resistant and India's agreement to international inspections for those reactors supplied with imported fuel means the US does not lose anything in terms of weapons proliferation prevention compared to the position if there was no deal.


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