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PostPosted: Apr 16, 2013 11:49 pm 
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Cyril R wrote:
Owen T wrote:
Cyril R wrote:
Delayed neutrons are important for solid fuelled reactors. For fluid fuel reactors with instant fast negative terms (faster than delayed neutrons time constant) it's not clear that it is all that vital.

The solubility of trifluorides (TRUs all occur as trifluorides) is limited in fluoride salts. This becomes a problem at some point for most reactors, though lower power density reactors can run a long time before this becomes an issue.


Thermal reactors need much lower fissile loading so solubility should be less limiting. I realize that this is all just qualitative generalizations rather than actual quantitative analysis but it seems that the "you need fast neutrons to burn TRUs" claim is not so clear cut.


That's true. In many ways, TRUs are more attractive in thermal reactors, especially if breeding isn't necessary. A thorium DMSR with TRU feed is an effective destroyer of TRUs whilst producing high quality U233 that can be recovered for future LFTRs (yet safeguarded by U232 and fission products in the meanwhile).


If the added fissile is TRU rather than LEU then it is not a DMSR any more. It is not just the lack of U238 to denature. There is a more fundamental difference. In a DMSR you would want to maximize breeding within the limits of the simple one fluid reactor. This saves on fissile. In a TRU burner you would want to minimize breeding - just enough for the reactor to behave nicely. TRUs are not "free fuel" -they are messy and expensive to handle. Presumably someone is paying you to burn them or you wouldn't bother. In that case you want to maximize fiszile burned and minimize breeding. This means excess neutrons. What can you usefully spend these neutrons on? Simpler processing, of course. Carrier salt moderator and structural materials with higher absorption but other desirable properties. Anything else?


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PostPosted: Apr 17, 2013 1:43 am 
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There is no reason one has to go to one extreme or the other. Excess neutrons means more damage to your structure. Use the TRUs en masse with thorium in the fuel salt to get the reactor started and burn off a bit more in the early years to build up an inventory of 233U. Then feed with thorium to burn off most of the plutonium before cleaning the salt after 10 years.


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PostPosted: Apr 17, 2013 1:59 am 
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Quote:
In a TRU burner you would want to minimize breeding - just enough for the reactor to behave nicely. TRUs are not "free fuel" -they are messy and expensive to handle. Presumably someone is paying you to burn them or you wouldn't bother.


These statements don't add up. If you don't breed (ie no or very little fertile) then you must add more of the expensive TRU makeup (a TRU fed Th reactor gets most of the energy from thorium-U233). The fuel cycle cost would be so high, no one would bother buying your expensive electricity. That means no investors. It's dead in the water. Purely academic, which is what it'll remain.

I don't want to wait for someone like a government to pay for the TRU burning. Because we can wait forever.

I'm more interested in a reactor that is good at a lot of things. Good at making electricity, good at not making too much TRUs, good at disposing of TRUs if and when needed, good in terms of ease of development, simplicity, etc. We have to zoom out and look at the whole field of play. Reactors that are too specialized don't stand a chance.

The converter reactor is that cookie-cutter reactor. We can get started on a LEU uranium burner, then later with the option of TRUs with thorium.


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PostPosted: Jun 14, 2013 8:38 am 
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A common approach to filing patent applications in multiple countries is the PCT, one aspect of which is publication of the application 18 months after the priority date. The fact that 18 months came and went with no PCT publication of the Transatomic application suggested that the application had been filed only in the US. This is/was quite counter intuitive.

Well, the application has published as a PCT (19 months after the priority date)
http://worldwide.espacenet.com/publicationDetails/biblio?DB=EPODOC&II=1&ND=5&adjacent=true&locale=en_EP&FT=D&date=20130530&CC=WO&NR=2013077941A2&KC=A2

Thus, we can expect that the application will be filed broadly.

Art Williams


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PostPosted: Jan 03, 2014 12:25 pm 
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More examples of prior art that would affect the patentability of a hydride-moderated molten-salt reactor.

From page 92 of ORNL-2221 (March 1957):

Quote:
ADVANCED REACTOR DESIGN

Preliminary design work has been done on advanced reactor concepts along the lines described previously, with the objective of achieving an aircraft reactor system that is simpler than the ART system and which will operate at a higher temperature. Efforts toward simplification have been based upon the concept of a reactor in which the circulating fuel cools the moderator. As stated previously, if the fuel is to accept heat from the moderator, the moderator must be at a higher temperature than the fuel. Thus beryllium metal cannot be used as it is in the ART for the moderator because of problems of containing it and because of its poor mechanical properties at temperatures above the fuel temperature of interest, that is, 1750°F. Graphite, beryllium oxide, and the hydrides of zirconium and yttrium are being considered as possible moderators.


From page 93 of ORNL-2221:

Quote:
REACTOR CONFIGURATIONS

Two reactor configurations that are now being studied can be used to illustrate the problems. The design presented in Fig. 1.7.2 is comprised of rods of hydride placed in the core on uniform equilateral centers. The rod diameter is increased with radial distance from the center of the core in order to obtain a uniform power density in the fuel and to reduce the gamma-ray heating power density near the core boundary so that relatively large-diameter rods can be used in the reflector. The fuel volume at the outer periphery of such a core would be reduced to a minimum of 9 vol %, as is characteristic of close-packed cylindrical rods. The reflector would be poisoned in the region radially outward from where close packing began. The poisoning additions would be made so that fissioning would be suppressed to a level such that, at any given radius, the virgin neutrons from the region would have little effect on the radiation escaping from the shield or on the activation of the secondary fluid in the heat exchanger.


From page 94 of ORNL-2221:

Quote:
While yttrium hydride would be the logical choice for the moderator, the absence of physical property data made it necessary to presume zirconium hydride, for which some data are available (see Table 1.7.2 in following section).


From page 96-97 of ORNL-2221:

Quote:
It is evident that the hottest point in a ZrH- or YH-moderated reactor with 0.5-in.-dia moderator rods will be about 300°F above the mixed mean fuel temperature if there is a good thermal bond between the cladding and the hydride. If the bond is not good and is replaced by a hydrogen-filled gap, the temperature drop will be about 60°F per mil of gap. From Fig. 1.7.9 (see below) it appears that the gap thickness that might be induced by differential thermal expansion would be less than 0.001 in. for 0.5-in.-dia clad rods.


From page 98 of ORNL-2221:

Quote:
Apart from the possible hydrogen losses by the hydride, the damage or ill effects which would be expected to present problems in the use of any particular high-temperature moderating material will arise primarily from thermal effects, that is, differential expansion between the moderator and the can caused both by differences in coefficient of expansion and by differences in temperature, since the temperature of the moderator will be higher than that of the can.


From page 100 of ORNL-2221:

Quote:
The hydride specimens must of course be sealed to retain the hydrogen.


Attachments:
ORNL2221_tab1-7-1.gif
ORNL2221_tab1-7-1.gif [ 52.02 KiB | Viewed 853 times ]
File comment: Cross Section Through Core of Hydride-Moderated Circulating-Fuel Reactor.
ORNL2221_fig1-7-2.gif
ORNL2221_fig1-7-2.gif [ 75.98 KiB | Viewed 854 times ]
File comment: Schematic Layout of a 180-Mw Hydride-Moderated Circulating-Fuel Reactor with a 21-in.-dia Core.
ORNL2221_fig1-7-3.gif
ORNL2221_fig1-7-3.gif [ 271.42 KiB | Viewed 855 times ]
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PostPosted: Jan 03, 2014 2:56 pm 
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Thanks.


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PostPosted: Jan 31, 2014 7:35 am 
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Transatomic is certainly free to attempt to use zirconium hydride moderator but I doubt they can patent it.


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PostPosted: Jan 31, 2014 10:11 am 
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That depends on whether the patent examiner becomes aware of the prior ORNL work.
Otherwise, TAP gets a patent that they have difficulty to defend but it still serves as a deterrent for others who want to go down the same road. One effective strategy we have used in the past is to send such information to the patent law firm submitting the patent (if you can find out who that is). The law firm has an affirmative duty to submit all known prior art or they lose their right to represent anyone at the patent office. So the law firm won't take that chance. On receiving lots of prior art the patent examiner will likely decide that there are other patent applications he can work on to make his quota.


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PostPosted: Jan 31, 2014 1:34 pm 
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It is just about impossible to patent or defend a patent in materials. So you can't patent zirconium hydride. But they can patent ways to configure the zirconium hydride into a reactor, ways it can be used, manufactured etc. There are actually companies that have patented all possible ways of synthesizing certain complex materials, even though some aren't realistic at all, just so that the material itself can be defended through the back door.


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PostPosted: Feb 02, 2014 9:24 pm 
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I don't know much about patents, but is there not a duty of disclosure of prior art against your own patent?


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PostPosted: Feb 02, 2014 9:37 pm 
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Yes - but it is limited to what you know about - and the lawyers encourage us not to go looking for prior art.


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