Energy From Thorium Discussion Forum

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PostPosted: May 26, 2014 1:36 pm 
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djw1 wrote:
Sr-90 is an alpha emitter with a 1.3 ba xs.
Leave it with the TRU.
It wont get in the way.

I don't believe Sr-90 is an alpha emitter. It emits high energy betas. The Soviet Union used it for remote power generation. The general desire was to isolate the Sr-90 to create power sources for various remote applications (like undersea cables, deep in oil wells, space probes, etc.). I don't think it travels with plutonium with any of the proposed processes to separate plutonium from fission products. Instead, it tends to stay with the fission products.
Since the Soviets used it in RPG applications there is a reasonably cost effective method - but it may generate lots of other waste.

If there happens to be a "clean" way to remove the strontium without increasing the waste stream with lots of solvents, AND the public really values prompt fission product permanent disposal THEN it may make sense to remove both the cesium and strontium (and the TRUs). At this point the remainder generates very little heat after 10 years or so and can be vitrified and buried.

Note that there are lots of IF's in the above. For me personally, I'd rather just be patient, it isn't much stuff and we can reasonably store it in a form that is passively cooled. After 5 years cooling decay heat for a reactor that has been running infinitely is 4e-4 * power level. Translating this to the US we use around 500GW, so if you used nuclear power for all US electricity for hundreds of years the total heat from all the waste (after 5 years onsite storage to cool sufficiently to make transport reasonable) would be around 200MW. This would be quite reasonable to passively cool.


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PostPosted: May 27, 2014 12:10 am 
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Most strontium salts including the acetate and chloride are soluble and can be leached from the used fuel during the reprocessing. It could be separated by fractional crystallization or precipitating it as fluoride.
Uranium can be separated as volatile UCl6 or leached as uranyl salts.
Transuranics including the Pu can be separated as in IFR processing.
Use Sr as decay fuel in RTG and uranium and TRU as fission fuel in reactors. Other fission products can be buried if not required.
This makes for a lot of 'cooking'.


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PostPosted: Jun 11, 2014 5:34 am 
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Lars wrote:
KitemanSA wrote:
Several thoughts on this.
The TRUs can be used as a starter charge for a Liquid Fluoride Thorium Reactor and by using the U as a diluent to achieve sustainment level rather than breeder level, you create what I like to call the 2.2+ fluid LFTR.

Once you are at the state with processing the unspent fuel for LFTRs, the FPs can also be segregated. At that point it seems wise to extract any FPs that are economical to do so, Cs and Sr seem a good starting point. Cs for gamma irradiation of stuff (food, etc.) and Sr for RTGs or SRMs.


For thermal LFTRs U-238 is a loss. It is a necessary evil for denaturing but we build up excess U238 over time so we add as little of it as necessary. Thermal LFTRs will never consume the LWR spent fuel uranium.
The idea is to add just enough of it to keep an otherwise pure Th/U233 cycle at sustainment vice breeding. Given the 60+ year life span of a LFTR it seems likely that most if not all of the unused U from SNF could be consumed along with the Pu used as the starter charge. I am not looking to run the LFTR on SNF, just burn up one batch of SNF per LFTR started with it.

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Last edited by KitemanSA on Jul 28, 2014 7:52 am, edited 1 time in total.

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PostPosted: Jun 11, 2014 9:28 am 
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KitemanSA wrote:
Lars wrote:
KitemanSA wrote:
Several thoughts on this.
The TRUs can be used as a starter charge for a Liquid Fluoride Thorium Reactor and by using the U as a diluent to achieve sustainment level rather than breeder level, you create what I like to call the 2.2+ fluid LFTR.

Once you are at the state with processing the unspent fuel for LFTRs, the FPs can also be segregated. At that point it seems wise to extract any FPs that are economical to do so, Cs and Sr seem a good starting point. Cs for gamma irradiation of stuff (food, etc.) and Sr for RTGs or SRMs.


For thermal LFTRs U-238 is a loss. It is a necessary evil for denaturing but we build up excess U238 over time so we add as little of it as necessary. Thermal LFTRs will never consume the LWR spent fuel uranium.
The idea is to add just enough of it to keep an otherwise pure Th/U233 cycle at sustainment vice breeding. Given the 60+ year life span of a LFTR it seems likely that most if not all of the unused U for SBF could be consumed along with the Pu used as the starter charge. I am not looking to run the LFTR on SNF, just burn up one batch of SNF per LFTR started with it.

We must remember that thorium is a downstream technology from uranium. It requires fissile feed from enriched uranium or fission products of a reactor.
You could start with fast, used fuel uranium burning MSR. You could gradually add thorium as a spice which produces superior fissile U-233.
There is an IFR concept involving fast reactors and reprocessing.
Fast MSR would be a better alternative to solid fuel fast reactor. There would also be synergy in pyro-processing.


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PostPosted: Jun 11, 2014 10:18 am 
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jagdish wrote:
KitemanSA wrote:
The idea is to add just enough of it to keep an otherwise pure Th/U233 cycle at sustainment vice breeding. Given the 60+ year life span of a LFTR it seems likely that most if not all of the unused U for SBF could be consumed along with the Pu used as the starter charge. I am not looking to run the LFTR on SNF, just burn up one batch of SNF per LFTR started with it.
We must remember that thorium is a downstream technology from uranium. It requires fissile feed from enriched uranium or fission products of a reactor.
If you go back you will find that I propose to use Pu from SNF as a starter charge for a LFTR and then use just enough U from that batch of SNF to maintain sustainment mode. Over the life of that LFTR, it should burn thru just about all of the rest of that batch of SNF. In that way, LWRs become a sort of "mother reactor" for a whole fleet of LFTRs.

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PostPosted: Jun 11, 2014 10:24 pm 
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KitemanSA wrote:
Lars wrote:

For thermal LFTRs U-238 is a loss. It is a necessary evil for denaturing but we build up excess U238 over time so we add as little of it as necessary. Thermal LFTRs will never consume the LWR spent fuel uranium.
The idea is to add just enough of it to keep an otherwise pure Th/U233 cycle at sustainment vice breeding. Given the 60+ year life span of a LFTR it seems likely that most if not all of the unused U for SBF could be consumed along with the Pu used as the starter charge. I am not looking to run the LFTR on SNF, just burn up one batch of SNF per LFTR started with it.

A 1GWe power plant will consume 1 tonne of fertile or fissile per year. So IF you had a 1GWe machine that could burn SNF it would take 20-25 years to burn off one year of the 1GWe LWR SNF. If you have a thermal LFTR with breeding and want to use your extra neutrons to burn off U238 you would burn this much more slowly. How slow? Well a good thermal breeder might achieve 6% breeding - meaning it has around 6% surplus neutrons. You would need something like an extra 0.25 neutrons per fission if you have U238 in the thermal machine so you might burn off 250kg/GWe-yr of U238. So you will need 80 to 100 years of a good thermal breeder to burn off one years worth of LWR SNF. If you goal is to burn off LWR SNF you need to go with a fast breeder. (Not a goal I share though).


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PostPosted: Jun 12, 2014 3:50 am 
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Eating of fuel rods reminds of other equivalents relating to food.
Uranium is a fruit which can be consumed comparatively raw with suitable moderators (spices) in some type of rectors. Thorium needs enrichment with additional fissile. Enrichment has been deliberately used in this manner.
Fissile is equivalent to gastric juices. You have to add some to thorium. Uranium can use its own or concentrated (enriched).
Enrichment or reprocessing are equivalent to cooking. Big bosses try to control it.
Reprocessing or 'cooking' is an ignored essential for developing nuclear power We are close to exhausting the ready to eat, low hanging fruit. Let the world reprocess the used fuel and use the recovered fissile economically with thorium or in fast reactors or both.
MSR's are better than solid fuel in either case.


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PostPosted: Jul 28, 2014 7:56 am 
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Lars wrote:
KitemanSA wrote:
The idea is to add just enough of it to keep an otherwise pure Th/U233 cycle at sustainment vice breeding. Given the 60+ year life span of a LFTR it seems likely that most if not all of the unused U for SBF could be consumed along with the Pu used as the starter charge. I am not looking to run the LFTR on SNF, just burn up one batch of SNF per LFTR started with it.

A 1GWe power plant will consume 1 tonne of fertile or fissile per year. So IF you had a 1GWe machine that could burn SNF it would take 20-25 years to burn off one year of the 1GWe LWR SNF. If you have a thermal LFTR with breeding and want to use your extra neutrons to burn off U238 you would burn this much more slowly. How slow? Well a good thermal breeder might achieve 6% breeding - meaning it has around 6% surplus neutrons. You would need something like an extra 0.25 neutrons per fission if you have U238 in the thermal machine so you might burn off 250kg/GWe-yr of U238. So you will need 80 to 100 years of a good thermal breeder to burn off one years worth of LWR SNF. If you goal is to burn off LWR SNF you need to go with a fast breeder. (Not a goal I share though).
80-100 years? I think you may be off a bit, but 80-100 years seems ok to me.

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PostPosted: Jul 29, 2014 4:41 am 
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LWR as mother machines have laid enough eggs in form of used fuel. If used in breeder reactors, it could see the mankind through a century or more as fuel.
The need now is to hatch these eggs by reprocessing and good breeder reactors, solid or liquid fueled. Thorium could be introduced as the source of superior fissile U-233. Metal fueled fast reactors being used/developed in Russia, India and China are no better than old reliables, slightly bugged by sodium fires.
Any ideas on a better version of Indian three-stage program based on used LWR fuel? MSR is a good hint.


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