Energy From Thorium Discussion Forum

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PostPosted: Apr 11, 2014 6:50 am 
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Cyril R wrote:
That's for really fast neutrons. Even RMWR has very few 5-10 MeV neutrons and no >10 MeV neutrons.

OK, so how is U232 produced ? .....or are you saying that it isn't ?


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PostPosted: Apr 11, 2014 7:43 am 
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jaro wrote:
Cyril R wrote:
That's for really fast neutrons. Even RMWR has very few 5-10 MeV neutrons and no >10 MeV neutrons.

OK, so how is U232 produced ? .....or are you saying that it isn't ?
from u233 n2n. Thorium needs faster spectrum and even then has pa233 decay to u231 so needs another capture. U233 is a one step reaction with lower threshold


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PostPosted: Apr 11, 2014 8:47 am 
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No wait. Pa231 is long lived. So you need a capture on pa231 in stead. Not likely in a fast reactor. And in a thermal reactor you dont get much th n2n.


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PostPosted: Apr 17, 2014 11:21 am 
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An MSR version of RMWR or water moderated version of waste burner seems to be a good idea.
UCl6 and PuF6 are low boiling and can be extracted from used fuel by chloride/fluoride volatility.
An MSR fuel consisting of tri- or tetravalent salts could be burnt in a water moderated and cooled multi-tube reactor with low moderation and high fissile production. Thorium could be introduced like in the DMSR.


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PostPosted: Aug 30, 2014 2:27 pm 
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Hitachi is continuing with the development of its RMWR/RBWR reactor, which it first started in the late 1990s and has now sought further research support from MIT, University of Michigan and the University of California, according to this WNN article from the 29th of August:

http://world-nuclear-news.org/WR-Hitach ... 08144.html

In many respects, this is a very attractive and interesting development: almost achieving the capabilities of a fast breeder reactor, but using the well-known BWR technology with its "simple" direct cycle.

But does a PWR have specific disadvantages compared to a BWR with regard to reduced moderation ?


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PostPosted: Aug 30, 2014 7:37 pm 
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U-232 is not much of a problem inside a reactor core, a hotbed of radioactivity in any case. If it can be recovered during reprocessing, it can be a fuel for RTG.
The real problems with using thorium in an MSR are:-
1. Keeping it in the liquid fuel.
2. Managing the fissile feed.
The starting fissile feed has to come as Pu from used LWR fuel. UK have a big stock. The US have weapon surplus.
If you cannot get sufficient concentration of thorium in the liquid fuel, put in a part as a metallic solid 3-D arrangement. It will keep getting converted to U-233 and enter liquid phase as uranium salts.


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PostPosted: Aug 31, 2014 3:26 am 
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jagdish wrote:
U-232 is not much of a problem inside a reactor core, a hotbed of radioactivity in any case. If it can be recovered during reprocessing, it can be a fuel for RTG.
The real problems with using thorium in an MSR are:-
1. Keeping it in the liquid fuel.
2. Managing the fissile feed.
The starting fissile feed has to come as Pu from used LWR fuel. UK have a big stock. The US have weapon surplus.
If you cannot get sufficient concentration of thorium in the liquid fuel, put in a part as a metallic solid 3-D arrangement. It will keep getting converted to U-233 and enter liquid phase as uranium salts.


Jagdish, I think you are getting off-topic in this thread, a reduced moderation water reactor is an adapted LWR which uses MOX (U-Pu) fuel, as Hitachi is envisaging, it has little to do with liquid fuel in combination with U-233. In its joint research with MIT, UM and UCB it has been evaluating the safety of such a reactor and is now continuing its research, focusing on further applications of a RMWR/RBWR, according to this recent WNN article.

What I am interested in, is why other reactor (PWR) builders such as Areva, Westinghouse, Mitsubishi, etc. are not choosing the same trajectory as Hitachi with its RMWR. Which begs the question: does the BWR have some inherent advantages over a PWR in this regard ?


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