Open issue for LFTR

Threads relating to the design of liquid-fluoride reactors.
edpell
Posts: 98
Joined: Apr 03, 2011 7:50 pm
Location: Rhinebeck, NY

Open issue for LFTR

Post by edpell » Aug 27, 2011 4:02 pm

What are the open issues standing in the way of designing a LFTR? The ones I can think of are

1) Hastelloy interaction with clean slat, with salt+fuel, with blanket salt
2) pump design for clean salt (or maybe salt+fuel) heat extraction loop
3) chemistry to extract elements (how many?) from
a) clean core salt
b) core salt+fuel
c) blanket

Are there others? What fraction of the chemistry was done already by ORNL? How long will this development program take regardless of who or where?

Lars
Posts: 3060
Joined: Jul 28, 2008 10:44 pm

Re: Open issue for LFTR

Post by Lars » Aug 27, 2011 4:52 pm

I think the biggest issue is going to be regulator with a fluid fuel.

But if your question is about science and engineering it depends very much on the LFTR you are talking about. The most simple version would be pretty much like MSRE only with thorium put into the fuel salt and more fissile added to match. You could build it as a high converter. That would mean you have to add fissile (20% LEU) periodically but that you get to skip the hard chemistry. The main issue that comes to mind is how to collect the noble metals - these changed behavior considerably during the MSRE and were not well understood. They want to plate out somewhere and if no other arrangements are made then they will likely plate out on the interior of the heat exchanger. (They prefer to plate out on metals and likely in the colder spots in the loop). If they plate out on the HX then that likely creates a safety issue should you lose both the coolant and drain the fuel salt. Since they want to come out of the salt it seems reasonable to anticipate that we can arrange a favorable place for this to happen and get them to plate out someplace of our choosing. Besides this there are lots of engineering type issues that ORNL showed basic proof of concept but need to be scaled up considerably (pumps, etc.). I believe the HastalloyN is qualified for the temperature but I don't think it has been nuclear qualified (and I have no idea how painful this might be).

At the other end of the scale you have a full chemical processing plant with fluorination to remove uranium (w/o any possibility of creating a critical mass), distillation to recover 7Li, and some variant of liquid metal exchange (this needs the most work) to recycle the TRUs.

cloa513
Posts: 78
Joined: Jun 30, 2011 7:10 pm

Re: Open issue for LFTR

Post by cloa513 » Sep 07, 2011 7:39 pm

Lars wrote:I think the biggest issue is going to be regulator with a fluid fuel.

But if your question is about science and engineering it depends very much on the LFTR you are talking about. The most simple version would be pretty much like MSRE only with thorium put into the fuel salt and more fissile added to match. You could build it as a high converter. That would mean you have to add fissile (20% LEU) periodically but that you get to skip the hard chemistry. The main issue that comes to mind is how to collect the noble metals - these changed behavior considerably during the MSRE and were not well understood. They want to plate out somewhere and if no other arrangements are made then they will likely plate out on the interior of the heat exchanger. (They prefer to plate out on metals and likely in the colder spots in the loop). If they plate out on the HX then that likely creates a safety issue should you lose both the coolant and drain the fuel salt. Since they want to come out of the salt it seems reasonable to anticipate that we can arrange a favorable place for this to happen and get them to plate out someplace of our choosing. Besides this there are lots of engineering type issues that ORNL showed basic proof of concept but need to be scaled up considerably (pumps, etc.). I believe the HastalloyN is qualified for the temperature but I don't think it has been nuclear qualified (and I have no idea how painful this might be).

At the other end of the scale you have a full chemical processing plant with fluorination to remove uranium (w/o any possibility of creating a critical mass), distillation to recover 7Li, and some variant of liquid metal exchange (this needs the most work) to recycle the TRUs.

Apparently Hastelloy N is ASME qualified for nuclear work though haven't found a specific reference point for that. Google's blurb for this link says so.





http://www.nuc.berkeley.edu/pb-ahtr/pap ... onse_C.pdf

Jess Gehin
Posts: 137
Joined: Dec 03, 2008 5:23 pm
Location: Oak Ridge, TN

Re: Open issue for LFTR

Post by Jess Gehin » Sep 07, 2011 10:14 pm

Hasteloy-N is not fully ASME code-qualified. It is qualified under section VIII to 704 C, but not under Section III, which is required for nuclear components. Some information can be found in this presentation:

https://www.ornl.gov/fhr/presentations/White.pdf

There may be other testing requirements as well including long-term chemical compatibility with fuel salt containing fission products.

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