Energy From Thorium Discussion Forum

I think CReff is supposed to, in that case, be a measure of how much of the input material can be burned away.
If I feed the reactor 20% LEU for example, if I burn up all the fuel then that means my CReff is 1 even if my actual CR is less than that.

There is a new paper, a technical memorandum done with ORNL thru the GAIN program, called "Two-Dimensional Neutronic and Fuel Cycle Analysis of the Transatomic Power Molten Salt Reactor" - story and link to the paper at: http://www.prweb.com/releases/2017/01/prweb13979699.htm

I may have missed it, but I do not see in the paper what cladding is proposed for their zirconium hydride rods. Seems to me that they are betting the farm on this cladding working, and also getting regulatory approval.

Jim L.

The key differences between TAP's current claims and what we've seen before are as follows:

"Specifically, we have realized that our initial analyses of spent nuclear fuel (SNF) core loadings were centered around inaccurate assumptions about reactor behavior that, upon detailed review, had to be corrected. This led to the conclusion that while the reactor can achieve criticality on an SNF fuel load and an SNF fuel feed, it cannot maintain criticality for sufficient lengths of time to produce a sustainable net-negative waste profile.
The results have prompted a shift in focus to reducing the rate at which waste is produced while simultaneously utilizing the current commercial 5% LEU supply chain."

This means that it's just another burner-type reactor & therefore incapable of replacing fossil fuels as humanity's primary energy source. The same conclusion applies to most of the other MSR concepts currently being considered.

While none of TAP's white papers gives a detailed description of their current system, it's possible to piece together its key characteristics from what they have revealed. Here's what I come up with

thermal/electric power: 1.25th/0.52 GWe
burnup 90 GWt/tonne
approximate total salt volume: 22 m3 (assuming 4 m3 out of tank volume)
initial salt composition: 27 mole% 5% enriched UF4/73 mole% LiF (100% Li7)
initial total uranium in fuel salt: 63 tonnes
mass "pure" lithium 7: 5.6 tonnes
initial 235U in fuel salt: 3.1 tonnes (or 6 tonne 235U/GWe - about the same as a LWR)
mass of ZrH1.6 in its moderator rods: 31 tonnes
number of moderator rods: 4318
fraction 235U fissions over 90 GWd/t lifetime: 40.6%
mass "New Uranium" (NU) required per GWe-year 81 tonnes (state of the art LWRs require about 160 tonnes)
approximate salt lifetime @0.52 GWe 12 years

In my opinion, TAP's leadership should be emphasizing more efficient (less NU/GW) systems. It's perfectly OK to assume a 20% initial enrichment which change would make it look considerably better.

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Darryl Siemer

Do you (anyone?) know how much fuel salt both ORNL's & TAP's own analyses are assuming? I can't figure out how they can get a lifetime of 28 years with the amount/volume of salt that I arrived at (about 22m3) based upon the component sizes indicated in the figures.

There's another issue that confuses me. As the initial fissile load burns off, more moderator rods are inserted which will eventually displace about 4 cubic meters of the fuel salt - where does it go?

The latest (your link's) analysis also indicates that cesium/rubidium/barium/calcium is "discarded" on a 3455 day (9.4 year) cycle - does that mean that the lithium 7 has to be replaced that often too? If so, the total amount of "high level" radwaste generated/GWe is going to be much greater than that generated by today's once-through LWRs.

In my opinion, what we're learning here (again) is that U/Pu based breeder reactors should not be moderated at all.

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Darryl Siemer

The assumption is that as fuel is fissioned and fission products are removed (off gas systems/scrubbers) more fuel is added to top off fissile/fertile loads.
MSRs can be refuelled online.
I haven't read the paper, this applies to all MSRs (in theory).
MSRs should also be designed with a little overflow room so the core and primary piping is always filled with salt, and some region on top of the reactor takes the overflow if needed, for instance at startup/right after adding more fuel.

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Looking for companies working to change the world.

http://www.nextbigfuture.com/2017/02/oa ... .html#more
Once Transatomic or Terrestrial get an MSR running, the material problems of the MSR will be solved and it should be possible to shift to a Th-U233 cycle and breeders.

Neither of those companies is moving technology in the direction it needs to go for a true thorium MSR. Only Flibe Energy is doing that.

Take a standard 2 Fluid LFTR and add just enough SNF actinides to keep it at sustainment level. This will allow you to burn the TRUs in a thermal spectrum reactor.

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DRJ : Engineer - NAVSEA : (Retired)

Kiteman,
An intriguing claim, worthy of it's own thread, IMHO.

I will comment quickly on two points though. First is that from what I understand on MSR design a LFTR-like MSR will not have many neutrons to spare to burn TRUs. This is essentially what TAP has discovered and they must now walk back some of their claims on what WAMSR can do. My "back of the envelope" calculations show that U-238 is effectively a neutron poison in the thermal spectrum, it's best to leave that out of a LFTR-like reactor if at all possible. Using LUFF (lightly used fission fuel, an acronym I first saw you use and one I find both amusing and appropriate) means introducing U-238. This gets beyond my understanding of nuclear physics very quickly, as well as the time I'm willing to spare to investigate it, very quickly.

My second point is that as I recall your "2.2+ fluid LFTR" design involves a neptunium extraction step. My back of the envelope calculations show that this creates a proliferation concern. Combining U-238 bombardment with continuous extraction of Np means that the Np from this extraction will have a very high concentration of Np-239. This Np-239 will decay in a short time to Pu-239. Flibe Energy avoids this with their Np extraction by not introducing U-238 to the fuel, what comes out is the highly valuable Np-237 used to produce RTG fuel.

I saw no mention in anything from TAP that they'd do an Np extraction into a decay tank to save on neutrons. I'd think this would be a very good idea except for the weapon proliferation concern which would make such a reactor design very undesirable when it comes to getting a license for a civilian power reactor. I'd expect this might be desirable for a military reactor, that could be used to produce "supergrade" plutonium.

This is an intriguing idea, which is also worthy of its own thread, IMHO.

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

Please stay on topic rather than attempting to redesign Transatomic's reactor. I'm sure you can start another thread for that. But no one from Transatomic reads this forum, so your time is wasted in such an effort.

Yes, of course, that is why I started and ended my last post with the comment that such topics are worthy of their own thread. If someone starts such a thread then I'll certainly read it and contribute what I can.


I'm not trying to redesign TAP reactors, or solicit a response from them. What I am soliciting is an insight from the members of this forum on aspects of TAP reactor design that I may have missed. I do not recall reading anything from TAP that would indicate that they propose doing any actinide extraction from the fuel for the purposes of neutron savings and/or milking off valuable isotopes. If someone has seen that proposed in any of the papers from TAP then I'd appreciate someone highlighting that for me.

If someone would like to discuss the why and how of actinide extraction in a WAMSR or WAMSR-like reactor then that is absolutely something for another thread, and something I'd like to discuss sometime on this forum. I have my own theories why TAP does not have actinide extraction, which I'd like to discuss further in another thread at some point.

Kiteman,
You've brought up your LFTR derived reactor proposal several times now in different threads, if you really want to have it discussed and critiqued by the members of this forum then please create a thread for it under the appropriate heading. It is helpful to compare and contrast different reactor designs such as those from yourself and TAP but this can get off topic quickly as Mr. Sorensen has reminded us.

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

It appears that staid old breeders are the only way known yet to burn used fuel stocks.
Russia seem to be soldiering on but UK,France and Japan seem to have joined the US to wayside.

http://www.nextbigfuture.com/2017/02/tr ... laims.html
My optimism about MSR continues to get punctured.
Irrespective of solid or liquid fuels(MSR), it will take reprocessing and fast reactors to burn as fuel thorium or even U238 available in DU or used nuclear fuel.
Fractional distillation or crystallisation of chloride/fluoride salts could be the new way of processing with molten salts.