Traveling-Wave Reactor - we need them badly

[Dr.LAL]

Traveling-Wave Reactor - we need them badly !

What is the fuel = Pu-239.
Energy equivalent of 1 pound of the above = 2,000,000 lbs of coal
Waste=comparatively miniscule
Currently we have 104 nuclear reactors in operation in the US, which generate about 20% of our electricity.
Waste discharged per year = 2000tonnes.
95% of this is U-238 can be used for this one !
Radioactivity is the same as existing ones so nothing new.
Shielding = almost the same as other RA plants
Security – spent fuel is difficult to re-process so not many takers !
TWRs win !

Dr.LAL
DALLAS

PS - what is TWR ? read on Wikipedia (http://en.wikipedia.org/wiki/Traveling_wave_reactor)

 

[QuantumPion]

I'm curious about the neutronics properties of the TWR. I'm tempted to try to make a model of one in Keno some time :)

 

[Astronuc]

Fast spectrum. One will need to use transport theory.

I imagine MNCP and ORIGEN2 are being used.

See this thread.
https://www.physicsforums.com/showthread.php?t=382272

Re: "Traveling-Wave Reactor - we need them badly !" Not so fast. They need to do a working demo. It will certainly generate waste. There are numerous technical issues that need to be resolved, e.g., fuel swelling (and how that affects vessel integrity), and migration of fission products. It will produce unused Pu and transuranics.

The spent core will have to be disposed of in much the same manner as spent fuel will be. It's complicated because it's one large mass. It may not be economical if the lifetime is too short - because once the reactor shutsdown, the plant if offline and there would be significant stranded assets - unless the spent core is removed to a nearby storage area.

 

[kundalini]

I wonder what is the cladding material selected for this concept. Also, what type of nuclear poison is used?

 

[kundalini]

I suppose if the Traveling Reactor can run for ~60 years without refueling, the clad metal should also last for the same number of years! Hence, the effect of radiation on clad metal properties must be tested. There will be radiation-induced creep, swelling, phase instabilities, radiation hardening and embrittlement, etc. How about fuel-cladding chemical interaction?

Any nuclear gurus out there care to comment!

 

[Astronuc]

I suppose if the Traveling Reactor can run for ~60 years without refueling, the clad metal should also last for the same number of years! Hence, the effect of radiation on clad metal properties must be tested. There will be radiation-induced creep, swelling, phase instabilities, radiation hardening and embrittlement, etc. How about fuel-cladding chemical interaction?

Yes - the materials have to be tested. Bur first the operating environment has to be determined and characterized.

As far as I know, the design has been reconfigured from the original design. I think a video of the original concept showed a nice symmetic wave. However, I'm quite sure they only modeled the nuclear physics or transport equation and transmutation, but they did not include atomic migration and fission product development, and the thermo-mechanical aspect of the reactor.

I would like to see the multiphysics simulation of the original design taking into account the swelling of the fuel matrix - one atoms fissions into two atoms, which occupy twice the space. If one fission 20% of the original atoms (about 20% FIMA or ~ 200 GWd/MTU), what swelling will one obtain?

I'd like to see similar results for the revised configuration, and the heat removal scheme, which will also give an idea of the operating temperature. I've heard the new design looks more like a conventional fast reactor.

I see heat transport from the interior, as well as reactivity control, being a challenge, at least on the originally reported configuration.

Without knowing more specifics, my guess for a structural material would be a high temperature superalloy, or possibly a ferritic or martensitic-ferritic steel.

 

[Astronuc]

FYI - http://bnrc.berkeley.edu/documents/forum-2010/Presentations-SS/Greenspan_TWR.pdf

It's looking a lot more like a conventional fast reactor.

Apparently they finally hired some folks with sense.

 

[mheslep]

It will produce unused Pu and transuranics.

Yes, but much less than traditional U235 reactors if it works at all.

The spent core will have to be disposed of in much the same manner as spent fuel will be.

Does it require the same disposal? Certainly the TWR's will have a similar set of highly radioactive, but short lived, fission products that require control, but there should be relatively little Pu or U left in the mix posing a proliferation problem, unlike PWR spent fuel going into a fuel recycling program.

It's complicated because it's one large mass. It may not be economical if the lifetime is too short - because once the reactor shutsdown, the plant if offline and there would be significant stranded assets - unless the spent core is removed to a nearby storage area.

The idea is that because of the high burnup localized to the wave in the reactor, the reactor can be made small (5-8M high) and loaded with a lifetime of fuel, a lifetime being 40-70 years. Because the reactor is small, it is proposed that it be buried during operation, perhaps with a gas turbine and balance of plant above ground. With only short lived fission products left at end of life, why not just leave it there? The concern about fuel swelling seems to indeed be a difficult problem, but that is a binary issue: either it is solvable or not. If it is not, then the wave concept, whatever its other theoretical benefits, is not feasible. it it is then all the above appears to follow.

 

[Astronuc]

Update: http://bnrc.berkeley.edu/documents/...S-Session-II/Kevan_Weaver_TerraPower_Pres.pdf

On page 4
Physics
• Modified version of MCNPX-CINDER90
• REBUS

Thermal hydraulics and safety
• Superenergy
• SASSYS

Fuel performance modeling
• FEAST

On page 7
2-D and 3-D models show ≥ 30% (peak) burnup,
and ≥ 500 dpa required to sustain a “wave” in uranium
• Requires metal fuel to sustain “wave”
• Higher heavy metal density
• Harder neutron spectrum

On page 15
TP-1
• Power = 1200 MWth, 500 MWe
• Operating temperature = 360°C / 510°C
• Core ΔP = 1 MPa
• Fuel = U-Zr alloy, sodium bond, HT-9 clad

I'd recommend ditch the Na bond and coextruding the clad with the fuel. There is the issue of f.p. migration to the cladding and cladding embrittlement.

Major Challenges (page 19)
Fuels and materials
• Burnup and fluence are beyond current data base (and fuel swelling)
Licensing
• Atypical design, with burnup and fluence beyond current database.

30% ~ 300 GWd/tHM as compared to rod average burnups ~ 50-70 GWd/tU (peak local ~ 82 in limited commercial fuel) for conventional LWR fuel. FFTF had some high burnup experiments with exposures around 20% (~200 GWd/tHM)

 

[QuantumPion]

Nice, I wonder if they will get anywhere with this. I bet utilities would love the idea of a 1200 MWe plant with no refueling!

 

[mheslep]

• Power = 1200 MWth, 500 MWe

41% efficient? Can anyone report the best done so far with a PWR?

 

[Astronuc]

41% efficient? Can anyone report the best done so far with a PWR?

As far as I know, the best PWR was about 37% efficient. I believe it was one of the pre-Konvoi units in Germany, after they replaced the LP turbines and possibly the HP turbines with advanced designs that produced an extra 150 MWe without increasing thermal power.

The most efficient BWRs are probably about 34-35% efficient. However, I can't recall if that is gross or net.

 

[QuantumPion]

As far as I know, the best PWR was about 37% efficient. I believe it was one of the pre-Konvoi units in Germany, after they replaced the LP turbines and possibly the HP turbines with advanced designs that produced an extra 150 MWe without increasing thermal power.

The most efficient BWRs are probably about 34-35% efficient. However, I can't recall if that is gross or net.

The new Gen3+ reactors, such as the Mitsubishi US-APWR are supposed to be 42% efficient due to improved turbine/generator design.

However, I think you were confusing two different numbers. In the PDF, there was a 500MWe test design and a 1200MWe commercial design. It was not one plant with 1200MWth/500MWe.

 

[Astronuc]

The new Gen3+ reactors, such as the Mitsubishi US-APWR are supposed to be 42% efficient due to improved turbine/generator design.

However, I think you were confusing two different numbers. In the PDF, there was a 500MWe test design and a 1200MWe commercial design. It was not one plant with 1200MWth/500MWe.

Page 15 of the pdf does report 1200 MWth for the TP-1. There is also a 1150 MWe plant (see page 10), the TPRP.

 

[mheslep]

The presentation does not specifically address fission products. My understanding is that expansion and poisoning from fission products is one the more difficult challenges in attempting a decades long fuel cycle (60 years here). Has TerraPower et al ignored the issue in the brief, or is it implied somewhere that I missed?

 

[QuantumPion]

The presentation does not specifically address fission products. My understanding is that expansion and poisoning from fission products is one the more difficult challenges in attempting a decades long fuel cycle (60 years here). Has TerraPower et al ignored the issue in the brief, or is it implied somewhere that I missed?

They used MCNPX-CINDER90 which is a monte carlo + depletion code so I assume they did model fission products.

 

[mheslep]

Yes, I assume in the model that they assumed some fission product removal rate over the claimed 60 year cycle. Has to, no? Ok, what's the removal mechanism? Then there's expansion to deal with in a solid core, if not from fission products then from radiation induced swelling. Page 20 acknowledges swelling. Ok, and?

Edit: page 21 has one bullet: "fission product transport and source term". Fairly thin.

 

[QuantumPion]

Yes, I assume in the model that they assumed some fission product removal rate over the claimed 60 year cycle. Has to, no? Ok, what's the removal mechanism? Then there's expansion do deal with in a solid core, if not from fission products then from radiation induced swelling. Page 20 acknowledges swelling. Ok, and?

Edit: page 21 has one bullet: "fission product transport and source term". Fairly thin.

Yeah I'm guessing that document is merely talking points and that the actual details were given in a presentation.