What's at the forefront of reactor research? A must-read digest/discussion.

[wtmusic]

An exchange of emails between three highly-respected nuclear engineers, augmented by 133 (largely informed) comments at BraveNewClimate.org has become a terrific one-stop resource.

Per Peterson, Ph.D.
Professor and Chair, Department of Nuclear Engineering, UC Berkeley
http://www.nuc.berkeley.edu/People/Per_Peterson

George Stanford, Ph.D.
Nuclear reactor physicist, Argonne National Laboratory (retired)
Part of the team that developed the Integral Fast Reactor.
http://www.thesciencecouncil.com/george-stanford.html

Dan Meneley, Ph.D.
Adjunct Professor, University of Ontario Institute of Technology
Acting Dean, Faculty of Energy Systems & Nuclear Science
http://www.thesciencecouncil.com/dan-meneley.html

"We’ll see what others on this list have to say, but in my opinion, Carlsen’s enthusiasm for thorium is premature, to say the least. The ONLY significant advantage a thorium cycle would have over fast reactors with metallic fuel (IFR/PRISM) is its lower requirement for start up fissile. That advantage is offset by the fact that the thorium reactor is at a stage of development roughly equivalent to where the IFR was in 1975 — a promising idea with a lot of R&D needed to before it’s ready for a commercial demonstration — which puts its deployment about 20 years behind what could be the IFR’s schedule. The thorium community has not yet even agreed on what will be the optimum thorium technology to pursue..."

"If you’ve tried to do control, fuel cycle, and safety system design on a thorium reactor you’ll not be so enthusiastic. The flux shape is a strong function of the past flux shape — because of the protactinium. After you shut the thing down you must account for the later reactivity increase. And then there’s the detail of not having any fissile isotope to start up in the first place..."

"Thorium reactors operate in with a thermal spectrum, which allows them to use graphite as the primary structural material in the reactor core. Graphite can be heated to very high temperatures without losing structural integrity. Combined with the very high boiling temperature of the fluoride-salt coolant (> 1400°C), thorium reactors can deliver heat at substantially higher temperature (between 600 and 700°C with current primary pressure boundary structural materials) than IFR (between 370 and 510°C with current fuel cladding materials). This is a sufficiently higher temperature that several options exist for gas-Brayton power conversion, while at the IFR temperatures steam Rankine is likely to remain the most practical option..."

http://bravenewclimate.com/2011/11/17/ifr-lftr-exchange/

[txlibdem]

1. I'm all linked out for today... can you summarize: do the 3 agree with the listed text?

PS, as seen in the below graph, process heat at 600 degrees C would enable all but 2 of our vital industries to get off of fossil fuels. Concentrating solar energy would provide for the high temperatures of those 2 industries. Therefore, LFTR research should be funded and ardently pursued in addition to SMR research.

[wtmusic]

2. It's a link that doesn't summarize easily

and for that reason, it's worth setting 30 minutes aside and digesting thoroughly along with the comments. Rolled-up shirtsleeve, practical experience with guys who have spent years sitting next to reactors going critical. The comment about the flux shape on LFTRs is typical - what do you do with a tons of hot Pa233 decaying over 27 days until it turns into useable U233? Moderated, your reactor suddenly becomes a bull in a china shop. You can pull it out of the salt, but some of it turns into U232 and starts kicking out gamma rays hot enough to burn hairs off your chest. Is a Brayton cycle turbine going to work in a closed loop?

A measly $billion or four would answer those questions.

[txlibdem]

3. Since Fossil Fuels currently receive $400B in subsidies worldwide that seems like a paltry sum

So, darn right, let's put that money into researching zero carbon energy sources rather than subsidizing the most polluting and most profitable companies in the world.

[PamW]

4. Thank You

Thank You for your link to this discussion.

It's good to see a good technical discussion between REAL SCIENTISTS, and not the ideologues that pass themselves off as scientists in order to gain credibility.

Contrary to one DU forum member's contention that everything possible in the field of nuclear energy has already been explored and none of it works; one sees here real scientists discussing real promises for future research.

PamW

[wtmusic]

5. You're welcome.

There are some incredibly exciting technologies on the horizon. Brayton-cycle generator tech is almost more important than the reactors themselves...while following up on this post, I came across this one

http://inhabitat.com/gas-powered-brayton-cycle-turbine-to-increase-efficiency-by-50/

which could also mean an immediate 25% increase in power for new or retrofitted natural gas plants.

[PamW]

7. Brayton Cycle..

Brayton-cycle generator tech is almost more important than the reactors themselves..
===========================

Yes - I remember working out a problem as a doctoral student at MIT in which there was a gaseous fuel reactor with the gaseous fuel also serving as the working fluid of a Brayton cycle. One had to determine the dynamics of such a system. Hint: as power increases, so does the speed of the Brayton cycle compressor, so the pressure goes up in the gaseous fuel, hence the density goes up in the gaseous fuel, and that does what to the reactivity?.....

PamW

[kristopher]

6. You do realize that link disproves most of your hype...

You do realize that link disproves most of your hype about thorium, don't you?

It shows that the list of benefits you tout are a compilation of several different reactors and cannot be attributed to a single design as the LFTR hypesters are doing.

It also confirms the fact that thorium is *not* superior overall to the once through uranium fuel cycle and is therefore NOT the silver bullet technology your crew is trying to make it out to be. You realize that, right?

[Maslo55]

8. ...

quote exactly where does it say such things. I dont see it there.

[PamW]

11. Lack of understanding begets poor interpretation.

quote exactly where does it say such things. I dont see it there.
=======================================

We see again how those that lack training / knowledge in the sciences can't interpret what real scientists say.

It matters not whether said real scientists are those being quoted in the media, or real scientists who are members of the DU forum.

PamW

[Maslo55]

9. IFR

is another great and proven reactor design, which was killed by shortsighted politicians. If the IFR (EBR-II) project was not cancelled in 1994 by Clinton administration after successfully running for almost 30 years, we could have already closed the fuel cycle, and burning nuclear "waste" for power.

In fact, with uranium breeders we can supply our energy needs for longer than the sun will exist, making them in principle even more sustainable than renewables:
http://www.sustainablenuclear.org/PADs/pad11983cohen.pdf

[PamW]

10. IFR cont'd

IFR is another great and proven reactor design,
-------------------------------------------------------

For more information, check out the following interview by Pulitzer Prizer winner Richard Rhodes for PBS's Frontline with a real scientist, nuclear physicist Dr. Charles Till, who was then Associate Director of Argonne National Laboratory:

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/till.html

[wtmusic]

12. In fairness to Clinton

1994 was 8 years post-Chernobyl, he was seeking re-election. Global warming was about as well understood as IFR's proliferation possibilities, which at the time was not very well.

A lot of debate about the relative merits of IFR/MSR at the link above. IMO a well-tested IFR design would be a significant improvement over what we have, but you still have flammable liquid sodium, solid fuel pellets, and you're relying on convection to provide passive cooling. A meltdown is still very possible, and in an MSR it really isn't.

[PamW]

13. Actually...

A lot of debate about the relative merits of IFR/MSR at the link above. IMO a well-tested IFR design would be a significant improvement over what we have, but you still have flammable liquid sodium, solid fuel pellets, and you're relying on convection to provide passive cooling. A meltdown is still very possible, and in an MSR it really isn't.
===========================

Actually NO - a meltdown in the Integral Fast Reactor is NOT POSSIBLE, every bit as much as it is impossible in an MSR.

First, the liquid sodium is held in a container such that oxygen can't get to it. Without oxygen, the liquid sodium can't catch fire.
EBR-II operated for over 4 decades without any type of mishap owing to the liquid sodium.

Yes - you rely on convection - and that's GOOD!!!. If you have a high heat capacity coolant like sodium, then natural convection can provide all the necessary cooling. Natural convection is as reliable as gravity because that is what drives it. As long as there is a heat source that needs to be cooled, and you have gravity; then you will have natural convection. EXTREMELY RELIABLE

As far as why Clinton cancelled the IFR, it was one of his campaign promises in 1992. In fact, he mentioned the cancellation in his very first State of the Union address. He attempted to cancel it in his first budget, but Congress didn't go along. However, it was cancelled in his second budget.

http://www.sustainablenuclear.org/PADs/pad0509till.html

http://seekerblog.com/2009/11/26/plentiful-energy-and-the-ifr-story-how-the-ifr-was-killed-part-2/

Before some says, "Oh that's published in a pro-nuke website..." The pro-nuke website just published it. The words were written by Dr. Charles Till, who is a scientist, not a lobbyist.

PamW

[wtmusic]

14. A sodium fire closed a Japanese plant (Monju) for fifteen years

"On December 8, 1995, the reactor suffered a serious accident. Intense vibration caused a thermowell inside a pipe carrying sodium coolant to break, possibly at a defective weld point, allowing several hundred kilograms of sodium to leak out onto the floor below the pipe. Upon coming into contact with the air, the liquid sodium reacted with oxygen and moisture in the air, filling the room with caustic fumes and producing temperatures of several hundred degrees Celsius. The heat was so intense that it warped several steel structures in the room.[3] An alarm sounded around 7:30 p.m., switching the system over to manual operations, but a full operational shutdown was not ordered until around 9:00 p.m., after the fumes were spotted. When investigators located the source of the spill they found as much as three tons of solidified sodium."

http://en.wikipedia.org/wiki/Monju_Nuclear_Power_Plant

Out of the 10 fast reactors that actually entered commercial service 1 has had a significant fire - not a great safety record. Without its coolant you're left relying on thermal expansion of fuel pins to separate the fuel. What happens if a pin is cracked, or defective?

"This fuel is based on experience gained through > 25 yr operation of the Experimental Breeder Reactor II (EBR-II) with a uranium alloy metallic fuel. The ultimate criteria for fuel pin design is the overall integrity at the target burnup. The probability of core meltdown is remote; however, a theoretical possibility of core meltdown remains."

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=6178770

I agree it would be much better than what we have, but MSRs appear to have all the advantages of IFRs with none of the negatives.

[PamW]

16. Then you don't know the negatives.

I agree it would be much better than what we have, but MSRs appear to have all the advantages of IFRs with none of the negatives.
===============================

First, even IF the IFR had a pin failure and melting and the fuel dissolved in the liquid sodium; then you have EXACTLY the same cleanup problem that you ultimately have with a molten fuel reactor.

Expansion of the fuel in not the only mechanism. Another mechanism is fuel-assembly bowing. Because the fuel assemblies are "canned", i.e there is an outer "duct", the response to non-uniform temperatures as experienced in an accident will cause the fuel assembly to "bow" - like an archer's bow - convex side toward the high temperature side. In an IFR, the assembly is only restrained at the bottom, so this bowing causes the core to "flower" outward - and the resultant displacement negates the excess reactivity. An MSR lacks this feedback mechanism.

You are WRONG about the MSR having none of the negatives. The MSR has some negatives of its own when it comes to neutronic stability concerns. Because of the IFR's heterogenity between coolant and fuel, it has a very strong neutron resonance Doppler feedback that can terminate runaway reactor transients promptly. The MSR doesn't have that. The ability to promptly terminate a neutron runaway is one of the most important feedback mechanisms in my book. Again, fuel assembly displacement is also another feedback that the MSR lacks.

The MSR still has good transient feedback response as detailed in:

http://www.coal2nuclear.com/MSR%20-%20Stability%20Analysis%20-%20ORNL-TM-1070-ocr.pdf

However, it's just not as good as the IFR transient feedback response.

PamW

[PamW]

17. MSR doesn't have a record

Out of the 10 fast reactors that actually entered commercial service 1 has had a significant fire - not a great safety record.
===================================

MSR really doesn't have a record - the ONLY real reactor was MSRE.

MSRE operated for only 4 years; 1965 to 1969

EBR-II operated for 40 years without incident.

There's so little experience operating MSRs that you can't really say that just because you didn't have an accident in the 4 years that the single reactor operated, that is somehow better than EBR-II operating 10X as long, but then there is Monju.

Who knows what would have happened if the Japanese had built an MSR; they may have figured out a way to have an accident with that one too.

Both MSRs and IFR look to be very safe. However, with the extremely limited experience with MSRs; I don't think anyone can claim superior operational history over LMFBRs.

PamW

[kristopher]

15. 2011 MIT meta-analysis on which nuclear technology is recommended

For the next several decades, light water reactors using the once-through fuel cycle are the preferred option for the U.S. (pg. 1)
(The "once-through fuel cycle" refers to uranium, not thorium - k)

LWRs (light water reactors) will be the primary reactor choice for many decades and likely the dominant reactor for the remainder of this century. (pg. 4)

Fuel cycle transitions require a half century or more. It is likely to be several decades before the U.S. deploys alternative fuel cycles. (pg. 5)

Our analysis of thorium versus uranium fuel cycles (appendix a) found advantages and disadvantages for both fuel cycles—but the differences were not sufficient to fundamentally alter conclusions. (pg. 17)