Monday, August 2, 2010

Not one good word for Uranium

The Debate of the week at Nuclear Townhall called for a trotting out of the old thorium versus uranium argument that goes back to an New Piles Committee argument between Enrico Fermi and Eugene Wigner during late World War II. At least that was the way it was pitched. The problem was the LFTR-Thorium side was out in force, while the IFR-Uranium side appears to have decided to talk only with God.

At any rate, the thorium side has been well stated, while the Uranium side has yet to show up. Barry Brook is traveling, and who knows what has happened to the other Uranium backers. Since both Kirk Sorensen and David Le Blanc have been thinking about building uranium fueled Molten Salt Reactors, maybe one of them will put in a good word for U-235 and U-238.


Joffan said...

I wasn't aware that the particular debate was uranium vs. thorium. So far it seems to be an interesting discussion of the potential of thorium. If you were expecting a horde to descend decrying the possibility of thorium use, swearing allegiance to uranium, I guess you were looking for a different debate.

I have noticed an occasional descent into uranium bashing by sincere thorium advocates, but not so much the other way around.

Charles Barton said...

There have been a few heated arguments between LFt'R and IFR supporters in the past, although not recently.

LarryD said...

In principal, a MSR can burn either uranium or thorium, how much difference is there in practice?

What I'm ultimately getting at, is, could a MSR be designed/built that can start with uranium (which we have a lot of on hand) and be switched to thorium later, as the thorium supply is developed? How much more expensive would it be? Cheaper to just replace? Other issues?

Charles Barton said...

Larry,LORNL tested the MSRE with u-235, Pu-239, and U0233. It ran successfully with all three, Because the thorium. U-233 breeding cycle has a beter neutron economy in the thermal neutron range, it is possible to breed with thorium, but not U-238. However, by changing the salt formula you can increase neutron speed, and in fact it is possible to create a fluoride salt formula that will produce fast neutrons. That makes it possible to breed U-238, However it takes quite a lof of fissionable material to start a Liquid Fluoride Salt Fast Breeder.

LarryD said...

So it would be a viable option to start with uranium burning MSRs, using up Spent Nuclear Fuel and depleted uranium while developing the thorium resources.

This has the advantages of cleaning up the Spent Nuclear Fuel and using up some of the hundreds of thousands of kilos of DU we have in storage.

Charles Barton said...

LarryD, It would be an option. Considering how much U-235 and/or RGP it would take, I won't vouch for how viable the option would be.

Frank Kandrnal said...

After 65 years we are still debating between Uranium and Thorium fuel cycles. Eugene Wigner would turn over in his grave if he could watch the confused humanity.
Today, it makes no difference. The mixture of Thorium, Uranium and Plutonium will be used in various reactors long into the future, so forget the differences and get on with building more reactors.
What is more important is the cost and ultimate safety of nuclear energy. The LFTR addresses these challenges with clear advantage.

Robw said...


Isn't what LarryD is saying the same thing that physicist David Leblanc is proposing with the DMSR?...or am I confused?

Rob W.

Charles Barton said...

Rob W, It is impossible to breed uranium in a thermal reactor environment. While it is possible to breed uranium in a fast reactor environment, fast reactors also require 10 times the amount of fissionable material to maintain criticality. Thus a tone of U-225 or Pu-239 would start a 1 GW moderated MSR, or a a 100 MW fast reactor. This problem was one of the major reasons why Eugene Wigner and Alvin Weinberg preferred Thorium cycle thermal breeders. You could build 10 times as many with a given supply of fissionable materials and still breed new nuclear fuel.

LarryD said...

I'm concerned with two things.

1. How to get from where we to where we want to be.

2. How to deal with the Spent Nuclear Fuel (and to a far lesser extent, depleted uranium) resulting from decades of "conventional" (i.e., LWR) nuclear power.

Initial deployment of MSRs as SNL "burners" deals with #2 directly, establishes in people's minds the MSRs are not a contributor to the nuclear waste issue, but a solution to it, and is an initial step towards a larger deployment of MSRs, using whatever fuel mix makes sense.

Currently, the fuel available is a mix of isotopes of uranium and plutonium. Thorium currently has no industrial use, hence there is no thorium mining/refining industry in place. Since it shows up as a component in many rare earth ores, we know where a lot of it is. But outside of India, there is no demand. And India is just dealing with the fact that they have good internal sources of thorium, but not of uranium.

Once we have MSRs in place, thorium will an advantageous upgrade to an existing power facility, rather than a fuel for a projected power facility. I.e., it is a cheaper, lower risk step from a U/Pu MSR to a LFTR, than from nothing to a LFTR. And usefully disposing of SNL is a sufficient justification for going from nothing to a U/Pu MSR.

Kirk Sorensen said...

Larry, you captured my thoughts exactly. An MSR based on burning fluorinated SNF is an excellent step towards a LFTR.

Barry Brook said...

Go U-RA-NIUM, rah, rah, rah! U-RA-NI-UM forever, go, go, go!

There, my cheering over. For more details, read my blog, especially my upcoming 'travel diary' posts where I describe my visit to the Argonne West site and the EBR-II.


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