Energy From Thorium Discussion Forum

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PostPosted: Jul 31, 2009 7:31 pm 
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Kirk Sorensen wrote:
Thorium doesn't work so well in LWRs--it can be made to work, but not particularly well. Uranium isn't so good in liquid-fluoride reactors--it can be made to work, but not so well. But put the right fuel in the right kind of reactor and you get much better results.

Thorium fuel is likely to be used in light water reactors before it is used in an LFTR, probably in Russia first. It shall produce U-233 in the process. Indians had to produce it in research reactors and PHWR for use in the AHWR. Final shape of LFTR is Th_U-233 fuel. Of course the Americans produced it in research reactors and dumped it.


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PostPosted: Jul 31, 2009 9:54 pm 
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Back to basics for me. What's the problem with heavy water reactors? They consume plutonium, natural uranium, LEU. Perhaps versions can run on thorium. They are constructed with tubes instead of enormous vessels. Reactivity control an issue?


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PostPosted: Jul 31, 2009 10:01 pm 
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For me I'd like the next gen reactors to have no explosives inside the containment.
No water, no heavy water, and no sodium.
Nothing that could make for interesting TV.


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PostPosted: Jul 31, 2009 10:18 pm 
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I should probably bow out of conversations among nuclear engineers, but I don't understand "explosives" an a priori problem. Certainly there are concerns about pressurized water propelling radioactive material. Certainly there are concerns about sodium catching fire. But you can't have that much contained energy without some risk. We live with gasoline fuel in our automobiles. I really do trust engineers to make the safety/performance trade-offs.


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PostPosted: Jul 31, 2009 11:18 pm 
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(By the way you are likely just as qualified as I am).

So do I. And in truth they are reasonably safe.

Unfortunately, nuclear power plants are not held to a reasonable standard.
They are much safer than any other power system and yet they are common viewed as dangerous.

If we have a good choice that does not include water or sodium inside the reactor then I think that should be preferred.
It is not that the current reactors are bad or dangerous but that there is a still better choice.

I'd like to see a 20x expansion in nuclear power.
It should come with at least a 20x reduction in the chances for a serious accident.

It is my impression that the engineered safety systems, the testing and verification of them, etc. is a significant portion of the overall cost.
(This is repeating what I've heard and it makes sense to me - I haven't seen a real breakdown of costs for a nuclear power plant).

I have no concerns about the new nuclear power plants going up now - except that they do cost quite a bit and I would hope there is some money left to develop LFTR.


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PostPosted: Jul 31, 2009 11:21 pm 
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Lars wrote:
For me I'd like the next gen reactors to have no explosives inside the containment.
No water, no heavy water, and no sodium.
Nothing that could make for interesting TV.


amen


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PostPosted: Aug 01, 2009 3:01 pm 
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robert.hargraves wrote:
Back to basics for me. What's the problem with heavy water reactors? They consume plutonium, natural uranium, LEU. Perhaps versions can run on thorium. They are constructed with tubes instead of enormous vessels. Reactivity control an issue?

The real problem with heavy water reactors today is that AECL has a problem with making them inexpensive.


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PostPosted: Aug 01, 2009 3:17 pm 
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dezakin wrote:
The real problem with heavy water reactors today is that AECL has a problem with making them inexpensive.


Not so. AECL have brought several CANDU projects in on time, and on budget outside of Canada. It is only in the crippling regulatory environment that has been created in Canada has it had issues.

A CANDU 6 or CANDU 9 can be built for about the same price as a comparable thermal plant if the process was not handicapped on purpose to make it non-competitive.


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PostPosted: Aug 01, 2009 6:43 pm 
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Lars wrote:
For me I'd like the next gen reactors to have no explosives inside the containment.
No water, no heavy water, and no sodium.
Nothing that could make for interesting TV.


Would you like it more if we put them outside the containment?

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PostPosted: Aug 01, 2009 11:28 pm 
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If you have a steam plant then it would be fine to have radioactive free hot salt crossing in and out of the containment and the steam outside.
In honesty this is an emotional reaction - I don't really know enough to be sure there is any significant risk - but if we have the choice then yes I would like a containment wall between any radioactive material and anything that wants to dramatically expand.

It has been fine so far, but with a 20x increase in deployment we need to be 20x better. Also, it may be that fission power needs to serve humanity for many times the 40 year history (of volume commercial operation) we have so far. Perhaps the gen 3+ have improved safety so much that this is not a real issue - probably so. But it is very hard to estimate very rare events. A single major incident with a modern power plant will have a major impact on the future of nuclear power. So rather than using engineered safety systems and trying to think of the various possible ways things could go wrong and be sure that none of them (or any combination of them) result in a significant accident I'd rather use a molten salt, that almost no matter what accident you conceive of, does something pretty boring.

No need to stop current plants or even those in process but lets develop LFTR and reduce the chances of a future problem.


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PostPosted: Aug 02, 2009 8:30 am 
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Of course your reaction is emotional...why do you think containment buildings are designed?

To prevent any release to the environment in extreme conditions of steam explosion, LOCA, sodium fire, fast reactor transient....

And as far as I know, not one containment building has failed so far! In MSR a hot cell around the reactor is needed to prevent the diffusion of radioactive products to the environment. It's simply a different containment approach.

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PostPosted: Aug 02, 2009 10:44 am 
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Ah but I think there will be a big difference in construction time between a containment for an MSR (w/o any water inside) and an LWR containment.
The size of the building I think will be much smaller.

If the construction time is much shorter then other indirect costs (like the chances that the rules of the game change after construction starts) will go down.


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PostPosted: Aug 02, 2009 1:07 pm 
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No one's ever claimed LFTR wouldn't have a containment. The claim is that it will be smaller and close-fitting and not have any explosive or expansive or reactive materials inside.


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PostPosted: Aug 02, 2009 2:11 pm 
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Lars wrote:
Ah but I think there will be a big difference in construction time between a containment for an MSR (w/o any water inside) and an LWR containment.
The size of the building I think will be much smaller.


That might be...however BWR's have also a different containment strategy compared to PWR, and I think (I'm not sure) that they have a construction time which is alike. Though that might be related to the heavy forgings which basically determine the biggest part of your construction time..

Lars wrote:
If the construction time is much shorter then other indirect costs (like the chances that the rules of the game change after construction starts) will go down.


Yes, but that's just a ridiculous argument. Or let's say a ridiculous way of regulating...From the things I know in my country, things have always been done in cooperation with the regulator and a lot was done before construction started. No last minute stops before construction was complete...
And if your plant was finished in a short time, extra regulations might force you to change things anyway...as have been done everywhere due to the increased precision of simulations and additional knowledge.

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PostPosted: Aug 02, 2009 2:34 pm 
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Kirk Sorensen wrote:
No one's ever claimed LFTR wouldn't have a containment. The claim is that it will be smaller and close-fitting and not have any explosive or expansive or reactive materials inside.

I would definitely argue against "close-fitting".

An LWR containment can be entered by workers for maintenance & repair -- in the worst case, following shutdown & even de-fuelling, if serious work needs to be done on, or in close proximity to, the reactor vessel itself.

This will NOT be possible in the case of LFTR.
There will be far more contamination & radioactivity, to allow human entry (which is why we need a hot cell).

Consequently, much floor space will be required to facilitate maintenance & repair by remote handling.
I figure there should be ample room for such things as a lay-down area for spare components, shielded areas for retraction of mobile inspection & manipulator systems, etc., etc.
In short, a floor space many times that taken by the reactor itself.

The old close-fitting hot cell designs are a sure prescription for economic disaster, as virtually no trouble-shooting is possible in case of component failure: That might be OK for an experimental reactor, but definitely not for a commercial plant required to last 60years or more...

Again, we need to look closely at how modern projects like ITER are handling this issue, as the solutions are likely to be similar.....


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