I've tracked down better figures for uranium in seawater - the previous source I was suspicions of has it's decimals tangled.
Should be around 3ppm:
http://213.253.134.43/oecd/pdfs/browseit/6608031E.PDF
6608031E.PDF

This sounds reasonable, as thorium being around 3 times as abundant in the sea as uranium would tie in nicely with crustal abundances.
So by simply burning thorium instead of uranium, assuming the technology to get that from seawater is similar, which there seems no reason to doubt, the efficiencies Ugo suggests could be multiplies by 3 times, or maybe 4 if uranium could be extracted in the same process.

Since this has taken a just a few hours to work out, it does not seem as though any suggestion that this article proves the impossibility of ever obtaining all the nuclear fuel we need from the sea would be well founded.

David,

Your link says 3-4 ppb on p. 27, not ppm. This is in agreement with Ugo's table. On the other had, that figure is not better in any sense than what Ugo has given.

Chris

Sorry for the confusion - in any case, the point is that thorium is 3 times as abundant as uranium in the crust and seawater, if the decimal places would behave themselves.
Of course, no research has been done on the practicality of extracting thorium from seawater, as it is so cheap and abundant. if we do need to at some time in the future, decades away at least, at first blush it would appear that the economics of extraction and the EROI would be several times better than Ugo has suggested, even without assuming advanced burning technologies.

David,

I see the difficulty now. No, thorium is much less soluble than uranium: http://www.marscigrp.org/ocpertbl.html

Chris

Thanks for setting me straight on that Chris.
Scratch seawater thorium!

Good job there is plenty on land! ;-)

"simply burning thorium"

Burning thorium isn't that simple, I'm afraid. In short: There were (and are) several attempts to do this in pilot plants, but so far this wasn't successful.

My understanding is that thorium burn has been successful in CANDU reactors:
http://www.nuclearfaq.ca/brat_fuel.htm

If this is in error, perhaps you would supply better data.
Thanks.

I'm not an expert in this technology, but this was my conclusion I remember from a general research on this technology a few months ago. As for your weblink: Keep in mind that this document is from the Atomic Energy of Canada Limited, so the author may tend to have a rather optimistic look on the outcome. To be sure you should also check it with statements from neutral or sceptical entities.

I just grabbed the first one that came up on a list by googling, as it is, AFAIK, common knowledge.
If you don't like my link, do you actually have any links at all or information to support your statement?

Yes, of course, but from a certain point I concluded to discard this technology, so I didn't collect much data.
But if you find something that might convince me please free to post it right here or send me a short email.

Not a problem, and if I chance on anything authoritative I will forward it, as I have not bothered investigating as AFAIK it is not in question - incidentally the Westinghouse reactor is also supposed to be adaptable to burn thorium.
Perhaps it is worth pointing out though that I believe the conventions of this site, at least as I have observed them, are that when you are asked for your sources for statements such as you made you substantiate or withdraw - not liking the link I gave is on a different level to not having any backing at all.
I am not too bothered about it though, so unless I hear something from you which substantiates in some way your comment, I will continue in my previous persuasion.

I've spotted a more detailed discussion here:
http://www.world-nuclear.org/info/inf62.html
Thorium

You are correct in that not every issue is fully resolved especially the high cost of fabrication as thorium is cheap enough that reprocessing issues are hardly critical for the present, but the main reason for the lack of development appear to be the same as for all the more advanced techniques, that uranium is so cheap and plentiful at the moment that no-one has bothered to develop alternatives.
But to conclude from that that the difficulties are so severe as to warrant 'discarding the technology' as you have done is strange, and may perhaps indicate that you were in no mood to reach a favourable conclusion regarding the technology, IOW perhaps looking for an excuse to reject it.
Everything has some level of difficulty, and thorium technology is hardly unique in this.

Burning thorium isn't that simple, I'm afraid. In short: There were (and are) several attempts to do this in pilot plants, but so far this wasn't successful.

Wasn't successful?  I'm aware of two demonstrations said to be highly successful:

  1. The final fuelling of the Shippingport reactor (link).
  2. The Molten Salt Reactor Experiment.

I think you've sucumbed to the hype here about the molten salt reactor. It did not have a breeding blanket. It did run on U233 for a little while.

Chris

what does breeding have to do with burning it?  The U-233 bred from Th-232 burned just fine in both, and was bred nicely in Shippingport.

The MSRE did not require a breeding blanket to prove the system.  The elements of neutron economy were proven in the reactors which made the U-233 for its test, and Shippingport demonstrated an all-up system in a converted LWR.

The MSRE is an example of the kind of reactors which

  1. Require no pressure vessels or other large forgings
  2. Could be mass-produced in pieces small enough to move by standard trucks
  3. Can use spent PWR fuel to start
  4. Can recover their waste in forms ready for disposal,
  5. Can breed more fuel from thorium, and
  6. Can run at higher thermal efficiency because of the higher temperature of operation.

Do you propose that the U233 used was derived in a manner that was self-sustaining? If so, please provide details. Otherwise, stand corrected.

Chris

Define your terms, troll.

You're right, Chris.

The 1977-1982 Shippingport mini-reactor contained .55 tons of U-233 bred at a different breeder reactor and 40 tons of thorium to produce 235 MW thermal of power(60 MWe).

http://www.presidency.ucsb.edu/ws/print.php?pid=6972

If you want to evaluate the practicality of a thorium program you should look at India's nuke program which was required to use domestic thorium as fuel. They have 17 existing small(most <<500 MWe) mainly CANDU style heavy water reactors for a total for India of 3779 MWe, which is smaller than the largest single US nuke, Palos Verde and the largest nuke plant Japan's Kashiwazaki is 8500 MW.

The new generation of reactors for India are
uranium based and many of their current reactors
have been running half-loads due a shortage of uranium and are buying model Russian VVER-1000 design LWR instead.

They actually have a goal of 20000 MW of nukes in 2020. I believe they only think they can get there with uranium based technology.

Why is India ABANDONING thorium?
Well, they simply haven't been able to push the technology
and are still desparately dependent of uranium as I'm sure you can see as it is in the news(Singh-Bush agreement).

Thorium is certainly a fuel, but it currently will not satisfy nuclear cornucopians who are addicted to uranium whether they admit it or not.

http://world-nuclear.org/info/inf53.html

You are right to question the practicality of the thorium as a major nuclear program based entirely on thorium in India is switching to
uranium.

Rather than citing theoretical studies I'd like to hear the explanations for why this is happening in India from the thorium lovers.

Also CANDU heavy water reactors require much more heavy water than LWRs because deuterium is required for moderation AND cooling.

Abandoning the Nuclear Non-proliferation Treaty was a very grave error. One hopes that someone will have the guts to repudiate that move.

Chris