
Thorium Instead Of Uranium: Solution To Our Energy Woes? - johndcook
http://wmbriggs.com/blog/?p=2970
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DanielBMarkham
I'm a big fan of Thorium, but I'm also a big fan of nuclear in general. It
just makes sense.

In fact, this is a lot like the issue of not building any oil refineries in
the United States since the 1970s. While I'm sure there are good reasons for
our lack of needed nuke plants, at the end of the day it looks like the system
has let us all down.

I hate to sound like old cranky guy again, but frack, if you really wanted to
get off oil you could do the math for how many nuke plants you'd need -- it'd
be a lot! But it wouldn't be impossible, and we've known all of this for
decades. It's just very frustrating. Things like the thorium ideas just make
things worse because we can't even solve our problems using the old
technology, much less the new stuff. It's almost like rubbing salt in the
wound to see such potential and realize how improbable it will be to see the
light of day (in a massive production sense). I find the state of our energy
policy completely incredible, but the tech continues to look better with each
passing year. Sigh.

~~~
henrikschroder
Nuclear power plants can't replace oil- or coal-powered plants, because
nuclear plants can't adjust output over the day to fit actual usage. Nuclear
power plants are great for providing the baseline power production, but you
need something adjustable to handle the morning and evening peaks, like oil or
coal or wind or hydro or really big batteries.

So no, you can't do the math for how many nuclear plants you would need to get
off oil.

~~~
pjscott
France is using some of their nuclear plants to provide peak load, and they
adjust the power output of most of their plants over the day to better fit the
actual usage. Their reactors are not ideal for this; there are better ways to
design nuclear plants for load-following. But it can certainly be done.

Alternately, you could make enough nuclear capacity to provide your peak power
levels _all the time_ , and dump excess energy into some energy-hungry
industrial process, like aluminum smelting, or synthetic fuel production, or
ammonia synthesis.

So yes, you _can_ do the math. It's just that there are a bunch of different
ways to do that math, and most of them involve a lot of cleverness, large
budgets, careful engineering, and a fair dose of uncertainty.

~~~
hugh3
_Alternately, you could make enough nuclear capacity to provide your peak
power levels all the time, and dump excess energy into some energy-hungry
industrial process, like aluminum smelting, or synthetic fuel production, or
ammonia synthesis_

Heck, you don't _have_ to do anything with it, just disconnect your turbines
from your generators.

~~~
pjscott
Technically, sure. Economically, since most of the cost of nuclear power is
the capital cost of building the plants, you want to be running them as close
to 100% capacity as you can, all the time. If you can smelt some aluminum
while you're at it, that really helps.

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grandinj
This is a classic case of a solution to a problem that does not exist.

Firstly, Uranium is practically an insignificant cost of a nuclear power
station. The price would have to go up by a factor of a 100 before it made a
difference.

Secondly, the supplies of uranium are currently limited because the demand is
limited. The moment the price shifts up by even a little, supply will grow
because several other mining locations will become profitable.

~~~
Retric
We have already mined something like 100 years worth of Uranium that is just
waiting around to be used in power plants. Or, if the US moved to breeder
reactors we could go for something like 1000 years without mining any new
uranium.

~~~
terra_t
The trouble with fast breeders is that you need a huge fissile inventory to
get one started.

A study of the PRISM design, a modern fast breeder that uses integral
reprocessing to reduce the inventory of plutonium that's sitting around, not
fissioning, indicates that if we reprocessed all spent fuel in the U.S. today,
we'd have enough Pu to power about 33 MWe worth of breeders, about 1/3 of the
current fleet.

It comes down to energy vs power. "Fast" breeders can tap a huge energy
resource, but they can only produce a low level of power because they tap that
energy slowly. That's the whole reason they use highly reactive sodium as a
coolant; to reduce fissile inventory per unit of power, you need a coolant
with incredibly high heat conductivity. Lead is a much easier material to
handle, but a lead-cooled fast reactor has 1/3 the power density of a sodium
reactor, which means 3x the fissile inventory.

Fast breeders, therefore, can sustain energy production over a long period of
time, but they can't drive a rapid expansion of nuclear energy, like the
5-fold increase we'd need to replace fossil fuels and stop global warming --
it becomes hard to justify the economics of a plutonium economy in the same
way... You have to be thinking more than "seven generations" ahead to see the
economic boon.

Thermal reactors effectively trade a moderator material (water, graphite,
etc.) for (relatively scarce) fissile material. Thermal reactors (even today's
LWR) extract 10-20x as much power from fuel than do fast reactors with less
aggressive design (although the LWR extracts only 2% as much energy, in the
long term, as a breeder could.)

A thermal breeder, based on thorium, could provide the best of worlds. With
small inventory, it's possible to meet high power requirements, but by using
abundant thorium instead of rare U-235, be able to sustain that power for
thousands of years.

~~~
uvdiv
> if we reprocessed all spent fuel in the U.S. today, we'd have enough Pu to
> power about 33 MWe worth of breeders, about 1/3 of the current fleet.

That should be "GWe" not "MWe".

Also, I dispute your choice of statistic. Why not show what happens if you
start fast breeders on mined uranium, just like LWRs?

~~~
terra_t
Sorry I missed a factor of 1000. Fast breeders on mined uranium have the same
problem as plutonium breeders... Except you can breed plutonium faster (but
less efficiently) in LWRs!

~~~
uvdiv
I mean, it's an odd statistic. You can use U-235 directly, or you can burn it
in an LWR, getting back just 1/5th its equivalent in Pu-239, and use that. If
you're trying to maximize fissile input for fast breeders, LWR spent fuel
isn't an efficient way.

And moreover, with mined uranium there's no limit to your rate of expansion
other than mining. You don't have to sit and wait for your atoms to reproduce
(doubling time 20-40 years), when you can just dig up new ones.

Some back of the envelope numbers:

Assuming 3% enriched fuel burned to 40 GWd/ton, and 33% thermodynamic
efficiency, the US nuclear fleet (~100 GWe) consumes around 100 tons/year of
U-235 in fuel. At about 10 kg/MWe fissile inventory, just 10 years' of present
US uranium consumption would be enough (1,000 tons) to start up a 100 GWe
fleet of fast breeders -- same as the current LWR fleet.

I found a table of fissile inventories here:

[http://nuclear.inl.gov/deliverables/docs/msr_deliverable_doe...](http://nuclear.inl.gov/deliverables/docs/msr_deliverable_doe-
global_07_paper.pdf)

------
GiraffeNecktie
The short answer is that there are many entrenched interests who are not keen
on the idea: Uranium mines, nuclear industry, weapons manufacturers, not to
mention the oil, gas and coal lobbies, even the alternative energy suppliers
like solar. Thorium would rain on all their parades.

~~~
Retric
The real answer is the R&D costs are not worth it because Uranium is still
extreamly cheap. The fuel costs for a modern reactor are a small fraction of
total cost.

Also, fosil fuels a not going to be replaced with wind, solar, fission or
fusion any time soon because they are not really portable for anything smaller
than a boat.

~~~
sdurkin
You're both right.

"The real answer is the R&D costs are not worth it because Uranium is still
extreamly cheap."

This answers why the market won't develop the technology on its own. But the
government could still sponsor research as they did with uranium fission.

"The short answer is that there are many entrenched interests who are not keen
on the idea..."

And this answers why the government would never fund it.

~~~
wtallis
As soon as the market has to bear the cost of long-term storage of waste,
they'll be interested in thorium.

~~~
pjscott
That "waste" is still perfectly usable fuel. You could extract the plutonium
and uranium and use that to make more fuel rods. You could burn it in fast
breeder reactors, in a hypothetical future where mined uranium becomes
expensive enough to warrant the use of fast breeders. Or you could just ship
it to Canada, where they have heavy-water-moderated reactors that can use
regular nuclear waste directly as fuel, without any chemical reprocessing.

I keep saying that nuclear waste storage shouldn't be thought of as permanent
disposal. It should be thought of as keeping a reserve of nuclear fuel for the
future.

~~~
protomyth
To add, <http://en.wikipedia.org/wiki/Nuclear_reprocessing> \- see the last
two paragraphs in history for some problematic decisions.

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muhfuhkuh
I thought all of the arguments against nuclear were overwhelmingly about NIMBY
(not in my backyard). People just look at Three Mile Island and Chernobyl and
think "hell no."

Maybe after the BP spill, we'll think a little more about nuclear.

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ngvrnd
I've read somewhere that one problem with Thorium is it can easily be
converted to a fissionable isotope (of Uranium?) which _can_ be used to build
bombs. So there's that.

~~~
randallsquared
One of the anti-proliferation points is that U233 (which is the isotope you're
thinking of) is mixed with U232, which decays to products with high gamma
output, meaning that it's more dangerous to work with than the more typical
fissionable materials, and much easier to detect. For a state this probably
wouldn't be a significant barrier, but it's a fair point with respect to
terrorist bombs. Of course, we haven't seen any of those, which implies that
there's some non-obvious factor at work, here.

~~~
CWuestefeld
From the OP:

 _You will hear that we can’t make bombs out of U-233 because it is a virulent
gamma-ray emitter. This is not true, and I find it curious that it is used as
a reason. U-233 has a 158,000-year half-life. What they are referring to is
the protactinium-233 contaminant, which has a 27-day half-life, beta-decaying
into U-233 with gamma-ray involvement. Chemically scrub the protactinium, of
course, or just wait a year and it will be gone._

~~~
pjscott
No, that's wrong. The claim is that the bred U-233 will be contaminated with
U-232, which is very hard to get rid of, and has the hard gamma emitter
Thallium-208 in its decay chain.

~~~
tkeller
Where would the U-232 contamination come from, if it's bred U-233? Does
thorium also just sometimes decay into the lighter isotope?

~~~
pjscott
Sometimes the thorium, when it absorbs a neutron, will emit two neutrons and
turn into thorium-231, which decays (though a couple more isotopes) into
U-232. It can also be formed when U-233 absorbs a neutron and emits two,
forming U-232.

How hard this would be to separate depends on the type of LFTR design you're
using. However, you could also include some thorium-230 in the fuel mix to
denature any protactinium produced, so there's really no way around having
U-232 mixed with the bred U-233. Here's a blog post with more details on the
entire process:

[http://energyfromthorium.com/2006/10/06/denaturing-
thorium-w...](http://energyfromthorium.com/2006/10/06/denaturing-thorium-with-
ionium/)

~~~
ngvrnd
What about this?

<http://www.technologyreview.com/blog/arxiv/25855/?ref=rss>

------
whyenot
I'm all for thorium and nuclear energy, BUT only if we in the US stop with the
NIMBY-ing and find a permanent storage location for nuclear waste.

~~~
warfangle
No need for a 'permanent storage solution' for thorium waste. What little
waste there is decays to safe levels in less half a century.

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johndcook
The post doesn't give a definite answer to the question in the title, but it
is interesting.

~~~
ScotterC
It could be a plausible solution to our electricity woes to a degree. Mainly
in baseload electricity supply which is about 60% of the U.S. grid. Small
liquid flouride thorium reactors (LFTRs) can fit on a flatbed truck and mass
manufactured. The idea is that we can connect these to existing coal plant
secondary systems around the country and replace the coal boilers.

Thorium is extremely abundant. We have 3000 tons of it sitting in nevada
gathering dust because we have nothing better to do with it. Also, you can get
an incredible amount of energy and little waste out of a liquid thorium
reactor. See <http://energyfromthorium.com/>. That's Kirk Sorensen's blog. A
NASA engineer who's really led the movement on LFTRs and got featured in Wired
for it.

~~~
pjscott
If we can get the cost per megawatt of capacity low enough, liquid fluoride
thorium reactors could even be used for peak power. They can scale their power
output up and down pretty rapidly, since they would use Brayton-cycle gas
turbines for power conversion, and it's possible to continuously (or very
frequently) remove xenon-135, which is a neutron poison and has traditionally
made it harder to adjust the power output of nuclear reactors.

~~~
ScotterC
Isn't it wonderful how we've barely scratched the surface on what potential
fission has?

------
ericd
Wouldn't getting over our fear of reprocessing Uranium make this a non-issue?
That seems the simplest and most straightforward path... Just have to figure
out a way to lock down the resulting plutonium.

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magamiako
If you need lots of thorium you can usually find a ton of it Winterspring or
the Burning Steppes!

~~~
ScotterC
You can find it pretty much anywhere actually. It's a by-product of many
mining processes and India has literal beaches of it.

~~~
AndrewHampton
I believe magamiako is referring to areas in World of Warcraft where thorium
can be found.

~~~
pjscott
Incidentally, comments like that are why it's so irritating to try to have
discussions of thorium on Reddit. Of the people who post in those threads, a
significant fraction are just there to make WoW references.

~~~
hugh3
I have the same problem with discussions of Uranus.

