
Thorium Reactors - ivolo
http://rein.pk/thorium-reactors
======
uvdiv
_A “fast breeder” version of a molten salt reactor has fast neutrons in the
reactor core. These neutrons easily interact with the actinides, transmuting
them into fissile isotopes and then fissioning them to produce energy. In
other words, molten salt reactors burn actinides. The same is not true for
traditional uranium reactors because they have thermal (slow-moving) neutrons
in the reactor core. Neutrons at these slower speeds don’t interact with the
actinides, so you can’t burn actinides in a traditional uranium reactor._

This is no different from a panoply of fast breeder reactors which are NOT
molten salt reactors, particularly liquid-sodium cooled (solid-fuel) reactors.
The difference is that liquid sodium reactors have dozens of commercial-scale
demonstrations, and hundreds of billions of $$$ of R&D investment -- whereas
the molten salt fast breeders (chloride salt reactors) are nothing more than
paper models to date.

 _As a side note, it looks like using thorium as a fuel is not actually
critical. Thorium can be used as fuel in molten salt fast breeder reactor,
which is a benefit for long-term sustainability, but thorium has little
relation to the cost of constructing a new reactor today._

There's a plausible suggestion that liquid-fuelled reactors could be cheaper
than LWRs. E.g.: they are far more compact (smaller), and the nuclear
components apparently have less complexity. (Speculative)

But the point is an important one. The "big" selling points of thorium -- fuel
efficiency, and spent fuel -- are very long-term issues. It's safe to argue
they can be deferred. ("Thorium is premature optimization")

 _As of this past month, China now has a $350m institute with 140 PhDs
plugging away on molten salt fast breeder reactors._

Actually they are thermal reactors (not fast breeders), and the focus is on
solid-fuel reactors with molten salt as a coolant (although they are also
considering molten-fuel reactors, as a lower priority).

~~~
thingification
What you say about U/Pu fast breeders is true, but there are other pertinent
differences between those and LFTR:

1\. LFTR safety is based on passive cooling. Pu breeders do not share this
property. Fukushima-style accidents involving loss of active cooling power for
decay products are not a failure mode of LFTR.

2\. MSR reactors don't suffer from the safety problems introduced by the use
of liquid sodium.

3\. MSR reactors don't suffer from the control complications introduced by Xe
poisoning in solid fuels.

4\. MSRs involve a continuous liquid process. Essentially all industrial
chemical processes work that way, and that's because liquids are very
convenient to work with. There are good reasons to think this will pay off in
multiple cost-saving ways.

Another way of looking at the billions spent on Pu breeders is that it might
be an indication that other technologies are worth a bet. Orders of magnitude
less have been spent on MSR than on U/Pu breeders.

I'd say the big selling points of Th are not fuel efficiency and spent fuel,
for exactly the reasons you note. The big selling points are the promise of
lower cost and public acceptance (both of these promises come to a large
extent from the real safety advantages of MSR over conventional reactors).

The hard one, public acceptance, will only happen if we can figure out how to
sell it, but luckily, making that effort is something that those of us who
think we need nuclear power have a duty to choose to support, not something
that's in the lap of the gods.

Re China: it's possible my memory is playing tricks on me, but I believe that
one of the guys at the top of that program, when he came to a North American
conference to speak about it, said that MS as coolant was the initial focus
simply because that is a natural early step, but MS fuel was very much a long
term goal (it's on youtube if somebody wants to check). Edit: I just checked
(somebody already linked to it), and my memory was playing tricks: he said
that they're developing both in parallel, with the priority initially on MS as
coolant, because that is "more technically ready". It still seems that MS as
fuel is where they want and intend to go eventually.

~~~
uvdiv
Oh, thank you. I intended only a very narrow point about _chloride_ reactors
being untested (not MSRs: just _fast-spectrum chloride MSRs_ ). I didn't mean
to provoke a debate between molten-salt and liquid metal reactors. I claim
neutrality. :)

 _LFTR safety is based on passive cooling. Pu breeders do not share this
property._

I'm unfamiliar with the details, but I read that liquid-sodium reactors are
capable of fully-passive decay heat removal, e.g. [0] (slide 6). Certainly
sodium has a much higher boiling point than water.

By the way, fast-spectrum MSRs are really Pu breeders -- that's the point of
actinide burning!

 _3\. MSR reactors don't suffer from the control complications introduced by
Xe poisoning in solid fuels._

This is not a relevant issue with _fast-spectrum_ reactors, e.g. [1] (c.f.
[2]):

"The xenon-135 and samarium-149 mechanisms are dependent on their very large
thermal neutron cross sections and only affect thermal reactor systems. In
fast reactors, neither these nor any other fission products have a major
poisoning influence."

 _4\. MSRs involve a continuous liquid process. Essentially all industrial
chemical processes work that way,_

Pretty sure it's a batch process?

[0]
[http://rpd.ans.org/presentations/DesignFeatures_Economics.pd...](http://rpd.ans.org/presentations/DesignFeatures_Economics.pdf)

[1]
[http://www.hss.doe.gov/nuclearsafety/techstds/docs/handbook/...](http://www.hss.doe.gov/nuclearsafety/techstds/docs/handbook/h1019v2.pdf)

[2] Xe-135 absorption:
[http://www.nndc.bnl.gov/sigma/getPlot.jsp?evalid=15174&m...](http://www.nndc.bnl.gov/sigma/getPlot.jsp?evalid=15174&mf=3&mt=102&nsub=10)

~~~
thingification
Ah, I did notice you were talking about fast reactors, then hastily slid back
to thermal ones! Sorry. I guess my error reflects the fact that I think the
thermal LFTR is more important.

Re passive cooling in sodium breeder reactors: that's certainly interesting.
I'd not heard about this.

------
krschultz
Great article, I would love to see more of this kind of stuff on HN.

The 350 million dollar question is why the government _has_ to be the sole
source of funding. Obviously the cost is very high, the regulations are very
intense, but where are the VCs willing to tackle this kind of "startup" (in
reality it would likely be more of a public/private partnership). It's a
longer view with higher cost but the payoff could be massive. Big innovation
isn't going to happen if it requires congress to agree on supporting it for
10-20 years.

~~~
ChuckMcM
Reactor designs are licensed by the NRC, new reactor designs require quite a
long review process (as people really have a lot of "What if a ... happened?"
questions that need answers) So funding a new reactor design is a multi-decade
process. That is pretty far outside the "VC" range of funding since their
funds want to be 'done' in 10 years, not just "almost approved for considering
to build."

And the thorium folks, much as I love them, do themselves a disservice by not
addressing the fuel cycle problem. If a uranium 'water' reactor leaks the
radio-isotopes in the water decay rapidly, and are easily blocked by modest
shielding. So that steam that escapes into the big containment dome? Well its
radioactive initially but a couple of days later its not. This is not true is
U233, a necessary byproduct of a thorium reactor fuel cell and present in the
molten sodium leaks out. As sodium reacts violently with water, and molten
sodium leak will cause an explosion and disperse highly dangerous, and
difficult to shield U233 contaminated with U233 [1]

So when a thorium reactor does have a problem, it will be very serious very
quickly. Not a lot of understanding on how to protect against that yet.

[1] <http://en.wikipedia.org/wiki/Uranium-232#Uranium-232>

~~~
uvdiv
You're confusing molten-salt reactors with molten-sodium reactors (different
beasts). Molten fluoride is also reactive with water (hydrogen fluoride
anyone?), but often MSR proposals don't involve water (they go for helium or
CO2 gas turbines), and the ones that do separate steam far away from nuclear
components, through intermediate coolant loops. Sodium reactors do the same
thing. The risks really are manageable (in theory).

Radioactivity is dominated by short-lived fission products, not U-233/U-232
and company. U-232 is very radioactive, yes; but in a nuclear reactor, there
exist vicious things far more radioactive than that. (Note that U-232 is a
_trace_ contaminant, but fission products are present in bulk amounts. U-232
is highlighted only because it's impossible to separate from U-233, a point of
theoretical (and meaningless) debate involving nuclear weapons. Otherwise it's
unimportant.)

~~~
ChuckMcM
Yikes, I am mixing my reactor breeds (pun intended!) Thanks for that.

My understanding of the danger in the thorium fuel cycle and the U232
specifically is the _energy_ of its gamma radiation which is difficult to
shield.

~~~
uvdiv
It's relative. It's difficult to shield relative to U-235 (for example), which
means that handling raw fuel is more difficult. (It requires robotic
manipulators -- hot cells, "waldos" [0] -- unlike conventional fuels which can
be handled manually [1]). This is barely relevant for MSRs, because there is
no fuel fabrication step (no fuel pellets). It _is_ a difficulty for solid-
fuelled thorium reactors.

It's of no importance in nuclear reactors, because there there rest vastly
greater amounts of _vastly_ more radioactive monsters.

The reason people talk about U-232 is this confusing debate about nuclear
weapons -- there's a weak (I think spurious) argument that thorium is weapons-
resistant, because the U-232 gamma radiation makes it difficult to
machine/work with weapons cores. It's really not relevant to molten-salt
reactors.

[0] <https://en.wikipedia.org/wiki/Remote_manipulator>

[1] proof by photo:
[https://inlportal.inl.gov/portal/server.pt?open=514&objI...](https://inlportal.inl.gov/portal/server.pt?open=514&objID=1269&mode=2&featurestory=DA_528176)

~~~
thingification
U-232: I'm not sure that's really the good argument. The better argument is
that it doesn't matter whether it is weaspons-resistant, because it is much
easier to enrich U 235, even for U-poor countries. Is that argument also
flawed? Unfortunately, I suspect some of the relevant knowledge is secret.

~~~
uvdiv
_U-232: I'm not sure that's really the good argument. The better argument is
that it doesn't matter whether it is weaspons-resistant, because it is much
easier to enrich U 235, even for U-poor countries._

Yes, that's right. That's why the "debate" is spurious.

------
voidlogic
I'm not any kind of nuclear expert, but it sounds like the author is comparing
Molten Salt Reactors to 1970s era traditional reactors:

"and the decay heat from these products requires continuous cooling for weeks
even after core shutdown. That cooling process also must be human managed and
actively powereed."

My understanding is the reactors currently under construction in the US are
being built with passive fail-safes that make them much safer than the
1960s/70s reactors. Is this incorrect?

<http://www.world-nuclear.org/info/inf41.html#New_build>

~~~
uvdiv
_My understanding is the reactors currently under construction in the US are
being built with passive fail-safes that make them much safer than the
1960s/70s reactors. Is this incorrect?_

Modern passive heat-removal systems are limited: the ESBWR mentioned on that
page -- one of the most "advanced" -- has about 72 hours of heat-absorption
capacity. [0]

[0]
[https://en.wikipedia.org/wiki/Economic_Simplified_Boiling_Wa...](https://en.wikipedia.org/wiki/Economic_Simplified_Boiling_Water_Reactor#Passive_safety_system)

~~~
voidlogic
Thanks for the info.

`one of the most "advanced" -- has about 72 hours of heat-absorption
capacity.` That is still a pretty decent "oh shit" buffer. I imagine Fukushima
or Chernobyl would have benifited from 72 hours extra to get their act
together.

~~~
uvdiv
_I imagine Fukushima or Chernobyl would have benifited from 72 hours extra to
get their act together._

Well, I'm not sure. Chernobyl isn't relevant because its issue was one of
supercriticality (milliseconds, explosions), not decay heat (hours, gradual
melting). In Fukushima, there actually were passive systems, not as
sophisticated as ESBWR, and some failed instantly (a steam injector in reactor
#1). And IIRC off-site power too a lot longer than 72 hours to restore, but I
don't know if the explosions contributed to this. I'm not a nuclear engineer
so I can't meaningfully assess this. But there is data here.

As a curiosity, ESBWR is actually a direct descendant of the BWR/3 at
Fukushima, from the same designer (GE Nuclear). Not a scare tactic: I'd be
pretty happy living next to an ESBWR.

~~~
gus_massa
I'm not sure, but in the Wikipedia article I found that the electricity
problems in the Fukushima plant lasted from March 11 to March 22 at least (the
problems continued for a longer time).
[http://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disas...](http://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disaster#Cooling_efforts)

So 72 hours = 3 days would be not enough alone, but I also don't know how the
other actions had made the situation better or worse.

~~~
lemonad
The amount of cooling needed is not constant over time (cf.
<http://en.wikipedia.org/wiki/Decay_heat>), which is one of the reasons
passive cooling systems are designed for days rather than weeks.

The first seconds/minutes are the most critical and after 72 hours the
residual heat is down to a level which can be much more easily handled.

------
bd_at_rivenhill
One issue with the review of previous nuclear disasters: Chernobyl was
qualitatively different than Three Mile Island and Fukushima. The latter 2
designs were both water cooled and water moderated; both suffered loss of
coolant (LOC) events which resulted in the core melting from residual decay
heat as described in the article, with Fukushima experiencing subsequent
detonations of hydrogen gas formed from reactions with the heated fuel rods
(some have claimed that this happened at TMI as well, but clearly not to the
same scale). The Chernobyl design (<http://en.wikipedia.org/wiki/RBMK>) is
also water cooled, but is moderated by graphite, which is much more dangerous
(and scary that there are still many of these in operation). Instead of a loss
of coolant event, Chernobyl experienced an exponential power spike which
pushed operating power up to 10 times normal, resulting in a series of steam
explosions in the coolant lines that blew off the 2000 ton cover of the
reactor, sprayed part of the core out the top to contaminate the immediate
vicinity (i.e. large chunks of the graphite moderator lying on the ground
outside the reactor building), and set the graphite moderator on fire. The
fire then spread many more fission products into the atmosphere with the smoke
to share the fun with people in a much wider area.

Despite what has been written about Fukushima recently, I expect that it was a
couple of orders of magnitude worse than Three Mile Island, which did not
result in significant amounts of radioactive material escaping from the site
(depending on whose analysis you believe); Chernobyl was between 1 and 2
orders of magnitude more severe than what we know about what happened at
Fukushima at this point as far as I can tell.

~~~
dmfdmf
Good review but "qualitatively different" is a bit of an understatement.

tl;dr: Chernobyl/RBMK reactors are inherently dangerous in nuclear design and
in operation without suitable containment structures, unlike Western reactors
like TMI or Fukushima.

TMI and Fukushima are comparable to a degree but it is important to note that
TMI is a Westinghouse pressurized water reactor whereas the Fukushima plants
are GE boiling water reactors. TMI had a LOC event due to a stuck pressurizer
vent valve that went undetected after a reactor scram which, combined with
incorrect assumptions in the operating procedures, led to a core melt.
Fukushima experienced station black out which means loss of both offsite and
backup power. The reactors shutdown and operated as designed for this scenario
but the design basis assumption is that power would be restored in 4 or 5 days
(don't know the exact number). It actually took more than a week to restore
power due to the devastation of the earthquake and tsunami. Core cooling was
maintained by discharging steam into the containment cooling pools but this
method can not be run indefinitely and as the pools overheat it threatens the
containment. Without a source of power the H2/O2 recombiners could not safely
burn off the hydrogen which led to explosions of the reactor service
buildings.

In contrast, the RBMK reactors are graphite moderated but water cooled. The
reason for this design was they were developed for civilian power generation
by scaling up military reactors used for plutonium production for nuclear
weapons (graphite moderator allows fuel extraction without shutdown). During
low power operation, the RBMK design has a positive reactor power void
coefficient. What this means is that an increase in power lowers the density
of the water coolant which allows more neutrons to escape into the graphite
moderator where they are slowed down and thus split more atoms. In other words
these reactors have an inherently dangerous operating region where an increase
in power can lead to more power in a positive feedback cycle. This is what
destroyed the Chernobyl reactor. (Note that water moderated reactors such as
TMI or Fukushima have a negative power void coefficient where an increase in
power reduces the density of the coolant and moderator which allows neutrons
to escape the core without causing a fission thus dropping power, the opposite
of an RBMK)

Of course the designers were aware of the positive power void coefficient, so
they added safety systems to prevent reactor operation in bad regions. On the
night of the accident, a maintenance shutdown was scheduled but on scram the
operators wanted to run a turbine spin down test, i.e. after the scram, see
how long the residual steam could drive the turbines before backup systems had
to be operational. Previous attempts to run these tests had failed and the
operators were pressured by Moscow to get it done or else (Siberia?). To
maximize the chance of a successful test the operators maneuvered the reactor
into the low core flow, low power region of the reactor's operating domain
with the dangerous positive void coefficient and thus positive power feedback.
To get the reactor into this state the operators had to override numerous
safety systems designed to prevent such operation. At the commencement of the
test there was a power excursion that led to a power runaway that cause a
steam (not a nuclear) explosion that blew the lid off the reactor.

One final important point, the Chernobyl reactors (and all RBMKs) are not
housed in any containment structure like Western reactors (they are too big).
The containment buildings of reactors like TMI or Fukushima are designed to
withstand and contain the operating energy and nuclear material should
anything go wrong and as these accidents have shown, they work. The Chernobyl
accident was made much worse because the lack of containment allowed
widespread dispersion of radioactive material due to the explosion and
subsequent graphite fire.

~~~
bd_at_rivenhill
By qualitatively different I mostly meant to point out that TMI and Fukushima
were both LOC accidents at water moderated reactors, while Chernobyl was of a
much more dangerous variety. This was motivated by the fact that the OP
glossed over that important point, and now you have filled in even more of the
blanks; thanks.

~~~
dmfdmf
Yes, I just wanted to expand on how completely different these reactors and
accidents were. Also, it was a minor point but LOC Accident (TMI) is different
than a Station Black Out (Fukushima), these are defined accident scenarios in
the design basis documents for the reactors.

------
jakozaur
Thorium has an enormous potential, but R&D + regulations cost will be huge. In
case of the nuclear energy, they were covered partly by military, but that
would not be the case for Thorium.

I would be extremely happy, if instead of paying for war we would bet on that
technology, but unfortunately it is rather unlikely that it will became
commercial available soon. Still looks more promising than fusion reactor -
ITER.

~~~
InclinedPlane
Yup. Thorium isn't all sunshine and roses, there are some difficult
fundamental problems requiring novel research to tackle, aside from all of the
complex engineering issues of designing a real reactor. Uranium/Plutonium
fission power is already billions of dollars and decades ahead of Thorium in
those regards, so it'll likely be quite some time before a Thorium power plant
is able to compete head to head with a Uranium one.

More so, fission power in the developed world has been in a bit of political
trouble for the last 3 decades or so, no one is building new fission reactors
of any sort. Maybe the developing world can trailblaze the technology and
prove that it's an order of magnitude or more superior to fission power, which
might re-ignite interest for fission power in the US, Europe, and Japan.

~~~
pkrein
could you outline the problems with thorium reactors that you know of? i've
been searching high and low to figure out what they are. obviously they exist,
but they often seem brushed over and ill-defined. any extra light you can shed
on it would be useful. thanks!

~~~
fatbird
In every article about thorium reactors, I never see any real discussion of
drawbacks, or why uranium triumphed over thorium early, so I asked here the
last time this author's article was linked. I got good answers:
<http://news.ycombinator.com/item?id=4912614>

The short version is that the typical thorium reaction still requires/produces
U-232, which is weapons grade uranium, so you have all the same problems as
before regarding proliferation concerns; and more seriously, the product U-233
produces a lot of gamma radiation, which is really deadly at a distance and
terribly difficult/expensive to shield against by comparison to the
radioactive products of U-235/238 fission reactors.

Also, there's a general engineering issue that lots of work and research has
been done on current reactor designs, while little has been done on thorium
reactors, comparatively. Thorium looks good on paper, but there are bound to
be a bunch of practical issues that come up that raise the expense and
mitigate the advantages. Basically, uranium fission is far more advanced,
practically speaking, so a better bet for commercial applications.

ETA: And on reading the article linked above, I find that Mr. Reinhart
addresses neither of these two issues.

~~~
thingification
"there's a general engineering issue...": This is quite right. However, that
is a general-purpose argument to dismiss any new technology. I don't think the
rational response to that is to not develop new technologies that show promise
to be significantly better than the old ones, as this one does. While nobody
could disagree that we don't know for sure how much it will cost before
actually commercialising it, if we want to learn more about whether it is
worth a try, the argument has to focus on the specific issues, such as the one
you raise in your previous paragraph. (I think it is worth a try, because
there are reasons to expect that it will be cheaper and safer.)

To address your specific point about U 232: First, you have 232 and 233
reversed: it's the U 232 and not the U 233 that causes significant gamma
emission [1], and the U 233 that is bred from the Th for use as fissile
nuclear fuel. U 233 production from Th 232 also unavoidably produces a small
amount of U 232. The gamma emissions from the U 232 are a problem for handling
of U 233. However, the gamma rays (easy to spot from space) and the tricky
handling are both unattractive properties for U 233 as a weapons material. The
pro-Th argument goes that this means that it is much easier to enrich U 235
than it is to work with U 233. If that is the case, the proliferation
properties of U 233 are arguably not relevant to the LFTR debate (I'm
personally not yet convinced that it is the case).

You say that the gamma rays are "really deadly at a distance". Can you cite a
reference please? I don't think it is necessary to fully shield the gamma
rays, unless you are building a nuclear weapon and don't want it to be seen by
a monitoring satellite. Certainly the gamma emitters here don't constitute a
nuclear waste issue, because the reaction takes place quickly.

[1]
[http://www.princeton.edu/sgs/publications/sgs/pdf/9_1kang.pd...](http://www.princeton.edu/sgs/publications/sgs/pdf/9_1kang.pdf)

~~~
fatbird
This isn't an area of my expertise. I was only trying to summarize the
response to my earlier question. I think I understand the issues generally,
but please look at the linked conversation for more details.

I agree that engineering inexperience with thorium isn't a reason to dismiss
it. I just find it a bit telling that thorium boosters like Reinhold don't
address that discrepancy, in the same way they tend to be silent on the issues
with U-232/233.

Regarding gamma radiation, by "deadly at a distance" I mean that they're a
coherent threat to health at a much greater distance because gamma radiation
travels further than alpha or beta radiation because it's much higher energy.
Likewise, that greater energy imposes a much higher cost on shielding: a sheet
of paper blocks alpha, heavy clothing blocks beta, but you need significant
amounts of dense material like lead or packed earth or granite to block gamma
radiation. Presumably, this imposes a significant extra expense on a thorium
reactor that's breeding U-232. My source to back up my vaguely recalled
knowledge is this:
[http://www.epa.gov/rpdweb00/understand/protection_basics.htm...](http://www.epa.gov/rpdweb00/understand/protection_basics.html).

~~~
7402
Gamma radiation is not "higher energy" than alpha or beta radiation. And the
energy of particle is not by itself significant as far as radiation damage is
concerned - what matters is how that radiation is deposited in you as the
particle passes through you. An extremely high-energy neutrino could pass
through you with no effect whatsoever.

Materials such as a sheet of paper or piece of cloth have a higher stopping
power (loss of energy per unit distance) for alpha particles (helium nuclei of
charge +2) and beta particles (electrons of charge -1) than for gamma rays
(photons - uncharged particles).

This is why an alpha emitter is much less significant if it's outside your
body, but much more significant if it's in your lungs - because it dumps all
its energy inside you where it can cause damage.

~~~
lostlogin
I'm not sure if this is semantics or not. Yes, low energy and high energy
radiation both can cause bad damage and a DNA hit from one is as bad as that
from another, but that isn't the point. Standing in a 20KV beam is going to do
you more damage than standing in a 500KV beam on a photon by photon basis -
but only because more of the 500kV beam will go straight through you. An I
missing your point though?

Edit: Yes I am. Your talking about alpha versus gamma, not low energy damage
versus high energy damage.

------
Retric
There plenty of good things about Thorium, however the advantages are
generally overstated. Yes it's more common but uranium is plentiful and a
small fraction of operating costs. Yes, it produces less waste but The
difference is minimal. In theory it's safer, but current designs are vary safe
with a multi decade track record where Thorium's is unproven.

So, while there are benefits the ROI on a multi billion dollor Thorium R&D
progect are probably negative.

~~~
stcredzero
_> Yes, it produces less waste but The difference is minimal._

As far as I understand, the difference is _orders of magnitude!_

<http://en.wikipedia.org/wiki/Thorium#Benefits_and_challenges>

 _> So, while there are benefits the ROI on a multi billion dollar Thorium R&D
progect are probably negative._

It could be possible to rebrand Thorium and overcome many of the PR challenges
of nuclear power. A solution to a substantial part of the global warming
problem is indeed worth hundreds of billions.

~~~
danielweber
What do they mean by "long-lived waste"?

Things that are highly radioactive stop being radioactive very quickly. Things
that are lowly radioactive stay radioactive for a long time, but at low levels
so you don't worry much about them. There's a middle "unsweet spot" of things
that are radioactive enough to worry about but not radioactive enough that
they quickly burn out.

So where does thorium fit in that taxonomy?

~~~
uvdiv
_What do they mean by "long-lived waste"?_

Actinides of half-life 100-100,000 years or so. These have a compounding
disadvantage in that they are alpha-emitters, hence disproportionately
radiotoxic (e.g. by ingestion) compared to gamma- and beta- emitters like
common fission products. _Orders of magnitude_ disproportionate.

The theoretical advantage is huge: (this graph is from a French nuclear
research lab which appears to be temporarily offline)

[http://2.bp.blogspot.com/-m6Jl1KpnH3E/TiwB5Ppo85I/AAAAAAAAAD...](http://2.bp.blogspot.com/-m6Jl1KpnH3E/TiwB5Ppo85I/AAAAAAAAADE/wJvHAVmTN28/s1600/img18.gif)

------
jcfrei
There was an interesting study by the national nuclear laboratory of the UK
comparing thorium and uranium:

[http://www.decc.gov.uk/assets/decc/11/meeting-energy-
demand/...](http://www.decc.gov.uk/assets/decc/11/meeting-energy-
demand/nuclear/6300-comparison-fuel-cycles.pdf)

the article is difficult to understand for a layman as myself but an important
fact (among others) is that the uranium reserves on earth are considered to
last for 100 years at 2008 levels of consumption. furthermore if demand rises,
higher prices will make accessing more reserves economically viable. hence
resource availability doesn't appear to be a concern for the near term future.

~~~
uvdiv
_the article is difficult to understand for a layman as myself but an
important fact (among others) is that the uranium reserves on earth are
considered to last for 100 years at 2008 levels of consumption._

An even more important fact is that uranium nuclear power is a couple of
percentage points of 2008 energy consumption, and energy demand itself is
growing exponentially. The metrics the DECC bureaucrats are plodding through
are no-growth extrapolations of past trends. If clean energy is to be a
reality, and if nuclear power is that clean energy, then we _must_ scale it up
by three or more orders of magnitude, and sustainability within the century is
(potentially) a critical issue. DECC bureaucrats aren't considering this in
that report; they are being conservative, in a bad way.

Don't look to government bureaucrats for revolutionary vision ;)

~~~
dalke
"Don't look to government bureaucrats for revolutionary vision"

Which bureaucrats should we look to? ;)

You seem rather negative towards bureaucrats.

Some bureaucratic positions are influential. Some people have visions which
they can't do on their own or in a company. Some people figure out that the
best way to achieve those visions is to become an influential bureaucrat.
Vannevar Bush is one of those. He had a vision of how he wanted the US to fund
science research. That vision became the NSF. His bureaucratic work started
much earlier. For example, he was a key figure in organizing the Manhattan
project.

Other bureaucrats with vision include: Secretary of Commerce Herbert Hoover
(Hoover Dam, and more importantly the interstate compact which lead to it),
the Health and Environmental Research Advisory Committee of the DOE (to start
the Human Genome Project), J. C. R. Licklider (his DARPA memo on the
"Intergalactic Computer Network" lead to ARPANet lead to the Internet), and
Viktor Zhdanov, Deputy Minister of Health for the USSR (call for the WHO to
undertake a global initiative to eradicate smallpox; the previous smallpox
vaccination programs were also government driven).

------
tokenadult
Back in May 2012, I happened to be on a drive while National Public Radio here
in the United States was broadcasting a Science Friday story, "Is Thorium A
Magic Bullet For Our Energy Problems?"

[http://www.npr.org/2012/05/04/152026805/is-thorium-a-
magic-b...](http://www.npr.org/2012/05/04/152026805/is-thorium-a-magic-bullet-
for-our-energy-problems)

Many of the issues considered in that story are glossed over by advocates of
thorium reactors. The author of the blog post kindly submitted here explicitly
admits, "My last article about thorium as an alternative nuclear reactor fuel
drew way more readers than I expected. I intentionally glossed over the
complexities of specific reactor designs for the sake of simplicity, but in
this article I want to go deeper." He mentions a number of interesting
technical trade-offs involved in using thorium reactor fuel and the latest
reactor designs as compared to earlier nuclear reactor designs, but the tone
is still largely a tone of credulity, without a lot of examination of non-
nuclear means of generating electrical power.

The Physics Stack Exchange discussion of thorium reactors is interesting,

[http://physics.stackexchange.com/questions/20034/what-
practi...](http://physics.stackexchange.com/questions/20034/what-practical-
issues-remain-for-the-adoption-of-thorium-reactors)

as is the article from The Guardian in June 2011, "Don't believe the spin on
thorium being a greener nuclear option."

[http://www.guardian.co.uk/environment/2011/jun/23/thorium-
nu...](http://www.guardian.co.uk/environment/2011/jun/23/thorium-nuclear-
uranium)

Advocacy groups are already mobilizing to cast doubt on thorium reactors, with
webpages like "Thorium Fuel – No Panacea for Nuclear Power"

[http://ieer.org/resource/factsheets/thorium-fuel-panacea-
nuc...](http://ieer.org/resource/factsheets/thorium-fuel-panacea-nuclear-
power/)

(with a link to an interesting fact sheet,

[http://ieer.org/wp/wp-
content/uploads/2012/04/thorium2009fac...](http://ieer.org/wp/wp-
content/uploads/2012/04/thorium2009factsheet.pdf)

that gets into the practicalities and economics of using thorium as a reactor
fuel).

It's not clear yet that thorium offers any economic or political advantages
over the uranium that fuels the nuclear reactor that provides much of my home
electricity. The two nuclear reactors here in Minnesota result in lower-than-
average cost for electricity here, compared to the rest of the United States,
and have had a perfect safety record. Ongoing concern about where to store
high-level radioactive waste on a long-term basis has made many politicians
here reluctant ever to approve another nuclear plant in this state, despite
the perfect safety record and inexpensive electricity we enjoy with the
current plants. Minnesota, as a matter of state policy, is strongly promoting
wind energy, fitting the wind-swept prairie geography of much of the state.
I'm not aware of any part of the world where local politics would make a
thorium plant more likely than another wind power plant or natural-gas-fired
power plant. So maybe thorium power generation is a technical solution looking
for a problem.

~~~
apendleton
Not necessarily disagreeing with your main thrust, but this sentence: "So
maybe thorium power generation is a technical solution looking for a problem."
goes a bit too far. Certainly, there are it might be a _political_ solution in
search of a problem, but there are technical problems around waste,
proliferation, and safety that MSRs at least attempt to address, and they also
don't produce greenhouse gases the way fossil-fuel-driven generators do, and
have fewer outstanding technical question-marks than renewables (at least as
baseload power, a role for which huge technical challenges will need to be
solved before they can be considered viable). That still may not be good
enough, but there are clearly problems in current energy production that will
need to be solved somehow.

Also, aside: that guardian article isn't terrible, but the author gets half-
lives backwards the way lots of authors seem to, implying that elements with
long half-lives are bad, I suppose because we'll need to bury them for longer.
It's the elements with short half-lives that are scary; they decay really fast
and give people radiation poisoning/cancer/whatever. An element with a
16-million-year half-life is barely emitting anything at all; that's the
category of waste that can, as the author of this post says, be buried in a
shallow pit in the desert.

~~~
yk
I would argue that for the purpose of nuclear waste disposal the relation
between half life and problem is a bit more complicated than "getting it
backwards." The short half life isotopes are easily disposed of, because we
know how to build an organizational structure, that oversees the disposal. For
example, to securely store nuclear waste with an half life of a decade on can
simply coat it in some plastic and put it in a mine with a warning nailed to
the entrance. With very large half life times on the other hand there is no
big problem to begin with, as you stated.

But the intermediate timescale poses problems, since there the nuclear waste
is radioactive enough to be dangerous and we do not have a good idea how a
facility looks like, that can survive one hundred thousand years.

~~~
apendleton
Yes, I was mostly just pointing out that the "Ooh! 16 million years! Scary!"
attitude is bothersome, but you're right that I'm over-simplifying. My
recollection was that the thorium cycle produces a mix of very-short-lived,
deadly, gamma-emitting isotopes (U-232, I think? and possibly others) and
very-long-lived, low-risk stuff, with less intermediate-half-life transuranic
material left over, which made it rather preferable to the uranium fuel cycle
as far as waste disposal was concerned, but I may be misremembering. Either
way, the Guardian article doesn't deal with the issue in much depth or in a
way that makes it sound like they know what they're talking about, so I don't
trust their assessment of the relative merits of LFTRs vs. conventional
uranium LWRs.

------
varjag
The troubling attitude in TR advocacy is the claims of inherent safety.

A sustainable energy-positive reaction can't be inherently safe. You can argue
if it has better failure modes than the alternatives but it's harmful to
ignore a multitude of factors which could be not yet considered.

The previous catastrophic failures with other reactor designs were also not
exactly forethought. For instance, xenon poisoning was little studied in the
beginning of nuclear era. It is not implausible some critical piece of
knowledge is missing in the current evaluation of "safe" designs.

Another thing is too much reliance on the neat presentations. E.g. this blog
refers to a freeze plug as a kind of panacea of any mismanagement. What if
freeze plug fails for whatever reason? Like, tectonic activity breaks the
pipework, or it's sabotaged, or groundwater leaks into the dump tanks?

------
avar
I recommend the Thorium Remix 2011 for a good overview:
<http://www.youtube.com/watch?v=P9M__yYbsZ4>

------
rapind
Apologies for the off-topic comment, but I really love the layout and style of
this blog. Any chance it's not a custom jobby and someone knows where it's
from?

~~~
AlexDanger
I agree its amazing. Reminds me of svbtle.

~~~
rapind
Yeah, very similar, but I like it even more than svbtle.

~~~
rdl
I hate the misuse of the pk ccTLD, though. In general I don't care that much,
but anything related to nuclear technology related to Pakistan produces an
automatic "reach for the safety catch on my Browning" stress response.

------
realrocker
Indian Thorium Breeding Technology:
<http://large.stanford.edu/courses/2011/ph241/bhattacharyya1/> Since we don't
have enough Uranium and no one would sell us, It's pretty much our only
strategy.

~~~
uvdiv
You've been free to buy uranium from since George W. Bush backed you in a
treaty modification with the nuclear suppliers group. You had been blacklisted
before that, because your nuclear weapons pissed off the world (don't blame
the world).

[https://en.wikipedia.org/wiki/Indo-
US_civilian_nuclear_agree...](https://en.wikipedia.org/wiki/Indo-
US_civilian_nuclear_agreement#NSG_waiver)

A quick google search turns up the Australian PM agreeing to sell you uranium:

[http://www.abc.net.au/news/2012-10-18/gillard-visit-paves-
wa...](http://www.abc.net.au/news/2012-10-18/gillard-visit-paves-way-for-
india-uranium-sales/4319654)

 _"Prime minister Singh and I have agreed that we will commence negotiations
for the nuclear safeguards agreement, the civil nuclear cooperation agreement
given Australia is now prepared to sell uranium to India," she said._

~~~
justatdotin
well, that's one statement from the PM. it hasn't got through parliament yet,
and this highly controversial proposal will face stiff opposition. Successive
polls have shown that most australians are opposed to exporting our uranium to
nuclear weapons states (tho I'll admit most respondants probably haven't
connected the dots, since one major customer is us[a]).

In the case of India, these concerns are magnified by the ongoing regional
arms race and the recent violent suppression (including murder) of Indian
opponents to the industry.

~~~
uvdiv
It's only been a few years since India was "pardoned", and Australia is just
one of many potential suppliers. The broad point is, the entire world uranium
market is open to India, which was not the case until recently. India's
preexisting nuclear strategy is no longer valid.

Here's another sale: a settled Russian deal to supply uranium for a Russian-
built VVER reactor, for its entire lifespan. (Admittedly the implication is
the uranium deal is somehow _tied_ to the Russian reactor sale, which is
somewhat limiting). Not much politics here! (Not much politics in Russia
either).

[http://www.thehindu.com/news/national/first-unit-of-
kudankul...](http://www.thehindu.com/news/national/first-unit-of-kudankulam-
plant-undergoing-tests/article4210508.ece)

~~~
justatdotin
yes, the russians will on-sell to anyone: its probable that australia's
decision to supply russia, while not as politically charged, was a greater
proliferation hit than any future decision on india :(

------
twentysix
There was a TEDx talk I saw a while back by two MIT graduates working on a
"Waste Annihilating Molten Salt Reactor".

[https://www.youtube.com/watch?&v=AAFWeIp8JT0](https://www.youtube.com/watch?&v=AAFWeIp8JT0)

It looks promising and they have formed a start-up,
<http://transatomicpower.com>

[http://www.forbes.com/sites/pikeresearch/2012/09/27/a-pair-o...](http://www.forbes.com/sites/pikeresearch/2012/09/27/a-pair-
of-mit-scientists-try-to-transform-nuclear-power/)

------
ComputerGuru
His final point about a nuclear kickstarter project is made in jest, but may
be truer than he realizes...

~~~
sixdimensional
It's a wild idea... but has anybody tried it? Other than all the obvious
reasons why a nuclear Kickstarter project might not work, why the heck not???

It would be an interesting experiment to see the response, if nothing else.

NOTE: IANANE (I am not a nuclear engineer).

~~~
sixdimensional
Oh, I spoke too soon - try searching "reactor" on Kickstarter. Looks like the
idea is floating around (and some documentaries regarding same).

------
gatsby
Blake Masters has a great overview from Peter Thiel's Stanford CS183 class
about the future of Thorium and why it may be a very promising cleantech
energy solution:

[http://blakemasters.com/post/23787022006/peter-thiels-
cs183-...](http://blakemasters.com/post/23787022006/peter-thiels-
cs183-startup-class-14-notes-essay)

------
Create
As far as I know, there are no (public) models on Th reactors. The most
advanced is an analytic simulation (without CFD) from a Chinese nuclear
engineering lab, but nobody has a real clue about the precise input variables
anyway, therefore no MC is even in sight, as of today. But marketing is well
advanced.

And as the Japanese say, assuming we do have a functionally correct model and
a Th reactor design (or designs, since there are several configurations), that
still doesn't say anything about the economic aspect (I do not mean the old
economic model, where the byproduct of plutonium factories were sold as
energy).

------
Barosan
See this recent EnergyFromThoriumFoundation facebook album for a historic
brochure about ORNL's Molten Salt Reactor Experiment between 1965-1972.

[https://dl.dropbox.com/u/15726934/Historic_Molten_Salt_React...](https://dl.dropbox.com/u/15726934/Historic_Molten_Salt_Reactor_Experiment_Brochure_ORNL_1965-1972.pdf)

[http://www.facebook.com/media/set/?set=a.10152449471560377.9...](http://www.facebook.com/media/set/?set=a.10152449471560377.951501.10150132132910377&type=1&l=91f3ea2327)

------
justatdotin
s/weapons//g

hmmm.. thorium reactors would still produce unmanagable high level nuclear
waste (tho not as bad, not as much), and would still open up significant
weapons proliferation vectors, both material and capacity. As for safety,
these designs merely substitute one catastrophic failure mode (meltdown) for
another (volatility of the continuous onsite reprocessing)

inarguably, thorium designs offer stepwise improvements to the major
disqualifications of catastrophic failure, unmanagable waste production and
WMD prolifertaion. But I'm concerned that we should judge the nuclear industry
on its present day detriments and hazards, not the promises of future designs.

there's a big thorium mine down the road from me - well, a big rare earths
mine, where the dominant product is thorium. They're planning to come and bury
all the (enriched) thorium back on site after extracting the lucrative rare
earths. I read that as a pretty clear indication of the state of the market.
(incidentally, and as far as minesite impacts go, the thorium mine is going to
be at least as hazardous as a comparable uranium mine)

When Chernobyl went off, we were told don't worry, it's an outdated design,
the new reactors would never do that. When Fukushima went off, we were told
don't worry, it's an outdated design, the new reactors would never do that.
Who can guess what they'll tell us when Indian Point goes off?

this is an industry that has consistently over-promised and under-delivered.
Remember "energy too cheap to meter"?

by their deeds, not their words. let's try to manage the industry by the
realities of today, not the promises for tomorrow.

------
louischatriot
Of course thorium reactors is not a proven technology but if there is a
scientific consensus saying it is promising, I don't see why utility companies
and civil nuclear reactor manufacturers try to make it viable. They have
everything to gain, in my opinion.

Tldr of the article: [http://tldr.io/tldrs/50f73bbe983c81b86a00012b/thorium-
reacto...](http://tldr.io/tldrs/50f73bbe983c81b86a00012b/thorium-reactors)

------
j00lz
As much as I am interested in the topic. I could only read a few paragraphs,
due to being irritated by the cheesy couple picture in the corner.

------
raphaelj
The future is fusion

~~~
uvdiv
The near future is fission. Fission reactors are compact, dense, cheap, and
actually work.

------
martinced
I've got one question...

The main issue is that now at Fukushima there are products like Cesium-90 in
the sea, contaminating the entire sealife, which have crazy long half-life
(ninety years). Thankfully they're "heavy" so they go down towards the center
of the earth, but only at about 5 cm per year. So in ten years the're going to
be highly radioactive Cesium-90 at 50 cm behind rocks still polluting the
sealife.

In case the worst sh _t happens: the worst SNAFU conceivable...

Would MSRs also generate highly products like Cesium-90?

I mean: I don't care about all the security and the great design meaning an
uncontrolled reaction shall never happen.

I know: it won't happen. Just like Fukushima. It didn't happen because it
couldn't.

We got your point. It IS safe.

But I tell you: a sh_t you didn't expect is going to happen (maybe an asteroid
striking your reactor or whatever).

What then?

Would MSRs pollute less than Uranium based reactors in the worst of the worst
scenario?

If so I'm all for it.

~~~
thingification
It's intermediate half-lives that are problematic. Very long half lives (for
example, billions of years, like Th 232) are not a problem, because they have
low activity (few particles emitted per second). Very short half lives (for
example, minutes) are not a long-term problem, because they are entirely gone
after those minutes. It's the middling half lives that get you: short enough
to be highly active, long enough to stick around for years.

So, Cs 137 and I 90 stick around for a few hundred years. That's bad, and LFTR
still produces these.

On the other hand, it's a lot better than the situation with conventional U
reactors, because those produce transuranic elements with intermediate half
lives measured in tens of thousands of years. There is a qualitative
difference to human civilisation between 300 years and tens of thousands of
years. LFTR produces those transuranic elements too, but in orders of
magnitude less quantity -- that combined with the liquid phase leads us to
expect that would be a much smaller problem than with conventional reactors.

Wikipedia suggests some other LFTR advantages here, which I haven't thought
about:

[https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reacto...](https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor)

Low mobility of radioactivity. Even if there is an accident beyond the design
basis for the multiple levels of containment and passively cooled systems,
fluorides do not easily enter the biome. The salts do not burn, explode, or
chemically degrade in air and react only slowly with water. Fluorine combines
ionically with most fission products to form stable fluorides. This is not
only an MSFR's first level of containment, but also serves as a high inherent
safety level during any beyond-design basis event. Fluoride is especially good
at holding biologically active "salt loving" wastes such as cesium-137 and
strontium-90, which are permanently bound as stable, nonvolatile CsF and SrF2.
The fluoride salts of radioactive actinides and fission products are generally
not soluble in water at lower temperatures. Even though Caesium fluoride is
one of the fission product fluorides that is highly water soluble, its
extremely high boiling point and chemical stability, combined with the lack of
stored energy sources (hydrogen, steam, etc.) in the LFTR, prevent it from
being blown into the air and carried with the wind to contaminate a large
amount of land.[citation needed]

