
Molten Salt Reactors - zeristor
https://whatisnuclear.com/msr.html
======
jillesvangurp
The elephant in the room with any kind of fission reactor is that they are
going to need a lot of security. Even when the fuel and waste product is not
weapons grade uranium, it's still highly radioactive and a great source of
material for a dirty bomb. Basically anything that goes boom combined with
small amounts of radioactive material and a bit of wind is a great way to
depopulate e.g. large cities. So, having lots of small molten salt reactors
all over the planet, which seems like the key selling point, is not a great
idea from that point of view. Having them in or near any kind of conflict zone
would be super risky. And according to this article there is actually some
weapons grade uranium being produced as well which makes this even more
problematic.

The security aspect would make this a lot more expensive than it already is
and cost is already on the high side even before you consider that. This is a
problem with traditional reactors as well but they have the advantage that
they are huge facilities and that there are only a handful of them; so
securing them is relatively easy.

People are suggesting this as complementing renewables but the cold hard truth
is that renewables are already dirt cheap and on track to continue to drop in
price by magnitudes for the next decades. That includes battery storage as
well. Already quite cheap, also dropping in price, and typically already
factored into e.g. new solar bids that are killing competing bids for coal and
gas plants (or in some cases shutting them down prematurely).

Even at the current prices, that's a problem for any kind of nuclear solutions
being contemplated right now. At the low end of the spectrum, we are talking 2
cents per kwh currently. Imagine this dropping to something like half a cent
or even less. At those prices, the security alone would make nuclear too
expensive probably. A 1 mw facility would have basically be generating only
about 500-2000$ worth of energy per hour but only at peak demand. There's no
guarantee prices won't drop way below that either. Any kind of operational
overhead would be a problem. Needing 24x7 intense security would be very
undesirable.

~~~
acidburnNSA
Are you suggesting that variable renewables plus batteries will approach
prices that are... too cheap to meter?

Looking at current cost VRE trends, when variable sources contribute up to 4%
of world energy, and surrounded by massive amounts of cheap but high-carbon
natural gas, and assuming that the trends will just continue exponentially
downward without serious complication, is optimistic.

Cost of integration of variable sources plus batteries is expected in many
studies and somewhat intuitively to skyrocket as market penetration increases.
When you have enough VRE to cover 100% including the big evening peak with
batteries during a clear summer day, the extra generation you build to fill
the other gaps gets curtailed. But you have to fill daily and then seasonal
gaps, worldwide, including heat in winter and worldwide transportation (not
just electricity). Buying that battery that is only even needed at all every
third day is 3x the price, yet we prefer if the power doesn't brownout with
this frequency. This is difficult. Already we're seeing NIBMYism in large
solar installations in california and with transmissions lines. That gets
worse with scale.

Nuclear today is a hedge against the possibility that deeply carbonizing with
variable renewables + storage at world scale will be harder than we all think
and hope it will be.

That said, nuclear certainly needs to drop capital and O&M cost dramatically
if it wants to play the game. And security is indeed a big factor in this. Its
competition in the small-footprint dispatchable world is natural gas with full
CCS, which is also looking pretty cheap.

~~~
jillesvangurp
Yes. Not indefinitely of course but we've seen nothing yet and there's enough
in the research pipeline to suggest clear trends over the next two decades in
terms of cost improvements, efficiency improvements, cheaper materials, etc.
That 4% you mention was less than 1% not so long ago and will be closer to 40%
not too long from now. Such is the nature of exponentials.

IMHO 5X cost reduction is basically a done deal even just applying simple
economies of scale. You can argue whether this happens in five or ten years
maybe but arguing it isn't happening seems futile. Beyond that, 10x is
extremely likely to happen as well. There's a lot of research happening that
would need to be a complete failure/waste of time for that to not happen. At
worst it will happen slower that I might like. Maybe this happens over the
next decade. Or two. Or three even. From there, 20x might be quite possible as
well.

Beyond that we're indeed talking rapidly diminishing returns. 10X would mean
0.2 cent/kwh. 20x would cut that to about 0.1 cent. This indeed gets you in to
territory where metering it becomes more expensive than is worth the trouble.
The average household uses about 15000 kwh per year, or about 150$ worth of
energy at these prices; much less outside the US. Much of that is going to be
produced on people's roofs or in their back yards. At that point it turns into
a fixed cost.

Historically the same sources producing the studies you are referencing have
been off by magnitudes predicting current adoption and prices for both solar
and wind. So, I'd consider that the pessimist glass half empty point of view.
Not to dismiss it entirely but arguing cost increases seems a bit far fetched
in light of current trends in the market.

~~~
Mirioron
Aren't roof solar panels very inefficient? They can't track the sun and you
can't have good density from them either. Furthermore, they don't work for
office buildings and apartment buildings.

> _Not to dismiss it entirely but arguing cost increases seems a bit far
> fetched in light of current trends in the market._

I think what the parent was saying is that because solar and wind don't
reliably produce energy, we will need redundancy. As the market share of solar
and wind grows we will need to increase the amount of storage and power
generation far beyond what we normally need to operate.

Let's say you have a city that uses 1 GWh of electricity per day. If you were
to generate all the electricity with natural gas then you need to have 1 GWh
plus _some_ extra for redundancy to fulfill the needs of the city. If you
generate 5% with solar and the rest with natural gas then nothing really
changes. If the weather is bad then the natural gas plant will step in.

As the share of your solar power generation grows toil need more and more
redundant storage and solar power generation. If you rely 100% on solar power
generation and the weather can be bad for a week in a row over the city, then
you'll need storage that will last for more than that entire week. Not only
that, you'll also need extra power generation capability to be able to fill
and maintain that storage.

Just to put this into perspective: the US uses about 10 TWh of electricity per
day.

~~~
jillesvangurp
> Aren't roof solar panels very inefficient?

They are good enough. Low efficiency just means we have to buy more of them.
Obviously we'd need solar plants (and maybe wind parks and other clean
sources) to also power those with limited access to roof surface.

Of course, bad weather doesn't mean solar stops working; it just reduces the
output. The effect is typically very local as well. So, all that means is that
you need a bit extra capacity to cover for that or import energy from
somewhere else where the weather isn't miserable.

When (not if) the price for solar and wind drops 10x, you'll be able to buy
10x more than what you need and still beat coal/gas/nuclear on price. 10x is
an insane safety margin that would mean you produce more than you need even on
the most cold, dark, and miserable day imaginable. And of course solar is not
the only source of clean cheap energy. Wind would be another popular option.

~~~
Mirioron
Bad weather in northern Europe means that everything is covered in snow for a
long time. I think that's slightly more than just reduced output. The snow
also tends to cover am area that's hundreds of kilometers in every direction
too.

~~~
jillesvangurp
I've lived in Sweden and Finland. It's actually the lack of sunlight that is
causing issues with solar. The snow is much less of a concern. E.g. Helsinki
only gets a few hours of daylight and the sun does not get much above the
horizon in the winter months. The reverse is true as well; you get insane
amounts of sunlight in the summer months. Luckily there's wind, hydro, wood
pellets, and a few other alternatives.

Further south in Germany, Netherlands, etc. Solar is usable throughout the
year and quite common. Obviously output in the summer is going to be much
better than during the winter.

------
AtlasBarfed
I thought LIFTR was the coolest thing ever. MSRs could have revolutionized
power generation... about two decades ago.

Solar/Wind/Storage are beating almost everything. Everything they aren't...
they will, very soon.

It's possible that MSRs could be scaled down and their liquid nature means
that the reactor could simply be replaced on a schedule and the entire old
reactor "reprocessed". But the investment won't be there with
wind/solar/battery eating everyone's lunch.

And that's IF regulatory was simplified and IF you were able to get enough
starting fuel to initiate breeding of the thorium.

~~~
Mirioron
Renewables have the problem that the larger the portion of your power that's
generated through these renewables, the exponentially more storage you need.
It's not a linear relationship, because you can have weather that doesn't
cooperate for long periods of time, but the power can't go out.

Another issue is that solar and wind aren't really suitable everywhere. The
further north you go the less economical solar becomes. A large chunk of
Europe sits further north than the US.

~~~
audunw
What’s happening right now is that renewables are being paired with an
increasing number of gas power plants. Since gas power can ramp up so quickly
they’re a good match until storage can take over.

So I think we already have the solution to the problem you’re describing: just
pay to maintain a decent amount of the existing gas power plant. If they’re
only there for backup, the impact on CO2 emissions will be negligible. You
could even make the gas from renewable sources, since in this scenario the
cost of the gas itself is negligible compared to cost of keeping the power
plant operational.

This is incidentally another reason (current) nuclear is a dead end going
forward. They’re a bad match for renewables. What we need isn’t more base
load, we need more peaker plants, load following plants, backup plants and
energy storage. Nuclear isn’t a good solution in any of these categories.

~~~
olejorgenb
Any increase in base load would reduce the amount of renewable+gas/storage
capacity needed, so at worst it's a neutral match for renewables.

------
petschge
The usual quip in the industry is that the remote maintenance is such a
complicated robotics problem. that which ever company is able to solve it, is
better off converting to a robotics company and just drive Kuka, Fanuc and ABB
out of business.

~~~
ambicapter
Is it a hard robotics problem or a hard radiation-hardening problem?

~~~
TaylorAlexander
Completely robotically maintaining a complex machine sounds like a hard
robotics problem to me. Of course it can be designed for machine manipulation
but that seems like a pretty complex fusion of robotics and nuclear reactor
design. So I think it would be a lot of work.

~~~
darkpuma
It seems to me that the simplest reactors tend to be the most dangerous. I'm
thinking of the Windscale fire and SL-1 in particular. One of the theories for
what went wrong at SL-1 is that it was a murder-suicide, caused by the man
tasked with physically manipulating the control rods of the reactor. I think
robotic control is better for something like that. Robots are more
predictable.

One of the aggravating factors at Windscale was their inability to perform
maintenance tasks behind the reactor. They had canisters of radioactive
material smashing open behind the reactor and it took them ages to even
notice. That was a _very_ simple reactor design; basically a nuclear pile. It
was also an awful design that was irradiating England even before it caught
fire.

~~~
tim333
The Windscale reactors were built in a hurry in 1950 to produce nuclear
weapons after Russia managed to test it's first atom bomb in 1949 and are not
really representative of modern power generating technology.

~~~
darkpuma
Obviously Windscale wasn't modern and SL-1 certainly wasn't either. My point
was that simple designs are poor designs, that modern designs are complex for
good reason. The added system complexity of automation is well worth it when
it comes to nuclear power.

------
achalhp
From the article: >if something goes wrong in a MSR and the temperature starts
going up, a freeze plug can melt,

A MSR does not need any sort of valve to drain the fuel. ORNL-MSBR was
designed to drain the core when pumps stopped working. The real advantage of
freeze valve is that is uses no moving parts and _maintanence_ free/friendly.

ORNL-4528: "The fuel salt pump and its sump, or pump tank, are below the
reactor vessel, so that failure of the pump to develop the required head
causes the salt to drain from the reactor vessel through the pump tank to the
fuel salt drain tank."

------
fnord77
> Protactinium-233 decays to pure, weapons-grade U-233

~~~
jlhawn
I thought it was Uranium 235 which was the common weapons material, so I
looked up Wikipedia [1]:

> ... While it is thus possible to use uranium-233 as the fissile material of
> a nuclear weapon, speculation[8] aside, there is scant publicly available
> information on this isotope actually having been weaponized ...

[1]
[https://en.wikipedia.org/wiki/Uranium-233#Weapon_material](https://en.wikipedia.org/wiki/Uranium-233#Weapon_material)

~~~
acidburnNSA
In the nuclear industry, U-233 is well known as an excellent weapons material
[1]. It's simply a matter of its nuclear properties, which are well known.

"The fast critical mass of U-233 is almost identical to that for Pu-239 and
the spontaneous fission rate is much lower, reducing to negligible levels the
problem of a spontaneous fission neutron prematurely initiating the chain
reaction -- even in a “gun-type” design such as used for the U-235 Hiroshima
bomb (see Table 1)."

[1] U-232 and the Proliferation-Resistance of U-233 in Spent Fuel -
[http://scienceandglobalsecurity.org/archive/sgs09kang.pdf](http://scienceandglobalsecurity.org/archive/sgs09kang.pdf)

------
nimish
The big problem with nuclear driven steam turbines is that they cannot be
cheaper than thermal coal driven steam turbines due to costs-- construction,
operation and decommissioning. Their LCOE is just not great and not lowering
quick enough.

Even thermal coal is getting out priced by solar/wind+ batteries. And the
latter will always get cheaper due to economies of scale and learning rate
reductions not to mention core technological advances.

Nuclear would have kept us out of the carbon free energy mess decades ago but
it's not the answer in 2019.

------
achalhp
>Tritium production: If lithium is used in the salt, tritium will be produced,

Not a disadvantage for all MSRs. Both lithium and beryllium can be avoided.
FLiBe is required for efficient MSRs and MSBR.

>Mobile fission products

It is the only disadvantage common to all molten-salt reactors and all fluid-
fuel reactors. Pumps and pipes have to handle a hot radioactive liquid.

> Material Degradation

Common to all nuclear reactors, solar, coal boiler tubes, etc. Components used
in reactor core do not last long. MSRs dispose nickel tubes and LWRs dispose
zirconium tubes and uranium.

>Proliferation...The problem with MSRs, then, is that the fuel is already
completely cut open and melted. >it will be difficult for the IAEA to
distinguish plate-out losses from actual proliferative losses.

The fuel salt loop can be sealed tamper-proof. The entire fuel salt loop is
analogous to a fuel assembly. Weigh the entire fuel salt loop. Vapor pressure
of actinide-halide salt is very low at operating temperatures. Actinides don't
move out of this loop.

~~~
DennisP
Regarding pumps and pipes, the Moltex design avoids them entirely. Liquid fuel
is contained in vertical fuel rods, open at the top to allow escape of gaseous
fission products (some of which are strong neutron absorbers). The pipes are
mostly immersed in a pool of molten salt coolant.

[https://www.moltexenergy.com/](https://www.moltexenergy.com/)

------
pweezy
> Molten salt fuels were first conceived of in the late 1940s, when people
> began thinking of nuclear powered airplanes! > The idea was to have very
> long range bombers in the air at all times

I had never heard of this idea, and thought it was super interesting. Imagine
aircraft that could stay in the air indefinitely (for some practical
purposes), carrying massive loads without fuel being a concern.

Similar to nuclear aircraft carriers and submarines, at least conceptually.

[https://en.m.wikipedia.org/wiki/Nuclear-
powered_aircraft](https://en.m.wikipedia.org/wiki/Nuclear-powered_aircraft)

~~~
Symmetry
In the long run nuclear jets could be really useful for the exploration of
planets that don't have free oxygen in the atmosphere like Venus, Saturn, etc.

------
achalhp
>Complex chemical plant

This is not a disadvantage for all MSRs. Only breeders need chemical plant.
Not fair to compare a solid-fuel burner to liquid-fuel breeder.

Let us compare liquid fuel breeder vs. solid-fuel breeder: Reprocessing solid-
fuel involves more complex chemical plant with physical mechanisms to declad
and convert solid-fuel to a processable liquid. Fabricate processed liquid to
solid-fuel and put it back in the reactor. Solid fuel breeders have additional
physical and chemical processes/steps.

------
sandGorgon
The largest reserves of thorium exist in India and China - two of the most
energy hungry and polluting economies. One is on the UN Security Council and
the other has a unique waiver from the US Congress on proliferation - so
fissile material production is not the primary concern.

Both India and China have massive deployments of renewable energy, yet the
demand for energy is outstripping projected build-out. LTFR is going to be one
of the best answers if it can be made safe.

~~~
sien
[https://en.wikipedia.org/wiki/Occurrence_of_thorium](https://en.wikipedia.org/wiki/Occurrence_of_thorium)

From there it seems like India, Australia & the US all have large thorium
reserves.

There is certainly heaps of it.

~~~
sandGorgon
not disagreeing. however, the hunger for energy in India and China is causing
outsize investments in MSR.

For example - [https://www.nextbigfuture.com/2017/12/china-spending-
us3-3-b...](https://www.nextbigfuture.com/2017/12/china-spending-
us3-3-billion-on-molten-salt-nuclear-reactors-for-faster-aircraft-carriers-
and-in-flying-drones.html)

------
w0mbat
Or just use that money for solar panels and batteries and not build a
combination power plant / doomsday weapon.

~~~
acidburnNSA
MIT studies suggest that deeply decarbonizing is actually cheaper when you do
some nuclear alongside your variable renewables + storage [1]. The cost of
filling those seasonal solar gaps and 10-day wind gaps gets pretty large
without nukes.

[1] [https://energy.mit.edu/research/future-nuclear-energy-
carbon...](https://energy.mit.edu/research/future-nuclear-energy-carbon-
constrained-world/)

~~~
pfdietz
Studies that purport to show that nuclear has a place due to inability of
renewables to fill those gaps are usually assuming renewables + short term
storage cannot fill those gaps. But renewables + short term storage + hydrogen
can, and probably more cheaply than a system with nuclear reactors.

~~~
AnthonyMouse
What's hydrogen supposed to add? It's just a type of storage, and probably not
even the cheapest one.

~~~
pfdietz
Hydrogen has low capital cost. The capital cost/energy of storing hydrogen
underground will be much less than the cost of storing that energy in a
battery. If you have a storage scenario where the energy is stored for very
long times, there will be few cycles of that system over its economic
lifespan, so minimizing capital cost (even if that means much lower round trip
efficiency) is very important.

One would still use more efficient short term storage (and over-installation
of renewables sources) for diurnal load leveling.

Hydrogen can also be turned back to electrical power (at lousy efficiency)
with cheap hardware. In particular, simple cycle gas turbine power plants with
efficiency of 40% cost maybe $400/kW. Compare this to $8-10K/kW for a new
nuclear power plant.

~~~
AnthonyMouse
> In particular, simple cycle gas turbine power plants with efficiency of 40%
> cost maybe $400/kW. Compare this to $8-10K/kW for a new nuclear power plant.

The problem being that it only operates ~2% of the time compared to ~100%, and
has a shorter operating lifetime in practice, and that isn't counting the cost
of storing the hydrogen nor the energy cost to produce it.

~~~
pfdietz
Yes, the power will be expensive during that 2%. But it will not contribute
all that much to the total cost of operating the grid. In particular, it would
be cheaper than forcing the consumers to pay for nuclear the other 98% of the
time, just so it would be available during that 2%.

~~~
AnthonyMouse
If it's dozens of times more expensive during that 2% because it has to
recover 100% of its cost in 2% of the time then it _does_ contribute quite a
bit to the total cost of operating the grid, whereas nuclear only has to make
up the difference in that time between the market price the rest of the time
and its overall average cost.

Storage also has the further disadvantage that you have to over-spec it. It
has to be built for the highest capacity you might need and the longest
duration, which you don't know ahead of time. If you build less than you need
you're in big trouble, but if you build more, you pay for it and get nothing.

~~~
pfdietz
Simple cycle gas turbines are 20 times cheaper than nuclear power plants of
equal power output. So, no, your argument doesn't hold up when the actual
numbers are examined.

~~~
AnthonyMouse
Being 20 times cheaper while producing 2% of the kWh because they're turned
off 98% of the time makes them 250% more expensive per kWh. And that's
comparing the the capital cost for the entire nuclear plant to only the
turbine, not including the capital required for the hydrogen storage, or the
equipment to produce the hydrogen, or the energy cost of the original
generation (with large conversion losses). Or, again, the deadweight losses
from the safety margin you need for surplus capacity that you might but
probably won't ever use, which could double the cost or more on top of
everything else. Whereas if you spec additional nuclear it means you're
generating that much more useful electricity 100% of the time.

Meanwhile that kind of storage will have more difficulty finding investors,
because if it turns out that some cheaper or better alternative comes along,
an investment in nuclear might have to average generating power below
levelized cost, but at least you recover most of the capital. Putting in $100
in capital only to have the net present value fall to $80 sucks, but not
nearly as much as putting in $100 in capital for a complete write off because
you were expecting to be selling to the grid 2% of the time when it turns out
to be 0% between demand based pricing and better than expected competing
storage technologies. Which means higher capital costs (meaning interest
rates) that reduce relative competitiveness even further.

~~~
pfdietz
> Being 20 times cheaper while producing 2% of the kWh because they're turned
> off 98% of the time makes them 250% more expensive per kWh.

Which ignores the cost of using nuclear during that other 98% (or whatever) of
the time, when it is very expensive compared to the alternatives.

Yes, the cost just during that 2% is high. But the total cost is lower than if
nuclear has to be forced down the consumer's throats 24/7.

------
rkachowski
There's a lot of references to "plate out" in the article and most of the
results I find on Google are paywalled by Elsevier - can some explain what the
term means or point me to a resource?

~~~
philipkglass
When fuel nuclei split apart in a nuclear reactor, their split fragments form
a variety of lighter elements. Some of these elements are so-called "noble"
metals -- metals that tend toward remaining chemically stable _as_ metals,
rather than as chemical compounds with other elements. Silver, ruthenium, and
palladium are some examples of noble metals. More typical metallic elements
like potassium and iron, by contrast, tend to be found on Earth as oxidized
chemical compounds rather than as metals.

In a molten salt reactor, _most_ fission products either stay dissolved in the
salt mix or are lost from the mix as stable gases. The noble metals are
different. Their tendency is to reform as solid metal. They tend to accumulate
as a metallic layer or plate of metal over other solid surfaces they come into
contact with. That's what is meant by plating out.

Here is a document that specifically addresses noble metal plate-out in molten
salt reactors:

[http://www.skyscrubber.com/Molten-Salt-
Reactor%20Technology%...](http://www.skyscrubber.com/Molten-Salt-
Reactor%20Technology%20Gaps.pdf)

See section III.C.

------
achalhp
From the article: >Problems with Molten Salt Reactors... >...but similar
problems may show up in long-lived power reactors.

Author assumes that MSR components should last as long as vessels and
secondary heat exchangers of solid-fuel reactors. The author should understand
that vessel and primary heat exchanger of a fluid-fuel reactor is anologus to
fuel rods. Solid fuel reactors just dispose primary heat exchangers or fuel
rods every few years. Example: Zircolloy tubes worth a MSR vessel + heat
exchanger is just disposed along with partially fissioned degraded solid fuel
every 4.5 years in a LWR. Zircolloy (Hafnium separated nuclear grade zirconium
+ additives) is more expensive than commercially available nickel based
alloys.

Graphite is a solid with a crystal structure. Crystal structure degradation
under radiation is permanent and there is nothing anyone can do to reverse it.
Solar panels degrade similarly. Nuclear industry handles solid-fuel rods which
are far more radioactive than MSR graphite and complains that it can't handle
MSR graphite. Just shows that either industry is incompetent or it is not
interested in efficient fluid-fuel reactors. Does nuclear industry aims >1000
GW of nuclear capacity? Does nuclear industry care to solve global energy
related issues? Efficiency really matters when we have >1000 GW of installed
nuclear capacity. If all energy is obtained from nuclear, (12000-16000 GW)
even seawater uranium get used up in 40-60 years with inefficient solid-fuel
reactors.

~~~
philipkglass
> _Efficiency really matters when we have >1000 GW of installed nuclear
> capacity. If all energy is obtained from nuclear, (12000-16000 GW) even
> seawater uranium get used up in 40-60 years with inefficient solid-fuel
> reactors._

That can't be right. About 200 tonnes of natural uranium is needed to produce
1 GWe per year in conventional reactors [1]. That's 3,200,000 tonnes per year
if you mean 16000 GW in the form of electricity, or closer to 1 million tonnes
per year if you're referring to primary (thermal) energy. Seawater contains
about 4.5 billion tonnes of uranium [2]. That's well over a thousand years'
worth of uranium, either way.

[1] [https://www.world-nuclear.org/information-library/nuclear-
fu...](https://www.world-nuclear.org/information-library/nuclear-fuel-
cycle/introduction/nuclear-fuel-cycle-overview.aspx)

[2]
[http://large.stanford.edu/courses/2012/ph241/ferguson2/](http://large.stanford.edu/courses/2012/ph241/ferguson2/)

~~~
achalhp
Firstly heat from inefficient low temperature solid-fuel reactors can't be
used directly for many applications. So consider electricity.
Cars/planes/kitchen-stoves cant use uranium or nuclear heat!!

All 4.5 billion tons can't be extratcted. More we extract, concentration
decreases and harder it gets. I keep asking this question: If seawater
extraction of metals is practical, why aren't we extracting other costly
metals now?
[https://twitter.com/AchalHP/status/1011661441412337665](https://twitter.com/AchalHP/status/1011661441412337665)

~~~
acidburnNSA
Don't confuse solid fuel with traditional light water reactors. The highest
temperature reactors are triso fueled helium cooled solid fuel reactors like
HTTR with outlet temperatures over 1000C. Also, fast breeder reactors with
solid fuel are just as sustainable as any fluid fuel breeder.

Molten salt is one of about a dozen advanced reactor techs that has huge
potential.

Hard part is economics. Hazardous coolant has been a pain to maintain cheaply
so far.

Also seawater uranium replenishes from erosion and plate tectonics so it will
effectively never decrease in concentration, even if we pull it out at world
scale.

[http://large.stanford.edu/publications/coal/references/docs/...](http://large.stanford.edu/publications/coal/references/docs/pad11983cohen.pdf)

~~~
achalhp
The successor of LWR/HWR should be a fluid-fuel reactor.

Once we setup a pebble/advanced fuel making factory, closing it will takes
decades (because people may lose jobs) and the new solid-fuel factory will
again pause nuclear innovation for another 100 years. The only way to
continuously improve nuclear reactors is to go fluid-fuel. No engineered fuel,
so no job loses. Reactor innovation is independent of fuel factory. Nuclear
fuel becomes a commodity instead of engineered speciality. Example: MSRE ran
U235 and U233 without any modification.

Secondly, solid fuel reactors throw away fuel along with heat exchange
surfaces (clad). Fuel also undergoes crystal structure degradation along with
other solid structures. Maybe there is enough fuel in the seawater, but there
may not be enough places suitable for geological repositories.

Solid-fuel reactors always need excess reactivity reserve. Always needs
control rods, and if someone (or a bad actor) pulls all the control rods,
reactor gets supercritical. Needs highly skilled people and needs security.

For emergency shutdown of solid-fuel reactor, poison is added to coolant, not
fuel. In an emergency, poison is added to the liquid-fuel, permanently
destroying the fuel. Emergency can be anything, from a natural disaster to
terrorist attack. Fluid-fuel reactors offer unbeatable safety features against
anything.

