Good afternoon and welcome to our
nuclear engineering colloquium series. The president and chief
technologist of Flibe Energy, Kirk Sorensen, he's also
affectionately called Mr. Thorium. If you had told me
when I was an undergrad that I was going to
be in nuclear engineering, I'd have laughed in your face. I'd
have said, "What are you talking about?" You know, I mean, I not only
had no interest in nuclear engineering, I actually had negative
interest in nuclear engineering. I wanted to
go build rockets and wanted to
work at NASA. And you know, sometimes be careful
what you wish for. You might actually get it. I did. And there was a lot of things
I really loved about working at NASA. But I think what I was hoping for
was a little closer to what SpaceX became, rather than what NASA was back then. Originally got into space stuff because
I was really fascinated by exploring space. And while I was there at NASA, I learned about this technology
from a friend of mine, who had actually gone to
library and found a book on it. Something about molten salt reactors.
And I'd never heard of such thing. I'd never heard of Thorium. I'd
never heard of what this could mean. And I got very, very excited about it. Our company is called Flibe Energy,
and we're working on a molten salt reactor. It's based on the Thorium fuel cycle.
It's got two fluids in it, a fuel salt, and it's also
got a blanket salt that surrounds the fuel salt
and absorbs neutrons. You can achieve much higher nuclear
efficiency, capturing all those neutrons. And this is based on using liquid
fuel, which is pretty different than solid fuel. But we believe this liquid
fuel is really going to be the key to realizing the energy
possibilities of thorium and making it possible to have an endless supply
of nuclear energy. This whole idea really starts
with a Thorium fuel cycle. If we start at the moment of fission,
this is when the nucleus splits apart. And we need at least one
of the neutrons from fission to make its way
to an atom of thorium and be absorbed
in that atom. And then, that atom is going to decay
to another element, protactinium. And that's ultimately going to decay
to fissile uranium, uranium-233. And then that U-233
could be struck by a neutron, have another fission,
and at least one of those neutrons is going to make its way
into another atom of thorium. And so you can keep the
process going, theoretically, indefinitely, which is really kind of magic.
The first time I learned about this, My mind was completely blown,
that this was even possible in real physics
in our real world. So let's talk a little bit about
uranium. We know it's got 92 protons, and in this case, it's got 141 neutrons. And altogether, that's a mass of 233. So that makes this material uranium-233. Now, if uranium's got 141 or 143 neutrons, it has a special property.
It's fissile. That means it has the ability
to undergo nuclear fission. The uranium atom is also
surrounded by a bunch of electrons. Uranium has four outer
electrons that it can share with other things,
in this case, fluorine. And when fluorine is
bonded to uranium, that's why we call it
uranium tetrafluoride. The tetra means four. This kind of bonding is actually
really common with fluorine. This is how fluorine
bonds forming ions. You may have brushed your teeth with a similar
compound of fluoride called sodium fluoride.
So when a uranium atom is struck by a slow neutron,
it can set up a process of fission here,
and that fission erupts, and it releases a lot of energy.
It releases two fission products but it also releases
several neutrons. And these neutrons,
they've got so much energy. They're moving so
fast that it's very unlikely they're going to cause
another fission reaction. So we've got to
slow them down. This process works
really well in carbon, in the form of graphite.
Neutron rattles around in the graphite, and it slows
down, and it loses energy. And then it's all
set up to trigger another fission reaction.
We've got to make sure one of these neutrons finds
another atom of uranium-233. But let's follow the other neutron.
Where is it going to go? Well, we want it to
find an atom of thorium. And if it finds its
atom of thorium, it's going to turn thorium
into a new nuclear fuel. So natural thorium
has got 90 protons, and that gives an atomic it's got 142 neutrons, and that
gives an atomic mass of 232, which is why we
call it thorium-232. And all thorium is
thorium-232, essentially. When it absorbs this neutron,
on the other hand, the neutron count
goes up one, it's not thorium-232 anymore,
it's thorium-233. And it's not going to
stay that way very long. It's actually going to
undergo a decay process in about 30 minutes,
where one of these neutrons is going to turn
into a proton, and it's going to emit an electron.
This process is called beta decay. That's going to change the
number of protons to 91. It's going to change the
number of neutrons down to 142, and we are now going
to have a new element, protactinium-233.
Now, protactinium-233 is now chemically distinct from
the thorium it was in before. It has a possibility to be extracted. We need this protactinium
to decay to uranium, but we don't want it
to absorb another neutron in the time it takes
to do that, and it's going to take, on average,
about a month for that to happen. In the meantime, we want to keep
protactinium away from neutron. We don't want
it to get any more neutrons. We need to take it out,
and we propose using this electrolytic cell,
which is basically a battery, and we would run a
pretty modest voltage a little less than
one and a half volts, between the anode and the cathode, and this would cause
thorium to evolve off this sacrificial anode,
while at the same time protactinium is being
driven into a pool of metallic bismuths,
and load this protactinium into a fuel salt carrier,
and give it time, several months, for it to
decay into fissile uranium, and by the time it does this,
then it's ready to be introduced back
into the reactor after it's undergone this decay process,
and we can load it back into the fuel, refuel the reactor this way, so we can keep this process
going on and on and on if we design the reactor right
and use it properly, but really the key to
making all this work is that uranium-233.
It's very valuable, it's very important,
and we're not going to be able to start the
thorium reactor without it, so this is really the starting
point to the whole process here. But if we can do this,
we can realize endless amounts of
energy for the world, because essentially we have an endless
amount of energy from thorium. It's a possibility to go
from where we are today, which is using about
one half of one percent ( 0.5 % ) of the energy in the uranium
in the ore that we mined, to almost 100% of the energy being
utilized from the thorium in these molten salt reactors.
I mean, that's practically a 200 : 1 advantage,
and by so doing that, we can almost completely eliminate
the production of new nuclear waste. As they say on TV:
"But wait, there's more!" Not only can we do that,
totally exciting all by itself, but we can potentially take
these molten salt technologies we can apply them against
old spent nuclear fuel. Y'all have taken fuel cycle class, right? Y'all know what happens to
nuclear fuel when you make it? Take uranium dioxide,
what do you do with it? You gotta make it a fluoride.
Very good, You gotta make it into a fluoride, So first thing you gotta do is you
gotta change it into something else. Well, that's what these reactors run on,
they run on uranium fluoride, so the point I try to
make to people is talking about using uranium fluorides,
it's not weird, it's not strange,
it's actually something we do with every speck
of uranium we use today. It's all been a fluoride, first it was
a tetrafluoride, then it was a hexafluoride, and then went through
an enrichment plant, and then we had to make
it back into an oxide again, or a metal, or something else.
So what we're talking about, and we're not the only ones, we could take uranium
dioxide, spent fuel, and we could fluorinate it again,
just like we did in the beginning, and we could make
a salt mixture, we could make a molten
salt mixture, and then once we've made a salt
mixture, we could potentially go and remove certain
things we want to take out, I mean we want to
take out the uranium, maybe we want to go and
recycle that, because uranium is most of the spent fuel,
but it's almost none of the radioactivity.
So we could take out 95% of the mass of the
spent fuel, just by recycling the uranium, just by
recycling it back into our existing economy.
But there's other things we can recycle too, we can
recycle noble gases like xenon. when I was at NASA, we were
very interested in xenon, because that's a fuel
that we use for spacecraft. In fact, a spacecraft was
launched just the other day, does anybody know what
spacecraft got launched? Psyche!
Where's Psyche going? It's going to Psyche,
that's right, Very good!
Where's Psyche at? It's in the asteroid belt. What ions are they throwing out
the back of that ion engine? Xenon! That's right!
We used to joke at NASA, xenon was the only thing
worth launching into space, because it was the
only thing that cost as much as it cost to launch it.
Everything else was cheap. but xenon was so
darn expensive, it was like actually worth
launching into space. because it was that expensive. Do you know that Xenon is the
most common fission product? Did you know Xenon
stabilizes in about a month? There's a shocking amount of xenon
sitting around in spent nuclar fuel. That's like the number one thing
fission makes, is xenon. The fission reaction is
making lots of things, and I was just amazed
how many of these beome stable isotopes and
become potentially useful. But the problem right now is all of these fission products
are mixed together in a semi worthless configuration. Let me give you an analogy. How many of you got a
pantry in wherever you live? Food, cereal, rice, sugar, beans.
... Kale in the pantry? That goes in the fridge! I'm gonna take all this food in the
pantry and I'm gonna dump it in a big pile on my kitchen, okay,
on the floor of the kitchen. I'm gonna take my broom
and I'm gonna mix it! In a big pile, all right?
Then you look at it, what do you got?
Have mass changed? No! You have the same amount
of stuff that you had before. Has temperature changed?
What's the problem though? Is that useful material to you? If you got your beans and
your cereal and your rice and your sugar all mixed together,
it's totally worthless, right? All you can do at that point is you can scoop it up and throw
it in the trash and throw it away. What was valuable about your pantry
was that everything was separated. Your rice was in your rice bin and
your cereal was in your cereal bin. That's how spent nuclear fuel
("nuclear waste") is right now. Everything's mixed together.
The neodymium and the samarium and the lanthanum
and the cerium and the strontium and the cesium,
it's all in a big pile. And that's what kind of makes
it worthless to us right now, it's the fact that
it's all mixed together. Let me tell you something
really cool though, about molten salts. If you make spent
nuclear fuel into a salt, we could then
use electrochemistry to tease out the
various species of salts and extract these fission
products onto electrodes. And now suddenly it's like
we've unscrambled the egg. We figured out how to get
individual species of materials. All of a sudden they're
not worthless any more. Now they're useful. I found almost every single
thing that comes out of fission, if you can get it by itself,
is a useful thing. If you can get the strontium,
if you can get the cesium, and you can get the lanthanum, and you can get the barium,
and you can get the xenon, you can get them
all by themselves, Every single one
of them has value. Where they don't have value
is when they're all mixed together like they are right now, just like
your pantry wouldn't have any value if everything was
mixed into a big pile. We think that that is
going to be a very exciting thing to do, not only
with spent nuclear fuel, but also with the fuels
for these reactors because we want to be
able to reuse and recycle all kinds of material.
And fission is an amazing way to make new things,
to make things that we can utilize in society
and in some cases have incredibly special values.
There's even a class of materials that are used in medicines
because they're radioactive. I was talking to a
guy the other day with a company called Zeno Power. They're getting ready to build
a battery based on strontium-90. And he was saying,
Oh, you know, if you're going to make
strontium, can we use it? And I said, heck yeah, that's great.
Now we got somebody who wants it. Okay, wonderful. I think this is going to be a very
exciting step forward in nuclear, we're going to see in
the not too distant future. And this is why I'm really hesitant
to say nuclear waste is waste. When people talk about taking
nuclear waste and throwing it away, I almost want to go:
Whoa, don't do that too fast! Because I really think we're
on the cusp of figuring out how to make that stuff very,
very valueable and very useful. One of the keys to that
though is we've got to get it into a molten salt.
Once we get it in a molten salt, we can start to do
electrochemistry on it. But right now, as a ceramic,
it's just about impossible to do those kinds of
separations on it because just the nature of
what a ceramic fuel is like. When I've been up talking to some of the leadership at NNSA before,
they're kind of responsible for the fuel kind of getting
to the plant and then kind of for diversion
and nonproliferation. When it gets out of the plant,
they would love to have a fuel that attaches to something
that makes it worthless, that can never be separated. Yeah they would. That is the opposite
of what you want to do. If you looked at things like TRISO, you talked about recycling our
current fuel, but what about TRISO? They like TRISO because they
think it's really hard to recycle. They think it is more proliferation
resistant than our current fuel. I was just wondering if
you've ever thought about it? Oh, I've thought about it.
I'm not a Triso fan. The United States has got a lot
of separated weapons material. We have 30 tons of surplus
plutonium. We have more than that in the existing arsenal.
We have a lot of HEU. The notion that the
United States is going to take spent nuclear fuel
and somehow divert it? I mean, it beggars imagination. We're not. We literally have a
pile of weapons grade plutonium that if we want to go make bombs,
we go make bombs out of it. We're clearly not
making bombs out of it. So, I will tell people, in terms of the United States,
there is no such thing as diversion or proliferation.
Dude, we already have bombs. Nothing will be more
useful for a weapon than the pile of weapons
grade plutonium we have sitting around
surplus right now. So do we need to do TRISO, for us?
No, we don't. What kind of regulation or regulatory
hurdles do you have to overcome, I guess mainly containment wise? Since you're dealing with
removal of fission products, mainly gaseous
fission products? Well, you know,
it's really interesting. A lot of reactors today already do
have gaseous fission product handling. BWRs... I had to study this
when I took Dr. Miller's class. BWRs have a pretty serious gaseous
fission product handling system. The difference is, our gaseous fission
product handling system is designed to handle the entire
gaseous product inventory, constantly. But in principle, it's not that different
than what we're already doing today. I was really surprised actually, in several of the classes I took at UT
to learn that a lot of our reactors already have chemistry control, they have to deal with leakers in fuel, they have to deal with fission
products going to where they're not supposed to.
So, you know, there is a fair amount of
some of these things already taking place in commercial industry. More than you might suspect.
Our pins are not perfect, they're getting better all the time,
but they're not perfect. And we do have fuel
failure sometimes, and we do have to handle
some of these things. As far as the NRC goes, there is
definitely going to be a re-education going on, but this
is common for all kinds of advanced reactors
are facing the challenge of trying to spool up more
understanding in the NRC. For the longest time in
the NRC, you could count on a bunch of guys who had
been in the Navy Nuclear Program going to the NRC,
who understood PWRs and BWRs,
and it wasn't that hard. Now though, we're asking the NRC to
do though is to understand reactors where there are not
existing commercial examples, and there's no Navy
heritage to draw on. And so I think, Wes, you've got
a Navy background, right? You know, I mean, this
is going to be the thing. This is going to be a challenge. A step in the right direction,
but you're absolutely right. It's going to be something
we're going to have to work on, and it's going to take time. One of the things I really am
hoping though is there's been movement in Congress
to tell the NRC that if you're working with startups or
advanced reactors or new companies that you're not going
to charge their time against that kind of learning curve,
which I think would be really great. It makes a lot of sense. Our current regulatory
structure is built around people with
big gigawatt plants that make lots of money and
need fairly light regulation. We're talking about startups
that need new understanding, and it's real hard to pay for
that at $400 an hour. I think there's a question back there. One of the pros of
ceramic fuels and solid fuels is that you contain a
lot of the fission products and damage levels a lot better. What are your plans to mitigate
corrosion and damage levels in your core structural materials? There's certainly partly true
to what you're saying, but I would actually make the case that we contain
fission products better in the fluoride form.
Fluorides are more tightly bonded to most metals
than oxides are. They're more electronegative,
and there are certainly certain species,
cesium in particular. Cesium is volatile in oxide media, but it's absolutely rock
solid stable in fluoride media. Cesium fluoride might be
the most stable salt there is. So, you know, these
fluoride compounds really lock down fission products
very well in non-volatile forms. There are a few
exceptions, obviously, like fission product gases,
but that's no different in solid fuel. Solid fuel undergoes structural damage
just due to the fact that covalent bond can't stand a multi-EV
neutron, it breaks apart. In the ionic bonding
that you find in a molten salt,
bond strengths are continuously renewed.
Bust apart the bond, it just comes right back together
again that is nature of an ionic bond. I think we have an
excellent argument for the chemical containment
of the fuel itself. The chemical containment
of many species of fission products will be
much better in fluoride media than they will be in
oxide media and far less susceptible to
thermal excursion. We want to get it hot and
actually have a meltdown and have a fission
product release. Fluorides just don't get that hot
before they radiate that heat away. It's a great material for
these sorts of problems. It doesn't contain everything, but neither does anything else.
But it does have a bond that is impervious
to radiation damage and constantly renewing.
So, that's great. I mean, like I said, I wish I
had thought all this stuff up. What do you think
are the anticipated doses for structural materials
in the system that you're looking at from
neutron damage? Well, that's a good question. I don't have any numbers
I can throw off top of my head, but one of the basic
principles of this notion of having a fuel and
a blanket is that we use the blanket essentially
as an internal radiation shield. It's very good at absorbing neutrons and
pretty darn good against gammas too. And by so doing and
configuring the reactor properly, we think we can
keep the dose on the reactor vessel a lot lower than
what you have in today's PWRs. In a PWR, I mean, you have
some water between you and the outside of the vessel, but a lot of neutrons and a
lot of gammas make it to that structural material
and they degrade it. No metal really does well in neutrons. I mean, they just don't exist. Some do better than others. This is actually a huge
problem for fusion. Fusion's got 14 MEV neutrons
hitting the first wall and whatever that is,
it's going to get the you know what kicked out of it. Fission lets you put stuff between
your fuel and that structural material. Now, the one place
where that process gets a little thinner
though is in the first wall of our primary heat
exchanger and that's kind of akin to like the
clad of a typical reactor. That's where you're
going to have a pretty hefty dose of gammas,
but because our fuel is actually outside of the
neutronically active region, then you're just dealing basically with delayed neutrons at
that point as far as the neutron flux. Whereas in clad, you're dealing with
the full blast of fast neutrons going out and thermal neutrons coming in. So, it's a much harder problem. Now, of course, we replace clad
every couple of years in a reactor. You put an assembly in,
it's clad, and we take it out because we don't know of a material that's going to survive that kind of
neutronic flux forever and ever. We certainly haven't come up with it yet, but what I'm saying
is there are possibilities in the molten salt
reactor design that let you really, really dial
down that problem particularly for the vessel, but even for the
primary heat exchanger, which is where you
have the thinnest walls. You know, radioisotopes for medical uses. Big thing is actinium-225. Is there a relationship between actinium-225
and uranium-233 and thorium? Here's your $20 bill, Wes. Thanks for asking me that question. No, thank you. That's an excellent question, Dr. Hines. Yes, there is a relationship between
actinium-225 and uranium-233. Uranium-233 will decay
to thorium-229 and then that in turn
will decay to actinium-225. In fact, that's one of the only ways
you can make actinium-225. So by using the thorium fuel cycle
and the uranium-233 fuel reactor, we can actually
produce a category of targeted alpha
therapy isotopes like actinium-225,
bismuth-213 that would be suitable for fighting cancers. And it's really unique that way because while there are a few other
potential candidates for this, they're just not near
as good as this one. And it's really- So many of us have probably
heard about how they milk, some materials at Oak Ridge
and make actinium-225, right? That's one of the
only sources that we have. So where does that come from? Well it came from the
operation of thorium reactors. The source that they milk
for that actinium-225 is about half a gram
of thorium-229. And I met the guy who got that
half a gram (of thorium-229) and he was pretty ticked because he had been
trying to save 30 grams of thorium-229
that was in a vessel and most of the rest
was thrown away. He literally rinsed what
was left in the vessel and that's where he got the half gram
that ended up on that column out there. So it's kind of a horrible story. But yeah, they're saving lives
with that little tiny rinse he did. Think what they could have been
doing if they'd saved the 30 grams. So going back to the
electrochemical separation of the different isotopes to be
dissolved inside of the molten salt, what exactly is the
mechanism that you're using to discriminate against what
specific atom you're collecting? Voltage. It is the only thing you can do. Voltage. Voltage determines
what comes out of it? Yeah. There's an electromotive series
and you just change the voltage. You kind of go one at a time. We're going to get this one out.
I'm going to turn the voltage. We're going to get this one out. I'm going to turn the
voltage and get this one out. It's interesting how close the
voltages are to one another though. They're not very
far off from one another. A friend of mine said,
By 2 volts, you've done everything. It is a lot shorter list
than you're going to think. But yeah, voltage is
your discriminator. That's how you go
and pull things out. How are you going to account for anything
somebody could just come in and take? I'm sure uranium-233 or a tank full of
soon-to-be uranium-233 is rather... uh. It's hot. Well, it probably looks good to
somebody that wants terrorism. It's hot on several levels. Number one, it's hot. It's like 650 degrees. Number two, it's hot. It's throwing out
really hard gammas. And number three, it's inside
a furnace that's also at 600 degrees. So it's not like a room you're
going to walk in and swipe it. The short answer is, it's really
easy to notice when it gets stolen. We were working on a safeguards
approach with Oak Ridge National Lab. Unfortunately, it was
truncated by COVID, but we're making some really
good progress on basically getting everything into sufficiently
small enough packages that, number one, it's not
a significant quantity. And number two, you'll
detect diversion very quickly. And diversion is generally going to be lethal in this case in
very short order because of the highly emissive
nature of some of these decays. Didn't have time to
go into some specifics, but there is a nice
long answer to that. And we have a report
about it and I'd be happy to pass that along
to you if you're interested. I was wondering if there are Instrumentation
and Control (I&C) challenges with your design? Are you doing electricity generation,
or what's the business model? Second question was: Are there I&C
(Instrumentation and Control) challenges? And the answer is:
yes, there are. And unfortunately,
because I'm not nearly as good on I&C as maybe
some other things I can only guess at
some of the challenges, But you're dealing
with a system, that is both radiologically
and temperature hot. And that means a lot of potential instrumentation just is not going
to be used in something like this. As we've gone back
and studied how Oak Ridge did this in the past, it's been
a little bit of semi horror. Going, oh, wow! We ran a one slot reactor
without knowing this or that! So we would definitely today want
much better instrumentation and much better insight
into what's going on. There are also some
very interesting alternative approaches that are
being looked at. I know a guy and his
expertise is sound monitoring. And he goes:
I can put acoustic sensors on this thing. I can tell you everything
that is going on in there. I said, no way. He goes: Yeah.
It's like sonar? He goes:
Yeah, pretty much. As far as your question
about the business model, as Dr. Hines was telling, there's a lot of different things
you can do in molten salt reactors. You can work on power generation. You can work on waste remediation. You can work on isotope production. You can work on process heat generation. There are a plethora of possible
valuable products that really differentiate. I like to think of them as a
cornucopia of good things. And that takes them way
beyond what we've got today where really we
just make electricity. You know, we're going to
go a lot further than that. Okay. Let's thank Mr. Thorium.
