All of the uranium in the reactor was separated from the intensely radioactive fission products.
I shall never forget my wonderment, as I stood next to the unshielded steel cans containing
the uranium- that only a few days earlier
had been mixed with millions of curies of radioactivity.
We were particularly proud of this, because that tiny chemical plant
was large enough to decontaminate the core of a 1 gigawatt molten-salt breeder.
You know, in one respect a machine is a machine.
But I guess anybody who involved in designs of things get sort of emotionally wedded
to one thing over another.
And I think the molten-salt breeder was probably the one thing that he really had
a feeling in his heart for.
There's this hot idea about using molten salts.
High-temperature is probably easier than high-pressure.
That was one of the best decisions I made, I think, despite the fact
the project was eventually terminated.
But I still think that, well, eventually people will come back to this reactor.
So I was born in 1974, which unfortunately, was the same year the Molten-Salt Reactor
was shut down. The whole program ended.
So I can kind of mark the beginning of my life
as the beginning of the end for the Molten Salt Reactor.
We're far behind schedule.
And we want to power the world with thorium.
And want to eliminate so many of the political and social problems that have
come about because of our dependence on other energy sources.
Really big star exploded.
A supernova.
And this seded the universe with everything heavier than iron.
Now, two of the things that were created- thorium and uranium- kept some of that energy
from the supernova explosion stored in their very nuclear structure.
And some of this thorium and uranium was incorporated into our planet.
Only Thorium-MSR is going to allow us to produce nuclear power without plutonium.
There are no other options, to making nuclear power
and not making plutonium other than this approach.
So this is the classic design for the Molten-Salt Reactor that came out
of the Oak Ridge effort in the 1970s.
It's what we call a single fluid reactor.
It is a complex chemical undertaking in order to turn one of these reactors
into a thorium breeder reactor.
There had been Oak Ridge studies done on what's called the 2-fluid reactor,
and the 2-fluid reactor is fundamentally different
in that it separates the fuel, the uranium-233 fuel,
in the FLiBe salt from a blanket FLiBe salt carrying thorium-tetrafluoride.
The challenge of this 2-fluid reactor design though, is the internal geometry of the reactor.
The advantage though, of keeping them separate, is-
The simplification that can be realized in the reprocessing step.
With the 2-fluid reactor it is a rather straightforward thing
to move the fuel that has been bred in the blanket
out of the blanket, and get it back into the core,
which is where you want it- You want it in the core salt.
Thorium does not have a volatile hexafluoride.
You can fluorinate it, and fluorinate it and fluorinate it all you want-
and it will not change chemical state.
It will stay thorium-tetrafluoride.
Uranium, on the other hand, does have a volatile hexafluoride.
And this is why many of us feel that the uranium-thorium fuel cycle
is a perfect fit with Molten Salt Reactor.
This same trick doesn't work by the way in uranium-plutonium fuels.
They both have volatile hexafluorides, and so you can't undergo a separation
using the simple technique of fluoride volatility.
One of the things we want to do is to couple to a gas turbine.
That addresses tritium migration, but it also gives us the potential to radically reduce
the form factor all the way down to supercritical-CO2.
And in fact, one of the original ideas was to use a Molten-Salt Reactor to drive open-cycle
air gas turbines and power a jet!
So this is the crazy idea that kicked off the Molten-Salt Reactor.
So there's just a little bit of precedent.
This 2-fluid reactor design was also designed to be modular.
To bring new nuclear power plants online quickly- they were into Small Modular Reactors before
Small Modular Reactors were cool.
Liquid fluoride reactors with their low pressure operation
are particularly suitable to modular construction.
Because one of the hardest things to get around is the large heavy pressure vessel that's
required when use pressurized water reactors.
Safety is one of the most important reasons to consider, very seriously, Molten-Salt Reactors,
and this is because of the clever implementation that was demonstrated
in the Molten Salt Reactor Experiment of the freeze plug and the drain tank.
This is something that perhaps was not getting enough attention in the early 1970s.
Now we know, that if we want to have the public accept nuclear reactor technology, it has
got to be very safe- and it's got to be something that is easily explained to people.
Now I've explained the safety basis of the Molten Salt Reactor to people many times,
and I haven't had anyone who is unable to get it.
Frozen plug?
That's it. That's it!
Flattened pipe.
With electrical heat- resistance heat on that one.
So you invented the frozen plug then.
A small port in the bottom of the reactor, plugged by a frozen plug of salt.
If all power was lost, that plug melted, the fuel drained into this train tank, and the
difference between the drain tank and the reactor vessel was the reactor vessel was
not meant to lose any thermal energy.
The only place you wanted to lose thermal energy was to give it up
in the primary heat exchanger.
The drain tank on the other hand is designed to maximize
the rejection of thermal energy to the environment.
Three paths.
The path we take now which is burning this very, very rare amount of Uranium-235.
Or the path that has been investigated by a lot of advanced nuclear programs,
the idea of burning in a fast reactor Uranium-238.
Or this new-old idea, which is using thorium in a thermal spectrum reactor.
We could imagine fueling a Molten Salt Reactor with Low-Enriched Uranium.
If we do that, the uranium mining and enrichment necessary will be comparable to what we do
today in Light Water Reactors.
That path was weaponized and it continues to be a concern.
Option 2, we could imagine fast-spectrum Molten-Salt Reactors.
We would not need any more uranium mining or enrichment.
But we're going to have a high inventory.
Fuel looks small to a fast neutron.
And there are chemical separation issues with fast-spectrum Molten-Salt Reactors that are
going to be challenging- It's harder to get plutonium and uranium away from one another
in fluoride than it is to get thorium and uranium away from one another.
And finally, Option 3, which is obviously the option I favor which is the thorium fuelled,
thermal-spectrum Molten Salt Reactor.
No uranium mining or enrichment are going to be necessary once we're in steady state.
And this option will have the lowest of all the fissile inventories.
And that fissile inventory won't be plutonium, it will be Uranium-233.
That third path was not weaponized because the unavoidable contamination of Uranium-232,
which was realized by Glenn Seaborg in 1944.
What we would propose is to use many of the materials that are otherwise going to go to
waste- to a fully thorium powered future.
In this scenario we put both our plutonium, our HEU, our U-233- all to productive use
along with our thorium stockpiles.
So I would make the case that if you have to choose your physical currency from one
of these three options- The safest and best bet and most efficient is to use Uranium-233
and to choose the thorium option.
Our fundamental motivation is that we share the dream that was put forward by Dr. Alvin
Weinberg long ago, of a world set free by the use of thorium as an essentially unlimited
energy source, and I know it was said earlier that thorium's not a miracle.
To me it is a miracle.
It's a miracle that there's a material on Earth that has such remarkable energy density,
that even worthless dirt is transformed into an energy resource greater than the richest
crude oil or anthracite coal or any other resource you can imagine.
To me that is- that is truly a miracle.
Every time mankind been able to access a new source of energy it has led to profound societal
implications.
You know, the Industrial Revolution and the ability to use chemical fuels was what finally
did in slavery.
Human beings had slaves for thousands and thousands of years.
And when we learned how to make carbon our slave instead of other human beings we started
to learn how to be able to be civilized people.
I really believe that if we don't have access to affordable and clean energy, we will revert.
We will go back to the way humans have been for thousands and thousands of years, which
is where the powerful and the rich oppress the masses who live terrible lives trying
to provide things for just a few people.
We live much better lives today because we have learned how to use carbon.
Okay, what about thorium?
Thorium has a million times the energy density of a carbon-hydrogen bond.
What could that mean for human civilization?
Going out thousands- tens of thousands of years into the future?
Because we're not going to run out of this stuff.
Once we've learned how to use it at this kind of efficiency we will never run out.
It is simply to common.
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