1. Rob Morse Science Engineer- Nuclear Option 19 October 2009
Liquid Fueled Thorium Reactors without equations ∑x<+-=-*± An overview of liquid-fueled liquid-cooled thermal spectrum Thorium breeder reactors and why they matter.
I’m Robert Morse and this it LFTRs without equations. My degree is in nuclear engineering. I worked in an engineering design firm on nuclear power plants and on coal power plants. I’ve also designed Inertial Confinement laser systems, weapons class laser systems and monochromatic x-ray sources.
LFTRs without equations; the title is accurate because the motivation for the Thorium breeder is not technical. And if factors of a thousand are not enough to persuade you, then a few percent will remain insignificant. I think factors of a thousand are the correct scale for our discussion. In simplest terms there are only three things we want from a liquid cooled, liquid fuelled thorium breeder reactor; it must be safe, efficient and necessary.
It must be necessary. As much as we find them attractive, you don’t need one for a camping trip.
That said, we can’t run an industrial society by burning twigs and branches. Have no doubt, modern society is a good thing. Industrialization made a cleaner environment, not a dirtier one.
Rob Morse
Science Engineer- Nuclear Option
19 October 2009

2. Power makes a difference.
The hut and open fire are one of the deadliest environments known to man. There are over 70 countries with average per capita incomes below 10$ per day. Their children die early. They don’t want an Ipod. They want clean water and a way to treat their sewage. They want their children to stop dying.
We have similar problems here in the US where we have 40% unemployment in areas where we can’t pump or desalinate water.
Given that those deaths are real, what level of risk can we tolerate with a LFTR. The answer is pretty simple.
LFTR wo Equations. Thorium power conference, Oct 2009

3. LFTR wo Equations. Thorium power conference, Oct 2009
The Necessities
Self regulating when it is ON
Passively safe when it is OFF
Inherently safe in case of an ACCIDENT
The power source must be self regulating when it is ON, passively safe when it is off and inherently safe in case of an accident. We will discuss how to do that.
How much power do we need?
LFTR wo Equations. Thorium power conference, Oct 2009

4. LFTR wo Equations. Thorium power conference, Oct 2009
Fuel for a lifetime?
You consume a ball of coal meters in diameter…
…or a ball or thorium 37mm in diameter.
Here is the energy you will need for your lifetime. A ball of coal 10 meters in diameter, or a small ball of thorium that is 37mm in diameter. By the way, there is at least the same amount of thorium and uranium spread about that in 10 meter ball of coal.
LFTR wo Equations. Thorium power conference, Oct 2009

5. Moderation and nuclear probabilities
We’ve talked about thorium breeders, but I want to give you some perspective on thermal reactors first. Neutrons are ejected at very high speed during nuclear fission. We slow them down from a fraction of the speed of light to about the speed of sound. We slow them down by simple collision with a material called a moderator. This chart shows the change in cross section when we slow the neutrons. Their probability of fissioning or breeding increases by a factor of about That means the fuel is much more reactive when we use slow or “thermal” neutrons. For the layman that is counter intuitive.
LFTR wo Equations. Thorium power conference, Oct 2009

6. LFTR wo Equations. Thorium power conference, Oct 2009
Speed?
I think we can help you understand. (TRANSITION TO GOLF) Now you get the picture. We want to interact with the nucleus and we need to slow down the neutrons to promote that interaction. This is important.
All our commercial reactors are temperature stable over their operating range. The LFTR exhibits this to an unusual degree. We can select design options that preserve that temperature stability. We talk about a nuclear core. The LFTR core is not an array of fuel, but an array of moderator. Let’s see what happens when the fuel gets near a moderator, in this case two slabs of graphite.
LFTR wo Equations. Thorium power conference, Oct 2009

7. What does it mean if a reactor is extremely temperature stable?
A power plant with a built in thermostat!
inlet outlet
fuel-coolant
reactivity
Some of the uranium in the fuel decays spontaneously. Many of the neutrons are lost. As the fuel moves along the fluid circuit and get closer to the moderator, some of the uranium atoms are struck by slower neutrons that come from the moderator. This time the uranium fissions and releases more neutrons. The fuel heats up and expands. Expanding means that there is more space between each atom of uranium, there is less fuel per unit volume. The fuel heats up in the core, and at some temperature the nuclear reaction is not self sustaining and the power drops.
temperature
LFTR wo Equations. Thorium power conference, Oct 2009

8. Improved reactor design
reactivity
We can change the size of the fuel channel so that the whole core produces power as the fuel heats up.
One aspect of safety is strong temperature stability. If we stop taking heat out of the core, the salt remains hot as it enters the moderator and the reactor stops making power. Now that is a safe reactor.
Did you notice that there are no control rods? We do not have excess reactivity. We only have enough fuel in the salt to reach criticality when the salt is cool. Now that is a safe reactor.
Pressurized water reactors need to be cooled all the time even when the control rods are inserted. They need to remove the considerable decay heat that could melt the PWR fuel pins. The LFTR starts with a liquid fuel and the liquid fuel can be cleaned of fusion products that produce decay heat. In the LFTR we can drain the fuel away from the core and the fuel is safe. That is a safe reactor!
Notice that the fuel is not pressurized. We don’t need a heavy pressure vessel. We don’t need a massive containment building to withstand a high pressure steam explosion. That is a safe reactor…and a light one!
That is safety. Let us talk about efficiency.
temperature
LFTR wo Equations. Thorium power conference, Oct 2009

9. LFTR wo Equations. Thorium power conference, Oct 2009
The Reactor at “idle”
Closed Loop Cooling
LFTR wo Equations. Thorium power conference, Oct 2009

10. LFTR wo Equations. Thorium power conference, Oct 2009
An Efficient Design
Little or no radioactive waste
No bomb materials
Low cost per power delivered
A small physical size
A wide choice of building sites.
We want little or no radioactive waste. No bomb materials. Low cost per power delivered. A small physical size, and a wide choice of building sites.
LFTR wo Equations. Thorium power conference, Oct 2009

11. LFTR wo Equations. Thorium power conference, Oct 2009
Size matters!
Your nuclear waste is the size of a few grains of rice!
We don’t want any heavy elements in the waste stream. All of the heavy elements stay in the reactor and fission. Only the fission products enter the waste stream, and they decay in a few hundred years. The LFTR can do that, and that is efficiency.
LFTR wo Equations. Thorium power conference, Oct 2009

12. LFTR wo Equations. Thorium power conference, Oct 2009
Lets Make Power
These wonderfully peculiar reactors run hot at low pressure, and by low I mean less pressure than is inside a child’s soccer. (safety!)
They can use a gas cycle, like a jet engine, rather than a steam cycle like a coal or gas power plant. We do not have to design for 1000 pounds per square inch to achieve high efficiency or compact equipment.
Because of the high temperature operation, the thermodynamic part of the plant (the part that converts heat into mechanical power), the plant has high efficiency. High efficiency means a 50% improvement in power rejected to the environment per power delivered to the electric grid. The ratio of electrical power to thermal power should run near 50% at full load.
These plants can run at partial load and can follow the electrical load. (Conventional nuclear utility plants do not load follow.)
The heat transfer fluid (molten salt) is at low pressure.
We can use a gas cycle, like a jet engine, at high temperature.
This means they can have high efficiency, a 50% reduction in power rejected to the environment per power delivered to the electric grid.
These plants can run at partial load.
LFTR wo Equations. Thorium power conference, Oct 2009

13. LFTR wo Equations. Thorium power conference, Oct 2009
THE WORLD IS FLAWED
-The world is not sane. We could improve our standard of living AND improve the environment for our children at the same time. That alone should be enough.
-The LFTR is not perfect, but it is fantastically better than what we have. Please remember that the person who defines the rules selects the winners. That is where we must argue. We must clearly show that the design we propose is better than existing power sources. That alone should be enough.
-I want to industrialize the world, even if the countries do not have oil. That alone should be enough.
-We are not alone in the world. I want to remove the need for uranium enrichment and sending billions of dollars a year to foreign countries. That alone should be enough reason to pursue the Thorium breeder reactor.
After this conference, I am hopeful. The question is not IF someone will produce the thorium reactor. The question is WHEN… and by WHOM. I would like them to be some of the people in this room.
Any questions?
LFTR wo Equations. Thorium power conference, Oct 2009