A ternary mixture is a three-part mixture of some substance. Ternary mixtures are especially important in fluoride reactors because there are some three-part mixtures that have very attractive properties. A three-part mixture of lithium, beryllium, and uranium fluorides can be used as a fuel in a fluoride reactor.
The lithium and beryllium fluorides are mixed together to make an attractive “solvent” for the uranium fluoride…much like the water in salt water. Uranium tetrafluoride, all by itself, has a melting point of 1035 degrees Celsius. Lithium fluoride all by itself has a melting temperature of 848 degrees Celsius. But when you mix LiF, BeF2, and UF4 together in the right proportions you can get that melting temperature down as low as 350-400 degrees Celsius.
A lot of work was done at Oak Ridge and other laboratories in the 1950s and the 1960s to understand these ternary mixtures and their properties. One of the most important things to understand was how melting temperature changed with the composition of the mixture. So they developed experiments and they plotted their results on ternary mixture diagrams, like this:
Now I’ll confess–I’ve been looking at these diagrams for years and really haven’t been able to understand them. All I could see was a triangle where each vertex (point) is labeled with the name of one of the components of the mixture. There’s a bunch of contour lines in the middle that I knew represented lines of constant melting temperature, but I could no more use the diagram than fly to the Moon.
So, I did what any good curious engineer does when he needs to learn something quick–Google search! And sure enough, it wasn’t long before I found a couple of nice sites that taught me how to read a ternary mixture diagram:
These sites were helpful and useful, but after plotting out a ternary diagram on the printer and breaking out the pencil and ruler and trying to figure out which way the lines should go, I was a bit frazzled. So I thought there should be an easier way, since I was pretty sure most folks wouldn’t be interested enough in ternary diagrams to go to all this trouble.
So I combined my interest in ternary diagrams with my enjoyment of Java programming to build an interactive tool that would allow folks to mess around with different ternary mixtures and see how their properties change as they chose different combinations.
There’s still a number of features that I want to add, but for now, you can run this simulation and move your mouse cursor around inside the triangle, and the simulation will figure out what composition of the three materials corresponds to the location of your mouse. The best part is that it will figure this out for you automatically without having to use pencil and ruler like I did!
Ternary Mixture Simulation (Java WebStart)
If you like it, let me know. If you hate it, be gentle. If you want some new feature, leave a comment and I’ll see what I can do.
Every morning I read the online editions of the two main papers in Salt Lake City, because I was born and raised in Utah and want to keep up with what’s going on in my boyhood home. This morning there was a very interesting article:
Deseret News: Utah nuclear plant construction a step closer
I had no idea anyone was really seriously thinking about putting a nuclear power plant in Utah. For many years now, the state has fought the Skull Valley Band of Goshute Native Americans from building a dry-cask storage site on their tribal lands. Personally, I can’t understand why they would be so terrified of dry-cask-stored nuclear waste and yet be fine with the fact that at Dugway Proving Grounds the US has been storing chemical weapons for many years. But that’s another story.
No, my real question about a nuclear power plant in Utah is the question any good Westerner asks about any development: where’s the water going to come from? Water is everything in the West. Without water, there’s no crops, no development, no people. We are blessed with giant natural water storage towers called mountains, and each winter we would watch the snowpack carefully, knowing that that’s all the water we would be getting for the next year.
A typical light-water reactor, like any large thermal power plant, uses a lot of water for cooling. Using cooling water is essential because of the physics of the power conversion system. Light-water reactors use the Rankine cycle with water/steam as the working fluid. Water is boiled under high pressure until it’s all steam, then expanded through a steam turbine to make work (and electricity), then condensed at low pressure back to a liquid, where it can then be pumped back up to high pressure for a tiny fraction of the work generated during expansion.
The Rankine cycle is quite elegant, taking advantage of the thermodynamic efficiency of isothermal heat addition and rejection. In normal speak, it means that the best way to make work (and electricity) is to somehow add thermal energy without making something hotter, and to take thermal energy away without making it colder. That may seem impossible, but nature has given us one simple process to do it–the changing of phases, from liquid to gas, and from gas to liquid.
When you are bringing water to a boil, stick a thermometer in the pot. You’ll see the temperature creep up closer and closer to 100 degrees Celsius until boiling starts. Once the water starts to boil, the temperature won’t change anymore. It will stay at 100 degrees C until the water has all boiled away to steam. That’s isothermal heat transfer. Your stove is moving thermal energy into the water, but the water isn’t getting hotter (isothermal) because it is undergoing a phase change (boiling). It’s really very elegant.
The concern for Utah comes from the reverse process: condensation. After the water has been turned to steam and expanded through the turbine, it has to be condensed (turned from steam to water) by cooling it. And all of that thermal energy in the steam has to go somewhere. Here in the Tennessee Valley of Alabama, we have a large river where we can conveniently dump the heat from the three reactors at Browns Ferry. But I’ve seen the Jordan River, and the Bear, and the Weber and Ogden and Logan Rivers. They’re barely ditches compared to the mighty Tennessee. Even the Colorado, for all its fame, isn’t much to compare to the Tennessee.
And very few Utahns live near the Colorado.
What about the Great Salt Lake? I grew up four miles away from that body of water. I’ve never been there. One of the many problems of the Great Salt Lake is that it is so shallow and slopes so gradually that the water intake pipes and return pipes would have to be many miles long. Also the lake is so saline that the corrosion could be horrible. The land around most of the lake is very marshy. (I did try to go to the lake one day, but after half-a-mile of wading through knee-deep mud, I gave up and went back home)
Many of you know that I am an afficiando of the Brayton cycle, which does not use the phase change effect for heat addition and rejection. The working fluid of the Brayton cycle is always a gas. Because of that, there’s no way to add heat to a gas without it getting hotter, and there’s no way to take it out without the gas getting colder. Isothermal heat transfer simply isn’t possible. So right off the bat, the Brayton cycle has a major strike against it relative to the Rankine cycle. Why consider it?
Because if you have a large difference in temperature between heat addition and heat rejection, the Brayton can actually outperform the Rankine. This is because any working fluid you might choose for the Rankine cycle, be it water, mercury, potassium, etc, has basic thermodynamic limitations in its temperature range. The gases used in the Brayton cycle (typically helium or carbon dioxide) have far fewer, if any, such temperature limitations.
So we should just retrofit light-water reactors with Brayton cycles instead of Rankine cycles, right? No. The maximum coolant temperatures of the light-water reactor are such that a Brayton cycle would perform much worse than a Rankine cycle in a light-water reactor. There’s not much you can do about it, either, because if you go much hotter, you’ll melt the centerline of the oxide fuel of the reactor.
But reactors that can achieve much higher coolant temperatures, such as the gas-cooled pebble-bed reactor or the liquid-fluoride reactor, can utilize Brayton cycles to their advantage, and they incur far less penalty when they raise their heat rejection temperatures to the point where they can use air-cooling for the reactor instead of water cooling.
What does this mean for Utah? In my opinion, it means that high-temperature reactors, of whatever sort, using gas turbines and heat rejection to air, are going to be much more successful in the arid West than the conventional reactors that use water cooling.
About this time ten years ago, I bought a copy of the Tori Amos album Little Earthquakes. I listened to it over and over, especially the title track, which conveys the sense of pain and desperation that I felt back then over what I thought was heartache. I was living in the high desert of California, by myself for the first time ever in my life, and Tori’s pained lyrics seemed to go so well with my emotional state.
Oooh these little earthquakes…here we go again.
Doesn’t take much to rip us into pieces.
After I met my wife eight years ago, Tori went back in the big box of CDs, where she has remained until a few weeks ago. I dug her out and started listening again. I can’t explain how attractive certain songs are for you when you feel a certain way.
Ten years ago, I might have been forgiven for listening to Little Earthquakes. I only lived a few kilometers from the San Andreas Fault, that huge north-south rift scarring California. Life has little earthquakes too, and sometimes it has big ones.
There was a little earthquake in Japan last week that has brought nuclear energy back into the headlines in the way that nuclear folks don’t usually want. Sensationalized media talk about radioactive water spilling into the Sea of Japan, and professional anti-nuclear activists are having a field day screaming about how dangerous earthquakes are to the reactors of the United States.
On a related note, Assemblyman Chuck DeVore of California is working on a ballot initiative in California to legalize the construction of new nuclear reactors. His bill has exclusions for reactor construction in areas where seismic safety is a concern, which according to this map, is a large fraction of the state:
Some time ago, I had the idea to base thorium reactors in submarines that would float several miles offshore and provide power and fresh water to coastal residents. A little investigating showed that others had had similar ideas (but not with thorium reactors). A common thread in the patent applications for the ideas (and there were several) was that such an arrangement provides a great deal of safety in the event of seismic activity. Essentially, your reactor is floating in a big viscous medium and can “ride” out even the worst tremors.
Such an idea perhaps ought to receive greater consideration for places like California and Japan. There’s nothing we can do about the fact that there will be “little earthquakes” in those places for many tens of thousands of years, but we could base reactors in such a way they they could ride out those events without concern for damage to the reactor.
Something to think about.
Discuss and comment on this subject on the Thorium-Forum.
Thank you so much for your kind words of sympathy and support. The last 18 days have been the most horrible of my life. Mornings where you wake up and have a few seconds of normalcy before the terrible memory of loss returns. Evenings where your arms ache to hold a child who is not there anymore. Nights spent on your knees in prayer asking “why?”
I’m coming around again. People keep asking me if I’m “okay” and I’m really not sure what that means anymore. Sometimes I think, “well, I haven’t cried yet today, so maybe I am okay” but other days I think “I’m okay because I already had a good cry this morning.”
The vast majority of you will never know what it is to lose a child, and for that, I am surpassingly grateful. A hundred years ago, families would bear ten children hoping to keep four. The death of a child was sad but not unexpected. And everyone knew what it was to lose a child.
Fortunately, due to marvelous advancements in medicine, transportation, and sanitation, we generally get to keep our children and they live long after we sleep in the grave. We don’t know what the loss of a child is like, and for that, I am very grateful.
Many of you have said “I don’t know what to say, but I am sorry…” Thank you for these words. These are the right words. The fact that you would even say them means so much to me, especially when you are someone who I have never met. Thank you for caring enough to leave a comment.
I’ve dropped my classes I was taking this summer, and well as just about every extraneous activity in my life. But I want to continue with this blog and this effort, because I think it is very important. We need clean energy, and we need a lot of it. I think there will be many contributions to the ultimate solution, but I believe that thorium has the potential to be the bulk of the solution. I’m going to keep working on this, for many reasons, but one of which will be as a memorial to my precious son. I hope that I can successfully explain my reasons for hoping that a bright future yet lies ahead of us.