Here’s a question I have often wondered, as I’ve tried to understand the point of view of those who oppose nuclear power–how much of their opposition is driven by the longevity of nuclear waste?
If long-lived nuclear wastes are the main issue they have against nuclear power, then thorium could go a long way towards alleviating their concerns.
If on the other hand, waste is only the issue du jour, and a solution to the waste issue would simply cause them to harp on other aspects of nuclear energy, such as proliferation, potential terrorism, CO2 release from mining, and my favorite stupid one–thermal pollution.
I really wonder because I know there are people that are simply categorically opposed to nuclear power because it represents some other evil to them–whether it’s democracy, capitalism, globalization, industrialization–whatever evil they feel like they want to attach to nuclear industry. I don’t think I’ll ever be able to change the mind of someone like that.
On the other hand, I often encounter colleagues who are well-educated, span the range of political inclinations, and yet are opposed to nuclear energy. These are the people who I really want to understand “why” because I think they might be reasoned with. And an issue I often seem to hear is the longevity of wastes.
For instance, last night I was listening to a podcast from Rod Adams’ “Atomic Show”. The guest was a mining and nuclear engineer from the University of Michigan. Well-educated, well-versed–no nuclear opponent by any stretch of the imagination, but certainly not as enthusiastic about the prospects of future nuclear energy as Rod was. He challenged Rod on several points, and one of his primary concerns about the expansion of nuclear energy was “what do we do with all the long-lived waste?”
Now this fellow knew what thorium was, and he spoke on several occasions about its merits. He knew the difference between a transuranic isotope and a fission product, and he had studied the geology of Yucca Mountain extensively. Perhaps he did not think that thorium fuel cycles were a realistic near-term possibility. But nevertheless, I perceived that this fellow was hesitant to endorse nuclear energy as a primary, dominant energy source for the world. To be quite honest, if it meant an enormous expansion of conventional uranium-fueled, once-through light-water reactors, I would be hesitant too.
So I will wonder, and perhaps some of you could offer your thoughts–do you think that the longevity of nuclear waste (meaning today’s form of nuclear waste) is the primary issue that concerns most people about nuclear energy?
I’ve taken a little time to do another comparison slide between the waste generated in a typical light-water reactor compared to a liquid-fluoride thorium reactor. For the light-water reactor waste calculations, I used the WISE Uranium Nuclear Fuel Energy Balance Calculator and used a baseline value of 1 GW*yr of electricity production. I accepted all the defaults of the calculator, with the exception that I used a fuel burnup of 35 GW*day/MTU, and a electrical generation efficiency of 33%.
For the fluoride reactor, I assumed
For the power conversion system, I assumed a triple-reheat helium gas turbine with a 50% electrical conversion efficiency, which is consistent with
The data on thorium mining came from ORNL/TM-6474.
Here’s the results of my calculations:
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Even with an initial engineering background, and a mechanical engineering background at that, I was really surprised how important formal education in nuclear engineering is. I had thought, when I first began learning about thorium and fluoride reactors several years ago, that doing some overall reactor design calculations would be as simple as getting a nuclear engineering text, parsing through it for the relevant equations, and doing some quick and simple sizing.
How wrong I was!
Nuclear engineering turned out to be devilishly difficult to learn. Now most folks are smarter than I am, and will probably have less trouble, but since I began my formal education in nuclear engineering in the fall of 2003, every class has seemed like it would just about kill me or take my little brain to the limit of where it could go. But six classes later, I’m still alive, still kicking, and have a lot more perspective on the problem (and I even have a decent GPA so far!)
Nuclear reactors are very difficult to design because of the basic behavior of neutrons during fission. They are borne at high energies, and then they have to slow down through moderation. Modeling this is extremely complicated because of what’s known as “resonances” in heavy materials like uranium, thorium, or tungsten. Resonances are when a material has a real predilection for a neutron of a certain energy. It REALLY wants those particular energy neutrons and it gobbles them up like Pac-Man. Your poor little neutrons are trying to slow down and moderate and all the while these nuclides are just waiting to eat them, like the monsters who gobbled up Ulysses’s sailors as they sailed past them.
Just modeling the real behavior of neutron moderation in the presence of resonance-absorbing nuclides is enough to scare you to death, but then you get to all the issues of neutron transport–the Boltzmann Transport Equation. Like the Navier-Stokes equations for fluid flow, the BTE is a perfect model of what happens in a reactor. And just like Navier-Stokes, you can forget about ever solving it. The best you can do is apply increasing levels of simplifying assumptions to the BTE, and try to get to a point where solution is possible. Problem is, each simplifying assumption removes more and more of the value of your eventual solution.
Therein is the “art” of neutronics–like Kenny Rogers “Gambler” you gotta know when you can simplify and know when you can’t simplify. And know when to run! It gives me a whole lot more respect for those early nuclear pioneers who had to do all this work without computers!
What does all this have to do with MIT? Well, I just read this week that MIT is going to the effort to put all their classes online, and it occurs to me that some enterprising person who wanted to get a decent understanding of the realities of nuclear engineering could “take” these classes on line and learn a thing or two. It would take a lot of determination and personal initiative, but it could save you a lot of money.
It’s too late for me–I’m going to finish my MS degree in nuclear engineering at the University of Tennessee (who I’d like to commend for offering an excellent distance learning program!) but some of you young folks might like to think about it!