The Wall Street Journal has published an editorial by William (Bill) Tucker, author of Terrestrial Energy, titled There Is No Such Thing As Nuclear Waste. Of course, we all know that headline is a bit of an oversimplification designed to capture attention, but the sentiments are in the right place. The op-ed is a condensed expression of a complex subject written in a way that makes it understandable to the readers of a publication like the Wall Street Journal, people who can get excited about technology and use technology but are not necessarily technical experts.
Unfortunately, in the condensation of ideas, Bill made a bit of a math error – something we all have done at times. He also made a suggestion that I believe points in the wrong direction. Here is my response to his piece:
Though I fully agree with the overall thrust of Bill Tucker’s excellent editorial, There’s No Such Thing as Nuclear Waste, there are some refinements that need to be understood. It really is difficult to condense a very complex subject into the space of an op-ed, so this is not a slam on the excellent work that Tucker has done in trying to make his idea more understandable. Opponents of nuclear power make much more egregious errors in their effort to oversimplify why they hate the technology.
– 12 ounces of uranium is not enough to power San Francisco for five years. The rule of thumb is that a city the size of San Francisco needs about 1000 MW of electrical power. Each day, the city uses 1000 MW-days of energy. Uranium fission releases about 1 MW-day per gram of heat, but it takes 3 MW-days of heat to make one MW-day of electricity due to the thermodynamics involved in the heat conversion system. Therefore, each day, a reactor large enough to power a city the size of San Francisco would need to consume 3000 grams – about 106 ounces of uranium. The five year number would be about 193,000 ounces (about 6 tons). I believe that Bill’s number of 12 ounces of uranium consumed during a five year residence in a reactor is a PER FUEL ROD number and that phrase got left out of the editorial by accident. A light water reactor contains tens of thousands of fuel rods. Rods are grouped into assemblies, reactors are made up of assemblies. Current large reactors require between 121 and 193 assemblies, each containing between 179-264 rods.
– The U-238 may be innocuous stuff that could be put back where it came from as Bill suggested, but its higher calling is to be used as fuel. Just like the U-235, it contains about 1 MW-day of heat per gram of potential energy. It just takes two or three neutron impacts to break it apart rather than one. That is an simplified version of what actually happens – the first neutron impact converts U-238 – indirectly – to Pu-239. Pu-239 is fissile and has a good chance of splitting with the next neutron that hits it. In purpose designed reactors, U-238 is simply a slower burning fuel that can be converted over time at a rate that matches the rate of U-235 or Pu-238 being consumed. That is made possible by the fact that each time a fissile atom breaks apart, it produces between 2-3 neutrons. Though we have not yet widely deployed reactors that perform this alchemy, we have built operational prototypes that have worked pretty well considering the early stage of knowledge for something that takes a very long time to test. (I know impatient people want instant gratification and answers, but the cool thing about this testing is that there is a valuable product produced during the test – massive quantities of usable heat.)
Otherwise, great editorial and great message. Unlike its competition, fossil fuel combustion, heavy metal fission does not inherenty produce a nasty waste product that needs immediate release into our common atmosphere. It produces a relatively tiny amount of very dense material with useful properties that can be easily stored until it can be recycled and reused. Canceling Yucca Mountain may have been the smartest decision yet by the new administration.
Publisher, Atomic Insights
Host and producer, The Atomic Show Podcast
Founder, Adams Atomic Engines, Inc.
(Edited from the original comment posted at WSJ opinion forum to remove grammar and typographical errors. Note to self – proofread before posting.)
I hope that Bill does not take this the wrong way and refuse to come back on the Atomic Show. I really enjoyed our last conversation and admire the work that he is doing in spreading the word about how wrongly some people have portrayed the vast potential of atomic fission – what he calls Terrestrial Energy.