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  • Polyanna Pinker’s Power Profundities

    Posted on October 10th, 2018 Helian No comments

    Recently Steven Pinker, public intellectual and author of a “history” of the Blank Slate debacle that was largely a fairy tale but at least drew attention to the fact that it happened, has been dabbling in something entirely different. Inspired by the latest UN Jeremiad against climate change, he has embraced nuclear power. In a series of tweets, he has endorsed articles advocating expanded reliance on nuclear power, such as one that recently turned up at Huffpo cleverly entitled “If We’re Going To Save the Planet, We’ve Got To Use the Nuclear Option.” As things now stand, that would be a dangerous, wasteful, and generally ill-advised idea.

    I say “as things now stand.” I’m certainly not opposed to nuclear power. I’m just opposed to the way it would be implemented if we suddenly decided to build a bevy of new nukes given current economic realities.  The new reactors would probably look like the AP1000 models recently abandoned in South Carolina. Such reactors would use only a fraction of the available energy in their nuclear fuel, and would produce far larger amounts of long-lived radioactive waste than necessary. They are, however, cheaper than alternatives that could avoid both problems using proven technologies. Given the small number of players capable of coming up with the capital necessary to build even these inferior reactors, there is little chance that more rational alternatives will be chosen until alternative sources of energy become a great deal more expensive, or government steps in to subsidize them. Until that happens, we are better off doing without new nuclear reactors.

    As noted above, the reasons for this have to do with the efficient utilization of nuclear fuel, and the generation of radioactive waste.  In nature there is only one potential nuclear fuel – Uranium 235, or U235. U235 is “fissile,” meaning it may fission if it encounters a neutron no matter how slow that neutron happens to be traveling.  As a result, it can sustain a nuclear chain reaction, which is the source of nuclear energy. Unfortunately, natural uranium consists of only 0.7 percent U235. The rest is a heavier isotope – U238. U238 is “fissionable.” In other words, it will fission, but only if it is struck by a very energetic neutron. It cannot sustain a fission chain reaction by itself.  However, if U238 absorbs a neutron, it becomes the isotope U239, which quickly decays to neptunium 239, which, in turn, quickly decays to plutonium 239. Plutonium 239 is fissile. It follows that if all the U238 in natural uranium could be converted to Pu239 in this way, it could release vastly more energy than the tiny amount of U235 alone. This is not possible in conventional reactors such as the AP1000 mentioned above. A certain amount of plutonium is produced and burned in the fuel elements of such reactors, but the amount is very small compared to the amount of available U238. In addition, other transuranic elements, such as americium and curium, which are produced in such reactors, along with various isotopes of plutonium, would remain dangerously radioactive for thousands of years.

    These problems could be avoided by building fast breeder reactors. In conventional reactors, neutrons are “thermalized” to low energies, where the probability that they will react with a fuel nucleus are greatly increased. The neutron spectrum in “fast” reactors is significantly hotter but, as a result, more neutrons are produced, on average, in each encounter. More neutrons means that more Pu239 can be produced without quenching the fission chain reaction.  It also means that the dangerous transuranic elements referred to above, as well as long lived fission products that are the source of the most long-lived and dangerous radioactive isotopes in nuclear waste, could be destroyed via fission or transmutation. As a result, the residual radioactivity resulting from running such a nuclear reactor for, say 30 years, would drop below that released into the environment by a coal plant of comparable size in 300 to 500 years, as opposed to the thousands of years it would take for conventional reactors. And, yes, radioactivity is released by coal plants, because coal contains several parts per million each of radioactive uranium and thorium.  Meanwhile, a far higher percentage of the U238 in natural uranium would be converted to Pu239, resulting in a far more efficient utilization of the fuel material.

    An even better alternative might be molten salt reactors. In such reactors, the critical mass would be in liquid form, and would include thorium 232 (Th232) in addition to a fissile isotope.  When Th232 absorbs a neutron, it decays into U233, another fissile material.  Such reactors could run at a lower neutron “temperature” than plutonium breeders, and would be easier to control as a result.  The liquid core would also greatly reduce the danger of a nuclear accident. If it became too hot, it could simply be decanted into a holding pan where it would immediately become subcritical. Thorium is more abundant than uranium in nature, so the “fuel” material would be cheaper.

    Consider the above in the context of the present. Instead of extracting the vast amounts of energy locked up in U238, or “depleted” uranium, we use it for tank armor and armor piercing munitions. In addition to this incredibly stupid waste of potentially vast energy resources, we dispose of huge amounts of it as “radioactive waste.”  Instead of treasuring our huge stores of plutonium as sources of carbon-free energy, we busy ourselves thinking up clever ways to render them “safe” for burial in waste dumps.  It won’t work.  Plutonium can never be made “safe” in this way. Pu239 has a half-live of about 25,000 years.  It will always be possible to extract it chemically from whatever material we choose to mix it with.  Even if it is “reactor grade,” including other isotopes of plutonium such as Pu240, it will still be extremely dangerous – difficult to make into a bomb, to be sure, but easy to assemble into a critical mass that could potentially result in radioactive contamination of large areas. Carefully monitored breeder reactors are the only way of avoiding these problems.

    According to the Huffpo article referenced above,

    Doesn’t nuclear power contribute to nuclear weapons proliferation? No. Weapons programs do not depend on civilian nuclear power, which operates under stringent international safeguards.

    Really? Will the “stringent international safeguards” last for the 25,000 years it takes for even half the plutonium waste produced by conventional reactors to decay? I would advise anyone who thinks it is impossible to fabricate this waste into a bomb, no matter what combination of isotopes it contains, to take an elementary course in nuclear engineering. The only way to avoid this problem is to burn all the plutonium in breeder reactors.  Predictably, the article doesn’t even mention the incredible wastefulness of current reactors, or the existence of breeder technology.

    It’s nice that a few leftist “progressives” have finally noticed that their narrative on nuclear power has been controlled by imbeciles for the last half a century. I heartily concur that nuclear energy is a potent tool for reducing carbon and other greenhouse gas emissions.  I simply suggest that, if we decide to return to nuclear, we either provide the subsidies necessary to implement rational nuclear technologies now, or wait until it becomes economically feasible to implement them.

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