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Cooler Fuel

The argument against casks is that they are merely temporary, not meant to serve longer than perhaps 100 years, and that they are a kind of surrender, leaving this generation’s waste problem to a future generation to solve. Yet their impermanence is exactly what’s good about them. A century hence, spent reactor fuel will be cooler and more amenable to permanent disposal. In fact, within a few decades, the average fuel bundle’s heat output will be down to two or three hair dryers. After 150 years, only one-thirty-second of the cesium and strontium will remain. The remaining material can be buried closer together without boiling underground water. Reduced heat means reduced uncertainty.

Granted, spent fuel will be far from safe after such a relatively short period. Even after 100 years, it will still be so radioactive that a few minutes of direct exposure will be lethal. “It’s many, many, many thousands of years before it’s a no nevermind,” says Geoffrey Schwartz, the cask manager for Indian Point, which is owned by Entergy Nuclear. “But the spent fuel does become more benign as time goes by.”

The fuel could be more valuable, too. For decades, industry and government officials have recognized that “spent” reactor fuel contains a large amount of unused uranium, as well as another very good reactor fuel, plutonium, which is produced as a by-product of running the reactor. Both can be readily extracted, although right now the price of new uranium is so low, and the cost of extraction so high, that reprocessing spent fuel is not practical. And the political climate does not favor a technology that makes potential bomb fuel – plutonium – an item of international commerce. But things might be different in 100 years. For starters, the same fuel could be reprocessed much more easily, since the potentially valuable components will be in a matrix of material that is not so intensely radioactive.

And in 100 years, advances in reprocessing technology might make the economics compelling. The existing American technology dates from the Cold War and involves elaborate chemical steps that create vast quantities of liquid waste. But an alternative exists: electrometallurgical reprocessing. Though research into the technique has lagged of late because of the economic climate, the concept might be taken more seriously in the future. Electrodes could sort out the garbage (the atoms formed when uranium is split) from the usable uranium (the uranium-235 still available for fission and the uranium-238 that can be turned into plutonium in a reactor), in something like the way jewelers use electrometallurgy to apply silver plate. Resulting waste volumes would be far smaller.

Perhaps most importantly, in 100 years, energy supply anddemand might be very different. Reprocessed nuclear fuel might well become a critical part of the energy supply, if the world has run out of cheap oil and we decide that burning coal is too damaging to our atmosphere. If that happens, we might have 1,000 nuclear reactors. On the other hand, we might have no reactors, depending on the progress of alternate energy sources like solar and wind. At this point, it’s hard to tell, but we are not required to make the decision now; we can put the spent fuel in casks for 50 years and then decide if it is wheat or chaff.

There is a final, more practical reason that we might choose to take the plutonium out of spent fuel for reactor use: it makes the remainder easier to store. For the most part, what’s left will not be radioactive for nearly as long, and the sheer volume of material will be lower. Mark Deinert, a physicist at Cornell University, says reprocessing, like recycling, removes about half of the material from the waste, dramatically decreasing storage costs and effectively doubling the capacity of a facility like Yucca.

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Tagged: Energy

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