are heavy, into lighter so-called fission products, such as technetium. This releases energy, along with sub-atomic particles called neutrons. Some of these neutrons go on to hit further uranium nuclei so hard that they, too, shatter and release yet further neutrons. It is this chain reaction that sustains the process. Other neutrons, however, are captured by uranium nuclei. That makes those nuclei heavier still, converting them into neptunium, plutonium, americium and curium.

All these by-products of nuclear fission are radioactive, and many will remain so for thousands—sometimes millions—of years. They are thus difficult to dispose of; the most practical idea being to bury them deep underground in stable rock formations and just wait. On top of that, the plutonium could, in principle, be extracted to make nuclear bombs. But the organisers of the Kumatori Accelerator-driven Reactor Test Facility (KART), at Kyoto University in Japan, which starts up this month, have dusted off an old scheme that might help overcome the problems of nuclear waste. This is to transmute the by-products still further, into something that can be disposed of safely.

Analysis in another blog...

The plan is to build a “sub-critical” nuclear reactor. Such a reactor would not be able to sustain a chain reaction. Instead, the nucleus-transmuting subatomic particles would be supplied from outside, using a particle accelerator.

About 95% of the mass of a piece of used nuclear fuel is unconverted uranium, so the first step is to extract the 5% that is waste. This is done chemically. The radioactive elements to be transmuted are then turned into a target for protons fired out of a particle accelerator. Neutrons cannot be speeded up in an accelerator because they have no electric charge to grab hold of. But the main role of the protons is to knock neutrons free from nuclei in the target.

These neutrons should, if all goes well, be absorbed by the technetium and other fission products, transmuting them into new elements. They will also break up the elements heavier than uranium into products similar to those from uranium fission. Although, initially, the new elements will be more radioactive than the spent nuclear waste was, that radioactivity will last only a few hundred years. This means that the dumps into which they are put need not be as secure (or as expensive) as those envisaged for long-term waste-storage. And, as a bonus, the whole process should generate more energy than it consumes. Indeed, Dr Rubbia's original name for the device was an energy amplifier.

now it doesnt work on all long life waste elements but it will reduce the volume of LT waste massively.

And this is "dusting off" an old scheme. We can deal with LT waste anyway as we see from Australias idea of becoming a global repository in its geologically ideal and hugely remote interior.

But alas we modern westerners must worry and in doing so distort a vital debate about sustainable energy sources and economic growth in a world where more than half of humanity is currently denied its fruits. It may well be we shouldnt have nuclear power but the reasons should not be waste disposal, they should be practical, political and economic.

I suspect we MUST have nuclear power. Fast breeders or whatever. We will see several competing technolgies no doubt and some will be better than others. Thats good.
ws