[PaulHoule]

The use of thorium in the MSR is perhaps 30x more fuel efficient than the current light water reactor. Large amounts of thorium have been buried in the desert by the U.S. government. Also, sufficient deposits exist in the U.S. to support centuries of use.

As for nuclear waste, the real reason why the problem appears intractable is that nuclear waste is not waste.

The LWR gets only 2% or so of the energy in uranium, the same fuel could be reprocessed and used in fast breeder reactors to release the other 98%. In fact, it is the presence of plutonium and other actinides in spent fuel that requires environmental isolation beyond 500 years or so. If we use those actinides as fuel, they do not need to be buried, and if we do that, the volume of waste is vastly reduced along with the half-life.

The fast breeder/reprocessing route has not been commercialized as of yet for a number of reasons. Probably the most discussed is that plutonium, neptunium and other actinides useful for nuclear weaponry could be nicked from the reprocessing plant.

The thorium MSR is an alternate path to a breeder, aka a "thermal breeder". In the case of the MSR, the reprocessing is done online or nearline to the reactor. It is also possible to do thermal breeding with thorium with a modified version of the light water reactor. Reprocessing that is a bitch though...

The most immediate problem facing the industry is an inability to say "it is going to take X years and Y dollars to build a reactor" and then finish it somewhere near on schedule and on budget. Being over 10% would be no scandal, but it is still looking more like 10x than 10%.

[ornel]

Doesn't reprocessing produce a lot of high level waste as a byproduct, thereby worsening the waste problem?

And I understand the Japanese had an experimental breeder reactor for a long time and never achieved actually producing any commercially viable electricity. They did get lots of plutonium, though, which may be turned into bombs any moment.

[PaulHoule]

Early on the fission products were stored in acid solutions in tanks. Circa 1980 the technology was developed to evaporate the solution and trap the fission products inside glass.

Plutonium from either a LWR or FBR fuel cycle is heavily contaminated with isotopes that will cause a bomb to predetonate or get really hot. Somebody with advanced technology (say Japan's government) could probably use electromagnetic separation to remove the unwanted isotopes, but you wouldn't expect ISIS to be able to do it.

The real thing terrorists would want to nick from a reprocessing plant is Neptunium 237; it has a large critical mass compared to plutonium, but it can be separated by chemical means and will not predetonate.

In the 1970s people wrote hang-wringing papers wondering if inventory control could be made good enough to detect diversion, a 2000s accident at Sellafield's THORP plant showed that it probably can't. They lost an Olymptic size swimming pool worth of fluid containing upwards of 50kg of Pu and around 1000kg of U and did not notice for months.

To be fair, it drained into a containment area and did not threaten anyone. They were able to clean it up. But obviously the inventory control was nonexistent.

THORP has been successful at producing plutonium oxide powder but the UK was unable to fabricate it into fuel elements and had to ship it to France.

[wbl]

Reprocessing separates rapidly decaying fission products from slowly decaying transuranics. The transuranics go back in to be burned, the fission products decay comparatively rapidly.