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Of which the waste can be dealt with with current technology (pebble bed reactors),

I don't get it - why pebble bed reactors? They don't seem suitable for destroying waste (that is, transmuting and fissioning the transuranics). First off, many PBRs are completely unsuitable for this - because they are uranium-cycle reactors in the thermal spectrum, and are not breeders - they do not destroy TRUs, but in fact create more of them. I guess some PBRs could be breeders - maybe the thorium PBRs, but even then there's a huge problem. PBRs are not designed for a closed fuel cycle - quite the opposite, the extremely-hard ceramic pebbles are designed to be indestructible and inert, not easily amenable to chemical reprocessing (which as a first step, means dissolving or melting the spent fuel elements.)

There are other reactors that are designed for closed fuel cycles, and disposing of nuclear waste. One class is the liquid-metal fast breeder reactors (LMFBR), like the IFR that was developed at Argonne national lab. The IFR was designed around a reprocessing cycle (pyroprocessing): that is why it uses metal fuel, as opposed to the common metal-oxide fuels, which are harder to reprocess because you need to reduce the very stable uranium/plutonium oxides. (Or even worse, the carbide fuel in TRISO pebbles).

Another reactor designed for reprocessing is the molten salt reactor, which has a liquid core (!) of a low-melting point fluoride salt. This is even more amenable to reprocessing - there is no need to break down - and then fabricate again - the solid fuel elements, as there aren't any!

But as far as I know, pebbles beds have no chance as a closed fuel cycle.

When Nuclear Power generation finally switches to Pebble bed Modular Reactors [first invented in the US and blocked by the Atomic Energy Commission (1944) for it's lack of military options] using Liquid Cooled Helium then I'm sure someone would rather adapt a small-scale solution, using a material medium other than water, for motherboards to do this than just using a giant water sink to account for the data center, as a whole.

ME Magazine: Pebbles making Waves, ME Magazine

PBMR Corporation

US Westinghouse takes stake in PBMR

Yes, the pebble bed modular reactor is due to start construction in South Africa in 2009. You can read more about it http://www.pbmr.com/ here.

The casing is defintely graphite (https://www.pbmr.com/index.asp?Content=4&).

I thought also that the reason PBMRs hadn't been used is that they don't scale up as far as the alternatives, which didn't fit the big centralised energy strategy. So PBMR are a safer alternative, but limited in application, requiring a more distributed approch to energy generation.

You're talking about the pebble bed modular reactor, the one that China is planning to build tons of by 2030 or something.
https://www.pbmr.com/2_about_the_pbmr/2_2what_is_t he_pbmr.htm

Reading the article linked to from /. story about pebble bed reactors would show you that the turbines are driven by helium in the primary loop. There is no secondary loop. Water can be used as precooling before the helium is recompressed, but water or steam is not required.

(1) is it going to be safe similar to the claims of ?

(2). If at any point (including) end of life, some unsavory party can break into the reactor and steal the plutonium. Even if there are alarms, the thief would be long gone before the autorities could arrive (if it is not the government themselfs doing this).

You gotta be kidding.

You should take a look a the links. From pbmr.com: The PBMR will generate about 19 tons of spent fuel pebbles per annum, of which less than one ton is depleted uranium. The spent fuel is much easier to store than fuel rods from Pressurized Water Reactors, because the silicon carbide coating around the fuel particles will keep the radioactive decay products isolated for approximately a million years. This is longer than the activity of any of the radioactive products, including plutonium.

The PBMR system has been designed to deal with nuclear waste efficiently and safely. There will be enough room for the spent fuel to be stored in dry storage tanks within the PBMR building. All the spent fuel that the PBMR generates during its 40-year life will be stored on site. This means that no spent fuel will have to be removed from the site. After the plant has been shut down, the spent fuel will be safely stored on site for another 40 years before being sent to a final repository, where the following factors will ensure safe storage:

Firstly, the fission products are encased in a layer of silicon carbide. This layer forms a protective shell around the fission products, and prevents environmental contamination.

Secondly, the fuel has been packed in a graphite sphere. Graphite is an inherently stable material. This means that the spheres will not break or disintegrate, and thus the configuration of the spent fuel will not change.

Finally, the density of spent fuel in each sphere is so minimal that the repository can be packed as efficiently as possible.

there is something new.

Here.

The basis for this technology has been around for at least 30 years, as you would know if you read the background on the site. The PBMR is not the same technology as the AVR or THTR at Hamm-Uentrop.

The THTR reactor was not closed due to technical problems. The problems it experienced were related to the loading of fuel, an issue addressed by the PBMR. Even Greenpeace admits regarding the THTR "In 1989 the reactor was permanently closed due to both economic and political reasons."

Whenever the issue of pebble-bed reactors has been discussed there has been allusion to "problems" in all reactors produced so far (in Germany, Japan and the US) -- without indicating that none of these reactors have been closed down for safety reasons! The biggest problem with these reactors so far has been getting them to reliably and economically perform their purpose.

As for information exchange so that South Africans know whats getting build "in their back yard" - we have a strong anti-nuclear lobby already. Unfortunately we also live in a country where 16% of the populate are illiterate and only 25% have completed secondary education -- so just how do you think it is possible for the public to make an educated decision on how long our coal reserves are going to last, whether a particular incarnation of nuclear technology is better or worse than pumping out greenhouse gasses, and what our electricity requirements are going to be in 2010?

All the spent fuel that the PBMR generates during its 40-year life will be stored on site....

Finally, the density of spent fuel in each sphere is so minimal that the repository can be packed as efficiently as possible.

Now, what if there is some malfunction, and a sizeable amount of non-spent pebbles are accidentally "discarded": Instant nuclear bomb! After all efficient packing is one way to reach critical mass and get some megaboss oomph!

That's kinda the point of these pebbles. I have seen a lot of work on this reactor technology, and waste is an important concern. The Fuel spere pebbles safely encase the nuclear material -- you can handle them and throw them around a bit. "The silicon carbide coatings that surround the uranium fuel particles within the pebble form a miniature pressure vessel. This pressure vessel provides a highly efficient barrier against the release of fission products during operation." - from the linked-to site

It would seem, critically, that the waste can be stored on site for 40 years, does not need to be transported elsewhere, and is inherently more stable than the waste in a typical water reactor.

There are new designs out there. Check out, for example, the pebble bed modular reactor (PBMR). A Web search on CANDU will turn up another design. Unfortunately, for political and economic reasons stated in a parent post, these will probably never be developed in the USA, even if the above-mentioned PBMR is built in South Africa as planned. We're going in the wrong direction; a program at Argonne National Laboratory to reduce atomic waste by transmutation was scrapped by Al Gore and company in 1995, and G.W.Bush's energy plan revolves almost entirely on developing natural gas and oil resources with only token mention of atomic, solar and wind energy.

Oops, the PBMR site requires a secure connection.

This Toshiba design looks a bit like the South African pebble bed modular reactor and the General Atomics GT-MHR, so the idea is not really new.

Well, the steam generators don't have to be that big, actually. For example, there are steam locomotives in use which are about as powerful as similarly sized diesel locomotives, only their fuel consumption is a lot worse.

Anyway, you don't necessarily need steam either. There are those nuclear batteries used on spacecraft and shit like that. Terribly inefficient, but you get electricity from a nuclear reaction with no moving parts at all. And don't forget gas turbines, that many of the more modern nuclear powerstation designs are using. They can be a lot smaller than comparable steam generator systems. For example the Pebble bed modular reactor.