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A New Class of Nuclear Reactors
prunedude tips this quote from a post at Freakonomics about Japan's nuclear crisis:
"The folks over at IV Insights, the blog associated with Nathan Myhrvold's Intellectual Ventures, point out that it was the complete loss of power that disabled the cooling systems protecting the plant's reactors. Which raises the question: Is there nuclear technology that could withstand such a catastrophe? Possibly. TerraPower, an Intellectual Ventures spin-off that also boasts Bill Gates as an investor, is working on a new reactor design called a traveling wave reactor that uses fast reactor technology, rather than the light water technology used at the Fukushima Daiichi plant. The two biggest advantages of the fast reactor design is that it requires no spent fuel pools and uses cooling systems that require no power to function, meaning the loss of power from the tsunami might not have crippled a fast reactor plant so severely."
Of course any new reactors designed will have safeguards against any previous disaster - it's the ones that never happened before that fuck us.
Humor from a Genetically Molested Mind
From: http://en.wikipedia.org/wiki/Thorium
Some of the benefits of thorium when compared with uranium as fuel:
* Weapons-grade fissionable material (U-233) is harder to retrieve safely and clandestinely from a thorium reactor;
* Thorium produces 10 to 10,000 times less long-lived radioactive waste;
* Thorium comes out of the ground as a 100% pure, usable isotope, which does not require enrichment, whereas natural uranium contains only 0.7% fissionable U-235;
* Thorium can not sustain a nuclear chain reaction without priming, so fission stops by default.
Actually, the pebble reactor in Julich, Germany (I'll assume that's what you are referring to) had severe problems leading to long half-life fission products contaminating the soil and water around the reactor.
The flaws are not based on the particular design of the AVR facility, but seem to be flaws in the whole pebble-bed idea. You can read the Julich Research Facilities own post-mortem here: http://www.eskom.co.za/content/AVR-Report-Press.PDF
Germany ran a pebble bed reactor at the Nuclear Research Facility at Juelich. The Juelich post-mortem report concluded that pebble bed reactors have severe problems in practice (at least some of them base design flaws), in the specific case of the Julich AVR reactor leading to Strontium-90 contamination of the soil and aquifer beneath the reactor.
The post-mortem report is posted here http://www.eskom.co.za/content/AVR-Report-Press.PDF
Some interesting bits from the report:
The AVR primary circuit is heavily contaminated with metallic fission products (Sr-90, Cs-137) which create problems in current dismantling. The amount of this contamination is not exactly known, but the evaluation of fission product deposition experiments indicates that the end of life contamination reached several percent of a single core inventory, which is some orders of magnitude more than precalculated and far more than in large LWRs.
[...]
It leads to the conclusion that the AVR contamination was mainly caused by inadmissible high core temperatures, increasing fission product release rates, and not - as presumed in the past - by inadequate fuel quality only.
From the conclusions:
As outlined above there exist unresolved safety problems in pebble bed reactors for design basis accidents, as for beyond design basis accidents like severe air ingress with graphite burning. Previously a superior safety behaviour of pebble bed reactors was claimed compared to other nuclear systems including an allegedly catastrophe free design. According to the above presents arguments there are doubts, whether this depicts reality.
So while pebble bed reactors have some advantages over traditional designs, they are by no means the silver bullet that some people make them to be.
These are only the size of a shipping container and are a self contained unit. They would be a great way to bypass the NIMBYism associated with nuclear power plants. They are also much safer. If these can be bought by people with a bit of cash in the attic and installed in the countryside unknown to the neighbours we can all enjoy cheap nucular energy while everyone is blisfully oblivious to the fact that the neighbours little 'storage' container is actually a nucular power plant
It turns out that pebble beds aren't quite so maintenance free. Although the helium used as a coolant doesn't become radioactive, the graphite in the pebbles absorb radioactive metals and spread it around in graphite dust particles. Both the the AVR and HTR reactors in germany had big problems with contamination of the reactors due to this and due to the inability of the pebbles to contain radioactive isotopes.
Also, the pebble bed itself can't be instrumented so it becomes a black box resulting in unexpected hot currents of gas that can be significantly (200+K) warmer than expected. This resulted in maintenance issues in the two reactors in Germany (I don't think there is information on other experimental or production reactors using a pebble bed design). These problems might be surmountable but right now they're pretty big issues.
If Bill Gates' life was to flash before his eyes, would it be a blue flash?