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Uranium Pebbles May Light the Way
kristy_christie writes "According to Wired News, South Africa's state-run utility giant Eskom and its international partners want to build the world's first commercial 'pebble bed' reactor, which, instead of using fuel rods, 'is packed with tennis ball-size graphite "pebbles," each containing thousands of tiny uranium dioxide particles'. To developers, the Pebble Bed Modular Reactor promises a rebirth of nuclear energy. Proponents insist that the reactor's design features make it 'meltdown-proof' and 'walk-away safe'."
However, coal power plants release more radioactive waste into the enviroment than nuclear power plants and still provide most of the power in the US.
There's big money in keeping things the way they are. Nuclear power is so heavily regulated that it is too expensive. Thats the only reason we don't have more of it. If the other types of plants were regulated just as strictly we'd switch over as quickly as we could build them.
19 tons of heavy metal radioisotope doesn't take up much space. These elements are quite dense.
I remember seeing a demo of this stuff in school.. It's so safe to use in a reactor it's crazy; they referred to it as "walk-away" safe. Lose _all_ cooling in the core, leave it over the weekend, fix it on Monday. It was going to bring about a revolution in safety WRT nuclear power generation. It's nice to see this finally coming to fruition.
Africa's state-run utility giant Eskom /rant
I'm going to pop a vein! Afirca is not a country, it's a continent . South Africa, the country where Eskom resides, is a country in Africa (easily confused with South America by Americans. South America is a continent south of North America, the continent with three different countries on it, including the USA). There are 54 independent, different countries in Africa, each with their own government. Africa is not simply a big ol' jungle where everyone speaks Swahili (only 50 million of the more than 700 million people in Africa speak Swahili).
OK, now that I got that off my chest: Eskom has been talking about this for a while now, and they are facing some resistance to the idea. The problem being the general conception that "nuclear is evil".
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
Languages aren't inherently fast -- implementations are efficient
Nuclear power is a subject that is near and dear to my heart having spent a part of my life working in the industry for Uncle Sam. There are three real issues with Nuclear power that keep it a hot button issue:
* Proliferation of WMD. Widespread use of nuclear power creates huge opportunites for people to get their hands on fissile material or highly radioactive material. A "dirty bomb" consisting of a few hundred pounds of waste and a few hundred pounds of explosives could do incalcuable damage. Nuclear power and nuclear weapons are NOT high tech. It's technology from the era of propeller airplanes, black and white movies, radio and vaccum tube electronics.
* Economics: widespread use of nuclear power would render a large sector of the global economy useless. There is a substantial interest in keeping the world dependent on our dwindling supplies of fossil fuel -- remember suply and demand? What happens when the supply decreases and demand increases? Many nations, corporations, and ultimately individuals stand to get very, very rich by monopolizing the resource (OPEC is a benign example compared to what we'll see in the future)
* Finally, there is a more practical issue: much of today's power challenges are demand side issues. Most people are blissfully unaware of what it takes to supply a couple of killowatt hours to their homes and especially businesses.
-- $G
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?
i-name =twylite [http://public.xdi.org/=twylite], see idcommons.net
The problem with radioactive waste is that its half-life is in the tens of thousands of years.
We don't know who's going to be blowing who up even this time next year.
Very little of the waste produced by power plants has this sort of a half life. Even so, the less radioactive a substance, the longer the half-life. Those elements that do lasts tens of thousands of years simply aren't producing that much radiation.
Highly radioactive substances, on the other hand, have shorter half lives, and aren't much of a worry after a few decades.
-josh
U-238 is barely radioactive, with a halflife of about 4500 million years. U-235 on the other hand is way more radioactive, and thus the part they are interested in using for reactorcores.
Not true. The half-life of U-235 is 710 million years -- enriched uranium is NOT too hot to handle.
Pu-239 (half-life 24400 years) and Pu-240 (half-life 6580 years) are hotter and are the reason spent fuel needs to be sequestered for so long. But the really nasty, ultra-hot radioisotopes are all the neutron-rich fission byproducts from splitting U-235 or Pu-239. Byproducts like barium-140, cesium-134, cesium-137, and iodine-131 have half-lives in the days to only a few years that make them intensely radioactive (thousands of times more radioactive than Plutonium and millions of times more radioative than U-235). Worse, these byproduct elements will chemically react with ordinary matter, form water-soluable compounds, and lodge in living tissue if injested.
Fact: Spent fuelrods from reactors are a major enviromental problem.
Extremely true, but not because of U-235.
Two wrongs don't make a right, but three lefts do.
Yep, some people will die from an increased incidence of cancer...
I don't know if that is the case... Coal, the major alternative to nuclear, has numerous carcinogens among it's combustion byproducts. These carcinogens are not tightly controled like the nuclear ones are, they are simply dumped into the environment surrounding the plant. I would much rather have a nuke in my back yard, than a coal burner...
"I'll have a Guinness, no wait, make that a Coors Light" -Grad student I work with, who shall remain anonymous...
The latest cost estimates for building a 'demo model' is about R10 billion, and will be completed in 2008. That's about 5 years over schedule, if my memory serves me. The PBMR company ltd., not Eskom directly, is building this thing. That company's shareholders are currently Eskom and BNFL. Since BNFL is currently being restructured, as the cleanup costs for Sellafield have forced it into bankruptcy, Eskom is the only real player. (US company Exelon was involved, but now they've pulled out)
R10 billion is way more than Eskom can afford. Therefore they are looking for external partners to invest in the project, and that depends on selling PBMRs being commercially viable. Now, nuclear electricity is very expensive - one of the reasons that the world nuclear industry is in the doldrums. There was a paper in the South African Journal of Science about this some time back, which examined the economic models Eskom was using for PBMR, and found them to be wildly optimistic.
So if the economics are so screwy, why is Eskom pursuing this project? No one really knows, but I'm sure the fact that the chairperson of Eskom, Reuel Khoza, effectively controls one of the main contractors (IST), through a holding company has got something to do with it. Even if the PBMR project fails, Khoza and buddies will end up much richer. IST got handed a R260 million (?) contract, which is about as much as its previous annual turnover. Their shareprice went through the roof, making Khoza and co's share options worth a lot more.
Besides the Reuel Khoza link, there is an argument to be made that difficult-to-manage technologies like PBMR will be an incentive for the government to keep a much more centralised and powerful Eskom around for much longer. Eskom is currently facing deregulation and restructuring, and this Apartheid-legacy parastatal needs to justify why it still needs to exist. Experience in other companies has shown that deregulating nuclear power is very hard, so PBMR might be a bargaining chip in the complicated game around Eskom's future.
Funnily enough, the Wired article and the Slashdot responses have all the hallmarks of engineers - in love with 'sexy technology' while pretty much ignoring the bigger political/economic picture.
Peter
As a poster above said, the really HOT nuke waste is fairly easy to get rid of - breader reactors. Carter banned them in the US for a few reasons
1)It was just post TMI
and
2)To do them right, you end up with NEAR weapons grade PU in the reactor and in the reproccessing plants. He thought there was too much of a security risk to have this much PU running around
A LOT of the initial assumptions on the cost of Nukes had to do with the fuel being reprocessed - aka, make your waste into fuel again - what is left is low level stuff - LONG half life, but also low radiation
One of the huge problems we have with storage is we keep trying to store "Mixed" waste - It's got high level waste (say, PU) mixed with low level waste.
-- 73 de KG2V For the Children - RKBA! "You are what you do when it counts" - the Masso
Incidentally, almost every power producing reactor in the western hemisphere is water moderated. And, discounting RBMK and their ilk, also in the rest of the world, for that matter. As you say, water moderation means that if the coolant boils off the chain reaction will stop. CANDU is in no way unique in this aspect. The problem is that the fuel will continue to generate a significant amount of heat even after the chain reaction is stopped, because of the radioactive decay of very short-lived fission products. This heat is enough to melt the reactor core if it's not cooled. This is essentially what happened at three mile island. That's why all nuclear power plants have all kinds of emergency power supplies etc. so that they can continue cooling the reactor after they shut it down.