Slashdot Mirror
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.
"Africa's state-run utility giant"... WTF?
Africa is not a state or a single country for that matter, it's a continent made up of many states. Please be specific, ppl are very ignorant about this, just like many think that all africans speak the same langauge (there are over 200 langauges in Nigeria alone for example).
On a scale of power generated per ton of input material it is incredibly efficient (bested only by those power sources which require no nonrenewable input, like wind/tidal/etc.) Possibly not true, because for the same energy output you need a lot more material and maintenance with the "renewable" systems - a gigawatt of wind power would be 100 10MW windturbines - and 10meg windturbines would be VERY big. Steve
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".
For you geographically challenged people. Africa is a whole continent. Like North America, South America and Australia.
South Africa is a country. It's at the tip of Africa. You'll never guess where it is in Africa.
It was a British Colony, but gained independence about 55 or so years ago, and promptly began to institutionalise pernicious racially-based discrimination. It was called Apartheid. After a long struggle (40 years) the white people agreed to share power and democratic elections took place. Nelson Mandela (you may have heard of him) was elected president.
The economy of South Africa is split - there's a strong first world component, and a large third world component. The first world component rivals the economies of Europe and the USA in sophistication - though it's much smaller. The third world component - i.e. subsistence farming, and subsistence trading - involves many more people. Unemployment rate is high - a few years ago it was 40%. Not sure what it is now. HIV/Aids rate is probably the highest in the world - hitting around 10% of population. Some places have rates as high as 40%. The current government until recently has ignored the problem.
Eskom is a world-class power utility. They have existing nuclear reactors, which were learning grounds for the Apartheid state in their quest for nuclear weapons. (Ten or so years ago South Africa admitted that they had nukes, and then destroyed them. Thank you Nelson Mandela and South Africa for making the world a safer place.)
It's questionable whether South Africa needs more nuclear power plants but Eskom has traditionally had a strong technocratic streak. (I was an employee a long time ago.) SA is rich in coal and natural gas.
I personally think that the money could be better spent given South Africa's problems - the only justification would be to export the technology. And maybe greater access to nuclear expertise is not what the world needs.
Jeff Veit
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.
Conversion Rate Optimisation French / English consultant
This technology has been around for at least 30 years. The Germans even built an example pebble bed reactor at Hamm-Uentrop which has led to the technology being heavily criticized by enviromentalists. Normally I would be hesitant to swallow raw what enviromentalists feed onto the internet, especially the religiously fanatical German anti nuclear lobby, but in this case their claims are reenforced by the fact that their opinions of pebble bed reactors are shared by the German state who shut the Hamm-Uentrop plant down in 1989 after the management covered up serious problems with the reactor. The whole affair has led the People of Hamm-Uentrop to start a citizens group which among other things aims to start an Information exchange with the people of South so that the Africans can take into account the German experiences before one of these things gets built in their back yard. Feel free to call this a troll but with so many people singing the "See!! I told you nuclear is safe" psalm here I figured the other side of the coin deserved a mention.
Only to idiots, are orders laws.
-- Henning von Tresckow
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
Such reactors are not new, e.g. there was/is one in Hamm-Uentrop, Germany called "THTR 300".
Building started 1970, reaction started 1983, shut down 1988, disassembling started 1991.
Its output was 308MWe, so I assume it was not just a toy.
AFAIK they had problems with the moderation and breaking of the balls.
Nothin' new, actually.
Why do they invest more money in such technologies. They have the Sahra desert.
No thay don't. This article is about a company in South Africa, which is nowhere near the Sahara Desert. It's a bit like responding to an article on Canada by mentioning the desert in Mexico because hey, both are in North America.
My Karma: ran over your Dogma
StrawberryFrog
It's been done before. In Germany. It was called "schneller Brueter". It never went operational.
The rationale was that it would be vatsly more efficient. In practice, those "balls" were harder to control than the normal rods. In testruns they would jam as they were processed in the facility.
So it's neither the first time this is being built, nor is it the answer to all energy-questions in the world.
Just a rather pedantic point but something that I do find irritating: Eskom is not a state run utility it privatised many years ago and is listed on the Johannesburg Stock Exchange (JSE).
It has been mentioned above that there is some opposition locally to the idea. Based on some of the comments in support of the idea it would be great if those interested could inform Earthlife Africa of your opinion.
> what happens to the depleted uranium?
Depleted Uranium is barely radioactive - totally different from nuclear waste. It does NOT comes from reactors. I think you need to do a little reading.
"The longer the half-life, the lower the radiation" may seem obvious, but escapes many.
... yet that doesn't keep you from judging and condemning something.
First of all, as was already said, the waste produced by fission plants is _not_ depleted uranium. It's not like "new batteries" and "used batteries", you know. When a uranium nucleus splits, it splits into much smaller nuclei. Ones which aren't uranium at all.
Second, I get this feeling that you don't understand how depleted uranium weaponry even works. I keep reading all sorts of SF (read: stupid) posts about how it explodes inside the tank, or how some shell's explosion spreads uranium dust and debris all over, and whatnot.
The only quality of depleted uranium is that it's an extremely hard material. Much harder than steel or even than tungsten penetrators. Its only quality is that a sharp tip made of depleted uranium, can go straight through armour made of steel. That's all.
It's also _not_ used in high explosive ammo. And APHE ammo (i.e., ammo which is both armour piercing and explosive) was last used by the Soviets in WW2. They discarded it as being useless.
The shells that tanks shoot at each other today are _not_ explosive. (Regardless of how it looks otherwise in computer games.) The preferred large caliber anti-tank ammo nowadays is APFSDS: Armour Piercing Fin Stabilized Discarding Sabot. It basically shoots a thin sharp metal rod with fins. Much like a crossbow bolt, if you will.
This goes through armour by sheer kinetic energy, and by being sharp. Again, just like a medieval crossbow bolt would.
Why is it important that it's very hard? So it doesn't deform while going through armour. Think a crossbow bolt with a steel bodkin tip, and now think one with a rubber tip. The rubber one will deform and spread the impact over a larger surface, whereas the steel one might stay sharp as it goes through armour. (Thus keeping the impact concentrated on the small surface of the tip.)
A polar bear is a cartesian bear after a coordinate transform.
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
Nuclear power plants are required by law to have insurance. Do your research, rather than just loosely citing a couple of environmentalist texts. Here is just one of many links pointing out that these plants are indeed insured.
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...
While I do think that nuclear power will make up more energy in the future, I also think that with a bit of inginutity we can lessen the need for plants. Basically, by storing excess power, we can add 33% to 100% power to the plant. This would also allow for alternative energy input. One approach is via 2 water resoivors with hydro power and simply use excess power to pump the water back.
Perhaps a better way is for us to spend money on high thermal storage with salts. Ideally, we would do small units and spread them out to provide emergency power in local areas (think hospitals, anywhere on the coast esp, Florida, Texas, and California).
I prefer the "u" in honour as it seems to be missing these days.
If you had RTFA you'd know that the pressure vessel is lined with a rather thick layer of graphite (and also has a large graphite column in the center). Besides that, I doubt a 5cm sphere of even the hardest substance would rub holes in a steel pressure vessel in even large multiples of the entire plant lifetime. And what vibration? These aren't Mexican Nuclear Jumping Beans, the don't move around on their own.
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
When the Three Mile Island reactor had its partial core meltdown, note that there was still enough safety margins active that its radioactive release was very small indeed. It definitely helped that the reactor was inside a strongly-built containment building, which essentially confined the radioactive release.
Since Chernobyl had NO containment structure, when that reactor's fissile material pile exploded there was NOTHING to stop its release into the atmosphere.
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.
Don't forget about the one at the Tokaimura fuel processing plant in Japan in 1999. It was an inadvertent criticality in which two workers were killed by radiation exposure and dose rates in the surrounding area were significantly elevated. As usual for nuclear accidents, it involved a lot of gross stupidity (unapproved modifications of procedures, bypassing safety systems).
The pebble reactors achieve the same effect using a different design principle.
Each pebble is a sphere.
A large number of spheres are arranged in a pile.
The density of the uranium is a function of the radius of the spheres.
Like most things, the pebbles expand as they get hot.
In turn, this creates a negative feedback loop which should prevent a catostrophic failure.
Same story - silly russians cutting costs, but costs get cut and things are mismanaged on a spectacular scale in the USA too. Three Mile Island is the textbook example of why you have to have enough staff to watch the contractors when they try to rip you off. The same weld joint was x-rayed several hundred times, with only the numbers changed on the print to pretend that other more inaccessable joints were checked. When the accident occured and people looked at the x-rays to see if there had been any pre-existing flaws they found that the area where the problem occured had never been checked.
TMI is a textbook case, but for other reasons:
a) Had the operators not shut down the safety systems (because they thought it was going to overpressurize the reactor), the event would have been a non-event. Lesson - be sure you know what's happening before you stop safety systems, and is why emergency procedures are designed to make operators diagnose and respond to symptoms, not events.
b) Steam cools as it expands - which is why the downstream temp after the leaking valve was much lower than the operators expected - and caused them to think the valve on the presurizer was shut, not open. Had they checked a p - t diagram, they would have discovered their error. Lesson - double check assumptions,especially when anomlies can be explained by a different conclusion than you reached.
c) A similar event occured at Davis-Besse, but the operators reacted correctly and no damage was done. Unfortunately, no one bothered to tell other plants about the events. Lesson learned - share information (which was why INPO - the Institute of Nuclear Power Operations was founded)so you don't make the same mistakes as someone else - something the aviation industry learned the hard way a long time ago.
I'm a consultant - I convert gibberish into cash-flow.
Chernobyl is also a good example of a RBMK reactor which is a unique design in that it is graphite rod moderated. The less you cool it the more efficent it gets - what is called a "positive void coefficient" - after Chernobyl many of the same RBMK reactors were fitted with many safety systems including containment. They still don't meet western safety standards, but there are several still in operation today - some of them are even connected to Europe's grid and producing electricity continent wide as a write this. The biggest is one called "Ignalina" in Lithuania.
Chernobyl had a cap on it - in fact when Unit 4 exploded it blew off the 2000 ton shield off the top of the reactor. When it exploded they were doing a test and were impatient with the performance of the control system and had subsequently shut off the safety systems. Oops.
RBMK reactors are kinda cool in the sense they can be refueled while online, but other then that...