-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Tue, Sep 11, 2007 at 04:14:29PM +1200, Russell McMahon wrote: > > A fun example with nuke plants is how no-one ever seems to point out > > that when they say it'll take "100,000" years for spent fuel to > > become > > non-radioactive about 99,000 years of that time it'll about as safe > > to > > handle as it was when it was in the ground in the first place. (er, > > look up exact figures, off the top of my head) > > Not at all true. Alas. > > > When nuclear plants are decommissioned it's standard practice to let > > them sit for a few years > > for some very unusual values of few No, it's very common. Many of the decay products present in spent fuel rods have quite short half-lifes, ranging from 5 to 90 years. For instance, the most important longer life contaminates in the Chernobly disaster are Sr90 and Cs13, with half-lives of 28.9 and 30.23 years respectively. The iodine that caused so many thyroid cancers is completely gone now, it has a half life of only 8 days. The US atomic energy commision uses the term "Safestore" to describe the 30 year wait built into many of their decommisioning projects. This allows %95 of the radioactivity to decay before final decomissioning happens. Improved robotics technology, and public pressure, is allowing some of these plants to be fully decommisioned sooner than planned, but you can easilly see the principle. Some examples, as well as other options, are given here: http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/decommissioning.html In the UK there is a debate over whether to use a 25 year, or 80 year, decomissinging plan for their Magnox plants. 25 year would require robotic equipment, while a 80 year wait would allow humans to dismantle the plant: (see decomissioning section) http://en.wikipedia.org/wiki/Magnox Unfortunately I can't find the linked source pdf... > > But more importantly, unlike > > practically every other form of industrial polution tritium is > > guaranteed to become half the problem that it was in ~12 years due > > to > > it's half-life. You can't say that about lead pollution! > > Tritium is a major issue if it's out here and not in there. > BUT Tritium is a straw man. It's a valuable product in its own right > and if it can be removed for use/sale/storage it will be. Sure is! Currently Canadian price, we produce most of it from CANDU reactors, is roughly $30,000,000/kg I suspect there is likely a fair bit of incentive there to reduce Tritium emissions... > Do you know why your watch is Glowing? Absolutely, I've got a tritium glowlight on my keychain, and intend to do some art projects with tritium one of these days. > Do you know how your typical H bomb is Going? > Give me a T. give me an R. Give me ... . Yup, any search of Tritium turns up all sorts of stuff from the US on how they need a supply to maintain nuclear weapons. A big political issue is keeping sales of tritium from going to US war purposes... > > But pesky facts like that just complicate things don't they... > > Not a lot. Alas. Well, in my perception of risk and reward, I think that complicates things a lot. :) Compare the nuclear industry to long-term storage of chemicals, many of which will remain dangerous forever, and who's behavior is less certain. > > What really pissed me off about the whole thing was how her research > > has > > been, to date, based on a few non-blinded studies > > None of us like those who abuse science and fact in the interests of > personal profit. > > More useful would be to quote a few of the many properly carried out > studies and related peer reviewed papers that do show possible areas > of concern from non ionising radiation. > > A single example, and I'm not even going to Gargoyle for any > supporting references, is that workers who work in industries which > generally have high exposure or proximity to electric fields, have > been shown in some properly designed and executed studies, to in some > cases show significant (but not necessarily overly large) correlations > with certain types of diseases. Notably but not only certain cancers > AFAIR. One Swallow does not a summer make, and correlation does not > prove causality. But when the Swallows are flying thick and fast - as > they do at Capistrano and Sellafield, then no matter how imapparent > the mechanisms may be, I wouldn't raise a family there. But, I'm still > an electrical engineer. My house is relatively close to an HV pylon > line - but I walked the area with a field meter and di some careful > thinking before we bought. > > Back to ionising stuff. I have never yet seen a nuclear waste disposal > proposal that makes assumptions about longevity of secure storage that > I would be happy with if I knew that my children's children's > children's children were going to live nearby. Most things manmade get > very tired by 100 years (1907 car ...). Some few things get, with > maintenance, cute and very very old and rather worn out at 500 years > (Venice. Europe) . A few big things have enough big and even small > chunks left at 2000 years that make them worth going to see > (Colosseum. Pyramids.) Of the original 7 wonders of the world (which > presumbly would feature high on the list of things worth maintaining > for posterity) only ONE remains, and they now won't let you > touch/climb it AFAIK. > > Glass sealed "flasks" at the bottom of the ocean or in deep > "impervious" [tm] rock tunnel storage have a good chance of pushing > the known upper levels of human-product longevity, but not overly > more. And if the assumptions were wrong, the contractors crooked, the > acts of God just happen and reality breaks through as it always does > in reality, then too much of the stored-forever waste will be > gotten-out-of-jail-free after only hundreds of years. Or less. > > There are bacteria which can and do live inside hard nuclear waste, > mine the material, and bring selected bits to the surface. If they can > do that then almost anything else conceivable is possible. I'm not going to get into an argument about risk and tradeoffs, I think my whole point with this is that people see nuclear storage, and freak out. But yet, there's *far* less outrage over long term storage of equally dangerous non-nuclear materials. Less than 5km from my parents house, and next to one of the largest freshwater lakes in the world, is Giant Mine, a now closed gold mine. They have 237,000 tonnes of arsenic trioxide dust, which is %60 arsenic and water soluable stored underground in three huge caverns the size of 6 story office buildings. It's deadly stuff and will remain deadly forever. The solution is to freeze it using Yellowknife's cold weather into essentially permafrost. This solution requires the long term maintainance of a system of thermal siphons that keep the "ice-cubes" cold enough that they stay frozen and immobile. Yet, there is so little public outrage about this that I can't even find any usefull references to the "Giant Mine Remediation Project" on the internet. I only know this stuff because I've visited the place. That is *not* an isolated example by any means. Yet, we worry about nuclear waste? Huh? I mean, hell, the volume of that waste, from that one mine, is more than the entierty of high-level nuclear waste. We've got lots of good reason to think that anything dumped in certain undersear mudflats will stay put regardless. We already know that when natural nuclear reactors have happened due to geological chance the reaction products seemed to pretty much stay put. I'm a pragmatist, and while yes, there is risk inherent, I just see our society so blindly accepting so many other risks but focusing on so few. > We don't even NEED to mention terrorism. Hardly even incompetence, > self interest, corner cutting and the whole of human nature. > > > Let's see some of those "most nuclear waste is American Apple Pie and > Motherhood after only 1000 years" references. Not Apple Pie, just not all that bad compared to where it came from. First of all look at the "Back end" table on wiki: http://en.wikipedia.org/wiki/Nuclear_waste You can see how much of the yield is in very short term stuff. This stuff decays quickly, and therefore has lots of energy to hurt you. Hell, stand 1m away from a freshly spent fuel CANDU fuel rod for one minute and you're dead. As for toxicity over time here's one such graph: http://www.nuclearfaq.ca/cnf_sectionE.htm It's interesting how quickly it becomes less toxic than even naturally occuring murcury ores. Another such graph, this time focusing on strict radioactivity: http://www.phyast.pitt.edu/~blc/book/chapter11.html Again, after 1000 years most of the danger is gone, after 10,000 *everything* has decayed to less radioactivity than the natural ore. The "lethal oral dose" estimations in the same artical are similar, and show how quickly the danger goes away, from fantastically deadly to... well, eating a pound of glass in itself is a dangerous thing. Though, I must admit, I suspect the above lethal oral dosage calculations didn't take into account chemical toxicity, uranium is essentially like eating lead... Then again, it just depends on how soluable the stuff is. Still, I think you can see my point. - -- http://petertodd.org -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFG5uaN3bMhDbI9xWQRAsEdAJ9FIq9rVbvUn9WRyH7iWuqZ3YLi2QCgmkB0 aYKPvO6/1wH99CPKXIFlMkk= =4O+e -----END PGP SIGNATURE----- -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist