"You?" I'm not Scandinavian at all (short and dark, in fact). Did spend a winter in Stockholm, and definitely wouldn't recommend it for the weather. Also have to add, in case it's not obvious from your message, that the Danes have a much better sense of humor than the Swedes, and better beer as well.

The Swedes are such a cold people. Even the Danes consider them distant and formal (not to mention a bit condescending).

I'm the treasurer for a small 501(c)3 (ITT4AS501(c)3), not a lawyer, but here's what our legal counsel has told us in the past: we can give money to whomever we want provided that the "regrant" is to further the goals of the corporation, as set forth in the corporate charter that was approved by the state. Depending on how the charter was drawn up, that can be either pretty broad or really, really, really broad. There are a few limits - if you start embezzling large amounts, or if most of the proceeds of the organization wind up in the pockets of one person, then the IRS will come sniffing around. But regrants in general are absolutely permissible.

I remember a few years ago that some comments in a electronics blog were censored; they referred to Panasonic's parent company Matsushita.

From (my contribution on) the talk page of the article on Romance Languages:

Can anything be done about the automated censorship of the Dante quotation in footnote 12, which now ends: "nam domus nova et dominus meus lo**censored**ur"? The censored part is a "c" followed by a "u" followed by an "n" followed by a "t"; the original can be found, for example, here: http://www.greatdante.net/texts/vulgari/vulgari.html (chapter XI, paragraph 7).

Apparantly, their Automated Puritan can pull lady parts out of the middle of a Latin word.

I'm breaking this off; not interested in communicating with someone who keeps calling me names.

No, this is wrong in several ways. If the reactor had been successfully scrammed, the control rods would have been down (all the way in the reactor), and the reactor would be in the process of shutting down (the control rods absorb enough neutrons to stop the chain reaction). They were stuck partially up and couldn't be lowered, plus the cooling system failed (both due to lack of electricity).

I made a nonsensical suggestion because your suggestion of flooding the inside of the reactor was equally nonsensical and I couldn't figure out what you were trying to get at. What's the worst possible outcome from a Fukushima type of situation? That would be an explosion (from pressure) of the reactor which would permanently poison a large part of the surrounding area especially down wind. A comparatively small version of this happened with the comparatively small amount of radioactivity that was vented to relieve pressure and prevent this much greater catastrophe. Even this small amount of radioactivity was enough to fry the electronics of robots sent it to work on the thing in a couple of hours.

Now, what happens when you open up the reactor to dump boron in? The whole thing blows up. More precisely, there's a catastrophic (meaning, very rapid) release of pressure and you've just released millions of times the amount of radioactivity than had previously been released. Of course, you've fried any electronics in the vicinity, so it's going to be difficult to dump boron in after that, but since the worst possible disaster has already occurred, the motivation is probably not quite so strong at that point. This is like deliberately opening the barn door, letting the horse out, and then closing it again to keep the horse in. Doesn't make any sense at all.

Hmm. It sounds like you've got some concepts right but filled in some of the blanks with your own interpolations, and these aren't right at all, so the results aren't right at all. Here's another important concept: the density of the material matters when it comes to temperature. If you put a pot into a 350-degree oven and let it heat up, then touch the pot, you will burn yourself. But you can hold your hand in the oven for several minutes without being uncomfortable at all, provided you don't touch anything solid. Air is less dense than the pot; it doesn't hold very much heat or transfer it very efficiently. The plasma in a fusion reactor is much, much less dense than air. You wouldn't want to hold your hand in it (neutron flux would be a problem), but it's fragile, has to be coddled and nursed at every point in its life (the fusion reactor projects are trying to figure out to do this). If something goes wrong, the plasma breaks. It's really, really wispy stuff, not dangerous to anything else, in spite of the high temps.

Oh, I guess you can blow it up through chemical means, like anything else, but a fusion explosion is physically impossible. You may understand the difference between fission and fusion but you don't seem to really *appreciate* the difference. They have nothing common, other than the use of the strong nuclear force (which is, obviously, much strong that the electromagnetic force that powers fossil-fuel power plants). To my ears - maybe to the ears of the person you wrote at ITER as well - it's as if someone were deathly afraid of refrigerator magnets because that uses the same force that runs electric chairs. Fusion and fission plants honestly have about that much in common.

Again, here's a summary of some of the differences, from the safety point of view:

Fission: uses the densest materials known, some inherently toxic; generates large amounts of toxic waste; reaction not only continues spontaneously, in fact, increases unless positive measures are taken to slow it down or stop it. So, if something goes wrong at a fission reactor, you have to scramble to make sure that the reactor doesn't get out of control What happens if a fission reactor blows up? A big, big mess.

Fusion: uses the lightest materials known,;no inherent (chemical) toxicity; essentially no toxic waste; reaction does not occur at room temperatures and pressures, but only under very difficult-to-maintain conditions - if these conditions are disrupted, the reaction stops. A runaway fusion reaction is physically impossible because the moment you disrupt the plasma - inject too much or too little fuel in, get the temps wrong, whatever - the plasma breaks. So, if something goes wrong at a fission reactor, whatever problem you have, at least there won't be a runaway fusion reaction because the reaction will have stopped. And what happens if a fusion reactor blows up (for example, someone flies a plane into it)? Not much - the fuel isn't toxic and won't stick around, anyway). If I were a terrorist and wanted to cause maximum damage, a fusion reactor would be a stupid thing to blow up; much better to go after a chemical factory. Or a fission plant.

What coolant? If you think that a fusion reactor has to be cooled, you're not understanding it. I must not be explaining it very well. The problem with keeping a fusion reactor going is keeping it hot. If anything bad happens to it, the plasma gets all bent out of shape (literally) and cools, and the reaction stops. This is the opposite of fission, where if anything bad happens, the reaction runs away.

No, this is not correct. It's like saying that by lighting a cigarette, you're teetering on the edge of a firestorm like the one which destroyed Dresden. Actually, it's not even like that: a carelessly deposited cigarette can start a nasty fire (although not a firestorm; that requires simultaneous fires); but there's no way that a fusion reactor can blow up. If you inject too much fuel by accident, the delicate balance of the plasma will be disrupted, and the reaction will stop.

Everything you say is correct right up until the last clause - if you mix too much fuel in by accident, it won't explode. You made that part up. You'll wreck the plasma and the reactor will shut down.

Not true - obviously they design the things to avoid a steam build up. Remember that the Fukushima reactors were supposed to flood with water to cool them down; problem was that the water pumps failed when all the sources of electricity, including the backup diesel generators, got knocked out. The real reason they're not in use is that that kind of safety system is expensive, and the industry hasn't been highly motivated to spend the extra money. There's one kind which is in the process of being approved; unfortunately, it looks as if they're building them on the cheap, again: http://www.homelandsecuritynewswire.com/controversial-nuclear-reactor-design-moving-toward-approval

Again not true - it depends on where you dump it. Most reactor designs include some kind of water flooding as a safety measure. If you cool the outside of the reactor, that can reduce the pressure inside, as you know from experimenting with your pressure cooker at home.

No point in putting boron on the outside; that's not where the reaction is. And if you open up the reactor to get the boron inside (how? by exploding it?), you're going to get serious radioactive nasties spewing everywhere.

As I said, I may not be explaining things very well, and I share your feelings about the inevitability of mistakes, but it seems to me that your fears about fusion power aren't that cogent.

And we're still just talking to ourselves. This is really weird.

At any point, you can kill the power going into a fusion reactor and the reaction will stop. In an ITER-type reactor, the plasma will smash itself (or "brush" might be a better term, considering how wispy the stuff actually is) against the reactor walls, cool off, turn into a gas, and no more fusion. The reactor wall might be damaged a bit (maybe, maybe not; depends), but that's all.

If you remove the power from a fusion reactor, the temperature doesn't increase: it goes down, almost immediately. This is the opposite of a fission reactor. A "thermonuclear chain reaction" is possible only under certain conditions, namely accumulating the right amount of the right material in a given space (at a given density). For fission, the materials are extremely dense metals, so you can accumulate them at room temperature. For fusion, the material is an extremely wispy gas (the wispiest element that exists, in fact), so in order to accumulate enough at the right density, you need pressure several million times what you get in nature (and when you compress something that much, it heats up, too; again to some millions of times what you get in nature or, at least, on earth). The chain reaction will keep going as long as you maintain these conditions, but let up the pressure and temp for even the slightest instant and the reaction stops.

Incidentally, there are designs for fission reactors that use passive safety controls. For example, a big tank of water is place above the reactor; it requires electricity to keep its outflow valves shut. If the electricity fails, the valves open and the reactor is flooded with water. Obviously something like this is a good idea; equally obviously, it's not at all needed for fusion reactors where, if the electricity fails, the reaction stops automatically.

I don't know about you being an ignorant moron, but the guy who wrote that ITER Q&A document is, if he thought it would be reassuring. The facts may be all right, but the tone is that of a very nervous grade-school teacher. (I'm assuming that a man wrote this, on the grounds that no woman could be that socially inept).

At any rate, there are plenty of things to be concerned about for safety, but the number one problem is PR: the public confusing fusion and fission, maybe dimly aware that both have something to do with atomic nuclei and bombs and genuinely scary stuff. The fact that industry flacks and their official enablers lied about fusion repeatedly over decades doesn't help. Hard to blame people for being wary. This is what that Q&A is supposed to address. I think it doesn't do a good job, but that's a PR problem, not a scientific one.

Anyway, there are plenty of safety issues, as with any industrial plant - high voltages, high temperatures, that sort of thing. Also, and special to fusion reactors, is the neutron flux, which is a stream of neutrons spewed out of a fusion reaction. This has to be shielded from things that you don't want to kill, like people. It's also a major, major problem in designing a reactor, since it causes metals to deteriorate. The process is called "neutron embrittlement." You can think of it as neutrons pushing the electrons in the metals around and messing up the structure of the crystals. The big problem is that it's cumulative - as long as the fusion is going, the metals around it get more and more brittle. If you shut the fusion reaction off, to give the reactor walls a rest, it doesn't do any good - the embrittlement just continues when you turn the fusion back on. With the little research reactors that they've been working with, this hasn't been a problem, but for a larger power reactor that's supposed to be in service for decades, there are no known materials that will withstand the flux. They're working on some graphite-fiber things; I don't know how that's going.

So, what's the worst that can happen with a fusion reactor? I don't know - anything that disrupts the reactor will cause it to shut down, so there's no way that the reaction can get out of hand. Maybe if the shielding failed and nobody noticed, then people in the immediate vicinity of the reactor would be exposed to a lethal dose of neutrons. Kind of hard to imagine how this could happen, and it wouldn't affect anybody outside the plant.

As for a self-sustaining reaction, of course fusion will do that (look at the sun - I don't mean that literally), but it requires special conditions (high heat, pressure) to maintain a plasma. When those conditions are removed, the reaction stops. This is why physicists didn't take "cold fusion" seriously - it's physically impossible (and its proponents were chemists - plus the Utah State Legislature - not physicists). (Still, good scientists know that their theories may be wrong, and a number of research teams tried duplicating the cold-fusion demonstration; they all failed.) In a power fusion reactor, some of the power generated will go into maintaining the temperature and pressure needed for the plasma - just as, in every power generating station, some of the power generated goes back into keeping the plant in operation.

I'm not saying it's perfectly safe; no industrial plant is. But it doesn't look particularly dangerous, and the thing that makes fission particularly dangerous - the possibility of a runaway reaction - is totally impossible.

This is very informative:
http://hardware.slashdot.org/story/12/04/11/0435231/mit-fusion-researchers-answer-your-questions

Ah, this is the mistake. You're right about fusion - when "confinement" - well, moderation, fails, you wind up with a runaway reaction.But it's not like that for fusion - when confinement fails, the reaction stops. The reason is that the plasma (which is where the reaction takes place) is very, very fragile. If it hits the walls of the container, it cools off, and that stops the reaction immediately.

True dat. But you need the right conditions for the reactions. Fission, in a chain reaction, will create those conditions by itself. An extreme case would be weapons-grade uranium, which doesn't even need any mechanism to explode, just a suicide bomber who has two pieces of uranium which together exceed critical mass; drop one on the other and BOOM! Instant atomic bomb. Not the most efficient way to use the material, but quite adequate for terrorist purposes.

Fusion's not like that. It requires a plasma. You can get one by assembling a bunch of hydrogen the mass of the sun and letting gravity do the work or, if that's not convenient, by exploding a fission bomb in order to generate heat high enough to form a plasma (which is why a fission bomb is used as a trigger for a fusion bomb). Obviously a bomb plasma doesn't last very long. For a fusion reactor, you've got to figure out how to confine a plasma *NOT* in order to confine the reaction, but rather to keep the reaction going at all. Whenever the plasma breaks out of its confinement, it turns into ordinary hydrogen, and ordinary hydrogen molecules bump into each other all the time without so much as bruising their electrons.

If you've got the time (a lot of it) and the interest, I highly recommend the books by Richard Rhodes "The Making of the Atomic Bomb" and "Dark Sun" which are mostly about history, but also go into a lot of the technical details.

Have you noticed that you and I seem to be talking only to each other? This can't be a good sign.

oh, p.s., I not only thought that a Chernobyl explosion was possible, I thought it inevitable. There's no particular technical reason that we can't design safer fission reactors (well, aside from waste disposal, which doesn't have a technically satisfactory solution), but economic factors have been unfavorable (safety costs money, and there's always the temptation to do things on the cheap), and the sociology is even worse: we don't know how to design a system that's fail-safe against human stupidity. Chernobyl blew because the techs deliberate operated it outside the design parameters to see what would happen. Poor design, such as lack of a containment vessel, magnified the effects of their poor judgment.

thorium is safer than uranium and plutonium, fine. They're all fission, which depends on a self-sustaining reaction. If you remove whatever moderator you have (graphite, boron, whatever), the reaction heats up because you need the moderator to tamp it down. There are reactor designs that have a "built-in" moderator to help with this problem, so that if, say, the control rods (which contain a moderator) all get stuck in the pulled-out position, the reactor will settle down to a steady-state, but these all depend on a moderator. ("Heats up" is partly a metaphor - physical heat is generated, of course, but the major effect is that the fission reaction gets faster.)

Fusion reactors, if we ever get them going, will work in exactly the opposite way. If you remove all the controls which confine the reaction, the plasma will cool off and the reaction will stop within a fraction of a second. In other words, the problem with fission is to prevent a reaction from getting out of hand and exploding, but the problem with fusion is to keep the reaction going. Fusion bombs use fission bombs as a trigger: it literally requires an atom bomb to get any sort of explosion out a fusion reaction. Needless to say, any fusion power reactor isn't going to be configured in any way that could produce a fusion explosion.

Um ... maybe you should find out what fusion is before you regale us with your opinions. If you think that thorum fission is safer, or that it's physically possible for a fusion reactor to explode, then you have no idea what you're talking about.