By "leaner fuel mixtures" they're not saying that you have to change the gasoline itself - you just inject less of it.
Even without running leaner, yes, this can improve efficiency: it can ignite the fuel closer to the center of the combustion chamber, which makes for a better burn. It might also ignite a longer path of the fuel, resulting in a quicker burn without detonation. You retard timing a little bit, and then do a quick burn to bring up pressure right at the best moment. This is already done on some current engines by using more than one spark plug per cylinder.
I agree that a prompt criticality is essentially impossible after a meltdown, but at the initial moment of failure in Chernobyl, much higher reactivity was easily attainable.
In an operating reactor the safety margin of reactivity is only about 0.6% between the threshold of delayed-critical and prompt-critical. The fuel alone is incapable of going prompt-critical (or even delayed-critical, in most cases) - but with enough neutron moderator present, you can get past that gap. One of the flaws of the RBMK - an insane design - is it has a long section of graphite (a neutron moderator) at the tip of each control rod to increase reactivity in certain regions when they're fully withdrawn. That's supposed to be done in a few regions at a time.
When Chernobyl popped, they had withdrawn nearly all of the control rods. At the end of the experiment, they SCRAMmed the reactor, and all the control rods descended together. It blew as the graphite sections were aligned with the bottom of the core. Thus, the bottom of the core - already primed from the previous activities - was in an extremely over-reactive configuration. The first explosion happened, causing three important things: 1, the rod channels shattered, so all that extra graphite stayed in the core; 2, a total coolant loss (which raised the reactivity considerably); 3, the fuel assemblies broke up, allowing the configuration to change further (likely with very high reactivity at some moments). It's entirely possible that those effects combined to reach a prompt-critical configuration briefly.
Ask your nuclear engineer friend for a clarification - I'll bet he was talking about a molten mess of fuel, not about an operating reactor that was placed into a *very* over-reactive configuration.
No, a nuclear explosion doesn't mean you get a mushroom cloud. Mushroom clouds occur from *large* explosions. As I said, the Chernobyl explosion was only around 10t - comparable to a MOAB but a pathetic fizzle compared to a nuclear bomb. An explosion that size DID happen - it's just a question of how. A large hydrogen explosion is also likely.
I guess you didn't bother to read the links I posted. The study wasn't based on modeling the explosion - it was based on analyzing the Xe-133 present after the meltdown. The ratios of isotopes give a picture of what processes were occurring. It's hardy conclusive, but it's a good indicator.
But weren't last few generations of reactors also supposed to be literally failsafe? Never in a thousand years would we see the types of accidents we've had five or so of in the last forty years? We were assured that by people who literally swore on their childrens' lives that it would be perfectly safe.
Who swore? Gen I BWRs were built to an standard of industrial safety that was considered adequate in the 1960s, when they were designed. "Adequately safe" never meant "perfectly safe" - it meant that the risk-reward profile was worthwhile.
I'm quite confident that if the Fukushima reactors had been replaced with ABWRs, ESBWRs, ACR-1000s, or AP-1000s, we would not be having the present crisis. In particular, all of these designs are capable of maintaining cooling even in a station blackout. This is not a case of hindsight being 20/20 - the problem of station blackouts was foreseen and mitigated, as were many others.
Part of the great increase in safety is because they're considerably simplified from GenII designs. Because of this they are more likely to survive (or simply not be vulnerable to) other failures that we haven't anticipated.
Modern nuclear safety standards are now much better than current industrial safety standards - which includes all other methods of large scale power generation commercially available at present.
...which of course are going to be "lighter" and "cheaper" because they'll have smaller containments...
This simply isn't true. Careful engineering is allowing some modest reduction in containment size in some of the latest designs compared to the 1980s era, but even the smallest ones are an order of magnitude larger than the 1960s era containments.
Chernobyl did not have a "small nuclear explosion". Period.
RBMKs (as configured at the time) had a very large positive void coefficient; after the steam explosion depressurized the vessel, the coolant was boiling like mad with essentially no liquid water inside the fuel assemblies. Combined with all the extra graphite from the control rod tips which were in exactly the wrong place, a prompt criticality was very possible as things were settling inside.
Since the assembly was slow (compared to a weapon) the criticality ended quickly as it blew itself apart. The yield was on the order of 10t (not low Kt, as expected in an unboosted uranium weapon). There are other theories for the second explosion, but this one has the best case made for it.
Anyway, I wasn't suggesting that it was the explosion itself that carried particles long distances (though it did make quite a mess locally); it just blew the thing wide open so when the fires started the only thing covering them was the blue sky.
In fairness, the seawater injection didn't begin until the reactors were already well off anybody's operating manual. In fact, the seawater injection was reported as the best option available at the time by world international experts.
Confusing things there were two injections of seawater: the injection into the pressure vessel was a likely a good move under the circumstances; the part I'm questioning is flooding the containment vessel, which is highly unusual. Why is that second move, which puts the system in a state it wasn't designed for, a better idea than following the documented plan: let the core dump, then optionally spray (but not flood) it with water?
It may be a good idea - but if so, why wasn't it part of the normal emergency procedures? I'm concerned that the answer may be that it was considered and rejected because of the risk of losing control of large volumes of contaminated water, or that an explosion inside the filled containment would be more likely to cause a breach due to hydraulic shock.
One of the big reasons why water is constantly re-applied to the reactors in Japan is because water does wonders to keep particulates out of the air.
So does a containment vessel. They were largely intact (as evidenced by high pressure) until the explosion inside the wetwell of #2. The others are still good to go.
Mind you, I'm glad to have an extra safety net as long as it's not making things worse. Unfortunately, I've not found any good in-depth analysis of these decisions. I'm sure someone's doing it, but it's not anywhere I can see it.
Good question. An answer was given in a special on the Fukushima accident on Japan's NHK World, on the one month anniversary of the quake. The trade off is to allow the current (comparatively) low leak off radioactivity in order to minimize the chances of a massive release of radioactivity (which I presume means on the scale of Chernobyl). The expert said they needed to keep cooling the reactors to prevent more fuel rods melting, causing the build up of more hydrogen. He said they are worried that another large hydrogen explosion could blow open a containment vessel causing a massive release of radioactivity.
Chernobyl's massive release was due to two main factors: 1) the steam explosion (and subsequently what was likely a small nuclear explosion) that blew the whole thing open; 2) the burning of the graphite moderator, whose smoke carried heavier radionuclides over long distances.
That's not the case here - with a BWR's water-moderation (not flammable), negative void coefficient (prevents steam explosions), and current state (shut down and unlikely to light off again), a meltdown just spews on the floor and sits there. The gaseous waste already got loose.
The hydrogen explosions were foreseeable and preventable - a dry meltdown doesn't generate hydrogen; having decided to melt down wet and generating hydrogen (which is no surprise - it's a known, documented problem), they should have vented to atmosphere instead of to the building. That would have caused some backlash because they'd be venting radiation directly out - but that radiation got out anyway and we now have a whole mess of exploded buildings.
Given that the radioactive water leaking out is giving them terrible PR and is also making the restoration of the cooling systems very difficult, I believe they are doing the right thing from an engineering perspective which is to try to minimize the worst case scenario even if doing so gives them awful PR now.
I'm worried that in the early stages of the meltdown they performed a risky nonstandard procedure hoping that it'd be adequate to keep things under control and prevent a giant PR problem... but the risky coverup didn't work, and now they're dealing with consequences that are much worse than if they'd just let it fail the way it was designed.
I've given them a lot of slack assuming that they're doing what they know is best, but from the first days of this event I've had the impression that they've deviated from the established sequence of containment strategies. I doubt seawater injection is listed in their operations manual.
I understand the cultural issue, but it's not a sufficient excuse when they are in charge of a nuclear reactor. If they can't overcome their shame *at least* during an emergency requiring international support, then perhaps they shouldn't have one.
Then ask yourself why would they do anything that wouldn't be normal for them to do?
They should follow a set of pre-established procedures that include adequate communication. I'd expect this to be required in licensing the plant; if it's not, it should be.
As I understand it, though, low-enriched uranium isn't much of a risk for re-criticality when dry. It requires a neutron moderator (water, in the case of a BWR) to reach a critical configuration. I'm not sure if that's an absolute - perhaps it'd be critical if formed into a sphere - but the "core on the floor" is supposed to be considerably subcritical.
Now of course I admit that Excel is probably not as flexible as R. However, unless your job is to produce stunning, tailor-made graphs, a spreadsheet application will deliver results a lot faster.
R is not a graphing language. It's a statistics language. If you just want to plot your sales growth by quarter, sure, a spreadsheet is much more convenient. But professional-quality graphs aren't the only (or even the primary) reason for R.
R has an enormous library of very well refined statistics functions. Spreadsheets are not designed to handle hundreds of thousands of data points, cross-correlations, advanced data transforms, and all kinds of analysis that spreadsheets don't (and shouldn't) have.
...that water they have to keep pumping in keeps coming out bringing highly radioactive particles from the damaged fuels rods along...
This is the part that I've never understood. Why are they pumping the containment full of water? The point of a containment structure is that when Shit Goes Wrong, and it most certainly has, you can stand back and watch while the water boils off, the core melts, and ends up as a puddle on the concrete floor. It'll slowly burn through for a while, but it'll eventually stop. You then wait a few decades and clean up the mess.
They've failed in keeping the fuel from melting, so the gaseous radionuclides have already escaped. The plan at this point (and in my opinion, since about day two or three) should have been to let the design do what it's supposed to do. Are there technical reasons that all the water pumping is beneficial, or was it just politics, trying to prevent an "OMFG meltdown" when in reality the contaminated water is actually worse?
Voltage != Current. Voltage * Current = Energy. Total energy kills, due to reasons you stated.
To be pedantic, Voltage * Current = Power. Energy is Voltage * Current * Time. Regardless, I understand the point you're making: that current alone isn't a good measure of damage being done.
Here's the thing: Watts aren't a good way to measure what's being done to your body either. Since your body's resistance is fairly even inside: Current = Voltage / path length - the voltage gradient - which determines how many nerves will fire; and Current ** 2 = Power / path length - the power density - which determines how much you get burned. Of course there are a slew of factors I'm ignoring (your heart is more vulnerable than your leg; people in poor health can't take as much; and many more), but to a first approximation, current is the main variable that determines if you're in danger.
To look at it another way, 500mA down your whole arm dissipates more power and is damaging more tissue than 500mA across your fingertip... But my goal is to cause *no* damage, and current is a good indicator: 2mA won't cause burns through any path length; 500mA will mess you up whether it's over an inch or head to toe.
Voltage is potential whether the circuit is open or closed.
Correct, but I think you misunderstand the point about constant-current power supplies. A CCPS will increase its voltage until it achieves its set current. In an open circuit, that theoretically means infinity volts. In reality, a CCPS will have a maximum open-circuit voltage. You want a resistor of large enough value that when contact is made (or the voltage rises high enough to cause dielectric breakdown in your skin) that it'll dump the stored charge into you gently rather than arcing through you.
Could I have done exactly the same thing over a leased line somewhere between 1970 and 1985
That's not the right question. The test you need is: "Did anyone think of doing this over a leased line before now?" If no one thought of doing it before, and it's a nontrivial invention, it's most certainly patentable.
In this case, remote version history has plenty of examples of people thinking of this a long time ago: AMANDA just off the top of my head. I haven't read the patent to see if they claim something narrower that people hadn't thought of before.
Current is what will kill you, not voltage. Greater current causes greater voltage gradients inside of you, which will disrupt neurons more and increase power dissipation, burning things. Higher voltage is more dangerous because it increases current. Decreasing resistance also increases the current. Your skin is a pretty good insulator, but if you poke wires in deep enough that they reach the wet bits that protection is lost and the current will spike way up.
Here are some measurements on myself: 2.5M ohm Probes pinched in my fingers of left and right hands 500K ohm After licking fingertips 1M ohm Across my scalp 50K ohm Across my tongue
A 9V battery isn't going to come anywhere near 2mA with any of those contacts. For anyone who wants to try wiring up their brain, though, I suggest putting a 4.7K resistor in series with the 9V battery - the added resistance is insignificant next to your skin, but when you accidentally stab the electrodes straight through your skull and into your brain it'll limit the current to safe levels.
I also suggest that a 9V battery is worthless because of the resistance of your skin. If you want this to actually work you should use a much higher voltage (such as stepping that 9V up with an oscillator driving a transformer) and a much larger value of protection resistor (Ohm's Law), to better approximate a constant-current source. A constant-current power supply is even better. Note that above 300V you're running a risk of dielectric breakdown in your skin - IE, the resistance suddenly drops - and the current will surge. You'd better have a protection resistor that can save you from the highest possible open circuit voltage of whatever power supply you use.
Start low and work your way up. 1mA is enough to put you in v-fib if it's direct to the heart. Of course, anything applied to the skin will spread out considerably before it reaches your heart - it's more like 50mA to the skin directly across the chest to induce v-fib - but it's best to have a healthy respect for what you're doing.
Well, I had two points: the first paragraph is pretty much what you are saying: without specifics, that once you try to scale things up from the initial experiment stage you start encountering new factors that screw it all up. I agree, and that's why I don't fault google for backing solar - it's a pretty safe bet, even though the potential payoff is a lot smaller than fusion.
My second point was that the Polywell looks workable at a much smaller scale than magnetic containment designs. That doesn't mean it's necessarily more likely to succeed, but that the cost to try is much lower - ITER is in the $5B range, whereas it'd only take $5M to push Polywell through it's next round or two of development, and if those go well another $50M would take them a long way toward having a workable machine. Flipside a $5M/2y fizzle hurts a lot less than a $5B/30y fizzle.
I'm also just tickled by the idea of a Farnsworth fusor evolving into a viable energy source.:)
I hate it when they try to hype an old service with a new name, but I don't think that's the case here. Hosted storage and dropping your infrastructure into VPSes is a fairly recent idea, and the "cloud" term didn't come along much later. It's a new term that's reasonably descriptive of a new thing. Do you object to the trendy marketing term "cell phone" even though they're really just multi-base multiplexed radiotelephones?
Who do you think is being upsold? I can't envision a buyer who didn't really want a colo server who's going to get screwed because they were lured in by the term "cloud".
Fusion's had a lot of investment and unbelievable numbers of failed designs. I can understand pursuing a known working technology that's deep into development instead of one that's still in the research stage.
That said, the Polywell's delightfully simple, and at a first pass, plausibly workable. The simplicity is the real reason it's really appealing - the investment required to give it a good shake is minimal, and it has relatively few ways to go wrong. Thanks for the link - I'm definitely going to be following this one.
I understand your point, but "selective killing" is also known as "natural selection". As long as you don't deploy too much too quickly, they'll adapt. It makes sense to keep an eye out for some species that is unusually vulnerable and needs our active protection, but unless there's an actual credible threat, we ought not to hold up this technology dreaming up "what ifs" when the ones we're using now *are* doing massive damage.
It's a data center that someone else runs for you. Big deal.
Said like someone who's never had to deal with a data center before. In the small to mid-size business range, running a data center seriously sucks. It involves at least one of: talent and capital that small businesses just don't have; renting a cage from someone who's charging an arm and a leg for mediocre service; or simply building a poor one in what used to be a conference room and dealing with crap power, cooling, cabling, etc, because those hassles are still cheaper than either of the two prior options.
Hassle-free sign up for what you need as you need it with no lock-in is a SMB's dream come true. I don't think it's going away.
Sorry, whatever you try to spin it people are not going to die from concentrated solar power, and please give me a break about plumbers falling from the roofs while installing solar panels, that would be laughable if not sad.
Large solar plants are like any industrial operation: constructing large towers in the desert will kill a few people from heat stroke, falling, mirrors falling on them, and other minor risks. It's a legitimate number of people who die installing infrastructure. Why should they be excluded? Because they only happen one at a time?
The number who die from solar is very small, and I consider it a perfectly acceptable risk.
That's exactly how I feel about nuclear power: the risk is even lower than what you call laughable and sad.
I'd be willing to hear arguments about price but then please take into account all costs, including externalities, risks, insurance, waste, pollution, etc. I'd be genuinely interested in true figures about costs, without political spin.
I'm game, though I suggest excluding either insurance or financial risks, which are largely redundant. I'll be glad to do a few hours of research if you'll do it too - pick your favorite energy source and do a fair job adding up the costs. If it's wind make sure you account for some other power source that can fill in on calm days and the costs of transmission lines (since wind isn't widely available). If it's solar you need to budget for extra capacity for cloudy days and transmission costs. For anything that burns, account for dealing with the CO2. Try to do a fair job looking at it as a global problem - solar won't work for Finland. I'm not saying you have to come up with a universal energy plan; just acknowledge the shortcomings and pick something that can feasibly provide 25% of the world's energy needs. No speculating on future technology - pick from the very best of what's commercially available right now.
I'll do nuclear. I'll account for waste handling, environmental damage from mining fuel, expensive cleanup projects from meltdowns, and wasted land from contamination. Let me know anything else you want that will help make the comparison as fair as possible. I won't speculate on future technology either (Generation IV designs) - but I WILL base my numbers on the very best of what's available right now (Gen III - Gen III+ designs). I'll include the costs of decommissioning all the 2nd generation 1950s and 1960s plants that should have been shut down a decade or two ago.
I'm not sure how to handle nuclear proliferation - while many plant designs can be used to produce weapons-grade plutonium, the bad guys can simply build small military reactors to do it anyway. Being able to piggyback a weapons program onto civilian reactors just makes it somewhat cheaper.
My gut instinct is nuclear will be quite competitive, but I'm happy to be proven wrong. Are you up for it?:)
Hydro's good in NZ, but it can't meet demands everywhere - there just aren't enough large rivers running through conveniently damable canyons. Even in NZ, you're apparently falling off the program: "The plan in 1959 to raise the level of Lake Manapouri to increase hydro-electric generation met with resistance, and the Save Manapouri Campaign became a milestone in environmental awareness. Later hydro schemes (such as the Clyde Dam) were also controversial, and in recent decades coal and gas-fired thermal stations have been approved in New Zealand, while renewable energy schemes in general have been turned down because of the unpopular effect they have on the environment." -- http://en.wikipedia.org/wiki/Hydroelectric_power_in_New_Zealand
When our power sources "have an accident", perhaps they break down, and other stations pick up slack. Absolute worst case, power goes out in certain regions, big deal.
Big-scale engineering comes with risks. Dam failures:
So in a disaster in Japan that's killed tens of thousands - including quite a few in burning oil refineries - how many are dead from nuke power?
I'm not saying hydro's universally a bad idea, but even in areas where it does work it has substantial risks that you're ignoring.
Anyway, if you'd care to look at the risks objectively, here's a great chart of deaths per TW/h:
161 Coal - world average (26% of world energy, 50% of electricity) 278 Coal - China
15 Coal - USA
36 Oil (36% of world energy)
4 Natural Gas (21% of world energy)
12 Biofuel/Biomass
12 Peat
0.44 Solar (rooftop) (less than 0.1% of world energy)
0.15 Wind (less than 1% of world energy)
0.10 Hydro (europe death rate, 2.2% of world energy)
1.4 Hydro - world including Banqiao) (about 2500 TWh/yr and 171,000 Banqiao dead)
0.04 Nuclear (5.9% of world energy)
I'm all for wind, solar and hydro, but they're limited in quantity and geography, so we have to find something else to fill the gap. All the other options but one involve burning stuff at considerable cost to human life and the environment. For all its faults, nuclear just isn't that bad compared to all the other alternatives.
If one person from a non Nuclear country is harmed, thats one too many. *Anyone* harmed by this accident is someone too many.
Too many for what? It's not too many for nuclear power to *still* be the safest power source available. That's not to say we shouldn't continue trying to improve safety, but no matter what we do, people will die for energy. Coal kills lots of miners. Any form of HC causes widespread planetary destruction. Don't get me started on dam failures.
The only energy policy to prevent anyone from being harmed is to drop our electrical requirements to zero. That would cause a great increase in deaths from other causes - pre-industrial society wasn't exactly a safe life - but hey, at least they wouldn't be from scary nuclear power, right?
I agree with most of your first three paragraphs, but the second two dealing with the UAV photos I have to rebut.
Note the object sitting on both pipes.... guess it's width. Now look at he edge of the item. Care to guess how thick it is?... Under the dust layer it is clearly Yellow. Care to guess what it is and where it came from?
My origin is at the upper left. The object you're describing is at X:20%, Y60%. Note the thickness of the cut off pipe at X:70%, Y:30%. This is thin walled stuff. In other photos you can see the twin pipes are at the same level as that raised section, and similarly supported. The containment vessel is very thick and heavy. If that was the dome or another section of the containment flung from #3, it would have destroyed or at least damaged the pipe. My analysis: It's just a chunk of wall, similar to the chunks laying in front of #4.
... look next to the reactor 3 building where the pile of plumbing is lying next to the building. All that plumbing is uniform is size. I'm thinking that is scattered fuel rods from the cooling pond.
http://cryptome.org/eyeball/daiichi-npp/pict6.jpg - Are you referring to the stuff to the lower-left of the steam, and similar-sized stuff strewn across the top of the turbine hall? I think it's too big to be fuel rods, and too small and mangled to be fuel assemblies. It looks like structural steel from the building.
Lastly, if the stuff flung up in the explosion was fuel rods or containment chunks, we'd be seeing much higher radiation levels in the vicinity of the #3 building. Instead the high levels are centered around #2, where there *was* an explosion inside containment that caused a breach.
The problem with terror alerts is that they are vague.
Even if they gave us more specifics, there's no associated reasonable response to them.
They look sort of like DEFCON levels, but they're not. DEFCON levels signal that it's time for specific groups to perform certain actions. At DEFCON 4 intelligence guys are activated and base security goes up. At DEFCON 3 you're organizing the troops and starting to make active preparations for war. And so on.
The terror alerts are useless. Let's say they give one that's pretty specific: San Jose is now at Red for this week. Does the SJPD set up inspection checkpoints for trucks? Does ATC divert all flights from SJC to SFO? Do they deploy guards to protect the reservoirs from poisoning? Are ANY specific actions indicated? If not, then all you're going to have is random fucknuts getting scared when they see a group of more than 3 of any ethnic minority.
The dumbest display I ever saw of this was a sign at a colo data center we used indicating that we were at level Orange. They weren't doing anything differently (just the same marginally acceptable security procedures as always). But they're a security checkpoint, and terror alerts have something to do with security, so they put up a sign.
Negative. This is not that system. There are a number of cars that let you adjust the shock absorbers on the fly: at the entry level, this involves servos adjusting the shock valving; at the high end (such as the F599) they use electromagnets to adjust the viscosity of the fluid in the shocks, which can be done much faster.
This system is altogether different: there is no shock absorber. They have a linear motor in its place. This gives advanced capabilities that adjustable shocks cannot.
For instance, say you turn hard left. The car wants to lean right. Soft springs are good for comfort, but allow the car to tilt more. This system lets you use soft springs, and then actively counter the body roll by pushing on one side and pulling on the other. The net result is you have the best of both worlds: the smooth ride of a luxury car's soft springs combined with the fast response and stiff anti-roll characteristics of a sports car.
You need a very strong linear actuator to make a meaningful improvement, but those are expensive and require a hefty electrical system to power them, further increasing the price. Bose did some fantastic demos of these some years back, but I don't think they managed to get any manufacturers interested, probably due to cost. Hopefully these guys have improved in that regard.
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By "leaner fuel mixtures" they're not saying that you have to change the gasoline itself - you just inject less of it.
Even without running leaner, yes, this can improve efficiency: it can ignite the fuel closer to the center of the combustion chamber, which makes for a better burn. It might also ignite a longer path of the fuel, resulting in a quicker burn without detonation. You retard timing a little bit, and then do a quick burn to bring up pressure right at the best moment. This is already done on some current engines by using more than one spark plug per cylinder.
I agree that a prompt criticality is essentially impossible after a meltdown, but at the initial moment of failure in Chernobyl, much higher reactivity was easily attainable.
In an operating reactor the safety margin of reactivity is only about 0.6% between the threshold of delayed-critical and prompt-critical. The fuel alone is incapable of going prompt-critical (or even delayed-critical, in most cases) - but with enough neutron moderator present, you can get past that gap. One of the flaws of the RBMK - an insane design - is it has a long section of graphite (a neutron moderator) at the tip of each control rod to increase reactivity in certain regions when they're fully withdrawn. That's supposed to be done in a few regions at a time.
When Chernobyl popped, they had withdrawn nearly all of the control rods. At the end of the experiment, they SCRAMmed the reactor, and all the control rods descended together. It blew as the graphite sections were aligned with the bottom of the core. Thus, the bottom of the core - already primed from the previous activities - was in an extremely over-reactive configuration. The first explosion happened, causing three important things: 1, the rod channels shattered, so all that extra graphite stayed in the core; 2, a total coolant loss (which raised the reactivity considerably); 3, the fuel assemblies broke up, allowing the configuration to change further (likely with very high reactivity at some moments). It's entirely possible that those effects combined to reach a prompt-critical configuration briefly.
Ask your nuclear engineer friend for a clarification - I'll bet he was talking about a molten mess of fuel, not about an operating reactor that was placed into a *very* over-reactive configuration.
No, a nuclear explosion doesn't mean you get a mushroom cloud. Mushroom clouds occur from *large* explosions. As I said, the Chernobyl explosion was only around 10t - comparable to a MOAB but a pathetic fizzle compared to a nuclear bomb. An explosion that size DID happen - it's just a question of how. A large hydrogen explosion is also likely.
I guess you didn't bother to read the links I posted. The study wasn't based on modeling the explosion - it was based on analyzing the Xe-133 present after the meltdown. The ratios of isotopes give a picture of what processes were occurring. It's hardy conclusive, but it's a good indicator.
But weren't last few generations of reactors also supposed to be literally failsafe? Never in a thousand years would we see the types of accidents we've had five or so of in the last forty years? We were assured that by people who literally swore on their childrens' lives that it would be perfectly safe.
Who swore? Gen I BWRs were built to an standard of industrial safety that was considered adequate in the 1960s, when they were designed. "Adequately safe" never meant "perfectly safe" - it meant that the risk-reward profile was worthwhile.
I'm quite confident that if the Fukushima reactors had been replaced with ABWRs, ESBWRs, ACR-1000s, or AP-1000s, we would not be having the present crisis. In particular, all of these designs are capable of maintaining cooling even in a station blackout. This is not a case of hindsight being 20/20 - the problem of station blackouts was foreseen and mitigated, as were many others.
Part of the great increase in safety is because they're considerably simplified from GenII designs. Because of this they are more likely to survive (or simply not be vulnerable to) other failures that we haven't anticipated.
Modern nuclear safety standards are now much better than current industrial safety standards - which includes all other methods of large scale power generation commercially available at present.
...which of course are going to be "lighter" and "cheaper" because they'll have smaller containments...
This simply isn't true. Careful engineering is allowing some modest reduction in containment size in some of the latest designs compared to the 1980s era, but even the smallest ones are an order of magnitude larger than the 1960s era containments.
Chernobyl did not have a "small nuclear explosion". Period.
RBMKs (as configured at the time) had a very large positive void coefficient; after the steam explosion depressurized the vessel, the coolant was boiling like mad with essentially no liquid water inside the fuel assemblies. Combined with all the extra graphite from the control rod tips which were in exactly the wrong place, a prompt criticality was very possible as things were settling inside.
"A second, more powerful explosion occurred about two or three seconds after the first; evidence indicates that the second explosion resulted from a nuclear excursion." The citation is over here.
Since the assembly was slow (compared to a weapon) the criticality ended quickly as it blew itself apart. The yield was on the order of 10t (not low Kt, as expected in an unboosted uranium weapon). There are other theories for the second explosion, but this one has the best case made for it.
Anyway, I wasn't suggesting that it was the explosion itself that carried particles long distances (though it did make quite a mess locally); it just blew the thing wide open so when the fires started the only thing covering them was the blue sky.
In fairness, the seawater injection didn't begin until the reactors were already well off anybody's operating manual. In fact, the seawater injection was reported as the best option available at the time by world international experts.
Confusing things there were two injections of seawater: the injection into the pressure vessel was a likely a good move under the circumstances; the part I'm questioning is flooding the containment vessel, which is highly unusual. Why is that second move, which puts the system in a state it wasn't designed for, a better idea than following the documented plan: let the core dump, then optionally spray (but not flood) it with water?
It may be a good idea - but if so, why wasn't it part of the normal emergency procedures? I'm concerned that the answer may be that it was considered and rejected because of the risk of losing control of large volumes of contaminated water, or that an explosion inside the filled containment would be more likely to cause a breach due to hydraulic shock.
One of the big reasons why water is constantly re-applied to the reactors in Japan is because water does wonders to keep particulates out of the air.
So does a containment vessel. They were largely intact (as evidenced by high pressure) until the explosion inside the wetwell of #2. The others are still good to go.
Mind you, I'm glad to have an extra safety net as long as it's not making things worse. Unfortunately, I've not found any good in-depth analysis of these decisions. I'm sure someone's doing it, but it's not anywhere I can see it.
Good question. An answer was given in a special on the Fukushima accident on Japan's NHK World, on the one month anniversary of the quake. The trade off is to allow the current (comparatively) low leak off radioactivity in order to minimize the chances of a massive release of radioactivity (which I presume means on the scale of Chernobyl). The expert said they needed to keep cooling the reactors to prevent more fuel rods melting, causing the build up of more hydrogen. He said they are worried that another large hydrogen explosion could blow open a containment vessel causing a massive release of radioactivity.
Chernobyl's massive release was due to two main factors: 1) the steam explosion (and subsequently what was likely a small nuclear explosion) that blew the whole thing open; 2) the burning of the graphite moderator, whose smoke carried heavier radionuclides over long distances.
That's not the case here - with a BWR's water-moderation (not flammable), negative void coefficient (prevents steam explosions), and current state (shut down and unlikely to light off again), a meltdown just spews on the floor and sits there. The gaseous waste already got loose.
The hydrogen explosions were foreseeable and preventable - a dry meltdown doesn't generate hydrogen; having decided to melt down wet and generating hydrogen (which is no surprise - it's a known, documented problem), they should have vented to atmosphere instead of to the building. That would have caused some backlash because they'd be venting radiation directly out - but that radiation got out anyway and we now have a whole mess of exploded buildings.
Given that the radioactive water leaking out is giving them terrible PR and is also making the restoration of the cooling systems very difficult, I believe they are doing the right thing from an engineering perspective which is to try to minimize the worst case scenario even if doing so gives them awful PR now.
I'm worried that in the early stages of the meltdown they performed a risky nonstandard procedure hoping that it'd be adequate to keep things under control and prevent a giant PR problem... but the risky coverup didn't work, and now they're dealing with consequences that are much worse than if they'd just let it fail the way it was designed.
I've given them a lot of slack assuming that they're doing what they know is best, but from the first days of this event I've had the impression that they've deviated from the established sequence of containment strategies. I doubt seawater injection is listed in their operations manual.
I understand the cultural issue, but it's not a sufficient excuse when they are in charge of a nuclear reactor. If they can't overcome their shame *at least* during an emergency requiring international support, then perhaps they shouldn't have one.
Then ask yourself why would they do anything that wouldn't be normal for them to do?
They should follow a set of pre-established procedures that include adequate communication. I'd expect this to be required in licensing the plant; if it's not, it should be.
As I understand it, though, low-enriched uranium isn't much of a risk for re-criticality when dry. It requires a neutron moderator (water, in the case of a BWR) to reach a critical configuration. I'm not sure if that's an absolute - perhaps it'd be critical if formed into a sphere - but the "core on the floor" is supposed to be considerably subcritical.
Or is there less margin than I think?
Now of course I admit that Excel is probably not as flexible as R. However, unless your job is to produce stunning, tailor-made graphs, a spreadsheet application will deliver results a lot faster.
R is not a graphing language. It's a statistics language. If you just want to plot your sales growth by quarter, sure, a spreadsheet is much more convenient. But professional-quality graphs aren't the only (or even the primary) reason for R.
R has an enormous library of very well refined statistics functions. Spreadsheets are not designed to handle hundreds of thousands of data points, cross-correlations, advanced data transforms, and all kinds of analysis that spreadsheets don't (and shouldn't) have.
...that water they have to keep pumping in keeps coming out bringing highly radioactive particles from the damaged fuels rods along...
This is the part that I've never understood. Why are they pumping the containment full of water? The point of a containment structure is that when Shit Goes Wrong, and it most certainly has, you can stand back and watch while the water boils off, the core melts, and ends up as a puddle on the concrete floor. It'll slowly burn through for a while, but it'll eventually stop. You then wait a few decades and clean up the mess.
They've failed in keeping the fuel from melting, so the gaseous radionuclides have already escaped. The plan at this point (and in my opinion, since about day two or three) should have been to let the design do what it's supposed to do. Are there technical reasons that all the water pumping is beneficial, or was it just politics, trying to prevent an "OMFG meltdown" when in reality the contaminated water is actually worse?
Voltage != Current. Voltage * Current = Energy. Total energy kills, due to reasons you stated.
To be pedantic, Voltage * Current = Power. Energy is Voltage * Current * Time. Regardless, I understand the point you're making: that current alone isn't a good measure of damage being done.
Here's the thing: Watts aren't a good way to measure what's being done to your body either. Since your body's resistance is fairly even inside: Current = Voltage / path length - the voltage gradient - which determines how many nerves will fire; and Current ** 2 = Power / path length - the power density - which determines how much you get burned. Of course there are a slew of factors I'm ignoring (your heart is more vulnerable than your leg; people in poor health can't take as much; and many more), but to a first approximation, current is the main variable that determines if you're in danger.
To look at it another way, 500mA down your whole arm dissipates more power and is damaging more tissue than 500mA across your fingertip... But my goal is to cause *no* damage, and current is a good indicator: 2mA won't cause burns through any path length; 500mA will mess you up whether it's over an inch or head to toe.
Voltage is potential whether the circuit is open or closed.
Correct, but I think you misunderstand the point about constant-current power supplies. A CCPS will increase its voltage until it achieves its set current. In an open circuit, that theoretically means infinity volts. In reality, a CCPS will have a maximum open-circuit voltage. You want a resistor of large enough value that when contact is made (or the voltage rises high enough to cause dielectric breakdown in your skin) that it'll dump the stored charge into you gently rather than arcing through you.
Fortunately I have a thick skull. Wait...
Could I have done exactly the same thing over a leased line somewhere between 1970 and 1985
That's not the right question. The test you need is: "Did anyone think of doing this over a leased line before now?" If no one thought of doing it before, and it's a nontrivial invention, it's most certainly patentable.
In this case, remote version history has plenty of examples of people thinking of this a long time ago: AMANDA just off the top of my head. I haven't read the patent to see if they claim something narrower that people hadn't thought of before.
Having recognized this, why did you still post it to the front page?
A quick lesson in electrical safety:
Current is what will kill you, not voltage. Greater current causes greater voltage gradients inside of you, which will disrupt neurons more and increase power dissipation, burning things. Higher voltage is more dangerous because it increases current. Decreasing resistance also increases the current. Your skin is a pretty good insulator, but if you poke wires in deep enough that they reach the wet bits that protection is lost and the current will spike way up.
Here are some measurements on myself:
2.5M ohm Probes pinched in my fingers of left and right hands
500K ohm After licking fingertips
1M ohm Across my scalp
50K ohm Across my tongue
A 9V battery isn't going to come anywhere near 2mA with any of those contacts. For anyone who wants to try wiring up their brain, though, I suggest putting a 4.7K resistor in series with the 9V battery - the added resistance is insignificant next to your skin, but when you accidentally stab the electrodes straight through your skull and into your brain it'll limit the current to safe levels.
I also suggest that a 9V battery is worthless because of the resistance of your skin. If you want this to actually work you should use a much higher voltage (such as stepping that 9V up with an oscillator driving a transformer) and a much larger value of protection resistor (Ohm's Law), to better approximate a constant-current source. A constant-current power supply is even better. Note that above 300V you're running a risk of dielectric breakdown in your skin - IE, the resistance suddenly drops - and the current will surge. You'd better have a protection resistor that can save you from the highest possible open circuit voltage of whatever power supply you use.
Start low and work your way up. 1mA is enough to put you in v-fib if it's direct to the heart. Of course, anything applied to the skin will spread out considerably before it reaches your heart - it's more like 50mA to the skin directly across the chest to induce v-fib - but it's best to have a healthy respect for what you're doing.
Well, I had two points: the first paragraph is pretty much what you are saying: without specifics, that once you try to scale things up from the initial experiment stage you start encountering new factors that screw it all up. I agree, and that's why I don't fault google for backing solar - it's a pretty safe bet, even though the potential payoff is a lot smaller than fusion.
My second point was that the Polywell looks workable at a much smaller scale than magnetic containment designs. That doesn't mean it's necessarily more likely to succeed, but that the cost to try is much lower - ITER is in the $5B range, whereas it'd only take $5M to push Polywell through it's next round or two of development, and if those go well another $50M would take them a long way toward having a workable machine. Flipside a $5M/2y fizzle hurts a lot less than a $5B/30y fizzle.
I'm also just tickled by the idea of a Farnsworth fusor evolving into a viable energy source. :)
I hate it when they try to hype an old service with a new name, but I don't think that's the case here. Hosted storage and dropping your infrastructure into VPSes is a fairly recent idea, and the "cloud" term didn't come along much later. It's a new term that's reasonably descriptive of a new thing. Do you object to the trendy marketing term "cell phone" even though they're really just multi-base multiplexed radiotelephones?
Who do you think is being upsold? I can't envision a buyer who didn't really want a colo server who's going to get screwed because they were lured in by the term "cloud".
Fusion's had a lot of investment and unbelievable numbers of failed designs. I can understand pursuing a known working technology that's deep into development instead of one that's still in the research stage.
That said, the Polywell's delightfully simple, and at a first pass, plausibly workable. The simplicity is the real reason it's really appealing - the investment required to give it a good shake is minimal, and it has relatively few ways to go wrong. Thanks for the link - I'm definitely going to be following this one.
I understand your point, but "selective killing" is also known as "natural selection". As long as you don't deploy too much too quickly, they'll adapt. It makes sense to keep an eye out for some species that is unusually vulnerable and needs our active protection, but unless there's an actual credible threat, we ought not to hold up this technology dreaming up "what ifs" when the ones we're using now *are* doing massive damage.
It's a data center that someone else runs for you. Big deal.
Said like someone who's never had to deal with a data center before. In the small to mid-size business range, running a data center seriously sucks. It involves at least one of: talent and capital that small businesses just don't have; renting a cage from someone who's charging an arm and a leg for mediocre service; or simply building a poor one in what used to be a conference room and dealing with crap power, cooling, cabling, etc, because those hassles are still cheaper than either of the two prior options.
Hassle-free sign up for what you need as you need it with no lock-in is a SMB's dream come true. I don't think it's going away.
Sorry, whatever you try to spin it people are not going to die from concentrated solar power, and please give me a break about plumbers falling from the roofs while installing solar panels, that would be laughable if not sad.
Large solar plants are like any industrial operation: constructing large towers in the desert will kill a few people from heat stroke, falling, mirrors falling on them, and other minor risks. It's a legitimate number of people who die installing infrastructure. Why should they be excluded? Because they only happen one at a time?
The number who die from solar is very small, and I consider it a perfectly acceptable risk.
That's exactly how I feel about nuclear power: the risk is even lower than what you call laughable and sad.
I'd be willing to hear arguments about price but then please take into account all costs, including externalities, risks, insurance, waste, pollution, etc. I'd be genuinely interested in true figures about costs, without political spin.
I'm game, though I suggest excluding either insurance or financial risks, which are largely redundant. I'll be glad to do a few hours of research if you'll do it too - pick your favorite energy source and do a fair job adding up the costs. If it's wind make sure you account for some other power source that can fill in on calm days and the costs of transmission lines (since wind isn't widely available). If it's solar you need to budget for extra capacity for cloudy days and transmission costs. For anything that burns, account for dealing with the CO2. Try to do a fair job looking at it as a global problem - solar won't work for Finland. I'm not saying you have to come up with a universal energy plan; just acknowledge the shortcomings and pick something that can feasibly provide 25% of the world's energy needs. No speculating on future technology - pick from the very best of what's commercially available right now.
I'll do nuclear. I'll account for waste handling, environmental damage from mining fuel, expensive cleanup projects from meltdowns, and wasted land from contamination. Let me know anything else you want that will help make the comparison as fair as possible. I won't speculate on future technology either (Generation IV designs) - but I WILL base my numbers on the very best of what's available right now (Gen III - Gen III+ designs). I'll include the costs of decommissioning all the 2nd generation 1950s and 1960s plants that should have been shut down a decade or two ago.
I'm not sure how to handle nuclear proliferation - while many plant designs can be used to produce weapons-grade plutonium, the bad guys can simply build small military reactors to do it anyway. Being able to piggyback a weapons program onto civilian reactors just makes it somewhat cheaper.
My gut instinct is nuclear will be quite competitive, but I'm happy to be proven wrong. Are you up for it? :)
Hydro's good in NZ, but it can't meet demands everywhere - there just aren't enough large rivers running through conveniently damable canyons. Even in NZ, you're apparently falling off the program: "The plan in 1959 to raise the level of Lake Manapouri to increase hydro-electric generation met with resistance, and the Save Manapouri Campaign became a milestone in environmental awareness. Later hydro schemes (such as the Clyde Dam) were also controversial, and in recent decades coal and gas-fired thermal stations have been approved in New Zealand, while renewable energy schemes in general have been turned down because of the unpopular effect they have on the environment." -- http://en.wikipedia.org/wiki/Hydroelectric_power_in_New_Zealand
When our power sources "have an accident", perhaps they break down, and other stations pick up slack. Absolute worst case, power goes out in certain regions, big deal.
Big-scale engineering comes with risks. Dam failures:
http://en.wikipedia.org/wiki/Banqiao_Dam - 171,000 dead, 11 million homeless.
http://en.wikipedia.org/wiki/Situ_Gintung - 100+ dead
http://en.wikipedia.org/wiki/Shakidor_Dam - 70+ dead
http://en.wikipedia.org/wiki/Gusau_Dam - 40 dead, 500 homes destroyed
http://en.wikipedia.org/wiki/Val_di_Stava_Dam_collapse - 268 dead
Also, aside from the body counts: http://en.wikipedia.org/wiki/Environmental_impacts_of_dams
So in a disaster in Japan that's killed tens of thousands - including quite a few in burning oil refineries - how many are dead from nuke power?
I'm not saying hydro's universally a bad idea, but even in areas where it does work it has substantial risks that you're ignoring.
Anyway, if you'd care to look at the risks objectively, here's a great chart of deaths per TW/h:
161 Coal - world average (26% of world energy, 50% of electricity)
278 Coal - China
15 Coal - USA
36 Oil (36% of world energy)
4 Natural Gas (21% of world energy)
12 Biofuel/Biomass
12 Peat
0.44 Solar (rooftop) (less than 0.1% of world energy)
0.15 Wind (less than 1% of world energy)
0.10 Hydro (europe death rate, 2.2% of world energy)
1.4 Hydro - world including Banqiao) (about 2500 TWh/yr and 171,000 Banqiao dead)
0.04 Nuclear (5.9% of world energy)
(from http://nextbigfuture.com/2008/03/deaths-per-twh-for-all-energy-sources.html)
I'm all for wind, solar and hydro, but they're limited in quantity and geography, so we have to find something else to fill the gap. All the other options but one involve burning stuff at considerable cost to human life and the environment. For all its faults, nuclear just isn't that bad compared to all the other alternatives.
If one person from a non Nuclear country is harmed, thats one too many. *Anyone* harmed by this accident is someone too many.
Too many for what? It's not too many for nuclear power to *still* be the safest power source available. That's not to say we shouldn't continue trying to improve safety, but no matter what we do, people will die for energy. Coal kills lots of miners. Any form of HC causes widespread planetary destruction. Don't get me started on dam failures.
The only energy policy to prevent anyone from being harmed is to drop our electrical requirements to zero. That would cause a great increase in deaths from other causes - pre-industrial society wasn't exactly a safe life - but hey, at least they wouldn't be from scary nuclear power, right?
I agree with most of your first three paragraphs, but the second two dealing with the UAV photos I have to rebut.
Note the object sitting on both pipes. ... guess it's width. Now look at he edge of the item. Care to guess how thick it is? ... Under the dust layer it is clearly Yellow. Care to guess what it is and where it came from?
You're implying that it's part of the containment vessel. Let's look at a specific picture for comparison: http://cryptome.org/eyeball/daiichi-npp/pict10.jpg
My origin is at the upper left. The object you're describing is at X:20%, Y60%. Note the thickness of the cut off pipe at X:70%, Y:30%. This is thin walled stuff. In other photos you can see the twin pipes are at the same level as that raised section, and similarly supported. The containment vessel is very thick and heavy. If that was the dome or another section of the containment flung from #3, it would have destroyed or at least damaged the pipe. My analysis: It's just a chunk of wall, similar to the chunks laying in front of #4.
... look next to the reactor 3 building where the pile of plumbing is lying next to the building. All that plumbing is uniform is size. I'm thinking that is scattered fuel rods from the cooling pond.
http://cryptome.org/eyeball/daiichi-npp/pict6.jpg - Are you referring to the stuff to the lower-left of the steam, and similar-sized stuff strewn across the top of the turbine hall? I think it's too big to be fuel rods, and too small and mangled to be fuel assemblies. It looks like structural steel from the building.
Lastly, if the stuff flung up in the explosion was fuel rods or containment chunks, we'd be seeing much higher radiation levels in the vicinity of the #3 building. Instead the high levels are centered around #2, where there *was* an explosion inside containment that caused a breach.
The problem with terror alerts is that they are vague.
Even if they gave us more specifics, there's no associated reasonable response to them.
They look sort of like DEFCON levels, but they're not. DEFCON levels signal that it's time for specific groups to perform certain actions. At DEFCON 4 intelligence guys are activated and base security goes up. At DEFCON 3 you're organizing the troops and starting to make active preparations for war. And so on.
The terror alerts are useless. Let's say they give one that's pretty specific: San Jose is now at Red for this week. Does the SJPD set up inspection checkpoints for trucks? Does ATC divert all flights from SJC to SFO? Do they deploy guards to protect the reservoirs from poisoning? Are ANY specific actions indicated? If not, then all you're going to have is random fucknuts getting scared when they see a group of more than 3 of any ethnic minority.
The dumbest display I ever saw of this was a sign at a colo data center we used indicating that we were at level Orange. They weren't doing anything differently (just the same marginally acceptable security procedures as always). But they're a security checkpoint, and terror alerts have something to do with security, so they put up a sign.
Negative. This is not that system. There are a number of cars that let you adjust the shock absorbers on the fly: at the entry level, this involves servos adjusting the shock valving; at the high end (such as the F599) they use electromagnets to adjust the viscosity of the fluid in the shocks, which can be done much faster.
This system is altogether different: there is no shock absorber. They have a linear motor in its place. This gives advanced capabilities that adjustable shocks cannot.
For instance, say you turn hard left. The car wants to lean right. Soft springs are good for comfort, but allow the car to tilt more. This system lets you use soft springs, and then actively counter the body roll by pushing on one side and pulling on the other. The net result is you have the best of both worlds: the smooth ride of a luxury car's soft springs combined with the fast response and stiff anti-roll characteristics of a sports car.
You need a very strong linear actuator to make a meaningful improvement, but those are expensive and require a hefty electrical system to power them, further increasing the price. Bose did some fantastic demos of these some years back, but I don't think they managed to get any manufacturers interested, probably due to cost. Hopefully these guys have improved in that regard.