Posted by
Roblimo
on from the sometimes-you-get-burned-when-you-play-with-fire dept.
Cy Guy writes "I'm sure there will be many more stories on this soon, for now, here is the wire story." An update sent in by cheetah: "It appears that someone mixed about 6 times too much uranium into a fuel processing tank. For the latest info click Here"
Criticality in solutions of heavy isotopes
by
Anonymous Coward
·
· Score: 5
...is easier to achive than you think.
(Snarl, network here is on the fritz, apologies if this comes through multiple times - connection reset by peer before anything actually gets submitted, I'm assuming...)
Anyone working at a nuke plant, especially a fuel processing plant, knows this. This incident appears to have been caused by stupidity of truly mind-boggling proportions.
If you're ever working with heavy isotopes (i.e. fissionables) in solution, the water or other solvent in which the compounds are dissolved can act as a moderator, and the amount of uranium or other fissionable matter required for criticality drops precipitously.
I did a few summer terms at a research reactor at a university. This reactor was often used to create compounds for medical use as well as other research. Preventing this type of incident was discussed in one of the most heavily-underlined-and-boldfaced sections of text in the book.
Any time you have to work with heavy unstable isotopes in solution, it's imperative that you know exactly what you're dealing with. That means you need to know both the nuclear (cross-sectional) and the chemical properties of both solvent and solute, AND the shape of the container, AND the concentrations expected at any stage in the dissolution.
Those latter two are particularly counterintuitive - but are glaringly obvious in hindsight, as they're significant factors in the mean distance (i.e. free path) between particles of the heavy isotope in the solution, a key determinant in criticality.
To give an example of what can go wrong - take a beaker of water and drop in a spoonful of brown sugar. Pretend the sugar is fissionable.
At the start, you have a subcritical mass of brown sugar. Safe enough to hold in your hand. At the end, the sugar is distributed evenly enough through the water that even with the water's moderating effect, it's subcritical. Safe enough to work with.
Walk away from the beaker and come back in 5 minutes. Observe that there are regions in the beaker of varying concentrations. At least one of these concentrations will be the "right" concentration to minimize the mass required for criticality. If the volume of that region is large enough, it goes critical in that region and it's game over.
For an even better version of this game, imagine you can stir it quickly enough so that this is never a risk. Mix it in a baking pan, so that the liquid is never deeper than 1cm, and most of the neutrons fly out the top and bottom of the pan. Give it to your friend, who pours it into one of those nice flasks with the spherical bottoms. The spherical shape allows many more neutrons to be absorbed. Your last thought is that "Safe enough to work with" only means "safe enough to work with in this container". Game over.
Or just carelessly leave the pan under the fume hood over the weekend. Or toss it in the freezer, and discover that as it freezes, the capacity to hold the material in solution changes, and some of it precipitates out. In either case, don't expect to get any work done on Monday morning, though.
Of course, now that I've gone through the hard ways to have this accident (about which anyone working in this environment would still know), putting seven times as much solute in the solution would also be a good way to screw it up.
Scary thought: If they could see the Cerenkov radiation - and weren't looking at the tank - it means the radiation flux through the fluid in the eyeball was high enough to cause a visible blue glow. That's a lot of radiation.
Remember all those "how to build your own atomic bomb" plans, that all worked out to "this won't give you a nuclear detonation, but it'll make one unholy hell of mess"?
The Japanese have just become the test case. While we're not talking about levelling cities or nuclear explosive yield, in terms of the physics involved - an uncontrolled chain reaction in a critical mass - the Japanese have arguably just nuked themselves, in the same sense that the Americans nuked them twice earlier this century.
It's a banner week for Darwinian Stupidity in the sciences, folks. First we lose a $125M space probe because two engineering teams didn't know the difference between metric and Imperial measure, and then a couple of Japanese fuel processing guys manage to top our blunder by accidentally building and activating something that's the fundamental equivalent to the core of an atomic bomb.
Slashdot Mirror
(Snarl, network here is on the fritz, apologies if this comes through multiple times - connection reset by peer before anything actually gets submitted, I'm assuming...)
Anyone working at a nuke plant, especially a fuel processing plant, knows this. This incident appears to have been caused by stupidity of truly mind-boggling proportions.
If you're ever working with heavy isotopes (i.e. fissionables) in solution, the water or other solvent in which the compounds are dissolved can act as a moderator, and the amount of uranium or other fissionable matter required for criticality drops precipitously.
I did a few summer terms at a research reactor at a university. This reactor was often used to create compounds for medical use as well as other research. Preventing this type of incident was discussed in one of the most heavily-underlined-and-boldfaced sections of text in the book.
Any time you have to work with heavy unstable isotopes in solution, it's imperative that you know exactly what you're dealing with. That means you need to know both the nuclear (cross-sectional) and the chemical properties of both solvent and solute, AND the shape of the container, AND the concentrations expected at any stage in the dissolution.
Those latter two are particularly counterintuitive - but are glaringly obvious in hindsight, as they're significant factors in the mean distance (i.e. free path) between particles of the heavy isotope in the solution, a key determinant in criticality.
To give an example of what can go wrong - take a beaker of water and drop in a spoonful of brown sugar. Pretend the sugar is fissionable.
At the start, you have a subcritical mass of brown sugar. Safe enough to hold in your hand. At the end, the sugar is distributed evenly enough through the water that even with the water's moderating effect, it's subcritical. Safe enough to work with.
Walk away from the beaker and come back in 5 minutes. Observe that there are regions in the beaker of varying concentrations. At least one of these concentrations will be the "right" concentration to minimize the mass required for criticality. If the volume of that region is large enough, it goes critical in that region and it's game over.
For an even better version of this game, imagine you can stir it quickly enough so that this is never a risk. Mix it in a baking pan, so that the liquid is never deeper than 1cm, and most of the neutrons fly out the top and bottom of the pan. Give it to your friend, who pours it into one of those nice flasks with the spherical bottoms. The spherical shape allows many more neutrons to be absorbed. Your last thought is that "Safe enough to work with" only means "safe enough to work with in this container". Game over.
Or just carelessly leave the pan under the fume hood over the weekend. Or toss it in the freezer, and discover that as it freezes, the capacity to hold the material in solution changes, and some of it precipitates out. In either case, don't expect to get any work done on Monday morning, though.
Of course, now that I've gone through the hard ways to have this accident (about which anyone working in this environment would still know), putting seven times as much solute in the solution would also be a good way to screw it up.
Scary thought: If they could see the Cerenkov radiation - and weren't looking at the tank - it means the radiation flux through the fluid in the eyeball was high enough to cause a visible blue glow. That's a lot of radiation.
Remember all those "how to build your own atomic bomb" plans, that all worked out to "this won't give you a nuclear detonation, but it'll make one unholy hell of mess"?
The Japanese have just become the test case. While we're not talking about levelling cities or nuclear explosive yield, in terms of the physics involved - an uncontrolled chain reaction in a critical mass - the Japanese have arguably just nuked themselves, in the same sense that the Americans nuked them twice earlier this century.
It's a banner week for Darwinian Stupidity in the sciences, folks. First we lose a $125M space probe because two engineering teams didn't know the difference between metric and Imperial measure, and then a couple of Japanese fuel processing guys manage to top our blunder by accidentally building and activating something that's the fundamental equivalent to the core of an atomic bomb.