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Robot Saves the Day at Radiation Lab
An anonymous reader writes "Nature.com is reporting that records released this week by the US defense department read almost like a bad movie plot. Back in October a high-security radiation lab had a cylinder filled with radiation get trapped in its delivery tube network. Fortunately a specially designed bomb-disposal robot was able to retrieve the canister before the radiation was able to eat its way free.
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Cobalt 60 decays via Beta (electron) emission (and also emits an anti-neutrino), and has a half-life of 5.2714 years. Of course, electrons don't go far in air and are easily shielded, but Co60 emits gamma-rays (like very "blue" X-Rays) with an energy of 1.33 and 1.17 MeV (MeV= the energy it takes to move an electron from a long ways away to a potential of 1 million volts). Co60 is commonly used in industry for sterilizing and for killing off bacteria on food (it is also used in gamma-ray photography industrially). Cobalt 60 can be produced from bombarding iron with nuclear radiation, like inside a nuclear reactor or near a nuclear explosion.
Wikipedia article about Cobalt
The cobalt was stuck for three weeks. The warning sirens are a government regulation, something to do with informing workers of radiation source. The robot was brought in, but it took a while for the team (from Albuquerque) to get ready to go to White Sands with their robot.
This slashdot article is dupe. See sandia.gov for more poorly written details.
No, they wouldn't be fired; they work at a national lab :-P Seriously though, electronics that can handle intense radiation are expensive.
The article that I read several days ago said that they use the cobalt-60 to test radiation resistance... they want to see the effects that high radiation levels will have on various pieces of military and civilian hardware. They set up their test gear, shuttle in the cobalt via pneumatic tube, let the gear cook in the extremely intense radiation, and then shuttle the cobalt back into a 'safe' area. I believe the original article claimed that cobalt is good for this, because it doesn't make the whole area permanently radioactive, though I'm not familiar with the reason why. (gamma radiation, maybe???)
... radiates. And it was ALREADY free, that's why the needed the darn robot. That whole testing area was absolutely lethal to human beings, even in heavy protective gear. Even the robot couldn't survive it very long... they thought 50 minutes. In actual practice, it lasted longer... but the movement system did fail, so they had to drag it out with a rope.
The writeup on the article is misleading. Radiation doesn't 'eat its way free'... fer chrissake, people! Acids eat things. Radiation just
To the person asking about building a Faraday cage around it.... as far as I know, a Faraday cage isn't an absolute barrier, it's just a very strong one. It attenuates a signal by a very great deal, making signals interception very difficult. But in this case, the 'signal' (the cobalt) is so incredibly powerful that a Faraday cage would just take the edge off, as it were. If my limited understanding of radiation is correct, it'd be just about as effective as sunglasses in front of a supernova. (and I'm not sure that Faraday cages even *work* at these frequencies... the radiation might just punch right through the shield material.)
The US no longer builds nuclear weapons. They actually are dismantling some. Sandia does a lot of SIMULATIONS of such weapons. I'm sure they have materials around to gather data for the simulations but they don't make bombs anymore. When the bombs were made, most were made at a facility outside Amarillo, TX.
I forget if they also use gamma rays to image concrete, or if that's other kinds of radiation, but there are times you want to crash the tank into the wall and see how badly you bent the wall.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
you're quite correct... a Co-60 source isn't going to eat through the cicuitry... That's just stupid... It can produce enough heat to melt circuits (assuming it's a very high-fluence source), but the article must've been written by someone ignorant of health physics, since it's quite obvious Co-60 isn't an acid, eating through a container... Finally, these sort of tests were likely done for gamma spectroscopy, where you can use gammas to examine imperfections in materials(it is probably the most common radioactive isotope used in nuclear labs today).
Irradiation doesn't make things radioactive. Exposure to a neutron flux can cause materials to become activated, but unless you've got a nuclear reactor around this isn't likely to be a problem.
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ultrasonic modem, the sound waves pass through the shielding and back to the base, or to an ultrasonic microphone and emitter pair on a long wire, since those components would be less sensative than digital circuits
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Cobalt-60 emits gamma radiation, which is comprised of high-energy photons. Photons only react with electrons, not nuclei, so if element X is exposed to them, it will still be element X afterwards, with its atomic number and mass unchanged.
It isn't the shape of the Faraday cages that's special. It's the size of the mesh. The mesh has to be significantly smaller then the wavelength of the radiation you are trying to keep out. Microwaves have a wavelength of 1-300mm. The wave-length of gamma rays is less then 0.00000000001mm. That's much smaller then the distance between atoms in a typical solid, so the idea of a mesh becomes kind of absurd.
I doubt that the problem with shielding is communications. After all you could put the shielding on the side facing the radiation, and leave the side towards the crew open. Gamma radiation doesn't go around corners. Or, as others have suggested, you could just run a cable to the robot. I think the actual problem is weight. Lead is heavy. You might be able to pile a ton of lead around the cpus and memroy, and just crank up the horsepower of the motors. However, by their very purpose you can't put the sensors behind lead sheilds, since all they would see then would be the lead shield. Not very helpful.
TFA says the alarm was caused by a cylinder wedged inside a transport tube by a defective switch and that it took them three weeks (presumably of trying everything available in-house) to come up with the robot idea.
/. article could have been titled "Mighty Mouse strikes back" - TFA says the robot used was called "Mighty Mouse 2".
The
Mayak, where the Soviet Union pumped out tens of tons of plutonium for nuclear weapons. Some info on how the Soviets fixed the 'it got stuck' problems - no fancy robots for them. http://www.thebulletin.org/article.php?art_ofn=so9 9larin
"A complete repair would have taken at least 12 months..."
""That meant that the irradiated uranium fuel had to be pulled up by hand into the central hall of the reactor and placed in a special storage area. Then, when the repair was finished, the elements had to be loaded back into the reactor. Over time, we unloaded and reloaded 39,000 fuel elements. All of the plant's personnel took part in this work and they received huge doses of radiation. The repairs were finished in two months."
"several hundred kilograms of freshly irradiated nuclear fuel got stuck--men from everywhere in the plant were called out, and one after another they used long steel rods to push the elements into the apparatus. The only protection they had was cotton overalls and gloves."
Domestic spying is now "Benign Information Gathering"
Our local county bomb disposal team has a robot and they only use fibre for remote control to avoid having any EM radiation (even from electrical signaling on copper) triggering the device being handled. I can't believe a small county in Utah is bleeding edge with their robot!
Actually Cobalt 60 is a Gamma emitter. Gamma is EM but very high frequency. The majority of the radiation from it is not particle radiation unless you count photons are particle radiation.
The holes in the shielding on a microwave have to be smaller than the wavelength of the microwaves. Gamma has a wavelength smaller than visible light so the holes would have to be too small for even light to pass through. It is also a lot more energetic so the thin metal shielding used in a microwave wouldn't be of much use. So a faraday cage "could" work if it was thick enough and had small enough crystal structure the be effective the only problem is I don't know of any material that meets those requirements off the top of my head. A high density shield of say, lead would be far simpler.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
Ohio University has its own reactor which is used for experiments in power generation as well as irradiation of materials. Anyone from nearby colleges can request time with the reactor to irradiate just about anything they want.
To get the material close to the core, pressurized tubes are used. The canisters that hold the material are made of some sort of plastic-like material for the specific purpose of letting radiation pass through. The problem is, repeated exposure causes the material to become brittle and occasionally a canister will break on the return trip (most often, it seems, when it slams into the retrieval portion of the tube and comes to a halt.)
The tubes are necessary to prevent people from coming into close contact with materials that are still radioactive for a time. The person running the experiment only has to load the canister with the material they wish to irradiate, load it in the tube system and send it on its way. The system halts when the tube reaches the core. After some time, the experimenter recalls the canister and can do whatever they please with it, knowing that it will still be emitting small amounts of radiation.
I don't know what the procedure was in the case that a canister failed during transit and material was caught somewhere between source and core. I do know the reactor is not very big (but neat to watch glow in the water) and the radiation danger wasn't too great. I believe it was said that most of the remaining radiation from the material dissipates within 5 minutes of the return. There are tables and shielding boxes with timers on them near the retrieval area.
The point is that radiation can eat through materials. It may not be the best way to phrase what really happens, but materials exposed to radiation react differently. Many materials become brittle. A radiation source as strong as the one in the article (with no mention as to what the cylinder was composed of) could cause any number of problems for anything nearby. The tubes are meant for short exposures as a material passes through, not prolonged exposure of a stuck cylinder.
Distance helps a ton when protecting against a radiation source. Assuming the source radiates in all directions, the amount of radiation received is proportional to the surface area of a sphere at whatever radius. I know for electromagnetic radiation it can be measured in mW/cm^2, not sure what the appropriate exposure unit is for gamma radiation. At 100 yards, the amount of radiation received is 120,000 times less than at 1 yard, and so forth.
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Is there anything tough enough to sheild against these particle emissions?
Depends on what it is. For alpha and beta particles, generally a couple pieces of paper will be an effective shield (since the particles are charged, they interact electrically--the alpha more so than the electron). For neutrons, a highly hydrogenated substance, such as water or polycarbonate, will be effective slowing down neutrons to thermal energies. It depends on the energy of the initial neutron, but typically you need only a few feet. You can then easily capture the neutrons in the end with a boronated substance. For gamma rays, any substance that is very dense will do since it will give the incident photon more chances to react. Each time the photons interact with a electrons (or occasionally, a nucleus), Compton scattering occurs and the re-emitted photons (now a spherical wavefront) now have a lower frequency. Given a thick enough dense substance, such as lead, very few high energy gamma rays will sneak through.
In general, only neutron and gamma radiation is significant for radiation workers or equipement because alphas and betas are so easy to shield.
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Gamma radiation is very high energy (and short wavelength) EM radiation. Neutrons are...neutrons. Alpha particles are Helium nuclei, and Beta radiation is positron radiation. That's about it for the types of radioactive decay radiation [sic].
A sheet of paper is sufficient to block alpha particles. A thin sheet of wood will effectively block beta radiation. Lead works well for neutrons, and a LOT of lead is required for gamma radiation.
Read back on the experiments with that B-36 that had a nuclear reactor on it. The crew area at the front was protected from the otherwise unshielded reactor core by something like 20 *tons* of lead...
We are still producing all the components, including a recently revitalized capability to manufacture the fissile pit (technical term for the uranium or plutonium core). We didn't have that ability for about a decade, but have been able to in small quantities again for a few years.
Bombs were being completely dissassembled and rebuilt throughout, for reliability testing and analysis purposes. In some cases, most or all of the other components were replaced.
As was this: "...a cylinder filled with radiation..."
Radiation is a phenomenon, not a thing. The cylinder was filled with materials which were radioactive.
Sigh.
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