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Cosmic Rays To Reveal the Melted Nuclear Fuel In Fukushima's Reactors
the_newsbeagle writes: Muons, produced when cosmic rays collide with molecules in the atmosphere, are streaming through your body as you read this. The particles pass through most matter unimpeded, however they can interact with heavy elements like uranium and plutonium. That's why engineers at Japan's Fukushima Daiichi power plant are using muon detectors to look for the melted nuclear fuel inside the plant's three melted-down reactors. By determining where muons are being diverted from their paths, the detectors create images of the blobs of fuel. That's necessary because nobody knows exactly where the radioactive gloop ended up during the meltdowns.
Gloop?
Gloop is an industry term.
Muon shadowgraphs of the Moon, a signature of the Moon's cosmic ray shadow on the upper atmosphere, are a common way of testing neutrino detectors buried under a km or more of rock. (Muons from the atmosphere tend to be the major source of confusion for such detectors; that's why they frequently do best looking down, as muons can't go through 12,000 km of rock.)
Oh, and archeologists have used muons to look through the Great Pyramid.
We've been using muon detectors for over 40 years to detect nuclear-related activities in various countries, including reactor installation, stockpiling, bomb-building, and so on. One of the reasons for the ability to move MX missiles around underground was so that long term muon detector observation by the Soviets could not pinpoint the location of the missiles.
I wonder if we can get some good images of the elephant feet that are all over that building...
Yes it's an anecdote! Were you expecting original research in a Slashdot comment?
Whenever talk turns to Fukushima, I'm always surprised at how little is known of the dark side of America's nuclear history.
Did you know the first meltdown in the U.S. was in Los Angeles? And the reactor had no containment.
https://www.youtube.com/watch?v=-_FCvbc0cNE
https://www.youtube.com/watch?v=DPk9kEaSyAY
Did you know about the Santa Susana Field Laboratory and it's ten reactors? Four of which had nuclear accidents.
http://en.wikipedia.org/wiki/Santa_Susana_Field_Laboratory
And this is only a very small part of the story. Be glad you are not raising a family in Canoga Park.
You've got to remember that these are just simple sub-atomic particles.
They are unstable. Common clay of the elements.
You know... Muons
I would have thought the fuel would remain hot for years, if it escaped confinement it could keep moving 'China Syndrome' style for a looong time...
I thought the term of art was Corium
I saw some documentary on TV not too long ago, that talked about using muon detectors to look for fissionable materials being smuggled for terrorist purposes hidden in transport containers.
In theory, theory and practice are the same; in practice they're different. (Yogi Berra & A. Einstein)
Radon's transform is really useful here
That makes no sense. Muon transmission tomography requires you place the object you are scanning between the detector and the source (the atmosphere). It is very difficult to get any signal coming up from the ground, and unlike neutrinos, muons are eventually stopped by the ground. There would be no way to detect material someone is trying to hide, unless they let you put a detector right next to it. Similarly, muon scattering tomography, which is just over ten years old now and what is being used to map things like Fukushima, requires you to move a detector all around a target for a lot of cumulative time to get any detail. And nuclear decay does not produce muons, you need higher energies (e.g. cosmic rays or particle accelerator). So no amount of moving missiles around is needed, unless you keep using Soviet supplied pallets underneath your weapons.
Underground mobile transport was to permit the usage of dummy silos, straining Soviet targeting and soaking up warheads.
That is an actual use, of CMT, unlike the fantasy of detecting deviations in muon flux through thousands of kilometers of dense, proton-rich material.
Primer from LANL:
http://www.lanl.gov/quarterly/q_spring03/muon_text.shtml
It is complete garbage, as pointed out by a few posts now. Yes, muons are starting to be used for monitoring for nuclear material, but that has to do with things like shipping containers and ships, where you can get up close or even send things through a portal/frame thing that measures all around it. But that is only a couple years old, and doesn't work over the distances needed for Soviets to tell where US missiles are.
Mod this up, not the GP post which is flat out bullshit.
Muon tomography has only been around for just over 40 years, when it was first used on the ground, in a stationary setup (not counting earlier uses where it only measured thickness, not full tomography). It was nowhere near the state of being a portable tech with the resolution need for nuclear related activity at a distance of kilomters, something that would be a struggle even today without massive resources.
On the way to you via Pacific currents and transpiration and the food chain. The liquid magma will continue to melt toward the core of the earth unless it hits ground water and causes steam explosions, washes into the sea, creates a volcano, or steam volcano, or hits the core, volcano again. And you wondered what the dampening was for over Chernobyl.
The last place it will ultimately be is within any buildings though it may still have part of it in the basement. Containment has completely failed and there is no plan or ability to deal with the problem. The ocean born plume including cesium plutonium is on it's way to an environment near you soon. There was also a recent steam explosion and building 4 so stay alert for elevated radiation readings.
Let's consider a few numbers. The incidence of muons is on the order of 100 per square meter. Let's assume a nuclear weapon has a dense core on the scale of a square meter (a huge over estimate), and that the muons get scattered uniformly (also a huge over estimate, as most are not backscattered). If you had a detector directly overhead, say 90,000 ft, and lets say the detector was 60 ft by 100 ft (i.e. a detector the length and width of the U2, much, much larger than what would actually fit inside a U2 or SR-71 plane), then you can work out the amount of scatter muons that would reach the detector would be about one per two days.
The work at Fukushima is expecting to use 50 m^2 of detectors, so about a tenth the huge size used above but still on the large size for an airplane, and for it to take several days of continuous monitoring at a distance of ~ 20-40 m from the reactor, which happens to also be much bigger than a nuclear weapon.
If you take away the orders of magnitude over estimates above, it would take months or years of continuous observing just to record muons from a weapon, to say nothing of how many you would need to distinguish it from any other dense material. At least in the Fukushima case, they are trying to distinguish an empty void from dense metal, not slightly different densities of metal.
Oh, forgot to add one more thing, that a highly relativistic muons from cosmic rays have relativistic factors on the order of 10, and so you might get it to travel about 4500 m before losing half due to decay. So at a distance of ~90,000 ft, even if assuming scattering doesn't lower energy of the muons (the paper about using the technique on the reactor, for example, mentions they tend to lose a lot of energy during scattering), you lose another factor of ~30 from just decay.
So now, using much exaggerated conditions, you are expected to see one muon every couple months of continuous, direct, over head observation.
That's a great scene from "Blazing Saddles."