Meltdown at Three Mile Island (Documentary)

As I type this, there are at least two nuclear reactors in serious danger of meltdown in Japan. I think they are already in partial meltdown. I don't know, because nuclear reactors are tough things to get inside, and Japan's nuclear regulatory agency is spending most of its time trying to avert disaster rather than speculating on what might be happening (this doesn't stop lots of pundits, myself included, from weighing in). For the latest, check this page from the IAEA. But despite the headlines, we must remember Douglas Adams's advice: "Don't Panic." (Always, always bring a towel.)

Reactor cooling efforts over the weekend included flooding the reactors with seawater and boric acid, after several explosions in containment buildings around reactors. A third explosion in a containment building was reported today. Explosions at nuclear plants often include a release of radioactive material, but it's debatable how much impact any given release is. This doesn't look good -- but it's not the end of the world, either. On the bright side, the term "meltdown" isn't quite as bad as most people think. It means there's something seriously wrong with the cooling system in a nuclear reactor, and continued failure of the cooling system leads to overheating, which can lead to bad things like explosions. Meltdowns can be contained (indeed the reactors are designed to contain them), or they can turn catastrophic -- and the meltdowns in Japan appear to be containable. In other words, even if there are two or three meltdowns in these reactors, we aren't necessarily talking about two or three Chernobyl-level events. It's hard to say what the eventual fallout (apologies for the pun) will be, but I'm guessing Japan has three Three Mile Islands on its hands. And, in case you don't know, the TMI-2 reactor was (more or less) cleaned up, albeit at great expense (nearly $1 billion) and over a shockingly long time (roughly 14 years). TMI is its own story, and that story is told in a documentary I've embedded below.

As the tragedy unfolds in Japan, lots of people are wondering: what's a meltdown? How does a nuclear reactor work? Weirdly enough, I studied this topic in college, although my degree is in Library and Information Science. I took a series of courses covering major disasters, with the notion being that if you could understand how a disaster occurred, perhaps the things you built would not themselves be so disaster-prone. (I went on to build computer systems and software -- fortunately none that were "mission critical.") On Saturday, fellow _flosser Maggie Koerth-Baker posted Nuclear energy 101: Inside the "black box" of power plants, a good overview of the technology involved. Read up, then come back for the documentary I've posted below: Meltdown at Three Mile Island.

The common pattern in a disaster is the confluence of at least one technical or environmental problem (for example, an earthquake knocking around some nuclear power plants), leading to secondary technical problems (the tsunami apparently disabling backup diesel-powered cooling systems at those plants), and then human behavior that interacts with those problems in unexpected ways (human attempts to shut down reactors can sometimes be destructive by themselves, although they're always well-intentioned -- currently Japanese nuclear plant workers have a makeshift cooling system rigged up to replace the failed diesel backup pumps, but it's not perfect). The operators of nuclear reactors often have limited information about what's happening inside the reactor itself, and workers under pressure to make decisions on the fly. Sometimes these high-pressure decisions turn out to be correct -- other times, not so much.

Here's a representative quote from the TMI documentary: "If the operators had not intervened in that accident at Three Mile Island and shut off the pumps, the plant would have saved itself. They had thought of absolutely everything! Except: what would happen if the operators intervened anyway?" -Mike Gray, author of The Warning: Accident at Three Mile Island. (See also: Normal Accidents: Living with High-Risk Technologies, a classic text by Charles Perrow.)

The rest is after the jump.

Another good resource: Mr. Reid's explanation of the situation (Reid is a Physics teacher).

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Cs California, Wikimedia Commons // CC BY-SA 3.0
How Experts Say We Should Stop a 'Zombie' Infection: Kill It With Fire
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Cs California, Wikimedia Commons // CC BY-SA 3.0

Scientists are known for being pretty cautious people. But sometimes, even the most careful of us need to burn some things to the ground. Immunologists have proposed a plan to burn large swaths of parkland in an attempt to wipe out disease, as The New York Times reports. They described the problem in the journal Microbiology and Molecular Biology Reviews.

Chronic wasting disease (CWD) is a gruesome infection that’s been destroying deer and elk herds across North America. Like bovine spongiform encephalopathy (BSE, better known as mad cow disease) and Creutzfeldt-Jakob disease, CWD is caused by damaged, contagious little proteins called prions. Although it's been half a century since CWD was first discovered, scientists are still scratching their heads about how it works, how it spreads, and if, like BSE, it could someday infect humans.

Paper co-author Mark Zabel, of the Prion Research Center at Colorado State University, says animals with CWD fade away slowly at first, losing weight and starting to act kind of spacey. But "they’re not hard to pick out at the end stage," he told The New York Times. "They have a vacant stare, they have a stumbling gait, their heads are drooping, their ears are down, you can see thick saliva dripping from their mouths. It’s like a true zombie disease."

CWD has already been spotted in 24 U.S. states. Some herds are already 50 percent infected, and that number is only growing.

Prion illnesses often travel from one infected individual to another, but CWD’s expansion was so rapid that scientists began to suspect it had more than one way of finding new animals to attack.

Sure enough, it did. As it turns out, the CWD prion doesn’t go down with its host-animal ship. Infected animals shed the prion in their urine, feces, and drool. Long after the sick deer has died, others can still contract CWD from the leaves they eat and the grass in which they stand.

As if that’s not bad enough, CWD has another trick up its sleeve: spontaneous generation. That is, it doesn’t take much damage to twist a healthy prion into a zombifying pathogen. The illness just pops up.

There are some treatments, including immersing infected tissue in an ozone bath. But that won't help when the problem is literally smeared across the landscape. "You cannot treat half of the continental United States with ozone," Zabel said.

And so, to combat this many-pronged assault on our wildlife, Zabel and his colleagues are getting aggressive. They recommend a controlled burn of infected areas of national parks in Colorado and Arkansas—a pilot study to determine if fire will be enough.

"If you eliminate the plants that have prions on the surface, that would be a huge step forward," he said. "I really don’t think it’s that crazy."

[h/t The New York Times]