Tuesday, April 5, 2011

Nuclear power, hurray!

Terrible stuff, nuclear power. It's not nice and clean, like coal power stations. And it doesn't work during the night, like solar power. Nor is it reliable in all weather conditions like wave and wind power, or as simple and easy to build as fusion power. Terrible stuff.
But seriously now. Nuclear power stations have been around for the last fifty years or so, in a fair few countries. They provide enough power that switching them off and making up the loss by using cool twisty light bulbs isn't an option. Unfortunately, catastrophic events like the train wreck at the Fukushima station are enough to frighten the hell out of most of us, and ensure the Greens will get a good turnout by promising No Nukes In Your Back Yard, without having to say where they'll find the juice to run your iKitchen for the next fifty years while they figure out how to get electricity from positive vibes, man.
We're scared of nuclear power. We see the fires, we see the explosions, worst of all we see those colourful maps showing radiation plumes and we think No Way, they're not building one of those at MY favourite surf beach. Then we turn off our plasma TV and go to sleep in our air conditioned bedrooms, smugly reassured that we're doing the right thing by our children by voting against anyone who even suggests building one of those demon-nests.
But are they that bad? Are they really likely to kill us as we sleep, dreaming of fawns frolicking beneath the moonlit chimneys of happy fuzzy coal-fired power stations? Let’s see how scary they are by looking at the worst nuclear accidents to date.
Bambi! NOOOO!

What went wrong at Windscale?
At the end of World War 2, the US had a monopoly on nuclear weapons. And they thanked their staunch British allies for holding back the Nazis single handed for two years by refusing to tell them anything about atomic bombs, other than that “they’re really swell.” The king was a bit put out by this, so he told his chaps to get cracking on a British bomb. This they duly did, building a thing called a ‘nuclear pile’ at the sleepy little coastal village of Windscale.
You might like to think nuclear facilities are precisely engineered things, all flashing lights and soothing green corridors. The ones that make electricity usually are. But the Windscale piles were bomb factories. And they were built in a hurry, to get a working bomb out there with, to quote the foreign minister of the time, “…the bloody Union Jack on top of it.” The end result was pretty light-on for flashing lights and soothing paint. What it did have was a huge block of dirty, dusty graphite, with a series of head-sized holes poked through it. Making bomb fuel was as simple as shoving aluminium cans full of uranium into the holes and gradually pushing them through to the other side. The radiation would partly change the uranium into plutonium by the time the cans fell out the other end into a ditch full of water to cool them down.
The brown stuff? That's graphite. Like in pencils. The things with fins? That's uranium. Like in "red-hot glowing metal of death."

If you think this all sounded a bit agricultural, you might be right. It worked, but there were some pretty frightening design features. Scariest of all was that this thing was air cooled. The radioactive cans got hot as they moved through the pile, but rather than piping in water, the designers just stuck a bunch of giant fans on the end and blew colossal amounts of air through it. So much in fact that it sometimes blew the cans out of the holes. The hot air went up through a chimney which, in the original design, was simply open at the top. Sir John Cockcroft, the bloke in charge of the project, reacted pretty much the way you just did when you read that, and forced the builders to stick filters on the top. They got a bit snippy about doing this, and named the filters ‘Cockcroft Follies’, which is as close at the British ever get to saying “screw you, pal.”
Despite all of this, the piles worked, and pretty soon the British had enough plutonium to build some bombs and give the hippies of the future something to get cranky about. But the whole nuclear thing was a bit new, and everyone was making it up as they went along. One of the surprising things was that the big pile of graphite would sometimes get really hot for no apparent reason. They figured out what caused it and how to fix it (Wigner energy and annealing if you’re curious), but  it meant that after each production run they would have to gently warm up the pile for a bit, sort of giving it a big nuclear hug to calm it down ready for the next run.
They started the annealing process for the ninth time on October 7th, 1957. Things went to plan, but it didn’t seem to work, the pile not releasing the stored heat as it should have. The engineers decided to have another go and pulled out the control rods again, cranking up the pile.
On October 10th (the process took days), they realised something was wrong. Rather than falling, the temperature inside the pile was now rising. They tried to fix it by turning the fans up to eleven, blowing lots of nice cool air across the pile. Rather than fixing it, this just made the radiation detectors at the top of the chimneys start clicking like a swarm of horny crickets. The manager’s mood shifted from ‘miffed’ to ‘peeved’, and he sent his second in command in to take a look.
Number 2 was a bit troubled to find the remote looky-inny thing was jammed, because it meant he had to go to the pile and actually peer inside. When he and a somewhat nervous offsider pulled an inspection plug, they were a little concerned to see “…four channels of fuel glowing bright, cherry red.”
Now, uranium is nasty stuff. Red-hot uranium really isn’t something you want to see, ever. The Windscale crew were looking at several cans of it, deep inside a space so radioactive that air blowing across it sent the detectors off scale. They probably uttered a few choice British swear words, slammed the hatch shut and headed for somewhere with less red-hot uranium nearby.
Things got pretty crazy after that. Incredibly, it had never occurred to anyone that the pile could catch fire, so they were stuck for what to do. Since the fuel canisters were the source of the heat, they tried to bash them out of the pile with long steel poles. Nothing moved, and the ends of the poles came out dripping molten uranium, because glowing uranium wasn’t nearly scary enough. Plan B involved a little tank of liquid carbon dioxide they had on hand. They hooked that up, but  Tom Tuohy, the manager, said afterwards “…we had this poor little tube of carbon dioxide and I had absolutely no hope it was going to work.”
It didn’t. Tuohy went to the top of the building to look down inspection holes to see what was going on. Determined to top the whole molten-uranium-on-a-stick thing, he reported back that there were blue flames shooting out of the fuel channels. The uranium wasn’t just hot; it was burning. Eleven tons of it.
With few options left besides sticking their fingers in their their ears and cowering behind desks, he decided to go with an old school solution. Fire hoses were dragged out, tied to the ends of metal poles (probably not the same ones) and poked into the pile. With Tuohy standing on top of the pile building where he would get the best view of any explosion, they turned on the tap.
To the relief of everyone downwind, it worked. Tuohy stayed on the roof to keep an eye on things, although “…I did stand to one side, sort of hopefully," he said afterwards, adding that "…if you're staring straight at the core of a shut down reactor you're going to get quite a bit of radiation."
Tom Tuohy. Cajones the size of Tasmania.

The air filters on the chimneys, added only at the last minute, stopped most of the radiation. Nonetheless, a plume of contaminated dust spread west towards Ireland, which, luckily, was uninhabited at the time. Detectors in Sweden, Finland and Denmark picked up the plume, which, luckily, didn’t have any people who could vote out the British government. The government responded quickly to the disaster, choosing which operators to blame the whole mess on and changing the site’s name to Sellafield so everyone would forget it ever happened. Then they hushed it up as best they could so the Americans wouldn't think they couldn't be trusted with new toys.
Fifty years on, the pile is still there, still sealed and still full of radioactive slag from the fire. Pile 2 never had an accident, but it was shut down soon after, because...well, burning uranium. You know. The adjoining building have been converted into a conference centre, where sales teams and advertising executives go to have any lingering traces of humanity blasted out of them by gamma rays.
The lesson from this? Always, ALWAYS have at least half a dozen ways to keep your reactor cool. Make sure none of them involve poking it with sticks.

What went wrong at Three Mile Island?
1979 was a rough year. John Wayne died, disco was king and Roger Moore made Moonraker, the most idiotic film that wasn’t Avatar. And in March, reactor number 2 at the Three Mile Island Nuclear Generating Station almost melted down because of a stuck valve and a hidden warning light.
Three Mile Island was a power station, not a bomb factory. It had lots of nice safety features, plenty of good, thick concrete and none of the “Wait, what?” feature that made Windscale look like a mad scientist’s doomsday device. And most of it worked pretty well. On March 28, 1979, when a little water pump shut down, a backup pump thingy didn’t work. Some bigger pumps got cranky when they weren’t getting their water, so they shut down too. This escalated all the way to the main cooling pumps, and when they shut down, the reactor automatically went into a sulk, dropping its control rods all the way in and turning itself off. Total time from the first pump failure to reactor shutdown was eight seconds.
Three Mile Island control room. Note lack of molten uranium

So far so good. The reactor was still making a bit of heat (uranium’s like that; much like a cranky two year old it’ll keep simmering awhile even after you put it in a time out), so pressure inside the water pipes started rising. Even this was fine; when the heat raised the pressure a bit too far a valve popped open, venting some coolant to a really big overflow bucket nearby.
No, bigger.

But the valve got stuck.
Instead of closing when the pressure dropped, it stayed open. Maybe it was a bit rusty, maybe a curious bug got jammed in it, maybe its feng shui just sucked. Nobody’s sure. What is certain however is that it meant the coolant system was no longer closed. Any coolant they put in would flow straight out to the bucket, which meant it wasn’t in the reactor keeping things cool.
And thanks to a design flaw, the operators couldn’t tell it was stuck. The little light saying ‘Valve thingy open’ was dark. They thought this meant ‘Valve thingy closed’. But what it actually meant was ‘Valve thingy not being TOLD to open.’ Since it was jammed open, it didn’t matter what they were telling it to do, it was off on its own little mission. So when they started pumping in more coolant, it headed straight on out to the overflow bucket. The coolant began to run out, the top of the reactor core was exposed and uranium began to melt. Molten uranium is bad.
But before anyone started talking about looking through ports or poking anything with steel rods, a new shift took over in the control room. They realised what was happening, stuck a cork in the overflow pipe and started putting coolant back in.
Things slowly came under control. There was radioactive water in places you don’t really want radioactive water, and the operators had vented radioactive steam to the atmosphere, but the feared containment breach hadn’t occurred. And almost nothing had exploded, caught fire or melted. Much. Radiation had definitely made it to the outside world, but there had been no deaths or injuries.
The cause was eventually found to be the sticky valve, plus the dodgy indicator light, plus some idiot deciding it was okay to shut down all the backup pumps when the reactor was running close to full power. Take away any one of these factors and the reactor might not have overheated.
The lesson from this? Always, ALWAYS have at least half a dozen ways to keep your reactor cool. Make sure none of them rely on one valve, one light or one person. And always have a bucket.

What went wrong at Chernobyl?
Ironically the worst accident in the history of nuclear power occurred during an experiment to make the reactor safer. Chernobyl had nice diesels to keep the coolant flowing if the reactor shut down, but they took a minute to start. So one night in 1986 they decided to test a way of powering the pumps for that critical minute while the diesels woke up and got their boots on.
Running the test meant reducing the reactor power level. Weirdly, this was a lot harder than going the other way; whenever the operators turned the wick right down, the reactor would surge and stall and generally bounce around like a learner driver on their first time out in dad's car. One of the causes was something called reactor poisoning. A gas called xenon (pronounced zee-non) forms inside nuclear reactors. it's a little bit like the exhaust from a car; if it backs up into the engine, it can make it run rough, and even stall. Once the reactor is running it gets burnt off, but when it's idling, it can cause real problems. Having this gas in the Chernobyl was like having a banana shoved up a car's exhaust, making it hard for them to get it to idle smoothly.
Xenon: pretty in lights, ugly in reactors

Their solution? The operators pulled the control rods all the way out.
Now, normally, this was what they did when they wanted the reactor go flat out. But thanks to mister xenon doing the banana in the tailpipe trick, it barely got the reactor turning over. So when they started the experiment, it was in a very unstable state, with the ‘accelerator’ mashed to the floor but the ‘engine’ struggling to turn over.
The operators either didn't know this, or didn't care. At 0123 am they started the experiment. Logs found after the event show that things went smoothly for the next forty seconds. Then, at 0123 and 40 seconds, someone pressed the emergency shutdown button.
Since both engineers on duty died, nobody knows who pressed it or why. It might have been planned, it might even have been an automatic shutdown. Regardless of the cause, things rapidly got worse.
Emergency shutdowns, or scrams in reactor-speak, involve quickly shoving control rods into the core. These are made of radiation-absorbing metal, which cools everything right down. These rods are the go-to guys when everything else is letting you down, the ice water in the face when things are getting a little panicky, and they work well in almost every instance. But Chernobyl's safety rods had a problem. They were mostly made up of the useful radiation-sponging metal, but for some reason the ends were made of graphite. Radiation blows through this gear like headlice through a primary school, so they didn't cool things down at all. What the graphite tips did do was push water out of the reactor as they were lowered in. And water does absorb radiation...
So when the safety rods were inserted, they had the opposite effect. With the water pushed out, the fuel heated up. As it got hotter, more of the water boiled, removing even more radiation-absorption. And the xenon gas that was stalling the reaction started to burn away.
In less than five seconds the reactor power doubled. The effect was like blowing the banana out of the tailpipe; suddenly the obstruction was gone, and the go-pedal was flat to the floor. The temperature rose rapidly and a powerful explosion shifted the thousand-ton lid on the core.
This did more than release some radiation. The core was bolted to this lid; moving it broke more fuel rods and cracked cooling piles. Worst of all, the emergency control rods got stuck halfway down. Now, not only was the reactor at full throttle, but the brakes had been cut.
The last record in the supervisor's log says "Severe shocks: the RPCS (safety) rods stopped moving..." Moments later a second, even bigger explosion flipped the massive concrete lid like a coin, dropping it sideways into the core. The last reading on the reactor's power gauge showed output increasing from 500 megaWatts to 33 gigwatts.
Two people died in the explosion. 31 died from acute radiation sickness, mostly firefighters. A beam of bright red light, visible for miles, shone skywards from the ruptured core. Contamination rained down on a nearby forest, turning the trees red.
The red forest. Fallout killed every tree.

Over the next six months, six hundred thousand people were involved in the cleanup. Each was only allowed on the site for forty seconds, receiving an entire lifetime's dose of radiation in this time. The common term for these workers was 'liquidators'. The military called them 'bio-robots.'
Vehicles used by the 'liquidators'. Too radioactive to recover, they are still there today

 Two cities, Pripyat and Chernobyl, were evacuated; hundreds of thousands of people were moved. The site remains deserted today, the centre of a 1,600-plus square mile exclusion zone where wild boars roam deserted city streets and wolf packs stalk the handful of humans still living there. The reactor is still hot, still full of uranium and probably turning nice friendly wild piggies into giant mutant wild piggies with laser beam eyes and radioactive tusks.
Chernobyl today: somewhere between sad and creepy as hell.

The lesson from this? Always, ALWAYS have at least half a dozen ways to keep your reactor cool. Make sure none of them involve a corrupt communist regime. Also, never buy Russian pork chops.
Twenty five years after that explosion, Japanese firefighters were pouring water onto the reactor at Fukushima, fighting to avoid their own Chernobyl.

What’s happening at Fukushima?
It’s too early to know exactly what’s going on in the world’s latest nuclear disaster, or even how bad it’s going to get. Latest news reports say radioactive water has been pumped into the sea, the resultant Godzilla-based Tweetfest briefly eclipsing Rebecca Black and Charlie Sheen on the top of Twitter.
As to what got them to this point? Presuming you didn’t start reading this blog here, it’s a familiar story. The reactors shut themselves down when the earthquake hit, so they were winding down nicely, getting rid of their two-year-old-in-time-out heat through their normal cooling systems. The backup generators were running, the reactors were nice and safe behind their 5.7 metre high tsunami wall and everyone was feeling fine.
Nobody ever expected a 14 metre tsunami.
The entire plant flooded. The backup generators busily chilling the reactors down were among the lowest-lying buildings. Even the best diesel will spit the dummy if you belt it with thousands of tons of seawater; as the flood began to recede the reactors started to heat up.
This isn’t just one reactor like Windscale, Three Mile Island or Chernobyl. Six reactors were suddenly without cooling. And the spent fuel ponds, still active enough to need constant water flow, were getting hot too. As the reactors heated up, hydrogen formed inside the cores. This leaked out into the external buildings; when enough had collected, the gas exploded, blowing open the buildings.
While it looked scary on television, these explosions were not ‘nuclear’, and spread little, if any, radiation. And the buildings they damaged were just outer shells that protected the reactors from the weather. Apparently there were systems in place even to deal with hydrogen leaks before they could cause explosions but, like every other system that failed, they needed electricity.
As of this blog, the crisis is ongoing. The whole plant has been written off. The reactors are now just radioactive landfill, thanks to the corrosive seawater used to cool them. Water pumped in to prevent meltdown has swept up radioactive debris, which is leaking, or being pumped, into the sea. Only a little airborne radiation has escaped, but it is enough to warrant binning all the spinach grown within thirty miles of the place (insert your own Popeye joke here). Power has been restored and coolant is flowing again, but there’s been so much damage that there is still the possibility of further chaos.
Preparing hoses to cool the reactors. Yes, that's duct tape.

The lesson from this? There is no lesson from this. At least, nothing that wasn't learned at the other three disasters. Maybe the sea wall should have been higher, but how much higher? Twenty metres? Fifty? Eventually it becomes so expensive that it's simply not worth building. I don't know enough to say that it shouldn't have been built there, but it does seem crazy to put atomic power on the coast that regularly gets pummelled by tsunamis, quakes and giant lizards. Japan's west coast is tsunami-proof; why not build it there? Surely not because the prevailing westerlies would blow contamination across their own country first...?

Sooo, nuclear power anyone?
These accidents highlight the biggest difference between nuclear power and every other kind. If your gas, coal, oil,solar or any other power station gets a bit out of hand, you can turn off the gas, the coal or the oil. Flick the switch on the solar cells, throw blankets over the mirrors, stick the cork back in the hydro dam; the thing will shut down and you’ll be able to fix it. But uranium? It has no Off Switch. Other power stations will just coast to a stop against a garden fence if you turn everything off, but nuclear power plants go the other way: if you turn everything off and go home, you’ll be coming back to a glowing slagheap surrounded by laser piggies. So you need backups for the backups, you need stable government with a strong safety culture, you need distance between you and anything that might flood, quake, slide, burn, erupt or riot. And you need just a little bit of luck.
But should we shut them down…?
Chernobyl killed fifty people. Estimates on how many have, or might, die of cancer vary, from a conservative 4,000 to a pessimistic 140,000. Nobody died in the Three Mile Island or Windscale accidents, although several long metal poles were badly traumatised. Five people have died at Fukushima, but they were drowned in the tsunami. So far, the only casualties attributable to radiation have been spinach.
Pound for pound, nuclear power is pretty safe when you count deaths per teraWatt-hour. A teraWatt-hour is enough electricity to power a small country, say, Madagascar, for a year. Or the United States for two hours. For each teraWatt-hour of nuclear power generated worldwide, the death toll, counting accidents, is 0.04. In other words, you can make 25 teraWatt-hours of nuclear power before you’re likely to kill someone.
The same figure for coal is 161. That’s deaths per teraWatt-hour. So by the time one person has died from nuclear power generation, you’ve killed about four thousand people with coal. Most of these deaths are from pollution-induced sickness. Plenty are from accidents in Chinese mines (taking just Chinese power plants, the figure is 278 deaths per teraWatt-hour). Just mining coal in China kills two thousand people every year, before they even set fire to the stuff at a power plant. That’s more people every ten days than Chernobyl killed in the first six months.
So maybe you’re thinking of putting solar cells up to save a few of those lives? Think again: deaths from rooftop solar are 0.4 per teraWatt-hour, usually from either falls off roofs or contact with live systems. Loosely speaking, you are TEN TIMES more likely to be killed by rooftop solar than by a nuclear meltdown.
Come a little closer...

But, of course, rooftop solar doesn’t give you cancer. And that’s what scares people. Coal plant exhaust and dust is much more likely to kill you, but for some reason people will live downwind of a coal plant in preference to living on the same continent as a nuclear plant. It makes about as much sense as James Bond In Space, but that’s how people think.
My guess is that it’s a bit like how people feel about flying. You’re a jillion times more likely to die in a car than you are in a plane, but way more people are frightened of boarding an aircraft than are scared of climbing into a car (except Hyundais, but…yeah, I’ll catch the bus thanks). But cars have been around all our lives, we grow up riding in them, we see millions of them tearing about safely every day, so we can’t associate the danger with the familiar act of going for a drive. Flying though? There are crowds, security checks, announcements, deadlines,  strangers sitting next to you, overtly gay stewards, weird plasticky food and countless other things unsettling us. And when those engines start screaming and we belt down the runway at speeds that make the oversized bags pop out of the undersized lockers, we can’t help thinking Wow I Really Wish I’d Driven.
Nuclear power is like that. Like air travel, most of the time we don’t notice it, but every now and then we see it go violently wrong on TV. And It’s all glowing pools and scary maps and faceless men in rad suits pointing Geiger-thingies at children and puppies. You can tell people as loudly as you like that it’s safer than coal, but unless they know the numbers, they’re still going to prefer the black, belchy coal plant that’s been in the town providing jobs since before grandad got lung cancer from not smoking on the job at the coal mine. And facts about people NOT dying in nuclear disasters don’t sell nearly as many papers as giant headlines screaming “MELTDOWN NIGHTMARE! STAY INDOORS! PUT YOUR RELATIVES IN PLASTIC BAGS! DON’T EAT THE SPINACH!”
But now YOU know the facts. All of the worst nuclear accidents in history have killed less people in total than a couple of bad years in Chinese coal mines. Nuclear power might make spinach hard to come by, but it’s less likely to kill you than going up on the roof and cleaning your solar panels. Well-designed, well-run reactors in geologically stable locations will quietly hum along, generating next to no greenhouse gases for as long as the uranium lasts (another 80 plus years, even if we stop looking for more now). I’m not about to tell you whether we should build more plants or shut down all the existing ones tomorrow.
But what I will ask you to do is make up your own mind. Nuclear power is complicated and scary, but so is global warming. Coal is much less complicated and scary, but it’ll kill you just as dead. And it’s a whole lot more likely to do so.
Either way, don’t eat the spinach. Radioactive or not, that stuff’s gross.