Tuesday, March 15, 2011

Fukushima: The Scare Y'all Were Waiting For

So, yeah, this is pretty much why people worry about nuclear energy. Great when it's working, but when it goes wrong, holy shit does it go wrong. This is an unfolding situation and I still have hope that the heroic efforts of the reactor workers and their helpers will pay off. But many of signs I've seen are pretty catastrophic, and I expect this to get worse before it gets better.

The good news is that even the worst Fukushima meltdown would not be a second Chernobyl. The choice of RBMK reactors for the Chernobyl power plant was incredibly stupid, even for the time, and was a product of even more unbelievably stupid cold war thinking. Virtually all Soviet industry in that era had to theoretically serve dual civilian and military purposes: car plants had to be able to be quickly converted to produce tanks, and nuclear power plants had to be able to produce mass amounts of plutonium for nuclear weapons. Why anyone thought it made sense to apply the same thinking to nuclear weapons production (estimated maximum length of a nuclear war: 2 hours) as conventional weapons production (estimated maximum length of a conventional war: 10+ years), I will never know. But that's hindsight for you.

Because of their stupid design, the Chernobyl reactors were made primarily with graphite, which burns. After the reactor massively spiked (read: exploded), the graphite was exposed to oxygen and ignited into a towering pillar of white-hot flame with a base that surrounded the still-critical reactor, shooting the equivalent of a 12-megaton bomb's worth of radiation into the atmosphere alongside the smoke. Furthermore, the plant was built without a concrete-and-steel vessel that would be capable of containing the radioactivity even in the event of such a meltdown. In this sense, the disaster could have been much worse: by dumping tons of neutron-absorbing material onto the hole in the building by helicopter, the Soviet army managed to cool the reaction (both in the thermal and radioactive sense) before it burnt its way into the groundwater.

(Fun Fact #1: there were actually FOUR reactors at Chernobyl, and the other three continued to operate for years after the accident.)

In contrast to Chernobyl, the Fukushima reactors are water-moderated and built within an intelligently-designed containment structure. Even if the temperatures got so high within the core that the fuel rods melt (which is looking more and more likely), there isn't any graphite to ignite and the containment structure would still have a fighting chance of keeping most of the radioactivity out of the groundwater and atmosphere. In theory, the torus-shaped shell underneath the reactor would spread out the fissionable material sufficiently to keep it from going supercritical and producing so much heat that it would melt through and escape into the ground underneath.

(Fun Fact #2: there is actually a name for the radioactive lava-like substance that is produced when a reactor melts down. It's called Corium.)

Thankfully, the reactor scrammed (shut down) successfully during the earthquake, and most of the heat in the core is caused not by chain-reacting nuclear fuel but by the remaining decay products from when the reactor was operating normally. As the short-halflife (ie, highly radioactive) byproduct isotopes decay into long-halflife (ie, less radioactive) isotopes, and thus do not decay (and release heat) as often, the excess heat problem will take care of itself. In this sense, it's a race against time that the rector operators will win if they can just hold on long enough.

That said, increasing radiation levels and additional fires and explosions can only mean one thing: the situation basically looks terrible at Fukushima right now, and is only getting worse. The fact that there have been hydrogen-caused explosions in the reactor buildings is actually a way worse sign than the explosions themselves: the most likely cause of hydrogen production under these conditions is the reaction between the casing of the fuel rods with the air at much higher temperatures than normal reactor operation. In other words, the fuel rods inside the reactor appear to have been exposed to the air for some time, at temperatures higher than 1000 degrees... and the resulting contaminated steam was vented outside the core.

Furthermore, pumping salt water into the cores is an absolutely last-ditch effort to stem a catastrophic meltdown, and is essentially an admission that the reactors will never operate again (at an instant loss of billions of dollars). The additional salt water produces additional contaminated water that either has to be contained or released into the environment, as well as introduces additional (and somewhat unpredictable) elements into the reactor core that can potentially produce additional, dangerous radioisotopes. The fact that salt water cooling appears to have failed at at least one of the reactors is an abysmal sign. There's not all that much more that can be done to save the reactors.

Now here's the real, real shit. As I've said, most Fukushima meltdown scenarios aren't globally, or even nationally, catastrophic: the possibility of true failure is on everyone's mind, but the reactor containment systems are reasonably well-designed and could probably keep a complete meltdown from seriously contaminating the surrounding environment. More worrisome are the on-site cooling pools that house spent fuel and byproducts from the reactor. This waste is flammable, highly radioactive, and largely unprotected - which is to say, tremendously vulnerable and dangerous in a situation like this.

Because they aren't going to be subjected to the same insane pressures and temperatures of a nuclear reactor core, the cooling ponds aren't protected with the same sorts of containment structures. And because they are home to highly radioactive substances, they require the same sort of cooling mechanisms that have failed at the reactors themselves. The timeframe is longer than for the reactors, but if the pumps remain off for too long and the heat level in the ponds rises sufficiently (particularly if reactor leaks render the area unsafe for work), a massive release of radioactivity is possible. This is before we even begin to consider the possibility that they have been damaged by the (ongoing?) hydrogen explosions.

Anyway, this is an incredibly complicated and evolving issue. I've skipped a lot of background info in this post, and there's still an enormous amount that I don't know myself. Ask questions in the comments, and I'll do my best to answer!


  1. Thanks for writing this up. This post follows the same pattern of a lot of your posts on nuclear issues.

    It's very interesting, you learn a lot of stuff you didn't know, and you leave more terrified than you were before.

    Question: Do the events in Japan make you more or less likely to visit Chernobyl as you had planned?

  2. Great post. Do you have insight into whether the emissions to date could be carried on the jet stream and have a discernible impact in the US/Canada?

  3. @JJ: MORE LIKELY THAN EVER! This stuff is so fascinating, even as much as I hope that no one will die because of it.

    @Provisions: As I understand, there is virtually no chance that significant radiation would reach the United States. Check out this Snopes debunking of a map released by the Australian Radiation Service.

    I'd also like to stress that despite the terrifying hype, even moderate doses of radiation are generally harmless. Eating a bunch of bananas (which contain radioactive potassium) while flying to Japan exposes you to to massively more radioactive conditions than normal ground background radiation, and people do both of these things all the time with no ill effects. The radioactivity emissions from Fukushima (measured right next to the plant) have severely spiked a couple of times, prompting evacuations, but for the most part have stayed in the range of eating 1-2 bananas a day for a year.

    Similarly, insufficient time has passed to measure increased cancer rates caused the Chernobyl disaster, but the radiation from that worst non-bomb release of radioactivity only killed around 28 people, many of whom were working directly on top of the reactor trying to put out fires and drop coolant into the ruptured core. Obviously Fukushima has the potential to grow into a public health catastrophe, but in many respects the radioactive emissions alone from a coal-fired power plant (yes, burning coal releases radioactivity) of comparable power operating for the last 30-40 years are worse than the radiation that has been released so far.

    That said, this is more of an argument against coal than fornuclear. As the president of the Federation of American Scientists recently noted in a blog post, having 30-50% of the energy in a country on a massive fault line come from nuclear energy is not exactly planning for success. Particularly when some of the older plants need AC power to run their coolant systems (though newer ones do not).

    In short: don't be afraid, just be concerned.

  4. Oh, that said, I wrote this post not realizing that Reactor Number 2's containment structure had likely been damaged by a hydrogen explosion, which greatly increases the chance of a high-level release of radiation.

  5. Interesting....How did the other reactors at Chernobyl keep working?? Weren't people banned from entering the zone of contamination?

  6. @Louise:

    Yep, though authorized workers were never banned completely. People are still largely forbidden to go near the plant: fully legal tourism of the zone of contamination (also awesomely known as the zone of alienation, or simply The Zone) only opened this year.

    In short, the Soviet Union couldn't handle shutting down all four almost brand-new reactors at that time, and the risk was deemed worth the reward. To give you a sense of the investment, the entire city of Pripyat, which is within the Zone adjascent to the power plant, was built primarily to house the reactor workers and their support personnel and families. In an attempt to wish away the the obvious design flaws, they initially blamed the meltdown on reactor worker error.

    I believe scientists and engineers still work in the facility today, even inside the sarcophagus. As I understand it, they must live primarily outside the Zone and only work staggered shifts in areas that have been highly contaminated. Here's what Wikipedia has to say:

    Any residential, civil or business activities in the zone are legally prohibited and punishable. The only officially recognized exceptions are the functioning of the Chernobyl nuclear power plant and scientific installations related to the studies of nuclear safety.

    Approximately 3,000 workers are employed within the Zone of Alienation. Employees technically do not live inside the zone, but work shifts. 75% of the workers work 4-3 shifts (four days on, three off) and 25% work 15 days on, 15 off, as of 2009. The duration of shifts is strictly counted regarding the person's pension and healthcare issues. Everyone employed within the zone is monitored for internal bioaccumulation of radioactive elements.

    The Chernobyl nuclear power plant is located inside the Zone of Alienation but is administered separately. Plant personnel, 3,800 workers as of 2009, reside primarily in Slavutych, a specially-built remote city in the Kiev Oblast, 45 km (28 mi) east of the accident site.

    BTW, Richard Rhodes's third book, Arsenels of Folly, deals closely with the accident and is my source for most of the Chernobyl-related info in this post. In addition to being fascinating for scientific and disaster-porn reasons, the disaster was also a major turning point in the cold war.

  7. Today's Boing Boing post re: Chernobyl: