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When I see a story like this, it reminds me that the events in Japan represent the biggest PR challenge the nuclear industry has faced in many years. Fifty bil
by marze 16y ago
When I see a story like this, it reminds me that the events in Japan represent the biggest PR challenge the nuclear industry has faced in many years. Fifty billion dollars of nuclear reactor US taxpayer-backed loan guarantees hang in the balance.
The industry has been working for the past few decades to rehabilitate the image of nuclear power after Chernobyl and Three Mile Island, and now they have to contend with videos of a 1/2 mile tall mushroom cloud over a Japanese reactor and the continuing press coverage. Talk about challenging.
I think the HN community may have difficulty appreciating the challenges of nuclear reactor design because it is so different from software. In software, you have known bugs and unknown bugs. Once you've got the known bugs down to a low enough level and aren't finding too many new ones, you might release. The consequences of a bug is generally not too bad, certainly not on the order of making 800 square miles of real estate worthless, for example.
In engineering a nuclear plant, you have 90 tons of nuclear fuel generating 3,000,000,000 J of heat every second. The only reason it doesn't immediately turn into a big bubbling blob of molten uranium is that pumps the size of SUVs are pumping water over the fuel and removing all that heat. Every nuclear plant in the world is one minute from 90 tons of fuel melting into the basement if the water flow stops and fall-back systems fail. Fortunately, the engineering on these plants is done extremely carefully, with multiple independent systems in place to prevent exactly this by halting the nuclear chain reactions with neutron absorbing rods as well as by ensuring the flow of cooling water.
However, the events in Japan exposed an "unknown bug" in the design, that if you flood the basements of the plants with water you can lose backup power and coolant flow. While this particular "bug" is relatively easy to correct, it is a reminder that other unknown bugs may exist waiting to be exposed by other unexpected sets of circumstances.
It is good to remember Richard Feynman's quote about the space shuttle Challenger disaster, "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled."
- WalterBright 16y agoThere are a lot of parallels with airliner design. From reading articles about the nuke plant design, I think they could learn a lot from aviation engineers about how to build safe systems.
- gnosis 16y agoI'm sure they know how to build safe systems. But equally important is whether they'll spend the money necessary to make them safe, or if they'll sacrifice safety in the name of profit.
- jschrf 16y agoOne thing that blows my mind with the Fukushima plant (and presumably others) is that the spent fuel pond is seemingly built above ground. Wouldn't you want this to be at the very bottom of the reactor building, so that water could collect in it in an emergency situation like in Fukushima where water is pumped in from above? Maybe this is (was) one of the unknowns/unthoughtofs that you mention. As an aside, if no one's seen the excellent Battle for Chernobyl, I highly recommend it. It details the insane clean-up operation that took place after the Chernobyl disaster. It's on Google Video.
- gamble 16y agoThe plant is built like that so spent fuel can be lifted out of the reactor and placed directly in the pool using one crane. A more secure spent-fuel pool would have required more elaborate fuel handling, thus a more expensive design. Also, when these plants were built I don't think they anticipated the spent-fuel pools would become long-term storage. There was the assumption that centralized nuclear waste disposal sites would be built and the pools would only store waste until it was safe to transfer.
- jorangreef 16y agoThis is often the case, a plan for the removal of waste to a disposal site is promised, and then once the plant is built, and the contractors have been paid, nothing happens. New plants are then built, it is said that a disposal plan will be put into effect, and still these plans never materialize.
- marze 16y agoPutting the fuel storage pool on the fifth floor of the reactor does seem questionable, especially given the violence of the explosion at reactor 3. Another "unknown bug" exposed by these events will probably motivate mitigating the risk of hydrogen explosions from hydrogen generated in a partial meltdown. As you can see in the second picture in this link, http://news.ycombinator.com/item?id=2399676 http://news.ycombinator.com/item?id=2399676 the force of the explosion crushed the concrete structure of the adjacent reactor building, and launched enough material into the air that it created holes 60 feet in diameter in the roof of the turbine building when it came down. This was not anticipated; if it were the reactors would have been constructed further apart. The spent fuel rods must be actively cooled for many months after they are removed from the reactor due to heat-generating radioactive daughter products. Since the pools holding them have either boiled away due to the absence of active cooling or drained into the basement due to damage, it is likely these rods overheated. Japanese authorities have mentioned the possibility of "re-criticality", which would be a bad thing, especially in a fuel pond with no containment whatsoever. There will probably be many lessons gained from these events that will be used to reduce risks in other operating reactors and future designs.
- phlux 16y agoSo, how is nuclear fuel transported from wherever is it manufactured to the reactor? Why cant that process be implemented to transfer the fuel out of the reactor?
- asharp 16y agoIf memory serves, the problem is that it is politically impossible to create some area to place the waste fuel. ie. it would be much safer to move the spent fuel out of the reactor, however there is nowhere for it to go to.
- phlux 16y agoI am talking about taking it out of the damaged reactor and into a sound containment/cooling unit. That is far better politically than letting it sit in a damaged structure leaking radiation everywhere. Sometimes nations need to STFU about politics and get shit done.
- billmcneale 16y agoNumber of casualties from nuclear plant accidents: a few thousands. Number of casualties from coal mining accidents this past century [2]: 100,000. That's accidents in coal mines alone, not even counting lung diseases and similar. The fact that it takes a 9.0 tsunami after forty years of complete absence of nuclear accidents to bring this to the front page should be indication enough that nuclear is not just safer than most of the other energy production techniques, it's also the one that has the highest energy rendering. Any Green voter who's done their homework should be voting for more energy to be generated by nuclear plants, not less. [2] http://en.wikipedia.org/wiki/Coal_mining http://en.wikipedia.org/wiki/Coal_mining
- lispm 16y agoI vote for neither.
- asharp 16y agoWhat would you suggest? Keeping in mind that basically all renewable sources sans hydroelectric can't be used to provide baseload power and hydroelectric power both has very few potential locations (most of which are in use) and has the nasty failure condition of washing away a good portion of the countryside.
- Ratfish 16y agoI know it's easy to suggest as a New Zealander (lots of mountains, lots of rain, and not that many people), but that hydro you mention is ace, wish all our power came from it.
- ctman 16y agoDams aren't impervious to killing lots of people either: http://en.wikipedia.org/wiki/Vajont_Dam http://en.wikipedia.org/wiki/Vajont_Dam http://en.wikipedia.org/wiki/Banqiao_Dam http://en.wikipedia.org/wiki/Banqiao_Dam 2 incidents in 15 years: 175,000+ killed. Plus they emit methane in huge quantities (from the decay of plant materiel in the reservoir) I would bet that for New Zealand the best form of energy would be geothermal even though the long-term effect studies around cooling the earth's crust are lacking.
- jbert 16y agoOut if interest, the way I'd try and design a fail-safe solution would be to have meltdown trigger a shutdown. Picture a bunch of large, heat-proof (ceramic?) test-tubes, with their bases apart but their openings together. Put that underneath the core - then if it melts and drops down, small pieces of it flow in different directions - until you've got a sub-critical amount in each one - so the fission reaction stops. Anything which requires active prevention of fission seems odd, presumably passive is better?
- asharp 16y agoI would have a look at pebble bed reactors, molten salt reactors and heavy water moderated reactors. long story short, the designs exist, we just can't seem to get rid of the old ones that are currently built and we can't seem to get the new designs built in any sort of scale.
- GFischer 16y agoThe R&D costs for those are HUGE, as they are unproven, the countries like mine (Uruguay) that are looking into building new power plants don't want that, we want proven designs.
- jorangreef 16y agoThe way I'd try and design a fail-safe solution would be not to design it in the first place. No one is forcing us to build these things. But government contracts are lucrative and contractors exist.
- jarek 16y agoNo one is forcing you. A lot of people just think refrigeration is awfully nice to have.
- jorangreef 16y agoWe will all be called to account for every careless word we have spoken.