I don't often write off-topic, but the images coming from Japan are just too troubling. I am not sure which images trouble more - those coming from Fukushima, those that came from Chernobyl or this video from Swiss TV:
What would happen if something like Fukushima or Chernobyl happened here in Switzerland? 800'000 workers were needed to contain Chernobyl; 50'000 of them have died of radiation sickness. The radiation in the Chernobyl reactor was so intense that even the robots failed.
Switzerland's population is only 7.4 million, of whom 2.5 Million are adult males, aged 20 to 60. If an accident on the scale of Chernobyl happened here, that would mean more than 1 Swiss in 10 -- or more likely, 1 adult male in 3 -- would be called into service and around 1 adult male in 30 would die. An area nearly the size of Switzerland would be rendered uninhabitable. Where would the rest of us go?
How can we expose ourselves to that kind of risk?
Either we need to get rid of nuclear power plants or we need a better Plan B.
On the way home from work a few days ago, I was wondering how would Star Trek solve this problem? I could almost hear LaForge screaming "Captain, I have to eject the warp core!" How could a nuclear power plant eject its core?
Sending it into space is not option -- too dangerous -- and beaming doesn't work either. So there is only one direction available: Down. Fortunately that is relatively easy to do. Gravity will do most of the work for you. (You can demonstrate this by jumping from a diving board, throwing something off a tall building, or letting a ball roll down a hill). You just need to prepare the reactor and path, so that the reactor core can fall or roll into a secure area on command.
The harder part is preparing the pathway and ensuring that there is enough material to isolate what is left of the reactor core and prevent the radiation and other products from contaminating our ecosystem. While this is not possible after a nuclear incident, an ejection could be prepared beforehand.
One approach for long term storage of radioactive materials is the so-called 'deep borehole.' The idea is to drop the waste down a very deep tube, say 5 km, then cap the tube with earth, rock and water to prevent leakage.
Why not build the reactor directly over a borehole? In the event of an emergency, the reactor core could be separated from its mountings and allowed to fall into the tube. The deployment might look something like this (click to enlarge):
Would this be sufficient to safely dispose of a reactor core? There is a natural precedent. A mine in Oklo, Gabon had been site of a natural U235 reaction. The remains of that reaction are still radioactive, but the sandstone around the uranium deposit contains the radiation.
Can we build a suitable borehole? The current record for a deep boreholes extend over 12'000 meters into the earth's crust! Obviously, an eject borehole would need to be substantially wider than existing boreholes for pumping oil or scientific research. The final resting site probably should be below all aquifers. And there are surely other issues and technical challenges. But there are precedents for the solution. And without a Plan B, nuclear power is just too dangerous.
Would this Plan B have helped in Japan? I don't think so. An earthquake is liable to leave the boreholes blocked or otherwise unusable. Which brings us to Plan C: If there is no viable Plan B for securely and quickly shutting a reactor and isolating it from our ecosystem, then then nuclear power is just too dangerous. Shut it down or don't build it in the first place!
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