The nuclear industry is keen on coming up with probabilistic risk assessments that show that a serious accident at a nuclear power plant can only happen every 20,000 years or so (admittedly this number is from a somewhat outdated report from 1974). Apparently, this is supposed to keep people’s minds at ease. But it shouldn’t:
This does not mean that once Chernobyl has happened, mankind will be safe for 20 millennia. It’s just statistical, so two accidents could happen in consecutive years (although according to these statistics, the next accident would then be – again statistically – 40,000 years away).
- If you read carefully, you will notice that these statistics use “reactor years” instead of “years”. A reactor year is one year of a reactor’s activity, so if your country has 20 active nuclear reactors, the probability of a serious accident is already 1 in every 1,000 years.
- It doesn’t take into account the slow deaths caused by constant radiation and increased rates of cancer in the areas surrounding a nuclear power plant.
But I have a much more general problem with these risk assessments: I just don’t believe that anyone can predict the safety for the next 20,000 years of a technology that has been around for 60 years. I think this is beyond the capability of any statistical model.
I have recently been thinking about our abilities to predict the risks of technologies because I had just come across a study by NASA’s Space Shuttle Safety and Mission Assurance Office that examined the risk of the first Space Shuttle missions and found that these were actually 10 times more dangerous than the current Space Shuttle flights.
Especially in light of the recent catastrophe in Fukushima where the possibility of a combined earthquake and tsunami had apparently not been considered (which in itself is a bit odd, considering that Japan is [a] an island that is [b] quite prone to earthquakes], this report by NASA provides valuable lessons for the risk assessment of nuclear power:
- The first Space Shuttle missions (in the 1970s) were ten times as dangerous as the current ones. We have many nuclear power plants currently active that are just as old. A scary thought.
- The main reason why later missions became less dangerous was that each mission learnt from the previous one. Nuclear power plants however are being used for decades, without any changes to the reactor’s design. Because a nuclear reactor is expensive to plan and build, but relatively easy to run, the nuclear industry has an incentive to squeeze as many years as possible out of each reactor.
- The biggest improvements in safety only followed what NASA calls “major events”, meaning an explosion with lethal consequences. This leads one to assume again that we are not capable of grasping all the risks that are technology-inherent, unless they are being pointed out to us by actual catastrophes.
And then there is of course still one fundamental difference: If a space shuttle explodes, the astronauts die. That is sad, but they had accepted that risk. – The radiation from a nuclear power plant however kills much more indiscriminately.