Part of the problem in these (and other) designs is the classification of “100 year events” and “500 year events” and so on relies on VERY poor modeling and knowledge of just how frequently these events happen.
Add to that the less than perfect modeling with math and we get poor requirements.
I still like how the financial boys on Wall Street had models that showed that the rate of market decline in October, 2008 couldn’t happen more than once in 4 billion years’ worth of market time (ie, it was *highly* improbable), yet we had two such declines in one week. That’s an example of poor modeling.
Consider that it was only recently that scientists admitted that mariners have been right all along and not merely telling tall sea tales: there are such things as rogue waves, waves 60’ high that come out of nowhere and can break a ship in half or roll it. Mariners have been saying this for years, and only with some very new approaches has science confirmed that “Yes, this can happen” and apparently off the coast of S. Africa, it happens often enough to make you sit up and take notice.
In Japan, the issue is one of modeling quake frequency and duration. Some stuff I’ve now been reading is about quake severity and frequency in Japan. New research indicates that severe quakes tend to ‘cluster’ in time in Japan, with long periods of ‘relative’ calm (when your big quakes are 8’s, 6’s look relatively calm) in between.
The central problem for civil engineers in Japan is that they have only 100 years (plus or minus) of really quantified data on which to base models. Coming up with a “1,000 year” design based on this paucity of data isn’t going to be easy.
And that modeling was even worse 40 years ago...
but it was all they had to go on. Assumed risk.
I hate to say it this way, but there are times when one looks at the specs, plans, and ER and say if that 100 year event happens...this is going to be a dot on the graph.
Things improved in 40 years. The only thing left behind in the time warp are these old reactors. And if one probes really deeply into why that is...one finds the environmental movement at the heart of stagnating innovation.