Here's the key bit from Robert X. Cringely's second (and last) post on the Japanese nuclear tragedy:
These Japanese nuclear accidents come down to the simple fact that nobody back in the 1960s designed nuclear plants to run for 40 years then go through an 8.9 earthquake. Nor are today’s nuclear plants probably designed to that standard, which means Japan is facing what will by necessity be a significantly different nuclear future.By definition the future surprises us. We can't know in detail what will happen. But the tsunami was one of the "unknown knowns" that engineers had to design for. The problem was that without relevant experience, cost pressures overtook prudence and reactor designs didn't include enough safety. This can be corrected. Sadly most people think in terms of black or what. This nuclear failure means that most people will say "no!" to nuclear. But the real world is in shades of gray. Even "safe" energy kills. All designs must include trade-offs. What this disaster teaches us is that nuclear reactors need a better safety design for natural catastrophes like 9.0 earthquakes and tsunamis.
We’ll see rolling blackouts for months, maybe years, in Japan and the new nuclear plants that replace those old nuclear plants will be vastly different, too. If I were to predict a clear winner in Japan’s new nuclear future it would be Toshiba with its innovative 4S (Super Safe Small and Simple) reactors.
Japan needs increased generating capacity fast. They would like to replace nuclear with nuclear. But the new plants also have to show they can survive an 8.9 earthquake and reduce the number of critical failure points. Toshiba’s 4S reactors, which have been around for several years now, though not yet commercially successful, do all that quite easily.
4S reactor cores are like nuclear building blocks, built on a factory production line and transported by truck to be installed 30 meters under the ground. Each 4S puts out 10 megawatts of electricity or enough for 2000 Japanese homes. Following this path means the lost 1000 megawatt reactors will need 100 4S’s each to replace them or a total of 1200 4S reactors. 4S’s are fueled at the factory, put in place to run for 20 years then returned to the factory for refueling. They are sodium-cooled and pretty darned impossible to melt down. If the cooling system is compromised they automatically shut down and just sit there in a block of sodium.
The biggest problem facing the 4S has been regulatory approvals, which would normally take in aggregate 100 times as long (and cost 100 times as much) if done the same way as a larger nuclear plant. That’s where this earthquake will probably change everything, at least in Japan, where the process will be streamlined almost to nothing with a 4S soon stashed under every power substation giving Japan a smart grid in the process.