There’s a lot of speculation out there about how much you can plan for accidents. And not just in the nuclear industry, but in every industry. The basic concept runs like this: “We’re going to do X, but X could be dangerous and could hurt people so what is the worst thing that can happen while we’re doing X, we’ll plan for that and we should be covered for all situations.” Sounds pretty logical right? I mean if you can plan for the worst thing ever then you can cover everything less than that. Well, there are two hitches to that logic strain.
Firstly you have to define what the Worst Thing Ever is. Given any X the Worst Thing Ever can be pretty freakin crazy. Let’s say X is driving a railroad train. What is the Worst Thing Ever, well obviously another train going the opposite way on the tracks right? No actually, the worst thing is that the other train going the opposite direction is filled with some chemical that will both explode on contact and leech out to the environment killing everything in it’s path. So is that the worst thing? No actually, it would be even worse if both trains were carrying this chemical. So that’s the worst thing right? Nope, now the collision of the trains occurs inside a train station, in a major metropolitan city, with both an airport and seaport next door. And so it goes, on and on, until you’re involving meteors and aliens and godzilla. But lets say that eventually you get to the point where you can get down to a not-so-insane Worst Thing Ever. So you build your plan around ensuring that if the Worst Thing Ever happens that you’ll be able to compensate for it.
So you’re good right? Nothing besides the Worst Thing Ever will actually happen right? Well, no, actually. The reality of the situation is that you’ve only just planned for the Worst Things Ever. You have, basically, left out all those other smaller, but still really bad, things. All the things that are only semi-catastrophic. All the things that don’t kill everyone, but still kill a lot of people. By assuming that planning for the Worst Thing Ever will cover you in all situations you leave yourself open to damage from much smaller, but much more conceivable situations.
The fact of the matter is, that you not only have to plan for the Worth Thing Ever, but for all bad things that could possibly happen, and you know what happens when you do that right? Well, you can’t. You can’t possibly imagine all the potential scenarios that could damage whatever it is you’re doing. So you plan for as many of them as you possibly can.
Now, this is how it all went down in the nuclear industry. Back in the day, read the 1940’s, it was determined that the Worst Thing Ever in a nuclear reactor was a combination of two things: a large scale disaster combined with a double end guillotine shear break of one of the 30-40 inch diameter pipes that connect to the reactor. So the analysis of the safety features went in two directions. 1) Planning to ensure that everything in the plant works in the event of a large scale disaster and 2) Planning to ensure that if the pipe suddenly falls off of the reactor that there are other ways to put water back into the reactor. Large scale disaster planning was based on the worst disasters that had ever happened in the vicinity of the plant: Earthquakes, tornadoes, hurricanes, tsunamis, fires, etc were all considered and the plant was built to withstand the worst of those that had happened, or a baseline in the case that it had never happened (Earthquakes for instant don’t happen so often in the Southeast U.S.). Planning to ensure that water could still get into the reactor even with what amounted to a large hole in the vessel went into designing series-es of redundant systems, all of which could get enough water into the reactor and run during a station blackout.
However, everyone knows, that even when you plan for the worst, things can still get worse. Through the 70’s and 80’s plants added system after system and retrofit after retrofit in order to deal with what were discovered to be potential, and in some cases actual, weaknesses in the plant designs. What happened in Fukushima was beyond that though. Fukushima was the result of two almost concurrent natural disasters, both of which were beyond the design basis of the plant. The plants survived the Earthquake, which was a full couple of Richter points above design basis, and the Richter scale is logarithmic, not linear. However, three of them did not survive the subsequent five story tall tsunami that was roughly twice as tall as the tsunami sea wall. And unfortunately the water managed to take advantage of a design flaw, the diesel engines, which would supply power in the event of a station blackout, were housed underground. This made them very safe from earthquakes. It however made them extra vulnerable to tsunamis. So there you have it, the tsunami, which basically slammed into the reactor buildings after it rode over the wall, did sufficient damage to the plant to knock out the cooling systems and eventually the cores melted, to some degree or other.
Now saying all that: There was no giant, unmitigated, release of radiation that contaminated the area for years to come. There was no loss of life due to radiation. The core, even melted, in majority remained inside the reactor vessels. The ultimate point is this, if we can’t produce nuclear power while keeping people safe then there is no reason to produce power that way. So far, everyone is pretty much safe, at least safer than the people who will get sick from the biomedical waste washing up on shore due to flooded hospitals. Safer than the people who will get sick from the chemicals that were leached out of chemical plants engulfed in the tsunami. If we’re willing, as a society, to put up with major ecological disasters due to unprotected chemical and oil plants then I think we’re willing, as a society, to allow nuclear power to be produced in the overprotected, safe manner in which it is produced, especially after proving that it can be taken far beyond design basis and still hold strong.
