ACCORDING to US nuclear expert, Mark Mervine, the Fukushima Daiichi nuclear power plant withstood the earthquake but the tsunami destroyed its backup power which is necessary for cooling the reactor. The situation is critical. Furthermore, there are another five reactors at that site that were in commercial operation.
Following is an extract from an interview recorded by Mr Mervine’s daughter, Eveyln.
Q: I guess the big question that everyone has today is, has the explosion or any of the damage, I guess there hasn’t been a lot of damage to the plant, it’s just overheating, do you think any of this is causing nuclear leakage and if so, is that a big problem?
A: So, I‘ve actually looked at the before and after picture from the explosion that’s available on the news and, in my opinion, they have an extremely serious situation at this nuclear power plant. So, my speculation is they were venting the steam in order to try and cool the reactor, unfortunately, without power they don’t have a lot of their normal instrumentation that they would have.
Q: So they can’t monitor things to the same degree –
A: They don’t even have their backup power, I mean they basically have the bare minimum of instrumentation provided by whatever battery power they have left. My guess is, and it was reported in the news that they had a hydrogen explosion, so they obviously had hydrogen and other gases that were generated, that built up to an explosive level and if you look at the photos the entire building surrounding the reactor, the only thing left of it is the steel frame, the whole building has collapsed. That would normally be called the auxiliary building, and that building actually does house a lot of the emergency systems for the reactor. So I think we have a very very serious situation at this power plant where the entire auxiliary building has been destroyed.
According to reports, the containment is intact, so if there has been any release of radioactivity, it has been very minor, to this point, but they have got to find a way to get some electricity, and cool that reactor. And the last report I saw said that there plan was to use seawater. So obviously, they’re going to get some temporary pumps, they’re going to use seawater, mixed with boron. Boron is a substance that will absorb neutrons, very similar to borax that you could go buy to wash your clothes with, that will keep the reactor from going critical again when they add the cold seawater. Even though the control rods have been fully inserted, when you add cold water, cold water is denser than warm water, and it can cause the neutrons that are still bouncing around the reactor to moderate, to a speed at which, (so moderate means slow down), they could strike the fuel and cause a fission.
We obviously don’t want any more fission because that generates more heat and we certainly don’t want the reactor to go critical because that generates a lot of heat. And, critical is not the bad word that you see in the news, where you say “Oh, reactor’s going critical!”; when it operates, it’s normally critical; all critical means is it has a self sustaining reaction, which is what you need to operate. What we wouldn’t want it to do is to go to a terminology called super-critical, that would be really bad. But in any event, when you add the cold water and you don’t add the boron, then you have the potential of causing the fission level to go up in the reactor and more heat to be generated, which you don’t want to do. This is beyond the last resort, to do this, at a nuclear plant.
Q: To use sea water to cool it –
A: I think they’re basically down to their last option here.
Q: So what do you think is the best case scenario for this plant, and added to that question, what is the worst case scenario?
A: I think the best case is that the military get the generators on-site with some emergency pumps and they’re able to rig up a cooling system to cool that reactor, to keep it cool, and they’ll have to cool it for several days before it gets to the point where the heat is decayed off. Obviously the plant is destroyed, and I’m sure it will have to be decommissioned. The question is how much additional damage is there at the site, because, there’s actually six nuclear reactors at that same site and two more that were planned or are under construction.
Q: I see, so this is just one that’s been failing.
A: This is just one of six reactors at that site that were in commercial operation.
Q: Oh that’s scary, so that there could be trouble with the other ones.
A: The question is, as a result of this explosion – has any damage occurred in any of the other, adjacent, reactors and also what is the situation of the additional reactors?
Q: Right, if they don’t cool them, it seems like this same thing could happen to them.
And also from the same interview…
And, that plant was automatically shut down, when the earthquake occurred, and for about the first hour, they were running on their diesel generator. Once a plant shuts down, it has two ways to get electricity, one is from the grid, and another is from emergency diesel generators that they have on site. In this case, because of the magnitude of the earthquake, the grid basically went dark, so they were operating on their diesel generators and everything was functioning as it should be. But then, based on news reports, about an hour after the earthquake and the shutdown, the tsunami hit, and flooded the plant, where the diesel generators were, and that caused them to lose their diesel generator power and reduced them to their emergency battery backup power only.
Q: And that wasn’t quite enough to have the cooling capability that they needed?
A: The emergency backup on the batteries gives them, you know, very very limited capabilities, so they were having a very difficult time keeping the plant cool.
Q: Do they sort of have to go to a smaller cooling system, smaller pumps and that sort of thing, that can be run off of their battery?
A: I don’t know the specifics of that plant and what they might have done in Japan. Obviously, Japan being in an earthquake zone probably had additional requirements for the plant that we wouldn’t have to have in other places around the world. But, in any event, based on news reports, they did have some type of cooling capability using their battery power, the problem of course is, the batteries are only good for a few hours.
Q: Yeah, the news reports said that the Japanese military was actually trying to get in replacement batteries to cool the plant, I’m sure they’ve continued that effort but I haven’t heard any update on that in the news.
A: So, the reports that I saw on the news said exactly that, they were trying to supply the plant with additional batteries and a portable diesel generator.
Q: Right, I hope they’re successful soon. So how are nuclear power plants in general built to withstand earthquakes and tsunamis? You may not know about this, since you work on power plants that are in more tectonically stable regions, but are there some specific requirements for natural disasters?
A: There are, and depending on what the worst case scenario would be anticipated for an earthquake, their requirements are different. So probably the best example I could give is, I once participated in an inspection of the Trojan nuclear power plant which was in Oregon. That plant has been shut down now, but compared to the plants that I had worked in Wisconsin and in Vermont they had a lot more requirements on them for earthquake protection. So the way you do that, there is a lot more supports for all the equipment, all kinds of hydraulic dampeners which allow the equipment to move back and forth without breaking. I know in Japan they have a requirement that all the plants have to be built on bedrock, so, they actually have to go down to bedrock in order to begin to build the supports of the plant. So, yeah, there’s numerous precautions that are taken and, like I said, there were probably additional backup system requirements that were required by the Japanese government, for those plants, being in an earthquake zone.
Q: Yeah but this was just such an enormous earthquake, I mean, I don’t think they’re released the official report yet, but this is probably in top five biggest earthquakes so even if they prepared for the absolute worst, this is something that really stressed all of their systems and backups, I imagine.
A: Well, I think really the key here was not so much the earthquake. By all reports, the plants functioned exactly as they were supposed to do in the earthquake, they shut down automatically, when the grid was lost their diesel generators started, and everything was fine. What really put us in the situation we’re in now is the tsunami as a result of the earthquake, but not the earthquake itself.