I am a retired Metallurgical and Nuclear engineer. I am quite familiar with the two first reactors built at Fukushima.
1)Most experts in fact have probably never been inside a nuclear plant, they are probably experts of nuclear reactions – not nuclear plants.
2) The GE mark I and II design is: compact, cheap and NOT safe. A number of Atomic Energy Commission experts have criticized these units since 1972 – the year after the first Fukushima reactor was installed.
3)The Fukushima units are BWR units, boiling water reactors, in which the reactor cooling water boils and leaves the reactor housing to a long loop to the turbines. The reactor concrete pad is reasonably thick and allows the reactor to “float” during a severe quake.
4) But the turbine building is on a completely different concrete pad. During the quake the two pads can move with respect to one another. This apparently broke the big pipes of the cooling system, the same pipes that are used by the emergence pumps. (Nice cheap compact design)
5) At this point all the redundant (bad design to save money) pumps count for nothing because the pipes are broken.
6) In 1972 the company I worked for negotiated for almost a year to install a competitive, safer and more expensive design for the second reactor.
7) The Japanese are technically competent, and quite rigorous regarding maintenance – but are even more hard headed than either Germans or Americans. At the time a young Japanese engineer told me that the Japanese had already decided on a design and to accept our design would mean that they would have to admit to a mistake on the first reactor.
I was informed unofficially that the primary decision makers would die before admitting that our design was better, and unfortunately take several thousand people with them.
9) A simple fact that no one seems to be sufficiently competent to understand: In a high risk environment of rupture of the cooling piping (as a sub or war ship or highly seismic area) a PWR Pressurized Water Reactor is indicated. For a situation with a VERY low risk of cooling pipe rupture, A BWR Boiling Water Reactor is ok, but in my opinion not the Mark I or Mark II designs.
10) The Japanese are much worse than Americans in hiding the real facts and cover ups of every type to avoid being blamed for screwing up and “losing face”.
11) Real honest to goodness “drop dead” safe nuclear plants can be constructed – but they are not from the lowest bidder and are probably not consistent with high company profit and or back room politics.
12) I am sorry for the Japanese people, but they paid for a half assed design and that is what they got.
13) The top of the secondary containment building, contains the “spent fuel” pools (check out the diagram). Has any expert explained how the top of the building can blow off and the primary and secondary containment remain ok???
14) Well, I’ll tell you. The Mark I design is very compact, and the tanks on either side of the secondary containment building (near the top of the reactor)are the spent fuel pools. Pools, as in concrete tanks, but not as robust as the secondary containment. During the quake, the cooling pipes to the pool were also ruptured, maybe even the tanks cracked. The water level lowered either due to a leak and or boiling in the tanks. Boiling is not just bubbling, it is the separation of the hydrogen and oxygen atoms forming the water.
15) So when the top of the building (simple metal construction)fills with hydrogen and the pressure increases, it explodes due to pressure. The flame you could see in the explosion is the hydrogen recombining with atmospheric oxygen and creating a fast flame front or a slow molecular explosion, having nothing to do with the reactor or it’s contents.
16)The reactors however can continue their progression toward a melt down, but while possible, less likely.
17) I hope this at least partially explains how we got here and why even considering the seriousness, is not a reason to automatically be anti-nuke. Anti-political for a technical issue is good sense. Purchase cost and utilization cost are not the same thing – either in dollars or safety
Regards
