The Tsunami in the ocean was only a little over four meters in height. Just like a wave that washes up on the sandy sea shore, the run up on the beach usually far exceeds the swell height. There was an estimated run up on Fukushima that exceeded forty feet. What is amazing about this is that Japanese history has numerous accounts of run ups well in excess of 40 feet from tsunamis. It all depends upon where in the ocean the tsunami originated. The fact that the engineers did not prepare for a forty (or more) foot wave is indicative of structural engineers not understanding what a swell in the ocean can do when it "runs up on land." Some thing was seriously wrong with that site engineering. Compound that with the fact that the Emergency Diesel Generators were placed in low spots in the turbine buildings for each reactor, and you know that somebody was seriously lacking in gray matter when it comes to site engineering. The Emergency Diesel Generators are there in case of a scram of the reactor. A scram, the insertion of the Boron Rods to shut down the nuclear reaction is automatically programed into the computers that operate the reactor in a case of an earthquake. One of the considerations for the scram is the fact that the electrical generating Turbine Generator (what the Nuclear Reactor plant is there for in the first place) needs to be protected from having the turbine blades destroyed as the turbine is shaking up and down while steam is still entering the blades. That can cause severe damage to the turbine, so the main steam piping has a shutdown valve in it that stops the steam from reaching the turbine and diverts the steam directly to the condenser under the turbine. Flowing through the pipes of the condenser is sea water that carries the sudden surge of heat to the ocean. Because the reactor is not needed to heat up the ocean there is a rapid insertion of the Boron Rods and the Reactor starts its slow shut down phase. Something in excess of 94% of the heat from the fissioning of enriched Uranium is quickly stopped because the boron has a great affinity for grabbing neutrons and stopping the nuclear fissioning reaction. That drop in power is tremendous when you consider the heat generated at full power down to five or six percent that gradually slows down over days. Still that excess heat has to be carried to the condenser or it can start doing damage to the Reactor Fuel Rods (which are not the Boron Rods - Two different things entirely.) You need pumps to pump the sea water through the condenser and you need pumps to pump the condensed steam (condensate) that was dumped to the condenser back to the reactor where it can be heated up and turned into steam to be dumped into the condenser to continue the cycle of heating the ocean. Unfortunately, at Fukushima their Emergency Generator electricity was shut off about a half hour after the Earthquake stopped shaking when a 40 foot wave swamped the Turbine buildings and shorted out the condensate pumps, the sea water pumps and all of the instrumentation for the reactors. Instrumentation? Yep, those same engineers who screwed up the site layout with the diesel generators down where they could be douched by the ocean also ran all of their local power and instrumentation cables underground where they were standing in feet of ocean water thirty to forty years after they were installed. They do not work too well when the insulation is brittle and the sea water shorts them out. Amazing stupidity! Absolutely amazing. Well, with no pumps to remove the heat that the Uranium Fuel rods were generating, they started to melt down. (There is mention of battery backup, but after a short while it was useless). My guess is that the Uranium Rods in Reactors One, Two and Three were well melted by March 12th, the day after the tsunami. They might be 100 percent melted or only 90 percent, but the fact of the matter is that they are melted. The only issue after that is the simple fact that the melted Uranium and Zirconium cladding of the fuel rods pools down at the bottom of the reactor and has the capacity to eat its way through the bottom of the metal (usually nickle-iron alloy - Inconel) Reactor vessel. When it does this, they give it a name - Corium. Corium (with a slightly different composition) was flowing everywhere at Chernobyl and it would only stand to reason that it was flowing in Fukushima. Just like at Chernobyl, it probably melted a lot of metal wherever it pooled. Over the course of the next few days after March 12th, Reactor Two and Reactor Three lost pressure. That means holes somehow opened in the reactor or the reactor piping. A good guess would be that the corium had something to do with this. Numerous posters to the physics forums around the internet have been talking about a nuclear explosion at Reactor Three three days after the earthquake. I am not convinced that is right for the simple fact that the radioactive particulate measured in proximity to Reactor Three is not as high as that around Reactor Two. Reactor Three had a Big "dirty" explosion while there were lesser explosions in Reactor One and Four (even though there was no fuel in Reactor Four's Vessel) The explosions in Reactor One and Four were clearly Hydrogen Gas explosions, but the explosion in Three was something else. I think (theory only) that the Corium (Ten Tons of it or more at 2000 degrees Fahrenheit.) ate and fell through the bottom of the reactor vessel into a massive pool of water in the concrete containment structure that is built around the reactor. That sudden flashing to steam was the source of the explosion. That steam carried some of the Uranium and Plutonium and other radioactive materials from the fission of the fuel rods into the atmosphere, but not contaminate the area around Reactor Three as heavily as an actual nuclear explosion of the stored fuel rods at Reactor three. What do you think? The only way that could have been a nuclear explosion was if the Japanese were not telling us the truth about their radiation surveys of the Reactor sites. Again, the site contamination was not indicative of a nuclear explosion but was indicative of ruptured fuel rods and contaminated water and particulate from contact with Corium. Everything is getting royally screwed up. Weeks ago they were reporting that they were pumping sea water into the reactors. At that time I questioned that report. To pump sea water into a reactor with a melting core without massive additions of boron could result in criticality. Boron is usually in the control rods because it scarfs up neutrons and makes it difficult to sustain a reaction in the uranium. When the core melts it is assumed that the boron control rods melt also. the only problem with that is that Boron dissolves in the hot water of the reactor and forms boric acid. If they were flushing the reactor with sea water they were effectively flushing the boron from the reactor. When I posted on the various physics and science boards of my fear I was told that the Japanese would not be that stupid. Guess what? And then they wondered why there was a BLUE GLOW over the reactor site?! Amazing!