The Tokyo Electric Power Co., TEPCO, has estimated the extent of the melt through of the nuclear fuel at the crippled reactors. It is based on the simulation by computer. The worset case seemed to have occured at the first reactor. According to their analysis, the melt nuclear fuel got through the reactor vessel down to about 13 feet above the the outer containment base.
Hydrogen explosions have occured at three of five nuclear power plants, which has definitely caused the terrible fallout all over. It is not known how hydrogen produced at the nuclear fuel surface has gone through not only the reactor vessel but also the outer containment, that was prerequisite for the explosion. I guess the fuel melt through those structures, which could release the hydrogen gas freely into the room, and it has also caused the acclereation of the hydrogen production. Of course, the tubing structures around the reactor must be destroyed by the earth quake before that. It might facilitate the release of hydrogen gas as well.
We should remeber that the government spokesman used to announce repeatedly there had not been any melt down occuring there for a week or so after the accident happened. The TEPCO as well as the government have been revealed to be aware of the high possibility of the melt through phenomenon at that time. They have been inclined to announce their estimate of the situation in the better way than it really is.
We must suspect the melt through is going on in much worse way. The above mentioned estimate must be biased to the better way by TEPCO. Then we should consider the sequel to this worse possibility. I suspect there have been the melt fuel getting through through the base concrete structure. If not getting through, it must has been penetrating through the concrete or the cracks of the base. It might result in the contamination of the ground water. If this occurs in reality, there has been much contamination into the ocean going on. It is not reported how the underground water beneath the nuclear power plants are contaminated. It should be urgently investigated. If such contamination is suspected, any procedure to prevent it such as constructing metal wall underground should be taken.