Reply #207: The drywell on these units is Carbon Steel

[divvy]

The drywell on these Units is carbon steel with some concrete poured in the bottom of it. If the core melted through the 6+" stainless steel RX vessel, it would make quick work of the drywell. I am told that these Units did not have a "core catcher" installed below the reactor. This is a large casting added in later Mark I plants (my plant had it). If you Google "core catcher nuclear," you will find more about this at Wikipedia. If the core was still in the containment, you wouldn't necessarily have a large uncontrolled release. Since they believe they do from U2, it would seem like the conclusion that the core is through the RX and inside the drywell is wrong. It is probably already through the steel drywell and into the RX building foundation. Under these circumstances, putting water into the vessel is not particularly helpful. It is probably spilling out of the breached drywall and causing the nasty water in the building. To say that this is bad news is kind of a gross understatement. The real danger in my mind is that the total meltdown of even one Unit may make it very difficult to save the other Units, because of crazy high dose and contamination levels onsite. Japan is kind of a long, skinny island. They should consider evacuating the northern part of the country in case it should become impossible to do so later. If there is a plan to get this under control, I don't see it. Today, there was a lot of concern about detecting plutonium at the site. These were small amounts and has more of a psychological impact than a real threat. There is plenty of danger in Japan, but detecting small amounts of plutonium is not high on the list of dangers.