Per Peterson, chair of the department of nuclear engineering at UC Berkeley:The primary containment vessel, it’s being left submerged in salty water and is corroding. So by not making prudent decisions today about what water must be discharged and what water can be safely discharged and instead just storing it all, the risk is it will make it in the longer term much less likely that it will be possible to get the damaged fuel out. And so by misdirecting a lot of the effort to do things that don’t reduce risk significantly, they’re creating in Japan a much larger probability that in the end it will not be possible to get the damaged fuel out, and they will have to manage those plants at that site for millennia going into the future.
Tom Ashbrook, Host: Millennia, that means thousands of years. […]
Peterson: Continue to flush water through these reactors to keep them cool and also you want to be trying to flush out all of that salt that was injected into these reactors, which right now is contributing to the corrosion of these primary containment vessels that if they don’t survive it will become challenging or impossible to get the damaged fuel out.
The China syndrome (loss-of-coolant accident) is a fictional nuclear reactor operations accident characterized by the severe meltdown of the core components of the reactor, which then burn through the containment vessel and the housing building, then notionally through the crust and body of the Earth until reaching the other side, which in the United States is jokingly referred to as being China.
In reality under a complete loss of coolant scenario the fast erosion phase of the concrete basement lasts for about an hour and progresses into about one meter depth, then slows to several centimeters per hour, and stops completely when the corium melt cools below the decomposition temperature of concrete (about 1100 °C). Complete melt-through can occur in several days even through several meters of concrete; the corium then penetrates several meters into the underlying soil, spreads around, cools and solidifies. 
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However in case of Fukushima incident this design also at least partially failed: large amounts of highly radioactive water were produced and nuclear fuel has possibly melted through the base of the pressure vessels.
Cooling will take quite a while, until the natural decay heat of the corium reduces to the point where natural convection and conduction of heat to the containment walls and re-radiation of heat from the containment allows for water spray systems to be shut down and the reactor put into safe storage. The containment can be sealed with release of extremely limited offsite radioactivity and release of pressure within the containment. After a number of years for fission products to decay - probably around a decade - the containment can be reopened for decontamination and demolition.
Originally posted by Orygun
What most don't understand, is that Fukishima has now become Japan's answer to Hiroshima and Nagasaki and they are attacking the US via the radiation released from this site. Yes, they soon will own the Pacific as evidenced by all the double layered metal ships they are building, almost as if they knew in advance that this would happen. They probably had something to do with setting off the earthquakes and tsunami's that caused all this. Makes sense yes? Besides, if a fish has 3 eyes, it means we have one more juicy eye for our fish soup, and you thought this was all bad.