I have to pose a pretty simple question here, but I'll throw in a couple of facts first;
a.) The fuel used is called Mox, which is a mix of plutonium, zircon and other mediating elements, and
b. ) Plutonium has a critical mass of about 16kg's (some articles state 4kg or less but that is with a trigger)
Critical mass is defined as the point when enough mass is accumulated self bombardment occurs and results in a nuclear reaction that causes a nuclear
Critical Mass (def)
The minimum amount of fissile material that can sustain a nuclear chain reaction under a given set of conditions the minimum amount or number
required for something to happen, begin, etc.
About Plutonium Bombs
Now at some point, with melted Mox rods, their individual compont materials will separate and settle, stratify into molten layers if you will.
The Question: How much actual plutonium is in each rod and how many rods per reactor?
Once melting and stratification starts to occur, there is constantly increasing mass added to each layer over time based on material availability (the
rods). Eventually, if the amount of p239 is of sufficient quantity in each rod, the stratified p239 layer will reach and/or exceed the critical mass
"at rest" level of 16kg. When this happens an uncontrolled nuclear reaction has a high probability of occuring, just like an atomic bomb.
There are a couple of problems;
The containment vessel will not contain this kind of explosion
The resulting explosion will send a few pounds (at least) of plutonium into the atmosphere. One pound distributed evenly amongst seven billion people
will kill them all.
The conclusion is simple, since the rods are made up of plutonium plus mediators, this material has to be prevented from melting and achieving
critical mass through stratification, otherwise, we're all screwed.
This scenario has two outcomes, it goes very bad or it goes ELE bad imho. All we can do is wait and see.
Cheers - Dave