Fukushima apocalypse: Years of ‘duct tape fixes’ could result in ‘millions of deaths’

[PamW]

39. Criticality is NOT a possibility

quadrature,

As you point out; we are talking about fuel that has been depleted in U-235. Spent fuel has been in the reactor for about 3 cycles ( ~3 years ) before it is discharged. So the reactor was operating with the spent fuel just before it was discharged as spent fuel; but ONLY because it was in a core with fuel that was depleted less. One third of the core had been burned for 2 cycles, and one-third had been burned for 1 cycle. It was only because 2/3 of the core was less depleted that the reactor could operate with fuel that had been burned 3 cycles.

The water in the spent fuel pool is borated. Boron is a neutron absorber, and "poisons" the fission reaction.

The spent assemblies are in racks that also contain neutron absorbers. With all those neutron absorbers; the fission reaction is well "poisoned".

Some would argue that the fuel is damaged / melted. However, that actually works AGAINST having a criticality. See my explanation at:

http://www.democraticunderground.com/112756727#post20

The good thing about science is that it is true, whether or not you believe in it.
--Neil deGrasse Tyson

PamW