Canadian Nuclear Scientist: Another, even more dangerous possibility than fire at Spent Fuel Pool No. 4 — Re-initiation of chain reaction can occur if fuel rods move slightly, an “accidental criticality”
April 29th, 2012
Title: Why Nuclear Scientists Have Missed the Danger of Spent Fuel Pools
Source: Akio Matsumura
Author: Gordon Edwards
Date: Jan. 23, 2012
You asked me why there has been so little warning from the “nuclear establishment” (TEPCO and the regulatory agency) about the potential for catastrophic accidents involving the spent fuel pool in reactor number 4.
In addition to the possibility of zirconium fires (which have for a long time been almost completely overlooked by nuclear engineers and regulators) there is another, even more dangerous possibility. An alteration in the geometry of the spent fuel in the pool, by which the separation between the spent fuel rods is slightly but significantly reduced, can lead to re-initiation of the chain reaction in the pool.
This “accidental criticality” will not only drive the temperature up rapidly, but will also replenish the supply of short-lived heat-producing fission products, accelerating the damage to the fuel, magnifying the heat loading, increasing the probability of a fuel pool meltdown, and vastly increasing the atmospheric releases of radioactivity.
It has been a standard practice in the nuclear industry to avoid consideration of all of these possibilities, based on the assumption that there will be “lots of time” to react to any emergency involving the spent fuel pool, as it will normally take days for the spent fuel to reach the melting point and it will be a “simple matter” to refill the pools with water if necessary.
This ignores the fact that major structural damage may make it impossible to approach the spent fuel pool due to the lethal levels of gamma radiation emanating from the spent fuel once the protective shielding of the water is gone.