Fuel storage and handling accidents

In the German Storfall-Berechnungsgrundlagen it is postulated that in such an incident all the fuel rods of one outer row of the respective assembly are damaged. It is further assumed that 10% of the fission product noble gas inventories of these rods is released to the containment atmosphere. As for the fission product iodine, 5% of the inventory has to be assumed to be transported to the pool water from there, a fraction of the iodine is assumed to be volatilized, in accordance with a partition coefficient of 1 - 10, which is calculated for a pool water volume of ISOOm and an atmosphere volume limited to 20,000 m. Airborne iodine is assumed to be present as 90% I2 and 10% organically bound iodine. 

Since in the fuel pellet - cladding gap fission product iodine is present as an iodide compound, it will be dissolved in the pool water as I ion. This means that a significant transport to the atmosphere can only proceed after oxidation to elemental I2, induced by the oxygen which is dissolved in the air-saturated pool water  

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