Particulars of the Effect of the Internal Medium of a Fuel Element in High-Burnup Fuel on the Corrosion Cracking of Fuel-Element Cladding under Stress

The mechanism of the reduction of iodine partial pressure in the presence of oxygen is examined. Analysis of computational and experimental studies shows that in fuel elements with high fuel burnup the concentration of iodine beneath the cladding decreases more than 100-fold in connection with an increase in the partial pressure of oxygen entering the fuel–cladding gap. The particulars of some radiationchemical processes beneath VVER fuel-element cladding with the participation of O 2 , I, I 2 , CsI, and inert gases (Xe, Kr, He), resulting together with an increase in fuel burnup in a reduction of the iodine emission kinetics and, in consequence, promoting fracture resistance of zirconium cladding under corrosion cracking conditions, are discussed.