THE ZIRFLEX DECLADDING OF TUBE-IN-TUBE TYPE FUEL ELEMENTS

Pilot unit Zirflex dissolutions were carried out on near prototypical tube-in-tube type elements clad in oxidized Zircaloy. The runs were made with the elements horizontal and at simulated large scale operating conditions. No significant difference was noted between the actual decladding achieved in these experiments and that which was predicted from prior studies on similarly oxidized elements with somewhat different geometries. No gas blanketing nor diffusion effects were observed. Initially, preferential attack was noted on areas where oxide film had been scratched or handled. However, near the end of a run a random distribution of undissolved cladding existed; 90% of the cladding was removed in 6.5 hours. (auth)