Choen May Chan¹, Paul Binks¹, Douglas Rishel², Aliaksandr Baidak³; ¹Wood, ²Naval Nuclear Laboratory, ³Dalton Cumbrian Facility

Gamma radiation is suspected of playing a contributing role in accelerating the in-reactor post-transition corrosion kinetics of zirconium alloys such as Zircaloy-4. Previous work has shown that it is possible to infer the role of gamma radiation on corrosion by comparing instances where variations exist in gamma flux levels relative to neutron flux levels within different regions of a reactor or from one reactor to another reactor. To definitively determine whether gamma radiation plays a role in zirconium alloy corrosion, electrochemistry tests have been conducted using a mini-autoclave situated in the gamma irradiator at the Dalton Cumbrian Facility at dose rates ranging from 22 to 37 Gy/min under PWR water chemistry conditions using Zircaloy-4 working electrodes with pre-transition and post-transition thick oxide films. Data from open circuit potential measurements and electrochemical impedance spectroscopy will be presented that support the hypothesis that gamma radiation impacts corrosion under post-transition conditions.