Corrosion of Nuclear Materials in Extrema conditions; in situ Synchrotron Studies

There is a general lack of fundamental understanding of oxidation and associated corrosion mechanism that occur in current nuclear materials such as zirconium alloy fuel cladding, nickel alloys steam generator tubes, and stainless steels internals, as well as advanced nuclear materials such as SiC and coated zirconium alloys for ATF (Accident Tolerant Fuel) cladding applications under extreme conditions of temperature, pressure, and corrosive environments. For most metal-oxide systems, the relationships between the oxidation conditions and the resulting oxide-film growth kinetics and microstructure are poorly understood [1]. This lack of understanding has led to models that are empirical at best and do not provide a physical description of the corrosion mechanism [2,3]. In addition, although it is well known that water radiolysis is preponderant in nuclear materials and significantly affects corrosion, satisfactory radiolysis effects on corrosion-coupled models are still lacking [4].

The autoclave is designed and built to simulate the in-reactor environment that zirconium alloys operate at in normal reactor operating conditions. The autoclave can operate at temperatures up to 400ºC and pressures up to 18 MPa. It has a rotating actuator to align the sample with respect to the incident-ray beam. The autoclave has two sapphire windows to pass the X-ray beams and in the same time maintain the high-pressure environment. The exit window is tilted 5º degrees to allow the detection of additional reflections (diffraction rings) of the sample without blockage of the autoclave body. The total opening angle in inlet or exit is 30º degrees.

[1] R. L. Williamson, N. A. Capps, W. Liu, Y. R. Rashid, and B. D. Wirth, “Multi-Dimensional Simulation of LWR Fuel Behavior in the BISON Fuel Performance Code,” Journal of The Minerals, Metals & Materials Society, vol. 68, no. 11, pp. 2930-2937, 2016.

[2] T.-L. Cheng, Y.-H. Wen, and J. A. Hawk, “Diffuse-Interface Modeling and Multiscale-Relay Simulation of Metal Oxidation Kinetics – With Revisit on Wagner’s Theory,” Journal of Physical Chemistry C, vol. 118, no. 2, pp. 1269-1284, 2014.

[3] A. Couet, A. T. Motta, and A. Ambard, “The Coupled Current Charge Compensation Model for Zirconium Alloy Fuel Cladding Oxidation: I.Parabolic Oxidation of Zirconium Alloys,” Corrosion Science, vol. 100, pp. 73-84, 2015.

[4] Y. Kim, et al., 16th International Symposium on Zirconium in the Nuclear Industry, pp. 91-116, 2011.