“…The UO 2 and Zr can interact chemically at temperatures as low as 1273 K, leading to a complex series of reaction layers [168] where, from both internal and external oxidation, the following reaction layers can be formed [168], and the AECL experiments were conducted at an overpressure of 1 MPa [169]. In the CANDU fuel design, the thin sheath will creep down onto the fuel under the conditions of the high pressure coolant.…”