High-temperature creep deformation in FeCrAl-oxide dispersion strengthened alloy cladding

Ukai, Shigeharu  ; Kato, Shoichi ; Furukawa, Tomohiro  ; Otsuka, Satoshi   

The FeCrAl-oxide dispersion strengthened (ODS) alloy is the promising cladding material for the accident-tolerant fuel (ATF) of the light water reactors (LWR). Ring-creep tests for FeCrAl-ODS alloy cladding were carried out at 973 K and 1273 K. The dislocation detachment stress from the dispersoid was derived by considering the dislocation-dispersoid elastic interaction and the dislocation relaxation effect by climb motion. When the applied stress exceeds the dislocation detachment stress, dislocations overcome the dispersoids with the reduced values of the stress exponent. When the stress is lower than the dislocation detachment stress, grain boundary sliding (GBS) is dominant factor for the low strain rate creep deformation at 1273 K. Based on those findings, new constitutive equations for creep deformation were constructed, which is applicable to low stress, low strain rate and high temperature conditions encountered at the reactor sever accident.