Enhanced thermal creep deformation under conditions of secondary stress cycling in the elastic regime

Enhanced thermal creep straining can take place under conditions of secondary stress cycling even when the maximum stress is within the elastic region. In the present investigation, a simplified analysis procedure is proposed to estimate the extent of enhanced creep strains under such conditions. A particular instance where this effect can be important is the case of a fuel rod in an LMFBR where there are temperature variations in the cladding due to power cycling. A detailed analysis of the fuel rod cladding to determine the damage and thermal creep strains due to power cycling operation is expensive and time consuming. The proposed simplified analysis procedure is aimed at computing the decay of thermal stress as a function of time with the computed stress history being used to assess the thermal strains under power cycling conditions. (Auth.)