The effect of peak cladding temperature occurring during interim-dry storage on transport-induced cladding embrittlement

To evaluate transport-induced cladding embrittlement after interim-dry storage, ring compression tests were carried out at room temperature(RT) and 135 °C. The ring compression test specimens were prepared by simulating the interim-dry storage conditions that include four peak cladding temperatures of 250, 300, 350 and 400 °C, two tensile hoop stresses of 80 and 100 MPa, two hydrogen contents of 250 and 500 wt.ppm-H and a cooling rate of 0.3 °C/min. Radial hydride fractions of the ring specimens vary depending on those interim-dry storage conditions. The RT compression tests generated lower offset strains than the 135 °C ones. In addition, the RT and 135 °C compression tests indicate that a higher peak cladding temperature, a higher tensile hoop stress and the lower hydrogen content generated a lower offset strain. Based on the embrittlement criterion of 2.0% offset strain, an allowable peak temperature during the interim-dry storage may be proposed to be less than 350 °C under the tensile hoop stress of 80 MPa at the terminal cool-down temperature of 135 °C.