Estimates of thermal fatigue due to beam interruptions for an ALMR-type ATW

Thermal fatigue due to beam interruptions has been investigated in a sodium-cooled ATW (accelerator transmutation of waste) using the Advanced Liquid Metal mod B design as a basis for the subcritical source driven reactor. A keff of 0.975 was used for the reactor. Temperature response in the primary coolant system was calculated, using the SASSYS-1 code, for a drop in beam current from full power to zero in 1 microsecond. Temperature differences were used to calculate thermal stresses. Fatigue curves from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code were used to determine the number of cycles various components should be designed for, based on these thermal stresses. (authors)