Assessment of thermal storage systems and thermomechanical effects for pulsed reactors

Pulsed operation of fusion power plants has severe impact on all major reactor components. This analysis focuses on the sensitivity of one subsystem, the breeding blanket, to pulsed operation in terms of thermal storage requirements and thermomechanical effects. For analysis, a water-cooled Li/sub 2/O breeding blanket (400 MWth, 3.45 MW/m/sup 2/ neutron wall loading) was chosen. With the operating temperature window, 800/410/sup 0/C for Li/sub 2/O, thermal analysis shows that for the coolant-in-tube design (STARFIRE) there would be 10 rows of coolant tubes in the radial direction of the blanket. Since the thermal inertia of the blanket is larger further away from the first wall, the mixed mean temperature of coolant from all regions will dictate the design requirements for the thermal storage system. Three representative blanket regions were analyzed under four burn scenarios (startup/shutdown time = 10 s, steady-state time = 3600 s, and dwell time = 0, 30, 90, and 200 s) to estimate the thermal storage requirements. The size of the thermal storage system is dictated primarily by the energy deficiency that occurs during the dwell/startup and shutdown phase, although time/temperature response of the heat transfer fluid is critical to the design. Only pressurized water/steam and hot sodium thermal storage systems are considered for this study, since alternative systems are not attractive for heat storage of the order of 11 MWh to 230 MWh.