FUEL-ROD LOAD FOLLOW ANALYSIS

A methodology for fuel rod load follow performance evaluation is prese nted in this paper. The strain energy density accumulation during one cycle of load follow operation is applied in the cladding fatigue frac ture analysis. To combine the energy density increment with critical v alue for cladding fracture, the cycle number of load follow operation that will cause cladding fracture could be determined. Three typical l oad follow strategies for PWR standard 17 x 17 fuel rod are analyzed. For fuel with burnup 20 GWD/MTU, power reduction from 30 kW/m to 70% w ill not induce energy density increment whatever the load follow strat egy is. The 50% power load follow operation definitely causes energy d ensity accumulation and is of fatigue fracture concerns. The energy de nsity increment at 30% power is close to that of 50% operation. To com bine the critical energy density for cladding fatigue fracture and ins pection data of failure rods caused by load follow operation, the meth odology will become perfect and of practical use.