The development of a transient version of the HOTROD computer code

The full length fuel rod steady state performance code HOTROD has been developed to predict fuel performance during a transient. This paper explains the theory used to calculate the transient fuel temperatures using the Crank-Nicolson method. Transient HOTROD predictions of SGHWR and PWR axial clad temperatures during a loss-of-coolant accident are given and are compared with those predicted by other codes. The code is being further developed to model Zircaloy clad ballooning and the creep equations coupled to the heat transfer equation derived in this paper.