MORECA, Simulating Modular High-Temperature Gas Cooled Reactor Core Heatup

1 - Description of program or function: MORECA was developed for analyzing postulated long-term core heatup scenarios for which active cooling systems used to remove afterheat following the accidents can be assumed to be unavailable. Simulations of long-term loss-of-convection accidents, both with and without depressurization of the primary coolant, have shown that maximum core temperatures stay below the point at which any significant fuel failures and fission product releases are expected. Sensitivity studies also have been done to determine the effects of errors in the predictions due both to uncertainties in the modeling and to the assumptions about operational parameters. MORECA models the U.S. Department of Energy reference design of a standard modular high-temperature gas-cooled reactor (MHTGR). It is based on the ORNL ORECA code system. 2 - Methods: The method of solution used was Modified Euler