SPERT benchmarks of the HFIR dynamic model

After the shutdown of Oak Ridge National Laboratory's high-flux isotope reactor (HFIR) in November 1986 because of embrittlement concerns, some of the design parameters were changed to ensure safe operation of the reactor with the existing pressure vessel. To properly document these changes and their effects on reactor operation, the safety analysis report of the HFIR is currently being updated. As part of this effort, an improved dynamic model of the HFIR core was developed, and the response of the HFIR to reactivity-induced accidents was analyzed. When compared to previous analog computer calculations, good agreement was achieved between the calculated and analog results except for low-power, low-flow transients. To further investigate low-power, low-flow transients, the short-period excursion reactor transients (SPERT) experiments have been calculated using the improved HFIR dynamic model. The purpose of this paper is to present the results of these comparisons