Safety design maps: an early evaluation of safety to support reactor design

Abstract

A new tendency in nuclear reactor conceptual design is to include safety criteria through accident analysis to address the selection of the engineering solutions and the value of the main design parameters. In this work, the concept of design map is used to correlate reactor safety performance with the design parameters. The effect of different design parameters on characteristic safety variables, referred to as “observable variables,” extracted from reactor evolution during accidents, is analyzed, and the concept of “safety design maps” is introduced. The sensitivity of these “observables variables” regarding changes in design parameters is visualized. Several safety design maps are built from the performance of an integral type reactor during loss of heat sink (LOHS) and main steam line break sequences without SCRAM to show the technique potentiality. Maximum reactor pressure vessel (RPV) pressure and minimum departure from nucleate boiling ratio are chosen as “observable variables” and their sensitivity to geometry-related parameters and reactivity coefficient is studied. Multiple-parameter single design maps and combined design maps for both accidental sequences are built as examples. The results show the usefulness of this technique to balance and optimize reactor design through an early engineering step. A computer code (HUARPE) has been developed in order to simulate these transients. The cooling circuit, the steam dome, the pressure vessel structures and core models are considered.