Dimensionally adaptive dynamic switching and adjoint sensitivity analysis: new features of the RELAP5/PANBOX/COBRA code system for reactor safety transients

This paper highlights two novel features that have been implemented into the coupled RELAP5/PANBOX2/COBRA3 (R/P/C) code system. On the one hand, the R/P/C code system has been extended to include a dimensionally adaptive algorithm that uses the underlying physical phenomena to switch dynamically between three-dimensional (3D), one-dimensional (ID), and point-kinetics models, thereby reducing computational times up to a factor of five while preserving the accuracy, within user-defined error criteria, of the 3D reference calculation. On the other hand, the R/P/C system has also been extended to include the Adjoint Sensitivity Analysis Procedure (ASAP) for the RELAP5/MOD3.2 two-fluid model with non-condensables, thus enabling the efficient calculation of local sensitivities of RELAP5 results to various parameters in the RELAP5 code.