Recent improvements in the system code package AC2 2019 for the safety analysis of nuclear reactors

The EC MUSA Project on Management and Uncertainty of Severe Accidents: Main Pillars and Status

In the current state of maturity of severe accident codes, the time has come to foster the systematic application of Best Estimate Plus Uncertainties (BEPU) in this domain. The overall objective of the HORIZON-2020 project on “Management and Uncertainties of Severe Accidents (MUSA)” is to quantify the uncertainties of severe accident codes (e.g., ASTEC, MAAP, MELCOR, and AC2) when modeling reactor and spent fuel pools accident scenarios of Gen II and Gen III reactor designs for the prediction of the radiological source term. To do so, different Uncertainty Quantification (UQ) methodologies are to be used for the uncertainty and sensitivity analysis. Innovative AM measures will be considered in performing these UQ analyses, in addition to initial/boundary conditions and model parameters, to assess their impact on the source term prediction. This paper synthesizes the major pillars and the overall structure of the MUSA project, as well as the expectations and the progress made over the first year and a half of operation.

A 3-D FINITE ELEMENT FEW-GROUP DIFFUSION CODE AND ITS APPLICATION TO GENERATION IV REACTOR CONCEPTS

In this paper, a recently developed 3-d few-group finite element-based diffusion code is de-scribed. Its geometrical flexibility allows future modeling of complex and irregular geometries of (very) small and medium size reactor concepts –(v)SMRs –being in the spotlight for energy provision in remote residential and industrial regions or for space applications, and also liquid metal cooled Generation IV reactors where thermally induced core deformation results in localized assembly lattice distortions which cannot be treated by traditional 3-d neutron kinetics codes devoted to the regular lattices of LWR and Generation IV systems. The description of the implemented FEM solution method is followed by first applications to a prismatic (or block type) high-temperature reactor MHTGR-350MW within an OECD/NEA benchmark activity and to the sodium cooled fast reactor concept ASTRID within the past EU project ESNII+. Finally, an outlook to planned further code development activities is given.