Advanced 3-Dimensional Simulation Sytem for High Temperature Reactors

The concept of a pebble bed high temperature reactor with self-acting decay heat removal is a concept from the 1980's. At the time, computational capabilities were limited not allowing for 3-d transient calculations. This work is about the development of a time-dependent 3-dimensional simulation system for safety analysis of pebble bed high temperature reactors. It describes the improvements of the thermal fluid dynamic programme ATTICA3D concerning water and air ingress, and its subsequent coupling to the neutron transport code TORT-TD to account for mutual feedbacks and enable transient calculations. The simulation system is verified and validated against experiments and subsequently applied for possible reactor cases.