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.

Dr.-Ing. Janis Lapins (*1980), 2001 - 2008 studied technology management (mechanical engineering), University of Stuttgart;2008 - 2016 Work as research assistant at the Institute of Nuclear Technology and Energy Systems, University of Stuttgart, Germany;May 2015 Defense of Doctoral Thesis