Consolidation of the High-Temperature Reactor Code Package HCP: Integration of the Source Term Analysis Code System STACY

The high-temperature reactor (HTR) code package, HCP, was initially codeveloped by Forschungszentrum Julich (FZJ) and RWTH Aachen University to address the need for an integral code package for HTR technologies, serving both licensing and safety evaluations. The code combines many previously independent analysis tools that were developed during HTR development in Germany, particularly at FZJ.

The consolidation of the HCP code is part of the German research project KONHCP (KONsolidierung HCP) with the integration of central processes such as the reactivity control by control rods (Technical University of Munich) and the simulation of the fission products release and transport within the primary circuit in normal and accident conditions (Becker Technologies).

This paper provides insights into the status of the integration in HCP of the Source Term Analysis Code system (STACY) module. In its original form, STACY is a standalone code in which users provide the data input, with several calculations needed to simulate different pebble histories. In the HCP framework, full-core calculations are now supported. For each fuel zone (node/batch), a STACY calculation is performed, with the other HCP modules automatically providing the input data required for the source term evaluation.

A source term calculation for a small HTR in normal operation followed by a station blackout (SBO) using a single input in a single calculation run is presented. The simulation provides the maximum fuel temperature reached during the SBO transient as well as the fractional release of relevant nuclides. The analysis is supported by an uncertainty study. To assess the capabilities of HCP in simulating a HTR under normal and accident conditions, the HTR-10 reactor test case was selected and benchmarked on two scenarios: steady-state temperature at full power and SBO at 3 MW.