Analysis of the HTTR with Monte-Carlo and diffusion theory

Both ECN and IRI take part in the benchmark of start-up core physics of the HighTemperature Engineering Test Reactor (HTTR), which is described in detail in Ref. 1, and is part of the IAEA Co-ordinated Program “Evaluation of HTGR Performance The IRI results obtained with Monte Carlo techniques for the problems in this benchmark are described elsewhere [2]. Because the configuration of the core is quite complicated with in total 12 different uranium enrichments, ECN and IRI decided to analyse a simpler configuration also, and compare cross sections and the core model. In this simpler configuration only 5.2 % enriched uranium is used for all fuel blocks in the reactor (the fuel block in layer 5, zone 2, see ref. 1). For the comparison of cross sections, it was agreed to condense the energy range into two groups with the boundary at 2.1 eV.This report first describes the generation of cross sections for both Monte Carlocalculations and for calculations with deterministic codes. Subsequently, results of the analysis of the simple core configuration with the multi-group Monte Carlo code KENO and the diffusion theory codes BOLD VENTURE and PANTHER are presented. Then results obtained with BOLD VENTURE are given for the fully loaded core which has a variety on enrichments in the fuel assemblies. This includes the generation time and the effective fraction of delayed neutrons at critical. Finally, results for the fully loaded core with PANTHER are presented