Resonance absorption in HTR mixed cores from high and low-enriched uranium fuel

Automatic translation: Since the consortium's pebble bed high-temperature reactor (HTR) went into operation Experimental Reactor (AVR) GmbH in Jülich was the resource-saving thorium-uranium cycle with highly enriched uranium fuel and thorium as breeding material for many years Reference fuel for this HTR line. Efforts came from the USA to reduce the degree of enrichment of the fuels in order to make the misuse of fissile material for weapons purposes more difficult and thus, among other things, the basis for the introduction of nuclear energy into politically insecure areas /INFCE/. In this context, the HTR based on the pebble bed principle offers the possibility of unrestricted power operation from highly enriched to medium or low enriched to change fuel and thus once again proves its high flexibility and topicality. The experimental reactor of the AVR is due to the many years of experience of its operating team in the implementation of experiments and last but not least because of the embedding in the scientific and technical infrastructure of the KFA the ideal test device for core physical Experiments, and so the conversion of his fuel cycle has been successful since mid-1982 demonstrated. This process, which is continuous with a pebble bed core, is very demanding to the computer simulation: Even if the graphite-moderated, helium-cooled HTR is characterized by an overall good-natured reactor-physical behavior is a correct one Treatment of resonance absorption in fertile matter is of great importance. Due the more homogeneous arrangement of fuel compared to other thermal reactors and moderator, the resonance integrals are 2 to 3 times higher. The transition to low enriched fuel due to the higher U-238 inventory brought in with it Build-up of plutonium formed in it by resonance absorption. pronounced Fission resonances of Pu-239 in the thermal regime suggest that Pu-239 in burns to a greater extent in situ in the reactor, so a non-negligible proportion of the power generation has. Furthermore, the low-lying plutonium resonances have a great influence on the Core dynamics and from this point of view require an exact computational recording of the plutonium inventory. Last but not least requires the correct treatment of the decay heat of irradiated fuel precise knowledge both with regard to disposal and for incident considerations of the current uranium, plutonium and transplutonium vectors /IREl/.