Design of a novel compact core with reduced enrichment for upgrading the research reactor Munich FRM

As an important result of the international reduced enrichment programs new fuel materials with very high uranium densities have been made available to users. This progress in fuel technology should also allow the realization of advanced core concepts for research reactors. Following this idea we are presently designing a novel ''compact core'' of about 20 cm diameter and 60 cm height, which will be cooled by H2O and surrounded by a large D2O moderator tank. For a reactor power P=20 MW we expect a maximum thermal neutron flux phisub(th)sup(max) asymptotically equals 8.1014 cm-2 s-1 outside of the core, and in any case the ''quality factor'' phisub(th)sup(max)/P would be the highest ever achieved at a beam tube reactor. While we started out neutronic calculations assuming high U235-enrichment, our present results for reduced enrichment (around 45%) are very promising; further calculations are in progress. The power density radial formfactor of the compact core can be reduced significantly by varying the uranium density in the individual concentric fuel plate rings. (author)