Re-evaluation of the criticality experiments of the "Otto Hahn Nuclear Ship" reactor

Several series of experiments with a "FDR" reactor (advanced pressurized light water reactor) were performed in 1972 in the Geesthacht critical facility ANEX The experiments were performed to test the core prior to its usage for the propulsion of the first German nuclear merchant ship "Otto-Hahn". In the present paper a calculational re-evaluation of the experiments is described with the use of the up-to date computer codes (Monte-Carlo code MCNP5) and nuclear data (ENDF/B-VI release 6). It is focused on the determination of uncertainties in the benchmark model of the experimental set-up, originating mainly from the limited set of information still available about the experiments. Effects of the identified uncertainties on the multiplication factor were studied. The sensitivity studies include parametric variation of material composition and geometry. The combined total uncertainty being found 0.0050 in k(eff), the experiments are qualified as criticality safety benchmark experiments.