Neutron Multiplication in Beryllium

The multiplication of 14-MeV neutrons in bulk beryllium has been measured using the manganese bath technique. Values of the multiplication have been obtained for beryllium samples of four thicknesses. Detailed calculations of the multiplication and all the systematic effects were made, utilizing a highly detailed three-dimensional model with the Monte Carlo program MCNP. The Young and Stewart and the ENDF/B-VI evaluations for beryllium were utilized in the analysis. Both data sets produce multiplication values that are in excellent agreement with the manganese bath measurements for both raw and corrected values of the multiplication. We conclude that there is no real discrepancy between experimental and calculated values for the multiplication of neutrons in bulk beryllium.