A manganese bath system for reliable neutron emission rate measurements

A complete Mn-bath system was installed at the Ionizing Radiation Metrology Laboratory (IRML), National Institute of Standards (NIS), Egypt. The system consisted of a stainless-steel sphere with a diameter of 1 m and a thickness of 5 Cm. An americium-Beryllium (Am-Be) neutron source with 3.7 × 10¹⁰ Bq activity was immersed in a Mn-bath that is filled with MnSO₄ solution. Gamma and neutron doses were measured outside the bath and were compared with the results calculated using Monte Carlo MCNP simulations. Different molarity of MnSO₄ was used, up to 0.91 mol/L. Required correction factors were determined analytically using neutron cross-sections for Sulfur, Oxygen, and Hydrogen elements, and by MCNP. An agreement between the experimental measurements of the neutron source emission rate and that obtained by MCNP was found; this agreement was enhanced with increasing MnSO₄ molarity up to 0.91 mol/L. Furthermore, the uncertainty of the emission rates was calculated, and it was found to decrease with increasing molarity.