Correction calculations for measure of the emission rate of the neutron sources in manganese sulfate bath at LNMRI/IRD

The Manganese Sulphate Bath [BSM] is the principal method used in laboratories of metrology to absolutely neutrons sources. The BSM consists basically of a big tank, full of manganese aqueous sulphate solution, next to the saturation condition. The radioactive source object of the measurement is immersed in the solution, where the majority of neutrons emitted by that is captured by the manganese, that it becomes radioactive [56Mn]. When decaying 56Mn emits radiation gamma, used in the measure of the emission rate of the neutron sources. Many parameters are used to correct the emission rate of the neutron source, amongst which are the losses due to neutron escape of the BSM, fast neutron capture for the solution and neutron capture by the source. The present work calculates these losses through Monte Carlo simulation [MCNP4C2]. In this simulation, the sources of routine used in the neutron lab at the Radiation Protection and Dosimetry have been considered [LN-IRD]. The objective of the simulation is to diminish the uncertainties and increase the accuracies on the determination of the mentioned losses. In simulation, it is possible to make individual calculations for each problem itself and determine all the components of the losses, for each specific situation of measurement. In future, the losses calculated by Monte Carlo method will substitute the ones that are currently used from experimental data. (author)