Estimation of scattered radiation influence on neutron beams at a calibration laboratory using Monte Carlo simulation of a long counter

At the Neutron Calibration Laboratory (LCN) of IPEN/CNEN, a 241AmBe source was used to test and calibrate neutron detectors. The neutrons emitted by reach detector as intended, but they also scatter undesirably from building's floor, ceiling, walls, leading indirect detection. A Long Counter (LC) modeled using MCNPX Monte Carlo code. objective this study measure contribution scattered radiation at LCN / IPEN, determine fluence rate, different points in calibration room source-to-detector distances 100 cm 150 cm; subsequently, results were compared with those Brazilian Metrology Ionizing Radiation (LNMRI). show that rates IPEN are comparable laboratory for (37 GBq). detectors should be performed less than cm, where is within 40% limit recommended ISO 8529-1.