OICC Press Journal of Theoretical and Applied Physics 2251-7235 19 1 2025 02 10 Thermal neutrons produced from an 241Am-Be source in different moderators 1 8 10.57647/j.jtap.2025.1901.05 EN Kourosh Sadeghi School of Physics, Damghan University, P.O. Box 36716-41167, Damghan, Iran Mojtaba Tajik School of Physics, Damghan University, P.O. Box 36716-41167, Damghan, Iran https://orcid.org/0000-0002-8714-5135 Journal Article 2025 02 10 A cylindrical proportional gas detector has been developed and simulated using the MCNPX code for neutron detection. This setup is specifically designed for use in nuclear laboratories that utilize neutron sources for educational and research activities. To achieve this goal, BF3 gas detector with a cylindrical geometry of 31.11 cm length and 1.219 cm radius was considered. The simulation results were then used to experimentally test the system with different moderators such as water, paraffin and polyethylene (PE). These measurements were performed with a 1.591E11 Bq (4.3 Ci) 241Am-Be isotopic neutron source. The simulation outcomes indicated that variations in moderator thickness and material have effects on the counts of the neutron detection setup, which are in agreement with the experimental data. Also, the comparison between the measurement and simulation results shows that an online neutron detection system, with BF3 gas detectors, can reliably monitor the neutron flux background radiation within a laboratory environment.