3He shortage has provoked a renewed interest for organic scintillation detectors (good neutron detection efficiency) with neutron-gamma discrimination capability. Pulse Shape Discrimination (PSD) with plastic scintillators has recently shown important progresses and raises a great interest as plastic detectors are not toxic and not inflammable contrary to liquid scintillation detectors. In this context, the French Atomic and Renewable Energy Commission (CEA), within the FP7 European project SCINTILLA, is studying the possibility to produce large size plastic scintillators as candidates for 3He tube replacements together with the related FPGA electronics. To support the design of plastic scintillators with enhanced neutron-gamma discrimination power, software based on ROOT data analysis software was developed to couple photon-neutron transport with MCNP PoliMi and optical photon tracking in the scintillator with Litrani. This new tool called “POLITRANI” allows to build realistic electronic pulses delivered by radiation detectors, and thus to study PSD sensitivity to various factors such as plastic shape, size, coating, scintillation decay time for neutrons vs. gamma rays, and radiation scattering in the detector. Parameters of the FPGA-based electronics can also be investigated, such as sampling frequency, trigger, and length of the integration gate.