  Neutron imaging is a non-destructive technique for analyzing a wide class of
materials, such as archaeological or structures of industrial materials.
Technological advances, in recent decades, have had a great impact on the
neutron imaging technique, evolving from simple radiographs using films (2D) to
modern tomography systems with digital processing (3D). The Instituto de
Pesquisas Energ\'eticas e Nucleares (IPEN), in Brazil, houses a 5MW research
nuclear reactor, called IEA-R1, where there is a neutron imaging instrument
with $1.0 \times 10^{6}$ $n/cm^{2}s$ in the sample position. IEA-R1 is over 60
years old and the future of neutron science in Brazil, including imaging, will
be expanded on a new facility called the Brazilian Multipurpose Reactor (RMB).
The new reactor will house a suite of instruments at the Neutron National
Laboratory, including the neutron imaging facility called Neinei. Inspired by
recent work, we model the Neinei instrument through stochastic Monte Carlo
simulations. We investigate the sensitivity of the neutron imaging technique
parameter ($L/D$ ratio) with the neutron flux, and the results are compared to
data from the Neutra (PSI), Antares (FRM II), BT2 (NIST) and DINGO (OPAL)
instruments. The results are promising and provide avenues for future
improvements.

Instrumentation and Detectors;Nuclear Experiment;Quantum Physics