  In this paper, the distribution of radiation field in the CSNS spectrometer
hall was simulated by FLUKA program. The results showed that the radiation
field of high energy proton accelerator is dominated by neutron radiation, and
the range of neutron energy is quite widely, including about eleven orders of
magnitude. Nextly, work of simulation and calculation of the response functions
of four Bonner spheres with simplified model is done by FLUKA and MCNP codes
respectively, and the acceptable difference proved the feasibility of FLUKA
program in this application and the correctness of the relevant calculation
method. Through adopting the actual model, we simulate and calculate the energy
response functions of Bonner sphere detectors with polyethylene layers of
different diameters, including the detectors with lead layers by using FLUKA
code. According to the simulation results, we select eleven detectors as the
basic structure of ERNMS.
