Monte Carlo calculations and experimental calibrations of Bonner sphere systems with a new cylindrical helium-3 proportional counter

The response functions to mono-energetic neutrons from thermal energy to 20 MeV of eight polyethylene moderating spheres with a cylindrical proportional counter were calculated with the MCNP-4B code for each moderator and confirmed by measurements in wide neutron fields (ISO), as Am–Be and ²⁵²Cf, and with the CANEL and SIGMA IPSN Cadarache (France) facilities, which simulate realistic field and thermal neutron response. With the described spectrometry system, we have carried out neutron measurements at different points from the annular zone inside the containment building of the Vandellòs II Nuclear Power Plant (Tarragona, Spain). The aim of this work is to present the results obtained during the sphere spectrometer development, with reference to the experimental and theoretical aspects and to show that our calculated spectra correspond to points of measurement compared with those obtained using the MORELPA code.