Neutron attenuation studies in single shield materials for PFBR shield design using solid state nuclear track detection and activation techniques

The present paper describes the neutron attenuation studies in single shield materials for PFBR (Prototype Fast Breeder Reactor) shield design. The measurements were carried out to study neutron attenuation of the order of 10-4. Shield materials like carbon steel, graphite and boron carbide were studied to study neutron attenuation using solid state nuclear track detectors (SSNTDs) and activation detectors in the intermediate neutron energy range. The fission reaction rates from 2'37Np having effective threshold energy of 0.6 MeV and 2'32Th halving threshold energy of 1.4 MeV were studied by counting the neutron induced fission track density on Solid state nuclear track detectors (SSNTDs) like Lexan polycarbonate. The reaction rate from 115In(n,n')In115m foils having effective threshold energy of 1.3 MeV were studied by activation methods in these deep penetration shielding experiments. SSNTDs were found to be complimentary to activations detectors which can be very well used in deep penetration problems. Further backscattering effect were observed in carbon steel and graphite models when compared with Boron carbide model for 237Np fission reaction rates. (author)