Neutron area monitor for ambient dose equivalent (H*(10)) and effective dose (EAP) using prompt gamma rays induced in high density polyethylene with metallic external layer

Abstract

Estimations of neutron ambient dose equivalent, H∗(10) and effective dose (anterior-posterior), EAP using measured prompt gamma intensities are theoretically investigated for several prompt gamma generating detection systems, each consisting of a cylindrical high density polyethylene (HDPE) covered with a layer of different materials. The neutron induced prompt gamma intensities are measured using a NaI(Tl) detector with lead as shielding. Materials like cadmium, iron, nickel, zinc, copper and lead are used as an outer layer covering the HDPE cylinder. A linear combination of the distributions of the prompt gamma intensities emitted from these materials at different incident neutron energies are subjected to multiple linear regression analyses to fit the energy dependent neutron fluence to dose conversion coefficients (DCC) as provided by the International Commission on Radiological Protection (ICRP). The aim of the present work is to explore the suitability of other elements to replace boron in the earlier used borated HDPE in the system to overcome certain practical difficulties. Different neutron energy distributions in the energy range from about 0.01 eV to 20 MeV are selected to validate the dose estimation. Among the materials used, iron, nickel, zinc and copper show promising results for the estimation H∗(10) as well as EAP as a replacement of boron for neutron energy distributions with predominant high energy components.