Neutron spectrometry of a lightly encapsulated 241Americium–beryllium neutron source using two different Bonner Sphere Spectrometers

Abstract

Abstract 241Americium–beryllium neutron sources are used in a variety of applications, spanning from the civil engineering to the oil industry, and to the radiation dosimetry. The ISO 8529-1 Standard reports a reference distribution for the energy of the emitted neutrons, which extends from 0.1 to 11 MeV. Nevertheless every source exhibits a slightly different spectrum, depending on the material and dimension of the capsule, and on the amount of active material. This source-to-source variability is expected to mainly affect the energy region below 0.1 MeV. As these differences can be important in the fields of neutron dosimetry and metrology, some relevant source formats have been investigated with spectrometric methods. The neutron calibration laboratory of the Politecnico di Milano recently acquired a CZ/1003/S — 96 type 241 Am–Be source (nominal emission rate 2.2E+6 s−1). As this type of source is in use in a number of European laboratories, its spectrum was determined through a neutron spectrometry experiment, involving two Bonner sphere spectrometers with well-known responses. The experimental spectrum is compared to that published for a similar source and to the ISO-recommended one.