Neutron spectrometry of a 241Americium-Boron neutron source using the NCT-WES single-moderator neutron spectrometer

Abstract

²⁴¹Americium-boron (α,n) neutron sources have been produced for various application from nuclear industry to well logging or radiation protection. Compared to ²⁴¹Americium–beryllium sources their specific emission rate is lower, but their spectrum is narrower, and their production cycle uses boron, which is less toxic than beryllium. Very few data are available in literature about the energy distribution of this neutron source: the 2001 version of Standard ISO 8529-1 reported a reference spectrum derived from 1970s data, exhibiting a single peak from about 1 to 6 MeV. Other spectra are available in recent works from PTB and NPL, based on high-resolution spectrometers and Bonner spheres. ENEA Frascati owns a ²⁴¹Am-B neutron source with nominal emission rate 3.5 × 10⁶ s⁻¹. Knowing its spectrum is important, as this source is used to feed the HOTNES (Homogeneous Thermal Neutron Source) facility. A spectrometry experiment was organized relying on the recently developed NCT-WES neutron spectrometer. Belonging to the family of the Single Moderator Neutron Spectrometers, NCT-WES is a convenient alternative to Bonner spheres as it derives the whole spectrum from a single exposure. The experimental data were elaborated in comparison with the existing literature spectra. As a main results of the study, the spectrum of the ENEA ²⁴¹Am-B neutron source nearly perfectly agrees with that derived at NPL.