Reactor test of beryllium as self-powered neutron detector emitter for fast neutron flux measurement

Neutron flux in nuclear reactors causes damages to material components. Fast neutrons, above 1 MeV, modify mechanical and structural properties of materials. Some experiments carried out in research reactors study the ageing of materials exposed to high neutron fluxes. In these experiments, the selective on-line monitoring of fast neutron flux in a water-pool type reactor environment remains a measurement challenge. The aim of this work is to experimentally validate the use self-powered neutron detector technology to monitor fast neutron flux in a water-cooled reactor. After a systematic review of the periodic element table, beryllium appears to be the most suitable emitter material for measurements sensitive and selective to fast neutrons. Due to its threshold cross section to neutrons and its low interaction probability with gamma rays, beryllium seems the appropriate candidate as emitter material for reactor environment use. Beryllium SPND prototypes were designed and manufactured. In June 2024, beryllium SPND prototypes have been tested in the Slovenian TRIGA Mark II reactor (Jožef Stefan Institute - JSI). These specific reactor tests in well-characterized irradiation conditions could enforce fast neutron SPNDs as a new option for on-line monitoring of technological irradiations.