Development of self-powered neutron detectors for neutron flux monitoring in HCLL and HCPB ITER-TBM

• Self powered neutron detector (SPND) is attractive neutron monitor for TBM in ITER.
• In hard neutron spectra (e.g. TBM) there is the need to optimize their response.
• Three state-of-the-art SPNDs were tested using fast and 14 MeV neutrons.
• The response of SPNDs is much lower than in thermal neutron flux.
• FISPACT calculations performed to find out candidate materials in hard spectra.

Self powered neutron detectors (SPND) have a number of interesting properties (e.g. small dimensions, capability to operate in harsh environments, absence of external bias), so they are attractive neutron monitors for TBM in ITER. However, commercially available SPNDs are optimized for operation in a thermal nuclear reactor where the neutron spectrum is much softer than that expected in a TBM. This fact can limit the use of SPND in a TBM since the effective cross sections for the production of beta emitters are much lower in a fast neutron spectrum.This work represents the first attempt to study SPNDs as neutron flux monitors for TBM. Three state-of-the-art SPND available on the market were bought and tested using fast neutrons at TAPIRO fast neutron source of ENEA Casaccia and with 14 MeV neutrons at the Frascati neutron generator (FNG).The results clearly indicate that in fast neutron spectra, the response of SPNDs is much lower than in thermal neutron flux. Activation calculations were performed using the FISPACT code to find out possible material candidates for SPND suitable for operation in TBM neutron spectra.