ABSTRACT
Fuel failures detection and monitoring is a key issue in sodium-cooled fast reactor operation. This detection is based on monitoring the signal of fission products using dedicated radiation monitoring systems based on gamma spectrometry or neutron counting. In this context, the French Alternative Energies and Atomic Energy Commission (CEA) investigates and developpes a Compton suppression system composed by a high-purity germanium diode, a bismuth germanate scintillator and a dedicated digital signal processing allowing filtering coincidences. This approach enables the Compton noise to be filtered without impacting the useful signal from short-lived radioisotopes. Through a calculation scheme based on a validated MCNP6 model of the detector. It was demonstrated that the sodium degassing is a mandatory option reducing the minimal detectable activities of fission products by a factor of up to 27. The Compton suppression system leads to an additional minimization of minimum detectable activities up to a factor of 4 enabling the ease measurement of the 89Kr safety indicator.
ABSTRACT
This paper presents the investigation carried out by CEA List and ArcelorMittal R&D in order to assess the potential of linac-based neutron activation analysis to detect and quantify copper in scrap metal. Performances are evaluated using MCNP6 and then validated experimentally using a 6 MeV linac coupled with heavy water. It is shown that (γ, n) reaction cross-sections for deuterium are likely to be undervalued in ENDF/B-VII and suggested that photoneutron production algorithms in Monte Carlo codes should be reexamined.
