Fission chambers are widely used for on-line monitoring of neutron fluxes in irradiation reactors. A selective measurement of a component of interest of the neutron flux is possible in principle thanks to a careful choice of the deposit material. However, measuring the fast component is challenging when the flux is high with a significant thermal component. The main problem is that the isotopic content of a material selected for its good response to fast neutrons evolves with irradiation, so that the material is more and more sensitive to thermal neutrons. Within the framework of the FNDS (Fast Neutron Detector System) project, we design tools that simulate the evolution of the isotopic composition and fission rate for several deposits under any given flux. In the case of a high flux with a significant thermal component, 242Pu is shown to be the best choice for measuring the fast component, as long as its purity is sufficient. If an estimate of the thermal flux is independently available, one can correct the signal for that component. This suggests a system of two detectors, one of which being used for such a correction.
|Title of host publication||First International Conference on Advancements in Nuclear Instrumentation, Measurement methods and their Applications (ANIMMA), 2009|
|Place of Publication||Piscataway, NJ, United States|
|State||Published - 8 Jul 2010|
|Event||2009 - ANIMMA - Advancements in Nuclear Instrumentation Measurement Methods and their Applications: International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications - CEA, Marseille|
Duration: 7 Jun 2009 → 11 Jun 2009
|Conference||2009 - ANIMMA - Advancements in Nuclear Instrumentation Measurement Methods and their Applications|
|Period||2009-06-07 → 2009-06-11|