Zirconium as a multi-isotopic flux ratio monitor and a single comparator in reactor-neutron activation analysis

Abstract

Different methods for the determination of thermal-to-epithermal neutron flux ratio are reviewed and nuclear data for commonly used monitor materials and for Zr isotopes are tabulated. It is shown that the use of the⁹⁴Zr−⁹⁶Zr isotope pair gives significant improvement in precision while measuring Φ_th/Φ_e ratios in the 20<Φ_th/Φ_e<200 range. When the single comparator method is applied, the use of the⁹⁴Zr isotope is suggested as a comparator with the⁹⁴Zr−⁹⁶Zr isotope pair for simultaneous flux ratio determination. Theoretical calculations show that the Zr comparator-flux ratio monitor gives better precision and accuracy than does Ru for two-thirds of the isotopes used for analysis in well thermalized (Φ_th/Φ_e>100) channels. The I_o/σ_th-values for the mentioned Zr isotopes have been experimentally determined and compared with previously published data.