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

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 the 94Zr-96Zr isotope pair gives significant improvement in precision while measuring PHIsub(th)/PHIsub(e) ratios in the 20100) channels. The I0/sigmasub(th)-values for the mentioned Zr isotopes have been experimentally determined and compared with previously published data. Two disadvantages of Zr should be mentioned. First it cannot be used repeatedly due to the relatively long half-life of 95Zr. Secondly, the irradiation of Zr does not result in adequate activities in low power reactors (PHIsub(th)<1011 n cm2 s) and short irradiations (<10 min). (T.G.)