The k0 and Q0 values for the Zr-isotopes:: A re-investigation

The k(0) and Q(0) values for Zr-94(n,gamma)Zr-95 (E gamma = 724.2+756.7 keV) and Zr-96(n,gamma)Zr-97 (beta(-)) Nb-97m (E gamma= 743.4 keV) were re-investigated. The aim was to further improve the reliability of the neutron spectrum characterization (f and alpha monitoring) in k(0)-NAA, based on "bare monitor" methods with the use of these Zr radionuclides. So as to achieve this goal, experimental determinations were performed in three reactor centers: KFKI AEKI, Budapest (WWR-M reactor); INW, Gent (THETIS reactor); SCK.CEN, Mol (BR1 reactor). The results were: Q(0)(Zr-94)= 5.306; Q(0)(Zr-96)= 251.6; k(0)(Zr-95, 724.2+756.7 keV)=2.000E-4; k(0)(Zr-97/Nb-97m, 743.4 keV)=1.237E-5. This means that the newly evaluated k(0)-values are about 4.7% lower than the formerly reported ones. It is also emphasized that the Zr-97 half-life is 16.74 hours, contrary to the similar to 1% higher values usually reported.