Critical evaluation of the effective resonance energy concept and the epithermal neutron spectrum shape-factor α for reactor NAA purposes

The epithermal reactor neutron spectrum shape-factor α and the associated effective resonance energy Esub(r) for a given nuclide are examined theoretically in great detail. First the necessity, meaning and importance of the choice of reference neutron energy in a non-ideal spectrum (α not=0) are explained. Next the definition and practical calculation of Esub(r) are discussed showing that the relation between the resonance integrals in ideal and non-ideal spectra can not be described adequately by two independent parameters Esub(r) and α. Finally, the effect of important errors on comparator technique based on the sup(197)Au reference nuclide. Conclusions are drown concerning the usefulness of comparator type reactor NAA as an alternative to clasical NAA using multi-element standards. (author)