Experimental determination and re-evaluation of nuclear data for the parametric and k0-standardization of neutron activation analysis

The success of the k0-standardization of Neutron Activation Analysis relies in the continuous revision of its core values. Although the k0 and Q0 factors are defined as “nuclear constants”, it is clear from their experimental nature and correlation to adopted nuclear data that these “constants” can change in time. It has been shown that part of the current recommended k0-library has been determined experimentally only once, 30 years ago, and that it is correlated to nuclear data adopted from unconfirmed literature available before 1980. Several authors have identified systematic differences in their analysis of reference materials when employing certain sub-datasets in the current k0-literature (2012) but the task of identifying the source of these inaccuracies can be difficult or even inconclusive, until more experimental data is made available to the k0-community. A review of a redetermination of 388 k0 nuclear data for 76 (n,γ) target isotopes, leading to the formation of 96 radionuclides states (364 γ-rays of analytical interest) are presented and the method to determine n(235U)/n(238U) was improved. For the latter task, new k0 factors for both 238U neutron capture and 235U fission were introduced. The k0 nuclear data for these 2 additional target isotopes leading to 239Np and 20 fission products was explored to provide information about the uranium enrichment levels in multi-elemental samples, with useful application in neutron forensics for safeguards and/or in environmental monitoring.