Flux variation related uncertainty in neutron activation analysis

The half-life of the product of the nuclear reaction applied to monitor the neutron flux has significant influence on the uncertainties of derived quantities of an investigated sample, such as the reaction rates, isotopic composition. If the flux is supposed to be constant during the irradiation, but its value varies between an upper and a lower limit, a so-called flux variation error occurs in the derived quantities. This error has been quantitatively analysed regarding various irradiation times, decay constants of the monitor foils and the nuclides of interest. Practical formulae have been elaborated, which can be used to handle this type of uncertainty.