Some investigations on the reactivity scale for the Super-Phenix 1 start-up experiment analysis

Possible sources of uncertainties in the effective fraction of delayed neutrons (βeff) calculations are investigated, in particular in relation to SUPER PHENIX. Method uncertainties, reaction rate bias and uncertainties and delayed neutron parameters uncertainties have been considered. Moreover, βeff uncertainties have been compared in SUPER PHENIX and in some experimental configurations of MASURCA, where control rod experiments have been performed, in order to assess eventual bias among critical experiments and power reactor data. Finally, some integral βeff measurements performed in SNEAK have been reanalysed, consistently with the above mentioned uncertainty analysis