Assessment and evaluation of decay data for nuclear reactor applications

Abstract

Discussions were initiated in 1994/1995 to identify specific inadequacies in the decay data of the Joint Evaluated File (JEF) prepared by the Nuclear Energy Agency (NEA) Data Bank for nuclear reactor applications. Various correspondence has taken place within Europe between the staff responsible for this file. The net result has been the generation of lists of radionuclides that were believed to require either further detailed assessments (to check for completeness and consistency) or comprehensive re-evaluations of their decay data. These radionuclides are of direct relevance and application to either fission reactors and fuel reprocessing, or fusion research: (a) A list of 37 fission-product radionuclides in priority order was formulated for which the decay data were judged to be of primary importance; decay-scheme data for a further 35 radionuclides were also defined as being inadequate, whilst being particularly important in decay heat calculations. (b) The decay data of approximately 50 radionuclides within the European Activation File (EAF) were identified as being problematic or incomplete when used for fusion reactor applications; these data exhibit inconsistencies between the mean gamma energies and component radiations (gamma rays, X-rays, annihilation radiation and internal bremsstrahlung). Using a combination of subjective judgement and statistical analysis, a series of clear directives were formulated, so that further efforts could be focused on improving and evaluating the decay data of those radionuclides judged to be inadequate. These re-evaluations are underway for completion at the end of 1998.