PLANS FOR NEW DECAY DATA EVALUATIONS: UK WORK UNDERTAKEN AFTER BNFL/CEA AND UKAEA REVIEWS OF JEF-2.2 DECAY DATA FILES: 1996-2000 Summary A significant fraction of the UKPADD-2 decay-data library

A significant fraction of the UKPADD-2 decay-data library has been incorporated into version 2 of the Joint Evaluated File (JEF-2.2, OECD/NEA Data Bank). Subsequent reviews of JEF-2.2 have highlighted the need for further developments in the recommended data for fission and fusion applications. For example, UKAEA staff involved in fusion studies identified 80 nuclides for which improvements in their evaluated decay-data files would be beneficial. Furthermore, 27 fission products of importance in thermal reactor studies (plus short-lived daughters and related metastable/ground states) were judged to have inadequate decay-data files in JEF-2.2, while of importance in fuel reprocessing, as monitoring standards, or because they undergo significant delayed neutron decay. Decay data for an additional 35 short-lived fission products were also considered, despite the lack of measured data; theoretical data were adopted for these specific radionuclides. Sixty-one of 80 requested fusion nuclides and all of the fission products have been evaluated, and form part of the UKPADD-6 library (which contains decay data for a total of 452 radionuclides). UKPADD-6 will be available through the OECD/NEA Data Bank where it is currently undergoing formal quality assessment.