The strategies foreseen for future development and employment of nuclear power generation underline the use of nuclear energy systems in which the nuclear fuel contains consistent and controlled amounts of the minor actinides (MA). These minor actinides, particularly neptunium and americium, are produced as normal by-products of the operation of thermal power reactors. Because of the existence of long-lived isotopes of these elements, they constitute the major sources of the radiation in spent fuel and in wastes resulting from their reprocessing. Reliable and accurate neutron-induced reaction cross section data are required for the important isotopes of these MAs, including reasonably low uncertainties for sound core design studies and high burn-up strategies.
The Agency has initiated a Coordinated Research Project on “Neutron Reaction Data for Minor Actinides (MANREAD)” as part of a worldwide effort to determine the present status of our knowledge on MA neutron reaction data. Experimental facilities will be assessed to undertake measurements of neutron reaction cross sections for the important isotopes of the MA elements. The CRP is expected to deliver the results of this experimental, theoretical and nuclear data evaluation work by the end of 2011
The overall objectives of the CRP are the critical evaluation, uncertainty assessment and production of neutron cross section data for an agreed set of minor actinides. This CRP is composed of research groups performing relevant experiments at the most appropriate facilities in Europe, United States of America, Japan and elsewhere, addressing agreed overall objectives of the CRP and delivering up-to-date results on neutron reaction data for the minor actinides.
A worldwide assessment will be made of the experimental capabilities to undertake measurements of neutron reaction cross sections for the important isotopes of the minor actinides;
Publish a final technical report and make new reaction cross section data available online and for distribution on CD-ROM.
Report measurements of neutron-induced reaction cross sections on MA just completed or planned in the period of activity of the CRP, at research laboratories worldwide;
Uncertainty assessment of available experimental information on MA neutron cross section data (including data from measurements to be performed in the next two-year period). Assessment of the quality and uncertainties of MA data present in the evaluated nuclear data libraries (ENDF/B-VII, JEFF3.1, BROND-2.2, JENDL-3.3, etc.);
The CRP participants were able to measure, assess and evaluate neutron induced reaction cross sections for a set of minor actinides ( 234,236U, 237Np, 238,240,241,242Pu, 241,242,242m,243Am). These newly obtained experimental and evaluated data will be incorporated in the next releases of national data libraries such as ENDF/B, JEFF, JENDL, CENDL and BROND, and will provide more accurate inputs for reactor core designing. In such a way the results of this CRP will have a significant impact on developments of next generation nuclear energy systems (e.g., GEN IV reactors, accelerator-driven minor actinide burner, hybrid fusion-fission system) carried out by Member States.
237Np(n,f) cross sections measured at LANL LANSCE facility was used as an input to the least-squares analysis (GMA) for evaluation of JENDL-4.0.