New measurement of the ²⁴²Pu(n,γ) cross section at n_TOF

¹ Dpto. de Física Atómica, Molecular y Nuclear, Universidad de Sevilla, 41012 Sevilla, Spain
² Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), 28040 Madrid, Spain
³ Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany
⁴ Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany
⁵ European Center for Nuclear Research (CERN), CH-1211 Geneva, Switzerland

^a e-mail: jlerendegui@us.es

Published online: 25 March 2016

Abstract

The use of MOX fuel (mixed-oxide fuel made of UO₂ and PuO₂) in nuclear reactors allows substituting a large fraction of the enriched Uranium by Plutonium reprocessed from spent fuel. With the use of such new fuel composition rich in Pu, a better knowledge of the capture and fission cross sections of the Pu isotopes becomes very important. In particular, a new series of cross section evaluations have been recently carried out jointly by the European (JEFF) and United States (ENDF) nuclear data agencies. For the case of ²⁴²Pu, the two only neutron capture time-of-flight measurements available, from 1973 and 1976, are not consistent with each other, which calls for a new time-of flight capture cross section measurement. In order to contribute to a new evaluation, we have perfomed a neutron capture cross section measurement at the n_TOF-EAR1 facility at CERN using four C₆D₆ detectors, using a high purity target of 95 mg. The preliminary results assessing the quality and limitations (background, statistics and γ-flash effects) of this new experimental data are presented and discussed, taking into account that the aimed accuracy of the measurement ranges between 7% and 12% depending on the neutron energy region.