Neutron-induced fission cross sections of short-lived actinides with the surrogate reaction method

Abstract

Determination of neutron-capture cross sections of short-lived nuclei is opening the way to understand and clarify the properties of many nuclei of interest for nuclear structure physics, nuclear astrophysics and particularly for transmutation of nuclear wastes. The surrogate approach is well-recognized as a potentially very useful method to extract neutron cross sections for low-energy compound-nuclear reactions and to overcome the difficulties related to the target radioactivity. In this work we will assess where we stand on these neutron-capture cross section measurements and how we can achieve the short-lived Minor Actinides nuclei involved in the nuclear fuel cycle. The CENBG collaboration applied the surrogate method to determine the neutron-capture cross section of 233 Pa (T 1/2 = 27 d). The 233 Pa (n,γ ) cross section is then deduced from the measured gamma decay probability of 234 Pa compound nucleus formed via the surrogate 232 Th (3 He ,p) reaction channel. The obtained cross section data, covering the neutron energy range 0.1 to 1 MeV, have been compared with the predictions of the Hauser-Feshbach statistical model. The importance of establishing benchmarks is stressed for the minor actinides region. However, the lack of desired targets led us to propose recently the 174 Yb (3 He ,pγ ) reaction as a surrogate reaction for the (n,γ ) predetermined benchmark cross section of 175 Lu. An overview of the experimental setup combining gamma ray detectors such as Ge and C6D6 in coincidence with light charged particles Δ E-E Telescopes will be presented and preliminary results will be discussed.