Neutron-induced reactions on U and Th – A new approach via AMS

Recent studies exhibit discrepancies at keV and MeV energies between major nuclear data libraries for ²³⁸U(n,γ), ²³²Th(n,γ) and also for (n,xn) reactions. We have extended our initial (n,γ) measurements on ^235,238U to higher neutron energies and to additional reaction channels. Neutron-induced reactions on ²³²Th and ²³⁸U were measured by a combination of the activation technique and atom counting of the reaction products using accelerator mass spectrometry (AMS). Natural thorium and uranium samples were activated with quasi-monoenergetic neutrons at IRMM. Neutron capture data were produced for neutron energies between 0.5 and 5 MeV. Fast neutron-induced reactions were studied in the energy range from 17 to 22 MeV. Preliminary data indicate a fair agreement with data libraries; however at the lower band of existing data. This approach represents a complementary method to on-line particle detection techniques and also to conventional decay counting.