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. (authors)