Abstract
Fast spectrum neutron-induced fission cross sections of transuranic isotopes are being of special demand in order to provide accurate data for the new GEN-IV nuclear power plants. To minimize the uncertainties on these measurements accurate data on spontaneous fission half-lives and detector efficiencies are a key point. High -active actinides need special attention since the misinterpretation of detector signals can lead to low efficiency values or underestimation in fission fragment detection. In that context, 240,242 Pu isotopes have been studied by means of a Twin Frisch-Grid Ionization Chamber (TFGIC) for measurements of their neutron-induced fission cross section. Gases with different drift velocities have been used, namely P10 and CH4. The detector efficiencies for both samples have been determined and improved spontaneous fission half-life values were obtained.
Highlights
In a recent assessment of target accuracies and uncertainties the NEA highlighted the need for improved nuclear data to be used in model calculations for innovative reactor systems (GEN-IV) [1]
In the present work we will focus on the determination of the detector efficiency and the spontaneous fission half-life, important ingredients in the final fission cross section determination, which will be subject of a forthcoming paper
To verify the efficiency results obtained with the CH4 gas, a theoretical calculation using SRIM [6] stopping power ranges and GEANT4 simulations [7] have been done
Summary
In a recent assessment of target accuracies and uncertainties the NEA highlighted the need for improved nuclear data to be used in model calculations for innovative reactor systems (GEN-IV) [1]. The neutroninduced fission cross sections of 240,242Pu have been identified in this study as of highest priority for fast spectrum reactors Their target uncertainties are very stringent and are requested to be lower than 5% in both cases from current uncertainties of 6% for 240Pu and 20% for 242Pu. In the frame of the ANDES collaboration (Accurate Nuclear Data for nuclear Energy Sustainability) several actinides are being under study, among them 240,242Pu. JRC-IRMM has been strongly involved in these measurements and has applied the new digital data acquisition techniques for cross section measurements. Using digital electronics and storing the full waveform opens up new analysis possibilities not available using regular analogue electronics
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