Abstract
The neutron capture-cross section of 237Np was measured using the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) with special emphasis in the region of interest for the core design of Accelerator-Driven Systems (ADS), from 0.5 to 500 keV. A neutron time-of-flight method was employed using the NaI(Tl) spectrometer in the ANNRI beamline at the Japanese Proton Accelerator Research Complex (J-PARC) together with the pulse-height weighting technique. The cross-section was determined by normalizing the results to JENDL-4.0 cross-section data at the first resonance of 237Np. In the 0.5 to 500 keV range, the present preliminary results present better agreement with previous experiments of Weston et al [3]. Experimental data from Esch et al [6] is about 15% lower than the present results. In comparision with evaluated data, ENDF/B-VIII.0 offers better agreement from 0.5 to 10 keV than with JENDL-4.0. From 0.5 to 10 keV JENDL-4.0 underestimates the present results by 10-15%. Nontheless, over 10 keV energy JENDL-4.0 shows good agreement up to 500 keV. The present preliminary cross-section has uncertainties of about 5% from 0.5 to 35 keV, a value lower than the uncertainties present in JENDL-4.0 of 6-10%. However, over 35 keV the total uncertainties steadily increase and amount to 10% at 500 keV.
Highlights
Nuclear transmutation has been widely established as a solution in order to reduce the long term accumulation of the high-level component of the nuclear waste
The experiments were conducted at the Accurate NeutronNucleus Reaction Measurement Instrument (ANNRI) from the Materials and Life Science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC)
The obtained relative cross-section was normalized to the first resonance value of the JENDL-4.0
Summary
Nuclear transmutation has been widely established as a solution in order to reduce the long term accumulation of the high-level component of the nuclear waste. Available nuclear data are not suitable for the final designs of the neutron transmutation systems. The region of interest for the core design is from 0.5 to 500 keV, where JENDL-4.0 [2] includes uncertainties for the capture cross-section of 237Np from 6% up to 10%. It is of utmost importance to precisely determine the neutron capture cross section at such energy range in order to reduce the uncertainties
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