Neutron Capture Cross Section Of 237Np Research Articles

Measurement of the neutron capture cross-section of 237Np using ANNRI at MLF/J-PARC

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.

Neutron capture cross-section measurement and resolved resonance analysis of 237Np

ABSTRACTThe neutron capture cross-section of 237Np has been measured in the neutron energy region from 10 meV to 500 eV. 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). The experimental capture yield was derived using the pulse-height weighting technique and an energy-dependent cross-section was obtained relative to the incident neutron spectrum derived from a 10B(n, )7Li reaction yield. The absolute cross-section was determined by normalizing the results to JENDL-4.0 cross-section data at the first resonance of 237Np. The thermal cross-section was measured to be 177.6 ± 3.8 b. The resolved resonance region was analyzed with the REFIT code. An average radiation width = 40.3 ± 0.5 meV, a mean level spacing D0 = 0.60 ± 0.02 eV and a neutron strength function 104S0 = 1.02 ± 0.12 were obtained.

Capture Cross Sections of Neptunium-237

Neutron-capture cross sections of 237Np have been measured at eight neutron energies between 0.15 and 1.5 MeV. The experimental method was the activation technique in which the neptunium target was irradiated with a monoenergetic neutron beam and analyzed for the product 238Np by gamma-ray spectrometry.