Measurement of 232Th and 238U neutron capture cross-sections in the energy range 5–17 MeV

Cross-sections of the 238U (n, γ) 239U reaction in the 3.0–7.0 MeV energy region measured by relative activation method*

“…The experimental values obtained by Panitkin et al [24] are compatible with the evaluation database CENDL-3.2 but are superior to the ENDF/B-VIII.0 and ROSFOND-2010 [28] databases in the 3.0-7.0 MeV energy region. In contrast, the experimental measurements of Mulik et al [4] at 5.9 ± 0.5 MeV neutron energy and the data of S.Mukherjee et al [7] at 5.1 ± 0.2 MeV are in general accordance with the evaluation databases ENDF/B-VIII.0 and ROSFOND-2010, respectively, yet far inferior to the evaluation data of CENDL-3.2. As stated above, accurate measurements of the reaction cross-sectional values of 238 U (n, γ) 239 U in the 3.0-7.0 MeV neutron energy region are critical for the assessment of cross-section data.…”

“…After the samples had been irradiated for 12 h and cooled for an adequate amount of time (2.7-43 h for Au flakes and 3.5-48 h for U 3 O 8 samples), the characteristic γ-rays produced were measured with a single-ended coaxial low-background GEM30P4-76 HPGe detector with an energy resolution of 850 eV FWHM at 122 keV and 1.85 keV FWHM at 1.33 MeV [6,30] as well as a 30% relative efficiency. The working high voltage was +2 kV, which was provided by ORTEC's 659 highvoltage power supply; the main amplifier 672 (pulse linear amplifier) had an adjustment multiple of 65 times and a time constant of 6 μs.…”

“…The 239 Np radionuclide is recognizable by the characteristic γ-rays of 106.1 keV, 228.2 keV, and 277.6 keV, whose intensities all surpass 10%. Nevertheless, the γ-rays at 277.6 keV were preferred over others in the calculations because the γ-rays at 106.1 keV and 228.2 keV are subjected to interference by the γ-rays at 103.2 keV and 228.2 keV originating from the fission products 153 Sm (T 1/2 = 46.284 h) and 132 Te (T 1/2 = 3.204 d), respectively [4][5][6]. In this experiment, the 197 Au (n, γ)…”

“…In the experiment, the scattered neutrons and the scattering effect interfere with the experimental results to a certain extent when the neutrons emitted from the accelerator cross the layers of cooled water and the tube wall material of the target head. Therefore, the Monte Carlo program GEANT4 is used to simulate and calculate this [6,30,36]. The number of target radionuclides N r was calculated firstly under the actual conditions (the presence of the surrounding materials).…”

“…The majority of these experimental values are centralized in the region of the neutron energy provided by the reactors, electrostatic accelerators, and high-voltage multipliers. Nevertheless, the cross-section measurements were performed at only eight energy points within the 3.0-7.0 MeV [4,6,7,18] energy region, and the measurement values are still relatively inaccurate and vary widely for the same energy point. Moreover, it is apparent that there are substantial variations among the evaluation databases for this energy region with three distinct tendencies; in particular, the ENDF/B-VIII.0 [26] and CENDL-3.2 [27] databases reach a maximum difference of 81.2% at a neutron energy of 7 MeV.…”