Thermal-Neutron Capture Cross Section and Resonance Integral of Americium-241

Abstract

The thermal-neutron capture cross section (0;g) and the resonance integral (I 0;g) leading to the ground state of 242 Am were measured by an activation method for neutron capture by 241 Am. A method with gadolinium, which was similar to the cadmium difference method, was used to measure the cross section 0;g with attention to resonances of 241 Am. Americium chloride samples containing 241 Am radioisotope were irradiated for 68 h in the long-irradiation plug of the Kyoto University Research Reactor, KUR. Wires of Co/Al and Au/Al alloys were used as monitors to determine thermal-neutron fluxes and epithermal Westcott's indexes at the irradiation positions. An-ray spectrometer was used to measure the activity ratios of 242 Cm to 241 Am. On the basis of Westcott's convention, the 0;g and I 0;g values were determined as 628 AE 22 b and 3:5 AE 0:3 kb, respectively.

Precise Measurements of Neutron Capture Cross Sections for LLFPs and MAs

“…The results for LLFPs are listed in Table 5.1, and for MAs [24][25][26][27][28][29][30][31] in Table 5.2, together with previously reported data. Here, the symbols σ eff , σ 0 , and I 0 denote the effective cross section, the thermal neutron capture cross section, and the resonance integral, respectively; σ 0 is the cross section at the neutron energy of 25.3 meV.…”

Improving nuclear data accuracy of 241Am and 237Np capture cross sections

“…With the use of Gd filter (effective cut-off energy around 0.1 eV), the problem of the bias is practically nonexistent. This method was used e.g., by Nakamura [9]. An independent study [11], based on analytical corrections to the Westcott formalism due to deviation of the neutron spectrum from idealized shape, yields similar correction factors for 241 Am(n,γ ) cross section at 25.3 meV as the above described numerical method.…”

“…[9,10]. Both methods are crude since they approximate the neutron spectrum ϕ(E) with only two free parameters (three in case variations in spectrum temperature are allowed).…”

“…The derived values for thermal (0.0253 eV) capture cross section for 241 (9) 25.94 (7) 25.94(6) α 6112.72 (8) 74.06 (7) 74.08(7) α …”

Research and development for accuracy improvement of neutron nuclear data on minor actinides

“…For the measurement of thermal neutron capture cross sections, an activation method has been widely used using a research reactor [30][31][32]. In order to separate thermal neutrons from epi-thermal neutrons, a Cd cut-off method has been applied.…”