Anisotropies and Low-temperature Annealing Effect in Cold-rolled Nickel-Silver Alloy

The changes in hardness, elastic modulus and bending deflection with rolling reduction and with low-temperature annealing of nickel-silver were measured on the specimens cut parallel and transverse to the rolling direction of the sheet, and the results were considered in relation to the rolling structure. The anisotropies become more remarkable as the rolling reduction exceeds 50 per cent, and, in this region, the measured values are always higher in the transverse than in the other direction. This may be due to the development of the rolling texture and to the appearance of the flaw-like strain markings in the transverse direction. The low-temperature annealing makes the values of hardness and elastic modulus increase, and the maximum values are, in either case, obtained by heat-treatment at 350℃. Also, the larger the rolling reduction is, the higher the increasing ratio becomes. The change in hardness due to low-temperature annealing is larger as the grain size reduces, whereas the change in elasticity is hardly affected by the grain size. The anneal-hardening at each temperature does not show the two-stage hardening which has been observed in α-brass sheet, but shows a simple and smooth process. No difference in microstructure can be observed between as cold-rolled and as anneal-hardened state, although, in the previous work on α-brass, some structural changes thought to be a kind of polygonization were recognized after low-temperature annealing. The results of bending test correspond with those of elastic modulus

EXFOR-based simultaneous evaluation for neutron-induced fission cross section of plutonium-242

The $^{242}$Pu neutron-induced fission cross section was evaluated from 100 keV to 200 MeV. The experimental $^{242}$Pu and $^{235}$U fission cross sections and their ratios in the EXFOR library were reviewed and analysed by the least-squares method. Additional simultaneous evaluation was performed by including the experimental database of the $^{233,238}$U and $^{239,240,241}$Pu fission cross sections and their ratios developed for JENDL-5 evaluation. The $^{242}$Pu fission cross sections from our evaluation and JENDL-5 evaluation are close to each other below 1 MeV while systematically differ from each other above 10 MeV. The cross section from our evaluation is systematically lower than the JENDL-4.0 cross section in the prompt fission neutron spectrum peak region ($\sim$5% lower around 1 MeV). The newly evaluated $^{242}$Pu fission cross section was verified against the cross section measured in the $^{252}$Cf spontaneous fission neutron field and criticalities of small-sized LANL fast systems, and demonstrated better performance than the JENDL-4.0 cross section on the same level with the JENDL-5 cross section.Comment: Submitted to Journal of Nuclear Science and Technolog

Spin-dependent observables in surrogate reactions

Observables emitted from various spin states in compound U nuclei are investigated to validate usefulness of the surrogate reaction method. It was found that energy spectrum of cascading $\gamma$-rays and their multiplicities, spectrum of evaporated neutrons, and mass-distribution of fission fragments show clear dependence on the spin of decaying nuclei. The present results indicate that they can be used to infer populated spin distributions which significantly affect the decay branching ratio of the compound system produced by the surrogate reactions

Measurements of neutron total and capture cross sections of 139^{139}La and evaluation of resonance parameters

Neutron total and capture cross sections of Lanthanum(La)-139 were measured at the Accurate Ne-utron-Nucleus Reaction measurement Instrument (ANNRI) of the Materials and Life Science Experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC). The total cross section was largely different from that in evaluated libraries, such as JENDL-5, in the energy range from 80 to 900~eV. Resonance parameters for four resonances including one negative resonance were obtained using a resonance analysis code, REFIT. The resonance analysis revealed discrepancies in several resonance parameters with the evaluated libraries. Furthermore, the information about the scattering radius was also extracted from the results of the total cross section. The obtained scattering radius was larger than that recorded in the evaluated libraries.Comment: 12 pages, 16 figure