[en] Starting from a completely microscopic description of the nucleus, we try to extract the characteristic features of the collective dynamics of the fission phenomenon in the case of the ²⁴⁰Pu nucleus. In particular, we give an interpretation for the mechanism of the scission process

[en] Starting from a completely microscopic description of the nucleus, we try to extract the characteristic features of the collective dynamics of the fission phenomenon in the case of the ²⁴⁰Pu nucleus. In particular, we give an interpretation for the mechanism of the scission process

[en] In this final chapter, we summarize the calculations leading up to our estimates of fission-fragment properties following the induced fission of ²⁴⁰Pu. We conclude with a discussion of possible improvements to the theory, and experimental measurements that can shed light on the fission process and help guide the theory. We also give a brief survey of other theoretical approaches to the description of fission. (authors)

[en] Currently, the most relevant application of NMIS for plutonium attribute estimation stems from measurements performed jointly by Oak Ridge National Laboratory (ORNL) and Russian Federal Nuclear Center, All-Russia Scientific Research Institute of Experimental Physics (RFNC-VNIIEF) personnel at RFNC-VNIIEF facilities in Sarov, Russia in June and July 2000. During these measurements at VNIIEF, NMIS was applied in its passive mode to eight unclassified plutonium spherical shells. The shells' properties spanned the following ranges: Composition: (delta)-phase plutonium-metal, constant; Relative ²⁴⁰Pu-content (f_240Pu): f_240Pu = 1.77% (g ²⁴⁰Pu/g Pu), constant; Inner radius (r₁): 10.0 mm (le) r₁ (le) 53.5 mm, mean r₁ 33.5 mm; Outer radius (r₂): 31.5 mm (le) r₂ (le) 60.0 mm, mean r₂ = 46.6 mm; Radial thickness (Δr): 6.4 mm (le) Δr (le) 30.2 mm, mean Δr = 13.1 mm; and Plutonium mass (m_Pu): 1829 g (le) m_Pu (le) 4468 g, mean m_Pu = 3265 g. The features of these measurements were analyzed to extract the attributes of each plutonium shell. Given that the samples measured were of constant composition, geometry, and relative ²⁴⁰Pu-content, each shell is completely described by any two of the following four properties: Inner radius r₁; Outer radius r₂; Mass m, one of ²³⁹Pu mass m²³⁹_Pu, ²⁴⁰Pu mass m²⁴⁰_Pu, or total Pu mass m_Pu; and Radial thickness Δr. Of these, generally only mass is acknowledged as an attribute of interest; the second property (whichever is chosen) can be considered to be a parameter of the attribute-estimation procedure, much as multiplication is a parameter necessary to accurately estimate fissile mass via most neutron measurements

[en] Throughout the DOE complex, laboratories are performing calorimetric assays on items containing high burnup plutonium. These materials contain higher isotopic range and higher wattages than materials previously encountered in vault holdings. Currently, measurement control standards have been limited to utilizing 6% ²⁴⁰Pu standards. The lower isotopic and wattage value standards do not complement the measurement of the higher burnup material. Participants of the Calorimetry Exchange (CALEX) Program have identified the need for new calorimetric assay standards with a higher wattage and isotopic range. This paper describes the fabrication and verification measurements of the new CALEX standard containing 12% ²⁴⁰Pu oxide with a wattage of about 6 to 8 watts

[en] Angular anisotropies have been determined for 14 fission products in alpha induced fission of ²⁴⁰Pu using recoil catcher technique followed by gamma ray spectrometry. The data shows that angular anisotropies do not depend on the mass asymmetry. This is similar to the observation in ¹²C + ²³²Th system forming the same compound nucleus ²⁴⁴Cm, and is in sharp contrast to what has been observed in proton and alpha induced fission of thorium and uranium targets. (author). 5 refs., 1 fig

[en] Plutonium-239 (²³⁹Pu) and plutonium-240 (²⁴⁰Pu) activity concentrations and ²⁴⁰Pu/²³⁹Pu atom ratios are reported for Brown Algae (Fucus distichus) collected from the littoral zone of Amchitka Island (Alaska), and at a control site at Unalaska, Alaska. The average ²⁴⁰Pu/²³⁹Pu atom ratio observed in dried F. distichus collected from Amchitka Island was 0.227 ± 0.007 (N = 5) and compares with the expected ²⁴⁰Pu/²³⁹Pu atom ratio in integrated worldwide fallout deposition in the Northern Hemisphere of 0.1805 ± 0.0057. In the absence of any evidence of a local source of plutonium containing an elevated ²⁴⁰Pu/²³⁹Pu isotopic signature, the characteristically high ²⁴⁰Pu/²³⁹Pu content of F. distichus supports the view of the existence of a discernible, basin-wide non-fallout source of plutonium entering the subarctic Pacific. (author)

[en] Nuclear fission is studied from the point of view of a diffusion process. Based on the analytical formula of a simple model we propose considering the neutron competition during the total fission process (including equilibration process) as an example, the fission probability of ²⁴⁰Pu for various viscosities at different nuclear temperatures is calculated. The roles of the viscosity in the fission process are analyzed and discussed

[en] Neutron scattering cross-section of ²⁴⁰Pu have been investigated using an attractive potential. On applying the modified Pöschl-Teller model, the total cross-section of the n+²⁴⁰Pu in the energy range of 5-20 MeV have been calculated. It was compared with the available experimental data and evaluated data of JENDL-4.0, ENDF/B-VII.0 and CENDL-3.1 as well as with the theoretical values from TALYS-1.2 Nuclear Reaction Program, EMPIRE: 2.19 Nuclear Reaction Model Code and are found to be in reasonably good agreement. This supports the validity of the present calculation. (author)

[en] The authors evaluate the neutron cross-sections for ²⁴⁰Pu in the energy region from 10^-4 eV to 15 MeV on the basis of available experimental data and theoretical concepts of nuclear structure. The evaluated data are presented in the SOKRATOR format and have been transmitted to the Obninsk Nuclear Data Centre. (author)