[en] Evaluated: January 2007/February 2009. Updated comments: 2010. Evaluation Procedure: Limitation of Relative Statistical Weight Method (LWM) was applied to average the decay data when appropriate (but see below). Decay Scheme: A relatively simple decay scheme was constructed from the branching fraction measurements of Fields et al. and Gabeskipiya et al. (1955Fi36, 1976Ga31) and the gamma-ray studies of Hoff et al. (1984Ho02). Only the gamma-ray studies of Hoff et al. provide estimates of the gamma-ray emission probabilities and their uncertainties per 100 neutron captures. Thus, no weighted mean data could be derived, and the data of 1984Ho02 were adopted as published

No abstract available

[en] Evaluated: January 2007/February 2009. Updated comments: Dec. 2010. Evaluation Procedure: Limitation of Relative Statistical Weight Method (LWM) was applied to average the decay data when appropriate (but see below). Decay Scheme: A relatively simple decay scheme was constructed from the gamma-ray studies of 1962Va08, 1963Ha29, 1967Sc34 and 1984Ho02. Only the gamma-ray measurements of Hoff et al. provide any estimates of the uncertainties in the gamma-ray probabilities expressed in terms of their relative intensity per 100 neutron captures in a high-flux reactor (1984Ho02). All other studies contained no information with respect to their overall uncertainties. Thus, no weighted mean data could be derived, and the data of 1984Ho02 were adopted wholesale and re-adjusted when deemed necessary (expressed in terms of the 743.977-keV gamma-ray emission probability (100%)). Further measurements are merited to quantify the gamma-ray emission probabilities and decay scheme with greater certainty

[en] Fractional cumulative yields (FCY) of various heavy mass fission products in the 128-148 mass region were determined in the fast neutron induced fission of ²⁴¹Am using radiochemical and off-line gamma ray spectrometric technique. From the FCY values the width parameter (σ_z), most probable charge (Z_p) and charge polarization (ΔZ= Z_p-Z_UCD) were obtained for various mass chains using Gaussian distribution. It was observed that the σ_z and ΔZ in the mass regions 128-130 and 134-136 are lower than other masses due to the presence of spherical 50p and 82n shells respectively. This indicates the effect of shell closure proximity on charge distribution parameters. From the σ_z values the average width parameter (<σ_z²>) for the fissioning system ²⁴⁴Am is obtained to be 0.58±0.05 and is determined for the first time. The average charge variance (<σ_z²>) of the fissioning system ²⁴⁴Am from the present work and for the other fissioning systems from earlier work show an increasing trend with the fissility parameter (Z_^F2/A_F). This is explained from the point of neck snapping (dc/dt) i.e. the rate at which neck pinches off. (author)

[en] Published in summary form only. 1 fig

[en] The status of experimental determination of level structure in odd-odd actinide nuclei is reviewed. A technique for modeling quasiparticle excitation energies and rotational parameters in odd-odd deformed nuclei is applied to actinide species where new experimental data have been obtained by use of neutron-capture gamma-ray spectroscopy. The input parameters required for the calculation are derived from empirical data on single-particle excitations in neighboring odd-mass nuclei. Calculated configuration-specific values for the Gallagher-Moszkowski splittings are used. Calculated and experimental level structures for ²³⁸Np, ²⁴⁴Am, and ²⁵⁰Bk are compared, as well as those for several nuclei in the rare-earth region. The agreement for the actinide species is excellent, with bandhead energies deviating 22 keV and rotational parameters 5%, on the average. Applications of this modeling technique are discussed

[en] The nuclear fission is one of the most complex nuclear phenomena in nature and many aspects remain only partially understood even in the 75^th year of its discovery. The third minimum has been discussed in the literature for many nuclides like thorium isotopes. The mic-mac approach with Cassini Ovaloid Shape parameterization for the nuclear potential has been utilized to calculate the potential energy surfaces in the actinides. This formalism is due to Garcia et al. The aim of the work is to search for the triple-humped fission barrier which may support the existence of hyper-deformed isomers. The paper look into such a hyper-deformed isomer near the magic numbers predicted around the 3:1 shapes. For the anisotropic-oscillator, the deformed magic numbers for the axes ratio 2:1 are 2, 4, 10, 16, 28, 40, 60, 80, 110, 140 and 182, which are also upwardly modified due to the spin-orbit term as recently shown for the super-deformed nuclei similar to the harmonic oscillator potential for spherical magic numbers. As we go to the higher deformation at 0.86 with axes ratio 3:1, the numbers become 2, 4, 6, 12, 18, 24, 36, 48, 60, 80, 100, 120, 150, 180, and 210. The spin-orbit interaction will modify these numbers upwards too. Therefore, the search for the third well near those magic numbers which lie in the actinide region is focussed. The potential energy surfaces are calculated for the nuclei having Z = 93 to 96 and N ∼ 150 for the search of triple-hump barrier. The calculations show that the third well corresponding to the 3:1 shell structure begins to appear in the deformation range 0.7-0.8 near neutron number 150 and above. The outer barrier decreases as we go from Z=93 to 95 due to increasing Coulomb energy contribution to the barrier. It starts to be more flat and leads to the existence of the deeper third well in the neutron-rich side of the particular isotopic chain. These calculations show that the Am nuclides may be the best candidates for third minimum. The deepest third minimum is observed in ²⁵⁰Am with a depth of 1.29 MeV. The next possible candidate is ²⁵¹Am. However, the experimentally accessible isotopes may be ^244,245Am. These nuclides have sufficiently deep minimum to observe hyper-deformed isomer. However, further calculations are in progress to establish this

[en] In reactor irradiation several trans-uranium elements, collectively termed as minor actinides, are produced. When exposed to neutrons, a large number of heavy actinide isotopes are expected to be produced, and, for many of them decay data is scarce. One such example is ²⁴⁴Am which is formed in the neutron irradiation of the long-lived ²⁴³Am. ²⁴⁴Am has a metastable isomer ²⁴⁴Am^m in addition to ²⁴⁴Am^g. The experimental data of the gamma-ray abundances of ²⁴⁴Am^m,g has large uncertainties which are of the order of ~30%). The uncertainties on the half-life of ²⁴⁴Am^m,g are also large. In the present measurements, a new gamma-ray of energy of 940.5 keV has been observed in addition to the 941.95 keV gamma-ray reported in literature

[en] In the present paper the cluster decay process ³²Si from ^233-247Cm and ^231-244Am, ³³Si from ^233-248Cm, ³⁴Si from ^233-249Cm and ^231-246Am has been investigated. All the parent-cluster combinations, where the experimental results were available have been considered. Calculations are done within the Coulomb and proximity potential model (CPPM) have been predicted

[en] Full text: In the nuclear waste management policy, beside the direct disposal, the separation of actinides from lanthanides is an important step for the alternative methods currently under development, e.g. partition and transmutation or conditioning. Partitioning (separation) and transmutation of long-lived radionuclides contained in spent fuel into shorter-lived or stable elements by neutron irradiation could be a solution for reducing the storage time of the waste. To be able to transmute the most long-lived elements, it is necessary to separate them from the rest of the waste. This separation may be carried out in several steps. First step is the PUREX process (Plutonium Uranium Redox EXtraction). Then, actinides (III) and lanthanides (III) are co-extracted from the remaining waste with a diamide extractant; this is the DIAMEX process (DIAMide EXtraction). Then, actinides and lanthanides are separated by the SANEX process (Selective ActiNide EXtraction). The principle of solvent extraction involves the distribution of a solute between two immiscible liquid phases in contact with each other. In this case, the organic phase consists of an organic molecule, the extractant (which is a soft donor ligand), dissolved in a diluent. The aqueous phase contains traces amounts of actinides and lanthanides (in this case ²⁴⁴Am and ¹⁵²Eu were chosen). In a solvent extraction process, changes in the parameters of the organic or aqueous phases, such as structural variations of the reactants, diluents, pH, temperature etc., can deeply affect the extraction. For this reason a good understanding of the chemistry of the extraction is needed. The influence of the solvent is one of the most important features, because this can influence the distribution ratio and also the separation factor. Beside this, for the environmental purpose, this should be chosen in order to fulfil all the present demands (the CHON principle). (author)