[en] The principal method of einsteinium and fermium production is irradiation of curium or californium isotopes in a high-flux nuclear reactor. Large-scale manufacture of transplutonium elements developed at RIAR enables also to produce regularly significant quantities of einsteinium and fermium. In view of the fact that main routes for ²⁵⁵Es and ²⁵⁷Fm reactor production are as follows: (a) ²⁵²Cf(n, γ)²⁵³Cf(n, γ)²⁵⁴Cf(n, γ)²⁵⁵Cf(β^-)²⁵⁵Es(n, γ)²⁵⁶Es(β^-)²⁵⁶Fm(n, γ)²⁵⁷Fm; (b) ²⁵²Cf(n, γ)²⁵³Cf(β^-)²⁵³Es(n, γ)^254gEs(n, γ)²⁵⁵Es(n, γ)²⁵⁶Es(β^-)²⁵⁶Fm(n, γ)²⁵⁷Fm. Irradiation of curium targets should be continued until ²⁵²Cf output reaches its peak value. Calculation results of einsteinium and fermium isotopes accumulation during irradiation of curium or californium targets in high-flux nuclear reactor SM are presented in the report. Neutron cross-section values of curium, berkelium and californium isotopes are well-known and have been tested in our predictive calculation of ²⁵²Cf accumulation. On the contrary, neutron cross-section data for einsteinium and, especially, for fermium isotopes are scarce and rather discrepant. Effective cross-section values for some nuclear reactions, calculated on the basis of our experimental data on accumulation of einsteinium and fermium isotopes are also presented. Results of laboratory-scale research, procedures of radiochemical reprocessing of irradiated targets with curium, californium and einsteinium as well as characteristics of obtained ^253,254,255Es, ²⁵⁵Fm, ²⁵⁷Fm preparations are described. (author)

No abstract available

[en] The development of separation technologies for transuranium elements is reviewed from the initial systems involving few atoms to the present time when multi kilogram amounts require separation. The initial synthesis of element 101, Mendelevium is reviewed as it was the first preparation, isolation and identification of only 5 atoms in the discovery experiment. Separation processes for spent nuclear fuel and environmental remediation generally have used aqueous processes. The PUREX, TRUEX, TALSPEAK, DIAMEX and SANEX separation systems are reviewed application of non-aqueous processes to the treatment of radioactive waste is of growing interest as these have the advantage of providing higher radiation resistance using more compact equipment producing smaller amounts of secondary waste volume and having higher proliferation resistance than aqueous processes. (author)

No abstract available

[en] The hydrated radii and hydration numbers of the trivalent irons of Am, Cm, Cf, Es, Fm and Md have been derived from the measured migration velocities of these ions in an electric potential field and from Stokes' law. The migration velocities in several concentrations of aqueous perchlorate were determined and a minimum mobility, corresponding to maximum hydration, was observed for the ions of Cf and Es. We interpret our results in terms of changes in hydration, coordination number, ionic radius and ion formation with electrolyte composition and atomic number. Our actinide results are compared with lanthanide data. (author)

[en] The transitional fission state concept successfully used for description of the fragments' angular distributions (FAD) for spontaneous and low-energy induced fission of axial-symmetrical nuclei is correct if the spin projection of fissile nucleus (SPFN) onto its symmetry axis is the integral of motion for external region from the descent of fissile nucleus from external fission barrier to scission point. By heating of fissile nucleus in this region to the temperature T≅1 MeV, predicted by a lot of theoretical fission models, the Coriolis interaction uniformly mixes possible SPFN for a case of small spin values that leads to forgetting of the transitional fission states in asymptotical region where FAD are formed. In the frame of quantum-mechanical fission theory taking into account the deviations from A.Bohr's formula the FAD for spontaneously fissioning nucleus aligned by external magnetic field for superlow temperatures are calculated and it is shown that the analysis of the named FAD gives the possibility to solve the problem of SPFN conservation for external region

[en] The decay of ²⁵³Es, ²⁵⁴Es, ²⁵⁵Es isotopes prepared during irradiation of californium in central channel of high flux nuclear reactor SM-2 and separated during two cycles of separation of californium and einsteinium by means of ion exchange chromatography in the system of sulfo-cation exchanger - ammonium α-oxyisobutyrate is studied. Absolute intensities of gamma- and x-rays accompanying the decay of ²⁵³Es and half-life values of these isotopes are determined

[en] The techniques described here have been demonstrated to predict the contents of transplutonium element production targets, at least for isotopes of mass 253 or less. The HFIR irradiation model is a workhorse for planning the TRU processing campaigns, for certifying the heat evolution rate of targets prior to insertion in the reactor, for predicting future production capabilities over a multi-year period, and for making optimization studies. Practical considerations, however, may limit the range of available options so that optimum operation is not always achievable. We do intend, however, to keep fine-tuning the constants which define the cross sections as time permits. We need to do more work on optimizing the production of ₂₅₀Cm, ₂₅₄Es, ₂₅₅Es, and ultimately ₂₅₇Fm, since researchers are interested in obtaining larger quantities of these rare and difficult-to-produce nuclides. 7 figures, 2 tables

No abstract available

[en] During the explosion of the Hutch device, the target (²³⁸U and ²³²Th) was subjected to a very high neutron exposure, 2.4 x 10²⁵ neutrons /cm². Multiple neutron capture reactions resulted in the production of heavy nuclides, up to and including 257Fm. Results of the search for species with A > 257 were negative. The recovery and chemical processing of kilograms of Hutch debris has resulted in the isolation of 10¹⁰ atoms of 257Fm, which is 10² times more material than has been available for experimentation in the past. Experimentally significant amounts of other rare nuclides, e.g., :²⁵⁴Cf, ²⁵¹Cf, ²⁵⁵-Es, and ²⁵⁰Cm, have also been separated from the Hutch debris. The production of these nuclides in thermonuclear explosions is shown to be a valuable supplement to the AEC program for reactor production of transplutonium elements. The neutron flux achieved in Hutch was insufficient to even approach production of nuclides in the region of ²⁹⁸114. A much more intense neutron flux is required. In future experiments, considerable attention must be given to the problem of adequate sample recovery, in order to properly use the ability to subject targets to an exceedingly intense time-integrated neutron flux. (author)