[en] Savannah River National Laboratory estimated activities of various radionuclides in vapor phase associated with saltstone. These radionuclides, as well as the estimated activity and concentration of each in the gases phase are listed. Some of the activities are so low they should be considered zero. In particular, activity of the antimony and tin isotopes in the gas phase correspond to less than a molecule of gas per 340 m3 of vapor volume. Equilibrium calculations of the partitioning of each radionuclide between vapor and dissolved phases were done using the Geochemists Workbench (R). The conceptual model used was that 1 curie of each constituent was available to partition between vapor and dissolved phases. The overall assumption is that exposure would come from a single release of the vapor phase from a saltstone vault

No abstract available

[en] Full text: Exotic nuclei beyond the ¹³²Sn double-shell closure are influenced by both the Sn superfluidity and the evolving collectivity only few nucleons away. Toward even more neutron-rich nuclei, especially at intermediate mass number, interplay between single-particle and collective particle-hole excitations compete. In some cases with the extreme addition of neutrons also other effects as the formation of neutron skin [1], stabilization as sub-shell gaps [2], and/or orbital crossings [3] may be expected. The knowledge of nuclear ingredients is especially interesting beyond ¹³²Sn and little is known on how the excitations modes develop with the addition of both protons and neutrons [4-7] and for example systematic prompt and decay lifetime studies can be a very sensitive probe. Recently, we have approached this region of nuclei in several measurements following fission as ²³⁸U on ⁹Be target, within the EURICA project [8-9], n-induced fission on ²³⁵U/²⁴¹Pu targets using prompt-decay spectroscopy within the EXILL/FATIMA campaigns [10-11], as well as in decay spectroscopy at LOHENGRIN. Examples from these studies on several nuclei in the region will be presented together with the possible interpretation of the new data.

No abstract available

[en] The reduced M2 transition probabilities 11-/2₁ -> 7+/2₁ in the odd-A isotopes ^109-121Sn are found to reveal a specific behaviour. B(M2) values are calculated in the framework of the quasiparticle-phonon model. The coupling of a quasineutron with the 2⁺, 3^- and 2^- one-phonon core excitation is taken into account. Inclusion of all one-phonon 2^- states up to 24 MeV in the wave functions of the excited states 11-/2₁ and 7+/2₁ reduces the theoretical B(M2) values by 3-4 times as compared to the single particle values. The specific B(M2) dependence on the mass number appears to be due to the pairing effect. (orig.)

[en] A pairing interaction fitted to be applied in nuclei with active particles moving close to the continuum threshold or even immersed in the continuum itself is introduced. It is found that the effects of the nonresonant continuum upon physically meaningful quantities is unimportant. We applied the theory to heavy tin isotopes and good agreement between theory and the very few available experimental data is found

[en] The validity of the diagonal-pairing approximation is studied. It is shown that in the case of volume pairing the relaxation of the diagonal approximation affects the results in an infinitesimal way. A series of calculations in the diagonal approximation is performed for a number of nuclei. The nuclei of the ''magic +- 2 particles'' type, for which the approximation of developed pairing is not valid, are considered separately. The nucleon stability boundaries are studied in the example of the Sn and Pb isotopes

[en] Short communication

[en] We extend the study of multiphonon excitations in heavy ion collisions to the case of the pygmy resonances. The motivation of this study relies in our findings on multiphonon investigation [2] at low energy excitation. Indeed, we have found that a few low lying multiphonon states are excited in a heavy ion collision process with a quite strong probability. These states lay in the region of the pygmy resonances and the question is whether they may contribute to the observed peak. Starting from a microscopic approach based on RPA, mixing of two-phonon states among themselves and with one-phonon states is considered within a boson expansion approach with Pauli corrections. By diagonalizing a quartic microscopic Hamiltonian in the space of one-, two- and three-phonon states we generate mixing eigenstates with an anharmonic spectrum. Non linear terms are also taken into account in the external mean field of one of the nuclei which is responsible of the excitation of the other partner of the reaction. The inelastic cross section are calculated by solving semiclassical coupled channel equations, the channels being superpositions of one-, two- and three-phonon states. The calculations have been done for two different Skyrme interaction (SGII and SLY4) and for the reactions A^Sn + 2^08Pb at 500 MeV/A. We found an increase of the cross section in the low lying PDR energy region which is mainly due to the excitation of several states whose population is strongly suppressed by selection rules when anharmonicities and non-linearities are neglected. The increase varies from 3% up to 21% depending on the isotope considered and the Skyrme force used. In general, the SLY4 interaction produces a smaller anharmonicity which is then reflected in a lower increase of the cross section in the PDR region. On the contrary, the results obtained with the SGII show the importance of anharmonicities and non linearities for the study of the PDR. The pygmy resonance is much more evident in nuclei with neutron skin and it is thought to be generated by the oscillation of the neutron in excess with respect to the core. To the discussion whether or not this mode is a collective one we have contributed with a novel analysis based on the investigation of the coherent construction of the reduced transition probability which should unambiguously give an answer to this problem. Our results show that although the degree of collectivity is not as high as the one of the GDR, they are far to be considered as due to one p-h configuration. Indeed, while for the GDR, as it is very well known, many configurations contribute appreciably and add up coherently, in the PDR case there are several configurations contributing but some of them cancel out so that, finally, the reduced transition probability B(E1) is quite smaller than what one should get without such cancellations and of the same order of a single p-h configuration.(author)

[en] A self-consistent theory of finite Fermi systems is developed for superfluid nuclei at nonzero temperatures. Calculations are carried out for a chain of even Sn isotopes. The temperature dependence of the energy gap Δ(T) turns out to be similar to the square-root behavior known from the BCS theory. The critical temperature T_c at which pairing disappears varies from one nucleus to another because of a change in the level structure near the Fermi surface. However, the relation between T_c and Δ(0) proves to be close to that predicted by the BCS theory: T_c = 0.57Δ(0). The self-consistent theory confirms the main result, in which calculations were performed in the approximation of a fixed nuclear mean field: the size of a superfluid nucleus decreases with temperature. 13 refs., 6 figs., 3 tabs