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Evaluation of Homolytic Dissociation Energies by Quantum Mechanical Methods

100%
Postolache C., Fugaru V., Tuta C., Bubueanu G.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
891-894
EN
In this paper we propose a quantum mechanical evaluation model for homolytic dissociation energies. Using AM1 and PM3 semi-empirical methods we have characterized molecular structures and fragments that resulted from the chemical bond dissociation. Total binding energies were determined for the geometrically optimized molecular structures of fragments that resulted due to the breaking of chemical bonds, as well as for transitional states. The reaction enthalpy and activation energies were correlated with homolytic dissociation energies. Accuracy of the method and application fields of different evaluation modalities were achieved by the intercomparison of obtained values with experimental ones found in literature. More than 74 organic and inorganic compounds were analyzed.
2
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Behavior of Fluoropolymers in Presence of Tritiated Water

100%
Bubueanu G., Postolache C., Fugaru V., Tuta C.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1363-1366
EN
The behaviour of Polytetrafluoroethylene (PTFE), NAFION ionomer membranes and VITON fluoroelastomer in presence of high activity tritiated water (HTO) was analysed. Radiolytic stability of the fluoropolymers-HTO system was analysed by: (a) Simulation of radiolytic processes by quantum mechanical methods, (b) Simulation of radiolytic effects by exposure of fluoropolymers immersed in H₂O to ^{60}Co gamma radiation field, (c) Immersing of fluoropolymers samples in HTO with high activity, for different time periods. In both cases the samples were characterized by FT IR ATR, and study of emission of fluoride ions from polymer matrix.
3
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Facility for Removal and Determination of Labile Tritium

76%
Tuta C., Postolache C., Fugaru V., Bubueanu G., Manea S., Bercea S.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
895-897
EN
Tritium bonded to electrophilic atoms like O, S, N or halogens can spontaneously exchange places with hydrogen from the water. These tritium species are exchanged even at a very low temperature and have the generic name `labile'. In this paper, a new facility for the removal and quantitative determination of labile tritium is shown. The working principle is as follows: tritium sources are brought in contact with protic solvent, leading to a spontaneous exchange of labile tritium, then the obtained tritiated solvent is extracted by distillation. The new facility was tested for removal efficiency of labile tritium from labeled compounds and wastes with different compositions.
4
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Gamma Ray Shielding Properties of Some Concrete Materials

76%
Fugaru V., Bercea S., Postolache C., Manea S., Moanta A., Petre I., Gheorghe M.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 4
1427-1429
EN
Concrete of various type have been used extensively for the adequate shielding of the radiological equipment using X and gamma rays. In its basic form, concrete is composed of pieces of inert aggregate held together by hardened cement paste. Different concrete types with special cements have been prepared. The linear attenuation coefficients of conventional concrete and concrete with supplementary mineral additives (barite and witherite) at different gamma energies (Co-60: 1.25 MeV, Cs-137: 0.662 MeV, Ir-192: 0.37 MeV) in narrow beam conditions have been measured. This paper includes some experimental data regarding the influence of barite and witherite additives on photon attenuation coefficients of concrete.
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