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Browsing by Author "Krynicka, Ewa"

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    Feasibility study of experimental detection of the hydrogen content in rock material by a pulsed neutron method
    (Institute of Nuclear Physics Polish Academy of Sciences, 2003) Drozdowicz, Krzysztof; Drabina, Andrzej; Dąbrowska, Joanna; Gabańska, Barbara; Igielski, Andrzej; Janik, Władysław; Krynicka, Ewa; Kurowski, Arkadiusz; Wiącek, Urszula; Woźnicka, Urszula
    Theoretical principles of a pulsed neutron method to measure the water or hydrogen content in a rock material have been tested on the experimental set-up at the fast neutron generator in the INP. The time decay constant of the thermal neutron flux in the samples has been measured as a function of the hydrogen content. Dry crumbled granite has been used as a rock sample. The hydrogen content has varied due to addition of a defined amount of polyethylene (0 to 20 %). A few arrangements (neutron source + sample) have been tried. A dedicated pulsed thermal neutron source has been designed and built. The measuring set-up has been chosen for a final elaboration of the method.
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    Influence of the water content in rock on the thermal neutron diffusion and diffusion cooling coefficients (by Monte Carlo simulations). II: – Quartz
    (Institute of Nuclear Physics Polish Academy of Sciences, 2003) Drozdowicz, Krzysztof; Krynicka, Ewa; Dąbrowska, Joanna
    The dependence of the thermal neutron diffusion parameters on the water content w in quartz, SiO2, has been studied by means of Monte Carlo simulations of the pulsed neutron experiments for a number of series of samples. The density-removed diffusion cooling coefficient CM varies hyperbolically between 39 400 000 and 4940 cm4s–1(g/cm3)3 at the water content in the full range 0 ≤ w ≤.1. The obtained function CM(w) is compared with the analogous dependence for moisturized dolomite.
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    Measurements of the effective thermal neutron absorption cross-section in multi-grain model
    (Institute of Nuclear Physics Polish Academy of Sciences, 2005) Drozdowicz, Krzysztof; Gabańska, Barbara; Igielski, Andrzej; Krynicka, Ewa; Schneider, Krystyna; Woźnicka, Urszula
    The effective macroscopic absorption cross-section Σaeff of thermal neutrons in a grained medium differs from the corresponding cross-section Σahom in the homogeneous medium consisting of the same components, contributing in the same amounts. The ratio of these cross-sections defines the grain parameter, G, which is a measure of heterogeneity of the system for neutron absorption. Heterogeneous models have been built as two- or three-component systems (Ag, Cu and Co3O4 grains distributed in a regular grid in Plexiglas, in various proportions between them). The effective absorption cross-section has been measured and the experimental grain parameter has been found for each model. The obtained values are in the interval 0.34 < G < 0.58, while G = 1 means the homogeneous material.
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    Monte Carlo simulations of the pulsed thermal neutron flux in two-region hydrogenous systems (using standard MCNP data libraries)
    (Institute of Nuclear Physics Polish Academy of Sciences, 2005) Wiącek, Urszula; Krynicka, Ewa
    Monte Carlo simulations of the pulsed neutron experiment in two- region systems (two concentric spheres and two coaxial finite cylinders) are presented. The MCNP code is used. Aqueous solutions of H3BO3 or KCl are used in the inner region. The outer region is the moderator of Plexiglas. Standard data libraries of the thermal neutron scattering cross-sections of hydrogen in hydrogenous substances are used. The time-dependent thermal neutron transport is simulated when the inner region has a constant size and the external size of the surrounding outer region is variable. The time decay constant of the thermal neutron flux in the system is found in each simulation. The results of the simulations are compared with results of real pulsed neutron experiments on the corresponding systems.
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    Sensitivity of the Thermal Neutron Time Decay to the Hydrogen Content in a Rock Sample
    (Institute of Nuclear Physics Polish Academy of Sciences, 2004) Drozdowicz, Krzysztof; Dąbrowska, Joanna; Gabańska, Barbara; Igielski, Andrzej; Janik, Władysław; Krynicka, Ewa; Kurowski, Arkadiusz; Niedźwiedź, K.; Wiącek, Urszula; Woźnicka, Urszula
    A pulsed neutron method to measure the water or hydrogen content in a rock material has been tested on the experimental set-up at the fast neutron generator in the IFJ PAN. A dedicated pulsed thermal neutron source has been designed, built and added to this set-up. The test experiments have been done using dry crumbled granite as the rock matrix. The hydrogen content in samples has varied due to an addition of a defined amount of polyethylene. The time decay constant of the pulsed thermal neutron flux has been measured as a function of polyethylene content in granite+polyethylene samples. The experimental results have been supplemented with Monte Carlo simulations of the experiments. Analytical estimations of the time decay constant in the examined geometry have also been done. Difficulties of the proposed experimental method at low values of the hydrogen content are discussed. The proposed method using the pulsed neutron source to determine the hydrogen content which is less than 10 %, can be applied for rock samples of volume about 30 dm3. For higher hydrogen content the volume of the sample can be lower – about 7 dm3.