Show simple document record

dc.contributor.advisorJay-Gerin, Jean-Paulfr
dc.contributor.authorSanguanmith, Sunuchakanfr
dc.date.accessioned2014-09-09T15:01:08Z
dc.date.available2014-09-09T15:01:08Z
dc.date.created2012fr
dc.date.issued2012fr
dc.identifier.isbn9780494909744fr
dc.identifier.urihttp://hdl.handle.net/11143/5548
dc.description.abstractA re-examination of our Monte-Carlo modeling of the high-temperature radiolysis of liquid water by low-linear energy transfer (LET~0.3 keV/[micro]m) radiation has been undertaken in an attempt to reconcile our computed g-values (primary yields) of the various radiolytic products (e[superscript -][subscript aq], ¨OH, H¨, H[subscript 2], and H[subscript 2]O[subscript 2]) with recently reevaluated experimental data over the range from 25 up to 350 [degrees]C. The temperature dependence of the rate constant for the self-reaction of the hydrated electron (e[superscript -][subscript aq]) measured under alkaline conditions, and in particular the abrupt drop observed above 150 [degrees]C, was assumed, in contrast to previous study, to be valid also in near-neutral pH water. To best reproduce the currently available temperature-dependent g-values, we found it necessary to introduce a discontinuity in the temperature dependence at 150 [degrees]C of certain parameters that intervene in the physicochemical stage of the radiolysis, including the thermalization distance (r[subscript]th) and the dissociative attachment (DEA) of subexcitation electrons, and the dissociative decay of electronically and vibrationally excited water molecules. With the exception of g(H[subscript 2]) above 200 [degrees]C, all calculated g-values were consistent with the general observation that when the temperature is increased, the yields of free radicals g(e[superscript]-[subscript]aq), g(¨OH), and g(H¨) increase while the molecular yield g(H[subscript 2]O[subscript 2]) decreases.Although H[subscript 2] is a molecular product, g(H[subscript 2]) was observed to continue to increase with temperature for a reason that has been a matter of controversy recently. Our simulations show that the reaction of H¨ atoms with water previously proposed by Swiatla-Wojcik and Buxton can indeed account for the anomalous increase in g(H[subscript 2]) at high temperature if we use for the rate constant of this reaction the value of 10[superscript 4] M[superscript 1] s[superscript -1] at 300 [degrees]C. Finally, as a direct application of the Fricke (ferrous sulfate) dosimeter, we have calculated the spur lifetime ([tau]s) and its temperature dependence. The results show that our calculated [tau]s value is decreasing from 4.2×10[superscript -7] to 5.7×10[superscript -8] s over the temperature range 25-350 [degrees]C.fr
dc.language.isoengfr
dc.publisherUniversité de Sherbrookefr
dc.rights© Sunuchakan Sanguanmithfr
dc.subjectDosimètre de Frickefr
dc.subjectTemps de vie des grappesfr
dc.subjectAttachement dissociatif de l'électronfr
dc.subjectDistance de thermalisation de l'électronfr
dc.subjectTELfr
dc.subjectRadicaux libres et produits moléculairesfr
dc.subjectValeurs Gfr
dc.subjectHaute températurefr
dc.subjectRadiolyse de l'eaufr
dc.subjectSimulation Monte-Carlofr
dc.titleLow-linear energy transfer radiolysis of liquid water at elevated temperatures up to 350[degrees]C Monte-Carlo simulationsfr
dc.typeMémoirefr
tme.degree.disciplineSciences des radiations et imagerie biomédicalefr
tme.degree.grantorFaculté de médecine et des sciences de la santéfr
tme.degree.levelMaîtrisefr
tme.degree.nameM. Sc.fr


Files in this document

Thumbnail

This document appears in the following Collection(s)

Show simple document record