Radiolysis of supercritical water at 400[degrees]C and liquid-like densities near 0.5 g/[cm.sup.3]--a Monte Carlo calculation

Citation metadata

Date: July 2010
From: Canadian Journal of Chemistry(Vol. 88, Issue 7)
Publisher: NRC Research Press
Document Type: Report
Length: 5,335 words

Document controls

Main content

Abstract :

Monte Carlo simulations are used to calculate the primary radical yields g([e.sub.aq.sup.-]), g([sup.*]OH), the sum [g([e.sub.aq.sup.-]) + g([sup.*]OH) + g([H.sup.*])], and the ratio g([H.sup.*])/g([e.sub.aq.sup.-]) in the low linear energy transfer (LET) radiolysis of supercritical water (SCW) at 400[degrees]C in the high-density, liquid-like region near ~0.5 g/[cm.sup.3]. Using all the currently available information on the reactivities and diffusion coefficients of the radiation-induced species under these conditions, and assuming the aqueous medium to be a "continuum", a good accord is found between our calculations and the available experimental data. In particular, our computed [e.sub.aq.sup.-] yields at 60 ps and 1 ns compare very well with recently reported direct time-dependent [e.sub.aq.sup.-] yield measurements in SCW ([D.sub.2]O) at 400[degrees]C and 0.570 g/[cm.sup.3] using picosecond pulse radiolysis experiments. Key words: supercritical water, radiolysis, hydrated electron, [sup.*]H radical, [H.sup.*] atom, rate constants, diffusion coefficients, primary radiolytic yields (g values), Monte Carlo track structure simulations. A l'aide de simulations Monte Carlo, nous avons calcule, pour des rayonnements de faible transfert d'energie lineique (TEL), les rendements primaires radicalaires (g([e.sub.aq.sup.-])), g([sup.*]OH), la somme [g([e.sub.aq.sup.-]) + g([sup.*]OH) + g([H.sup.*])] et le rapport g([H.sup.*])/g([e.sub.aq.sup.-]) intervenant lors de la radiolyse de l'eau a l'etat supercritique (ESC) a 400[degrees]C dans la region de haute densite; de type liquide autour de ~0,5 g/[cm.sup.3]. En utilisant toute les renseignements actuellement disponibles sur les reactivites et les coefficients de diffusion des especes radio induites dans ces conditions et en considerant le milieu aqueux comme un , un bon accord a ete trouve entre nos calculs et les donnees experimentales existantes. En particulier, nos rendements calculesen electrons hydrates ([e.sub.aq.sup.-])a 60 ps et 1 ns s'accordent tres bien avec les mesures directes obtenues en radiolyse pulsee picoseconde du rendement en [e.sub.aq.sup.-] dans l'ESC ([D.sub.2]O) a 400[degrees]C et 0570 g/[cm.sup.3]. Mots-cles: eau supercritique, radiolyse, electron hydrate, radical [sup.*]H, atome [H.sup.*], constantes de vitesse de reaction, coefficients de diffusion, rendements primaires radiolytiques (valeurs g), simulations Monte Carlo de structure de trajectoire.

Source Citation

Source Citation   

Gale Document Number: GALE|A231996717