“Acid-spike” effect in spurs/tracks of the low/high linear energy transfer radiolysis of water : potential implications for radiobiology and nuclear industry

Hydronium ions (H3O+) are formed within spurs or tracks of the low or high linear energy transfer (LET) radiolysis of pure, deaerated water at early times. The in situ radiolytic formation of H3O+ renders the spur and track regions temporarily more acid than the surrounding medium. Although experimental evidence for an acidic spur has already been reported, there is only fragmentary information on its magnitude and time dependence. In this work, spur or track H3O+ concentrations and the corresponding pH values are obtained from our calculated yields of H3O+ as a function of time, using Monte Carlo track chemistry simulations. We selected four impacting ions and we used two different spur and track models: 1) an isolated “spherical” spur model characteristic of low-LET radiation and 2) an axially homogeneous “cylindrical” track model for high-LET radiation. Very good agreement was found between our calculated time evolution of G(H3O+) in the radiolysis of pure, deaerated water by 300-MeV incident protons (which mimic 60Co gamma/fast electron irradiation) and the available experimental data at 25 °C. For all cases studied, an abrupt transient acid pH effect, which we call an “acid spike”, is observed during and shortly after the initial energy release. This acid-spike effect is virtually unexplored in water or in a cellular environment subject to the action of ionizing radiation, especially high-LET radiation. In this regard, this work raises a number of questions about the potential implications of this effect for radiobiology, some of which are briefly evoked. Our calculations were then extended to examine the effect of temperature from 25 to 350 °C on the yield of H3O+ ions that are formed in spurs of the low-LET radiolysis of water. The results showed an increasingly acidic spike response at higher temperatures. As many in-core processes in a water-cooled nuclear reactor critically depend on pH, the question here is whether these variations in acidity, even highly localized and transitory, contribute to material corrosion and damage.

Name thesis:degree_name

M. Sc.

Level thesis:degree_level

Maîtrise

Discipline thesis:degree_discipline

Sciences des radiations et imagerie biomédicale

Grantor dc:publisher

Université de Sherbrooke

Year dc:date.issued

2016

Author dc:creator

• Kanike, Vanaja

Advisor dc:contributor.advisor

• Jay-Gerin, Jean-Paul

• Eau liquide
• Radiolyse
• Transfert d'énergie linéaire (TEL)
• Structure de trajectoire
• Grappe
• Simulations Monte Carlo de la chimie de trajectoires
• Ion hydronium (H3O+)
• Rendement radiolytique (valeur G)
• Liquid water
• Radiolysis
• Linear energy transfer (LET)
• Track structure
• Spur
• Monte Carlo track chemistry simulations
• Hydrogen ion (H3O+)
• Radiation chemical yield (G-value)

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-sa/2.5/ca/

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/11143/9711

OAI identifier oai:identifier

oai:usherbrooke.scholaris.ca:11143/9711