title: Effect of temperature on the low-linear energy transfer radiolysis of the ceric-cerous sulfate dosimeter: a Monte Carlo simulation study.
abstract: The stochastic modeling of the (60)Co γ/fast-electron radiolysis of the ceric-cerous chemical dosimeter has been performed as a function of temperature from 25-350°C. The system used is a dilute solution of ceric sulfate and cerous sulfate in aqueous 0.4 M sulfuric acid. In this system, H(•) (or HO2(•) in the presence of dissolved oxygen) and H2O2 produced by the radiolytic decomposition of water both reduce Ce(4+) ions to Ce(3+) ions, while (•)OH radicals oxidize the Ce(3+) present in the solution back to Ce(4+). The net Ce(3+) yield is given by G(Ce(3+)) = g(H(•)) + 2 g(H2O2) - g((•)OH), where the primary (or "escape") yields of H(•), H2O2 and (•)OH are represented by lower case g's. At room temperature, G(Ce(3+)) has been established to be 2.44 ± 0.8 molecules/100 eV. In this work, we investigated the effect of temperature on the yield of Ce(3+) and on the underlying chemical reaction kinetics using Monte Carlo track chemistry simulations. The simulations showed that G(Ce(3+)) is time dependent, a result of the differences in the lifetimes of the reactions that make up the radiolysis mechanism. Calculated G(Ce(3+)) values were found to decrease almost linearly with increasing temperature up to about 250°C, and are in excellent agreement with available experimental data. In particular, our calculations confirmed previous estimated values by Katsumura et al. (Radiat Phys Chem 1988; 32:259-63) showing that G(Ce(3+)) at ∼250°C is about one third of its value at room temperature. Above ∼250°C, our model predicted that G(Ce(3+)) would drop markedly with temperature until, instead of Ce(4+) reduction, Ce(3+) oxidation is observed. This drop is shown to occur as a result of the reaction of hydrogen atoms with water in the homogeneous chemical stage.
authors.affiliation: Département de Médecine Nucléaire et de Radiobiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke (Québec) J1H 5N4, Canada.
authors.forename: Leila Mirsaleh
authors.initials: LM
authors.lastname: Kohan
authors.forename: Jintana
authors.initials: J
authors.lastname: Meesungnoen
authors.forename: Sunuchakan
authors.initials: S
authors.lastname: Sanguanmith
authors.forename: Ridthee
authors.initials: R
authors.lastname: Meesat
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Jay-Gerin
mesh_terms: D002563:Cerium / Q000737:chemistry*; D003037:Cobalt Radioisotopes; D003198:Computer Simulation; D006861:Hydrogen Peroxide / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical; D018499:Linear Energy Transfer; D008956:Models, Chemical; D009010:Monte Carlo Method; D009688:Nuclear Reactors; D010084:Oxidation-Reduction; D010782:Photolysis; D011830:Radiation Effects; D011874:Radiometry / Q000295:instrumentation*; D012996:Solutions; D013053:Spectrophotometry; D013269:Stochastic Processes; D013431:Sulfates / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D003037:Cobalt Radioisotopes; D012996:Solutions; D013431:Sulfates; D013464:Sulfuric Acids; D014867:Water; D002563:Cerium; D017665:Hydroxyl Radical; C042259:ceric sulfate; D006861:Hydrogen Peroxide; C033158:sulfuric acid