Clara WrenClara Wren
Professor
B.Sc. (Hons), Sogang University, South Korea
Ph.D., Kansas State University
Office: Chemistry 016. Lab: Chemistry 040
Phone (Office): 519 661-2111 ext 86339

jcwren@uwo.ca

Research Group Homepage

Chemical Kinetics and Transport Phenomena in Radiation-Induced Processes



Awards:

    NSERC/AECL Industrial Research Chair

Current Research Programs:

My primary research aim is the application of chemical kinetics analysis and modelling to complex chemical systems of practical interest. The field of applied chemical kinetics has a wide range of practical applications, from environmental studies to industrial problems, such as the rate of ozone depletion in the atmosphere, containment transport in ground waters, chemical evolution of mine tailings, the rate of pipeline corrosion, etc. The solution to such problems lies in an integrated approach, combining experimental and modelling studies.

A primary focus is the study of the chemical reactions and transport phenomena occurring in ionizing radiation environments for nuclear safety and material integrity issues.  High radiation fields create a dynamic chemical environment, particularly in systems where water is present.  Radiolysis of water produces highly reactive radicals (•OH, •H, eaq-, •HO2 and •O2) and molecular species (H2, O2 and H2O2).  The reactions of these species are often responsible for the evolution of the chemistry and the degradation of the materials of nuclear reactor systems. 

Particular interests are: (a) the chemistry and transport phenomena in nuclear reactor containment buildings under postulated accident conditions, especially the volatility of radioiodine and the production of potentially explosive hydrogen, and: (b) the influence of redox conditions on materials in high temperature/pressure reactor coolant systems. These systems are kinetically complex because the radiolysis products are highly reactive and interact with a large number of chemical species and surfaces in a multiphase, geometrically complex engineered system.

Research topics to address these issues include: (a) the impact of dissolved trace metals and nitrogen-containing compounds on the radiolysis behaviour of water, (b) the effects of metal/metal oxide surfaces on radiolysis and redox chemistry, (c) radiation-induced reactions of iodine and organic compounds in aqueous solutions, (d) the interaction of gaseous iodine with, and accompanying iodine-assisted corrosion of, metals/metal oxides, and (e) mass and heat transport of iodine and water vapour through a charcoal bed under flow conditions.

The development of solutions to such complex problems requires a combination of experimental and modelling approaches. Our experimental approach includes irradiation of samples in a g-irradiation cell, the use of a radioactive iodine tracer (131I) accompanied by analysis using gamma spectrometry, and the use of standard chemical analytical techniques such as Gas Chromatography – Mass Spectrometer (GC-MS), High Performance Liquid Chromatography (HPLC), Fourier Transform Infrared (FTIR) Spectroscopy, UV-Vis. Spectroscopy, etc. For the study of surface reactions, these methods are supplemented by various electrochemical techniques (e.g., Electrochemical Impedance Spectroscopy) and surface analysis methods (e.g., Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy).

Modelling approaches include the simulation of the chemical kinetics and transport processes occurring in laboratory-scale experiments and their expansion to the modelling of full-scale systems. The coupled rate equations of the processes are solved using commercially available numerical integration software such as FACSIMILE and FEMLAB. For a given system, comprehensive mechanistic models are first developed. Parametric and sensitivity analyses of the comprehensive models are then used to develop simpler models for practical applications. The creation and validation of practical models is a sophisticated exercise in chemical kinetic analysis.

We are currently looking for graduate students (MSc and/or PhD). If you are interested, please contact us.

Selected Publications:

P.A. Yakabuskie, J.M. Joseph, J.C. Wren, The Effect of interfacial Mass Transfer on Steady-State Water Radiolysis, Rad. Phys. Chem.,79, 777-785 (2010)

K.Yazdanfar, X. Zhang, P.G. Keech, D.W. Shoesmith, J.C. Wren, Film Conversion and Breakdown Processes on Carbon Steel in the Presence of Halides, Corrosion Science, 52 1297-1304 (2010)

D. Fu, X. Zhang, P.G. Keech, D.W. Shoesmith, J.C. Wren, An electrochemical study of H2O2 decomposition on single-phase ?-FeOOH films, Electrochimica Acta, 55, 3787-3796 (2010)

K. Daub, X. Zhang, J.J. Noel, J.C. Wren, Effects of gamma-Radiation versus H2O2 on Carbon Steel Corrosion, Electrochimica Acta, 55, 2767-2776 (2010)

W. Xu, K. Daub, X. Zhang, J.J. Noel, D.W. Shoesmith, J.C. Wren, “Oxide Formation and Conversion on Carbon Steel in Mildly Basic Solutions”, Electrochimica Acta, 54, 5727-5738 (2009)

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