A 5 Mg/annum Combined Electrolysis Catalytic Exchange (CECE) Facility was designed, constructed and operated to demonstrate the CECE process for heavy water detritiation. In this demonstration facility, a liquid-phase catalytic exchange (LPCE) column, using AECL's wetproofed catalyst, separated tritium from deuterium and a specially designed, low-inventory electrolytic cell provided tritium-enriched deuterium to the LPCE column. An overhead recombiner, also using wetproofed catalyst, produced detritiated heavy water. Tritium was removed from the electrolysis cell as tritiated deuterium gas and packaged as a titanium deuteride. The design detritiation factor of 100 was readily achieved using a 370 GBq/kg heavy water feed. Design features, operational experience and results from the 4-month, 2 000-h operation are described.
Catalytic recombiners appear to be a credible option for hydrogen mitigation in nuclear containments. The passive operation, versatility and ease of back fitting are appealing for existing stations and new designs. Recently, a generation of wet-proofed catalyst materials have been developed at AECL which are highly specific to H{sub 2}-O{sub 2}, are active at ambient temperatures and are being evaluated for containment applications. Two types of catalytic recombiners were evaluated for hydrogen removal in containments based on the AECL catalyst. The first is a catalytic combustor for application in existing air streams such as provided by fans or ventilation systems. The second is an autocatalytic recombiner which uses the enthalpy of reaction to produce natural convective flow over the catalyst elements. Intermediate-scale results obtained in 6 m{sup 3} and 10 m{sup 3} spherical and cylindrical vessels are given to demonstrate self-starting limits, operating limits, removal capacity, scaling parameters, flow resistance, mixing behaviour in the vicinity of an operating recombiner and sensitivity to poisoning, fouling and radiation. (author). 13 refs., 10 figs.
Abstract A combined experimental and theoretical investigation of the effect of forced feed composition cycling for CO oxidation on platinum has been performed. A novel approach to forced composition cycling was examined, in which the phase angle between the two input streams was varied. Reaction rate enhancement is shown to occur, and by varying the phasing of the feed streams it is possible to achieve a global maximum in the time‐average reaction rate. This phenomenon can be explained quantitatively by a model based on an adsorbate‐induced phase change of the Pt surface combined with CO adsorption self‐exclusion. This mathematical model can also quantitatively describe the complex steady‐state behavior (uniqueness‐multiplicity transitions) observed for this reaction. The predictions of the model have been validated further through a detailed experimental study of the effects of feed flow rate, temperature, size of catalyst charge, and cycling frequency on the instantaneous and time‐average conversions during forced cycling of the feed composition.
Abstract An experimental determination of the steady state behavior for the supported platinum catalyzed oxidation of carbon monoxide in a recycle reactor was performed. Steady state multiplicity was observed. The effects of the size of catalyst charge, feed flow rate, feed composition, and reactor temperature on the location of the boundaries of the steady state multiplicity region were determined. The sensitivity of these bifurcation points to variations in reactor parameters was used to discriminate among five reaction mechanisms. Only an elementary step model incorporating carbon monoxide self‐exclusion from the catalyst surface could quantitatively describe all observed steady state data. An explicit rate function based on this model is presented.
A combined experimental and theoretical investigation of the effect of forced feed composition cycling for CO oxidation on platinum has been performed. Reaction rate enhancement is shown to occur, and a quantitative explanation of this phenomenon is possible by a newly developed model based on an adsorbate induced phase change of the Pt surface. This mathematical model can also quantitatively describe the complex steady-state behavior (uniqueness-multiplicity transitions) observed for this reaction.
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