Increased fuel burn up in a CANDU thorium reactor using weapon grade plutonium

Weapon grade plutonium is used as a booster fissile fuel material in the form of mixed ThO₂/PuO₂ fuel in a Canada Deuterium Uranium (CANDU) fuel bundle in order to assure the initial criticality at startup.Two different fuel compositions have been used: (1) 97% thoria (ThO₂) + 3%PuO₂ and (2) 92% ThO₂ + 5% UO₂ + 3% PuO₂. The latter is used to denaturize the new ²³³U fuel with ²³⁸U. The temporal variation of the criticality k_∞ and the burn-up values of the reactor have been calculated by full power operation for a period of 20 years. The criticality starts by k_∞ = 1.48 for both fuel compositions. A sharp decrease of the criticality has been observed in the first year as a consequence of rapid plutonium burnout. The criticality becomes quasi constant after the second year and remains above k_∞ > 1.06 for 20 years. After the second year, the CANDU reactor begins to operate practically as a thorium burner.Very high burn up could be achieved with the same fuel material (up to 500,000 MW·D/T), provided that the fuel rod claddings would be replaced periodically (after every 50,000 or 100,000 MW·D/T). The reactor criticality will be sufficient until a great fraction of the thorium fuel is burnt up. This would reduce fuel fabrication costs and nuclear waste mass for final disposal per unit energy drastically.     

Motion analysis for event detection and tracking with a mobile omnidirectional camera

A mobile platform mounted with omnidirectional vision sensor (ODVS) can be used to monitor large areas and detect interesting events such as independently moving persons and vehicles. To avoid false alarms due to extraneous features, the image motion induced by the moving platform should be compensated. This paper describes a formulation and application of parametric egomotion compensation for an ODVS. Omni images give 360 view of surroundings but undergo considerable image distortion. To account for these distortions, the parametric planar motion model is integrated with the transformations into omni image space. Prior knowledge of approximate camera calibration and camera speed is integrated with the estimation process using a Bayesian approach. Iterative, coarse-to-fine, gradient-based estimation is used to correct the motion parameters for vibrations and other inaccuracies in prior knowledge. Experiments with a camera mounted on various types of mobile platforms demonstrate successful detection of moving persons and vehicles.Published online: 11 October 2004     

Adaptive sliding mode control for trajectory tracking of nonholonomic mobile robot with uncertain kinematics and dynamics

ABSTRACT

This article designs a novel adaptive trajectory tracking controller for nonholonomic wheeled mobile robot under kinematic and dynamic uncertainties. A new velocity controller, in which kinematic parameter is estimated, produces velocity command of the robot. The designed adaptive sliding mode dynamic controller incorporates an estimator term to compensate for the external disturbances and dynamic uncertainties and a feedback term to improve the closed-loop stability and account for the estimation error of external disturbances. The system stability is analyzed using Lyapunov theory. Computer simulations affirm the robustness of the designed control scheme.     

Supporting design of primary shaped micro parts and systems through provision of experience

Nowadays, miniaturization is one observable trend in the development of new technical systems. Based on the miniaturization of existing macroscopic production technologies e.g. powder injection molding, a new process chain for the development of primary shaped microparts and systems is being developed in the collaborative research center 499 “design, production and quality assurance of molded micro components made of metallic and ceramic materials”. Because of the constantly evolving miniaturization and growing complexity of the developed microparts and systems, new development processes and methods are needed. Because of the mostly restrictive influence of the downstream phases (production and quality assurance) over the design phase, micro-specific design processes require well-founded knowledge about micro-specific manufacturing techniques (e.g. restrictions) which may be stored in form of design rules. However, many micro-specific aspects cannot be represented in design rules. In this paper the authors propose a new approach to ensure this other kind of knowledge.     

Experimental Implementation of New Sliding Mode Control Law applied To a DC–DC Boost Converter

The real implementation of sliding mode controllers (SMCs) to a DC–DC boost converter is a challenge due to the nonminimum phase behavior of these kinds of converters and the SMCs chattering problem. In this paper, new integral sliding mode control laws with linear and proposed nonlinear sliding surfaces are developed to overcome these problems. An experimental comparative study between these SMCs and the classical SMC applied for a DC–DC boost converter is presented.     

Tetrakis(alkylthio)-substituted lutetium bisphthalocyanines for sensing NO2 and O3

In this study, the nitrogen dioxide (NO₂) and ozone (O₃) sensing properties of a series bis[tetrakis(alkylthio) phthalocyaninato] lutetium(III) complexes [(C_nH_2n+1S)₄Pc]₂Lu(III) (n = 6, 10, 16) are investigated as a function of concentration in the temperature range between 25 °C and 150 °C. The concentration ranges were 1–10 ppm for NO₂, and 50 ppb–1 ppm for O₃. The response time and the sensor response to NO₂ are measured for approximately 1 min and 100% ppm⁻¹, respectively, for compound 1 at room temperature. At room temperature, all compounds are in the solid phase. The response time decreases to a few seconds with increasing operation temperature to 150 °C. At this temperature, all compounds are in the liquid crystal phase. The fastest response to oxidizing gases is observed at the liquid crystal phase of the Pcs. It has also been observed that the response time and the sensor response depend on the alkyl chain lengths of the Pcs. The doping effect of oxygen has been determined under high purity nitrogen N₂ flow, after exposure to dry air, at a different period of time and after annealing. It has been found that the conductivities of [(C_nH_2n+1S)₄Pc]₂Lu(III) thin films increased after exposure to dry air and the conduction mechanism also changed from ohmic behavior to space-charge-limited conduction.     

Interfacial energy of solid bismuth in equilibrium with Bi−In eutectic liquid at 109.5 °C equilibrating temperature

The interfacial energy of solid bismuth (Bi) in equilibrium with Bi−In eutectic liquid was determined for the equilibrating temperature of 109.5 °C. A radial temperature gradient on the sample was established by heating it from the center with a single heating wire and cooling the outside of the sample at −10 °C with a heating/refrigerating circulating bath containing an aqueous ethylene glycol solution. The equilibrated grain boundary groove shapes of solid Bi in equilibrium with Bi In eutectic liquid (Bi- 47.3 at. %In) were observed from a sample quenched at 109.5 °C. The Gibbs-Thomson coefficient and the solid-liquid interfacial energy of the solid Bi in equilibrium with Bi In eutectic liquid were determined to be (8.4±0.4) × 10⁻⁸ K m and (54.0±5.4)×10⁻³ J m⁻² from the observed grain boundary groove shapes. The grain boundary energy of the solid Bi phase was calculated to be (105.5±11.6)×10⁻³ J m⁻² by considering a force balance at the grain boundary grooves. The thermal conductivities of Bi-47.3 at. %In eutectic liquid phase and the solid Bi-47.3 at. %In phase and their ratio at 109.5 °C were measured with a radial heat flow apparatus and a Bridgman type growth apparatus.     

CANDU reactor as minor actinide/thorium burner with uniform power density in the fuel bundle

A CANDU reactor fueled with a mixed fuel made of thoria (ThO₂) and nuclear waste actinides has been investigated. The mixed fuel composition has been varied in radial direction to achieve a uniform power distribution and fuel burn-up in the fuel bundle.     

Hardness and electrical resistivity of Al–13 wt % Mg<Subscript>2</Subscript>Si pseudoeutectic alloy

In the present work, effect of growth rates on microhardness, electrical properties and microstructure for directionally solidified Al–13 wt % Mg₂Si pseudoeutectic alloy at a constant temperature gradient were studied. Directional solidification process were carried out with five different growth rates (V = 8.33–175.0 μm/s) at a constant temperature gradient (G = 6.68 K/mm) by using a Bridgman type directional solidification furnace. Microstructure of directionally solidified Al–13 wt % Mg₂Si pseudoeutectic alloy was observed as Mg₂Si coral-like structure phase dispersed into primary α-Al phase matrix. The electrical resistivity for Al–13 wt % Mg₂Si pseudoeutectic alloy, were measured by the d.c. four-point probe method. The dependency ofmicrohardness and electrical resistivity on growth rates were obtained as HV = 135.7 (V)^0.09 and ρ = 17.30 × 10^?8(V)^0.08, respectively for Al–Mg₂Si pseudoeutectic alloy. The results obtained in present work were compared with the previous similar experimental results.