Integral Fast Reactor Program annual progress report, FY 1994

This report summarizes highlights of the technical progress made in the Integral Fast Reactor (IFR) Program in FY 1994. Technical accomplishments are presented in the following areas of the IFR technology development activities: metal fuel performance; pyroprocess development; safety experiments and analyses; core design development; fuel cycle demonstration; and LMR technology R&D

Experimental and Analytical Study of Silica Particles on Self-Healing Concrete

This study aims to investigate the properties of green concrete made with ground granulated blast-furnace slag (GGBS), Robo sand (RS), and coconut shell (CS). GGBS is the mineral admixture used to replace cement. Nano-silica particles (NSPs) and CS are used as coarse aggregates, and RS is the fine aggregate used to replace river sand. The workability, mechanical properties, and durability properties of green concrete are investigated and compared with those of conventional concrete (CC). Test results show that the cement replaced with 30% GGBS and 3% NSPs exhibits superior strength. The compressive and splitting tensile strengths are increased by 24.03% and 42.32% after 28 days of curing, respectively. The workability is improved by 12.22% (slump) and 13.25% (compaction factor) after 28 days of curing. The sorptivity of HM3 (3.26%) is lower than that of CC due to the uniform distribution between particles. Microstructure evolution is carried out to identify concrete mix behavior

Research and technology

The NASA Lewis Research Center's research and technology accomplishments for fiscal year 1987 are summarized. It comprises approximately 100 short articles submitted by staff members of the technical directorates and is organized into four sections: aeronautics, aerospace technology (which includes space communications), space station systems, and computational support. A table of contents by subject was developed to assist the reader in finding articles of special interest

Application of LQR and MPC on Distillation and Batch Crystallization Process

As the widespread use of a batch crystallization process in many industries, finding an optimal operating condition and effective control strategy are significant for improving product quality and downstream processing. To achieve these, an accurate model is required to predict the process behavior and to design controller. However, due to unknown disturbances and batch-to batch variations, the kinetic parameters obtained from experimental study may not represent the real process resulting in poor control and estimation performances. In this work, improvement of batch crystallization control under uncertain kinetic parameters has been proposed. Model predictive controller (MPC) is used for optimal control of distillation and batch crystallization process. Feedback control strategy is found out using LQR technique. A Kalman filter has been designed to estimate uncertain parameters and immeasurable states. A MPC TOOLBOX in MATLAB software is used to obtain desired crystal size distribution (CSD)

Sustained release of lysozyme encapsulated in zein micro- and nanocapsules

A hydrophobic biopolymer, corn zein, was studied as a carrier for manufacturing particulate delivery systems of antimicrobials with sustained release. Three techniques, i.e., solvent attrition, supercritical anti-solvent and spray drying, were investigated to produce lysozyme-loaded zein micro- or nanocapsules. The work was focused on particle synthesis and in vitro release kinetics as affected by formulations and processes. The size (100-200 nm) and morphology (separated or connected) of the zein nanoparticles produced using solvent attrition were significantly affected by shear force, ethanol and zein concentrations in stock solutions during synthesis. Zein nanoparticles showed gradual release of lysozyme at pH 7 and 8 but no sustained release at lower pHs. Further, the impact of adding 1% zein nanoparticles in model carboxymethylcellulose solutions (adjusted to pH 3 to 9) was studied for viscosities that increased with pH. Microcapsules produced from supercritical anti-solvent showed a continuous matrix with internal voids. Sustained release of lysozyme at pH 2 to 8 was observed over 36 days at room temperature, with slower release at higher pH. At pH 4, release kinetics was further slowed by addition of sodium chloride. Spray drying was studied as one commercially feasible process. To further reduce the material cost, partial purification of lysozyme from hen egg white was studied using binary aqueous alcohol. Extraction with 50% ethanol at pH 3.5 for 6 h enabled high lysozyme activity and relatively high purity. Lysozyme precipitated after increasing the ethanol concentration from 50% to 90% in the extract. The precipitates were resolubilized by dilution to 50% ethanol. Slurries after increasing ethanol concentration from 50% to 60%-90%, with or without additives of Tween 40 or thymol, were spray dried. Capsules without additives were porous and did not show sustained release of lysozyme. The addition of Tween 40 changed the capsule microstructure to packed nanoparticles but did not achieve sustained release of lysozyme. Thymol facilitated the formation of a continuous capsule matrix and allowed sustained release of lysozyme at near neutral pH. Findings from this work demonstrated the possibility of using zein as a carrier biopolymer to deliver antimicrobials in food matrices for sustained release

Development of Fibre Reinforced Geopolymer Concrete (FRGC) cured under ambient temperature for strengthening and repair of existing structures

Most of the previous research on plain and fibre reinforced geopolymer concrete (FRGC) has concerned on the properties of geopolymer mixtures hardened under heat curing conditions, which is a severe limitation for on-site, cast-in-place applications. This study focuses on the material and structural properties of novel fibre reinforced geopolymer concretes cured under ambient temperature. The overall aim of the study was to develop and test a more environmentally sustainable concrete material with improved structural characteristics, which utilises waste rather than primary mineral products, suitable for cast-in-place applications and for the structural strengthening of existing buildings. In the first part of this thesis, the material behaviour of FRGC cured under ambient temperature was examined. Initially, the work identified the role of various parameters which may affect material compressive strength, in order to enhance overall performance. In addition, the mechanical and microstructural properties of geopolymer mortar with different slag contents and variant silica fume types (densified, undensified and slurry) were assessed. Following this, the effect of slag content and silica fume particle size on the properties of steel fibre reinforced geopolymer composites (SFRGC) was examined. The optimum FRGC mixtures were further investigated in term of its durability characteristics and mechanical properties, in order to provide strain hardening characteristics. In the examined mixes, different fibre types, aspect ratios, and volume fractions, and its comparison with Portland cement based conventional concrete, have been assessed and appropriate mixtures have been identified with multiple fine cracks and strain hardening in tension. In the final part of the thesis, the structural behaviour of FRGC is examined at larger scale application. PVA and steel fibre reinforced geopolymer concrete mixtures were used as strengthening and repair materials for the protection of steel bars in a new material layer, and for subsequent improvement of the flexural strength of existing beams. Large scale beams strengthened with additional FRGC layers reinforced with steel bars have been examined. Also, an additional investigation was conducted in beams where part of the concrete cover at various depths was replaced by FRGC. In all the examined cases respective beams with conventional concrete were examined in order to evaluate the efficiency of the proposed technique. Accelerated corrosion tests were performed using the induced current technique by applying a nominal 300 mA constant anodic current. The results of this investigation showed significant improvements in the structural performance of the examined beams following strengthening or repair with FRGC. The outcomes of the experimental work indicate that FRGC considerably enhanced both the flexural strength capacity and the durability of strengthened and repaired reinforced concrete elements