SYSTEM DYNAMICS MODEL DEVELOPMENT BY ANALYZING CAUSES OF FUKUSHIMA DAIICHI NPP UNIT-1 ACCIDENT

— Fukushima Daiichi NPP accident occurred on March 11, 2011. A system dynamics model is developed by analyzing the chronological progression and causes of the Fukushima Daiichi NPP unit-1 accident applying causeeffect relationship and qualitative causal loop and feedback loop. The accident progression demonstrates that the safety system of the NPP could not function properly, resulting in the loss of core cooling and confinement of radioactive materials functions, and a severe accident with hydrogen explosion occurred. The system dynamics model shows that earthquake, tsunami induced flooding, design failure of Tsunami height, loss of all AC power, loss of DC power, loss of ultimate heat sink, failure of HPCI system, failure of IC system, design complexity of isolation valves of IC and lack of training on IC operation, delayed water injection to reactor, delayed operation of containment venting, lacking of compressed air, high reactor pressure, and harsh radiological condition are the causes of this severe accident. High reactor pressure and harsh radiological condition were produced during the accident, which positively boost accident progression by demonstrating the effect of system dynamics. The conservative design to protect power sources from natural events and the loss of all power for an extended period must be considered during future design of NPP.

SYSTEM DYNAMICS MODEL DEVELOPMENT BY ANALYZING CAUSES OF FUKUSHIMA DAIICHI NPP UNIT-1 ACCIDENT

Fukushima Daiichi NPP accident occurred on March 11, 2011. A system dynamics model is developed by analyzing the chronological progression and causes of the Fukushima Daiichi NPP unit-1 accident applying causeeffect relationship and qualitative causal loop and feedback loop. The accident progression demonstrates that the safety system of the NPP could not function properly, resulting in the loss of core cooling and confinement of radioactive materials functions, and a severe accident with hydrogen explosion occurred. The system dynamics model shows that earthquake, tsunami induced flooding, design failure of Tsunami height, loss of all AC power, loss of DC power, loss of ultimate heat sink, failure of HPCI system, failure of IC system, design complexity of isolation valves of IC and lack of training on IC operation, delayed water injection to reactor, delayed operation of containment venting, lacking of compressed air, high reactor pressure, and harsh radiological condition are the causes of this severe accident. High reactor pressure and harsh radiological condition were produced during the accident, which positively boost accident progression by demonstrating the effect of system dynamics. The conservative design to protect power sources from natural events and the loss of all power for an extended period must be considered during future design of NPP.

Synthesis and Characterization of Pb@GaS Core–Shell Fullerene-Like Nanoparticles and Nanotubes

New types of core–shell nanoparticles are reported: Pb@GaS fullerene-like and nanotubular structures, achieved via the continuously high reactor temperatures and ultra-hot strong-gradient annealing environments created by highly concentrated sunlight. Structural and chemical characterizations suggest a formation mechanism where vaporized Pb condenses into nanoparticles that are stabilized as they become covered by molten GaS, the ensuing crystallization of which creates the outer layers. Hollow-core GaS fullerene-like nanoparticles and nanotubes were also observed among the products, demonstrating that a single solar procedure can generate a variety of core–shell and hollow nanostructures. The proposed formation mechanisms can account for their relative abundance and the characterization data.

Design and Control of Alkali-Catalyzed Transesterification Reactors

Controllability analysis during the design stage is needed to ensure that the plant can be operated properly. This research focuses on design and control of transesterification reactor. Effects of important design parameters including residence time, methanol/oil molar ratio, and reactor temperature to design conversion and controllability of the reactor are studied. Controllability is analyzed using linear system theory based on poles, zeros, and gains. The result reveals that for a given design conversion, the operation with high reactor temperature and low methanol/oil molar ratio is preferred.

Synthesis of tungsten oxide comblike nanostructures

Tungsten oxide comblike nanostructures were synthesized using a two-step thermal evaporation method. The first step involving high reactor pressure and temperature was to synthesize the cores of the comb structures, upon which the teeth of the comb were grown in the second step using low operation pressures and temperatures. The teeth of the comb structure are well aligned and vertical to the side surfaces of the cores. The effects of growth parameters were examined, and the growth mechanism was investigated.

Amorphous silicon nitride fibers grown from the vapor phase

Using high reactor pressures (>1 bar) and a unique rate control mechanism, three fibers were recently obtained by laser assisted chemical vapor deposition (LCVD) having elemental (i.e., boron, carbon, and silicon) compositions, small diameters (>9 μm), and surprisingly high growth rates (0.3–1.1 mm/s). By reacting silane and ammonia at high pressures (>1 bar) near the focus of a Nd-YAG laser beam, we have now obtained the first LCVD fibers with binary (i.e., silicon-nitrogen and silicon nitride) compositions having small diameters and high growth rates (0.34–0.74 mm/s). These fibers were amorphous.

Etiologic Studies on Late-Term Swine Abortions

One hundred thirty-eight swine abortions were studied in detail in an effort to identify an etiologic agent. A viral agent was implicated in 7 cases. Bacteria were isolated in less than half of the examined cases; however, in 61% of the cases, motile, filamentous organisms were observed in tissues and fluids. Although swine sera from farms experiencing reproductive problems had a high reactor rate to Leptospira bratislava antigen, electron microscopy of the observed organism revealed a wall-free prokaryote morphologically typical of the class Mollicutes.