Design improvements

The flow scheme of the out-in refueling core is described by Fig. 2.66 [9]. Among the 121 fuel assemblies, 89 inner fuel assemblies are cooled by upward flow of the coolant, while the 32 outer fuel assemblies are cooled by coolant downward flow. The core pressure is 25 MPa and the inlet coolant temperature is 280°C. Most of the inlet coolant (76.7%) is guided to the top dome and distributed to the water rods of the inner fuel assemblies (30.0% of the inlet coolant), water rods of the outer fuel assemblies (10.8% of the inlet coolant), and the fuel channels 

The flow separation plates were introduced in the first trial design mainly to increase the coolant outlet temperature from the outer region of the core. However, such separations are not necessary when the outer core downward flow cooling scheme is adopted. 

When the outer core downward flow cooling is adopted for the out-in refueling core, the maximum power fuel rod may not belong to the maximum power fuel assembly. As can be seen from the radial core power distributions in Fig. 2.69 [9], 

The MCST is evaluated with three-dimensional core calculations using the homogenized fuel assembly model and the single channel thermal-hydraulic analysis model as before. The peak value of the MCST is about 650°C, which is the same as that of the first trial core. As noted above, the removal of the flow separation plates for the first trial core decreases the core outlet temperature by about 40-50 C. Taking this reduction into account, the outer core downward flow cooling can effectively raise the average outlet temperature by about 70-80°C, which may have a great impact on the plant economy. 

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Robust design improves product quality by reducing the effects of variability (Phadke, 1989). 

Mayeux, T., Paul, Feltman Jr., and Paul, F., Design Improvements Enhance Dry Gas Seal s Ability to Handle Reverse Pressurization, Proceedings of the 25th Turbomachinery Symposium, Texas A M University, p. 149, 1996. 

National Nuclear Corporation, New advanced gas-eooled reactors incorporate design improvements, Nud. Engr. Int., March 1981,27 36. 

One of the most spectacular modern developments in materials has been the design, improvement and exploitation of fine glass fibres for purposes of large-scale communication. Messages, above all telephone conversations, but also TV signals... 

Transportation risk can be reduced by applying inherently safer design principles to transportation containers. Some examples of design improvements follow. 

Analyses are types of calculations but may be comparative studies, predictions, and estimations. Examples are stress analysis, reliability analysis, hazard analysis. Analyses are often performed to detect whether the design has any inherent modes of failure and to predict the probability of occurrence. The analyses assist in design improvement and the prevention of failure, hazard, deterioration, and other adverse conditions. Analyses may need to be conducted as the end-use conditions may not be reproducible in the factory. Assumptions may need to be made about the interfaces, the environment, the actions of users, etc. and analysis of such conditions assists in determining characteristics as well as verifying the inherent characteristics. (See also in Part 2 Chapter 14 under Detecting design weaknesses.)... 

These can be achieved through reduced downtime, consolidating safety-related activities, improving operations information, facilitating process design improvements, minimizing exposure to liability, and improving customer satisfaction. 

Tires, like everything that rolls, encounter resistance. The resistance encountered by the tire rolling across a surface is a major factor in determining the amount of energy needed to move vehicles. Since Dunlop s original efforts, a considerable number of tire design improvements have been made that have tended to cause a decrease in tire power consumption. For example separate plies of cotton cord were intro-... 

Advanced two- and three-dimensional computer analysis methods are used today in the analyses of all critical components to verify aerodynamic, heat transfer, and mechanical performance. Additionally, the reduction of leakage paths in the compressor, as well as in the gas turbine expander, results in further plant efficiency improvements. At the compressor inlet, an advanced inlet flow design improves efficiency by reducing pressure loss. Rotor air cooler heat utilization and adt anccd blade and vane cooling arc also used. 

Some reactants in atmospheric-pressure reactors must be highly diluted with inert gases to prevent vapor-phase precipitation, while generally no dilution is necessary at low pressure. However, atmospheric pressure reactors are simpler and cheaper. They can operate faster, on a continuous basis and, with recent design improvements, the quality of the deposits has been upgraded considerably and satisfactory deposits of many materials, such as oxides, are obtained. 

Although impressive progress has been made in unraveling the mechanism of ORR catalysis by cofacial porphyrins, much remains to be learned before we can understand how this mechanism relates to those in heme enzymes and simple metalloporphyrins and use our mechanistic knowledge to rationally design improved metalloporphyrin catalysts for the ORR. 

It is important to note that age does not necessarily increase the likelihood of equipment failure. Properly designed, inspected, and maintained equipment in fact may have a low likelihood of failure. Years of operating experience may provide valuable information such as the locations of high-corrosion rates areas in piping and may also bring about repeated design improvements. 

The Model 303A static mercury drop electrode (SMDE) has received continuous design improvements (cf., Fig. 3.28 and associated explanation), e.g., the larger drop size afforded by the 303A design has yielded a further increase in sensitivity and the flip of a switch converts it into an extremely stable HMDE for stripping and/or square-wave voltammetry. ... 

Tong, L. S., 1988, Principles of Design Improvement for Light Water Reactors, Hemisphere, New York. 

Parker, M.A. and McDaniel, B.U. "Fracturing Treatment Design Improved by Conductivity Measurements Under In-Situ Conditions," SPE paper 16901, 1987 SPE Annual Technical Conference and Exhibition, Dallas, September 27 30. 

Some of the important issues that should be considered when designing, improving or operating any such pipe branching applications are described in the following sections. 

This accident could have been prevented by a good inspection and maintenance program. Potential design improvements include vibration detectors, gas analyzers, block valves, and deluge systems. 

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