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The core region of a nuclear rector is an extremely compact area with a capability of providing a very high heat output. Regardless of the type of coolant used, the heat transfer characteristics of this region must be adequately designed to prevent any undesirable "hot-spots" from developing. The Sandia Engineering Reactor has one of the most compact cores of any in currently operating nuclear reactors. For this reason it is necessary to investigate fully the heat transfer characteristics of the core. The rate of heat transfer from the fuel elements to the coolant is directly dependent upon the temperature difference between the fuel elements and the coolant, the area available for the heat transfer, and the rate of coolant flow past the fuel elements. Because of these factors an investigation of the flow of coolant was deemed necessary.

The purpose of this study undertaken was threefold, (1) to design and construct an experimental vacuum apparatus to produce a metal impregnated or coated material; (2) to study some of the variables which affect the process; then (3) to examine the physical characteristics of the resultant materials. Described herein is the development and operation of a vacuum system capable of producing conditions to permit the evaporation of metals to impregnate and coat various materials. The fundamental principle involved in this process is that a rarified atmosphere reduces the temperature required for metal evaporation and protects the metal vapor from reacting with the contaminants as it is transferred to and deposited on a receiving material.

To insure the proper application of newly developed materials, it is necessary to evaluate their physical and chemical properties. In the case of plastic laminates for use as heat barrier material, thermal diffusivity is an important property. Thermal diffusivity is the parameter which governs the rate of temperature change through a material. Its value depends upon the chemical composition and the physical structure of the material and its temperature.

Nitroguanidine (NQ) is a high explosive which is commercially available in low bulk density form (0.20 to 0.30 gms/cm3). This low bulk density limits its usefulness as an explosive. High bulk density NQ can be produced from a NQ-N, N-dime-thylformamide-Versamid 125 system when crystallized in a mixed suspension mixed product removal crystallizer. Bulk densities ranged from 0.92 to 1.05 gms/cm3 for the operating conditions used. The effect of agitator speed, growth rate, and solids concentration on nucleation rates was determined using a multiple linear regression technique. The resulting equation is: B0 = 0.19 (RPM) 1.54 (G) 1.68 (MT) 0.09. The result is consistent with postulated secondary nucleation mechanisms.

The object of this was to find the factors controlling the rate of wetting of carbon filaments by organic liquids. To carry out this study, the factors affecting the wetting of surfaces, such as the surface tension of liquids, and the contact angle formed at the liquid-vapor-solid boundary of a three phase system were discussed. At the same time, the anomalies with respect to contact angle, such as that relating to advancing and receding contact angles to dynamic angles was considered. As complimentary information, the methods used to obtain carbon and graphite filaments from cellulose and molten pyrolysis products were studied. Also studied were characteristic properties of both types of filaments. The experimental study was carried out by using Union Carbide type VYB 70-1/2 carbon filaments and twenty different organic liquids. Experimental technique used was wicking and the increasing weight of the filaments with time was recorded. The experimental data obtained in this way are included in this thesis, as well as the plots made to reach the final conclusions. The final conclusion reached was that the rate of wicking of the carbon filaments in controlled by the same factors controlling the rate of wicking of textile fibers. The principle factors are: surface tension, viscosity and density of the wetting agents, and the contact angle. It was found that the same equations hold for both textile fiber and carbon filament systems.

Abstract A complete carbon black pilot plant was employed in this study. Carbon laden gas was produced in a fur­nace and introduced into the outer pipe of a heat ex­changer. Air, at the same time, was introduced into the inner pipe of the heat exchanger cocurrently with the carbon laden gas. Thus, heat, with temperature dif­ference as driving force, would transfer from the car­bon laden gas to the air stream. The temperatures along the two streams were measured by iron-constantan ther­mal couples and recorded by a multi-reading temperature recorder. Air supply and fuel (C3H8) supply were intro­duced into the furnace with such rates that about 3oi of combustion would be achieved. The flue gas from the heat exchanger was piped to a collecting system where most of the carbon particles were removed and the gas was released to atmosphere. With the temperature data and the fuel and air flow rate, plus the thermal property data for the gases involved (obtained from some publications), the dimensionless groups such as Reynolds number, Nusselt number and Prandtl number were calculated and correlated to an equation of the Dittus-Boelter form. Due to heat lost to the ambient and carbon particles deposited on the pipe wall, the heat transfer rate for this system was approximately equal to 1/14 of that of a pure gas system without any significant deposit and heat loss. Because of the characteristics of this particular experiment, the result may only be recommended to apply on systems that close to this one. In other words, the generality of the obtained equation is re­stricted by the characteristics of the system employed.

Cold traps have been used extensively for controlling oxygen concentration in sodium systems. Cold traps utilize the positive temperature dependence of the solubility of sodium monoxide in sodium and the resultant precipitation of sodium monoxide at low sodium temperatures. Sodium monoxide precipitation is here assumed to be heterogeneous because of the strong effect of surface area on the precipitation rate shown in previous packless cold trap experiments. Growth of crystals from a super-saturated solution is said to proceed according to the equation where dm/dt is the rate of mass accumulation on the crystal, k is an over-all mass transfer coefficient including a diffusion step and a precipitation step, A is the crystal surface area, C is the bulk solute concentration and Ce is the equilibrium concentration at the temperature of the crystal. A packless cold trap of simple geometry and operating with a temperature gradient was used in this study. In the presence of the temperature gradient, the effective precipitation surface area was a function of the oxygen concentration in the sodium entering the cold trap. An equation describing the change in oxygen concentration with time was derived by performing a mass balance around the system using equation 1 and by accounting for the change in effective surface area with changing oxygen concentration. Eleven cold trapping runs were performed in which concentration was measured as a function of time. Tests were performed at various flow rates, initial oxygen concentrations and final oxygen concentrations. In general, the theoretical model fit the data quite well. Values of the mass transfer coefficients were calculated and were found to be a function of both temperature and flow rate. The dependence on sodium flow rate was proportional to Reynolds number to the 0.6 power. Variation of the mass transfer coefficient with flow rate implied that the precipitation process was diffusion controlled. An Arrhen