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The use of a scalloped cross-sectionsl coolant channel has been suggested as a possible solution of the fuel-element bowing problem inherent in the septafoil type of geometry. Using simplified assumptions, a method has been developed for calculating the red spacing and scallop size necessary to produce equal average fuel-element surface temperatures in the central and peripheral regions of the coolant flow channel at the mid-section of each fuel-red cluster under a given set of reactor flow conditions. Since the extent of rod-bowing is related to the surface temperature distribution, this requirement should minimize fuel-element deflection. ( auth) l6629 In heavy-water-cooled and -moderated power reactors such as NPD-2 and CANDU the coolant will be insulated from the moderator by a gas layer external to the pressure tubes. Therefore, these tubes must be designed to operate at the maximum coolant temperature. However, by placing the insulation inside the pressure tubes they can be kept cold; a thiner wall or a higher reactor operating temperature can be used. and a wider range of pressure tube materials be considered. Two kinds of internal insulstion are considered: the cooled pressure tube in which stagnant heavy water is the insulation, and the cooled stress tube inmore » which magnesium oxide is the insulation Both are compared with externally insulated pressure tubes by calculating the cost of power for a series of reactors in which only the arrangement of the pressure tube and insulation is varied. For Zircaloy pressure tubes the use of internal insulation is estimated to reduce the cost of power by about 0.2 mill per kwh from that obtained with external insulation. This is a sufficiently attractive potential saving to warrant further development work on the cooled- Zircaloy-tube concept Neither aluminum nor magesium are attractive materials cooled pressure tubes. The two types of interna insulation result in the same cost of power and they will have to be compared on the basis of their technical performance. Studies of the cooled stress tube are not as pet sufficiently advanced for this to be done. (auth) l6630 A preliminary stud of the heat variations in a pressurized water reactor is made with emphasis on the ALPHA ship reactor project. On the basis of a litera ture search and heat calculations for the Savannah and Shippingport reactors, the boiling heat transfer was calculated without consideration of correction factors. (J.S.R.)« less |
