11-6Nuclear PowerChap. 118. Although the steam cycle is simpler in a BWR, explain why the capital costsof BWR and PWR plants are very competitive.Solution:The simplicity of a single steam/water cycle in a BWR compared to the doubleprimary/secondary cycles in a PWR is offset by the increased complexity of theBWR components. Although a BWR does not require steam generators and apressurizer, the reactor pressure vessel is much more complex. A BWR vesselmust include steam dryers in the top and penetrations for control rods andinstrumentation in the bottom of the vessel. Two-phase flow through the corerequires a very detailed thermal-hydraulic design. For example, fuel assembliesare shrouded (Fig. 11.21)to prevent cross flows. F\1rthermore, differing sizedorifices are required in the entries to coolant channelsto adjust flow rates toassurethat steam quality is uniform across the core. More important, A BWRcore has a power density (W /liter) about half that of PWRs, and, for the
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