Xenon critical constants

The energy distribution functions in liquid argon and liquid xenon are shown in Figure 16. These results should serve only as illustrative examples. The precision and accuracy of the calculations depend critically on the input data for Aq and A (see Gushchin et al, 1982). Aq can be taken as constant, while Aj is extracted from mobility measurements. The mobility data available in the literature show considerable scatter (see Chapter 3). A direct estimation of the electron mean energy comes from the measurement of the transversal diffusion coefficient. The ratio of diffusion coefficient and mobility is a measure of the mean energy. 

The control rod patterns are determined for each of the 15 bumup steps of the equilibrium cycle (cycle bumup exposure of 0-14.8 GWd/t). Figure 2.54 [9] shows the control rod patterns for the equilibrium core (1/4 core symmetry). Each box represents a fuel assembly and the value in the box represents the control rod withdrawn rate out of 40. A blank box represents a fuel assembly with control rods completely withdrawn. While the control rod patterns are adjusted at every 1.1 GW/t throughout most of the cycle, the fine adjustment of the control rod pattern at a cycle bumup of 0.22 GWd/t is necessary to compensate for a rapid drop of BOC excess reactivity. The excess reactivity drop is relatively fast with respect to the bumup at BOC because of the initial build up of xenon gas and other fission products. The concentration of xenon reaches eqmlibrium shortly after operation commences and from there, the rate of the excess reactivity drop becomes lower and almost constant. The control rod patterns are determined by considering control of the core power distributions while keeping the core critical. The radial core... 

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