FIG . 24-6 . Fuel concentration in core vs . PB/Pl for two-fluid LMFR fully blan-
keted sphere . All criticality calculations were performed using the specifications out1ined in Article 24-2 .2 . Two-group diffusion theory was employed, and a t - o-group, multiregion code was used for solving the diffusion equations . A- previously mentioned a 37-group spectral code was used to generate the t`vo-group coefficients . The critical concentration of fuel in the core and i , lauket . breeding ratio, and neutron losses were determined for several powor -plits for each relative poison level in the core . The blanket power frarti,,ii values of 10, 33 .3, and 50% were used as reference values for compari-i,i, and the important nuclear parameters were determined from a set of par, metric curves for these precise values . (Cases actually calculated corn ponded very closely to the desired blanket power in most calculation . TTThc iiua'lear parameters corresponding to these power splits are summarizu â&#x20AC;˘d in Table 24-2 . Figures 24-5 and 24-6 show the variation of X> :, N 1 , in both the core and blanket as the blanket power fraction chan<tc- . This atom ratio of U233 to bismuth in the blanket ranges from - h to 2420 X 10 - c for 255 x 10 PB/Pt = 0 .10 to 0 .50 . In the core the J - :: X i i, ratio decreases approximately 20% over the same range . The