Despite the inability of these equations to represent accurately the concentration of higher plutonium isotopes, the reactivity-limited bumup attainable from fuel initially containing 3.2
w/o 235 U can be predicted quite satisfactorily from the results of this table. Reactivity p, calculated from these concentrations by Eq. (3.35), is listed in the last row of Table 3.15 and is plotted against burnup В at the circled points in Fig. 3.30. The points are represented quite accurately by the straight line

p = 0.17 — 8.16 X 10‘6Д (3.82)

The reactivity equals zero at a burnup of 20,833 MWd/MT. This is in excellent agreement with the reactivity-limited burnup of 21,085 MWd/MT for batch irradiation of 3.2 w/o fuel in this reactor obtained by Watt [W2] using the computer codes CELL [B2] and CORE [К1].