accuracy for sodium void reactivity of the core with a sodium plenum might be
poor. Thus, we should consider change of the neutron spectrum in the heterogeneous MA loaded core. Figure 17.5 shows the neutron spectra for MOX driver fuel
without MA and 10 % MA-mixed fuels in transmutation target with and without
Zr-Hx. The spectrum of 10 % MA-mixed fuel in transmutation target without Zr-Hx
is slightly softer than that of the MOX driver fuel without MA, because the 10 %
MA-mixed fuel in the transmutation target has no fissile plutonium but the MOX
driver fuel includes
239 Pu and
241
Pu. The neutron spectrum of the moderator
mixture target fuel is clearly softer than other fuels.
Fig. 17.3 Vertical view of
axially heterogeneous core
with sodium plenum
Fig. 17.4 Axial distribution of coolant density and density coefficient
17 Method Development for Calculating Minor Actinide Transmutation in a Fast. . .
183
poor. Thus, we should consider change of the neutron spectrum in the heterogeneous MA loaded core. Figure 17.5 shows the neutron spectra for MOX driver fuel
without MA and 10 % MA-mixed fuels in transmutation target with and without
Zr-Hx. The spectrum of 10 % MA-mixed fuel in transmutation target without Zr-Hx
is slightly softer than that of the MOX driver fuel without MA, because the 10 %
MA-mixed fuel in the transmutation target has no fissile plutonium but the MOX
driver fuel includes
239 Pu and
241
Pu. The neutron spectrum of the moderator
mixture target fuel is clearly softer than other fuels.
Fig. 17.3 Vertical view of
axially heterogeneous core
with sodium plenum
Fig. 17.4 Axial distribution of coolant density and density coefficient
17 Method Development for Calculating Minor Actinide Transmutation in a Fast. . .
183