Fission Product Yield Data for the Transmutation of Minor Actinide ...

FIG. 4.6.1. Fission product mass yields from 190 MeV proton induced fission of nat W, 197 Au, nat Pb and 208 Pb. The lines indicate
the fitted Gaussian mass distributions; the filled circles denote the independent and cumulative yields used in the fit; triangles
correspond to the experimental mass yields deduced from these measured independent and cumulative yields.
slope of the ECD lines will probably attain a value
closer to the fitted slope. It is impossible to draw a
conclusion as to which model gives the best
predictions on the most probable charges of the
fission fragments.
4.6.3.3. Fission in thorium
4.6.3.3.1. Symmetric and asymmetric fission
contributions
Fitting Eq. (4.6.1) to the measured yields of
232 Th produces the mass yields and the mass
214
distribution, as shown in Fig. 4.6.4. The result is
certainly not a Gaussian, as is the case for the subactinide
targets. Furthermore, the fission crosssection
obtained in this manner is 630 ± 60 mb,
which is much lower than the value by Eismont et
al. of 1236 mb from systematics [4.6.25]. The values
of the fit parameters can be found in Table 4.6.3.
Looking carefully at the 232 Th mass yields, one
notices a dip around fragment mass 125. Therefore,
the suggestion is that the fragment mass distribution
for 232 Th cannot be properly described by a single
Gaussian, but rather is a superposition of a wide
flattened distribution and a narrower Gaussian.