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

3.3.4. Results and discussion
The results of the normal spline fit are given in
Annex 3.3.2, while the results of the spline fit with
symmetric reflection are given in Annex 3.3.3. Both
are compared with the evaluated experimental data
(Figs 3.3.2–3.3.5).
Total yields under the light and heavy mass
peaks, as well as v – , were calculated in order to check
the correctness of the spline fit curve. The
borderline between the light and heavy mass peaks
was taken at mass 124, which was calculated from
the mass number of 252 Cf and v – = 3.7661
(Table 3.3.2). As shown by the normal spline fit, the
integral yield under the heavy mass peak is in good
agreement with 100%, while the total yield under
the light mass peak is in similar agreement within an
uncertainty of 1.3%, and v – is in agreement with the
internationally recommended value of 3.7661 within
an uncertainty of 2.93%. Similarly, for the
symmetric fit the integral yield under the light and
heavy mass peak is in agreement with 100% within
an uncertainty of 1.0%, and v – is in agreement with
the internationally recommended value of 3.7661
within an uncertainty of 1.86%.
A comparison between the results of fits with
and without symmetric reflection is shown in
Fig. 3.3.6. These data are in very good agreement,
but there are some differences in the peak regions.
The light mass peak without symmetric reflection is
narrower than the equivalent peak with symmetric
reflection, and the situation is the reverse for the
heavy mass peak. Also, the right hand side of the
light peak is narrower for the normal fit than for the
symmetric fit, but the left hand side of the heavy
mass peak is the opposite (see Figs 3.3.1 and 3.3.8).
c 2 is 1.551 for the normal fit and 1.795 for symmetric
fit, indicating that the mass distribution is not
completely symmetric around the reflection point.
The fits to the results imply that there is a
systematic trend towards the light fragment peak
being higher and narrower and the area under the
peak being slightly smaller. Individual experimental
data by different authors also exhibit the same
92
FIG. 3.3.6. Comparison of regular and symmetric spline fit:
mass distribution.
FIG. 3.3.7. Comparison of regular and symmetric spline fit:
light mass peak.
trend. Table 3.3.3 shows some of the results from
different authors, who measured a wide range of
fission products so that integrals of the yields under
the peaks can be calculated more reliably. These
integral data are given in the papers by Li Ze et al.
and Chen et al., and were calculated for Schmitt et
al. and Fraser et al. by using their original data
without any adjustments. The yields under the light
mass peak are smaller than those under the heavy
mass peak in all four cases. Comparing the light and
heavy mass peak yields of Li Ze et al. and Schmitt et
al. (Figs 3.3.9 and 3.3.10), the light peak can be seen
to be narrower than the heavy peak — this
TABLE 3.3.2. REDUCED c 2 , TOTAL YIELD AND v – FROM FITTED DATA
Fit mode Reduced c 2
Total yield
Light peak Heavy peak Total
Normal 1.551 98.76 99.77 198.52 3.8764
Symmetric 1.795 98.98 98.96 197.95 3.6962
v –