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

4.3.3. Examination of parameters
Several measured mass distributions are
available. The measured mass distributions were
decomposed into five Gaussian functions by least
squares fits. A x and s x in Eq. (4.3.2) were obtained
from the decomposed Gaussian functions. R and F
were calculated using the following relationships:
fragment yield given by two asymmetric components
R =
fragment yield given by the symmetric component
150
Y + Y + Y + Y
h h l l
=
Y
1 2 1 2
s
, (4.3.5)
fragment yield given by component 2
F =
fragment yield given by component 1
Y + Y h2 l2
=
Y + Y
h1 l1
(4.3.6)
where Y h1 , Y h2 , Y l1 and Y l2 are the yields of the
asymmetric components, and Y s is the yield of the
symmetric component. The resulting parameters
were examined by plotting these data against
various variables such as the mass of fissioning
nuclides, energy of incident particles, etc. Thus the
dependence of the parameters on the various
variables was determined.
Examples of such dependences are given in
Figs 4.3.1 and 4.3.2. Figure 4.3.1 shows the
dependence of the R parameter on the incident
particle energy. The solid circles represent yields
from measured mass distributions of 238 U for
various incident neutron energies [4.3.3]. The
behaviour of the measured data in Fig. 4.3.1
suggests an energy dependence proportional to
1/(E C 1 + C 2 ). The values of C 1 and C 2 were
determined by least squares fit. Figure 4.3.2 shows
the shell factor dependence of the R parameter,
which seems to exhibit a sinusoidal dependence on
the shell factor. The shell factor mentioned here is
that given by Meyers and Swiatecki [4.3.4].
Other examples of the examination are
illustrated in Figs 4.3.3 and 4.3.4. Figure 4.3.3 shows
the energy dependence of the F parameter. Since a
clear energy dependence is not evident, we assume
no energy dependence for the F parameter.
However, the shell factor dependence is clearly seen
in Fig. 4.3.4. The F parameter is assumed to be
linearly dependent on the shell factor.
FIG. 4.3.1. Energy dependence of the R parameter.
Derived from measured data
Fitted result
FIG. 4.3.2. Shell factor dependence of the R parameter.
FIG. 4.3.3. Energy dependence of the F parameter.
Similar examinations were performed for
other parameters. The resulting parameters for the
present systematics are described below.