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

values (points) and the derived function (line), both
adjusted for the small Z F dependence to allow
comparison of parameter values for a number of
fission reactions with the derived function.
The narrowness of the inner peak curves that
results from the sharp decrease in yields below A H @
130 and above the light complementary A L = PA –
130 – NT, as well as the large kinetic energies
[4.2.28] and small prompt neutron emission near
A = 130 [4.2.29], may all arise from the proximities
of the Z and N of the nascent heavy fragments to
the Z = 50 and N = 82 spherical shells.
4.2.2.7. Central peak curve
FIG. 4.2.16. A' 4 = A 4 – f(Z f ) function.
The maximum for the central peak is at the
midpoint (D 3 = 0.0, AL 3 = (PA – NT)/2), and the
width parameter for the central peak (s 3 = 8.6 ± 1.0)
is the average of ten values from the fission of
thorium isotopes. Principal peak separations were
larger for these fissions than for the other fission
reactions investigated, giving optimal information
about the properties of the central peak (e.g. see
Figs 4.2.1(a) and (b) and compare with Figs 4.2.2(a)
and (b) through to 4.2.10(a) and (b)). The value of 8.6
better approximates the nearly flat valleys observed
for a number of experimental mass yield data than
does the smaller value of 6.0 used previously [4.2.4].
For high energy fission reactions, s 3 was taken to be
8.6 or s 1, whichever was the larger.
The curve intensity (Y 3 ) increases by several
orders of magnitude with increasing PE (~0.015%
from model calculations for spontaneous fission
[4.2.4] and ~90% for high energy fission). This
significant change required two functions to be
applied in different regions of PE (Eqs (4.2.7) and
(4.2.8), Table 4.2.1, and Fig. 4.2.13). The transition
between functions is quite smooth (two exponential
functions with different slopes were used in Ref.
[4.2.4]).
4.2.2.8. Wing curves
Least squares calculations for nuclei with Z F ≥
94 showed that the wing curve parameters Y 6,7 and
D 7 were essentially constant for low PE (