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

activities were recorded with a proportional counter
for b emissions and with a NaI scintillator for g rays.
The efficiency of the g ray detector was determined
experimentally. Either the predetermined g ray
efficiency curve was used or the efficiency of the
g ray and b particle detectors was determined
directly via the measured fission product. The total
uncertainties of the data are 3–15% and include
contributions from detector calibration and chemical
yield, fission rate and peak area determinations.
The data were taken from Table 1 of the paper
(no corresponding EXFOR entry exists) and agree
reasonably well with the data of Li Ze et al. [3.3.8],
although there are fewer values in the valley range.
Chain yields are too large for A = 113, 134 and 135, as
deduced from 113g Ag, 134 Te and 135 I, respectively. These
nuclides are far from the stable nuclides of the
respective chains (i.e. by 2–3 charges). The adjustment
factors from the literature are relatively large (when
calculated using ENDF/B-VI data they are even
larger), the resulting yields are unreliable, and their
uncertainties are increased by 10% for mass chains
113 and 135, and by 13% for mass chain 134. Also, the
uncertainty for 99 Mo was increased from 3.5% to 5%.
3.3.2.8. Fraser et al. [3.3.10]
Fragment mass distributions of pre- and postneutron
emission were measured by the double
time of flight method, with a source intensity of 0.6–
3 × 10 5 fissions/min. The flight paths were 144.3 and
146.2 cm, time resolution was 1.35 ns, and data were
adjusted for mass resolution.
The mass yields are given for each mass
number in the range 80–168, which represents a
reasonably complete coverage of the mass distribution,
but the measurement statistics are poor due
to the weak source and the long flight distance.
Furthermore, there may have been some problems
with the energy and mass calibration because the
light mass peak is narrower and the heavy mass
peak is systematically shifted to the right (Fig. 3.3.1)
when compared with other studies (e.g. Li Ze et al.,
and Schmitt et al.). The data were eventually
discarded in the evaluation.
3.3.2.9. Adopted data
All adopted and adjusted experimental data
are given in Annex 3.3.1 and shown in Figs 3.3.2–
3.3.5. Seven sets of data altogether are in agreement
within the assigned uncertainties, except for a few
specific data points.
90
FIG. 3.3.1. Comparison of data of Li Ze, Fraser and
Schmitt.
FIG. 3.3.2. Mass distribution from 252 Cf spontaneous
fission.
FIG. 3.3.3. Mass distribution from 252 Cf spontaneous
fission.
3.3.3. Processing of evaluated experimental data
3.3.3.1. Data at mass numbers 99 and 140
The yields for mass numbers 99 (Nervik
[3.3.6]) and 140 (Blachot et al. [3.3.5] and Flynn et
al. [3.3.7]) were used as monitors in the relative
measurements. These data have to be renormalized