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

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3.2. EVALUATED REFERENCE FISSION YIELD DATA FILE
The Chinese reference fission yield file has
been established, in which all experimental data
available at the time of evaluation were considered.
The data were processed using the AVERAG codes
for calculating weighted averages, and ZOTT for
the simultaneous evaluation of experimental input
data. Our evaluated data were compared with those
from ENDF/B-VI, JEF-2, JENDL-3 and CENDL/
FY. The data were updated and improved, and
uncertainties were considerably reduced in
comparison with JEF-2 and CENDL/FY.
3.2.1. Introduction
Fission yield data used as standards in fission
yield measurements and evaluations or as monitors
in the nuclear industry for decay heat calculations,
burnup studies, etc., are referred to as ‘reference
fission yields’. These reference fission products and
their yields were selected and recommended by an
earlier IAEA CRP [3.2.1].
The uncertainties of relative yield measurements
depend directly on the accuracy of the
standard data, and the same situation applies to
yield data derived from measured ratios and
R values. Applied calculations, such as decay heat
and burnup, etc., also depend on the accuracy of the
monitor fission yield.
A summary is given of the formulation of this
file, including the evaluation method and the system
of supporting activities, the result of this evaluation,
and the comparison with yield data from other
evaluated libraries. Details of the evaluation can be
found in Refs [3.2.2–3.2.8], which describe the
evaluation of 235 U and 238 U reference fission yields
from 1997 to 2001.
3.2.2. Evaluation method
3.2.2.1. Data collection and selection
Experimental data were retrieved from the
EXFOR master data library and evaluated by using
the fission yield data evaluation system FYDES
[3.2.9]. Relevant data were also collected from the
Liu Tingjin, Liang Qichang
China Institute of Atomic Energy, China
open literature. All of the data collected are listed in
the tables of Refs [3.2.2–3.2.8]. The EXFOR BIB
information and papers were carefully studied and
the method and physics background were analysed.
The adoption or rejection of the data was based on
the date of the original study, the measurement
method and discrepancies compared with other
data. In general, the following data were discarded:
(a) The parameter(s) measured are not relevant
to this evaluation.
(b) There is something wrong with the
measurement or data analysis.
(c) Compared with other data, the discrepancy is
large and the measurement method is not
reliable, or no detailed information is given
concerning the experiment and/or analysis.
(d) The values or the reliability of the adopted
standard data in measurements of relative
data are not given in the paper. Such
information is indispensable in the evaluation
of ‘reference yield data’, and data cannot be
used that are based on standards of unknown
value or reliability.
As a result, about half of the data were discarded,
and half were used (for details, see Refs [3.2.2–
3.2.8]).
3.2.2.2. Data correction
If necessary, the measured data were
corrected for the values used for the standards,
g ray intensities and fission cross-sections (in
absolute measurements). As mentioned above, the
relative data were generally not used as published.
Such data were only selected when the standard
yields used by the authors correspond to, or agree
with, the recently evaluated values, or if they can be
corrected using our reference yields.
These corrections were made by using the
equation:
U U U
= 0
U
8
SO
(3.2.1)