Program - Brookhaven National Laboratory

KC 2 2:00 PM
R-matrix Analysis for n+ 16 O Cross-Sections up to En = 6.0 MeV with Covariance
S. Kunieda, K. Shibata and T. Fukahori
Japan Atomic Energy Agency, Tokai-mura Naka-gun, Ibaraki 319-1195, Japan
T. Kawano, M. Paris, G. Hale
Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.A.
Oxygen is one of the most important materials in nuclear applications such as reactors, in the form of
water and oxide. Therefore, both experimental and theoretical studies have been devoted to know the
accurate neutron cross sections for 16 O over the years. Nowadays, the oxygen data in the evaluated nuclear
data libraries such as ENDF/B-VII.1, JENDL-4 and JEFF-3.1.2 are believed to be reasonable, since they
well perform in criticality benchmarks. Since there are increasing demands for giving uncertainties in
evaluated cross sections to estimate the margin of integral calculations, the covariance data are available in
ENDF/B-VII.1 and JENDL-4 for 16 O cross sections. However these covariances are estimated in a simple
way inferred only from experimental information. This situation is also true for many other light nuclei.
Purpose of this work is to estimate n+ 16 O cross sections and their uncertainties by analysing experimental
data with theoretical model. We carry out the R-matrix analysis for the 17 O system to deduce model
parameters with uncertainties up to En = 6.0 MeV. Because the (n, α) reaction channel opens at about
En = 2.4 MeV, two partitions of the 17 O system - 16 O+n and 13 C+α - are considered in the analysis.
Measured data we use are neutron total cross section for 16 O and 13 C(α, n) 16 O reaction cross sections.
The covariance matrix is obtained by propagating uncertainties of model parameters to the cross sections.
The uncertainty we obtained is strongly dependent on the resonant behavior.
KC 3 2:20 PM
Progress in Developing Nuclear Reaction Calculation Code CCONE for Higher Energy
Nuclear Data Evaluation
O. Iwamoto
Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency
The nuclear reaction calculation code CCONE [1] was developed and used for the nuclear data evaluation
for JENDL/AC-2008 and JENDL-4.0. It is planned to extend the evaluated data in JENDL-4.0 toward
higher energy. To adapt the CCONE code to the high energy nuclear data evaluation, the pre-equilibrium
exciton model part has been extended to be able to calculate multiple particle emission. It is realized
by sequential calculation of exciton states for all residual nuclei left by particle emissions. In addition,
Iwamoto-Harada cluster coalescence model has been incorporated in the multiple-emission exciton model
to improve calculation accuracies of cluster emission spectra such as alpha particles. The calculated results
of light particle emission spectra are compared with experimental data and evaluated data.
[1] O. Iwamoto, “Development of a Comprehensive Code for Nuclear Data Evaluation, CCONE, and
Validation Using Neutron-Induced Cross Sections for Uranium Isotopes”, J. Nucl. Sci. Technol., 44, pp.
687-697 (2007).
KC 4 2:40 PM
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