Program - Brookhaven National Laboratory

Session GA Evaluated Nuclear Data Libraries
Tuesday March 5, 2013
Room: Met East at 1:30 PM
GA 1 1:30 PM
Status of the ENDF/B Nuclear Data Library
Dave Brown
BNL
In December 2011, The Cross Section Evaluation Working Group (CSEWG) released its latest recommended
evaluated nuclear data file, the ENDF/B-VII.1 library. This library incorporated many advances
made in the five years after the release of ENDF/B-VII.0. That said, CSEWG is now preparing another release:
ENDF/B-VII.2. In this talk, I will outline some of the new or improved evaluations already prepared
for ENDF/B-VII.2 including new zirconium evaluations, new charged particle evaluations including a new
alpha-projectile sublibrary, and recent results from several NEA Working Party on Evaluation Cooperation
subgroups and IAEA Cooperative Research Projects. I will also discuss CSEWG’s expanded and automated
testing regime using the ADVANCE continuous integration system. In ADVANCE, every change
or addition to ENDF/B-VII.2 is tested automatically with NNDC’s checking codes and the PREPRO,
fudge and NJOY processing codes. As a side-effect of ADVANCE, we automatically produce usable ACE,
GENDF and PREPRO files for neutronics codes. Finally, in this talk I present some emerging initiatives
that impact the ENDF/B library, namely the move to a new nuclear data format (the Generalized Nuclear
Data format) and the possibility of a world-wide nuclear data library.
GA 2 2:00 PM
n+ 12 C Cross Sections from an R-Matrix Analysis of Reactions in the 13 C System
G. M. Hale and P. G. Young
Group T-2, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
We have performed an R-matrix analysis of reactions in the 13 C system, resulting in a new evaluation of the
neutron cross sections for 12 C at energies below about 6.5 MeV. This is the first new evaluation work that
has been done for carbon in many years, and it is part of an effort to separate the evaluation done by C. Y.
Fu et al. for natural carbon into isotopic evaluations for 12 C and 13 C. Carbon is, of course, an important
element in many technology applications, including nuclear power reactors, and its elastic scattering cross
section is a neutron standard at energies below 1 MeV. The analysis included the two channels n+ 12 C(0 + )
and n+ 12 C ∗ (2 + ), having lmax = 4 in the ground-state channel and lmax = 1 in the excited-state one.
Experimental data, including total cross sections, differential cross sections, and neutron analyzing powers,
were fitted for the reactions 12 C(n, n) 12 C and 12 C(n, n ′ ) 12 C ∗ at neutron lab energies below 6.5 MeV. Quite
a good fit (χ 2 /ν = 1.36) was obtained to the more than 6300 data points in the experimental data set
with 37 free parameters. The R-matrix parameterization included levels for a dozen bound states and
resonances at excitation energies up to 10.75 MeV, as well as fixed background levels in all J π submatrices.
Representative fits to the experimental data and comparisons to the previous evaluation will be shown.
Changes in the integrated and total cross sections are much less than those in the Legendre coefficients
representing the elastic and inelastic angular distributions. We will also discuss the implications of the
analysis for the level structure of 13 C at excitation energies below 10.75 MeV, and present covariance
information for the cross sections.
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