Program - Brookhaven National Laboratory

each nucleus in agreement with uncertainties on nuclear data. In the case of shielding and propagation
of neutrons in a material thickness, two types of data are important because they impact the neutron
flux : the interaction cross sections and angular distributions (energetic distributions) of scattering reactions.
The neutron flux of high energy (above 100keV ) is particularly important in these studies and cross
sections from various libraries are in relatively good agreement taking into account uncertainties available
in evaluations. For energies higher than 1MeV , angular distributions of scatterings are increasingly
anisotropic and significant differences appear between the various libraries. These uncertainties on the
angular distributions should be correlated with the uncertainties on cross sections, which is unfortunately
not the case. In this paper, we present the impact of uncertainties on scattering anisotropies on the propagation
of neutrons in a bulk of iron, that is the ASPIS benchmark from the SINBAD Database [5]. For
this, there are two possibilities: the use of 31 evaluations of 56 F e from the TENDL2011 library or the use
of covariance matrices available in several libraries. The first solution is the simplest to implement. It
implies computation time and post processing for the analysis of results. The second solution requires the
treatment of evaluation ahead of simulation code. The ERRORJ (from NJOY [6]) and PUFF [7] codes do
not process extensively these informations. Therefore, we developed a module for processing such data.
For application to neutron transport, we use the Monte Carlo code TRIPOLI-4 [8]. As expected, the
variance-covariance data on angular distributions of scattering reactions have the greatest impact on the
dosimeter of sulfur. Indeed, the reaction used has a threshold of about 1.6 MeV and this dosimeter is
very sensitive on neutron fluxes between the threshold and 3.5 MeV, i.e. the range in which distributions
become highly anisotropic and where the variance-covariance are significant.
[1] M.B. Chadwick et al., Nuclear Data Sheets 112, 2887-2996 (2011) [2] K. Shibata et al., Journal of Nucl.
Scien. and Tech. 48, 1-30 (2011) [3] A. Santamarina et al., JEFF Report 22, (2009) [4] D. Rochman
and A.J. Koning, proceedings of Physor 2012, (2012) [5] I. Kodeli et al., Radiation protection dosimetry
116, 558 (2005) [6] R.E. MacFarlane and A.C. Kahler, Nuclear Data Sheets 111, 2739-2890 (2010) [7] D.
Wiarda et al., ORNL/TM-2006/147 (2006) [8] E. Dumonteil et al., Transactions of the American Nuclear
Society, 97, 694-695, 2007
PE 5 5:00 PM
MCNP6 Fission Cross Section Calculations at Intermediate and High Energies
Stepan G. Mashnik, Arnold J. Sierk, Richard E. Prael
Los Alamos National Laboratory, Los Alamos, NM 87545, USA
MCNP6 has been Validated and Verified (V&V) against intermediate- and high-energy fission-cross-section
experimental data. A previously unobserved error in the calculation of fission cross sections of 181 Ta and
other nearby target nuclei by the CEM03.03 event generator in MCNP6 and a technical “bug” in the
calculation of fission cross sections with the GENXS option of MCNP6 while using the LAQGSM03.03
event generator were detected during our current V&V work. After fixing both these problems, we find
that MCNP6 using the CEM03.03 and LAQGSM03.03 event generators calculates fission cross sections in
a good agreement with available experimental data for reactions induced by nucleons, pions, and photons
on both subactinide and actinide nuclei (from 165 Ho to 239 Pu) at incident energies from several tens of
MeV to about 1 TeV.
PE 6 5:15 PM
Development Progress of the GAIA Nuclear Data Processing Software
G. Ferran, W. Haeck
Institut de Radioprotection et de Surete Nucleaire (IRSN)
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