Program - Brookhaven National Laboratory

[1] H. J. Shim, et al., ”McCARD: Monte Carlo Code for Advanced Reactor Design and Analysis,” Nucl.
Eng. Technol., 44, 161-176 (2012). [2] H. J. Park, H. J. Shim, C. H. Kim, ” Uncertainty Quantification in
Monte Carlo Criticality Calculations with ENDF0B-VII.1 Covariance Data,” Trans. Am. Nucl. Soc., 106,
796 (2012).
Session LD Nuclear Power Applications
Wednesday March 6, 2013
Room: Empire West at 3:30 PM
LD 1 3:30 PM
Reactivity Impact of 2 H AND 16 O Elastic Scattering Nuclear Data for Critical Systems
with Heavy Water
D. Roubtsov, K.S. Kozier, J.C. Chow
AECL - Chalk River Nuclear Laboratories, Chalk River, Ontario, Canada
J.P. Svenne
University of Manitoba and Winnipeg Institute for Theoretical Physics, Winnipeg, Manitoba, Canada
L. Canton
Istituto Nazionale di Fisica Nucleare, Sezione di Padova, and Dipartimento di Fisica dell’Università di
Padova, via F. Marzolo 8, Padova, I-35131, Italy
A.J.M. Plompen, S. Kopecky
European Commission - Joint Research Centre - Institute for Reference Materials and Measurements,
Retieseweg 111, 2440 Geel, Belgium
The accuracy of deuterium nuclear data at thermal and epithermal neutron energies is important for reactor
physics simulations of heavy water (D2O) reactors. The main subjects having noticeable reactivity impact
for critical systems involving D2O are the value of the elastic scattering cross section at thermal neutron
energies, σs,th, the degree of backscattering in 2 H(n,n) 2 H elastic scattering at neutron incident energies
E < 3.2 MeV, which is characterized by the average scattering cosine, ¯µ, in the centre-of-mass reference
frame, and the adequacy of their numerical representation in evaluated nuclear data libraries. We discuss
how the uncertainty in the thermal scattering cross section of 2 H(n,n) 2 H propagates to the uncertainty of
the calculated neutron multiplication factor, keff , in thermal critical assemblies with heavy water neutron
moderator/reflector, such as the ZED-2 reactor in the Chalk River Laboratories. The method of trial
evaluated nuclear data files (Replica Method), in which specific cross sections are individually perturbed,
is used to calculate the sensitivity coefficients of keff to microscopic nuclear data, such as σs,th and ¯µ. The
thermal elastic scattering cross section data for 16 O(n,n) 16 O used in various modern nuclear data libraries
are found to be too high compared with the best available experimental measurements. The reactivity
impact of revising the 16 O scattering data downward to be more consistent with the best measurements
was also tested using the Replica Method. We discuss how the uncertainty in the thermal scattering cross
section of 16 O(n,n) 16 O propagates to the uncertainty of the calculated keff in thermal critical assemblies.
For example, large reactivity differences of up to about 5−10 mk (500−1000 pcm) were observed using
16 O data files with different elastic scattering data (MF=3 MT=2 data block of corresponding ENDFformat
files) in MCNP5 simulations of the Los Alamos National Laboratory HEU heavy water solution
thermal critical experiments included in the ICSBEP handbook. Finally, we discuss the low-epithermal
asymptotic behavior of σtot(D2O) vs. E, in which σtot is built from the evaluated nuclear data files of 2 H
and 16 O and compare it with the available experimental data and nuclear theory estimates for neutron
scattering on heavy water. The calculations of neutron-deuteron scattering cross sections are based on
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