Program - Brookhaven National Laboratory

Massachusetts Institute of Technology, Cambridge, MA 02139, USA
L. Leal, K. Guber
Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
S. Kopecky, P. Schillebeeckx, P. Siegler
Nuclear Physics Unit, EC-JRC-IRMM, Retieseweg 111, 2440 Geel, Belgium
Over the past decade, a discrepancy between the computed eigenvalues and the experimentally recorded
eigenvalues of criticality safety benchmark experiments containing copper was noticed by the nuclear data
and criticality safety community [1]. The most notable of these benchmarks is the set of highly enriched
uranium metal fuels with copper reflectors from the Zeus experiment, that is, HEU-MET, taken from the
ICSBEP compilation [2]. Used as a minor structural material in many nuclear facilities, copper is an
important structural component in Scandinavian spent fuel casks. To refine prediction of experimental
values for copper-containing benchmarks with a new copper cross section evaluation would be vital to the
safe operation of the advanced fuel cycle and from a criticality safety point of view. The need for a new
resonance evaluation was reflected in the United States Department of Energy (DOE) Nuclear Criticality
Safety Program (NSCP) Five-Year Execution Plan where 63,65 Cu were identified by the Nuclear Data
Advisory Group (NDAG) as ”Important for measurement and evaluation in the next five years” [3]. The
objective of this study is to address the issue discussed above by doing a new cross section evaluation
in the Resolved Resonance Region (RRR) for the two isotopes of copper. While applying the R-Matrix
SAMMY [4] method using the Reich-Moore (RM) approximation, the evaluation of a consistent set of
resonance parameters for 63,65 Cu is under way in the neutron energy range of 10 −5 eV up to 99.5 keV.
The extension of the RRR from 99.5 keV to 300 keV will also be performed. Invaluable information to
the evaluation process is provided by the 63,65 Cu (n,γ) high-resolution measurements performed by Guber
et al. at GELINA in 2011. Capture cross section measurements reveal resonances that are impossible to
identify from the transmission experiments alone. By combining capture measurements with transmission
data, one obtains a way of assigning the spin (total angular momentum) of nuclear resonances less ambiguously.
In the thermal energy range, cross section data are based on independent measurements performed
by Sobes et al. [5] at the MIT Nuclear Reactor (MITR). In the full paper we will present the evaluation
methodology as well as benchmarking efforts on the ICSBEP benchmark models sensitive to copper, such
as Zeus copper-reflected experiments [2] and newly evaluated Scandinavian criticality safety experiments
from the 1960s [6]. This new evaluation is done in support of the DOE Nuclear Criticality Safety Program
(NCSP).
[1] R. Mosteller, ”Benchmark Anomalies and Persistent Problems in Nuclear-Data Testing for ENDF/B-
VII.0,” presented at the MCNP Workshop at MCD + SNA 2007 , Monterey, CA, April 15, 2007. [2] International
Handbook of Evaluation Criticality Safety Benchmark Experiments, Nuclear Energy Agency, NEA,
September 2011. [3] ”United States Department of Energy, Nuclear Criticality Safety Program, Five-Year
Execution Plan for the Mission and Vision, FY 2011 through FY 2015,” http://ncsc.llnl.gov/plan/NCSP Five-
Year Plan 2011-2015 Final 12-02-10.pdf (2010). [4] N. M. Larson, Updated Users’ Guide for SAMMY:
Multilevel R-Matrix Fits to Neutron Data Using Bayes’ Equations, ORNL/TM-9179/R6, Oak Ridge National
Laboratory, Oak Ridge, TN (2008). [5] V. Sobes, R. Macdonald, L. C. Leal, B. Forget, K. Guber, G.
Kohse, ”Thermal Total Cross Section Measurement for 63Cu and 65Cu at the MIT Reactor,” Proceedings
of ANS Winter Meeting, Washington, DC, October 31 - November 4, 2011. [6] Personal communication
with Dennis Mennerdahl, Knoxville, TN, USA, April 17, 2012.
DC 8 5:45 PM
Neutron Irradiation Experiments: Automated Processing and Analysis of γ-Spectra
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