Open Access
ND 2007
Article Number 221
Number of page(s) 4
Section Benchmarking for fission applications
Published online 17 June 2008
International Conference on Nuclear Data for Science and Technology 2007
DOI: 10.1051/ndata:07332

A comparison of reaction rate calculations using ENDF/B-VII with critical assembly measurements

C. Wilkerson, M. Mac Innes, D. Barr, H. Trellue, R. MacFarlane and M. Chadwick

Los Alamos National Laboratory, Los Alamos, NM, USA

Published online: 21 May 2008

We present critical assembly reaction rate data, and modeling of the same using the recently released ENDF/B-VII library. While some of the experimental measurements were performed as long as 50 years ago, the results have not been widely used/available outside of Los Alamos. Over the years, a variety of target foils were fabricated and placed in differing neutron spectrum/fluence environments within critical assemblies. Neutron-induced reactions such as (n,γ), (n,2n), and (n,f) on these targets were measured, typically referenced to 235U(n,f) or 239Pu(n,f). Because the cross section for the latter reactions are now well known, these experiments provide a rich data set for testing evaluated cross sections. Due to the large variety of critical assemblies that were historically available at Los Alamos, it was possible to make measurements in spectral environments ranging from hard (Pu Jezebel, center of Pu Flattop) through intermediate (Big Ten) to degraded (reflector region of Flattop). This broad range of configurations allows us to test both the cross section magnitudes and their energy dependencies. We will present data, along with reaction rate predictions using primarily MCNP5 in conjunction with ENDF/B-VII, for a number of target nuclei, including iridium, isotopes of uranium (e.g., 233, 235, 237, 238), neptunium (237), plutonium (239), and americium (241).

© CEA 2008