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Science and Technology of Nuclear Installations
Volume 2012, Article ID 109614, 11 pages
Research Article

Computational Method for Global Sensitivity Analysis of Reactor Neutronic Parameters

Research and Development Division, The South African Nuclear Energy Corporation (Necsa), Building 1900, P.O. Box 582, Pretoria 0001, South Africa

Received 25 April 2012; Accepted 5 October 2012

Academic Editor: Kostadin Ivanov

Copyright © 2012 Bolade A. Adetula and Pavel M. Bokov. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The variance-based global sensitivity analysis technique is robust, has a wide range of applicability, and provides accurate sensitivity information for most models. However, it requires input variables to be statistically independent. A modification to this technique that allows one to deal with input variables that are blockwise correlated and normally distributed is presented. The focus of this study is the application of the modified global sensitivity analysis technique to calculations of reactor parameters that are dependent on groupwise neutron cross-sections. The main effort in this work is in establishing a method for a practical numerical calculation of the global sensitivity indices. The implementation of the method involves the calculation of multidimensional integrals, which can be prohibitively expensive to compute. Numerical techniques specifically suited to the evaluation of multidimensional integrals, namely, Monte Carlo and sparse grids methods, are used, and their efficiency is compared. The method is illustrated and tested on a two-group cross-section dependent problem. In all the cases considered, the results obtained with sparse grids achieved much better accuracy while using a significantly smaller number of samples. This aspect is addressed in a ministudy, and a preliminary explanation of the results obtained is given.