The goal of this study is to look after the amount of information that is mandatory to get a relevant parameters optimisation by data assimilation for physical models in neutronic diffusion calculations, and to determine what is the best information to reach the optimum of accuracy at the cheapest cost. | Evaluation of relevant information for optimal reflector modeling through data assimilation procedures EPJ Nuclear Sci. Technol. 1 17 2015 Nuclear Sciences . Argaud et al. published by EDP Sciences 2015 amp Technologies DOI epjn e2015-50022-3 Available online at http REGULAR ARTICLE Evaluation of relevant information for optimal reflector modeling through data assimilation procedures Jean-Philippe Argaud Bertrand Bouriquet Thomas Clerc Flora Lucet-Sanchez and Angélique Ponçot EDF Recherche et développement 1 avenue du Général de Gaulle 92141 Clamart cedex France Received 6 May 2015 Received in final form 28 July 2015 Accepted 6 November 2015 Published online 16 December 2015 Abstract. The goal of this study is to look after the amount of information that is mandatory to get a relevant parameters optimisation by data assimilation for physical models in neutronic diffusion calculations and to determine what is the best information to reach the optimum of accuracy at the cheapest cost. To evaluate the quality of the optimisation we study the covariance matrix that represents the accuracy of the optimised parameter. This matrix is a classical output of the data assimilation procedure and it is the main information about accuracy and sensitivity of the parameter optimal determination. From these studies we present some results collected from the neutronic simulation of nuclear power plants. On the basis of the configuration studies it has been shown that with data assimilation we can determine a global strategy to optimise the quality of the result with respect to the amount of information provided. The consequence of this is a cost reduction in terms of measurement and or computing time with respect to the basic approach. 1 Introduction Thus there is an optimal amount of information that provides suitable results without too many measurements. The modeling of the reflector part of a nuclear PWR core is The purpose of this work is to generalise .