Improved best estimate plus uncertainty methodology, including advanced validation concepts, to license evolving nuclear reactors

• Published in: Nuclear engineering and design 2011-05, Vol.241 (5), p.1813-1833
• Main Authors: Unal, C., Williams, B., Hemez, F., Atamturktur, S.H., McClure, P.
• Format: Article
• Language: English
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2011.01.048

► The best estimate plus uncertainty methodology (BEPU) is one option in the licensing of nuclear reactors. ► The challenges for extending the BEPU method for fuel qualification for an advanced reactor fuel are primarily driven by schedule, the need for data, and the sufficiency of the data. ► In this paper we develop an extended BEPU methodology that can potentially be used to address these new challenges in the design and licensing of advanced nuclear reactors. ► The main components of the proposed methodology are verification, validation, calibration, and uncertainty quantification. ► The methodology includes a formalism to quantify an adequate level of validation (predictive maturity) with respect to existing data, so that required new testing can be minimized, saving cost by demonstrating that further testing will not enhance the quality of the predictive tools. Many evolving nuclear energy technologies use advanced predictive multiscale, multiphysics modeling and simulation (M&S) capabilities to reduce the cost and schedule of design and licensing. Historically, the role of experiments has been as a primary tool for the design and understanding of nuclear system behavior, while M&S played the subordinate role of supporting experiments. In the new era of multiscale, multiphysics computational-based technology development, this role has been reversed. The experiments will still be needed, but they will be performed at different scales to calibrate and validate the models leading to predictive simulations for design and licensing. Minimizing the required number of validation experiments produces cost and time savings. The use of multiscale, multiphysics models introduces challenges in validating these predictive tools – traditional methodologies will have to be modified to address these challenges. This paper gives the basic aspects of a methodology that can potentially be used to address these new challenges in the design and licensing of evolving nuclear technology. The main components of the proposed methodology are verification, validation, calibration, and uncertainty quantification – steps similar to the components of the traditional US Nuclear Regulatory Commission (NRC) licensing approach, with the exception of the calibration step. An enhanced calibration concept is introduced here, and is accomplished through data assimilation. The goal of this methodology is to enable best-estimate prediction of system behaviors in both normal and safety-rela