Development and application of a tool for the sensitivity and uncertainty analysis

The AZTLAN Platform project is a national initiative led by the National Institute of Nuclear Research, which brings together the leading public institutions of higher education from Mexico, as the National Polytechnic Institute, the National Autonomous University of Mexico, and the Metropolitan Autonomous University, to take a significant step towards the autonomy of calculation and analysis, and with the aim to place Mexico in the mid- and long-terms at a competitive international level in the diverse aspects of nuclear reactor analysis software. The software involved in the AZTLAN Platform integrates enhanced and upgraded computational codes for neutronics, thermal hydraulics, and thermomechanical analyses. These codes in the integrated platform will be developed and maintained by Mexican experts for the consequent benefit of Mexican institutions. This project, supported by the SENER-CONACYT´s Energy Sustainability Fund, substantially strengthens research institutions and, at the same time educational institutions, by helping in the training of specialized human resources in the area of analysis and design of nuclear reactors. The activities of the Working Group 3: Coupling and sensitivity analysis and uncertainty, has, as one of its main objectives, the development, verification, and validation of the AZTUSIA (AZtlan Tool for Uncertainty and Sensitivity Analysis) computational code, which complements the use of best-estimate codes, which in turn, are used to perform calculations with a realistic approach, instead of traditional conservative approaches. Although AZTUSIA is the main product of this research project, it was developed as part of the AZTLAN project with the aim of providing the necessary tools to carry out comprehensive sensitivity and uncertainty analysis, to be applied to a wide variety of problems. The main characteristics of AZTUSIA are listed: 1) Generation of a sample of selected input parameters, by means of a sampling with the Monte-Carlo method. Sample size can be calculated using Wilks/Wald equations or it can be defined by own criteria. For each parameter its respective associated Probability Density Function (PDF) is provided. AZTUSIA currently has 4 PDF options: Uniform, Normal Log, Triangular and Normal. 2) It is currently directly coupled with AZTRAN (AZtlan TRANsport code, neutron code of the AZTLAN platform), generating the sample and executing the code to provide a sample output of the code results. It can also be coupled to other codes,both neutron and thermohydraulic, as PARCS,TRACE,SIMULATE3-K, MAAP, to name a few. 3) Having the set of FoMs of the output sample, uncertainty bands can be generated and minimum, maximum, and average values can be obtained for each FoM. 4) With the set of input parameters and FoMs four different Correlations can be calculated: Pearson Simple Correlation Coefficient (PSCC), Spearman Rank Correlation Coefficient (SRCC), Partial Correlation Coefficient (PCC) and Partial Rank Correlation Coefficient (PRCC). The AZTUSIA code was verified with the help of specialized academic personnel at the Polytechnic University of Madrid (UPM) via a reference problem for a PWR reactor, whose model was developed at the Department of Mines, Energy, and Nuclear Fuels of the UPM. Additionally, and as part of the validation process of AZTUSIA, a sensitivity and uncertainty analysis was applied to a stability scenario of a BWR, whose reference model is similar to those of the two units at Laguna Verde Nuclear Power Plant. (author)