Uncertainty and Sensitivity Investigations with TRACE-SUSA and TRACE-DAKOTA by Means of Post-test Calculations of NUPEC BFBT Experiments

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Publication Information

Manuscript Completed: January 2014
Date Published: August 2017

Prepared by:
Wadim Jaeger, Victor Hugo Sanchez Espinoza*
Francisco Javier Montero Mayorga, Cears Queral**

*Karlsruher Institute of Technology (KIT)
Institute for Neutron Physics and Reactor Technology (INR)
Hermann-von-Helmholtz-Platz 1
76344, Eggenstein-Leopoldshafen, Germany

**Universidad Politecnica de Madrd,
Departmento de Sistemas Energeticos ETSI Minas
28003 Madrid, Alenza 4, Spain

Kirk Tien, NRC Project Managerr

Division of Systems Analysis
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Published by:
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Uncertainty and sensitivity investigations are performed with TRACE-SUSA and with TRACE-DAKOTA for thermal hydraulic simulations of selected BWR related experimental scenarios based on the NUPEC BFBT data base. Steady state as well as transient scenarios are selected to conduct a comprehensive investigation of BWR like phenomena. The steady state investigations include single and two phase flow pressure drop analyses, axial void fraction profiles and critical power predictions. The pressure losses and the void fractions are also predicted during two postulated BWR transients; a turbine trip and a trip of a re-circulation pump. The average error for the pressure losses, the void fractions and the critical power scenarios is in the order of ± 5 %. Parameters of the input and of the source code are selected for the uncertainty and sensitivity study. By means of sensitivity coefficients, a quantitative way of evaluating the system response is given. The analysis shows that even small variations can cause a rather large spread of the output parameter(s). The investigations show also that the width of the predicted uncertainty band is a function of parameters like the inlet sub cooling or the hydraulic diameter. In addition, shortcomings of the thermal hydraulic code/modeling or of the uncertainty and sensitivity tool(s) are given in order to help to improve the prediction capabilities.

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