This work presents a sensitivity study of boiling and two phase flow models for thermal hydraulics simulations in nuclear reactors. This study quantifies sources of uncertainty and error in these simulations by computing global sensitivities of figures of merit, or output, to model parameters, inputs, and mesh resolution. Results are obtained for the DEBORA benchmark problem of boiling in a channel driven by a heated wall section. Scalar outputs of interest consist of axial pressure drop, average wall temperature in the heated section, average void fraction at the end of the heated section, and the centroid of the radial distribution of the void fraction at the end of the heated test section. Sensitivities to both individual heat fluxes and to the parameters in the models for these heat fluxes are computed.
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