In the Verification Validation and Uncertainty Quantification process of modern simulation tools, the validation phase relies mainly on the comparison between calculation and experimental results for the major quantities of interest. For neutronics, the experiment database focuses on measurements coming from zero power reactors for which the reference states does not require complex multi-physics modeling: isothermal state (very low power such as few hundreds of watts) and fresh fuel (un-irradiated).
However, the VVUQ of power reactor needs to go beyond zero power experiments and thus arises the necessity to apply a multi-physics VVUQ approach. This new frame requires the integration of phenomena from other disciplines outside of pure neutronics: temperature and density dependence of the main quantities of interest (keff, power distribution, and feedback coefficients), temperature field inside the pins as function of core power and irradiation.
Regarding Doppler Effect, the set of experiments held at the SEFOR facility in the 70’s is of major interest for the VVUQ process. This sodium cooled fast reactor fed with mixed oxide fuel was built in support of the US R&D program for indigenous code validation at the time.
Based on the available data, the proposed work focuses on core characterization using a fully neutronic/thermo-mechanic/thermalhydraulic process for both nominal and transient states based in high-fidelity modeling. In order to quantify the benefit of such approach, a step-by-step comparison will be done with the same results obtained by the traditional “chained approach” which assumes a weak dependence between the three mentioned disciplines.
The work will be performed using the last generation of simulation tools available at CEA.