STUDY ON UNCERTAINTY EVALUATION METHODOLOGY FOR DECAY HEAT REMOVAL EXPERIMENT IN SODIUM EXPERIMENTAL FACILITY

抄録

For enhancing the safety of sodium-cooled fast reactors (SFR), the development of a decay heat removal system using natural circulation (NC-DHRS) is a key issue. A numerical analysis method has been developed to evaluate thermal–hydraulic behaviors in a reactor vessel under the operation of a NC-DHRS at the Japan Atomic Energy Agency (JAEA). During the validation of the evaluation method, in addition to the uncertainties due to the numerical solution and the input parameters in simulations, it is important to quantify the uncertainties due to the experimental data. From this perspective, JAEA has been developing an experimental database for sodium experiments during operation of the NC-DHRS. In this study, the authors have proposed an uncertainty evaluation approach during the relative calibrations of thermocouples in sodium experiments. The proposed approach was applied to experimental data obtained in a sodium NC-DHRS experiment conducted at the sodium experimental facility, named PLANDTL-2. As a result, the uncertainties of the experimental data were successfully evaluated and the applicability of the methodology to temperature measurement in sodium experiments was confirmed. In the future, the uncertainty evaluation approach proposed in this study will be used to construct an experimental database with uncertainties for sodium experiments during the NC-DHRS operation.