Study on uncertainty evaluation methodology for decay heat removal experiment in sodium experimental facility

Akimoto, Yuta ; Ezure, Toshiki ; Onojima, Takamitsu; Kurihara, Akikazu 

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. During the validation of the evaluation method, in addition to uncertainties due to the numerical solution and input parameters in simulations, it is important to quantify uncertainties due to the experimental data. From this perspective, JAEA has been developing an experimental database and uncertainty evaluation methods for sodium experiments during operation of the NC-DHRS. In this study, the authors have proposed an uncertainty evaluation approach during relative calibrations of thermocouples in sodium experiments. The proposed approach was applied to experimental data obtained in a sodium NC-DHRS experiment conducted at PLANDTL-2. As a result, uncertainties of the experimental data were successfully evaluated and the applicability of the method to temperature measurement in sodium experiments was confirmed.