Natural circulation with DOWTHERM RP and its MARS code implementation for molten salt-cooled reactors

Abstract

SUMMARYRecently, molten salt has received attention as a promising coolant for advanced nuclear reactors, especially for fluoride salt-cooled high-temperature reactor. The heat transfer characteristics of molten salt provide great advantages for application as a primary coolant, because of its superior performance in terms of sustainability, economics, safety, and reliability compared with gas coolant. However, understanding the thermal-hydraulic characteristics of molten salts by experimental method is difficult because of its high-temperature corrosion and toxicity issue. Therefore, oil fluids were introduced as simulants for studying the heat transfer phenomena of high Pr (Prandtl number) molten salts. In this study, a scaleddown experiment using simulant oil was conducted, and scaling laws were applied to investigate a single-phase natural circulation, which is important in nuclear reactors as a part of their passive safety. DOWTHERM RP (Diaryl Alkyl) was considered as a heat transfer simulant in this study because it matches the relevant dimensionless numbers (Prandtl number, Ra, Grashof number, Reynolds number, etc.) with those of molten salt. Prior to the experiment, the thermophysical properties of both the liquid and vapor phases of DOWTHERM oils were implemented into thermal-hydraulic system analysis code or multi-dimensional analysis of reactor safety code, to enable simulation and further study of the molten salts. Then, natural circulation experiments were conducted with the scaled rectangular loop, to establish similarity and experimental feasibility. For the validation, two different codes (multi-dimensional analysis of reactor safety and computational fluid dynamics (CFD) were used to simulate the same natural circulation loop. From the experimental data, new heat transfer correlation for a single-phase natural convection was developed, and the existing heat transfer correlations were compared. Copyright

The Design of the Scaled-down Experimental Device for Molten Salts

“…and some disadvantages, mainly suboptimal scaling. Better scaling is provided by the use of thermal oils, e.g., experimental devices at the UC Berkeley [16], [17] and others [18], [19].…”

Experimental and simulation approach of the loop geometry effect on the natural circulation system of the advanced nuclear reactor

“…Paper 26 utilized molten nitrate salt consisted of a mixture of KNO 3 ‐NaNO 2 ‐NaNO 3 with a ratio of 53‐40‐7 wt% as the working fluid in the NCL with double heat exchangers. Also, the utilization of Diaryl Alkyl (DOWTHERM RP) that has dimensionless numbers relevant to molten salt, as the working fluid in the NCL, was conducted in paper 27 . These studies revealed that the instability of the NCL is influenced by the working fluid.…”

Transient analysis for liquid-fuel molten salt reactor based on MOREL2.0 code

“…In Japan, THORIMS‐NES concept and several loop experiments were performed by Furukawa for production of fissile U233 . In 2013, US researchers created an initial technology development roadmap for fluoride salt‐cooled high‐temperature reactors (FHRs) by combining a high temperature gas‐cooled reactor and MSR to improve the affordability of nuclear power . Further, the Chinese Academy of Sciences carried out “Thorium Molten Salt Reactor (TMSR) Nuclear Energy System” project to design Liquid‐Fuel TMSR (TMSR‐LF) and Solid‐Fuel TMSR in the next 20–30 years based on effective utilization of thorium, as shown in Figure…”

“…9 In 2013, US researchers created an initial technology development roadmap for fluoride salt-cooled high-temperature reactors (FHRs) by combining a high temperature gas-cooled reactor and MSR to improve the affordability of nuclear power. [10][11][12] Further, the Chinese Academy of Sciences carried out "Thorium Molten Salt Reactor (TMSR) Nuclear Energy System" project to design Liquid-Fuel TMSR (TMSR-LF) and Solid-Fuel TMSR in the next 20-30 years based on effective utilization of thorium, as shown in Figure 1. 13 The establishment of TMSR-LF with a graphite channel at lower power is the first-stage goal in the TMSR program.…”