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High-temperature plumbing and advanced reactors
The use of nuclear fission power and its role in impacting climate change is hotly debated. Fission advocates argue that short-term solutions would involve the rapid deployment of Gen III+ nuclear reactors, like Vogtle-3 and -4, while long-term climate change impact would rely on the creation and implementation of Gen IV reactors, “inherently safe” reactors that use passive laws of physics and chemistry rather than active controls such as valves and pumps to operate safely. While Gen IV reactors vary in many ways, one thing unites nearly all of them: the use of exotic, high-temperature coolants. These fluids, like molten salts and liquid metals, can enable reactor engineers to design much safer nuclear reactors—ultimately because the boiling point of each fluid is extremely high. Fluids that remain liquid over large temperature ranges can provide good heat transfer through many demanding conditions, all with minimal pressurization. Although the most apparent use for these fluids is advanced fission power, they have the potential to be applied to other power generation sources such as fusion, thermal storage, solar, or high-temperature process heat.1–3
Mathieu Martin, Daniel Leonard, R. Brian Jackson, K. Michael Steer
Nuclear Technology | Volume 206 | Number 9 | September 2020 | Pages 1325-1336
Technical Paper | doi.org/10.1080/00295450.2020.1727263
Articles are hosted by Taylor and Francis Online.
TerraPower participated in a cooperative project among industry, a national laboratory, and a university to perform verification and validation of computational fluid dynamics (CFD) methods for predicting the flow and heat transfer within fuel assemblies with hexagonally packed wire-wrapped fuel pins. This project consisted of both experimental and numerical components and used surrogate fluids and electrically heated fuel pins to substitute for liquid metal and nuclear fuel. TerraPower performed CFD simulations of the experiments using industrial-level Reynolds-averaged Navier-Stokes (RANS) turbulence modeling. These simulations of helically wire-wrapped fuel assemblies employed meshes of bare pins without the wire-wrap geometry explicitly modeled. Instead, the effect of the wire-wrap on the flow is accounted for by introducing a momentum source (MS) into the governing fluid equations.
Solution validation was conducted by benchmarking the CFD simulations to the heated bundle experiments. These simulations used the as-tested boundary and operating conditions but were conducted blind. Pressure drop measurements and local temperature measurements were compared.
Axial pressure drop simulation results compared well with the experiment measurements. The vast majority of the local CFD temperatures matched thermocouple measurements within the instrument uncertainty. The good agreement between simulation and experiment supports the use of RANS-based CFD simulation methods and the specific applied MS method to model wire-wrapped fuel assemblies.