Toward local core outlet temperature monitoring in gas-cooled nuclear reactors using distributed fiber-optic temperature sensors

Holden C. Hyer; Dominic R. Giuliano; Christian M. Petrie

doi:10.1016/j.applthermaleng.2023.120847

Toward local core outlet temperature monitoring in gas-cooled nuclear reactors using distributed fiber-optic temperature sensors

Holden C. Hyer, Dominic R. Giuliano, Christian M. Petrie

Research output: Contribution to journal › Article › peer-review

9 Scopus citations

Abstract

Gas-cooled nuclear reactors operate at temperatures up to 950 ℃ with significant spatial variations in power generation and coolant flow through hundreds of parallel flow channels, resulting in complex mixing at the core outlet. The high temperatures and complex mixing can damage downstream components, challenge reactor calorimetry for power determination, and result in significant conservatism in calculated peak fuel temperatures, which ultimately limits the total power output. Directly measuring each gas stream individually is unrealistic using single point thermocouples, requiring more robust sensing techniques. Fiber-optic sensors are resilient to high temperatures (up to 1,000 ℃) and radiation damage. Moreover, distributed measurements can be made along the length of one fiber, making them potential candidates for monitoring local core outlet temperatures to improve core calorimetry and identify hot channels. To the authors’ knowledge, this manuscript is the first to report spatially distributed fiber optic temperature measurements to quantify mixing at the outlet of a relevant orifice plate under prototypic temperature and flow regimes to assess the feasibility of using fiber-optic sensors for distributed measurements of coolant temperature in gas-cooled reactors. A single optical fiber captured dynamic changes in local temperatures, whereas the mixed outlet temperature exhibited a muted response and could not identify which channels were responsible for the change in the mixed outlet temperature. The discussion focuses on potential challenges for deploying distributed optical fibers in gas-cooled reactors, including the effects of vibrations, radiation-induced signal attenuation and drift, and routing of the fiber while minimizing flow obstructions.

Original language	English
Article number	120847
Journal	Applied Thermal Engineering
Volume	230
DOIs	https://doi.org/10.1016/j.applthermaleng.2023.120847
State	Published - Jul 25 2023

Funding

This work was originally supported by the Transformational Challenge Reactor Program and later by the Advanced Materials and Manufacturing Technologies Program of the US Department of Energy's Office of Nuclear Energy. The authors thank Robert Sitterson for help in fabricating the support plate. The authors also thank David Holcomb and Nate See for providing feedback and assistance with editing the draft manuscript. Josh Jones and Tom Blue (Ohio State University) provided data to help calibrate the fiber-optic sensors tested in this work, and Dan Sweeney (Oak Ridge National Laboratory) helped analyze the calibration data. The image in Fig. 2(b) is Copyright 2022 by the American Nuclear Society, La Grange Park, Illinois. The image in Fig. 2(c) is Copyright 2022 American Nuclear Society, reprinted by permission of Taylor & Francis Ltd, http://www.tandfonline.com on behalf of 2022 American Nuclear Society. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). This work was originally supported by the Transformational Challenge Reactor Program and later by the Advanced Materials and Manufacturing Technologies Program of the US Department of Energy’s Office of Nuclear Energy. The authors thank Robert Sitterson for help in fabricating the support plate. The authors also thank David Holcomb and Nate See for providing feedback and assistance with editing the draft manuscript. Josh Jones and Tom Blue (Ohio State University) provided data to help calibrate the fiber-optic sensors tested in this work, and Dan Sweeney (Oak Ridge National Laboratory) helped analyze the calibration data. The image in Fig. 2 (b) is Copyright 2022 by the American Nuclear Society, La Grange Park, Illinois. The image in Fig. 2 (c) is Copyright 2022 American Nuclear Society, reprinted by permission of Taylor & Francis Ltd, http://www.tandfonline.com on behalf of 2022 American Nuclear Society.

Funders	Funder number
U.S. Department of Energy
American Nuclear Society
Office of Nuclear Energy
Oak Ridge National Laboratory

Keywords

Distributed sensing
Fiber-optic
Gas-cooled reactor
Nuclear power
Temperature sensor

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10.1016/j.applthermaleng.2023.120847

Cite this

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title = "Toward local core outlet temperature monitoring in gas-cooled nuclear reactors using distributed fiber-optic temperature sensors",

abstract = "Gas-cooled nuclear reactors operate at temperatures up to 950 ℃ with significant spatial variations in power generation and coolant flow through hundreds of parallel flow channels, resulting in complex mixing at the core outlet. The high temperatures and complex mixing can damage downstream components, challenge reactor calorimetry for power determination, and result in significant conservatism in calculated peak fuel temperatures, which ultimately limits the total power output. Directly measuring each gas stream individually is unrealistic using single point thermocouples, requiring more robust sensing techniques. Fiber-optic sensors are resilient to high temperatures (up to 1,000 ℃) and radiation damage. Moreover, distributed measurements can be made along the length of one fiber, making them potential candidates for monitoring local core outlet temperatures to improve core calorimetry and identify hot channels. To the authors{\textquoteright} knowledge, this manuscript is the first to report spatially distributed fiber optic temperature measurements to quantify mixing at the outlet of a relevant orifice plate under prototypic temperature and flow regimes to assess the feasibility of using fiber-optic sensors for distributed measurements of coolant temperature in gas-cooled reactors. A single optical fiber captured dynamic changes in local temperatures, whereas the mixed outlet temperature exhibited a muted response and could not identify which channels were responsible for the change in the mixed outlet temperature. The discussion focuses on potential challenges for deploying distributed optical fibers in gas-cooled reactors, including the effects of vibrations, radiation-induced signal attenuation and drift, and routing of the fiber while minimizing flow obstructions.",

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AB - Gas-cooled nuclear reactors operate at temperatures up to 950 ℃ with significant spatial variations in power generation and coolant flow through hundreds of parallel flow channels, resulting in complex mixing at the core outlet. The high temperatures and complex mixing can damage downstream components, challenge reactor calorimetry for power determination, and result in significant conservatism in calculated peak fuel temperatures, which ultimately limits the total power output. Directly measuring each gas stream individually is unrealistic using single point thermocouples, requiring more robust sensing techniques. Fiber-optic sensors are resilient to high temperatures (up to 1,000 ℃) and radiation damage. Moreover, distributed measurements can be made along the length of one fiber, making them potential candidates for monitoring local core outlet temperatures to improve core calorimetry and identify hot channels. To the authors’ knowledge, this manuscript is the first to report spatially distributed fiber optic temperature measurements to quantify mixing at the outlet of a relevant orifice plate under prototypic temperature and flow regimes to assess the feasibility of using fiber-optic sensors for distributed measurements of coolant temperature in gas-cooled reactors. A single optical fiber captured dynamic changes in local temperatures, whereas the mixed outlet temperature exhibited a muted response and could not identify which channels were responsible for the change in the mixed outlet temperature. The discussion focuses on potential challenges for deploying distributed optical fibers in gas-cooled reactors, including the effects of vibrations, radiation-induced signal attenuation and drift, and routing of the fiber while minimizing flow obstructions.

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Toward local core outlet temperature monitoring in gas-cooled nuclear reactors using distributed fiber-optic temperature sensors

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