Bypass flow computations on the LOFA transient in a VHTR

Tung, Yu-Hsin; Johnson, Richard W.; Ferng, Yuh-Ming; Chieng, Ching-Chang

doi:10.1016/j.applthermaleng.2013.10.003

Cited by 9 publications

(3 citation statements)

References 12 publications

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“…The flow paths, interstitial gaps between upper shields and upper reflectors, still exists between upper plenum and core because the geometry of the graphite blocks changes over the lifetime of the reactor due to thermal expansions and irradiation damages. However, Tung's study discovered that the flow rate in such gaps under loss of forced cooling condition in prismatic HTGR is negligible compared to that in coolant holes (Tung et al, 2013). Hence, it can be concluded that the proposed structure can prevent massive air ingress into core in case of stand pipe rupture accidents.…”

Section: Proposed Upper Reflector Structurementioning

confidence: 96%

Design approach for mitigation of air ingress in high temperature gas-cooled reactor

Satō

Ohashi

Nakagawa

2017

Mechanical Engineering Journal

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One important safety design consideration for high temperature gas-cooled reactor (HTGR) is air ingress following a rupture of the reactor pressure boundary such as primary piping. The air intrusion to the reactor core held at high temperature through the break will results in significant oxidation of graphite components and fuels. Such oxidation may leads to the weakening of core support structures as well as fuel element damage and subsequent fission product release. This paper intends to propose a practical solution to protect the reactor from severe oxidation against air ingress accidents without reliance on subsystems. Firstly, a change is made to the center reflector structure to minimize temperature difference during the accident condition in order to reduce buoyancy-driven natural circulation in the reactor. Secondly, a modified structure of the upper reflector is suggested to prevent massive air ingress against a rupture in standpipes. As a preliminary study, a numerical analysis is performed for a typical prismatic-type HTGR to study the effectiveness of the proposed design concept using simplified lumped element models. The analysis considers internal decay heat generation and transient heat conduction from inner to outer regions at the reactor core, cooling of vessel outer surface by radiation and natural convection, and natural circulation flow in reactor. The results showed that amount of air ingress into the reactor can be significantly reduced with practical changes to local structure in the reactor.

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Section: Proposed Upper Reflector Structurementioning

confidence: 96%

Design approach for mitigation of air ingress in high temperature gas-cooled reactor

Satō

Ohashi

Nakagawa

2017

Mechanical Engineering Journal

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“…In addition to the heat exchangers, each flow loop will include high-temperature test sections operating at prototypical conditions that can be customized to address specific research issues associated with each working fluid. Possible research topics for the high-temperature helium test section include flow distribution, bypass flow, heat transfer in prototypical prismatic core configurations under forced and natural circulation conditions [9,10], parallel flow laminar instability during pressurized cooldown [11,12], and turbulent heat transfer deterioration [13,14]. Oxidation effects associated with water or air ingress could also be examined [15].…”

Section: Motivationmentioning

confidence: 99%

Strategic need for a multi-purpose thermal hydraulic loop for support of advanced reactor technologies

O’Brien¹,

Sabharwall²,

Yoon³

et al. 2014

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This report presents a conceptual design for a new high-temperature, multi-fluid, multi-loop test facility for Idaho National Laboratory (INL) to support thermal hydraulic, materials, and thermal energy storage research for nuclear and nuclear-hybrid applications. In its initial configuration, the facility will include a high-temperature helium loop, a liquid salt loop, and a hot water/steam loop. The three loops will be thermally coupled through an intermediate heat exchanger (IHX) and a secondary heat exchanger (SHX). Research topics to be addressed with this facility include the characterization and performance evaluation of candidate compact heat exchangers such as printed circuit heat exchangers (PCHEs) at prototypical operating conditions, flow and heat transfer issues related to core thermal hydraulics in advanced helium-cooled and salt-cooled reactors, and evaluation of corrosion behavior of new cladding materials and accident-tolerant fuels for light water reactors (LWRs) at prototypical conditions. Based on its relevance to advanced reactor systems, the new facility has been named the Advanced Reactor Technology Integral System Test (ARTIST) facility. Research performed in this facility will advance the state of the art and technology readiness level of high-temperature IHXs for nuclear applications, while establishing INL as a center of excellence for development and certification of this technology. The thermal energy storage capability will support research and demonstration activities related to process heat delivery for a variety of hybrid energy systems and grid stabilization strategies. Experimental results obtained from this research will assist in development of reliable predictive models for thermal-hydraulic design and safety codes over the range of expected advanced reactor operating conditions. Proposed/existing IHX heat transfer and friction correlations and criteria will be assessed with information on materials compatibility and instrumentation needs. The experimental database will guide development of appropriate predictive methods and be available for code verification and validation (V&V) related to these systems. viii ix ACKNOWLEDGMENTS The authors would like to acknowledge the Laboratory Directed Research and Development Program of the Nuclear System Design and Analysis Division for supporting the development of the advanced reactor technology multipurpose thermal hydraulic loop.

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“…Possible research topics for the hightemperature helium test section include flow distribution, bypass flow, heat transfer in prototypical prismatic core configurations under forced and natural circulation conditions [9,10], parallel flow laminar instability during pressurized cooldown [11,12], and turbulent heat transfer deterioration [13,14]. Oxidation effects associated with water or air ingress could also be examined [15].…”

Section: Introductionmentioning

confidence: 99%

Experimental facility for development of high-temperature reactor technology: instrumentation needs and challenges

Sabharwall¹,

O’Brien²,

Yoon³

et al. 2015

EPJ Nuclear Sci. Technol.

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Abstract. A high-temperature, multi-fluid, multi-loop test facility is under development at the Idaho National Laboratory for support of thermal hydraulic materials, and system integration research for high-temperature reactors. The experimental facility includes a high-temperature helium loop, a liquid salt loop, and a hot water/ steam loop. The three loops will be thermally coupled through an intermediate heat exchanger (IHX) and a secondary heat exchanger (SHX). Research topics to be addressed include the characterization and performance evaluation of candidate compact heat exchangers such as printed circuit heat exchangers (PCHEs) at prototypical operating conditions. Each loop will also include an interchangeable high-temperature test section that can be customized to address specific research issues associated with each working fluid. This paper also discusses needs and challenges associated with advanced instrumentation for the multi-loop facility, which could be further applied to advanced high-temperature reactors. Based on its relevance to advanced reactor systems, the new facility has been named the Advanced Reactor Technology Integral System Test (ARTIST) facility. A preliminary design configuration of the ARTIST facility will be presented with the required design and operating characteristics of the various components. The initial configuration will include a high-temperature (750°C), high-pressure (7 MPa) helium loop thermally integrated with a molten fluoride salt (KF-ZrF 4 ) flow loop operating at low pressure (0.2 MPa), at a temperature of ∼450°C. The salt loop will be thermally integrated with the steam/water loop operating at PWR conditions. Experiment design challenges include identifying suitable materials and components that will withstand the required loop operating conditions. The instrumentation needs to be highly accurate (negligible drift) in measuring operational data for extended periods of times, as data collected will be used for code and model verification and validation, one of the key purposes for the loop. The experimental facility will provide a much-needed database for successful development of advanced reactors and provide insight into the needs and challenges in instrumentation for advanced high-temperature reactors.

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Bypass flow computations on the LOFA transient in a VHTR

Cited by 9 publications

References 12 publications

Design approach for mitigation of air ingress in high temperature gas-cooled reactor

Design approach for mitigation of air ingress in high temperature gas-cooled reactor

Strategic need for a multi-purpose thermal hydraulic loop for support of advanced reactor technologies

Experimental facility for development of high-temperature reactor technology: instrumentation needs and challenges

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