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Design, Testing and Modeling of the Direct Reactor Auxiliary Cooling System for FHRs

Lu, Qiuping
http://rave.ohiolink.edu/etdc/view?acc_num=osu1462544389

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Nuclear Engineering.
Direct Reactor Auxiliary Cooling System (DRACS) is a passive decay heat removal system proposed for the Fluoride-salt-cooled High-temperature Reactor (FHR) that combines coated particle fuel and a graphite moderator with a liquid fluoride salt as the coolant. The DRACS features three coupled natural circulation/convection loops, relying completely on buoyancy as the driving force. These loops are coupled through two heat exchangers, namely, the DRACS Heat Exchanger (DHX) and the Natural Draft Heat Exchanger (NDHX). In addition, a fluidic diode is employed to minimize the parasitic flow into the DRACS primary loop and correspondingly the heat loss to the DRACS during normal operation of the reactor, but to keep the DRACS ready for activation, if needed, during accidents. While the DRACS concept has been proposed, there are no actual prototypic DRACS systems for FHRs built or tested in the literature. The primary goal of the present research is to design, test, and model the DRACS for FHR applications. Previously, a detailed modular design of the DRACS for a 20-MWth FHR was developed. As a starting point, the DRACS was designed to remove 1% of the reactor nominal power, i.e., 200 kW decay power. In addition, a detailed scaling analysis has been performed to develop the key non-dimensional numbers that characterize the DRACS system. Based on the previous work on the prototypic DRACS design and scaling analysis, two scaled-down test facilities have been designed and constructed, namely, Low-temperature DRACS Test Facility (LTDF) and High-temperature DRACS Test Facility (HTDF). The LTDF has a nominal power capacity of 6 kW. It uses 1.0-MPa water as the primary coolant, 0.1-MPa water as the secondary coolant, and ambient air as the ultimate heat sink. The main purpose of the LTDF is to examine the couplings among the three natural circulation/convection loops in the DRACS, as well as to provide design and operation experience for the HTDF. An extensive test matrix has been developed for the LTDF, including steady-state tests and transient tests. The transient tests are further divided into three groups, namely, the startup test, and the pump trip tests with and without a simulated Intermediate Heat Exchanger (IHX). The decay heat removal capability of the DRACS based on natural circulations have been demonstrated in those tests. In addition, the experimental results from the LTDF have been scaled up to predict the system behaviors in the prototypic DRACS under three different accident scenarios. Natural circulations are found to be developed at time scales similar to those in the LTDF experiments. In addition, salt freezing is not observed in the three projected accident scenarios in the prototypic DRACS. However, the projected steady-state operation temperatures in the prototypic DRACS are higher than the design values, possibly due to the fact heat transfer has been over-predicted in the DHX design for both the LTDF and HTDF. The HTDF employs FLiNaK as the primary coolant, KF-ZrF4 as the secondary coolant, and air as the ultimate heat sink. The HTDF has been constructed and some preliminary tests have been performed. More tests are undergoing before the HTDF can be brought to operation. In addition to the experimental study on the DRACS using the LTDF and HTDF, a numerical investigation of the DRACS thermal performance has been performed. An in-house computer code based on the platform of MATLAB has been developed to predict the DRACS performance at both transients and steady states. This code is based on a one-dimensional formulation and its principle is to solve the energy balance and integral momentum equations. The code has been applied to both the LTDF and HTDF to predict their performance in the startup scenario and pump trip scenario. The predictions of the HTDF steady-state operation conditions agree well with the design values. The experimental data from the LTDF and eventually the HTDF could be used to validate/benchmark the developed in-house code for applications to future DRACS and FHR designs.
Xiaodong Sun (Advisor)
Tunc Aldemir (Committee Member)
Thomas Blue (Committee Member)
Richard Christensen (Committee Member)
Piyush Sabharwall (Committee Member)
311 p.
Nuclear Engineering
FHR, DRACS, passive decay heat removal, LTDF, HTDF

Recommended Citations

Citations

  • Lu, Q. (2016). Design, Testing and Modeling of the Direct Reactor Auxiliary Cooling System for FHRs [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462544389

    APA Style (7th edition)

  • Lu, Qiuping. Design, Testing and Modeling of the Direct Reactor Auxiliary Cooling System for FHRs. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1462544389.

    MLA Style (8th edition)

  • Lu, Qiuping. "Design, Testing and Modeling of the Direct Reactor Auxiliary Cooling System for FHRs." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462544389

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.