Anton Moisseytsev

Experimental Investigations on Sodium Plugging in Narrow Flow Channels

Abstract A series of experiments was performed to investigate the potential for plugging of narrow flow channels of sodium by impurities (e.g., oxides). In the first phase of the experiments, clean sodium was circulated through the test sections simulating flow channels in a compact diffusion-bonded heat exchanger such as a printed circuit heat exchanger. The primary objective was to see if small channels whose cross sections are semicircles of 2, 4, and 6 mm in diameter are usable in liquid sodium applications where sodium purity is carefully controlled. It was concluded that the 2-mm channels, the smallest of the three, could be used in clean sodium systems at temperatures even as low as 100 to 110°C without plugging. In the second phase, sodium oxide was added to the loop, and the oxygen concentration in the liquid sodium was controlled by means of varying the cold-trap temperature. Intentional plugging was induced by creating a cold spot in the test sections, and the subsequent plugging behavior was observed. It was found that plugging in the 2-mm test section was initiated by lowering the cold spot temperature below the cold-trap temperature by 10 to 30°C. Unplugging of the plugged channels was accomplished by heating the affected test section.

Impact from the Adoption of Advanced Materials on a Sodium Fast Reactor Design

Abstract To improve the economic characteristics of fast reactors, researchers are developing advanced structural materials for application to reactor components. These advanced materials provide higher strength at elevated temperatures. Coupled thermal-hydraulic and structural analyses have been carried out to investigate the benefits of the advanced structural materials for a specific fast reactor design: the Advanced Burner Reactor (ABR) developed at Argonne National Laboratory. The benefits of the advanced materials, in terms of increased design margins, possible longer lifetime, thinner structures, and higher operating temperatures, were calculated for the major ABR structural components, including the reactor vessel, the core support structure, the intermediate heat exchanger, the intermediate heat transport system piping, and the steam generator. For each structure, the possible reduction in the component thickness was calculated and was converted into estimates of the commodities savings provided by the use of the advanced materials. Overall, a significant material mass saving of ~40% was calculated for the considered fast reactor structures.

Lessons Learned and Improvements in ANL Plant Dynamics Code Simulation of Experimental S-CO2 Loops

Validation of the ANL Plant Dynamics Code with the experimental data from integral S-CO2 cycle facilities has been continued. Several code modifications as well as modeling approaches and assumptions were introduced to improve both the code’s capabilities in modeling the experimental loops and the agreement of the code prediction with the experimental data. The lessons learned from the code improvement and modeling experience important for the validation of the codes with the experimental data from small-scale integral loops are presented.Copyright

A Supercritical CO2 Brayton Cycle Power Converter for a Sodium-Cooled Fast Reactor Small Modular Reactor

Although a number of power conversion applications have been identified or have even been developed (e.g., waste heat recovery) for supercritical carbon dioxide (S-CO2) cycles including fossil fuel combustors, concentrated solar power (i.e., solar power towers), and marine propulsion, the benefits of S-CO2 Brayton cycle power conversion are especially prominent for applications to nuclear power reactors. In particular, the S-CO2 Brayton cycle is well matched to the Sodium-Cooled Fast Reactor (SFR) nuclear power reactor system and offers significant benefits for SFRs. The recompression closed Brayton cycle is highly recuperated and wants to operate with an approximate optimal S-CO2 temperature rise in the sodium-to-CO2 heat exchangers of about 150 °C which is well matched to the sodium temperature rise through the core that is also about 150 °C. Use of the S-CO2 Brayton cycle eliminates sodium-water reactions and can reduce the nuclear power plant cost per unit electrical power. A conceptual design of an optimized S-CO2 Brayton cycle power converter and supporting systems has been developed for the Advanced Fast Reactor – 100 (AFR-100) 100 MWe-class (250 MWt) SFR Small Modular Reactor (SMR). The AFR-100 is under ongoing development at Argonne National Laboratory (ANL) to target emerging markets where a clean, secure, and stable source of electricity is required but a large-scale power plant cannot be accommodated. The S-CO2 Brayton cycle components and cycle conditions were optimized to minimize the power plant cost per unit electrical power (i.e.,

Validation of the ANL Plant Dynamics Code With the SNL S-CO2 Loop Transient Data

/kWe). For a core outlet temperature of 550 °C and turbine inlet temperature of 517 °C, a cycle efficiency of 42.3 % is calculated that exceeds that obtained with a traditional superheated steam cycle by one percentage point or more. A normal shutdown heat removal system incorporating a pressurized pumped S-CO2 loop slightly above the critical pressure on each of the two intermediate sodium loops has been developed to remove heat from the reactor when the power converter is shut down. Three-dimensional layouts of S-CO2 Brayton cycle power converter and shutdown heat removal components and piping have been determined and three-dimensional CAD drawings prepared. The S-CO2 Brayton cycle power converter is found to have a small footprint reducing the space requirements for components and systems inside of both the turbine generator building and reactor building. The results continue to validate earlier notions about the benefits of S-CO2 Brayton cycle power conversion for SFRs including higher efficiency, improved economics, elimination of sodium-water reactions, load following, and smaller footprint.Copyright

Transient Accident Analysis of a Supercritical Carbon Dioxide Brayton Cycle Energy Converter Coupled to an Autonomous Lead-Cooled Fast Reactor

The ANL Plant Dynamics Code (PDC) is the current state-of-the-art capability for one-dimensional system level transient analysis of supercritical carbon dioxide (S-CO2) Brayton cycle power converters. Earlier validation of code models was carried out with data from testing of individual S-CO2 components such as a small-scale compact diffusion-bonded heat exchanger and compressor tests. The steady-state part of the PDC has been compared with experimental data from the Sandia National Laboratories (SNL) small-scale S-CO2 Brayton cycle demonstration. In this work, predictions of the PDC code are assessed through comparison with SNL S-CO2 loop transient data. Code modifications were needed to properly simulate the actual experimental runs due to the unique features of the small-scale SNL loop. Overall, good agreement with the measured data is predicted by the PDC, although the code predictions could be improved in some cases. Future code improvements for comparisons with future SNL loop data are identified based upon the results.Copyright

Advanced Fast Reactor - 100 (AFR-100) Report for the Technical Review Panel

The Supercritical Carbon Dioxide (S-CO2 ) Brayton Cycle is a promising advanced alternative to the Rankine saturated steam cycle and recuperated gas Brayton cycle for the energy converters of specific reactor concepts belonging to the U.S. Department of Energy Generation IV Nuclear Energy Systems Initiative. A new plant dynamics analysis computer code has been developed for simulation of the S-CO2 Brayton cycle coupled to an autonomous, natural circulation Lead-Cooled Fast Reactor (LFR). The plant dynamics code was used to simulate the whole-plant response to accident conditions. The specific design features of the reactor concept influencing passive safety are discussed and accident scenarios are identified for analysis. Results of calculations of the whole-plant response to loss-of-heat sink, loss-of-load, and pipe break accidents are demonstrated. The passive safety performance of the reactor concept is confirmed by the results of the plant dynamics code calculations for the selected accident scenarios.Copyright

Lead-to-CO2 Heat Exchangers for Coupling of the STAR-LM LFR to a Supercritical Carbon Dioxide Brayton Cycle Power Converter

This report is written to provide an overview of the Advanced Fast Reactor-100 in the requested format for a DOE technical review panel. This report was prepared with information that is responsive to the DOE Request for Information, DE-SOL-0003674 Advanced Reactor Concepts, dated February 27, 2012 from DOE’s Office of Nuclear Energy, Office of Nuclear Reactor Technologies. The document consists of two main sections. The first section is a summary of the AFR-100 design including the innovations that are incorporated into the design. The second section contains a series of tables that respond to the various questions requested of the reactor design team from the subject DOE RFI.

Investigation of alternative layouts for the supercritical carbon dioxide Brayton cycle for a sodium-cooled fast reactor

Recent development of the Secure Transportable Autonomous Reactor-Liquid Metal (STAR-LM) lead-cooled natural circulation fast reactor (LFR) has been directed at coupling to an advanced power conversion system that utilizes a gas turbine Brayton cycle with supercritical carbon dioxide (S-CO2 ) as the working fluid. A key ingredient in achieving a coupled plant having a high efficiency are the modular lead-to-CO2 heat exchangers that must fit within the available volume inside the reactor vessel and must heat the S-CO2 to a high temperature. Thermal hydraulic performance and feasibility of seven different heat exchanger concepts has been investigated with respect to the achievement of a suitably high Brayton cycle efficiency for the coupled LFR-S-CO2 plant. The relative merits of the different heat exchanger configurations are revealed by the analysis which provides a basis to select the most promising concepts for further development.Copyright