We propose to administer a financial aid mechanism for graduate students in nuclear engineering named the ���North Carolina State University���s Graduate Fellowship In Nuclear Engineering��� (NCSU���GFINE). The primary objective of NCSU���GFINE is to enhance the ability of NCSU���s Department of Nuclear Engineering to recruit and retain outstanding individuals and to provide incentive to the sponsored graduate students to maintain high academic performance along with promotion of diversity in the department���s graduate student population. Ultimately, the collective effort by US educational institutions to raise the admission standards and to diversify their graduate student populations, as proposed here for NCSU, will translate into a highly competent and diverse cadre of leaders for the nuclear engineering endeavor at large. The benefit to the nation from NCSU���GFINE is that it will contribute to the production of a highly competitive group of advanced-degree nuclear engineers capable of assuming leadership positions in their area of specialization within the field of nuclear engineering. The diverse profile of NCSU���GFINE fellows will be reflective of the US���s population and supportive of the nation���s goals of achieving social justice and economic equity for underprivileged groups. The so-developed workforce will be best positioned to lead the nation���s charge to reinvigorate its nuclear industry, and will shepherd the design, construction, operation, and regulation of new and innovative nuclear facilities, while maintaining the safety and security of processes for the handling of requisite nuclear materials. This proposal if awarded will support two graduate students per year over a four-year period through combined NRC support and NCSU cost share.

"Two-phase flow is a phenomenon important to the operation and safety of conventional Light Water Reactors (LWRs) and light-water cooled Small Modular Reactors (SMRs). Two-phase flow also plays a crucial role in many advanced reactor designs, even though the coolant may not boil during normal operations. In Molten Salt Reactors (MSRs) or Fluoride salt-cooled High-temperature Reactor (FHRs), gaseous fission products such as Xe and Kr are removed by inert gas bubbles injected into the salt coolant (Compere et al., 1975). For Sodium-cooled Fast Rectors (SFRs), it is of great interest to study sodium boiling and fission gas release into sodium coolant during a fuel failure scenario. Two-phase flow also exists in the heat-pipe cooled microreactors, in the reactor cavity cooling system (RCCS) for the High-Temperature Gas-cooled Reactors (HTGRs), and in all the secondary systems of the advanced reactors utilizing the Rankine cycle for power production. Essentially, two-phase flow is a fundamental phenomenon important to the advancement of all types of nuclear reactors. Even though two-phase flow has been studied for many decades in the past, it remains one of the most challenging problems in the design and safety analysis of various reactors. To design and license a new type of reactor, an enormous amount of separate-effect and integral-effect tests need to be carried out to prove its safety, which is often very costly and time-consuming. This issue is mainly because the current design tools, such as system analysis codes and CFD codes, are not capable of accurately predicting two-phase flows. These codes are largely based on the time-averaged two-fluid model, which requires a wide spectrum of closure correlations such as interfacial force models, interfacial area models, and boiling models. However, those models are strongly dependent on the two-phase flow interfacial structure, which involves complex phenomena such as bubble nucleation, bubble break-up, coalescence, and flow regime transition. Due to such complexity, the correlations developed from experimental data could be unusable if the application condition slightly deviates from the experimental condition. "

This fundamental research is motivated by three major global challenges that directly involve the transformation of gas molecules: carbon dioxide (CO2) capture for greenhouse gas mitigation, CO2 conversion to fuels and chemicals, and nitrogen (N2) gas conversion to biologically available ammonia to meet growing fertilizer demand. The research focuses on creating and investigating multi-functional interfaces that durably immobilize enzymes near their gaseous substrates while simultaneously delivering essential chemical and electrical reducing equivalents and removing reaction products to achieve maximum catalytic rates. Biocatalytic systems to be explored are: conversion of CO2 to bicarbonate catalyzed by carbonic anhydrase, reduction of CO2 to formate catalyzed by formate dehydrogenase, and reduction of N2 to ammonia catalyzed by nitrogenase. We envision that minimization of reaction barriers near immobilized biocatalyst interfaces involving gas molecule conversions will lead to transformative innovations that help overcome global sustainability challenges.

Direct numerical simulation (DNS) with interface capturing is capable of resolving and measuring thermal/hydraulic phenomena that is difficult or impossible to obtain in experiments. Of particular interest is the application of multi-phase DNS to forced convection nucleate boiling and evaluating the local effects resulting from near wall bubble motions, such as the quenching phenomena and enhanced heat transfer. Quenching occurs when a bubble departs the wall and cooler water rushes towards the nucleation site.

In recent years there has been renewed interest in advanced nuclear reactors, as a wave of investment has spurred innovation and novel reactor designs. Yet advanced reactors' design, certification, and licensing pose formidable hurdles to successfully deploying such technologies. The challenges in the current thermal-hydraulic modeling of advanced reactors are dual. Primarily, there is a severe deficit of direct thermal-hydraulic data that can be applied to new, innovative nuclear system designs due to a lack of integral-effect test facilities for the wide range of scenarios and conditions relevant to these systems. Secondly, the results of experiments that generate "big data" in advanced instrumented, small-scale, separate-effect experiments and high-fidelity numerical simulations) that could be used to bridge the gap are inefficiently utilized.

The goal of this research program is to gain fundamental understanding of the multi-phase plasma-gas-liquid system by utilizing both theoretical and experimental approaches. The plasma breakdown and streamer development in steep gradients will be investigated dependent on realistic bubble geometries and as a function of applied voltage conditions. The multiphase interface tracking DNS code PHASTA has been well-established through a wide variety of two-phase flow problems. When coupled with the well-established plasma modeling and characterization code nonPDPSIM, it will give new insights into gas bubble formation and how the size and shape of the bubbles will influence the breakdown of the plasma. The experiment will allow the production of various well-defined bubble shapes and sizes, making it possible to investigate the dependency of the plasma breakdown on bubble geometries. The project will provide 1) the initial steps to combine high-resolution multiphase physics with electric fields and plasma physics, opening the opportunity to study fundamental plasma physics in a multiphase system, and 2) the experimental investigations to benchmark the simulations and to study how the polarity of the applied voltage pulses affects the streamer propagation in a bubble in liquids.

The proposed research thrust aims to develop, demonstrate and apply high-fidelity direct numerical simulation (DNS) methods for multiphase flow and heat transfer with phase changes for flow conditions occurring during direct contact condensation (DCC) induced chugging phenomenon.

In this DOE-funded project the NCSU team will support the larger effort in establishing the knowledgebase for thermal-hydraulic multiscale simulation to accelerate the deployment of advanced reactors. NCSU focus will be on performing high resolution simulations of advanced reactor flows as well as developing advanced methodologies for data processing using machine-learning techniques.

The proposed scope will focus on demonstrating the DNS capabilities for GE���s problem of interest. Specifically, complex geometries and two-phase flow behavior at various flow conditions can be studied.

The proposed scope will focus on demonstrating the DNS capabilities for GE���s problem of interest. Specifically, complex geometries and two-phase flow behavior at various flow conditions can be studied. The following tasks can be planned for the first year of the project: 1) Identify geometry of interest to the industry and flow conditions suitable for DNS level meshing in collaboration with the CNP member 2) Demonstrate the meshing capabilities for selected geometry 3) Perform single phase flow simulations and collect basic statistics (e.g. averaged flow profiles) 4) Demonstrate two-phase flow simulation capabilities in flow regime suitable to DNS in this geometry 5) Evaluate the traditional modeling approach knowledge gaps and demonstrate how those can be narrowed / filled using high resolution simulations 6) Demonstrate how DNS statistical analysis can support for industry scale simulations capabilities