About

Saya Lee is an Assistant Professor at the Thermal-Hydraulics Laboratory at The Pennsylvania State University, located in 219 Hallowell Building. Her research interests focus on experimental thermal hydraulics, reactor heat pipe applications, and micro reactor technologies. She leads a team of graduate and undergraduate students who work on various aspects of thermal hydraulics, including sodium heat pipe design, compact heat exchangers, and microreactor design. Her work involves studying advanced reactor design and the properties and limits of heat pipe wicks, contributing to the development of innovative thermal management solutions in nuclear reactor technology.

Research topics

• Computer Science
• Materials science
• Artificial Intelligence
• Thermodynamics
• Mechanics
• Physics
• Internet privacy
• Geography
• Mathematics
• Business
• Composite material
• Architectural engineering
• Engineering
• Optics
• Human–computer interaction
• Meteorology
• Geometry
• Advertising
• Multimedia

Selected publications

• Numerical Investigation and Optimization of Liquid Gallium Cooled Mini-channel Designs

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

• Development and Application of Reduced-Order Models for Thermal-Fluid Dynamics in Molten Salt Reactors

  Nuclear Technology · 2025-09-30

  article
  PublisherDOI

• Investigation of Reverse Recovery Failure Mechanism in SJ MOSFET with Increasing R _g

  2025-09-24

  articleSenior author

  We investigated the reverse recovery failure mechanisms in a 650 V -class Si superjunction (SJ) MOSFET with increasing gate resistance (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{R}_{\boldsymbol{g}}$</tex>) by experiments and TCAD simulations. We analyzed that physical failure occurs when two phenomena take place simultaneously: voltage overshoot exceeding a critical value and non-uniform reverse recovery operation, meaning that reverse recovery at the edge termination is not completed even after reverse recovery at the active has terminated. As <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$R_{g}$</tex> increases, the magnitude of overshoot increases due to the current imbalance between the drain-source capacitance, the parasitic inductance and a large gate delay of the device under test. This large overshoot eventually leads to device failures. This study confirms that the magnitude of overshoot depends on the electrical characteristics of the active rather than the edge termination, while the physical failure occurs on the edge termination area because the large current density and the voltage overshoot are applied due to the non-uniformity. Finally, we proposed strategies to develop the edge termination with improved resilience against physical failures in conditions with similar overshoot events.

  PublisherDOI

• High-Fidelity Modelling of the Molten Salt Fast Reactor

  ArXiv.org · 2025-07-05

  articleOpen access

  The Molten Salt Fast Reactor (MSFR) is one of the six GEN-IV reactor designs. In the MSFR, the liquid fuel is the coolant, which moves throughout the primary circuit. This complex phenomenology requires multiphysics modeling. In the present paper, a model of the MSFR is developed in the multiphysics code Cardinal, considering neutronic-thermal hydraulic feedback and the transport of delayed neutron precursors (DNPs) and decay heat precursors (DHPs). OpenMC is used to solve neutronic equations, and NekRS is used to solve mass, momentum, energy, DNPs, and DHPs distribution. A RANS k-t turbulence model is used in NekRS. DNPs and DHPs are modeled using a convective-diffusion equation with modified source terms considering radioactive decay. Cardinal results showed a reasonable behavior for temperature, heat source, velocity, DNPs, and DHPs. However, the current limitations in OpenMC do not allow the modification of delayed neutron source locations. Ongoing efforts look to include this feature in future work to introduce DNP feedback in OpenMC.

  PublisherOA PDF

• High-Temperature Fiber Optic Sensor Performance for Heat Pipe Instrumentation

  IEEE Sensors Journal · 2025-04-03 · 5 citations

  articleSenior author

  Presented in this paper are experimental results of an investigation on the performance of distributed fiber optic temperature sensors at temperatures up to 800 °C. The experimental results produced in this work assess the performance of fiber optic temperature sensors for use in instrumenting liquid metal heat pipes. Distributed fiber optic temperature sensors are capable of providing high spatial and temporal resolution temperature measurements across a wide range of operating temperatures and conditions, making them intriguing candidates for many advanced nuclear reactor technologies. Tests were conducted at high-temperature on the prolonged survivability, short-term performance, and hightemperature cycling effects of distributed optical fiber temperature sensors. A quartic fit of the spectral shift produced by the fiber sensors was developed to fit with thermocouple measurements of the experiment and was compared to fits available in literature. An upper limit of 700 °C was established for the prolonged use of distributed fiber optic sensors. No significant hysteresis effects were observed when the fiber sensors were cycled at high temperatures. Distributed fiber optic temperature sensors were determined to be viable for instrumenting liquid metal heat pipes under limited operational conditions.

  PublisherDOI

• High Temperature Gas Velocity Profile Measurement Using Fiber Optic Hot-Wire Velocimetry

  2024-08-04

  articleSenior author

  Abstract Most advanced reactors operate at high temperatures; however, there is a lack of local velocity measurement techniques that survive in the high-temperature, corrosive, and irradiation environments present in these reactors. In this experimental study, a Fiber Optic Hot-wire Anemometer (FO-HWA) using Rayleigh Backscattering is developed and applied to high-temperature airflow in a circular tube operating at temperatures exceeding 600 °C as the first step to developing a velocity profile measurement technique for high-temperature gas-cooled reactors. The circular tube is made of transparent borosilicate glass to allow for flow visualization measurement techniques to be applied at the desired temperature ranges. Additionally, the flow channel will be equipped with thermocouples to monitor the temperature of the flow. Also, inlet conditions were well controlled by applying a nine-to-one contraction and a flow straightener, which generates a uniform inlet velocity profile. A Time-Resolved Particle Image Velocimetry (TR-PIV) system consisting of a high-speed camera capable of recording at up to 9,000 frames per second and a high-power continuous green (532 nm) laser is applied simultaneously to the flow to generate validation data. The flow rate was controlled to cover laminar, transition, and turbulent flow regimes (Re: 1,800, 5,500, and 7,300). High-temperature air velocity profiles are obtained at those different flow rates by the FO-HWA and compared with the PIV data and existing experimental data in the literature. Considering the relatively thick sensor diameter compared with the traditional hot-wire sensors, the velocity data is post-processed to generate a time-averaged velocity profile, and the accuracy of the time-averaged velocity profile was discussed by comparing the results with the PIV data. The time-resolved capability of the FO-HWA is assessed. Also, the second moment of the temperature fluctuation measured by the FO-HWA and the velocity fluctuation measured by PIV were compared. The FO-HWA technique demonstrated in this study will be applied to higher temperatures, targeting over 800 °C, found in helium-cooled reactors and potentially the sodium vapor core of heat-piped cooled microreactors. In the present setup, the oxidation issue is not thoroughly resolved, although acceptable stability of the measurement is achieved. This may cause an issue for the long-term operation of the current setup. However, in the realistic target conditions mentioned above in advanced reactors, with the same stainless steel capillary tubing protection of the current setup, the oxidation issue can be mitigated compared with the present experimental condition with airflow. Eventually, with additional coating/protection techniques, the FO-HWA concept can be applied to other high-temperature energy-transporting fluids such as molten salt that can be used in nuclear fusion &amp; fission, and solar energy applications.

  PublisherDOI

• High-Fidelity Simulation of Pebble Beds: Toward an Improved Understanding of the Wall Channeling Effect

  2023-01-01 · 3 citations

  article
  PublisherDOI

• High-fidelity simulation of pebble beds: Toward an improved understanding of the wall channeling effect

  arXiv (Cornell University) · 2023-08-09

  preprintOpen access

  Wall channeling is a phenomena of interest for Pebble Bed Reactors (PBRs) where flow is diverted into high-porosity regions near the wall. This diversion of flow can have a significant impact on maximum fuel temperatures and core bypass flow. Porous media models that are currently used to model PBRs for design scoping and transient simulation are lacking in their capabilities to model the wall channel effect. Recent efforts at Penn State have produced an improved porous media pressure drop equation that is more capable of modeling the velocity variations caused by the wall channel effect in a porous media model. Several pebble beds were divided into concentric rings of $0.05D_{peb}$, and average flow quantities and porosities were extracted for the ring. A correlation between the form loss coefficient and the local ring porosity was found, allowing for the addition of a correction factor to the form loss term of the KTA equation. The developed correlation was purely empirical, and thus a more thorough understanding of the underlying flow phenomena is desired. This study investigates geometric and flow features that can explain the observed correlation between the form coefficient and the local porosity that was used to generate the improved pressure drop equation. The solid surface area to volume ratio $S_v$ along with the production of Turbulent Kinetic Energy (TKE) is analyzed. A relationship between $S_v$ and the local porosity and an inverse relationship between the negative TKE production and the local porosity were found, pointing to the idea that inertial effects caused by different pore geometry in each ring contribute to the variation of the form constant with the local porosity.

  PublisherOA PDFDOI

• Proposal of a Hand Motion and Control Method Matching System for Interaction Optimized for Mixed Reality Control: Focusing on Meta Interface and Augmented Behavior

  Korean Institute of Smart Media · 2022-10-31

  article1st authorCorresponding

  In an era where non-face-to-face meetings become common, eXtended Reality(XR) is rapidly developing and filling areas that are not satisfied in online meetings based on existing photos/video method. In particular, general users are also able to easily access and use HMD-type mixed reality devices. However, the basic operations applied in HMD-type in Mixed Reality(MR) with hands as the main input tool do not have a standardized system, and each manufacturer operates in a separate response to each other's hand movements. Therefore, this study considered that a systematic hand motion matching system considering the usability and efficiency of operations performed in mixed reality was necessary, and conducted a study to clarify this. First, the basic operation performed in the MR environment and its attributes were investigated, and at the same time, the structure of the hand and the attributes of the possible hand movements were identified. Based on the identified properties, it is intended to present a system that can intuitively and efficiently match basic operation properties in the MR environment with subtle operation properties according to the structure/context of the hand.

  PublisherDOI

• Flow structures of the cross-flow over a five-layer helically coiled steam generator geometry

  International Journal of Heat and Fluid Flow · 2022 · 9 citations

  1st authorCorresponding
  • Mechanics
  • Geometry
  • Physics
  PublisherOA PDFDOI

Frequent coauthors

• Yassin A. Hassan

  Texas A&M University

  58 shared

• Rodolfo Vaghetto

  Electric Power Research Institute

  19 shared

• Marilyn Delgado

  12 shared

• Suhaeb Abdulsattar

  Texas A&M University

  8 shared

• P. Jones

  Texas A&M University

  7 shared

• Nolan Goth

  6 shared

• N. K. Anand

  5 shared

• Mason Childs

  Idaho National Laboratory

  5 shared

Labs

• Thermal-Hydraulics LaboratoryPI

Education

• Ph.D., Nuclear Engineering

  University of California, Berkeley

  2000

• M.S., Nuclear Engineering

  University of California, Berkeley

  1996

• B.S., Nuclear Engineering

  University of California, Berkeley

  1994

Awards & honors

• Early Career Award