Nuclear Engineering Commons^™

Design, Simulation, And Characterization Of A Deuterated Plastic Scintillator For A Portable Neutron Spectrometer, Anders M. Kinney Ii

Theses and Dissertations

This thesis examines the design, simulation, and experimental characterization of a novel deuterated plastic scintillator for portable neutron spectroscopy applications related to homeland security and nuclear non-proliferation. Using Monte Carlo N-Particle (MCNP) simulations and experimental tests with gamma-ray (¹³⁷Cs) and neutron sources (AmBe, ²⁵²Cf), this research shows that deuterium substitution in scintillators significantly enhances pulse shape discrimination (PSD) and neutron energy spectrum unfolding capabilities. Although deuterated scintillators demonstrate reduced overall light output, their higher stopping power and increased ionization quenching lead to superior neutron event differentiation, particularly between (α, n) and spontaneous fission neutrons critical for detecting …

Effective Management Of Disused Sealed Radioactive Sources In Uganda, Susan Nalumansi

International Journal of Nuclear Security

Sealed radioactive sources are used in a wide range of applications in Uganda, such as medicine, agriculture, geology, industry, and other fields. After a given useful period, the sealed sources can no longer perform their intended purpose and are thus regarded as disused. However, depending on the activity of the source, the disused sources are highly active and can cause significant damage to human health and the environment when mismanaged. A regulatory body was established with the mandate to regulate peaceful applications of ionizing radiation in Uganda. Given the vulnerability of sealed sources at the end of their life cycle …

Development Of P-Type Cesium Iodide Thin Film For Radiation Detection By Rf-Magnetron Sputtering, Rhett Simon Tabbada

Chulalongkorn University Theses and Dissertations (Chula ETD)

Cesium iodide (CsI) is a wide-bandgap alkali halide semiconductor with strong potential for radiation detection and optoelectronic integration, though its intrinsic insulating nature limits charge transport. In this study, the effects of silicon (Si) doping on the structural, optical, electrical, and radiation-response capabilities as a semiconductor of CsI thin films were determined. The CsI thin films were deposited on n-Silicon (n-Si) (100) substrates using magnetron sputtering. In the optimization of sputtering conditions, three films with a thickness of 250 nm were fabricated with varying sputtering power for Si: 0W, 5W, and 10W, while keeping the sputtering power for CsI constant …

การพัฒนาฟิล์มบางซีเซียมไอโอไดด์ชนิดเอ็นเพื่อการวัดรังสีด้วยเทคนิคสปัตเตอริง, กฤตยชญ์ คูณคณะ

Chulalongkorn University Theses and Dissertations (Chula ETD)

ผลึกซีเซียมไอโอไดด์เป็นหนึ่งในวัสดุอัลคาไลฮาไลด์ที่มีประสิทธิภาพมากในการตรวจจับรังสี แม้ว่าคุณสมบัติความเป็นฉนวนโดยธรรมชาติของมันจะจำกัดการถ่ายเทประจุ ในการศึกษานี้ ฟิล์มบางซีเซียมไอโดไดด์ถูกเจือด้วยทองแดงบนฐานรองซิลิกอนโดยใช้เทคนิคสปัตเตอริงซีเซียมไอโอไดด์สำหรับกำลังการปลูกที่ 30 วัตต์ ทองแดงสำหรับกำลังการปลูกที่ 50 และ 80 วัตต์ สมบัติเชิงโครงสร้าง คุณสมบัติทางแสง คุณสมบัติทางไฟฟ้า และการตอบสนองต่อรังสีของฟิล์มบางเหล่านี้ได้รับการตรวจสอบอย่างครอบคลุม ผลการวิเคราะห์สมบัติทางโครงสร้างผลึกโดยเทคนิค GIXRD พบว่า ฟิล์มบางที่สัเคราะห์ได้นี้เป็นโครงสร้างผลึกของซีเซียมไอโอไดด์ที่เจือด้วยทองแดง ซึ่งฟิล์มซีเซียมไอโอไดด์นี้มีค่าแลตทิซของหน่วยผลึกแบบบีบอัดขนาด 4.4102 Å (80 วัตต์) และขนาด 4.4516 Å (50 วัตต์) และค่าความเครียดลดลงจาก 3.29% เป็น 2.38% การวิเคราะห์เชิงแสงโดยใช้วิธี Tauc–Kubelka–Munk ระบุช่องแถบพลังานของซีเซียมไอโอไดด์พลังงานที่ 3.25 อิเล็กตรอนโวลต์ การศึกษาลักษณะทางไฟฟ้า ได้ผลว่า ฟิล์มซีเซียมไอโอไดด์ที่เจือด้วยทองแดง มีความหนาแน่นของพาหะคือ -1.822×1012 cm-3 ความคล่องตัวคือ 2.436×107 cm² V-1s-1 และสภาพต้านทานไฟฟ้าคือ 0.1407 Ω·cm และเมื่อนำฟิล์มซีเซียมไอโอไดด์นี้พัฒนาต่อให้เป็นอุปกรณ์ไดโอดรอยต่อพีเอ็นที่มีชั้นเคลือบทองคำชั้นบนสุดของชิ้นงาน Au/p-CsI/n-CsI:Cu/n-Si มาทดสอบการตอบสนองทางรังสีต่าง ๆ คือ แสงสว่าง รังสีแกมมา และอนุภาคแอลฟา ที่สภาวะแวดล้อมแสงต่างกัน ซึ่งผลการตอบสนองรังสีเหล่านี้เบื้องต้นได้ผลสัญญาณวัดในฟังก์ชันเวลาที่แสดงความแตกต่างกันได้ค่อนข้างชัดเจน และผลการทดลองนี้สามารถเป็นแนวทางในการพัฒนาโครงสร้างวัสดุซีเซียมไอโอไดด์ที่เจือทองแดงนี้ต่อไปเป็นหัววัดรังสีแอลฟาและรังสีชนิดอื่น ๆ ให้มีประสิทธิภาพดีขึ้นได้ในอนาคตต่อไป

การผลิตละอองลอยที่มีลูกหลานเรดอนเกาะติดสำหรับการประเมินปริมาณรังสียังผลที่ปอด, รุ่งโรจน์ สกุลเนรมิตร์

Chulalongkorn University Theses and Dissertations (Chula ETD)

งานวิจัยนี้มีวัตถุประสงค์เพื่อพัฒนาระบบและกระบวนการผลิตละอองลอยกัมมันตรังสีที่มีนิวไคลด์ลูกหลานเรดอนเกาะติดภายใต้สภาวะควบคุม เพื่อจำลองลักษณะทางกายภาพของอนุภาคในสิ่งแวดล้อมจริง และประเมินปริมาณรังสียังผลที่ปอดได้รับ โดยมุ่งเน้นการศึกษาในช่วงขนาดอนุภาค 10 ถึง 150 นาโนเมตร ซึ่งเป็นช่วงขนาดวิกฤตที่มีโอกาสตกสะสมในถุงลมปอดและส่งผลกระทบทางชีวภาพสูงสุด การศึกษาดำเนินการโดยใช้สารละลายตั้งต้น 3 ชนิด ได้แก่ โซเดียมคลอไรด์, กลูโคส และโพแทสเซียมเปอร์แมงกาเนต ที่ระดับ ความเข้มข้นแปรผันตั้งแต่ 1,000 ถึง 10,000 ppm ร่วมกับการศึกษาอิทธิพลของปัจจัยสิ่งแวดล้อม ได้แก่ อุณหภูมิ (25 และ 35 องศาเซลเซียส) และความชื้นสัมพัทธ์...

Investigation Of Radiation Absorption Behavior Of Banana Leaves And Onion: A Cost-Effective Way Of Radiation Protection, Arpita Datta, Alpana Goel, Shreya Singh

International Journal of Nuclear Security

Shielding of nuclear radiation is an important component of radiation safety aiming to reduce the exposure of ionizing radiation to radiation workers. In the present work, beta and gamma radiation absorption properties of various environmentally friendly natural materials such as onion, banana leaf, and banana stem were investigated with a view to understand their radiation shielding capability. Pure beta source ⁹⁰Sr–⁹⁰Y and gamma sources such as ²⁴¹Am, ¹³⁷Cs and ⁶⁰Co were used to study the attenuation of beta and gamma radiation using these natural materials. Intensity of the emitted radiation was measured by placing …

Design And Development Of A System That Characterizes Highintensity Gamma Fields From Rinsc Nuclear Fuel, Michael Peters

Open Access Master's Theses

Nuclear energy is a form of energy that utilizes the fissile nature of uranium, or other fissionable elements, to produce heat. In a uranium core, this reaction consists of a thermalized neutron being absorbed by the uranium nucleus, splitting the atom, and thus creating two subsequent fission products, along with the release of three neutrons, heat, and gamma radiation. These fission products are randomly generated elements, commonly in the form of isotopes of iodine, cesium, strontium, xenon, and barium. Although the type of fission products is known, much is still unknown about the nature of these isotopes, such as their …

Input Independent Observers For Bilinear Systems Using Convex Optimization, M. Aminul Haq, W. Steven Gray

Electrical & Computer Engineering Faculty Publications

An asymptotic state variable observer is proposed for a continuous-time bilinear dynamical system with the distinguishing feature that the error dynamics are globally asymptotically stable and independent of the applied input. Only the speed of convergence of the error dynamics may be input dependent. The approach is to apply classical Lyapunov stability theory using a convex optimization algorithm and linear matrix inequality (LMI) tools to in effect isolate the stability property of the error dynamics from the input. The LMIs are used to turn the nonconvex problem into a convex problem. The method is demonstrated on an induction motor drive.

Multiphysics Modeling Of Material Response To High-Intensity X-Ray And Laser Pulses: Heating, Ablation, And Plasma Expansion, Youssef Abouhussien

Theses and Dissertations

This dissertation presents a computational framework to investigate material response under high-intensity X-ray fluxes produced by an exo-atmospheric nuclear detonation and laser-material irradiations, with a focus on heating, ablation, and plasma expansion phenomena relevant to satellite vulnerability and high-energy-density environments. A hybrid Monte Carlo and Two-Temperature Model (MC-TTM) was developed to simulate X-ray and laser energy deposition and thermal relaxation in metals and semiconductors across a range of X-ray and laser pulse durations from femtoseconds to nanoseconds. Results demonstrate distinct thermal behavior between materials, with ablation thresholds and phase transitions captured in good agreement with experimental data.

In parallel, a …

Cfd Modeling And Simulation Of Natural Circulation In Helium- Cooled Very High Temperature Reactors, Mohammad Sakib U. Abrar

Dissertations and Theses

This thesis investigates the thermal-hydraulic behavior of natural circulation in helium-cooled Very High Temperature Reactor (VHTR) systems, focusing on the performance and validation of passive safety features under Pressurized or Depressurized Loss of Forced Cooling (P-LOFC or D-LOFC) events. An experimental facility inspired by the General Atomics 350 MWt Modular High Temperature Gas-Cooled Reactor (MHTGR) was developed at The City College of New York. The setup consists of a plenum-to-plenum flow loop with four riser and four downcomer tubes, each equipped with heating coils, thermocouples, and pressure sensors. Natural circulation is driven by density gradients induced by asymmetric heating of …

Hafnium Oxide-Based Nanoheterostructures For Catalytic Radiosensitization And Enhanced X-Ray Radiotherapy, Marlen Dariela Calix Quezada

Theses and Dissertations

Orthovoltage X-ray beams are attractive for surface and intra-operative radiotherapy. Yet, their clinical utility is constrained by rapid attenuation and the limited dose that can be delivered without harming healthy tissue. High-Z hafnium oxide (HfO₂) nanoparticles can boost local energy deposition through the photoelectric effect, while catalytic surface defects accelerate water radiolysis. Harnessing both mechanisms in a single nano-heterostructure could enable potent radiosensitization at diagnostic-range energies.

This thesis develops and evaluates HfO₂-based nanoheterostructures, both bare and Au-decorated, as catalytic radiosensitizers.

Two types of HfO₂ were evaluated, one was synthesized following a specific route and the …

Advanced Air Preheater Sealing Systems For Enhanced Efficiency And Reliability In Thermal Power Plants, Pavan Kumar Ravulaparthy

Theses and Dissertations

Global electricity generation still relies heavily on thermal power plants, which consume vast amounts of fuel and emit significant amounts of carbon dioxide. A major but often overlooked source of inefficiency in these plants lies within the rotary regenerative air preheater (RAPH), a critical heat-exchange component where air leakage can exceed 20% in aging units. This leakage increases fuel consumption, parasitic fan power, and CO₂ emissions, while degrading boiler reliability.

This research introduces advanced adaptive sealing systems designed to mitigate these losses by dynamically compensating for rotor eccentricity, thermal distortion, and wear under harsh operating conditions. Brush seals, composed of …

Laser Ablation-Induced Corrosion Resistance For Molten Salt Equipment Materials Evaluated Utilizing Electrochemical And Spectroscopic Analysis, Peggy Milota

Theses and Dissertations

Advanced reactors and used nuclear fuel separation (i.e. pyroprocessing technology) utilize high temperature salt as a thermal storage medium as well as an ionic solution for electrochemical processes. The use of these aggressive molten chloride and fluoride mediums requires specific materials or additional system alterations to extend the lifetime and structural integrity of equipment due to corrosion. Some materials, in the presence of inherently impure salt, will corrode and form oxide films in a specific formation that decreases corrosion rate by electrochemically and physically preventing elemental movement to the material surface. This is referred to as a passivation layer. However, …

Forgoing Nuclear: Nuclear Power Plant Closures And Carbon Emissions In The United States, Luke Petach

Funded Scholarship

This paper examines the effect of nuclear power plant decommissioning on electricity generation and carbon emissions in the United States. Using data on nuclear reactor closures in the United States between 1993 and 2022 and data on state-level carbon emissions and electricity generation from the Energy Information Administration (EIA), this paper adopts a difference-in differences (DiD) approach to estimate the effect of nuclear decommissioning. Two-way fixed-effects (TWFE) DiD estimates suggest a nuclear plant closure increases annual state-level per capita carbon emissions between 6% and 8%. The increase in state-level carbon emissions is driven by a substitution toward fossil fuel electricity—particularly …

Atmospheric Transport Of Radionuclides, Meteorological Data Mining & Synthesis For Site Data Supplementation, Ben Yao Sonpon

Doctoral Dissertations

"This research aligns with the NRC's vision of implementing risk-informed decision-making to support its regulatory charter. The suite of tools developed includes automated procedures for data mining and extracting meteorological (met) data from various national and regional repositories. A second data analytics tool automates the process of data fusion into a uniform format while preserving data fidelity. Autocorrelations were then established, and correlation coefficients were calculated between the Callaway Nuclear Power Plant (Callaway) and nearby off-site weather stations. The complexity of these correlations depends on factors such as physical proximity, geographic features, and topology, potentially necessitating multivariate analysis (MVA). Furthermore, …

Experimental Investgation Of Core Fluid And Heat Transfer Of Pwr By Using Advanced Measurments Techniques, Saud Aldawood

Doctoral Dissertations

This comprehensive study investigates the thermal-hydraulic mechanisms and convective heat transfer characteristics within (PWRs), with a focus on (SMRs) under both single-phase and two-phase bubbly flow conditions. Specifically, the research investigates the complex bubble dynamics in two-phase flow rod bundles, which are crucial for understanding reactor behavior during loss-of-coolant accidents (LOCA). Employing an advanced experimental setup developed at the (mFReel) at MST, this work measures critical parameters such as void fraction, bubble passage frequency, bubble velocity, bubble chord length, and interfacial area concentration (IAC) using a four-tip optical probe across various locations in the rod bundle. The findings reveal that …

Higher-Order Statistics And Normalized Decay Analysis For Detector Deadtime Characterization, Abdallah Wazzan

Doctoral Dissertations

Detector deadtime limits radiation measurement accuracy at high count rates, yet current methods rely on idealized paralyzable or non-paralyzable models. Real detectors exhibit hybrid behavior requiring advanced characterization approaches. This study explores deadtime characterization using two Monte Carlo simulation approaches: higher-order statistical analysis of inter-arrival times and simplified deadtime correction with hybrid models.

Using MATLAB (PULSE-WIZ), we analyzed full decay curves spanning ~4.5 half-lives of Cobalt-60 and Vanadium-52, examining coefficient of variation (CV), skewness, and kurtosis of inter-arrival times, plus normalized decay curves with Full Width at Half Maximum (FWHM) analysis. Hybrid models incorporated paralyzable and non-paralyzable components with dead …

Digital Twin-Centered Hybrid Data-Driven Multi-Stage Deep Learning Framework For Enhanced Nuclear Reactor Power Prediction, James Daniell, Kazuma Kobayashi, Ayodeji Alajo, Syed Bahauddin Alam

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

The accurate and efficient modeling of nuclear reactor transients is crucial for ensuring safe and optimal reactor operation. Traditional physics-based models, while valuable, can be computationally intensive and may not fully capture the complexities of real-world reactor behavior. This paper introduces a novel hybrid digital twin-focused multi-stage deep learning framework that addresses these limitations, offering a faster and more robust solution for predicting the final steady-state power of reactor transients. By leveraging a combination of feed-forward neural networks with both classification and regression stages, and training on a unique dataset that integrates real-world measurements of reactor power and controls state …

Impact Of Surface And Physical Property On Multiphase Flow In Sealed Vessel: Liquid Dropdown Performance, Mehedi Hasan Tusar, Palash K. Bhowmik, Kazuma Kobayashi, Syed Bahauddin Alam, Shoaib Usman

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

This study explores multi-phase (i.e., liquid-gas) and multi-fluid (i.e., air-water, and water-silicone oil) flow-pattern and flow-blockage physics phenomena for wall wettability conditions ranging from superhydrophilic to superhydrophobic cases in sealed vessels utilizing computational fluid dynamics (CFD) simulation tools and volume-of-fluid (VOF) method with sharp interface modeling. Detailed modeling and simulation (M&S) of such physics phenomena—in which liquid (e.g., water) stands over top of gas (e.g., air or steam) in a closed channel and exhibited flow blockage, flow reversal related challenges—are pivotal for design, analysis, and qualification of component-level (e.g., heat pipes, heat exchangers) to system-level (e.g., emergency core cooling systems …

Development Of Group Iii-V Quantum Confinement-Enabled Detectors: Bias-Tunable Quantum Well Infrared Photodetector (Qwip) And Quantum Dot Scintillation Detector (Qdsd), Gyana R. Biswal

Electronic Theses & Dissertations (2024 - present)

This dissertation discloses the physics, fabrication, characterization, and analysis of two novel types of group III-V semiconductor detectors relying on quantum confinement of carriers, namely voltage-tunable quantum well infrared photodetectors (QWIP) and a high-yield ultrafast quantum dot scintillation detector (QDSD). Both QWIP and QDSD heterostructures presented here were grown on 3” GaAs (001) substrates using molecular beam epitaxy (MBE).

A major part of the dissertation focuses on development of the voltage-tunable QWIPs targeting detection in the mid-wave infrared region (MWIR) (3μm -5μm) and long-wave infrared region (LWIR) (8μm -12μm) with control of sensitivity by the applied bias. The QWIPs utilize …