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Papers by Tatjana Jevremovic

Research paper thumbnail of Monte Carlo assessment of boron neutron capture therapy for the treatment of breast cancer

Nuclear Technology and Radiation Protection, 2005

Research paper thumbnail of Modeling reactors with AGENT: Verification, validation, efficiency analysis and 3D-Visuals on iPod

2010 1st International Nuclear & Renewable Energy Conference (INREC), 2010

Research paper thumbnail of Feasibility Study of the Underwater Neutron Radiography Facility Using the University of Utah 100 KW Triga (Uutr) Reactor

Research paper thumbnail of Automated Signal-Layered Algorithm for Processing Complex Gamma Radiation Spectra

Research paper thumbnail of Tritium measurements in neutron-induced cavitation of deuterated acetone

Nuclear Technology, 2006

Tsoukalas et al. TRITIUM MEASUREMENTS IN NEUTRON-INDUCED CAVITATION activity measurements are pra... more Tsoukalas et al. TRITIUM MEASUREMENTS IN NEUTRON-INDUCED CAVITATION activity measurements are practically within lo-of zero. Fur-thermore, the averaged value of activity change for all the deuterated acetone runs is 0.40 ± 0.47 dpm (ie, also within 1er of zero), and the averaged ...

Research paper thumbnail of Developing Experimental and Computational Nuclear Forensics Signals of Fast Neutron Irradiation Facility At TRIGA Reactor

ABSTRACT Developing Experimental and Computational Nuclear Forensics Signals of Fast Neutron Irra... more ABSTRACT Developing Experimental and Computational Nuclear Forensics Signals of Fast Neutron Irradiation Facility at TRIGA Reactor Ian Schwerdt, Joseph Levinthal, Chris Dances, Dong-OK Choe, Haori Yang, and Tatjana Jevremovic Nuclear Engineering Program, The University of Utah Abstract Over 230 research reactors are operating on campuses and labs across the globe. These research reactors are diverse in their design, fuel type, power, and fuel enrichment. Most TRIGA reactors use Uranium Zirconium Hydride (UZrH) fuel that initially was designed to contain High-Enriched Uranium (HEU). Majority have been converted into low-enriched uranium (LEU) fuel. Fast neutrons can be used in several applications such as neutron hardness experiments for electronics and material tests. Accurate neutron flux and radiation dose measurements and computational estimates in reactors’ irradiation facilities are of great importance for producing accurate nuclear signals of interest to nuclear forensics. The University of Utah houses a 100 kW TRIGA reactor (UUTR), with one of four irradiators such as the Fast Neutron Irradiation Facility (FNIF), thermal irradiation facility (TI) and other ports. The FNIF provides a neutron spectrum that approximates a fission spectrum. This paper presents experimental measurement and GEANT4 simulation of the neutron flux map in the UUTR’s FNIF, therefore creates a signature of this facility for future experiments and sample irradiation data analysis. The measurements were based on the activation of sulfur pellets positioned at the core side of the FNIF. These values are directly correlated to neutron flux and allows its mapping of the FNIF. The GEANT4 model of the FNIF provided neutron flux distribution with good agreement in comparison to the measured flux map. Further work will consist of a more detailed reactor model in GEANT4 and further data analysis of the P-32 samples to develop reliable and functional data to provide accurate nuclear forensics signatures. Key words: nuclear forensics, research reactor, TRIGA, fast neutron transport, GEANT4, flux map

Research paper thumbnail of Development of Educational Undergraduate Course Modules for Interactive Reactor Physics

Transactions of the American Nuclear Society, 2009

Research paper thumbnail of Intelligent Recognition of Signature Patterns in NRF Spectra

Nuclear Technology, Aug 1, 2011

Research paper thumbnail of A direct-cycle, supercritical light-water-cooled FBR, SCFBR-D

Research paper thumbnail of Systems design of direct-cycle supercritical-water-cooled fast reactors

Nuclear technology

... speaking, the reactor pressure vessel and control rods are similar to those of a pressurized ... more ... speaking, the reactor pressure vessel and control rods are similar to those of a pressurized water reactor, the containment and emergency core cooling system are similar to a BWR, and the balance of plant is similar to a supercritical-pressure fossil-fired power plant (FPP). ...

Research paper thumbnail of Core design of a direct-cycle, supercritical-water-cooled fast breeder reactor

The conceptual design of a direct-cycle fast breeder reactor (FBR) core cooled by supercritical w... more The conceptual design of a direct-cycle fast breeder reactor (FBR) core cooled by supercritical water is carried out as a step toward a low-cost FBR plant. The supercritical water does not exhibit change of phase. The turbines are directly driven by the core outlet coolant. In comparison with a boiling water reactor (BWR), the recirculation systems, steam separators, and dryers are eliminated. The reactor system is much simpler than the conventional steam-cooled FBRs, which adopted Loeffler boilers and complicated coolant loops for generating steam and separating it from water. Negative complete and partial coolant void reactivity are provided without much deterioration in the breeding performances by inserting thin zirconium-hydride layers between the seeds and blankets in a radially heterogeneous core. The net electric power is 1245 MW (electric). The estimated compound system doubling time is 25 yr. The discharge burnup is 77.7 GWd/t, and the refueling period is 15 months with a 73% load factor. The thermal efficiency is high (41.5%), an improvement of 24% relative to a BWR's. The pressure vessel is not thick at 30.3 cm.

Research paper thumbnail of Supercritical-pressure, light-water-cooled reactors for improving economy, safety, plutonium utilization and environment

Progress in Nuclear Energy, 1995

Research paper thumbnail of Assessment of Wavelet Processing in Removing Background Peaks from NRF Spectra

Research paper thumbnail of Automated Multisignal Detection of Special Nuclear Material in Cargo Containers

Research paper thumbnail of Heuristic Identification of Nuclear Materials from NRF Spectra

Research paper thumbnail of An Insight in Wavelet Denoising of Nuclear Resonance Spectra for Identification of Hazardous Materials

Research paper thumbnail of iMASS: Evolved NRF Simulations for More Accurate Detection of Nuclear Threats

Volume 2: Structural Integrity; Safety and Security; Advanced Applications of Nuclear Technology; Balance of Plant for Nuclear Applications, 2009

ABSTRACT The intelligent Model-Assisted Sensing System (iMASS) combines computer simulated nuclea... more ABSTRACT The intelligent Model-Assisted Sensing System (iMASS) combines computer simulated nuclear resonance fluorescence (NRF), real-time Monte Carlo analysis, and signal data processing for the detection of nuclear materials hidden in cargo containers. There are on average nine million cargo containers entering the US every year. Fast and robust scanning for nuclear materials and explosives is of the outmost importance for a country’s security and safety. This paper presents the Geant4 platform development for direct application in nuclear material detections, including: an improved module to simulate the bremsstrahlung spectra, a model for NRF simulations addressing the Compton continuum background that would be found during an actual scan, and the improvements in output data interpretation. The dynamic flexibility of Geant4 and the ability to be sped up with field programmable gate array (FPGA) and parallelization is also described.

Research paper thumbnail of LG-Graph Based Detection of NRF Spectrum Signatures: Initial Results and Comparison

2009 21st IEEE International Conference on Tools with Artificial Intelligence, 2009

ABSTRACT In this paper we present an enhanced version of our NRF spectra classifier based on loca... more ABSTRACT In this paper we present an enhanced version of our NRF spectra classifier based on local-global graphs (LG-graphs) and provide a comparison with other possible alternative detection schemes. Experimental results verify our claims that the proposed nuclear resonance fluorescence (NRF) signature detection methodology is favorable over other widely employed conventional feature extraction and signal representation methods. The LG-graph methodology is based on the representation of the signal's peaks as triangle-like shapes and then on extracting significant geometrical features from these triangles to derive a concise representation of the peaks that correspond to specific NRF signatures of interest. These features are used to enable the matching of the materials of interest in a new unknown NRF spectrum.

Research paper thumbnail of Expert System for Decision Making and Instructing Nuclear Resonance Fluorescence Cargo Interrogation

2009 21st IEEE International Conference on Tools with Artificial Intelligence, 2009

ABSTRACT Artificial intelligence has been recognized as a highly potential field for automation o... more ABSTRACT Artificial intelligence has been recognized as a highly potential field for automation of cargo scanning process. Specifically, intelligent systems have the capability to direct the process without the interference of a human operator and being able to make decisions. In this paper, an expert system for directing and instructing the cargo inspection, which is performed by means of nuclear resonance fluorescence (NRF), is presented. The empirical knowledge is embedded to the system through fuzzy sets while the inference mechanism is encoded by a set of fuzzy rules. The expert system gets as an input a set of parameters arrived from the NRF processing unit and decides whether the cargo is positive or negative in hazardous materials or no decision can be made. In the last case, the way that the sensing parameters should change, to improve next step detection results, is indicated.

Research paper thumbnail of Intelligent Order-Based Method for Synthesis of NRF Spectra and Detection of Hazardous Materials

2009 21st IEEE International Conference on Tools with Artificial Intelligence, 2009

ABSTRACT Clandestine transport of hazardous materials has been recognized as a major challenge fo... more ABSTRACT Clandestine transport of hazardous materials has been recognized as a major challenge for global aviation, water and land transport and homeland security. Nuclear resonance fluorescence (NRF) provides a high-potential physics basis for efficient detection of such materials at the entry points of a country. NRF's potency, however, is diminished due to varying environmental conditions and noisy background. Hence, fast and accurate signal processing algorithms are needed for detection and diagnostic purposes. In this paper a new method for identification of hazardous materials is proposed. The synergy of NRF signal processing and fuzzy logic allows an automated procedure for the detection of such materials. Automated decision making that does not require human interference improves the speed of the algorithm execution. The proposed method is tested on various scenarios aiming at the detection of Uranium-238 in NRF spectra.

Research paper thumbnail of Monte Carlo assessment of boron neutron capture therapy for the treatment of breast cancer

Nuclear Technology and Radiation Protection, 2005

Research paper thumbnail of Modeling reactors with AGENT: Verification, validation, efficiency analysis and 3D-Visuals on iPod

2010 1st International Nuclear & Renewable Energy Conference (INREC), 2010

Research paper thumbnail of Feasibility Study of the Underwater Neutron Radiography Facility Using the University of Utah 100 KW Triga (Uutr) Reactor

Research paper thumbnail of Automated Signal-Layered Algorithm for Processing Complex Gamma Radiation Spectra

Research paper thumbnail of Tritium measurements in neutron-induced cavitation of deuterated acetone

Nuclear Technology, 2006

Tsoukalas et al. TRITIUM MEASUREMENTS IN NEUTRON-INDUCED CAVITATION activity measurements are pra... more Tsoukalas et al. TRITIUM MEASUREMENTS IN NEUTRON-INDUCED CAVITATION activity measurements are practically within lo-of zero. Fur-thermore, the averaged value of activity change for all the deuterated acetone runs is 0.40 ± 0.47 dpm (ie, also within 1er of zero), and the averaged ...

Research paper thumbnail of Developing Experimental and Computational Nuclear Forensics Signals of Fast Neutron Irradiation Facility At TRIGA Reactor

ABSTRACT Developing Experimental and Computational Nuclear Forensics Signals of Fast Neutron Irra... more ABSTRACT Developing Experimental and Computational Nuclear Forensics Signals of Fast Neutron Irradiation Facility at TRIGA Reactor Ian Schwerdt, Joseph Levinthal, Chris Dances, Dong-OK Choe, Haori Yang, and Tatjana Jevremovic Nuclear Engineering Program, The University of Utah Abstract Over 230 research reactors are operating on campuses and labs across the globe. These research reactors are diverse in their design, fuel type, power, and fuel enrichment. Most TRIGA reactors use Uranium Zirconium Hydride (UZrH) fuel that initially was designed to contain High-Enriched Uranium (HEU). Majority have been converted into low-enriched uranium (LEU) fuel. Fast neutrons can be used in several applications such as neutron hardness experiments for electronics and material tests. Accurate neutron flux and radiation dose measurements and computational estimates in reactors’ irradiation facilities are of great importance for producing accurate nuclear signals of interest to nuclear forensics. The University of Utah houses a 100 kW TRIGA reactor (UUTR), with one of four irradiators such as the Fast Neutron Irradiation Facility (FNIF), thermal irradiation facility (TI) and other ports. The FNIF provides a neutron spectrum that approximates a fission spectrum. This paper presents experimental measurement and GEANT4 simulation of the neutron flux map in the UUTR’s FNIF, therefore creates a signature of this facility for future experiments and sample irradiation data analysis. The measurements were based on the activation of sulfur pellets positioned at the core side of the FNIF. These values are directly correlated to neutron flux and allows its mapping of the FNIF. The GEANT4 model of the FNIF provided neutron flux distribution with good agreement in comparison to the measured flux map. Further work will consist of a more detailed reactor model in GEANT4 and further data analysis of the P-32 samples to develop reliable and functional data to provide accurate nuclear forensics signatures. Key words: nuclear forensics, research reactor, TRIGA, fast neutron transport, GEANT4, flux map

Research paper thumbnail of Development of Educational Undergraduate Course Modules for Interactive Reactor Physics

Transactions of the American Nuclear Society, 2009

Research paper thumbnail of Intelligent Recognition of Signature Patterns in NRF Spectra

Nuclear Technology, Aug 1, 2011

Research paper thumbnail of A direct-cycle, supercritical light-water-cooled FBR, SCFBR-D

Research paper thumbnail of Systems design of direct-cycle supercritical-water-cooled fast reactors

Nuclear technology

... speaking, the reactor pressure vessel and control rods are similar to those of a pressurized ... more ... speaking, the reactor pressure vessel and control rods are similar to those of a pressurized water reactor, the containment and emergency core cooling system are similar to a BWR, and the balance of plant is similar to a supercritical-pressure fossil-fired power plant (FPP). ...

Research paper thumbnail of Core design of a direct-cycle, supercritical-water-cooled fast breeder reactor

The conceptual design of a direct-cycle fast breeder reactor (FBR) core cooled by supercritical w... more The conceptual design of a direct-cycle fast breeder reactor (FBR) core cooled by supercritical water is carried out as a step toward a low-cost FBR plant. The supercritical water does not exhibit change of phase. The turbines are directly driven by the core outlet coolant. In comparison with a boiling water reactor (BWR), the recirculation systems, steam separators, and dryers are eliminated. The reactor system is much simpler than the conventional steam-cooled FBRs, which adopted Loeffler boilers and complicated coolant loops for generating steam and separating it from water. Negative complete and partial coolant void reactivity are provided without much deterioration in the breeding performances by inserting thin zirconium-hydride layers between the seeds and blankets in a radially heterogeneous core. The net electric power is 1245 MW (electric). The estimated compound system doubling time is 25 yr. The discharge burnup is 77.7 GWd/t, and the refueling period is 15 months with a 73% load factor. The thermal efficiency is high (41.5%), an improvement of 24% relative to a BWR's. The pressure vessel is not thick at 30.3 cm.

Research paper thumbnail of Supercritical-pressure, light-water-cooled reactors for improving economy, safety, plutonium utilization and environment

Progress in Nuclear Energy, 1995

Research paper thumbnail of Assessment of Wavelet Processing in Removing Background Peaks from NRF Spectra

Research paper thumbnail of Automated Multisignal Detection of Special Nuclear Material in Cargo Containers

Research paper thumbnail of Heuristic Identification of Nuclear Materials from NRF Spectra

Research paper thumbnail of An Insight in Wavelet Denoising of Nuclear Resonance Spectra for Identification of Hazardous Materials

Research paper thumbnail of iMASS: Evolved NRF Simulations for More Accurate Detection of Nuclear Threats

Volume 2: Structural Integrity; Safety and Security; Advanced Applications of Nuclear Technology; Balance of Plant for Nuclear Applications, 2009

ABSTRACT The intelligent Model-Assisted Sensing System (iMASS) combines computer simulated nuclea... more ABSTRACT The intelligent Model-Assisted Sensing System (iMASS) combines computer simulated nuclear resonance fluorescence (NRF), real-time Monte Carlo analysis, and signal data processing for the detection of nuclear materials hidden in cargo containers. There are on average nine million cargo containers entering the US every year. Fast and robust scanning for nuclear materials and explosives is of the outmost importance for a country’s security and safety. This paper presents the Geant4 platform development for direct application in nuclear material detections, including: an improved module to simulate the bremsstrahlung spectra, a model for NRF simulations addressing the Compton continuum background that would be found during an actual scan, and the improvements in output data interpretation. The dynamic flexibility of Geant4 and the ability to be sped up with field programmable gate array (FPGA) and parallelization is also described.

Research paper thumbnail of LG-Graph Based Detection of NRF Spectrum Signatures: Initial Results and Comparison

2009 21st IEEE International Conference on Tools with Artificial Intelligence, 2009

ABSTRACT In this paper we present an enhanced version of our NRF spectra classifier based on loca... more ABSTRACT In this paper we present an enhanced version of our NRF spectra classifier based on local-global graphs (LG-graphs) and provide a comparison with other possible alternative detection schemes. Experimental results verify our claims that the proposed nuclear resonance fluorescence (NRF) signature detection methodology is favorable over other widely employed conventional feature extraction and signal representation methods. The LG-graph methodology is based on the representation of the signal's peaks as triangle-like shapes and then on extracting significant geometrical features from these triangles to derive a concise representation of the peaks that correspond to specific NRF signatures of interest. These features are used to enable the matching of the materials of interest in a new unknown NRF spectrum.

Research paper thumbnail of Expert System for Decision Making and Instructing Nuclear Resonance Fluorescence Cargo Interrogation

2009 21st IEEE International Conference on Tools with Artificial Intelligence, 2009

ABSTRACT Artificial intelligence has been recognized as a highly potential field for automation o... more ABSTRACT Artificial intelligence has been recognized as a highly potential field for automation of cargo scanning process. Specifically, intelligent systems have the capability to direct the process without the interference of a human operator and being able to make decisions. In this paper, an expert system for directing and instructing the cargo inspection, which is performed by means of nuclear resonance fluorescence (NRF), is presented. The empirical knowledge is embedded to the system through fuzzy sets while the inference mechanism is encoded by a set of fuzzy rules. The expert system gets as an input a set of parameters arrived from the NRF processing unit and decides whether the cargo is positive or negative in hazardous materials or no decision can be made. In the last case, the way that the sensing parameters should change, to improve next step detection results, is indicated.

Research paper thumbnail of Intelligent Order-Based Method for Synthesis of NRF Spectra and Detection of Hazardous Materials

2009 21st IEEE International Conference on Tools with Artificial Intelligence, 2009

ABSTRACT Clandestine transport of hazardous materials has been recognized as a major challenge fo... more ABSTRACT Clandestine transport of hazardous materials has been recognized as a major challenge for global aviation, water and land transport and homeland security. Nuclear resonance fluorescence (NRF) provides a high-potential physics basis for efficient detection of such materials at the entry points of a country. NRF's potency, however, is diminished due to varying environmental conditions and noisy background. Hence, fast and accurate signal processing algorithms are needed for detection and diagnostic purposes. In this paper a new method for identification of hazardous materials is proposed. The synergy of NRF signal processing and fuzzy logic allows an automated procedure for the detection of such materials. Automated decision making that does not require human interference improves the speed of the algorithm execution. The proposed method is tested on various scenarios aiming at the detection of Uranium-238 in NRF spectra.