Study on Tritium Behaviors in VHTR and Forward Osmosis Integration System
고온가스로의 폐열을 이용한 정삼투 담수화 시스템의 삼중수소 침투 거동에 대한 연구

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dc.description학위논문 (박사)-- 서울대학교 대학원 : 에너지시스템공학부, 2016. 2. 김응수.-
dc.description.abstractEnergy depletion and water scarcity are the two major global issues which are only intensifying due to global population growth. Efforts have been made to tackle the mentioned global issues and as an effective solution to this matter, the integration concept of the Very High Temperature Reactor (VHTR) and Forward Osmosis (FO) desalination is proposed. Through thermodynamic analysis calculations, the suggested VHTR-FO integration system is found to have significantly higher energy utilization rate than the existing nuclear desalination systems.
The VHTR-integrated system has the potential of tritium migration from the VHTR core to the integrated industrial system through permeation in the heat exchangers. As this is a very serious safety problem, the tritium behavior in the VHTR-integrated system must be analyzed and understood.
In order to understand and analyze tritium behavior in the VHTR-integrated system, the tritium code, Behavior of Tritium Analytic Code (BOTANIC) is developed using a chemical process code, gPROMS. The code involves tritium generation, sorption, leakage, purification, recombination, dissociation, permeation, trapping, release models. It is not only capable of tritium analysis but also chemical process analysis and system dynamics calculation. The developed code is verified using the analytical solutions and the benchmark code in step wise approach.
As the migration mainly occurs through permeation in the heat exchanger, this mechanism is the most important phenomena in understanding tritium behavior. In this study, the printed circuit heat exchanger (PCHE) permeation model is developed which accounts the geometry and thermal distribution across the PCHE wall. The existing permeation model is found to significantly over predict or under predict permeation rate whereas the developed PCHE permeation model is found to accurately calculate permeation rate within ± 20 %.
There is a lack of permeability data of hydrogen at low temperature region, the integration temperature region of VHTR and FO system. In order to resolve the error accounted with the lack of permeability at low temperature, hydrogen permeation experiment is conducted at low temperature region. Based on the permeability data, the effective permeability is defined and when compared with the permeability data it is found to be in good agreement.
Using the developed BOTANIC code, PCHE permeation model and effective permeability the tritium behavior in the proposed VHTR-FO desalination system is analyzed. The tritium level in the final water product of VHTR-FO system is found to exceed the regulatory limit an order. This stresses the necessity of tritium mitigation, thus, sensitivity analysis is conducted in order to figure out the effective parameters in reducing tritium level in final product. Based on the sensitivity analysis results, mitigation concepts are suggested and investigated
dc.description.abstractPHX tritium barrier, PHX material substitution and PHX pre-heat treatment.-
dc.description.tableofcontentsChapter 1 Introduction 1
1.1 Background and Motivation 1
1.1.1 Water Scarcity and Energy Depletion 1
1.1.2 Nuclear Desalination Technology 2
1.1.3 Tritium Permeation Issue in VHTR 4
1.2 Objectives and Scope 6

Chapter 2 Development of Integration concept of VHTR and FO 10
2.1 VHTR Power Conversion Systems 10
2.1.1 Helium Brayton Cycle 11
2.1.2 Supercritical Carbon Dioxide Brayton Cycle 12
2.1.3 Waste Heat Conditions for VHTR PCS options 13
2.2 Forward Osmosis Desalination 14
2.2.1 Overview of Forward osmosis 14
2.2.2 Membrane 16
2.2.3 Draw solute 19
2.2.4 Thermodynamic analysis of FO process 21
2.3 Thermodynamic Analysis of the Integrated System 24

Chapter 3 Development and Verification of Behavior of Tritium Analytic Code 43
3.1 Tritium Behavior 43
3.2 Physical Models 44
3.2.1 Conservation Equations 44
3.2.2 Tritium Generation 44
3.2.3 Tritium Loss 46
3.3 Development of BOTANIC 50
3.3.1 Code features 50
3.3.2 Code Structure 52
3.4 Verification of BOTANIC 53
3.4.1 Individual model verification 53
3.4.2 Total system verification 55

Chapter 4 Development of Tritium Permeation Model in Printed Circuit Heat Exchanger 73
4.1 3-D Tritium Permeation Modelling in PCHE 74
4.1.1 Assumptions and Conditions 74
4.1.2 Results 76
4.2 2-D Numerical Analysis and Parametric Study 76
4.2.1 Assumptions and Conditions 77
4.2.2 Grid Sensitivity Study 77
4.2.3 Parametric Study 78
4.2.4 Results 79
4.3 Tritium Permeation Model for PCHE 82
4.3.1 Shape Factor 82
4.3.2 Effective Diffusivity 86
4.3.3 Verification of the Developed Model 87

Chapter 5 Permeability Experiment at Low Temperature 107
5.1 Hydrogen Permeation Experiment 108
5.1.1 Description of the Hydrogen Permeation Facility (HYPER) 108
5.1.2 Experimental Procedure 108
5.1.3 Uncertainty Analysis 110
5.1.4 Effective Permeability 111
5.2 Grain Size Effect on Hydrogen Permeation 112
5.2.1 Effect of Temperature on Grain Size 112
5.2.2 Effect of Grain Size on Permeation 113

Chapter 6 Tritium Analysis of VHTR-FO integrated system 124
6.1 Tritium analysis on the proposed VHTR-FO system 124
6.2 Sensitivity Study on the VHTR-FO system 127
6.2.1 Key parameters 127
6.2.2 Results and Discussion 127
6.3 Tritium Mitigation Approaches 128
6.3.1 Overview 128
6.3.2 Evaluation on the suggested mitigation approaches 129

Chapter 7 Summary and Conclusions 144
7.1 Summary 144
7.2 Recommendations 147

Nomenclature 149

References 155

Appendix A BOTANIC Interface 164
Appendix B Tritium Barrier 166

Figure and Table 168

국문 초록 172
dc.format.extent10173215 bytes-
dc.publisher서울대학교 대학원-
dc.subjectGas turbine-
dc.subjectForward osmosis desalination-
dc.subjectPrinted Circuit Heat Exchanger-
dc.subjectTritium mitigation-
dc.titleStudy on Tritium Behaviors in VHTR and Forward Osmosis Integration System-
dc.title.alternative고온가스로의 폐열을 이용한 정삼투 담수화 시스템의 삼중수소 침투 거동에 대한 연구-
dc.contributor.AlternativeAuthorMin Young Park-
dc.contributor.affiliation공과대학 에너지시스템공학부-
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Energy Systems Engineering (에너지시스템공학부)Theses (Ph.D. / Sc.D._에너지시스템공학부)
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