Critical Heat Flux (CHF) enhancement of ZrSi2 Accident Tolerant Fuel (ATF) cladding using Electrophoretic Deposition (EPD)

다국어 초록 (Multilingual Abstract)

Critical heat flux of ZrSi2 coated Zircaloy-4 (ZrSi-Zry) has been evaluated and improved using Electrophoretic Deposition (EPD) in flow boiling. Two different porous layers were produced by changing the process conditions and have been characterized. The particle size, thickness and porosity were characterized using particle sizer and FIB (Focused Ion Beam) analysis. Critical Heat Flux (CHF) was evaluated on Zircaloy-4 (Zry-4), ZrSi-Zry and ZrSi-Zry modified with EPD (EPD ZrSi-Zry). Capillary wicking on EPD ZrSi-Zry has been evaluated by liquid rise experiment and the liquid rise height according to time has been modeled. This model could predict the CHF enhancement of the EPD ZrSi-Zry and predicted CHF enhancement has been compared with the actual CHF enhancement in flow boiling experiment. The bubble dynamics on ZrSi-Zry and EPD ZrSi-Zry were visualized to investigate the effect of EPD on dried out area and re-wetting time. The bubble residence time (re-wetting time) and vapor mushroom diameter (Db) were calculated according to heat fluxes.

국문 초록 (Abstract)

지르코늄실리사이드가 코팅된 지르칼로이의 임계열유속이 유동비등 상황에서 평가되고 전기영동증착을 통해 증진되었다. 두 가지 공질성 코팅이 공정 조건 변화를 통해 형성되었고 표면 특성이 평가되었다. 입자의 크기, 두께 그리고 공질도가 입도분석기와 FIB를 통해 분석되었다. 지르칼로이, 지르코늄 실리사이드가 코팅된 지르칼로이 그리고 전기영동증착을 통해 표면이 개질된 지르코늄 실리사이드 (전기영동증착 지르코늄 실리사이드)가 코팅된 지르칼로이에 대해서 임계열유속이 평가되었다. 전기영동증착 지르코늄 실리사이드의 모세관 위킹이 물 상승 높이 측정 실험을 통해 평가되었고, 시간에 따른 물 상승 높이가 모델링되었다. 물 상능 높이 측정 실험과 모델을 통해 예측된 임계열유속 증진이 실험적인 증진과 비교되었다. 지르코늄 실리사이드가 코팅된 지르칼로이와 전기영동증착 지르코늄 실리사이드에서의 기포 거동을 가시화를 통해 관찰하였고, 전기영동증착이 표면의 마른 영역의 넓이와 표면이 다시 적셔지는 데 걸리는 시간에 미치는 영향에 대해서 연구가 수행되었다. 표면이 다시 적셔지는 데 걸리는 시간과 합쳐친 증기의 크기가 열유속에 따라 정량적으로 계산되었다.

목차 (Table of Contents)

• Abstract Ⅰ
• Contents Ⅱ
• Nomenclature Ⅴ
• List of Tables Ⅸ
• List of Figures Ⅹ
• 1. Introduction 1
• 2. Literature survey 5
• 2.1 Introduction of ATF cladding 5
• 2.1.1 Concept of ATF 5
• 2.1.2 Oxidation kinetics of ZrSi2 ATF 6
• 2.1.3 Evaluation of heat transfer on ATF 7
• 2.2 Flow boiling heat transfer 9
• 2.2.1 Correlation to predict CHF: Haramura and Y. Katto 9
• 2.2.2 Critical heat flux and liquid inflow rate 10
• 2.2.3 Surface roughness and CHF 13
• 2.2.4 Bubble residence time and dry-out area 13
• 2.3 Boiling experiment on microporous surface 17
• 2.3.1 Effect of particle size on pool boiling critical heat flux 17
• 2.3.2 Effect of particle size on flow boiling critical heat flux 18
• 2.4 Wicking performance in porous media 18
• 2.4.1 Relationship between liquid rise height and time 18
• 2.4.2 Force balance affecting liquid rise in porous media 20
• 2.4.3 Effect of particle size 22
• 2.4.4 Effect of deposition porosity 22
• 2.4.5 Permeability of porous media 23
• 2.4.6 Hydraulic resistance 24
• 2.5 Electrophoretic deposition 25
• 2.5.1 Effect of applied voltage on particle size of deposit 25
• 2.5.2 Relationship between deposition time and thickness 25
• 2.6 Surface wettability and bubble dynamics 27
• 2.6.1 Contact angle and departure diameter 27
• 2.6.2 Disappearance of a single bubble on hydrophilic surface 27
• 3. Surface preparation and characterization 30
• 3.1 Surface preparation 30
• 3.1.1 Deposition of ZrSi2 PVD coating on Zircaloy-4 30
• 3.1.2 Electrophoretic deposition of ZrSi2 powders on ZrSi2 PVD coated Zry-4 35
• 3.2 Characterization of surface morphology 39
• 3.1.1 Measurement of particle size 39
• 3.1.2 Measurement of deposition thickness 40
• 3.3 Wicking performance evaluation 43
• 3.3.1 Wicking experiment 43
• 3.3.2 Experimental results 45
• 3.3.3 Modeling of liquid rise height 48
• 3.3.4 Comparison of the model to the experiment 49
• 4. Flow boiling experiment on Zry-4, ZrSi-Zry and EPD coated ZrSi- Zry 51
• 4.1 Flow boiling experimental facility 51
• 4.1.1 Heater preparation 51 4.1.2 Flow boiling loop and design of test section 52
• 4.1.3 Experimental procedure of flow boiling experiment 58
• 4.1.4 Data and uncertainty analysis 59
• 4.1.5 Visualization method 60
• 4.2 Results and discussion 64
• 4.2.1 Effect of ZrSi2 PVD coating on flow boiling performance of Zry-4 64
• 4.2.2 Flow boiling performance of EPD ZrSi-Zry 66
• 4.2.3 Effect of mass flux 73
• 4.2.4 Visualization on ZrSi-Zry and EPD coated ZrSi-Zry 75
• 5. Summary and Conclusions 81