Thermal-hydraulic Characteristics of IFMIF Liquid Lithium Target JAERI Mizuho IDA, Hideo NAKAMURA, Hiroshi NAKAMURA, Hiroo NAKAMURA, Koichiro EZATO and Hiroshi TAKEUCHI ISFNT-6 April 8-12, 2002, San Diego, USA MEX.INV.3

Other IFMIF Presentations Oral April 11 afternoon, Parallel Session-6 (NSD.INV.7) H. Matsui et al. (NSD.INV.8) V. Heinzel et al. Poster April 10 afternoon, Poster Session 3 (MEX.POS.22) E. Maki et al. (MEX.POS.33) U. Fischer et al April 11 afternoon, Poster Session 5 (MAT.POS.29 ) T. Sakurai et al.

Historical Ukiyo-e on Flow Instability

Contents 1. D-Li Neutron Source 2. Requirements of IFMIF Target 3. Thermal-hydraulic Analysis 4. Simulating Experiments by Water 5. Selection of Target Parameters 6. Conclusions

Requirements of Neutron Source for Development of Fusion Materials 14MeV neutron 14MeV neutron Neutron intensity Neutron intensity dpa dpa (20dpa/year, 2MW/m 2 ) (20dpa/year, 2MW/m 2 ) He production/damage He production/damage ~10appm/dpa ~10appm/dpa Irradiation volume Irradiation volume 500cc 500cc (LAF steel, V-alloy, SiC/SiC) (LAF steel, V-alloy, SiC/SiC) D-Li neutron source has been selected Fusion Reactor D-Li (IFMIF) Spallation (LASREF) Neutron Flux (n/m 2 /s/Lethargy) HFIR FBR Neutron Energy (MeV) Spallatio n (5MW, 20%- availability) Fission Reactor Fusion Reactor IFMIF Irradiation Damage (dpa/y) He Production (appm/y)

Concept of D-Li Neutron Source High-speed liquid Li flow along concave back-wall is selected as Li target to handle high heat load (1GW/m 2 ) of 10MW D + beams. D + Accelerator Liquid Li Target Li Flow Specimen Neutron (1x10 17 n/s) Li Free Surface HX EMP Injector D + Beam(10MW) Vacuum Pa Concave Back-wall to Increase Boiling Point beyond 340 by Centrifugal Force

Concave back-wall Concave back-wall Target width : 10cm Target width : 10cm to cover D + beam for to cover D + beam for 2MW/m 2 10cc 2MW/m 2 10cc Nozzle shape Nozzle shape determined by repeated determined by repeated skewing from a solution skewing from a solution based on potential flow based on potential flow Stability of free surface Stability of free surface was examined without beam was examined without beam Liquid Li Target in FMIT Basic concept was tested in FMIT in Issue is optimization of nozzle design to avoid flow separation. Exit W 10cm T 1.9cm Neutron Li Flow D + Beam 3cm x 1cm 3.5MW TARGET MARK-II (USA)

IFMIF target features : High power handling of ~10MW High power handling of ~10MW Long and wide free surface Long and wide free surface Nozzle to achieve high flow rate > 100L/s Nozzle to achieve high flow rate > 100L/s Comparison of Free Surfaces Beam Footprint FMIT x 1cm (FWHM) 10cm 33L/ s 2cm Free Surface IFMIF x 5cm Requirement : High- contraction nozzle >100L/s 15cm Flow 26cm Free Surface Beam Footprint

Stable Generation of High-speed, Free-surface Flow Power Handling without Boiling ( 10MW) Thermal- hydraulic Analyses Water Experiments Requirements for IFMIF Target on Analysis and Experiments Li Flow D Beam Item to be verified : Surface deviation < 1mm Design Issues : Flow velocity Back-wall radius Jet thickness Nozzle shape (High contraction)

Calculation code : FLOW-3D Viscosity estimation : k- turbulent model Mesh size : 0.2mm x 1mm Average velocity (U 0 ) : 10, 20m/s Back-wall radius (R W ) : 100, 250, 1000mm Jet thickness : 25mm Inlet temperature : 250 Inlet temperature : 250 Thermal-hydraulic Analysis

Calculation Model 50mm Temperature was calculated using input data of beam penetration. Li Flow D + Beam Free Surface Li Flow Back-wall Heated Region Li Region (t=0) Empty Region (t=0) Energy Deposition Profile Back Wall Free Surface Depth from Surface (mm) Energy Deposition (GW/A m) 40MeV D + Li ( =0.5MeV)

Calculated Temperature & Pressure (Case : U 0 =20m/s, R W =250mm) Depth from Surface (mm) Pressure ( kPa ) Centrifugal Force ~160G Max. temperature is given at lower edge of beam. Pressure increases with depth by centrifugal force. Boiling Point= logP(Pa) ( C, JSME, Engineering data of heat transfer, Edit.4) Beam Height (50mm) Flow Free Surface

Distribution of Li Temperature, Boiling Point and Boiling Margin Velocity of 20m/s gives enough margin. Velocity of 20m/s gives enough margin. Spatial margin > 3mm on back-wall side. Spatial margin > 3mm on back-wall side Depth (mm) Boiling Point R W =100 mm 1000 Li C 280 C 408 C Temperatures Distribution in Li Flow (U 0 =20m/s) 3mm 712 C Temperature ( C) Average Velocity : U 0 (m/s) Surface Temperature ( C) Boiling Point at Free Surface Velocity Dependence on Surface Temperature 30 C40 C T= 61 C 54 C

Required Nozzle Feature : Required Nozzle Feature : - High contraction ratio of 10 for 20m/s, 133L/s flow - High contraction ratio of 10 for 20m/s, 133L/s flow - Short nozzle length for thin boundary layer - Short nozzle length for thin boundary layer Separation was expected at 1-step high- contraction. Separation was expected at 1-step high- contraction. Development of New Nozzle New nozzle was required for high- speed, high-contraction flow without separation. Flow Separation Thickening Jet TARGET MARK-I (USA) 1-stepContraction (FMIT Type) NoSeparation Boundary Layer < 1mm Trans. Velocity < 0.1m/s NewNozzle TARGET ISTC (Russia)

Effectiveness of 2-step nozzle on high- contraction flow was predicted by simulation. Comparison on 2 Types Contraction 2-Step Nozzle 1-Step Nozzle Y 20m/s 0 1cm 10cm AB C A 2m/s Y 39.6cm 36.6cm 2m/s < 0.1m/s within short length Increasing jet thickness A B A Transverse Component Uy (m/s) Y (cm) Wall Center Line Boundary layer ~1mm at A Wall Center Line Transverse Component Uy (m/s) Y (cm) B 0.1m/s B 3.6cm 0 10cm 3.6cm

Double Reducer Nozzle IFMIF nozzle was designed by 2-step contraction method to achieve required flow at nozzle exit. Calculated Values at Exit : Transverse component ~ 0.03m/s Boundary layer ~ 0.6mm 2.5cm 2m/s 20m/s Connection Point 39cm 30 (cm) Nozzle-1 (Contraction ratio = 4) Nozzle-2 (2.5) cm 6.25cm

Objectives : To verify stable flow generation by To verify stable flow generation by double reducer nozzle double reducer nozzle To clarify effect of nozzle wall To clarify effect of nozzle wall roughness on surface waves roughness on surface waves Advantages of Water Experiment : Well simulation of Li flow with fitting Well simulation of Li flow with fitting Reynolds number Reynolds number Convenience at velocity measurement Convenience at velocity measurement Simulating Experiments by Water

Effectiveness of Simulation by Water Flow Parameters at Velocity of 20m/s Water experiments can simulate Li flows with same kinematic viscosity and Reynolds number.

Water experiments with horizontal, straight wall are expected to well simulate surface of Li flow with vertical, concave wall. Wave amplitude (g+U 0 2 /R W + K 2 / ) -0.5 (g+U 0 2 /R W + K 2 / ) -0.5 ~ ( K 2 / ) -0.5 : Surface tension : Surface tension : Density : Density K : Wave number (2 / ~2 /1mm) (2 / ~2 /1mm) Effect of Test Section Arrangement Effect of Forces on Surface Wave Stability U0U0 RWRWRWRW

Experimental Setup 10 10cm Surface Observation (High-speed Camera) Wall Roughness 6.3, 100 m Free Surface Double Reducer Nozzle 15cm 1cm Velocity Measurement (Laser Doppler Velocimeter) X Y VXVX VYVY Wave Height Measurement 20m/s Laser Beam and Position Sensitive Detector

3D View of Test Section (Test Operation without Measuring Devise) Double Reducer Nozzle Flow Surface 10cm 1cm

Surface Observation Double reducer nozzle generates stable flows with surface deviation < 1mm. Roughness : 100 m 50mm Flow Rough (100 m) wall nozzle generated waves in IFMIF velocity range of m/s U 0 =5m/sU 0 =10m/sU 0 =20m/s Roughness : 6.3 m Flow 50mm Wave Height ~0.2mm (r.m.s.)

Characteristic Change of Boundary Layer at Nozzle Exit Change of boundary layer from laminar to turbulent occurred at U 0 >5m/s in case of rough (100 m) wall nozzle. Velocity : U (m/S) Distance from Wall : y (mm) U 0 =20m/s 5m/s 10m/s Average Velocity : U 0 (m/s) Laminar Flow ( U ) Momentum Thickness (mm) Momentum thickness : =(U/U 0 (1- U/U 0 )dy Wall Roughness 6.3 m Wall Roughness 6.3 m 100 m

Double Reducer Nozzle (Roughness : 6.3 m) Concave Back-wall (R W =25cm) Li Flow ( U 0 =10-20m/s T 25mm x W 260mm ) D + Beams Quench Tank Pump Shielding Wall Selection of Target Parameters

3-D view of IFMIF Li loop Quench Tank Deuteron Beam Li Target EM Pump HX(Li / Organic Oil) Dump Tank HX(Organic Oil / Water) Purification System 133 L/s

3-D View of IFMIF Irradiation Test Cell D + Accelerators 40MeV 125mA x 2 beams m Li Loop Li Target

Conclusions 1) Thermal-hydraulic analysis has been done to define target specifications. done to define target specifications. 2) Water experiment has validated a stable high speed flow with a double reducer high speed flow with a double reducer nozzle and defined nozzle roughness. nozzle and defined nozzle roughness. Based on these results, thermal- hydraulic stability of Li target has been established.