Vapor Condensation Study Vapor Condensation Study for HIF Liquid Chambersfor HIF Liquid Chambers

byby

Patrick CalderoniPatrick CalderoniUCLA – Fusion Engineering SciencesUCLA – Fusion Engineering Sciences

1515thth International Symposium on Heavy Ion Inertial Fusion International Symposium on Heavy Ion Inertial FusionPrinceton Plasma Physics LaboratoryPrinceton Plasma Physics Laboratory

Princeton, NJ, June 7-11, 2004Princeton, NJ, June 7-11, 2004

Experimental research work major accomplishmentsExperimental research work major accomplishments

Developed an innovative and inexpensive scheme to generate flibe Developed an innovative and inexpensive scheme to generate flibe vapor in conditions relevant to fusion technology design studies vapor in conditions relevant to fusion technology design studies involving a liquid protection scheme (HIF, IFE, Z-pinch)involving a liquid protection scheme (HIF, IFE, Z-pinch)

Measured flibe vapor clearing rates suggest that high Measured flibe vapor clearing rates suggest that high repetition rates in HIF power plants are feasible provided repetition rates in HIF power plants are feasible provided that high purity of the molten salt is ensuredthat high purity of the molten salt is ensured

Found that for flow conditions characterized by high kinetic energy Found that for flow conditions characterized by high kinetic energy flibe vapor condensation is partially inhibited on metal surfaces flibe vapor condensation is partially inhibited on metal surfaces perpendicular to the main component of the vapor velocityperpendicular to the main component of the vapor velocity

HYLIFE-II parameters relevant to vapor condensation studies (Moir, 1994)HYLIFE-II parameters relevant to vapor condensation studies (Moir, 1994)

Total mass generated from x-ray absorptionTotal mass generated from x-ray absorptionon liquid surfaces: 14 kgon liquid surfaces: 14 kg

Total volume for vapor expansion: 280 mTotal volume for vapor expansion: 280 m33

Initial n: Initial n: 0.9x100.9x101818 #/cm #/cm33 (0.5x10(0.5x101818 #/cm #/cm33))Recovered n:Recovered n: 3x103x101313 #/cm #/cm33 (2x10 (2x101515 #/cm #/cm33))

Energy from explosion coupled with x-Energy from explosion coupled with x-ray and debris: 110 MJray and debris: 110 MJ

Energy density: Energy density: 7.85 kJ/g7.85 kJ/g (7.5 kJ/g) (7.5 kJ/g)

Structural surface for condensation: 40 mStructural surface for condensation: 40 m22

Surface from droplet injection: 1060 mSurface from droplet injection: 1060 m22

Ratio of surface area per unit mass of Ratio of surface area per unit mass of generated vapor: generated vapor: 785 cm785 cm22/g/g (4300 cm2/g (4300 cm2/g for LiF andfor LiF and 10205 cm 10205 cm22/g /g for flibefor flibe))

Droplet spray injection design:Droplet spray injection design:T = 843 KT = 843 KSpray flow rate = 2.4x103 kg/s Spray flow rate = 2.4x103 kg/s (1.6% of main flow rate)(1.6% of main flow rate)

Experimental approach: Experimental approach: staged design of vapor generation facilitystaged design of vapor generation facility

Characterization of superheated vapor source in comparison Characterization of superheated vapor source in comparison to other experiments using electro-thermal sourcesto other experiments using electro-thermal sources

Diagnostic developmentDiagnostic development

Limited availability, cost and toxicity of materials: Limited availability, cost and toxicity of materials: demonstrate efficiency, repeatability and reliability before using flibedemonstrate efficiency, repeatability and reliability before using flibe

Reduce residual non-condensable gases Reduce residual non-condensable gases

Stage 1: Lexan withStage 1: Lexan withArgon background (1 Argon background (1 Torr) Torr)

time: 0time: 0

time: 820 time: 820 s s

time: 1640 time: 1640 s s

Typical vapor parameters in the source : Typical vapor parameters in the source :

n = 10n = 101919 - 10 - 102020 # / cm # / cm33

T = 1-3 eVT = 1-3 eV

Argon background is ionized (10-100 ns) Argon background is ionized (10-100 ns) forming initial plasma column forming initial plasma column

Injected electrical power radiated to Injected electrical power radiated to surface, ablates material of interestsurface, ablates material of interest

Pressure gradient drives injection, Pressure gradient drives injection, ablation balances axial mass loss ablation balances axial mass loss

Energy stored in cap banks maintains Energy stored in cap banks maintains plasma at 1-3 eV for 100 micros plasma at 1-3 eV for 100 micros

expansion chamberexpansion chamber

volume: 4000 cmvolume: 4000 cm33

surface area: 1720 cmsurface area: 1720 cm22

Stage 2: Teflon and LiF in vacuum chamberStage 2: Teflon and LiF in vacuum chamber

time of flight view portstime of flight view ports

vaporvaporsourcesource

current incurrent in

current outcurrent out

Cathode: ¼’’ D Cathode: ¼’’ D 10’’ long W rod10’’ long W rod

Flibe Flibe liquid liquid pool: pool: 1.6 cm1.6 cm33 volume volume

Anode: Nickel crucible Anode: Nickel crucible with embedded high with embedded high density cartridge heaterdensity cartridge heater

Stage 3: Flibe Stage 3: Flibe vapor generationvapor generation

SS witness plates for SS witness plates for SEM and EDX analysisSEM and EDX analysis

Pressure sensor, water Pressure sensor, water cooled (Tmax = 260 C)cooled (Tmax = 260 C)

Total length: 34 cmTotal length: 34 cm

Expansion volume: 400 cmExpansion volume: 400 cm33

Surface area: 420 cmSurface area: 420 cm22

Insulation: high-vacuum Insulation: high-vacuum ceramic breaksceramic breaks

High-speed camera frames sequence from flibe discharge High-speed camera frames sequence from flibe discharge

100 100 ss

120 120 ss

140 140 ss

160 160 ss

180 180 ss

200 200 ss

220 220 ss

240 240 ss

260 260 ss

280 280 ss

300 300 ss

320 320 ss

Pressure data and residual gas composition: flibePressure data and residual gas composition: flibe

tt300300 = 4.27 ms (4.22 ms at 1.44 kJ) = 4.27 ms (4.22 ms at 1.44 kJ)

tt500500 = 6.58 ms = 6.58 ms

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96-81.0x10

-71.3x10

-72.5x10

-73.7x10

-74.9x10

-76.0x10

-77.2x10

-78.4x10

-79.6x10

-61.1x10

-61.2x10

Atomic Mass Units

TorrRGA Analog Scan Oct 14, 2003 05:03:48 PM

HH22

28,16 amu: 28,16 amu: hydrocarbonshydrocarbons

condensation is condensation is completed in 30 ms: completed in 30 ms: no residual BeFno residual BeF22

traces at 47 amutraces at 47 amu

44 amu:44 amu:COCO22

300 C300 C

500 C500 C

p(T) p(T) → n(T) → n(T) assumes assumes thermodynamic thermodynamic equilibrium with a equilibrium with a liquid surfaceliquid surface

Comparison with HYLIFE-II chamber clearing modelsComparison with HYLIFE-II chamber clearing models

n = nn = n00 x e x e-t/T-t/T

nn00 = 0.9x10 = 0.9x101818 #/cm #/cm33

nnendend = 3x10 = 3x101313 #/cm #/cm33

Clearing period for Clearing period for HYLIFE-II = 68 msHYLIFE-II = 68 ms

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49-8-3.2x10

-87.8x10

-71.9x10

-73.0x10

-74.1x10

-75.2x10

-76.3x10

-77.4x10

-78.5x10

-79.6x10

-61.1x10

Torr RGA Analog Scan

00:00 00:06 00:12 00:18 00:24 00:30 00:36 00:42 00:48 00:540

-78.0x10

-61.6x10

-62.4x10

-63.2x10

-64.0x10

-64.8x10

-65.6x10

-66.4x10

-67.2x10

-68.0x10Torr RGA P vs T Scan

H2

BeF2

LiF

CO2

Measured composition of flibe vapors Measured composition of flibe vapors in equilibrium with a liquid surface in equilibrium with a liquid surface

Heating sequence (linear) from 460 C to 700 C (about 30 min)

at 460 C

HH22

hydrocarbonshydrocarbonsCOCO22

BeFBeF22

Additional data: post-analysis of side collecting platesAdditional data: post-analysis of side collecting plates

Collecting plates parallel to the radial direction

300 C300 C 460 C460 C

Film forms during first Film forms during first expansion phase (100 expansion phase (100 s) when vapor velocity s) when vapor velocity is highly directionalis highly directional

Drops condense in the Drops condense in the chamber volume after chamber volume after the velocity has the velocity has become uniform and become uniform and deposit on the liquid deposit on the liquid film without mergingfilm without merging

At low T film is thinner At low T film is thinner and breaks due to quick and breaks due to quick cooling and cooling and solidificationsolidification

Surfaces are gold Surfaces are gold plated for SEM analysisplated for SEM analysis

Additional data: post-analysis of front collecting platesAdditional data: post-analysis of front collecting plates

Collecting plates perpendicular to the radial direction

300 C300 C 460 C460 CFilm condensation Film condensation is inhibited at 300 Cis inhibited at 300 C

At 460 C thin film At 460 C thin film starts at fixed r from starts at fixed r from plate side center plate side center (flow stagnation point)(flow stagnation point)

EDX analysis confirms EDX analysis confirms qualitative resultsqualitative results

Additional data: post-analysis of collecting platesAdditional data: post-analysis of collecting plates

Further evidence Further evidence of volumetric of volumetric condensationcondensation

Evidence of liquid Evidence of liquid displacement by the displacement by the pressure front pressure front generated during the generated during the discharge: large liquid discharge: large liquid drops are entrained in drops are entrained in the flow and deposit the flow and deposit around the crucible and around the crucible and the collecting platesthe collecting plates

300 C300 C 300 C300 C

460 C460 CLarge drop is flibeLarge drop is flibe

sidesideplateplate

frontfrontplateplate

ConclusionConclusion

Condensation rates of flibe vapor in conditions relevant to IFE power plant studies Condensation rates of flibe vapor in conditions relevant to IFE power plant studies have been measured experimentally - Vapor density decays exponentially with a have been measured experimentally - Vapor density decays exponentially with a time constant of 6.58 mstime constant of 6.58 ms in the range between 5x10 in the range between 5x101717 cm cm-3-3 and 2x10 and 2x101515 cm cm-3-3

Extending to Extending to HYLIFE-IIHYLIFE-II expected density cycles the expected density cycles the vapor clearing ratevapor clearing rate is is 68 ms68 ms, compatible with the desired 6 Hz repetition rate, compatible with the desired 6 Hz repetition rate

Data suggest that for flow conditions characterized by high kinetic Data suggest that for flow conditions characterized by high kinetic energy flibe vapor condensation is partially inhibited on surfaces energy flibe vapor condensation is partially inhibited on surfaces normal to the main component of the vapor velocity normal to the main component of the vapor velocity

Control of the impuritiesControl of the impurities dissolved in the molten salt is a fundamental issue for dissolved in the molten salt is a fundamental issue for applications that require recovery of vacuum conditions in the 10applications that require recovery of vacuum conditions in the 101313 #/cm #/cm33 range range

Discharge parametersDischarge parameters

Teflon I and V for 10 and 5 disk configurationTeflon I and V for 10 and 5 disk configuration

LiF I for different energy experimentsLiF I for different energy experiments

I for flibe experimentsI for flibe experiments

HYLIFE-II conceptHYLIFE-II concept

Liquid protection for Inertial Fusion Energy power plant chambers

Thick liquid “pockets” or thin liquid layers shield chamber structures: Thick liquid “pockets” or thin liquid layers shield chamber structures: fluid mechanics questions replace materials questionsfluid mechanics questions replace materials questions

Neutron damages and activation of flowing liquid accumulate only in the short Neutron damages and activation of flowing liquid accumulate only in the short residence period - no blanket replacement required, increases availabilityresidence period - no blanket replacement required, increases availability

The molten salt flibe:The molten salt flibe:

High Tritium Breeding Ratio High Tritium Breeding Ratio

Low electrical conductivity Low electrical conductivity

High neutronic thickness High neutronic thickness

Chemical, radioactive Chemical, radioactive and thermal stability and thermal stability

Limited material availabilityLimited material availability

Uncertain composition and purity level of available material Uncertain composition and purity level of available material

Beryllium safety hazardBeryllium safety hazard

Lack of data on physical and chemical properties Lack of data on physical and chemical properties

For fusion system design:For fusion system design:

For small scale experiments:For small scale experiments:

Flibe composition is a compromise Flibe composition is a compromise between melting temperature (structural between melting temperature (structural costs) and viscosity (pumping cost)costs) and viscosity (pumping cost)

2 LiF + 1 BeF2 2 LiF + 1 BeF2 in molesin moles

0 1000 2000 3000 4000 5000 6000500 1500 2500 3500 4500 5500 6500

Temperature [C]

1.00E -005

1.00E -004

1.00E -003

1.00E -002

1.00E -001

1.00E +000

1.00E +001

1.00E +002

1.00E +003

1.00E +004

1.00E +005

1.00E +006

1.00E +007

1.00E +008

1.00E +009

1.00E +010

Va

po

r p

res

su

re [

Pa

]

Flibevapor

pressure

In equilibrium with the liquid In equilibrium with the liquid at 600 C, flibe vapor pressure at 600 C, flibe vapor pressure is about 1 mTorr, is about 1 mTorr, corresponding to a density of corresponding to a density of 1.2 101.2 101313 cm cm-3-3

Flibe low vapor pressure is Flibe low vapor pressure is a key property for efficient a key property for efficient driver coupling with the driver coupling with the fusion target at high fusion target at high repetition ratesrepetition rates

Reference dataReference data for flibe for flibe vapors are based on the vapors are based on the assumption of assumption of thermodynamic equilibrium at thermodynamic equilibrium at the liquid interface the liquid interface and ideal and ideal gas equationgas equation

Weight loss measurements Weight loss measurements

18 experimental runs 18 experimental runs with 10 Teflon disks with 10 Teflon disks as sleeve materialas sleeve material

1 with 5 disks1 with 5 disks

5.76 kJ5.76 kJ

2.54 kJ2.54 kJ

Volume ratio Volume ratio between source between source and chamber: 1:25and chamber: 1:25

Evidence of C soot Evidence of C soot deposition on source deposition on source componentcomponent

Pressure data: Lexan and TeflonPressure data: Lexan and TeflonDynamic sensor Dynamic sensor mounted at mounted at center of back center of back plate (high noise plate (high noise from vibration)from vibration)

Teflon = CFTeflon = CF22 chain chain

Residual gases (20-70 Torr):Residual gases (20-70 Torr):28 amu (C28 amu (C22HH22 - C - C22HH44 - C - C22HH66))

69 amu (CF69 amu (CF44))

20 amu (HF)20 amu (HF)

about 5 times decayabout 5 times decay

Jet velocity optical Jet velocity optical measurement systemmeasurement system

Diode axis separation:7.62 cmPeak time delay:6 microsecondsEstimated initial vapor velocity:10110 m/s

Jet velocity optical measurement system

Sensor closer to center of chamber sees a second peak in the light, about 2ms after triggering

Peak due to first reflection of the vapor jet at the chamber bottom

Vapor cools and expands in the chamber, emitting front does not reach the upper sensor

Estimated average velocity of vapor in the chamber after first reflection:320 m/s - 4 kV210 m/s - 3 kV

Flibe experiments results

Exponential decay fits data points good

Decay time constant t1 is a measure of the condensation rate

t1 = 4.22 ms

Flibe experiments results

Exponential decay fits data points good

Decay time constant t1 is independent from initial particle

density

t1 = 4.27 ms

Additional data: emission spectroscopyAdditional data: emission spectroscopy

Strong lines from neutral and first ionization state of both lithium and beryllium atoms are present in the spectrum

Be vapors diagnostic development:

• measure at different times the ratio of line intensity of Li I and Li II transitions

•steady-state emission calibration with langmuir probe will associate line ratio with thermodynamic vapor parameters (pressure and density)