U.C. Berkeley Per F. Peterson, Christophe Debonnel, Philippe Bardet, Grant Fukuda Department of Nuclear Engineering University of California, Berkeley 2004 International Symposium on Heavy Ion Fusion June 7-11, 2004 HIF Chamber Phenomena and Design

U.C. Berkeley Outline: Thick liquids can replace fusion materials questions with fluid mechanics questions The scaling basis for understanding and predicting thick-liquid IFE chamber performance Robust Point Design 2002 –RPD liquid geometries »Cylindrical jets »Porous slabs »Beam-tube vortices Vortex flows Related work with molten salts in fission energy

U.C. Berkeley IFE system phenomena cluster into distinct time scales Nanosecond IFE Phenomena –Driver energy deposition and capsule drive (~30 ns) –Target x-ray/debris/neutron emission/deposition (~100 ns) Microsecond IFE Phenomena –X-ray ablation and impulse loading (~1  s) –Debris venting and impulse loading (~100  s) –Isochoric-heating pressure relaxation in liquid (~30  s) Millisecond IFE Phenomena –Liquid shock propagation and momentum redistribution (~50 ms) –Pocket regeneration and droplet clearing (~100 ms) –Debris condensation on droplet sprays (~100 ms) Quasi-steady IFE Phenomena –Structure response to startup heating (~1 to 10 4 s) –Chemistry-tritium control/target fabrication/safety ( s) –Corrosion/erosion of chamber structures (10 8 sec) Principal focus for IFE Technology R&D...

U.C. Berkeley The HIF Robust Point Design provides the first demonstration of an integrated HIF chamber design

U.C. Berkeley Flibe x-ray ablation experiments on “Z” can be compared to simpler materials with known EOS’s (LiF, Li metal) LiF has been used as a non-toxic, well- characterized surrogate for flibe in recent experiments –Experiments at 41 J/cm 2 match expected wetted wall fluences »Koyo (laser chamber) »Osiris (heavy-ion chamber) –Sesame EOS is available for LiF »Gives impulse prediction 10% less than ideal-gas EOS –UCB/LANL predicted 2.8  m ablation matches  m measured with LiF »Greater ablation, 4.2  m, is predicted for flibe; will be confirmed in upcoming tests Li metal has been tested at higher fluences (~1000 J/cm 2 ) under DP programs –Time-resolved diagnostics required due to sample destruction –IFE samples can be treated with same approach as DP effects testing work Cast and diced Flibe disk being handled in glovebox 14 mm 5 mm LiF sample exposed to 41 J/cm 2 shows clear ablation step 0.4 mm Microsecond phenomena

U.C. Berkeley Flibe vapor condensation is studied with plasma guns Millisecond phenomena

U.C. Berkeley Scaled water experiments have demonstrated the capability to form the jets used in RPD-2002 Re = 100,000 High-Re Cylindrical Jets Vortex Layers for Beam Tubes Oscillating Voided Liquid Slabs UCB Millisecond phenomena

U.C. Berkeley Navier-Stokes governs liquid hydraulics phenomena Major simplifications: No EOS, No energy equation No MHD A scaled system behaves identically if initial conditions and St, Re, Fr, I*, and We are matched... Millisecond phenomena

U.C. Berkeley Penreco® Drakesol® 260 AT light mineral oil allows molten salt scaled experiments with low distortion Flibe at 600°CFlibe at 900°C Oil Temperature110°C165°C Length-ScaleL s /L p Velocity-ScaleU s /U p Δ T-Scale ΔTs/ΔTpΔTs/ΔTp Reynolds NumberRe s /Re p 11 Froude NumberFr s /Fr p 11 Weber NumberWe s /We p Prandtl NumberPr s /Pr p 11 Rayleigh NumberRa s /Ra p 11 Nusselt NumberNu s /Nu p 11 Pumping PowerQp s /Qp p Heating PowerQh s /Qh p Adjustable Parameters Millisecond phenomena

U.C. Berkeley UCB is now doing detailed experimental measurements of turbulence and surface topology in vortex tubes Millisecond phenomena

U.C. Berkeley Particle image velocimetry is providing detailed velocity and turbulence information Ar CW laser allows visualization of micron particles Water has been replaced by Mineral Oil for improved visualization Evidence for intense turbulence at small length scales –crossing streaks in 1000 µs frame suggests eddy frequencies in the kilohertz range 200 µs exposure time1000 µs exposure time If surface-renewal frequency is 1 kHz, 2MW/m 2 is possible with a surface temperature 50°C greater than bulk temperature Millisecond phenomena

U.C. Berkeley UCB has begun studies of combined blowing and suction to keep liquid layers attached to large, concave surfaces Blowing is generated using patterns of small holes in the wall, supplied by a pressurized plenum Suction rate depends on layer velocity, surface radius of curvature, and layer thickness –Layer thickness adjusts itself to keep injection and suction flow rates equal Both injection and suction nozzles are protected by the liquid layer Millisecond phenomena

U.C. Berkeley Modular solenoid HIF chamber could potentially use a large-scale vortex flow Issues: –Using injection and suction to maintain vortex flow on substrate with non-uniform radius –Response of liquid layer to x-ray ablation (surface waves, substrate stresses, droplet ejection) –Effects of turbulent surface renewal on surface temperature and condensation Vortex generation has been demonstrated experimentally Millisecond phenomena

U.C. Berkeley A simple device was constructed to provide proof of principal A test device was fabricated from a short segment of cylindrical pipe (22.5-cm diameter) Eight pressurized plenums provided blowing flow Perforations between injection plenums provided suction –A suction = 2A injection End walls produced modest non-ideality Millisecond phenomena

U.C. Berkeley Liquid accumulated during startup can be cleared t = 2.0 sec t = 7.0 sec t = 14.0 sec The first viability issue for large-vortex flows is removing excess liquid during startup –UCB experiments demonstrate that this can be done by providing sufficient suction area After startup, flow dumps on suction drains can be closed, and pressure recovery can be achieved –reduce pumping power –increase layer thickness stable layer established Millisecond phenomena

U.C. Berkeley Now a new large vortex experiment is under construction Uses precision fabrication of injection and suction holes Test stand now under trials

U.C. Berkeley UCB is studying the injection/suction scheme for complex geometries Chamber volume: 80m 3 Liquid volume: 28m 3 Open fraction of solid angle: 2.4% Millisecond phenomena

U.C. Berkeley NGNP “Artist’s Conception” The Next Generation Nuclear Plant (NGNP) provides opportunities to develop molten salt technology Molten salt heat transfer loop? Fusion Overlaps: Tritium management High-temperature materials High efficiency helium gas-cycle power conversion

U.C. Berkeley UCB has completed a pre-conceptual design study for a MCGC power conversion system Physical arrangement based on the GT- MHR PCU (vessels are ~ 30 m high) Components fit in four pressure vessels Pre-conceptual design allows comparison of “molten coolant gas cycle (MCGC)” versus gas- cooled reactor power conversion –Based on GT-MHR PCU design –Includes detailed calculations for MS-to-He heat exchangers Results for high-temperature design –2400 MW(t) –900°C turbine inlet temp. –54% thermal efficiency –1300 MW(e) Power density comparison –GT-MHR: 230 kW(e)/m 3 –MCGC: 360 kW(e)/m 3 –Additional MCGC savings expected due to non-nuclear grade turbine building H. Zhao and P.F. Peterson, “A Reference 2400 MW(t) Power Conversion System Point Design for Molten-Salt Cooled Fission and Fusion Energy Systems,” Report UCBTH (Rev. B), Jan. 10, Quasi-steady phenomena

U.C. Berkeley A scaled comparison of the 1380 MWe ABWR turbine building and ~1300 MWe MCGC equipment MCGC turbine building must also contain crane, turbine lay- down space, compressed gas storage, and cooling water circulation equipment MCGC requires ~1100 MWt of cooling water capacity, compared to 2800 MWt for ABWR The MCGC can likely achieve a substantial reduction of the turbine building volume ABWR He-MCGC Quasi-steady phenomena

U.C. Berkeley Conclusions RPD-2002 provided the first integrated chamber design for an IFE system Assisted pinch transport chambers are small extrapolations from current HIF chamber designs Vortex flows are interesting and have substantial promise –Potential for very high surface heat fluxes –Issues: »droplet ejection from surface »effects of ablation impulse loading »control of flow for complex geometries The Next Generation Nuclear Plant will advance and demonstrate key fusion chamber technologies –advanced materials –molten salt heat transfer fluids »materials compatibility »target debris recovery –helium Brayton cycle power conversion –tritium safety and management