falling liquid film flow along cascade- type first wall of laser-fusion reactor t. kunugi, t. nakai,...
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Falling Liquid Film Flow along Cascade-type First Wall of Laser-Fusion Reactor
T. Kunugi, T. Nakai, Z. Kawara
Department of Nuclear Engineering
Kyoto University, Japan
Collaborated with T. Norimatsu
ILE Osaka University, JapanLijiang river10.24.2007
Design specification of KOYO-Fast
– Net output 1200 MWe (300 MWe x 4)
– Reactor module net output 300 MWe
– Laser energy 1.2MJ
– Target gain 167
– Fusion pulse out put 200 MJ – Reactor pulse rep-rate 4 Hz
– Reactor module fusion outputr 800 MWth
– Blanket energy multiplication 1.13
– Reactor thermal output 904 MWth
– Total plant thermal output 3616 MWth (904 MWth x 4 )
– Thermal electric efficiency 42 % ( LiPb Temperature ~500 C)
– Total electric output 1519 MWe
– laser efficiency 8.5% (implosion) , 5% (heating)
– Laser pulse rep-rat 16 Hz
– Laser recirculating power 240 MWe ( 1.2 MJ x 16 Hz / 0.08)
– Net plant out put power 1200 MWe(1519MWe - 240MWe - 79MWe Aux.)
– Total plant efficiency 33.2 %( 1200 MWe/ 3616 MWth)
Basic design concept for PbLi chamber
1) No pressurized pipe or vessel in the chamber for avoiding high pressure in chamber in accidents, and for achieving simple maintenance and long life use.
2) Free surface fast cooling using divergent flow thorough from bulk flow (small holes or slit structure ⇒ Cascade-typed FW)
3) Feritic steal is used for cylindrical vessel and upper dome cover vessel
4) SiC/SiC is used as separate wall without pressure bulkhead
5) Adjusting holes or slits on the separate to control divergent flow for stabilizing and fast cooling free surface (200ms for renewal of FW)
6) Two layers PbLi blankets (~20 cm for free surface first wall and ~80 cm for blanket) and ~45cm graphite neutron reflector.
PbLiC PbLi
SiC wall
Feritic Steal
50 mm 450 mm 800 mm 200 mm
F3 F2 F1Graphite 45 cm
SiC/SiC porous wall container
LiPb Flow
Ablation control by FW inclinationFree-surface flow control by cascade passage
Cascade-typed FW Concept
The coolant flows downward along FW→ into reservoir behind FW→ flows laterally to a slit→ goes upward into the slit→ past the exit of the slit→ some of the overflowed coolant forms a falling liquid-film flow
Laser fusion modular power plant "KOYO" design, which has four reactor chambers driven by one laser system, was proposed .
KOYO laser-fusion reactor
Cascade typed Liquid wall
KOYO reactor cross-sectional viewLiPb flow inlet (280-300oC)
LiPb flow outlet(480-500oC)
Reflector
Gas coolant outlet
Gas coolant inlet
Thermal flow of KOYO-F( One module)
SGTurbin
500℃
300℃300℃
50MW
210MW
70MW
70MW
240MW
80MW
80MW
500℃
F2+F3 (80cm)12.84 ton/s
Average flow 7.8 cm/s
F1 (20cm)8.56 ton/s
Average flow 24.3 cm/s
Flow rate 21.4 ton /s
904MW
Watercycle
Chamber
LiPb cycle
200MJ/shot x 4Hz
300 MWe
ther-elec=30%
30cm
Cascade-typed Liquid Wall
Redesigned Cascade-typed liquid wall
Some flow resistances to maintain the surface shape.
Primary design proposal
The fluid covering the surface heated at the upper unit does not enter the backside of FW.
As a result, the fluid does not mix well, and the surface temperature of the first wall is continuously rising.
The height of the first wall of each unit is set to 30cm corresponding to the surface renewal time: 4 Hz laser repetition
Difficult to keep thickness of liquid film
Mixing is not sufficiency
Surface temperaturerises
Making space between reservoir units ⇒ static pressure drop for each units could be kept constant
Proof-of-principle experiment
• The flow visualization experiment was performed as a POP experiment.
• In order to examine the performance of the new cascade-typed FW concept, numerical simulation was performed using STREAM code with k- turbulent model.
Similarity Law and Flow Condition of Visualization Test
In the actual reactor, Li17Pb83 will be working fluid and SiC/SiC composite
material will be used for the first wall. In this case, the wall surface might have a lower wettability. In the present experiment, we used the acrylic resin board as the FW because of its lower wettability.
The major concern of this experiment is to know the stability feature of the liquid film flow, therefore, the Weber number is the key parameter ,where is based on the film thickness , velocity , density , and surface tension coefficient .
According to the similarity law, we can estimate the flow velocity ratio.
2We u
2
1water LiPb Water Water
LiPb Water LiPb LiPb
We u
We u
1.21Water
LiPb
u
u
Water : =7.275×10-2[N/m] =9.98×102 [kg/m3]
Li17Pb83 : =4.80×10-1[N/m] =9.6×103 [kg/m3]
u
Experimental Setup
PumpTank
Drain
Tank
Drain
Valve
Valve FlowMeter
FlowMeter
Valve
Valve
Pump
Electric Balance
Flow Condition
Re:4800~9600
T=17.5[ 。 c]
Experimental results
The average flow velocity is 1.75 times (14 l/min) of Weber number coincident condition (8.0 l/min) with the actual reactor.
Liquid Film Flow
OverflowAt the overflow regions, there
are many small waves. The liquid-droplet generation
from the liquid surface and the large wave on the liquid-film surface were not observed.
These small waves might trigger free surface unstable motion of the falling liquid-film flow on FW.
Break-up of FW liquid film
The averaged flow velocity is 0.75 times (6.0 l/min) of Weber number coincident condition (8.0 l/min) with an actual reactor condition.
Film Break-up
Film Break-up
Numerical Simulation We performed the two-dimensional thermo-fluid simulation by using the MARS
function of the STREAM (commercial 3-D thermo- fluid code, Software Cradle Co. Ltd. in Japan).
Liquid Film Flow
Flow
Direction
Experiment
Overflow
NumericalSimulation
Comparison between Exp. & CFD
Computational Conditions
Mesh:782800
Fluid1:Air Fluid2:Water
Material:Acrylic resin
Re=5806, T=20.0[ 。 c]
Experiment
3mm3mm
Numerical Simulation
Conclusions• We proposed the cascade typed liquid wall concept, and
conducted the POP experiments and the numerical simulation (CFD) based on the consideration of the similarity law.
• The CFD result qualitatively agreed with the POP flow visualization experiment, so that the cascade-typed liquid film system will be realized.
• We also confirmed that the stable liquid film with sufficient thickness (liquid wall covering the first wall) could be naturally formed.
Therefore, it seems that this liquid wall concept might be possible to apply to the real reactor.