1 Scoping the Potential of Mobile Tiles for and IFE Power Plant Lance Snead, Hsin Wang, Jim Kiggans Oak Ridge National Laboratory Igor Sviatoslavsky, Mohamed Sawan,Carol Alpine, Greg Sviatoslavsky University of Wisconsin Presented at the HAPL Meeting PPPL, Princeton, NJ December 12-13, 2006
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1 Scoping the Potential of Mobile Tiles for and IFE Power Plant Lance Snead, Hsin Wang, Jim Kiggans Oak Ridge National Laboratory Igor Sviatoslavsky, Mohamed.
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Scoping the Potential of Mobile Tiles for and IFE Power Plant
Lance Snead, Hsin Wang, Jim Kiggans
Oak Ridge National Laboratory
Igor Sviatoslavsky, Mohamed Sawan,Carol Alpine, Greg Sviatoslavsky
University of Wisconsin
Presented at the HAPL Meeting
PPPL, Princeton, NJ
December 12-13, 2006
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Basic Idea
• Fundamental problem with graphite is solved by limiting residence time of graphite tile in chamber and post-processing tile in vacuum furnace.
-- Post processing restores graphite properties-- Post processing removes tritium-- Erosion mitigated by limiting time in chamber
----> let’s consider recycling the tiles….
• Material and Design: Intermediate quality graphite tile similar to matrix nuclear graphite (good thermal conductivity, very high fracture toughness.)
• Tile rides on rail from top of reactor to bottom, through furnace, inspect, back to the top of the reactor.
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The original twisted biscuit
Top View With Oval RailGraphite + Breeder + Multiplier
Side View: View Face Changes With Twist of Oval Rail
Chamber Support Composed OfTwisting Metallic Oval Rail
It is possible to achieve adequate tritium breeding with the mobile tiles design with proper composition optimization keeping in mind constraints on material content
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Cooling the Tiles is of Paramount Importance
• The target energy in the form of ions, neutrons and x-rays impacts the tiles and is conducted to the back through the graphite.
• At this point the energy has to be transferred to the coolant channel.
• Radiating the energy is not adequate since it causes the front temperature to be excessive (2700 oC).
• A scheme for conducting the energy is shown in the figure. Graphite felt lines the inner channel of the tile facing the target.
• A linkage built into the cooling channels, when engaged applies forces on the the tile and compresses the graphite felt allowing the energy to be conducted to the cooling channel.
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Estimating the Tile Surface Temperature
x-rays Burn ions Debris ionsType of deposit. Exponential Uniform Uniform
Deposit. Depth() 2 10 1
Deposit. Time (ns) 1.4 1100 3800
Fluence (J/cm2) 0.39 2.98 4.0
Max. Temp. (oC) 1330 1400 1600
• Assuming radiation, to transfer the energy from the tile to the coolant channel exceedsdesirable temperatures at the surface. For example, assuming the coolant channel is at 200 oC, the maximum tile surface temperature is ~ 2700 oC. Conduction is needed to transfer heat from tile to the coolant rails.
• Tile temperature is critically dependent on the contact conductance between tile and coolant rails. This tile thermal conductivity and contact conductance can only be guessed at currently, though there are potential engineering improvements which can be considered.
• Graphite felt in the space between the tile and the coolant channel, when compressed, provides a conduction path. Assuming a coolant temperature at 400oC, a conductivity for the graphite felt of 1 W/mK, a thickness of 0.1 cm, resulting temperatures are shown below.
142.52.01.51.00.50.0
1000
1200
1400
1600
1800
2000
2200
2400
Maximum Tile Surface Temperature as a Function of Graphite Felt Conductivity
• Estimation of the thermal contact resistance is a critical path issue for the mobile tiles and will be a strong function of temperature and interfacial pressure
Flux via electrical resistance delivered to mandrel of load frame
Top Specimen 25mm x 5mm diameter
Bottom Specimen 5mm x 5mm diameter
Sample Pair sat atop hemispherical tungsten carbide support
TC for measure of ambient Temperature
• Estimation of the thermal contact resistance is a critical path issue for the mobile tiles will be a strong function of temperature and interfacial pressure
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The cover is place on the furnace and the heating elements placed in the top 4 slots to help induce heat flow. A sapphire widow is placed over the opening to retain heat while allowing for the capture of the thermal image
• System tested at RT, 50, 100, 150, 200 C and 1, 25, 50, 75 MPa
• For these initial runs the top “specimen” was aluminum alloy and the bottom specimen a lower conductivity steel
• Data was taken at RT with and without the sapphire window
• There was a 20 minute interval between heat cycles
• For Example, lets say data was collected at 50 C for the 4 pressures. The furnace would cycle on, and allowed to heat to 100 C (10C/min). Once at 100 C, it was left there for 8 minutes, at which time the flux source was turned on. After 4 minutes, data collection began for the 4 pressures, after which time, the furnace began to heat up to 150 C.
• This continued up to 200 C, till all the data was collected.
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Raw Data w/Curve Fit319 vs Brico @ 50 C Ambient
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48
50
52
54
56
58
60
0 5 10 15
Distance (mm)
Temperature (C)
1 MPa
25 MPa
50 MPa
75 MPa
Series5
Series6
Series7
Series8Flux was determined for both top and bottom specimens using (dT/dx)Kmat’l, then averaged to get Qave.
Qave/dTinterface = TCC (mW/mm2-C)
The linear approximations were obtained using the 5 mm closet to the interface for the top specimen and 3mm for the bottom specimen. The true location of the interface itself (the vertical line) is very subjective and sensitive to the calculation of the interface TCC.
Test System Data
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356 vs Exhaust Seat Mat'l (K=40.1)
0
40
80
120
160
200
240
0 10 20 30 40 50 60 70 80
Pressure (MPa)
TCC (mW/mm2-C)
200°C150°C
100°C
50°C
20°C
Thermal Contact Conductance of Model Al/Steel System
• Additional optimization to the analysis program would be helpful, but system appears ready for application to a mobile tile graphite/metallic interface.
• Hot press powder to ~ 1100 °C (low temperature to avoid vapor hazard)
• Carbon binder will bond powders together under pressure Interior of ORNL Brew hot press
showing graphite die
• Properties and property evolution in-reactor can only be estimated for this graphite-ceramic. Assuming preliminary designs suggest promise, property measurement on prototypic materials will be required.
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next
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Sawicki JNM 1989
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Saeki JNM 81Neutron irradiation to ~3E19 n/cm2, 250-400
Largest TBR achieved with high breeder content / low Li enrichmentAchievable TBR not adequateReplacing FS/Na by SiC/He is not Helpful
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0
20
40
60
80
100
0.1 1 10 100 1000
Time in HFIR Core (hours)
H451 : Tirr
= 430°C
H451 : Tirr
= 710°C
Snead data, recently unpublished
0.2 dpa 2 dpa
Degradation in Thermal Conductivity• For graphite held in the 600-1000°C range, thermal conductivity will slightly degrade and density somewhat. Some recovery during furnace anneal will occur.