Preliminary Neutronics Assessment of Molten Salt Blanket Concepts - - PowerPoint PPT Presentation

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Preliminary Neutronics Assessment of Molten Salt Blanket Concepts

Mohamed Sawan

Fusion Technology Institute University of Wisconsin, Madison, WI

ITER TBM Meeting UCLA

• Feb. 23-25, 2004

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Preliminary Neutronics Assessment

ÿ Three blanket concepts analyzed

• 1. Self-cooled Flinabe blanket (Flinabe/Be/FS)- [SC]
• 2. Dual coolant blanket with Be (Flibe/He/Be/FS)- [DC-Be]
• 3. Dual coolant blanket with Pb (Flibe/He/Pb/FS)- [DC-Pb]

ÿ The FS alloy F82H used as structural material ÿ Same reactor configuration and power loadings used for fair comparison Average reactor neutron wall loading 3.84 MW/m2 Peak neutron wall loading: OB 5.45 MW/m2 , IB 3.61 MW/m2 Average neutron wall loading: OB 4.61 MW/m2 , IB 2.80 MW/m2 ÿ Radial build between FW and VV is 80 cm IB and 95 cm OB ÿ 25 cm thick VV ÿ Water cooled steel VV and shield ÿ TBR has a flat peak in the enrichment range 40-60%. 40% 6Li is used ÿ 1D calculations with IB and OB blankets modeled simultaneously ÿ Several iterations were made to determine the radial build that achieves adequate tritium breeding and shielding for VV and magnet ÿ Larger margins are considered to account for uncertainties resulting from approximations in modeling ÿ Multi-dimensional calculations are to be performed later to accurately model the blanket

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Blanket Radial Build

5 cm 87% Pb 5 cm 60% Be 7 cm 60% Be Multiplier Zone 65 cm OB 40 cm IB 65 cm OB 40 cm IB 50 cm OB 40 cm IB Blanket Thickness DC Flibe/He Pb DC Flibe/He Be SC Flinabe Be

ÿSame TBR can be achieved with a thinner SC OB blanket compared to the DC blanket with large He amount ÿTo achieve the same TBR a smaller Be zone thickness (5 cm) is required in the DC design with Flibe compared to the SC with Flinabe (7 cm) ÿIn the DC design more Pb is needed than Be although the Be is pushed farther from FW by the Flibe poloidal flow channel required to cool it

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Tritium Breeding Potential

ÿIf neutron coverage for the divertor is 10% the overall TBR will be ~1.17 excluding breeding in divertor region. Breeding in divertor zone could add ~0.05 ÿThe blanket design concepts have the potential for achieving tritium self-

• sufficiency. Some design parameters can be adjusted (e.g., multiplier

thickness, blanket thickness, etc) to insure tritium self-suffiency based on calculations with detailed multi-dimensional modeling

0.0 0.5 1.0 1.5

SC DC-Be DC-Pb

Blanket

OB IB

1.296 1.288 1.299 Total 0.897 0.882 0.867 OB 0.399 0.406 0.432 IB DC-Pb DC-Be SC

Local TBR

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Blanket Energy Multiplication

ÿUsing Be yields higher blanket energy multiplication

ß 1.27 for SC blanket with Be ß 1.21 for DC blanket with Be ß 1.13 for DC blanket with Pb

0.0 0.5 1.0 1.5

SC DC-Be DC-Pb

Blanket

1.27 1.27 1.27 1.21 1.13

Blanket Energy Multiplication

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Nuclear Heating in Components

• f Self-Cooled Flinabe Blanket

ÿ Peak nuclear heating values in OB blanket

• FS

55 W/cm3

• Flinabe 69 W/cm3
• Be

47 W/cm3

10 20 30 40 50 60 70 10 20 30 40 50

FS Flinabe Be

Power Density (W/cm3) Depth in Blanket (cm) Radial Distribution of Power Density in Blanket Components at OB Midplane Peak Neutron Wall Loading 5.45 MW/m

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Recirculating Blanket Flinabe/Be/FS

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Nuclear Heating in Components

• f Dual Coolant Blanket with Be

ÿ Peak nuclear heating values in OB blanket

• FS

56 W/cm3

• Flibe

70 W/cm3

• Be

36 W/cm3

10 20 30 40 50 60 70 80 8 16 24 32 40 48 56 64

Flibe FS Be

Power Density (W/cm3) Depth in Blanket (cm) Radial Distribution of Power Density in Blanket Components at OB Midplane Peak Neutron Wall Loading 5.45 MW/m

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Dual Coolant Blanket Flibe/He/Be/FS

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Nuclear Heating in Components

• f Dual Coolant Blanket with Pb

ÿ Peak nuclear heating values in OB blanket

• FS

49 W/cm3

• Flibe

73 W/cm3

• Pb

50 W/cm3

10 20 30 40 50 60 70 80 8 16 24 32 40 48 56 64

FS Flibe Pb

Power Density (W/cm3) Depth in Blanket (cm) Radial Distribution of Power Density in Blanket Components at OB Midplane Peak Neutron Wall Loading 5.45 MW/m

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Dual Coolant Blanket Flibe/He/Pb/FS

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Peak Radiation Damage Parameters in FW Structure (OB Midplane)

ÿ Based on 200 dpa damage limit blanket lifetime is ~2.4 FPY

922 983 1005 He appm/FPY 84.2 74.8 76.4 dpa/FPY DC-Pb DC-Be SC

Peak Radiation Damage Parameters in Shield (IB Midplane)

213 183 100 He appm @30 FPY 41 33 18 dpa @30 FPY

DC-Pb DC-Be SC

ÿBased on 200 dpa damage limit shield is expected to be lifetime component with a large margin that allows for uncertainties due to modeling and possible hot spots due to streaming at module sides

Total Tritium Production in Be (for 2.4 FPY blanket life)

1.80 kg 2.97 kg Total 1.34 kg 2.19 kg OB 0.46 kg 0.78 kg IB DC-Be SC

ÿModest amount of tritium produced in Be ÿTritium inventory will be much smaller depending on temperatures ÿ40% less tritium produced in Be of DC blanket

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Shielding Requirement

50 100 150

SC DC-Be DC-Pb

Blanket

V V Shield Blanket

50 100 150

SC DC-Be DC-Pb

Blanket Radial Build (cm) Radial Build (cm)

IB OB

ÿRadial build determined to insure that radiation limits are satisfied with adequate margins

• Shield is lifetime component (<200 dpa)
• VV is reweldable (<1 He appm)
• Magnet adequately shielded (<1010 Rads)

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Peak VV Damage Parameters

ÿ Shielding effectiveness of DC blanket is lower than SC blanket due to large amount of He ÿ With same IB radial build damage parameters in shield, VV, and magnet are a factor of ~2 lower with the SC blanket ÿ DC designs with Be and Pb result in comparable radiation damage parameters

SC DC-Be DC-Pb IB OB IB OB IB OB Peak end-of-life dpa 0.035 0.007 0.065 0.029 0.07 0.03 Peak end-of-life He appm 0.21 0.04 0.38 0.16 0.45 0.17

Peak Magnet Damage Parameters (IB)

SC DC-Be DC-Pb Design Limit Peak Nuclear Heating (mW/cm3) 0.14 0.35 0.29 1 Peak end-of-life Fast Neutron Fluence (n/cm2) 1.3x1018 2.8x1018 2.8x1018 1019 Peak end-of-life Dose to Insulator (Rads) 3.1x109 7.6x109 6.6x109 1010 Peak end-of-life dpa to Cu Stabilizer 9.0x10-4 2.1x10-3 2.0x10-3 6x10-3

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Summary

ÿThe three design concepts have the potential for achieving tritium self-

• sufficiency. Several design parameters can be adjusted (e.g., multiplier

thickness, blanket thickness, etc) to insure tritium self-suffiency ÿUsing He gas in the dual coolant blanket results in

• Lower blanket shielding effectiveness
• 15 cm thicker OB blanket

ÿHigher blanket energy multiplication with Be

1.27 for self-cooled blanket with Be 1.21 for dual coolant blanket with Be 1.13 for dual coolant blanket with Pb

ÿSmaller amount of Be required in dual coolant design with Flibe compared to self-cooled blanket with Flinabe resulting in ~40% less tritium production in the Be multiplier ÿWith total B/S/VV radial build of 105 cm IB and 120 cm OB it is possible to achieve:

• shield lifetime component
• VV reweldable
• magnets adequately shielded

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Issues related to multiplier choice (Pb vs. Be)

Unique issues for MS blankets:

• Neutron multiplier needed: Be better neutron multiplier. Smaller amount needed.
• Need for REDOX and chemistry control: Be in direct contact with MS helps

Issues with Be:

• Be toxicity
• Be resources
• Tritium production in Be. How much tritium inventory retained in Be (dependence on

temp.)

• Need to accommodate swelling in Be

Issues with Pb:

• Safety issues related to Po production in Pb. Could Bi/Po be removed efficiently?

Compatibility Issues:

• Interaction of Be with FS. Formation of discontinuous brittle superficial layer with

generation of holes in Be. Rate of layer formation depends on temp

• Pb compatibility with FS. Corrosion (main mechanism is dissolution of FS) dependence
• n temperature and velocity. Can we accurately control oxygen content in Pb to help

forming stable adherent oxide film (not much O to avoid intergranular attack) that alleviates dissolution? What is max allowable interface temp?

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Detailed Blanket Radial Build

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Radial Build of SC Blanket

ÿ Radial build for OB blanket ÿ Radial build for IB blanket

zone Thickness Flibe NCF Be 1 First wall 3 mm 1 2 FW Flibe channel, poloidal flow 10 mm 0.92 0.08 3 Multiplier front wall 3 mm 1 4 Multiplier region 70 mm 0.322 0.08 0.598 5 Multiplier back wall 3 mm 1 6 Flibe channel+side wall 10 mm 0.92 0.08 7 Flibe channel back wall 6 mm 1 8 Flibe + Side walls, a mixed zone 366 mm 0.932 0.068 9 Back wall, a mixed zone 29 mm 0.6069 0.3931 Total 500 mm zone Thickness Flibe NCF Be 1 First wall 3 mm 1 2 FW Flibe channel, poloidal flow 10 mm 0.92 0.08 3 Multiplier front wall 3 mm 1 4 Multiplier region 70 mm 0.322 0.08 0.598 5 Multiplier back wall 3 mm 1 6 Flibe channel+side wall 10 mm 0.92 0.08 7 Flibe channel back wall 6 mm 1 8 Flibe + Side walls, a mixed zone 266 mm 0.932 0.068 9 Back wall, a mixed zone 29 mm 0.6069 0.3931 Total 400 mm

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Radial Build of DC-Be Blanket

ÿ Radial build for OB blanket ÿ Radial build for IB blanket

Zone thickness(mm) steel Be FliBe helium 1 FW, front 3 1 2 FW, cooling channel 22 0.13 0.87 3 FW, back 3 1 4a Flibe front channel, poloidal flow 20 0.03 0.93 0.04 4b Multiplier front wall 3 0.88 0.1 0.02 4c Be pebble bed 50 0.03 0.60 0.35 0.02 4d Multiplier back wall 3 0.88 0.1 0.02 4e Flibe back channel, poloidal flow 20 0.03 0.93 0.04 5 second wall 38 0.32 0.68 6 breeding zone A 288 0.03 0.93 0.04 7 breeding zone B 166 0.09 0.64 0.27 8 back wall 34 0.66 0.34 total 650 Zone thickness(mm) steel Be FliBe helium 1 FW, front 3 1 2 FW, cooling channel 22 0.13 0.87 3 FW, back 3 1 4a Flibe front channel, poloidal flow 20 0.03 0.93 0.04 4b Multiplier front wall 3 0.88 0.1 0.02 4c Be pebble bed 50 0.03 0.60 0.35 0.02 4d Multiplier back wall 3 0.88 0.1 0.02 4e Flibe back channel, poloidal flow 20 0.03 0.93 0.04 5 second wall 38 0.32 0.68 6 breeding zone A 64 0.03 0.93 0.04 7 breeding zone B 140 0.09 0.66 0.25 8 back wall 34 0.66 0.34 total 400

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Radial Build of DC-Pb Blanket

ÿ Radial build for OB blanket ÿ Radial build for IB blanket

Zone thickness(mm) steel Pb FliBe helium 1 FW, front 3 1 2 FW, cooling channel 22 0.13 0.87 3 FW, back 3 1 4 multiplier 50 0.05 0.87 0.08 5 second wall 38 0.32 0.68 6 breeding zone A 334 0.03 0.93 0.04 7 breeding zone B 166 0.09 0.64 0.27 8 back wall 34 0.66 0.34 total 650 Zone thickness(mm) steel Pb FliBe helium 1 FW, front 3 1 2 FW, cooling channel 22 0.13 0.87 3 FW, back 3 1 4 multiplier 50 0.05 0.87 0.08 5 second wall 38 0.32 0.68 6 breeding zone A 84 0.03 0.93 0.04 7 breeding zone B 166 0.09 0.64 0.27 8 back wall 34 0.66 0.34 total 400