Preliminary Neutronics Assessment of Molten Salt Blanket Concepts

Transcription

1 Preliminary Neutronics Assessment of Molten Salt Blanket Concepts Mohamed Sawan Fusion Technology Institute University of Wisconsin, Madison, WI ITER TBM Meeting UCLA Feb ,

2 Preliminary Neutronics Assessment 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] The FS alloy F82H used as structural material Same reactor configuration and power loadings used for fair comparison Average reactor neutron wall loading 3.84 MW/m 2 Peak neutron wall loading: OB 5.45 MW/m 2, IB 3.61 MW/m 2 Average neutron wall loading: OB 4.61 MW/m 2, IB 2.80 MW/m 2 Radial build between FW and VV is 80 cm IB and 95 cm OB 25 cm thick VV Water cooled steel VV and shield TBR has a flat peak in the enrichment range 40-60%. 40% 6 Li is used 1D calculations with IB and OB blankets modeled simultaneously Several iterations were made to determine the radial build that achieves adequate tritium breeding and shielding for VV and magnet Larger margins are considered to account for uncertainties resulting from approximations in modeling Multi-dimensional calculations are to be performed later to accurately model the blanket 2

3 Blanket Radial Build SC Flinabe DC Flibe/He DC Flibe/He Be Be Pb Blanket Thickness 50 cm OB 40 cm IB 65 cm OB 40 cm IB 65 cm OB 40 cm IB Multiplier Zone 7 cm 60% Be 5 cm 60% Be 5 cm 87% Pb Same TBR can be achieved with a thinner SC OB blanket compared to the DC blanket with large He amount To 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) In 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 3

4 Tritium Breeding Potential 1.5 Local TBR IB OB IB OB SC DC-Be DC-Pb Total SC DC-Be DC-Pb Blanket If 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 The blanket design concepts have the potential for achieving tritium selfsufficiency. 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

5 Blanket Energy Multiplication Blanket Energy Multiplication SC DC-Be DC-Pb Blanket 1.13 Using Be yields higher blanket energy multiplication 1.27 for SC blanket with Be 1.21 for DC blanket with Be 1.13 for DC blanket with Pb 5

6 Nuclear Heating in Components of Self-Cooled Flinabe Blanket Radial Distribution of Power Density in Blanket Components at OB Midplane Peak Neutron Wall Loading 5.45 MW/m 2 Power Density (W/cm 3 ) Recirculating Blanket Flinabe/Be/FS FS Flinabe Be Peak nuclear heating values in OB blanket FS 55 W/cm 3 Flinabe 69 W/cm 3 Be 47 W/cm Depth in Blanket (cm) 6

7 Nuclear Heating in Components of Dual Coolant Blanket with Be Radial Distribution of Power Density in Blanket Components at OB Midplane Power Density (W/cm 3 ) Peak Neutron Wall Loading 5.45 MW/m 2 Dual Coolant Blanket Flibe/He/Be/FS Flibe FS Be Peak nuclear heating values in OB blanket FS 56 W/cm 3 Flibe 70 W/cm 3 Be 36 W/cm Depth in Blanket (cm) 7

8 Nuclear Heating in Components of Dual Coolant Blanket with Pb Radial Distribution of Power Density in Blanket Components at OB Midplane Power Density (W/cm 3 ) Peak Neutron Wall Loading 5.45 MW/m 2 Dual Coolant Blanket Flibe/He/Pb/FS FS Flibe Pb Peak nuclear heating values in OB blanket FS 49 W/cm 3 Flibe 73 W/cm 3 Pb 50 W/cm Depth in Blanket (cm) 8

9 Peak Radiation Damage Parameters in FW Structure (OB Midplane) dpa/fpy He appm/fpy SC DC-Be DC-Pb Based on 200 dpa damage limit blanket lifetime is ~2.4 FPY Peak Radiation Damage Parameters in Shield (IB Midplane) FPY He FPY SC DC-Be DC-Pb Based 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) 9 IB OB Total SC 0.78 kg 2.19 kg 2.97 kg DC-Be 0.46 kg 1.34 kg 1.80 kg Modest amount of tritium produced in Be Tritium inventory will be much smaller depending on temperatures 40% less tritium produced in Be of DC blanket

10 Shielding Requirement 150 IB 150 OB Radial Build (cm) Radial Build (cm) Blanket Shield VV 0 SC DC-Be DC-Pb 0 SC DC-Be DC-Pb Blanket Blanket Radial 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 (<10 10 Rads) 10

11 Peak VV Damage Parameters SC DC-Be DC-Pb IB OB IB OB IB OB Peak end-of-life dpa Peak end-of-life He appm Peak Magnet Damage Parameters (IB) SC DC-Be DC-Pb Design Limit Peak Nuclear Heating (mw/cm 3 ) Peak end-of-life Fast Neutron Fluence (n/cm 2 ) 1.3x x x Peak end-of-life Dose to Insulator (Rads) 3.1x x x Peak end-of-life dpa to Cu Stabilizer 9.0x x x10-3 6x10-3 Shielding effectiveness of DC blanket is lower than SC blanket due to large amount of He With same IB radial build damage parameters in shield, VV, and magnet are a factor of ~2 lower with the SC blanket DC designs with Be and Pb result in comparable radiation damage parameters 11

12 12 Summary The three design concepts have the potential for achieving tritium selfsufficiency. Several design parameters can be adjusted (e.g., multiplier thickness, blanket thickness, etc) to insure tritium self-suffiency Using He gas in the dual coolant blanket results in Lower blanket shielding effectiveness 15 cm thicker OB blanket Higher 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 Smaller 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 With 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

13 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 13 Pb compatibility with FS. Corrosion (main mechanism is dissolution of FS) dependence on 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?

14 14 Detailed Blanket Radial Build

15 Radial build for OB blanket Radial build for IB blanket Radial Build of SC Blanket zone Thickness Flibe NCF Be 1 First wall 3 mm 1 2 FW Flibe channel, poloidal flow 10 mm Multiplier front wall 3 mm 1 4 Multiplier region 70 mm Multiplier back wall 3 mm 1 6 Flibe channel+side wall 10 mm Flibe channel back wall 6 mm 1 8 Flibe + Side walls, a mixed zone 366 mm Back wall, a mixed zone 29 mm Total 500 mm zone Thickness Flibe NCF Be 1 First wall 3 mm 1 2 FW Flibe channel, poloidal flow 10 mm Multiplier front wall 3 mm 1 4 Multiplier region 70 mm Multiplier back wall 3 mm 1 6 Flibe channel+side wall 10 mm Flibe channel back wall 6 mm 1 8 Flibe + Side walls, a mixed zone 266 mm Back wall, a mixed zone 29 mm Total 400 mm 15

16 Radial build for OB blanket Radial Build of DC-Be Blanket Zone thickness(mm) steel Be FliBe helium Radial build for IB blanket 1 FW, front FW, cooling channel FW, back 3 1 4a Flibe front channel, poloidal flow b Multiplier front wall c Be pebble bed d Multiplier back wall e Flibe back channel, poloidal flow second wall breeding zone A breeding zone B back wall total 650 Zone thickness(mm) steel Be FliBe helium 1 FW, front FW, cooling channel FW, back 3 1 4a Flibe front channel, poloidal flow b Multiplier front wall c Be pebble bed d Multiplier back wall e Flibe back channel, poloidal flow second wall breeding zone A breeding zone B back wall total

17 Radial build for OB blanket Radial Build of DC-Pb Blanket Zone thickness(mm) steel Pb FliBe helium 1 FW, front FW, cooling channel FW, back multiplier second wall breeding zone A breeding zone B back wall total 650 Radial build for IB blanket Zone thickness(mm) steel Pb FliBe helium 1 FW, front FW, cooling channel FW, back multiplier second wall breeding zone A breeding zone B back wall total