Sh ield Performance and Magnet Protection in Thick Liquid Wa lconcepts. Mah moud Youssef UCLA

Transcription

1 Sh ield Performance and Magnet Protection in Thick Liquid Wa lconcepts Mah moud Youssef UCLA Presented at the 5th APEX Group Meeting, UCLA, November 2-4, 998

2 Outlines Evaluate dam age param eters at key locations in Inboard and Outboard of the GMD thick liquid concept under different shield thickness for neutron w a l load of 0 MW/m2: Configuration: - Brad s layout for the I/B and O/B - 2 cm liquid FW fo low ed by 40 cm liquid pocket - 4 cm pocket back wa l - shield (varying thickness) behind pocket - max thickness 50 cm, O/B - max thickness 49 cm I/B Structure/Breeder: - Ferritic steel/flibe (naturalli6) - Ferritic Steel/Li-Sn (90% Li6) Dam age param eters: - AnnualDPA rate - H e and H production rates (appm /year) - H eating rate in the winding pack of the SCM

3 Outlines (Cont d) Selected Locations: - Front wa lof the Vacuum Vessel - TF Coil - Copper Stabilizer Evaluate nuclear h eating rate through out the system. Com pare nuclear perform ance of Flibe and Li-Sn for various Li-6 Enrichment: - TBR - Pow er Multiplication, PM - Totalpow er deposited in the system/breeder/structure

4 Total Nuclear Heating in the GMD Thick Liquid Conceptual Design 00 Flibe/FS-natLi6 Total Nuclear Heating in the GMD Thick Liquid Conceptual Design Power Deposited (w/cc) WL=0MW/m2 Power Deposited (w/cc) L FW/Blanket Shield Outboard Total (Flibe/FS-nat Li6) WL=0MW/m2 Gap Gap TF coil TF coil V.V Winding Pack Distance from Tokamak Center, cm Distance from Tokamak Center, cm Maximum Nuclear H eat Deposition rate, w/cc (W L= 0 MW/m2) (42 cm Flibe naturalli6, 50 cm shield) L.FW Pocket back Plate Sh ield V.V.W a l TF Coil W inding Pack I/B O/B

5 Annual Displacement Per Atom in Various Parts of the System 0 dpa (VV)-I/B-Flibe dpa (VV)-O/B-Flibe dpa (TF Coil)-I/B-Flibe dpa (TF Coil)-O/B-Flibe dpa (Cu)-I/B-Flibe dpa (Cu)-O/B-Flibe 0. DPA/year Thick Liquid Layer: Flibe-Natural Li6 Wall Load: 0 MW/m Shield Thickness, cm DPA rates in the V.V.of the I/B and O/B are similar. DPA rates in the TF coiland Cu stabilizer on the I/B are ~ 5 and ~0 times larger in the I/B than in the O/B, respectively. The attenuation length of the shield (40% Flibe, 60% FS) is ~ 20 cm i.e. an order of magnitude reduction in V.V. DPA rate for ever 20 cm of the shield DPA rate in the V.V.at 50 cm-thick shield is 0.0 DPA/year. This is below the 200 dpa limit for the V.V. to be a lifetime component

6 Helium Production Rate (appm/yr) in Various Parts of the System appm/year Thick Liquid Layer: Flibe-Natural Li6 Wall Load: 0 MW/m2 He4 (VV)-I/B-Flibe He4 (VV)-O/B-Flibe He4 (TF Coil)-I/B-Flibe He4 (TF Coil)-O/B-Flibe Shield Thickness, cm Hydrogen Production Rate (appm/yr) in Various Parts of the System appm/year Thick Liquid Layer: Flibe-Natural Li6 Wall Load: 0 MW/m2 H (VV)-I/B-Flibe H (VV)-O/B-Flibe H (TF Coil)-I/B-Flibe H (TF Coil)-O/B-Flibe Shield Thickness, cm He and H production rates in the V.V.of the I/B and O/B are similar. He and H production rates in the TF coiland Cu stabilizer on the I/B are ~ 5 and ~6 times larger in the I/B than in the O/B, respectively. Helium production rate in the V.V.at 50 cm-thick shield is ~0.02 appm /year. i.e. 0.6 appm after 30 years. This is below the He appm limit for the V.V. to Reweldable.

7 0 Comparison Between Flibe and Li-Sn for Annual DPA Rate dpa (VV)-I/B-Flibe-nat dpa (VV)-I/B-LiSn 90%Li6 dpa (TF Coil)-I/B-Flibe nat dpa (TF Coil)-I/B-LiSn 90%Li6 dpa (Cu)-I/B-Flibe nat dpa (Cu)-I/B-LiSn 90%Li6 DPA/Year Wall Load: 0 MW/m Shield Thickness, cm DPA rates in V.V., TF Coil, and Copper stabilizer are larger in the Li-Sn case than in the Flibe case.if no shield is present the values in the Li-Sn case are a factor of 2-3 larger.at 50 cm-thick shield this factor is ~ an order of magnitude. The attenuation length of Li-Sn shield for DPA rate in the V.V.is ~ 30 cm i.e. an order of magnitude reduction in DPA rate for every 30 cm shield

8 0 Comparison Between Flibe and Li-Sn for Helium Production Rate 00 Comparison Between Flibe and Li-Sn for Hydrogen Production Rate appm/year 0. He4 (VV)-I/B-Flibe nat He4 (VV)-I/B-LiSn 90%Li6 He4 (TF Coil)-I/B-Flibe nat He4 (TF Coil)-I/B-LiSn 90%Li6 He4 (VV)-I/B-LiSn-nat He4 (TF Coil)-I/B-LiSn-nat appm/year 0 0. H (VV)-I/B-Flibe H (VV)-I/B-LiSn H (TF Coil)-I/B-Flibe H (TF Coil)-I/B-LiSn Wall Load: 0 MW/m Shield Thickness, cm Wall Load: 0 MW/m Shield Thickness, cm The He and H production rates in the VV.and TF coilare similar in the Flibe and Li-Sn cases.the attenuation length is ~ 20 cm.he and He production occurs at high energies.this show s that the attenuation characteristics of Flibe and Li-Sn for 4 MeVneutrons are similar.this is not the case for neutrons in the epitherm alenergy ranges 0 kev- 2 MeVwhere more of such neutrons reach the V.V.and TF Coilin the Li-Sn case, causing larger DPA rates at these locations.

9 Comparison of Neutron Spectrum at the Back wall of GMD Liquid Pocket of the Outboard 0 2 Flibe-neutron-nat Li-Sn-neutron-90%Li6 Neutron Spectrum, (n/cm2.sec.en) Wall Load = 0 MW/m Neutron Energy En, ev

10 Comparison Between Flibe and Li-Sn for Heating Rate in the Winding Pack 0. Heating Rate (WP)-I/B-Flibe Heating Rate (WP)-O/B-Flibe Heating Rate (WP)-I/B-LiSn Heating Rate (WP)-O/B-LiSn Heating Rate (WP)-I/B-LiSn-nat Heating Rate (WP)-O/B-LiSn-nat 0.0 w/cc Wall Load: 0 MW/m Shield Thickness, cm Heating rate in the winding pack has similar features to the DPA rates curves, particularity on the I/B side. Attenuation length of the 50 cm-thick Li-Sn shield of ~ 30 cm (to reduce heating rate by an order of magnitude)

11 Tritium Breeding Ratio and Power Multiplication V.S. Li-6 Enrichment in the GMD Thick Liquid Blanket Design TBR Structure: Ferritic Steel TBR (Flibe) TBR (Li-Sn) PM (Flibe) PM(Li-Sn) PM Power Deposited, (w/cm) Total Power Deposited per Unit Length (w/cm) and Contribution From Neutron and Gamma Heating (GMD Blanket Concept) Blanket/Shield System 0 MW/m2 Total (Flibe/FS) Neutron (Flibe/FS) Gamma (Flibe/FS) Tot (Li-Sn/FS) Neutron (Li-Sn/FS) Gamma (Li-Sn/FS) Li-6 Enrichment Li-6 Enrichment NaturalLi6 25% Li-6 90% Li-6 Flibe Li-Sn Flibe Li-Sn Flibe Li-Sn TBR PM TBR is low (0.43) for Li-Sn with natural Li6. It increases rapidly with increasing Li6 enrichment. It reaches a values as high as.35 at 90% Li-6 enrichment TBR in Flibe decreases with Li-6 enrichment. It decreases by ~0% at 90% Li-6 enrichment. Power Multiplication decreases with Li-6 enrichment for both breeders.

12 Neutron Spectrum, (n/cm2.sec.en) Comparison of Neutron Spectrum at the Back wall of GMD Liquid Pocket of the Outboard (Natural Li6) Flibe-neutron-nat Li-Sn-neutron-nat Wall Load = 0 MW/m Neutron Energy En, ev Neutron Spectrum, (n/cm2.sec.en) Comparison of Neutron Spectrum at the Back wall of GMD Liquid Pocket of the Outboard (90%Li6) Flibe-neutron-90%Li6 Li-Sn-neutron-90%Li6 Wall Load = 0 MW/m Neutron Energy En, ev At natural Li-6 enrichment, the neutron spectrum in the Flibe case is generally larger in the low energy range (where Li6(n,a) xs is large) than in the Li-Sn case. This leads to a larger TBR. At 90% Li6 enrichment, the neutron flux in the low energy range falls below the corresponding flux in the Li-Sn case. This leads to a lower TBR.

13 Total Power Deposited per Unit Length (w/cm) and Contribution From Neutron and Gamma Heating (GMD Blanket Concept) Total Power Deposited per Unit Length (w/cm) and Contribution From Neutron and Gamma Heating (GMD Blanket Concept) Power Deposited, (w/cm) Breeder 0 MW/m2 Flibe (tot) (Flibe/FS) Flibe (n) (Flibe/FS) Flibe (G) (Flibe/FS) Li-Sn (tot) (Li-Sn/FS) Li-Sn (n) (Li-Sn/FS) Li-Sn (G) (Li-Sn/FS) Power Deposited, (w/cm) FS (tot) (Flibe/FS) FS (n) (Flibe/FS) FS (G) (Flibe/FS) FS (tot) (Li-Sn/FS) FS (n) (Li-Sn/FS) FS (G) (Li-Sn/FS) Structure: Ferritic Steel 0 MW/m Li-6 Enrichment Li-6 Enrichment Power multiplication for Li-Sn breeder at 90% Li6 (.32) is noticeably larger than PM for Flibe (.2). Total heat deposited is larger by ~8% which should be handled by the heat extraction system. Heat deposition due to gamma heating is large in the Li-Sn breeder, particularly heat deposited in the structural material (FS). This is due to the large Sn(n,gamma) XS. The total Sn(n,gamma) reaction decreases as Li-6 enrichment increases (competing processes).

14 GeneralConclusions: With 50 cm-thick shield, the DPA rate in the V.V.(w ith Flibe, naturalli-6) is ~ 0.0 DPA/yr.This is below the 200 dpa limit for the V.V.to be a lifetime component Helium production rate in the V.V.at 50 cm-thick shield is ~0.02 appm /year (Flibe with naturalli6). i.e. 0.6 appm after 30 years. This is below the He appm limit for the V.V. to Reweldable. TBR with Flibe is larger at naturalli-6 enrichment as compared to 90% enrichment.this is true in the case of GMD concept where thick liquid layer is facing the plasma.the TBR with Flibe (.2) is how ever low and raises a concern of achieving tritium self-sufficiency unless a separate neutron multiplier is used. TBR with Li-Sn breeder increases rapidly w ith Li-6 enrichment.at 90% Li6, TBR is ~.35 (better than Flibe).It appears that this breeder could offer sufficient breeding if cleverly used with structure that has less neutron absorption. Li-Sn breeder also offer larger pow er m ultiplication factor (~.33) w hich could improve the therm al cycle.