1. 09 FNST meeting Preliminary Neutronics Analysis for IB Shielding Design on FNSF (Standard Aspect Ratio) Haibo Liu Robert Reed Fusion Science and Technology Center, UCLA August 19 th, 2009

2. 09 FNST meeting Objective  To maximize the TBR of the FNSF design with an effective IB shielding of a given thickness. Approach:  Within a 50-cm IB shielding, the damage rates are kept below the allowable limits by investigation of various IB configuration/material choices, type of magnet insulators, etc.

3. 09 FNST meeting How to Achieve Shielding Effectiveness IB total thickness: 50cm Case1: FW(2cm) + PbLi(7cm) + Reflector(5cm) + Shield(36cm) Case2: FW(2cm) + Be(5cm) + Reflector(5cm) + Shield(38cm) Case3: FW(2cm) + PbLi(2cm) + struc(0.5cm) + Be(5cm) + struc.(0.5cm) + PbLi(5cm) + Reflector(5cm) + Shield(30cm) Case4: FW(2cm) + PbLi(2cm) + struc.(0.5cm) + Be(3cm) + struc.(0.5cm) + PbLi(5cm) + Reflector(5cm) + Shield(32cm) Case5: case3 IB + Full Coverage OB Shield: 5%Water + 5%SS + 25%B 4 C + 65%W

4. 09 FNST meeting Model and Code Model: based on GA FDF design and the VNS design of Ho&Abdou(1996) 3D Calculation: MCNP XS Library: FENDL/MC-2.1 Normal magnet is used. FNSF parameters assumed Elongation: 2 Aspect Ratio A: 3.5 Major Radius R: 2.5m Neutron Wall Load: 2MW/m 2 Peak Inboard Fluence: 6 MWa/m 2 A DCLL blanket (83.4cm) is used on the outboard in all calculations. 20 o Model (CAD Model Generated by MCAM) Reflective Boundary Vacuum Boundary

5. 09 FNST meeting Magnet Case TFC IB OHC OB PFC VV Components Description

6. 09 FNST meeting IB Design Cases IB total thickness: 50cm Case1: FW(2cm) + PbLi(7cm) + Reflector(5cm) + Shield(36cm) Case2: FW(2cm) + Be(5cm) + Reflector(5cm) + Shield(38cm) Case3: FW(2cm) + PbLi(2cm) + struc(0.5cm) + Be(5cm) + struc.(0.5cm) + PbLi(5cm) + Reflector(5cm) + Shield(30cm) Case4: FW(2cm) + PbLi(2cm) + struc.(0.5cm) + Be(3cm) + struc.(0.5cm) + PbLi(5cm) + Reflector(5cm) + Shield(32cm) Case5: case3 IB + Full Coverage OB 1-D Diagram of IB Design Cases Shield: 5%Water+5%SS+ 25%B 4 C+65%W PbLi: 90%enriched 6 Li FW: 40%FS+60%He Reflector: 100%FS Plasma Side

7. 09 FNST meeting Case3 Case5 – Full OB Coverage Difference Between Case3 and Case5

8. 09 FNST meeting Radial Dimension and Materials Composition ComponentRadial thickness (cm) Composition TFC Coil10660%Copper+25%Water+15%insulator Insulator0.240%Epoxy+60%Al 2 O 3 Case7100%SS316L(N)-IG OHC Coil7.860%Copper+25%Water+15%insulator Insulator *0.240%Epoxy+60%Al 2 O 3 VV Void2- Inboard (Case3**) Shielding305%Water+5%SS+25%B 4 C+65%W Reflector5100%FS PbLi5100%PbLi (90%enriched) Struc.0.5100%FS Be5100%Be Struc.0.5 100%FS PbLi2 100%PbLi (90%enriched) FW2 40%FS+60%He SOL5 void Plasma132 Neutron Source SOL5 void OutboardDCLL TBB83.4 From Dr. Youssef (DEMO) ** one of five cases * organic insulator

9. 09 FNST meeting Design Limit for Damage Rates  Limit dose for epoxy insulator ~10 9 Rads (10 MGy)  Limit fast neutron fluence for epoxy insulator ~ 5×10 21 n/m 2  Limit dose for ceramic insulator Generally ~10 12 Rads but > 10 12 Rads for MgAl 2 O 4 (spinel)  Limit fast neutron fluence for MgAl 2 O 4 ~2×10 26 n/m 2  Limit VV He production rate 1 He appm Copper Magnet Electrical Resistivity Change  ∆ρ trans = K Ni C Ni + K Zn C Zn, where K Ni = 11.2 nΩm, K Zn = 3.0 nΩm, and C Ni & C Zn are atomic percentages.  ∆ρ rad,def ≈ A(1-e -B·DPA ), where A is the saturation resistivity change. A=1.2 nΩm for pure copper and 1.6 nΩm for DS and Cu-Cr-Zr copper alloys at 100 o C. B=100. The electrical resistivity of pure copper is 17.1 nΩm at 20 o C.

10. 09 FNST meeting Tritium Breeding Ratio Peak VV He appm  Case3, with a sandwich IB configuration, has larger IB TBR and the total is 1.04. The TBR can be further increased to 1.24 by extending the OB to the divertor region. But does it feasible from the engineering point of view of FNSF?  The peak VV SS helium production rate for all the cases are below the reweldability limit of 1appm. The maximum is 0.33 He appm from Case5. TBR and Peak VV He appm

11. 09 FNST meeting Peak Insulator Dose with Epoxy InsulatorPeak Insulator Dose with Spinel Insulator Peak Insulator Dose The epoxy insulator doses for all the cases are much higher than 10 9 rads. The ceramic insulator is suggested to be used in the FNSF design for its much higher dose limit. The dose in spinel insulator case5 is 4.7×10 10 rads. If the epoxy insulator is preferred, the IB shielding thickness has to be increased.

12. 09 FNST meeting OHC Peak Fast Neutron FluenceOHC Peak DPA  The maximum OHC peak fast neutron fluence is from spinel insulator Case5, which is 8.6×10 19 n/cm 2, higher than the result of epoxy insulator case5.  The maximum OHC peak copper DPA is also from spinel insulator Case5, which is 0.05DPA. Peak Fast Neutron Fluence and DPA

13. 09 FNST meeting OHC Resistivity Change with Epoxy InsulatorOHC Resistivity Change with Spinel Insulator The resistivity change for two kinds of insulators are about 1.2 nΩm, about 7% increase to the total copper electrical resistivity. The DPA-induced electrical resistivity increase in magnet pushes its resistivity almost to the saturation value of 1.2 nΩm for pure copper. The transmutation induced resistivity change is very small because of the low neutron fluence. Peak Magnet Electrical Resistivity Change

14. 09 FNST meeting IB Nuclear Heating Rate Case1 IB Nuclear Heating RateCase3 IB Nuclear Heating Rate The peak nuclear heating rate in Case3 is about 14 w/cc in the FW-FS, about 23 w/cc in the 1 st PbLi layer, which occurs before the beryllium multiplier layer, and this could be because of the effect of the neutron multiplication and reflection from the beryllium. In Case1, the PbLi layer heating rate is also increased along the IB depth because of the reflective neutron induced gamma from the FS reflector.

15. 09 FNST meeting Summary Five FNSF IB cases with 50cm IB thickness have been calculated. Taking into account the high damage rate, ceramic insulator is suggested to be used in FNSF. The MgAl 2 O 4 could be a good choice based upon its good mechanical and electrical properties. For getting tritium self-sufficiency, the Case5, PbLi & Be & PbLi sandwich IB design with full OB coverage, is confirmed better choice. The TBR from Case5 is 1.24, which is larger than the other cases. The DPA-induced increase in magnet electrical resistivity is the dominant part of the total increased resistivity under the low neutron fluence.

16. 09 FNST meeting Thank you for your attention!