1. A. Schwendt, A. Nobile, P. Gobby, W. Steckle Los Alamos National Laboratory D. T. Goodin, G. E. Besenbruch, K. R. Schultz General Atomics Laser IFE Workshop February 6, 2001 Naval Research Laboratory, Washington D.C. Status of IFE Tritium Inventory

2. Goal of this work is to evaluate the tritium inventory of a target filling facility  Develop tools to evaluate the tritium inventory  Target characteristics (material properties, foam densities, gold coatings, etc.)  Characteristic time scales  Inventory of each step of the process  Evaluate influence of:  increased temperature of the fill process  reduction of void volume  Studies provide guidance into development of IFE plants  Define issues for future R&D needed to achieve feasibility goals. Develop low inventory tritium target filling methods to minimize inventory. Develop and evaluate cradle-to-grave production scenario including fabrication, filling, layering, and handling of targets in a high volume process. CURRENT DP PROGRAM TASKS:

3. Target fabrication feasibility and cost is being evaluated for HIF and Direct Drive approaches  Baseline HIF target is the close-coupled design  D. A. Callahan-Miller and M. Tabak, Nuclear Fusion Vol. 39 No. 7, 883 (1999).  Baseline Direct Drive target is the NRL design.

4. Fabrication and filling of the direct drive target is simpler DT Diffusion Fill Cool to Cryo Temps Evacuate DT DT Ice Layer Inject Manufacture Capsule

5. We are evaluating the minimum tritium inventory required for IFE plants DT Diffusion Fill Capsule Cool to Cryo Temps Evacuate DT DT Ice Layer Inject Manufacture Materials “JIT” approach Targets are processed at the rate necessary for injection Benefit of model: eliminates engineering assumptions

6. DT inventory during filling DT pressures during filling DT Diffusion Fill Pressure fill pressure Time Pressure P(t) P ext (t) N fill = (shot rate) x (fill time) P ext, V V capsule P, V inner fill time PoPo { P o =P buckle *0.75 Fill Cell

7. The capsule fill time is a function of the capsule wall thickness and internal foam properties DT pressures during filling DT Diffusion Fill Pressure fill pressure Time Pressure P(t) P ext (t) fill time PoPo { P o =0.75*P buckle HIF Target Direct Drive Target t solid CH shell 0.8  m CH membrane CH foam Buckle pressures for the HIF target are simple to estimate Buckle pressures for the DD target depend on the internal foam properties

8. Direct Drive Target Buckle Determination and Considerations Outer Shell Foam support Assume 0.8µm GDP layer (no gold) 0.002 - 0.006 atm 0.062 atm ISSUES: Elastic collapse 0.014 atm Plastic collapse 0.857 atm

9. The cooling time is a function of the material properties of the capsule, holding vessel, and high pressure cylinder Cool to Cryo Temps WORK IN PROGRESS Target Holding Vessel Target Holding Vessel (Aluminum) High Pressure Vessel (Stainless steel)

10. Tritium inventories have been evaluated  The above analysis has been performed to evaluate “minimum” tritium inventory - this allows comparison of inventories for different approaches without assuming any engineering approach.  “Actual” tritium inventories based on real engineering scenarios will be evaluated in the future. Theoretical minimum tritium inventory (Actual inventories will be higher)  6.7 shots per second *  Void fraction – 0.33  Fill Temp – 25  C  Cool time - 2 hr  Evac time - 1 hr  layer time - 8 hr  IR layer time - 2 hr  Fill overpressures are 75% of buckle pressure * target design by Bodner, et al requires 6.7 Hz reprate for Sombrero plant design with net power of 1 GWe

11. Higher temperatures decrease fill time Shorter fill time decreases inventory Direct Drive Target Beta-layering Infra red-layering Diffusion Fill Time (days) Increasing the capsule temperature during filling and decreasing layering time decreases tritium inventory

12. Decreasing the void volume in the fill system decreases tritium inventory Tritium Inventory vs. Void Fraction for Fill of Direct Drive Target Fill Temperature – 340 K Cool Fill Fill and cool Beta-layering IR-layering Tritium Inventory (kg) Total inventory Fill and Cool Inventories

13. Effect of a gold coating on tritium inventory? 0.8  m CH membrane CH foam 0.03  m gold coating  x = 300 Å Ks = 1.9x10 -23 mol/m Pa 0.5 s 10 12 days !!

14. Progress has been made in reducing IFE plant tritium inventories, but more work is required  Reducing tritium inventories in HIF and Direct Drive IFE facilities necessitates the following: Diffusion fill at temperatures as high as possible. Minimize dead-space in fill system. Minimize DT ice layering times through use of enhanced layering methods (infra red layering)  Use these tools to evaluate target design options  Goal is to reduce tritium inventories to acceptable levels

15. Progress has been made in reducing IFE plant tritium inventories, but more work is required  Continue the development of the tools  rigorous calculation of the cool times  improve P buckle calculations for DD target  Update inventories as we better understand material properties  need P buckle (T) data (foam properties)  need experimentally measured permeability K(T)  Implement “real” engineering assumptions into model  batch process, non-idealities (ex. “overfill”)  Provide guidance for target material development WORK IS IN PROGRESS