Systems Modeling for IFE Power Plants

1. Systems Modeling for IFE Power Plants Rob Schmitt, Wayne Meier LLNL High Average Power Laser Program Meeting Los Angeles, CA June 2, 2004 Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

2. Introduction • Update on lithium-cooled blanket model • W/FS interface ΔT constraint not yet included; waiting for resolution of discrepancies in W surface temperature calculated by different codes • Costing for FW and blanket now included (need to add shield/reflector) • Progress on the helium-cooled solid breeder concept • 1-D heat transfer calculations and temperature constraints for first wall have been added • Breeding blanket details to be added next • Modular Rankine cycle unit efficiency scaling as function of He outlet temp included

3. Systems code of Li-cooled blanket is based upon ARIES design Material masses needed for cost scaling are roughly based on an ARIES-type blanket. First wall unit includes first wall (W/FS), Li coolant, and coolant channel outer wall (FS/SiC/W). (See detail on far right) Remainder is considered as the breeding blanket, mostly Li (~98%) with FS structures (2%). Shield has not yet been included (requirements likely different for IFE since no superconducting magnets to protect).

4. Based on estimates the first wall/blanket will cost ~ $43 M Costing for Li-cooled blanket is based on ARIES unit costs (escalated to 2004) Example: Y = 300 MJ, p = 10 mtorr, Rwall = 8.9 m FW unit = 1.5 mm W / 3.5 mm FS / 2 cm Li / 3 mm FS / 1 mm SiC / 1 mm W Blanket = 60 cm thick, 98 vol% Li, 2 vol% FS • Will use updated unit costs from Les Waganer (ARIES) when they are available.

5. He-cooled first wall has been modeled • Temperature Constraints • Tungsten Wall ≤ 2400 oC • Ferritic Steel ≤ 800 oC • Steady-state heat flux • Includes 3.5% heating from neutrons • Heat transfer coefficient is an important parameter to understand. (needs to remove heat from system) temp 2400 oC (max) 800 oC (max) q” THe W FS Forced He distance

6. Given a specific target yield, we can find the allowable chamber radius 300 MJ 154 MJ Radius of first wall depends on target yield and chamber gas pressure Chamber radius determined by using W temperature constraint (2400 C) for single pulse ΔT. Rep-Rate = 10 Hz

7. A heat transfer code was used to find the convective heat transfer coefficient • Dr. Shahram Sharafat (UCLA) has provided us with a heat transfer code which calculates the convective heat transfer coefficient for helium based upon a variety of parameters. • Heat transfer dependent on pressure, velocity, temperatures, pipe diameter and roughness. • Using a fixed velocity (v = 50 m/s) and fractional roughness (10% of pipe diameter) a parameter study was done in Mathcad to find a curve-fit for the heat transfer coefficient. Curve fit within 10% for: 2.5 mm < D < 2 cm 350 K < T < 1100 K 2 MPa < P < 30 MPa

8. The heat transfer coefficient needed is within reasonable limits of engineering design • Need adequate cooling of the steady-state fluence using convection of the helium along the ferritic steel surface. • Constants: 10 mtorr Xe, Dpipe= 1.7 cm, P = 8 MPa, V = 50 m/s At fixed He pressure, HT coefficient decreases with increasing temperature 154 MJ case allows Tmax = 860K  HT coeff ~ 8200 W/m2K 300MJ case allows Tmax = 830K  HT coeff ~ 8400 W/m2k

9. Yield = 300 MJ Rwall = 8.9 m The max allowable FS temp is the limiting constraint and sets the max He outlet temp • The FS temp (1073 K at the W/FS interface) is the most constraining temp, therefore helium temperature is set for given yield and rep-rate. • As shown on graph, the He outlet temp is given for a specific yield and radius.

10. Thanks to R. Raffray for providing tabular Rankine cycle efficiency data. A modular Rankine cycle model is being developed to couple with the blanket designs • Curve fits have been created to model the efficiency of the steam cycle based upon chamber outlet helium temperature, as this is the most important parameter. • Cycle efficiencies range from 38-42% for 154 MJ and 300 MJ examples. (assuming chamber outlet = FW outlet temp) • If blanket materials can operate at higher temps, He from FW could be channeled through blanket to achieve higher chamber outlet temp and efficiency.

11. Summary / next steps • Work on the lithium-cooled blanket design is essentially complete • Helium-cooled first wall scaling complete • Rankine cycle efficiency scaling now included • Next steps • Add solid breeder blanket information. • Include blanket cooling approach – coupled or separate from FW cooling? • Add costing for solid breeder blanket. • Possibly start on molten salt coolant/breeder option.