1. ss Hefei, China July 19, 2011 Nuclear, Plasma, and Radiological Engineering Center for Plasma-Material Interactions Contact: druzic@illinois.edu Flowing Liquid Lithium Limiter for HT-7 Utilizing TEMHD to maintain a clean Li surface, keep it below 400C, and prevent ejection

2. ss Hefei, China July 19, 2011 Conceptual Design To flow against a high field one needs to maintain the temperature gradient even outside of the plasma heat flux zone. How: utilize TEMHD in the return flow legs too: In a limiter machine such as HT-7, this is easier since there is some heat flux along the entire plasma-facing surface. 2 Hot Heat flux Cooling channels Inlet Outlet Lithium reservoir Li flow B J J J Hot, passively (not cooled) or heated

3. ss Hefei, China July 19, 2011 Velocity and temperature gradient Average velocity of liquid lithium in the trench The power transferred by the trench structure is written as The temperature gradient can be calculated through

4. ss Hefei, China July 19, 2011 Top surface temperature and flow velocity for SLiDE SLiDE’s geometric parameters are used here. Heat flux is 4MW/m^2 (typical value for our experiment, corresponding to 1500W e-beam power). Top surface temperature increases with the magnetic field and flow velocity decreases with the magnetic field after 0.01T (100Gauss). This model fits our experimental results 4

5. ss Hefei, China July 19, 2011 Apply to HT-7 to find parameters for the trench Top surface temperature and flow velocity change (from previous equations). heat flux (6MW/m^2), toroidal magnetic field (2T), the length of direct heating area along radius direction (80mm), the length of hot region along a single trench (L 1 ) (110mm) and the length of cool region (L 2 ) (30mm). F. Gao et al, Fusion Eng. Design 83 (2008) 1–5 Q. Li et al, Fusion Eng. Design 85 (2010) 126– 129 5

6. ss Hefei, China July 19, 2011 Estimate top surface temperature and flow velocity Top surface temperature is 396C and flow velocity is 0.36m/s. Bottom of trench is assumed to be kept at 200C. 6

7. ss Hefei, China July 19, 2011 Pressure drop in return flow 7

8. ss Hefei, China July 19, 2011 Ejection problem 8

9. ss Hefei, China July 19, 2011 Possible LiMIT design for HT-7 limiter 9

10. ss Hefei, China July 19, 2011 LiMIT design for HT-7 limiter 3 parts: trench, tray and heat sink Trench and tray are made of stainless steel (SS316) and the heat sink is made of copper. This limiter is 134mm*254mm*28mm. The heat sink needs cooling. 10

11. ss Hefei, China July 19, 2011 Trench 11 Front Back

12. ss Hefei, China July 19, 2011 Trench Trench is 130mm*250mm*6.5mm. Thickness of the SS wall is 0.5mm and width of the lithium trench is 2mm. Height of the trench is 5mm. The thickness between the bottom surface of the trench and the bottom of each channel is 1.5mm (the bottom plate under those fan structure). Both ends of the bottom plate is cut to let lithium flow into the back flow channel (10mm on each side). Minimize the area of free surface to lower the ejection. The top surface of the trench is as high as the edge of the tray. The distance between the bottom surface of the trench and the tray is 5mm. (for back flow) 12

13. ss Hefei, China July 19, 2011 LiMIT design for HT-7 limiter 13

14. ss Hefei, China July 19, 2011 Tray 14 Wall thickness is 2mm. The edge is round shape because of the parallel heat flux. (I’m not sure if this is enough since the toroidal parallel heat flux is a major component of the total heat flux for limiter structure.) Height of the tray is 11.5mm. Thickness of the bottom is 1.5mm.

15. ss Hefei, China July 19, 2011 Engineering Details Will follow based on remainder of visit and detailed consultation with HT-7 staff. 15