Thermal-hydraulic analysis of unit cell for solid breeder TBM Presented by P. Calderoni ITER-TBM meeting March 3, 2004 UCLA

¼ port sub-module analysis already presented 1 of 10 alternative cooling flow paths First wall inlet manifold (Tin= 300oC) First wall outlet manifold (also layer breeding units inlet manifold) (T= 353oC) Layer breeding units outlet manifold (T=500oC) Edge-on breeding units inlet manifold (1 of 2 alternative paths) T=353oC Edge-on breeding units outlet manifold (1/2) T=500oC Mass flow rate In: 0.9 kg/s Out: 0.82 kg/s By-pass: 0.08 kg/s

Thermo-mechanics tests unit cell Volumetric heat is generated in the unit cell by neutron capture in the breeder, multiplier and structural materials Tmax < 850C to ensure pebble bed integrity Average nuclear heating rates from 2-D calculations by Youssef, Sawan, Ying: Structure (55% F82H) = 1.24 W/cm3 Breeder (Li4SiO4, 75% Li6, single size, 60% packing fraction) = 3.24 W/cm3 Beryllium (single size, 60% packing fraction) = 1.24 W/cm3 FEM thermal analysis Inlet 300 C Volumetric ratio for TM units: Structure = 20% Breeder = 35% Beryllium = 45% Outlet 500 C

Thermo-mechanics tests unit cell Independent mass flow control and manifold design allow to choose optimal temperature distribution. Breeder bed front toroidal dimension: 18 mm Back to front ratio = 1.7 Operational windows of different ceramic breeders will be tested. Variable temperature distribution in each unit cell is desirable Single pass configuration, parallel flow: 32 channels 6.5 mm pitch channel length = 2.5 m 5 mm Unit cell mass flow = 31.8 g/s He flow velocity = 10 m/s h = 1400 W/m2 K Channel Dp = 6000 Pa 3.5 mm 6.5 mm

Thermo-mechanics tests unit cell Double pass configuration, upper half and lower half counter flow: 16 channels 6.5 mm pitch channel length = 5 m Unit cell mass flow = 31.8 g/s He flow velocity = 20 m/s h = 2400 W/m2 K Channel Dp = 40000 Pa Single pass configuration, counter flow: 32 channels 6.5 mm pitch channel length = 2.5 m Unit cell mass flow = 31.8 g/s He flow velocity = 10 m/s h = 1400 W/m2 K Channel Dp = 6000 Pa

Neutronics and tritium production tests unit cell Simplest, low cost design is considered for NT unit cells. Temperature limit is ensured by overestimating mass flux. Temperature gradient within the 4 sections is not an issue. Tmax < 350C to inhibit T release Unit cells are exposed only to a few irradiation pulses during D-D and early D-T phases Inlet 100 C Volumetric ratio for NT units: Structure = 26% Breeder = 26% Beryllium = 48% Outlet 250 C

Summary Thermal-hydraulic analysis of unit cells has been performed Independent He cooling circuit allows wide operational window For neutronic tests unit cells the simplest configuration is chosen, and the outlet He temperature limited to 250 C to ensure T trapping inside breeder material at all locations For thermo-mechanics tests unit cells a combination of flow rate and manifold design optimization will allow to test operational windows of different ceramic breeder materials Flow parameter optimization will be finalize with 3-D thermal analysis