1. Tritium Breeding Blanket Part II: Coolant Properties, Shielding, and Tritium Breeding Ratio Nicholas Alfred NRE 4610-A :Intro to Fusion Dec 7 th, 2015 500

2. Why Li17Pb83 High density [~9015 kg/(m^3)] [1] (and therefore a high mass flow rate can be obtained at lower velocities) High thermal conductivity [~18.58W/(m*K)] [1] (and therefore a more uniform temperature distribution in the coolant channel) Modest specific heat [~187.2J/(kg*K)] [1] (which allows it to remove the heat from the system while staying under the melting point of the ODS structural material) Combines the tritium breeding and coolant system to reduce system complexity Pb provides n-2n and Li-6 provides Li(n,α)T [2] reactions At the eutectic point so the melting temperature is at its lowest [3]

3. Blanket Shielding material density (g/m^3) Molecular weight (g/mol) Region thickness (m) avg. cross- section (m^2) [5] attenuation factorentering fluxexit flux He5.76E+03 [4]4.00E+001.80E-023.66E-288.82E-011.47E+171.29E+17 ODS Steel7.64E+06 [6]4.75E+011.80E-023.24E-285.05E-011.29E+176.53E+16 He5.76E+034.00E+003.50E-033.66E-289.76E-016.53E+166.38E+16 SiC3.21E+064.01E+011.00E-022.90E-288.14E-016.38E+165.19E+16 LPb4.80E+051.73E+024.55E-015.59E-283.15E-025.19E+161.63E+15 SiC3.21E+064.01E+011.00E-022.90E-288.14E-011.63E+151.33E+15 He5.76E+034.00E+003.50E-033.66E-289.76E-011.33E+151.30E+15 ODS Steel7.64E+063.41E+021.80E-023.24E-288.20E-011.30E+151.06E+15 He5.76E+034.00E+001.80E-023.66E-288.82E-011.06E+159.38E+14

4. MHD Pressure drop in the Breeder Conductivity of coolant = 7.213*10^7 S/m [1] which means it will be heavily affected by the magnetic field without insolation by the SiC tubes. With the tubes the pressure change per unit length due to the flowing coolant affected by the magnetic field is in the order of 10^(-4) Pa/m [2] which can be neglected compared to the frictional pressure drop per unit length

5. Tritium Breeding Ratio and Doubling Time From estimations in the downtime and from the loss of tritium due to decay and processing, the TBR was estimated to be 1.2 for the system. [7] The time to double this amount of tritium is 2 years assuming no downtime or loss of tritium that is produced in the blanket to the rest of the system. [2]

6. References [1] Zinkle, S. J “Summary of Physical Properties for Lithium, Pb-17, and (LiF) n BeF 2 Coolants” Sandia National Lab, July 1998. [2] Stacey, W.M. Fusion Textbook [3] Jauch, U, et al. “Thermophysical Properties in the System Li-Pb.” Institut für Material-und- Festkörperforschung. Sep. 1986. [4] Todreas, N. E, et al. “Nuclear systems thermal hydraulic fundamentals second eddition – revised printing volume 1” (2012).

7. References Cont. [5] Cross-secton database http://www.kayelaby.npl.co.uk/atomic_and_nuclear _physics/4_7/4_7_2.html, accessed on Nov 28 th 2015. http://www.kayelaby.npl.co.uk/atomic_and_nuclear _physics/4_7/4_7_2.html [6] ODS data page https://www.ipp.mpg.de/1532493/P93A.pdf, accessed on Nov 30, 2015. https://www.ipp.mpg.de/1532493/P93A.pdf [7] Wong, CPC, et al. “An overview of dual coolant Pb-17Li breeder…” Fusion Engineering and Design 81 (2006).