A high-temperature gas- cooled nuclear reactor consists r = 8 mm of a composite cylindrical wall for which a thorium fuel r, = 11 mm Coolant channel with helium flow (7T, h) = 57 W/m-K) is Graphite element (k encased in graphite (k W/m-K) and gaseous helium flows through an Thorium, - T1 T2 = 3 ra = 14 mm annular coolant channel. Consider T3 conditions for which the helium temperature is To = 600K and the convection coefficient at the outer surface of the graphite is h = 2000 W/mK. If the thermal energy is uniformly generated in the fuel element at a rate = 10* W/m', what are the temperatures Ti and T2 at the inner and outer surfaces, respectively, of the fuel element?