Heat flux capabilities of first-wall tube arrays for an experimental fusion reactor

Abstract

Abstract A preliminary design study has been made of some of the thermomechanical problems of water and helium cooling for the first wall of a near-term experimental fusion reactor. The first wall is envisioned as an array of 316 stainless steel tubes between the plasma and the blanket modules to intercept a heat flux from the plasma estimated to be between 0.25 and 1.0 MW/m 2 . Evaluations have been made of the maximum allowable heat fluxes for constraints imposed on the tube wall temperature, the cyclic stresses, the quasi-steady stresses and energy recovery from the coolant. For tubes with 2 meter long heated sections, 10 mm inside diameter and 1 mm wall thickness, water cooling was found to be more than adequate for plasma heat fluxes over 1 MW/m 2 with a fatigue life of 10 6 cycles; for a 2 mm wall thickness, at least 0.7 MW/m 2 can be handled for the same fatigue life. Helium-cooled tubes can also handle heat fluxes up to about 1 MW/m 2 with a 1 mm tube wall thickness and over 0.5 MW/m 2 with a 2 mm tube wall thickness, but the required pumping powers tend to be high. The problems of plasma disruptions and erosion by energetic plasma ions are also discussed briefly.