High-temperature carbon-irradiation issues for the Sombrero ICF reactor

In order to assess the feasibility of carbon materials for the first-wall o f the Sombrero KrF laser-driven ICF fusion reactor [W.R. Meier et al., OSIR IS and SOMBRERO Inertial Fusion Power Plant Designs, W.J. Schafer Associate s Report, WSJA-92-01, DOE/ER/54100-1 (1992); W.R. Meier, et al., Fus. Eng. Des. 25 (1994) 145-157; I.N. Sviatoslavsky, et al., Fus.Tech. 21 (1992) 147 0-1474], published experimental results relating to mechanical and thermal properties of graphites and carbon-fiber-composites (CFC's) under neutron i rradiation and high heat loads are reviewed. Results are compared to publis hed design requirements for the Sombrero ICF reactor, with particular atten tion to three separate issues of concern: (1) Erosion rates of the first wa ll are highly sensitive to the thermal conductivity value, which is itself environment-sensitive (radiation and high temperature). Erosion rates at th e first wall are calculated here using a high-temperature post-irradiation conductivity value of 50 W/m K, with complete erosion of the first wall lay er predicted within 1.25 full-power years (FPY), illustrating the sensitivi ty of erosion rates to thermal conductivity assumptions; (2) Radiation-indu ced swelling in 2-D and 'pseudo 3-D' CFC's is consistently similar to 20% u nder high-temperature neutron damage of 5 dpa (0.33 FPY). This level of swe lling would pose technical challenges to the engineering of the target cham ber modules; (3) Total tritium retention is predicted to be similar to 0.5- 5 kg in the Sombrero chamber within 0.67 FPY, which may call into question safety-status assumptions of the CFC-based chamber design,. These results i ndicate the urgency of high-temperature neutron-irradiation tests of fully symmetric 3-D CFC's in order to support the plausibility of a carbon first- wall IFE chamber such as proposed for Sombrero. (C) 2001 Elsevier Science B .V. All rights reserved.