A double-walled steam generator is used in the fusion power cycle to replace the intermediate loop. This will save the cost associated with a complicated system and the associated temperature degradation. The mechanical design of the steam generator is similar to that proposed for LMFBR application. The heat transfer and tritium diffusion calculations are performed. The double-walled steam generator provides a tritium diffusion barrier factor > 105 while increasing the surface area by 25% compared to a singlewalled steam generator.