Rhenium and molybdenum coatings for dendritic tungsten armors of plasma facing components: Concept, problems, and solutions

Fusion technology development requires materials resistant to heat, erosion and activation. Tungsten (W) could fulfill these requirements for plasma facing components of fusion power plants. A method developed by SNL to enhance the thermal and dimensional stability of W requires depositing a thin coating on the surface of dendritic W armors for IFE plasma facing components. This paper examines the waste disposal rating (WDR) associated with the activation of thin coatings of Re and Mo on the ARIES-ACT W-based divertor. Our results indicate that Re coatings must be limited to fewer than 30 μm in order to classify the Re/W-based divertor as low-level waste (LLW). Mo coatings that are larger than a few microns thick exceed the LLW disposal limit. It is recommended that, in addition to limiting the Mo thickness to 25 μm, natural Mo should be tailored to remove the Mo-94, Mo-98, and Mo-100 isotopes in order to reduce the WDR of the Mo/W-based divertor below the LLW disposal limit. If the isotopic tailoring process is inefficient or costly, SNL could focus their effort on the further development of the Re dendrite coating while Mo experiments would be regarded as a comparative study only.