UWFDM-1382 Activation of W-Based Divertors with Thin Re and Mo Coatings for Fusion Applications

There is a considerable interest in low activation and high heat resistant materials for fusion applications. Tungsten (W) would fulfill these requirements for plasma facing components of future fusion power plants. A novel method developed by SNL to enhance the thermal and dimensional stability of W requires depositing materials such as Re and Mo as a thin coating on the surface of dendritic W armors for IFE and MFE plasma facing components. Waste management issues arise due to the transmutation of Re and Mo in the harsh 14 MeV neutron environment created by fusion reactions. In this report, the waste disposal rating (WDR) associated with the activation of thin coatings of Re and Mo on the ARIES-ACT W-based divertor is examined. Our results indicate that Re coatings must be limited to fewer than 30 microns 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. Further analysis on natural Mo was performed to examine the effect of isotopic tailoring on WDR. The transmutation of Mo-94, Mo-98, and Mo-100 contributes to the majority of the radioactivity produced during Mo activation. It is recommended that, in addition to limiting the Mo thickness to 25 microns, 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.