The State of the Nuclear Energy Industry 2020, page-20

Lewy is right, in that the big brains are needed to explain how a travelling wave reactor uses fuel and what type. Although I believe the tech is complimentary with silex, in particular Paducah tails. Bill actually has a photo of the Paducah tails containers in his twr promo video as the fuel source.
The basics of how it would work in my mind is that Silex would run the tails renriching for conventional reactors that will be around for at least 60 years as well as the small modular reactors from other vendors that will use hi assay low enriched uranium. The silex waste tails would then become the bulk of Mr Gates fuel supply with some other goodies thrown in. A perfect fit for both companies and I believe ge as well