Small modular reactors (SMRs) are on the rise, especially because of their expected modularity, shorter construction time, and low capital costs compared to large Generation III nuclear reactors; they are also likely to be more uranium intensive. In such case, we studied the impact of SMR development on uranium resources and its effect on fast reactor deployment using GRUS, a system dynamic-based numerical tool. Based on nuclear energy demand scenarios up to the year 2150, we show the evolution of the nuclear fleet by reactor type, along with the associated uranium consumption. In all our scenarios and even without SMRs, the global development of nuclear energy in 2150 already exceeds conventional uranium resources. On top of it, in a nuclear fleet made of EPRs and FRs, SMRs could lead to an additional uranium requirement of about 25%. Furthermore, the non-reprocessing of SMRs spent fuels would reduce plutonium stocks, what would impact the deployment of fast reactors and cause an additional demand of natural uranium of more than 10%. Finally, the SMRs, by accelerating the use of uranium resources, increase its cost and bring forward the date of competitiveness of fast reactors from a few years to several decades. The results indicate that to ensure the sustainability of nuclear power with SMRs, a particular attention must be paid during the design phase of such modular reactors to uranium consumption and fuel reprocessing.