The high 88.5% implied probability for "No" on a U.S. Nuclear Regulatory Commission combined license (COL) for a new nuclear reactor by December 31, 2026, stems primarily from the sequential and technically rigorous nature of licensing, even after recent streamlining. While the NRC issued its first advanced reactor construction permit to TerraPower's Natrium project in March 2026 and finalized the risk-informed Part 53 framework to target 18-month reviews, no full COL authorizing both construction and commercial operation of an entirely new design has been granted as of late August. DOE-authorized test reactors reached criticality under separate pathways, but these bypass standard NRC commercial licensing. Ongoing reviews for designs like X-energy's Xe-100 and Oklo's Aurora face remaining safety evaluations, hearings, and first-of-a-kind inspections that traders view as unlikely to conclude in the remaining months.