The dataset's assignee ranking (rendered separately on this page) shows filing concentrated among a handful of national nuclear programmes and major reactor vendors, including entities tied to France's state-backed fuel-cycle programme and established reactor manufacturers such as Toshiba and Westinghouse. Several of these top assignees show zero filings in the most recent tracked year, which reflects the dataset's broader decline from its 2020 peak rather than any single company exiting. Because publication lags filing by about 18 months, current-year rankings should be treated as provisional.

Filing peaked at 27 records in 2020 and had fallen to 11 by the 2022 midpoint, indicating the field is past its filing peak rather than still expanding. This pattern is consistent with a technology area where the core storage and reprocessing mechanisms were claimed in earlier years, leaving recent activity more incremental. The 2025-2026 figures will revise upward as later applications publish, but the overall trajectory is flat-to-declining rather than growing.

US9666315B2, assigned to Toshiba, covers a spent fuel reprocessing method that dissolves fuel in nitric acid and separates nuclides by solvent extraction, with a specific electrolytic valence-adjustment step that manipulates plutonium's oxidation state before a nuclide separation stage using a uranium-selective extraction solvent. It does not block solvent extraction reprocessing generally — it blocks the specific combination of electrolytic valence control timed and parameterized as claimed. Alternative reprocessing routes that adjust valence by other chemical means, or that omit the electrolytic step entirely, sit outside its claim scope.

Relative to the 387 records classified under G21C (nuclear reactors) and 268 under G21F (radiation shielding), separation and metallurgical chemistry classes such as B01D, C22B, C25C and B04B are thinly represented, together covering well under a fifth of the corpus. That gap suggests process chemistry — particularly centrifugal extraction hardware, electrolytic valence adjustment, and vitrification matrix formulation — carries lower filing density than the storage and shielding hardware around it. A first claim in these branches has more room to establish novel ground than one filed against the crowded G21C or G21F classes.

The United States leads receiving offices with 154 filings, followed by Japan at 90 and the European Patent Office at 77; the United Kingdom and the WIPO PCT route each sit in the 50s, while China trails at 16. This spread tracks where fuel storage and reprocessing infrastructure is concentrated rather than reactor fleet size alone, since countries with large operating reactor fleets but limited domestic reprocessing capacity file comparatively less in this specific dataset.