Plutonium(III) Chloride
Properties
| State | Solid |
| Color | Emerald-green to blue-green |
| Solubility | Very soluble in water; soluble in ethanol, LiCl/KCl molten-salt eutectic |
| Melting Point | 760 °C |
| Boiling Point | 1767 °C |
About Plutonium(III) Chloride
Plutonium(III) chloride (PuCl3, 350.35 g/mol) is the emerald-green to blue-green hexagonal halide that anchors most of the practical aqueous-and-melt chemistry of trivalent plutonium. It crystallizes in the UCl3 structure type — each Pu(III) sits in a 9-coordinate tricapped trigonal prism of chloride — the same lattice you find in the trivalent lanthanide trichlorides, which is why so much Pu(III) coordination work uses lanthanide analogs as cold stand-ins. Where thorium and uranium chemistry are dominated by the +4 state, plutonium is happy to sit at +3 under non-oxidizing conditions, and PuCl3 is the workhorse starting material for that oxidation state. The single most important use is in pyroprocessing, the non-aqueous reprocessing scheme developed at Argonne for sodium-cooled fast reactor fuel: PuCl3 dissolved in a LiCl/KCl eutectic at 500 °C provides the electrolyte from which plutonium electrodeposits onto a solid cathode, while uranium co-deposits on a parallel liquid cadmium cathode. The flowsheet was demonstrated end-to-end on Experimental Breeder Reactor II spent fuel at Idaho National Laboratory in the late 1990s and remains the reference fuel-cycle technology for Generation IV fast-reactor concepts.
Where you'll encounter it
If you've worked in an actinide glove box at Argonne or Idaho National Lab, you've handled PuCl3 — the green color of the salt and of its molten LiCl/KCl solutions is how operators visually confirm the bath is loaded and Pu(III) is the dominant species. In a pyroprocessing demonstration cell, you can watch the bath color deepen as PuCl3 builds up during the anodic dissolution step, then lighten as plutonium plates out onto the steel cathode. The same compound shows up in nuclear-waste migration research: PNNL and LANL groups use PuCl3 as the starting point for Pu(III) speciation studies under groundwater conditions, since reducing or strongly complexing aquifers can stabilize Pu(III) over the +4 state usually assumed in performance assessments. It is also the reference Pu(III) substrate for testing CMPO and HDEHP extractants meant to separate trivalent actinides from chemically similar lanthanide fission products.
Common Uses
- Active species in LiCl/KCl eutectic molten-salt electrorefining of metallic fast-reactor fuel at 500 °C
- Feedstock for electrowinning Pu metal onto solid cathodes in the EBR-II pyroprocessing flowsheet
- Source of Pu(III) in coordination studies with crown ethers, cryptands, and 1,10-phenanthroline-class ligands
- Reference phase for Pu(III) speciation work on nuclear-waste groundwater migration at PNNL and LANL
- Test substrate for CMPO and HDEHP solvent extractants in trivalent-actinide/lanthanide separation R&D
Safety Information
Pu-239 alpha emitter (specific activity 62 mCi/g); inhalation ALI ~30 nCi for soluble Pu compounds (DOE 10 CFR 835). Hygroscopic; hydrolyzes in humid air to release HCl and form insoluble PuOCl. SPECIAL NUCLEAR MATERIAL under DOE/NRC accountability — handled only in dry inert-atmosphere alpha glove boxes with HEPA exhaust. GHS: H301 (acute toxicity Cat 3 ingestion), H314 (corrosive Cat 1B), H350 (carcinogenicity Cat 1A from alpha radiotoxicity), H400 (very toxic to aquatic life).
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.