PUREX

PUREX
source
Name	PUREX
Type	Chemical separation process
Developer	Manhattan Project scientists; Argonne National Laboratory contributions
Introduced	1940s
Primary use	Reprocessing of irradiated nuclear fuel
Feedstock	Irradiated uranium/plutonium fuel from light-water reactors, fast breeder reactors
Products	Recovered uranium, recovered plutonium
Country	United States; deployed in United Kingdom, France, Russia, Japan, India

PUREX

PUREX is an industrial solvent-extraction method for separating uranium and plutonium from irradiated nuclear fuel using tributyl phosphate in a hydrocarbon diluent. Developed in the 1940s for large-scale recovery of fissile materials from irradiated targets and fuel, PUREX has been deployed in national fuel-cycle programs at facilities such as the Hanford Site, Sellafield, and the La Hague complex. The process underpins civil reprocessing campaigns tied to programs involving light-water reactor fleets, fast breeder reactor development, and strategic stockpile management.

Overview

PUREX stands for Plutonium Uranium Redox EXtraction and is a liquid–liquid extraction flowsheet used to partition uranium and plutonium from fission products and minor actinides. As a cornerstone of reprocessing strategies developed during the Manhattan Project and refined at institutions like Argonne National Laboratory and Los Alamos National Laboratory, PUREX enabled campaigns associated with the Manhattan Project production reactors at the Hanford Site and later civilian programs in France and United Kingdom. Internationally, PUREX installations have interfaced with national programs at organizations such as Commissariat à l'énergie atomique et aux énergies alternatives (CEA), United Kingdom Atomic Energy Authority, and Rosatom enterprises. The method supports fuel-cycle options connected to the Closed nuclear fuel cycle concept and programs like BREEDER reactor development and plutonium disposition treaties.

Process and Chemistry

The PUREX flowsheet uses an aqueous nitric acid phase containing dissolved irradiated fuel and an organic phase of tributyl phosphate (TBP) diluted in kerosene or a similar hydrocarbon. Uranium and plutonium are extracted from the aqueous phase into the TBP phase through complexation reactions; plutonium is typically converted between oxidation states using redox reagents such as hydrazine or ferrous sulfamate to control its distribution. Subsequent scrubbing and strip stages employ reagents like uranyl nitrate adjustments and reducing agents to selectively back-extract plutonium and uranium. The chemistry exploits coordination of actinyl ions to phosphoryl oxygens on TBP, while fission products such as cesium-137, strontium-90, and lanthanides remain largely in the aqueous raffinate. Radiolysis, solvent degradation, third-phase formation, and cross-contamination with transuranics such as americium and curium are key chemical engineering concerns addressed by process control strategies developed by institutions like Oak Ridge National Laboratory and industrial partners including Areva (now Orano).

Industrial Implementation and Facilities

Commercial and military-scale PUREX plants were constructed at sites including the Hanford Site, Savannah River Site, Windscale (now Sellafield), La Hague, Rokkasho Reprocessing Plant, and Russian facilities at Mayak. Designs range from early batch units to continuous mixer-settler cascades and pulse column arrangements used in modern facilities. Companies and agencies such as BNFL, Areva/Orano, UKAEA, and national utilities have integrated PUREX units with interim storage systems like spent-fuel pools and dry cask storage, and with downstream conversion plants producing mixed oxide fuel for use in commercial nuclear reactors. International projects, overseen by bodies such as the International Atomic Energy Agency, have coordinated safeguards, commissioning, and decommissioning of PUREX plants, with decontamination and decommissioning projects at legacy sites involving contractors experienced in nuclear remediation.

Safety, Environmental and Proliferation Issues

PUREX operations concentrate fissile materials, creating proliferation-sensitive streams of separated plutonium and enriched uranium that intersect with non-proliferation regimes such as the Treaty on the Non-Proliferation of Nuclear Weapons and safeguards applied by the International Atomic Energy Agency. Radiological hazards from high-activity fission products like cesium-137 and strontium-90, and chemical hazards from nitric acid and organic solvents, necessitate engineering controls, containment, and emergency planning exemplified at regulated facilities like Savannah River Site and La Hague. Environmental incidents at reprocessing sites have driven regulatory responses in jurisdictions governed by agencies such as the Nuclear Regulatory Commission and national ministries of energy; remediation of legacy contamination has involved programs linked to the Comprehensive Environmental Response, Compensation, and Liability Act in the United States and national cleanup authorities in Russia and France. Plutonium disposition efforts, including immobilization and fabrication of mixed oxide fuel under bilateral initiatives such as agreements between United States and Russia, reflect policy responses to proliferation concerns.

Historical Development and Alternatives

PUREX evolved from wartime separations chemistry used during the Manhattan Project and was scaled at sites like Hanford Site and Savannah River Site for both weapons and civil purposes. Postwar civilian uses proliferated through reactors associated with utilities such as Électricité de France and state programs in Japan and India. Alternative aqueous processes include the UREX and TRUEX variations designed to limit plutonium separation or remove minor actinides, while pyroprocessing approaches developed at Argonne National Laboratory and by Electrorefining programs in South Korea and Japan present non-aqueous alternatives aimed at proliferation resistance and treatment of metallic fuels. Research into novel extractants—such as diamide ligands and borated solvents—and partitioning and transmutation strategies pursued in initiatives like the European Commission frameworks and national research programs continue to influence policy decisions regarding PUREX deployment, decommissioning, and replacement.

Category:Nuclear fuel reprocessing