C. J. Maher

National Nuclear Laboratory, UK | NNL

EURO-GANEX is an innovative hydrometallurgical process for the group separation of transuranic actinides from future spent nuclear fuels. A flowsheet test of a process upset (or ‘maloperation’) has been carried out involving the reduction in the concentration of the scrub acid feed to the extract-scrub contactors. The experimental test was complete...

The production of ²³⁸Pu from ²³⁷Np, to the specifications required for space flight, requires the separation of plutonium from neptunium and a range of fission products. The valuable neptunium is then recycled into targets for further irradiation. At Oak Ridge National Laboratory (ORNL), a solvent extraction process has been developed to separate n...

Over 80 heat treatment experiments have been made on samples of chloride-contaminated plutonium dioxide retrieved from two packages in storage at Sellafield. These packages dated from 1974 and 1980 and were produced in a batch process by conversion of plutonium oxalate in a furnace at around 550 °C. The storage package contained a poly(vinyl chlori...

In recent years, NNL has investigated the potential for advanced plutonium and minor actinide bearing fuels, in particular in fast reactor fuel cycles (both SFR and GFR) as well as the use of advanced production technologies. R&D has been undertaken in order to address key challenges in NNL internal, UK national and European programmes including FP...

In recent years, the National Nuclear Laboratory (NNL) has investigated the potential for advanced plutonium and minor actinide bearing fuels, in particular in fast reactor fuel cycles (both sodium-cooled fast reactors [SFR] and gas-cooled fast reactors [GFR]) as well as the use of advanced production technologies. R&D has been undertaken in order...

One of the most successful uses of nuclear energy, other than nuclear fission reactors, is the use of radioisotopes to provide a simple source for heat and electrical power in space applications. The alpha decay heat from suitable radioisotopes can be harnessed to heat instrumentation and generate electricity through thermoelectric generators. With...

The dissolution of uranium or uranium-plutonium carbide fuel in nitric acid leads to ~50% carbon evolved as carbon dioxide, the remainder remains in the solution as soluble organics. These dissolved organic molecules interfere with the solvent extraction of uranium and plutonium by complexing to the actinide ions and decreasing the efficiency of th...

Electrical power sources used in outer planet missions are a key enabling technology for data acquisition and communications. State–of-the-art power sources generate electricity from alpha decay of 238Pu via thermoelectric conversion. However, production of 238Pu requires specialist facilities including a nuclear reactor, a source of 237Np for targ...

Two potential methods for decomposing organic ligands in nitric acid have been studied using acetic acid and diethylenetriaminepentaacetic acid (DTPA) as examples; these methods were oxidation by nitric acid at elevated temperatures (70-110°C) and electrochemical oxidation, both direct and mediated electrochemical oxidation. Based on total carbon m...

A new hydrometallurgical grouped actinide extraction process has been developed to separate the transuranic actinide ions from dissolved spent fuel solution (after an initial uranium extraction cycle). This “EURO-GANEX” process is aimed towards the homogeneous recycling of plutonium and minor actinides in a future closed fuel cycle. The separation...

Electrical power sources used in outer planet missions are a key enabling technology for data acquisition and communications. State–of-the-art power sources generate electricity from alpha decay of ²³⁸Pu via thermoelectric conversion. However, production of ²³⁸Pu requires specialist facilities including a nuclear reactor, a source of ²³⁷Np for targ...

A novel separation process for recovering transuranic actinides has been tested in centrifugal contactors using a surrogate feed solution. This “TRU-SANEX” (transuranic element-selective actinide extraction) process uses solvent extraction between nitric acid and an organic phase containing 0.2 mol/L N,N,N’,N’-tetraoctyl diglycolamide with 0.5 mol/...

The rate of decomposition of oxalic acid in strong nitric acid solutions increases with increasing acidity and temperature with the rate of reaction following pseudo-first-order kinetics with respect to oxalic acid. The order of nitric acid on the overall reaction has been shown to be 2.7, although this result should be treated with some caution du...

Future generations of spent fuel could be greatly different in form and chemical composition when compared to current commercial reactor fuels. This, combined with potential future changes in the management of gaseous radionuclides, could necessitate substantial changes to the headend of future fuel reprocessing plants. In this context, the science...

The development of advanced separation processes for spent nuclear fuel reprocessing and minor actinide recycling is an essential component of international R&D programmes aimed at closing the nuclear fuel cycle around the middle of this century. Whilst both aqueous and pyrochemical processes are under consideration internationally, neither option...

NNL is involved in the development of reprocessing and Minor Actinide (MA) recycling processes essential for the integration of sustainable closed nuclear fuel cycles into future balanced energy portfolios. To this end, NNL are part of the Safety of ACtinide SEparation proceSSes (SACSESS) and Advanced fuelS for Generation IV reActors: Reprocessing...

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A flowsheet for a novel GANEX (Grouped ActiNide EXtraction) process has been tested in a spiked flowsheet trial in a 32 stage plutonium-active centrifugal contactor rig with a simulant feed that contained 10 g/L plutonium as well as some fission products and other transuranic actinides. The solvent system used was a combination of 0.2 mol/L N,N,N’,...

The preferred European alternative of 241Am for use in future Radioisotope Power Systems (RPS), and the issues that will need to be addressed has continued with the development of a conceptual flowsheet to be used for production of 241Am. Current work is now focused on underpinning the conceptual flowsheet, using aged plutonium in NNL's PuMA labora...

The focus of this paper is the chemistry of mixed uranium plutonium oxide (MOx,) in nitric acid. An overview of dissolution chemistry is discussed by comparing the differences in the dissolution characteristics of uranium and plutonium oxides. An overview of batch dissolution experiments, studying the dissolution chemistry of high surface area MOx...

The solvent combination N,N,N'N'- tetraoctyl diglycolamide (TODGA)/tributyl phosphate (TBP)/odourless kerosene (OK) is examined as a potential solvent system for a Grouped Actinide Extraction (GANEX) process to separate all of the actinides from fission products when reprocessing spent nuclear fuel. A series of solvent extraction batch experiments...

Formo‐ and aceto‐hydroxamic acids are very effective reagents for stripping Pu(IV) ions from a tri‐butyl phosphate phase into nitric acid. Distribution data for Pu(IV) in the presence of these hydroxamate ions have been obtained and trends established. The affinity of aceto‐hydroxamic acid for Pu(IV) ions and its selectivity over U(VI) ions is demo...

As any future spent fuel treatment facility is likely to be based on intensified solvent extraction equipment it is important to understand the chemical and mass transfer kinetics of the processes involved. Two candidate minor actinide separations processes have been examined through a programme of modeling and experimental work to illustrate some...

Simple hydroxamic acids are shown to be useful reagents for the separation of Np and Pu from U within simplified, single cycle Purex flowsheets. They are compatible with the use of centrifugal contactors and laboratory scale flowsheet trials with aceto-hydroxamic acid have demonstrated high actinide recoveries and decontamination factors on product...

In 30% TBP/OK Np(V) is unstable and disproportionates to Np(IV) and Np(VI). Np(V) readily coordinates to Np(IV) in solution to form a '' cation - cation '' complex by bonding through an axial oxo group on Np(V). The rate of disproportionation in 30% TBP/OK is > 500 times that in aqueous solution.

To support either the continued operations of current reprocessing plants or the development of future fuel processing using hydrometallurgical processes, such as Advanced Purex or UREX type flowsheets, the accurate simulation of Purex solvent extraction is required. In recent years we have developed advanced process modeling capabilities that util...

Actinide elements and their chemistry have a significant number of applications. Bringing together contributions from the leading experts in the field, Recent Advances in Actinide Science covers six main topics: * Analysis, the environment and biotransformations * Coordination and organometallic chemistry * Heavy elements * Nuclear fuels, materials...

Actinide elements and their chemistry have a significant number of applications. Bringing together contributions from the leading experts in the field, Recent Advances in Actinide Science covers six main topics: * Analysis, the environment and biotransformations * Coordination and organometallic chemistry * Heavy elements * Nuclear fuels, materials...

The reprocessing of nuclear fuel using PUREX-based solvent extraction has been undertaken in the UK on an industrial scale for over forty years. Current research includes the development of modified PUREX-style flowsheets for processing ever-increasing plutonium content fuels including MOX, fast reactor and even experimental and legacy fuels. Herei...

Significant improvements are required in the Purex process to optimise it for Advanced Fuel Cycles. Two key challenges we have identified are, firstly, developing more efficient methods for U/Pu separations especially at elevated Pu concentrations and, secondly, improving recovery, control and routing of Np in a modified Purex process. A series of...

In order to recycle potentially valuable uranium and plutonium, the Purex process has been successfully used to reprocess spent nuclear fuel for several decades now at industrial scales. The process has developed over this period to treat higher burnup fuels, oxide as well as metal fuels within fewer solvent extraction cycles with reduced waste ari...