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DECONTAMINATION OF PU CONTAINING INCINERATOR ASHES.

Objective

THE INCINERATION OF PU CONTAINING WASTE (PCW) IS ONE OF THE MOST PROMISING TREATMENT OPTIONS BECAUSE OF ITS HIGH VOLUME REDUCTION FACTOR. THE ARISINGS OF PU CONTAINING INCINERATION ASHES EXPECTED TO INCREASE IN THE NEAR FUTURE. AS THE PU CONTENT IN THESE ASHES MAY REACH HIGH VALUES (UP TO 10 WT.%) THEIR DISPOSAL COULD BECOME PROBLEMATIC IN THE LIGHT OF DISPOSAL CRITERIA SET UP BY SAFETY AUTHORITIES. LIKEWISE, IT MAY BE VALUABLE TO RECOVER PU FROM THESE ASHES FOR RECYCLING PURPOSES IN LWRS. THEREFORE, THE DEVELOPMENT OF AN EFFECTIVE PU RECOVERY PROCESS APPEARS WORTHWILE.

THE MAIN ACTIVITIES OF THE PROJECT ARE:
- ANALYSIS OF LITERATURE DATA ON PU RECOVERY PROCESSES.
- EVALUATION OF THE EXPERIMENTAL RESULTS OF THE ALONA PLANT FOR DECONTAMINATION OF THE MARCOULE ALPHA ASHES.
- EXPERIMENTAL ACTIVITIES FOR DEVELOPING A SUITABLE PROCESS.
- PRELIMINARY COST EVALUATION FOR A PLANT PROTOTYPE.
The sulphuric acid nitric acid system proved to be valuable in principle for the recovery of plutonium from alpha-emitter bearing incineration residues. However, it appeared that all of the concentrated sulphuric acid used to digest plutonium dioxide had to be replaced after a throughput of as little as 0.6 kg ashes per litre because the plutonium dioxide had been saturated with dissolved ash constituents. To avoid this drawback most of the soluble companion substances must be leached out of the ashes before digestion. Nitric acid was studied as a candidate solvent since it is being used anyway to oxidise the carbon still present in the ashes.
This report describes experimental investigations into the dissolution of plutonium dioxide occurring in inactive and alpha-emitter bearing incineration residues, with attention concentrated on pretreatment with nitric acid. Finally, a preliminary proposal for a methodology is presented on the basis of the results obtained and a simplified flowsheet is discussed.
2.3. LITERATURE SURVEY.
2.4. EVALUATION OF THE EXPERIMENTS PERFORMED IN THE ALONA PLANT.
2.5. EXPERIMENTS.
2.5.1. CHARACTERIZATION OF THE INCINERATOR ASHES FROM KFK AND MARCOULE.
2.5.2. ASHES PRETREATMENT: EFFECT OF PARTICLE SIZE ON LEACHABILITY OF ASHES.
2.5.3. PU RECOVERY FROM ASHES: INFLUENCE OF LEACHING TEMPERATURE, LEACHING REAGENT, LEACHING REAGENT/ASH RATIO AND FURNACE TEMPERATURE DURING INCINERATION ON THE LEACHABILITY OF THE ASHES AND THE DISSOLUTION OF PUO2
2.5.4. PU PURIFICATION: DEVELOPMENT OF A PURIFICATION PROCESS FOR PU FROM LEACHING SOLUTIONS WITH A VIEW TO PU RECYCLING
2.5.5. SECONDARY WASTE: EVALUATION OF THE SECONDARY WASTE PRODUCED DURING PU DISSOLUTION/PURIFICATION AND PROPOSAL FOR A WASTE TREATMENT PROCESS
2.6. DRAWING UP FLOWSHEETS: ON THE BASIS OF THE EXPERIMENTAL RESULTS FLOWSHEETS HAVE TO BE DRAWN UP FOR THE TREATMENT OF ALPHA-BEARING ASHES
2.7. COST EVALUATION: BASED ON A SIMPLIFIED FLOW DIAGRAM, A PRELIMINARY COST EVALUATION WILL BE PERFORMED FOR A PROTOTYPE FACILITY.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Forschungszentrum Karlsruhe Technik und Umwelt GmbH
Address

76021 Karlsruhe
Germany