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TREATMENT AND CONDITIONING OF RADIOACTIVE GRAPHITE FROM NUCLEAR INSTALLATIONS

Objective

The objective of the laboratory-scale investigations is the development of chemical processes for the treatment of radioactive graphite for its safe storage. It consists of:

previous extraction of radionuclides (mainly tritium) to decrease the radioactivity of graphite;
fixation of radionuclides (mainly C-14) to avoid their leaching during the storage of graphite;
impermeabilization of graphite by metal coating for its transport and storage.

Extraction of the radionuclides with chemical agents will be done before the metallising process for fixation, in order to minimize leaching of radioactive products during storage, followed by standard leaching tests. The radioactive graphite will be procured from the experimental reactor JEN-1 and the gas-cooled reactor Vandellos-I.
The objective of the laboratory scale investigations is the development of chemical processes for the treatment of radioactive graphite for its safe storage. It consists in:
previous extraction of radionuclides (mainly tritium) to decrease the radioactivity of graphite; fixation of radionuclides (mainly carbon-14) to avoid their leaching during the storage of graphite; impermeabilisation of graphite by metal coating for its transport and storage.

Graphite has been characterized with respect to organic impurities, surface characteristics and radionuclides concentration. The radioactive characterization of graphite sleeves shows the presence of tritium, carbon-14, and cobalt-60 and the small amounts of caesium-137, caesium-134 and europium-154. The presenc of the different radionuclides in the sleeves is mainly due to their contamination in the swimming pool of the reactor. Several straight and cyclic hydrocarbon chains have been detected on inactive graphite samples. It could explain the presence of tritium in the radioactive graphite fixed in the hydrocarbons. This radionuclide can probably be desorbed by passing a wet air stream. Water adsorption and desorption kinetic in graphite has been studied in order to optimize the process. The metallization of graphite surface by electrolysis using 70 different methods has been studied, 9 of them showing the highest efficiency have been selected. Characterization of metallized surface has been done by electronic and optic microscopy and other techniques. Leaching and corrosion tests on active and inactive graphite samples have been started.
WORK PROGRAMME

1. Removal and/or fixation of radionuclides

1.1. Investigations on radioactive and inactive sample structure and texture using different analysing techniques. (all)
1.2. Testing of appropriate chemical agents on samples with regard to their possible decontamination and/or immobilization features. (UDA)
1.3. Study of radionuclide removal, mainly tritium.
1.4. Study of radionuclide fixation.
1.5. Characterization of treated samples using methods from subtask 1.1.

2. Metal coating of graphite by ionic deposition.

2.1. Characterization of samples similar to 1.1. (all)
2.2. Performance of process parameter studies for metal coating applications on inactive samples. (all)
2.3. Chemical modification of radioactive surfaces. (CIEMAT)
2.4. Metallization of inactive samples. (all)
2.5. Metallization of radioactive samples. (CIEMAT)
2.6. Characterization of the treated samples concerning chemical properties and thickness of the metal layer, porosity of the surface etc. (all)

3. Leaching experiments with the metallized specimen. (CIEMAT)

4. Assessment of results and conclusions.

Funding Scheme

CSC - Cost-sharing contracts
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Coordinator

CENTRO DE INVESTIGACIONES ENERGETICAS, MEDIAMBIENTALES Y TECNOLOGICAS
Address
22,Avenida Complutense 22
28040 Madrid
Spain

Participants (1)

UNIVERSITY OF ALICANTE
Spain
Address
99,Carretera De San Vicente S/n
03080 Alicante