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SEPARATION OF CONTAMINATED CEMENT STONE AND NON-CONTAMINATED CONCRETE AGGREGATES.

Obiettivo

IN A NUCLEAR INSTALLATION, CONCRETE IN VARIOUS BUILDINGS STRUCTURES MAY BECOME CONTAMINATED DURING OPERATION. WHEN THE INSTALLATION IS WITHDRAWN FROM SERVICE AND EVENTUALLY DISMANTLED, THE CONTAMINATED CONCRETE MUST BE CONDITIONED AND DISPOSED OF AS RADIOACTIVE WASTE.

PRELIMINARY RESEARCH CARRIED OUT BY THE CONTRACTOR INDICATED THAT THE CONTAMINATING SUBSTANCES PENETRATE ONLY INTO THE POROUS CEMENT ATONE AND NOT INTO THE MOSTLY IMPERMEABLE AGGREGATES.

THE OBJECTIVES OF THIS RESEARCH PROGRAMME ARE TO CHECK THE BEFORE-MENTIONED INDICATION AND, IF IT IS CONFIRMED, TO DEVELOP, ON LABORATORY SCALE, A PROCESS FOR SEPARATING THE CONSTITUENTS OF CONTAMINATED CONCRETE INTO A CONTAMINATED AND A NON-CONTAMINATED PART IN ORDER TO REDUCE THE AMOUNT OF RADIOACTIVE WASTE.
Separating the contaminated parts from the noncontaminated parts from decommissioned nuclear facilities would reduce the amount of contaminated concrete. It is shown that the radioactive contamination is mostly in the cementstone. Normally the cementstone takes about 30% of the total concrete volume.

A separation procedure composed of a combination of milling and thermal shock has been assessed. Both a cold and a hot thermal shock were investigated. Both the cold and hot thermal shock in combination with milling were not able to separate the cementstone from the larger aggregates completely. However, the cementstone seems to be almost completely removed from concrete of low nominal grain size by the combination of cold thermal shock and milling, while it seems to be almost completely removed from concrete of high nominal grain size by the combination of hot thermal shock and milling. After both methods a layer of cementstone was still visible on the aggregates. A washing procedure with water and nitric acid was investigated. Washing followed by a nitric acid treatment removed 2% by weight of cementstone.
B.1.- CHECKING OF THE HYPOTHESIS THAT ONLY CEMENT STONE IS CONTAMINATED BY ANALYSIS OF CONTAMINATED CONCRETE SAMPLES FROM VARIOUS NUCLEAR INSTALLATIONS.

B.2.- LABORATORY-SCALE DEVELOPMENT OF A SEPARATION PROCESS BY EG THERMAL SHOCK AND SCREENING SHEET ON SAMPLES OF VARIOUS TYPES OF RELEVANT CONCRETE, INCLUDING CONTAMINATED SAMPLES AS FAR AS AVAILABLE.

B.3.- DEVELOPMENT OF A WASHING PROCESS FOR CONTAMINATIONN-CONTAINING AGGREGATES (IF ANY), BASED ON AN INVESTIGATION OF VARIOUS WASHING FLUIDS.

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Meccanismo di finanziamento

CSC - Cost-sharing contracts

Coordinatore

Business Unit of TNO Built Environment and Geosciences
Contributo UE
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Indirizzo
Van Mourik Broekmanweg 6
2628 XE DELFT
Paesi Bassi

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