THE DECISION OF RADIOACTIVE WASTE DISPOSAL IN DEEP CLAY FORMATIONS CANNOT BE TAKEN UNTIL A FULL UNDERSTANDING HAS BEEN ACQUIRED OF THE IN SITU WATER RADIOELEMENT TRANSFER PHENOMENA.
THE FIRST STAGE OF THE INVESTIGATION CONSISTS IN TAKING CORE SAMPLES AND STUDYING THEIR PROPERTIES IN THE LABORATORY. THE DIFFICULTY OF THIS APPROACH RESIDES IN THE NEED TO TAKE AND STORE THE SAMPLES WITHOUT CHANGING THEIR INTRINSIC PROPERTIES.
THE GENERAL PURPOSE OF THIS STUDY IS THUS THE DEVELOPMENT OF METHODOLOGY WHICH CAN BE USED TO ESTABLISH THE MODES OF ACQUISITION OF THE MECHANICAL AND CHEMICAL IN SITU PROPERTIES REQUIRED FOR EVALUATION OF TRANSFER PHENOMENA: LISTING OF THE PROPERTIES TO BE ACQUIRED AND THE DISTURBANCES CAUSES BY SAMPLE TAKING, SELECTION OF METHODS OF CORE DRILLING, CORE HANDLING AND PACKAGING, PREPARATION OF SAMPLES AND ANALYSIS PROCEDURES.
THE APPROACH IS ESSENTIALLY BASED ON THE EXPERIENCE ACQUIRED BY CEN/SCK MOL WITH BOOM CLAY, THE OBSERVATIONS CARRIED OUT BY ANDRA ON THE BASIS OF DEEP CLAY CORE SAMPLE TESTS AND THE METHODS DEVELOPED BY THE CEA FOR STUDYING CLAY MATERIALS (CONTRACTS FI1W 0031 AND 0061).
THE SECOND STAGE WILL CONSIST OF VALIDATING THE METHODOLOGY BY CARRYING OUT CORE DRILLING AT THE MOL SITE USING THE PREVIOUSLY ESTABLISHED SPECIFICATIONS, THEN COMPARING THE RESULTS OF ANALYSIS OF THE CORE SAMPLES WITH THOSE OF IN-SITU TESTS CARRIED OUT IN THE UNDERGROUND LABORATORY, UNDER A PROTOCOL WHICH REMAINS TO BE ESTABLISHED.
Knowledge of deep formations for the disposal of radioactive waste requires in situ measurements or laboratory measurements on samples of the site material. In the case of clay massifs, the taking and sampling of cores is particularly difficult. A methodology which allows the suppression or reduction of the factors perturbing these operations is needed. The most suitable materials and techniques were selected from a study of clay coring and conservation methods. These were used for a series of core samples taken at Mol in Belgium. Subsequently, permeability measurements were carried out in the laboratory on samples from vertical drilling and were compared with in situ measurements. The latter were taken by horizontal drillings from the gallery of the underground facility HADES at Mol. There is good overall agreement between the results of both typess of measurements.
1. LISTING OF THE PHYSICO-CHEMICAL PARAMETERS TO BE ACQUIRED FOR THE PURPOSE OF ASSESSING TRANSFER PHENOMENA IN CLAY FORMATIONS AND THE DISTURBANCES OF THE CLAY BY THE SAMPLING METHOD.
2. SELECTION OF METHODS OF TAKING, PACKAGING AND PRESERVING SAMPLES.
ESTABLISHMENT OF EXPERIMENTAL PROCEDURES. THEIR IMPLEMENTATION AT THE MOL SITE IN BELGIUM.
3. COMPARISON OF IN SITU AND LABORATORY READINGS. VALIDATION OF THE METHODOLOGY.