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THE ROLE OF COLLOIDS IN THE TRANSPORT OF RADIONUCLIDES IN GEOLOGICAL FORMATION

Objective

RECENT RESEARCH HAS EMPHASISED THE POTENTIAL IMPORTANCE OF COLLOIDS IN THE MIGRATION OF RADIONUCLIDES FROM A WASTE REPOSITORY INTO THE GEOSPHERE /1,2,3/. THUS, IF RADIONUCLIDES ARE ASSOCIATED WITH COLLOIDS THEIR FATE MAY BE DIFFERENT FROM THAT OF SIMPLE IONIC SPECIES IN SOLUTION. IN PARTICULAR, DEPENDING ON THE SIZE AND CHARGE OF COLLOID SPECIES RETENTION EFFECTS MAY OCCUR DUE TO FILTRATION, OR IN CONTRAST THERE MAY BE ENHANCED MIGRATION DUE TO DIFFERENCES IN FLOW MECHANISMS AND A REDUCTION IN THE INTERACTION WITH MINERAL SURFACES.
OUR OBJECTIVE HERE IS TO IMPROVE THE UNDERSTANDING OF THE ROLE OF COLLOIDS IN RADIOACTIVE WASTE DISPOSAL. THIS IS BEING ACHIEVED FIRSTLY BY DETAILED CHARACTERISATION OF NATURAL COLLOIDS DERIVED FROM GROUNDWATERS, TYPICAL OF THOSE IN A GRANITE GEOLOGY PROPOSED FOR WASTE DISPOSAL, AND SECONDLY BY INVESTIGATING THE INTERACTION OF NATURAL AND SYNTHETIC COLLOIDS (AS MODEL SYSTEMS) WITH GRANITE SURFACES WHICH HAVE BEEN CHARACTERISED PETROGRAPHICALLY. THIS SHOULD PROVIDE AN INSIGHT INTO RETENTION MECHANISMS AND WOULD LEAD TO SUBSEQUENT INVESTIGATIONS OF THE TRANSPORT AND HYDRODYNAMIC BEHAVIOUR OF COLLOIDS IN THESE AND OTHER GEOLOGICAL SYSTEMS. HERE EXPERTISE AND TECHNIQUES DEVELOPED AT BOTH HARWELL AND FONTENAY ARE BEING APPLIED IN A COLLABORATIVE INVESTIGATION.

1 PREPARATION AND CHARACTERISATION OF SYNTHETIC COLLOIDS
1.1 PREPARATION OF SILICA, IRON OXIDE, ALUMINA AND HUMIC MATERIALS
1.2 CHARACTERISATION BY LIGHT SCATTERING, ELECTROPHORESIS AND ELECTRON MICROSCOPY
2. CHARACTERISATION OF NATURAL COLLOIDS OCCURING IN GROUNDWATERS
2.1 CHARACTERISATION OF HOST ROCK
2.2 CHARACTERISATION OF GROUNDWATER
2.3 CHARACTERISATION OF NATURAL COLLOIDS BY LIGHT SCATTERING TECHNIQUES, ULTRAFILTRATION AND ELECTRON MICROSCOPY
2.4 ISOLATION OF ORGANIC COLLOIDS
3. STUDIES OF RADIO-COLLOID RETENTION PROCESSES
3.1 ASSOCIATION (INCORPORATION, SORPTION) OF ACTINIDES AND RARE EARTH ELEMENTS WITH NATURAL/SYNTHETIC COLLOIDS
3.2 INTERACTIONS OF COLLOIDS WITH WELL CHARACTERISED MINERAL SURFACES.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

United Kingdom Atomic Energy Authority
Address
353,Harwell
OX11 0RA Didcot - Oxfordshire
United Kingdom

Participants (1)

COMMISSARIAT A L'ENERGIE ATOMIQUE (CEA)
France