Objective
THIS PROJECT UTILISES A CHARACTERISTIC URANIUM PROFILE SHAPE DEVELOPED IN DEEP-SEA TURBIDITE SEDIMENTS TO EXAMINE THE BEHAVIOUR OF URANIUM AND ITS DAUGHTER ISOTOPES OVER TIME-SCALES DESIRED FOR THE ISOLATION OF RADIOACTIVE WASTE. THE GEOCHEMICAL BACKGROUND IS THAT HOMOGENOUS ORGANIC-RICH TURBIDITES, EMPLACEMED IN THE DEEP-SEA, EXPERIENCE OXIDATION FROM THE TOP DOWNWARDS BY BOTTOM WATER.
URANIUM REDISTRIBUTES IN THE TURBIDITE IN RESPONSE TO THE OXIDATION FRONT, BUT THIS REDISTRIBUTION CEASES WHEN THE TURBIDITE IS ISOLATED FROM BOTTOM WATER ON EMPLACEMENT OF THE NEXT TURBIDITE. TWO LONG CORES (MD24 AND MD10) ARE AVAILABLE FROM A 1985 NEA CRUISE WITH SEVERAL SUCH UNITS UP TO 750 KY OLD PRESERVED. GOOD STRATIGRAPHIC, GEOCHEMICAL AND GEOTECHNICAL DATA ARE AVAILABLE, AND PORE WATER ADVECTION IN THE CORES IS BELIEVED TO BE NEGLIGIBLE.
THE GOALS OF THE PROJECT ARE :
DETERMINATION OF THE URANIUM AND ITS LONGER-LIVED DAUGHTER RADIONUCLIDES IN INDIVIDUAL TURBIDITE UNITS AGES BETWEEN 250 AND 750 KY TO COMPARE THE OBSERVED PROFILES WITH THOSE PREDICTED BY RADIOACTIVE INGROWTH SYSTEMATICS.
UTILISATION OF THE EXPERIMENTAL DATA TO ESTIMATE EFFECTIVE DIFFUSION COEFFICIENTS OF THE DIFFERENT ELEMENTS FOR MODELLING PURPOSES. SUCH DATA WILL BE RELEVANT TO THE IN-SITU GEOCHEMICAL AND CONDITIONS OF THE SEDIMENTS OVER THE LONG TIME SCALES INDICATED.
Following the completion of method development, a full set of radiochemical analyses (protoactinium-231) was obtained for turbidite t from core MD24. This turbidite was treated first because the reconnaissance uranium profile had indicated that the lower turbidites in MD24 (particularly u, v and w) had uneven uranium distributions, whereas that for turbidite t was comparatively smooth. Subsequently, samples from turbidite w and surrounding units in core MD24 were analysed because this section represents the oldest sediment in the 2 cores available for study.
1. DEVELOPMENT AND VERIFICATION OF A RADIOCHEMICAL ANALYTICAL SCHEME FOR THE ANALYSIS OF URANIUM-238, URANIUM-234, THORIUM-232, THORIUM-230, PROTACTINIUM-231, RADIUM-226 AND POLONIUM-210.
2. DETERMINATION OF ACTIVITY VERSUS DEPTH PROFILES OF THE ABOVE RADIONUCLIDES FOR DIFFERENT TURBIDITES OF DIFFERENT AGES (250-750 KY) IN CORE MD24.
3. DETERMINATION OF A GROSS URANIUM PROFILE FOR CORE MD10 TO GUIDE SAMPLING AND COMPARISON OF CORRESPONDING TURBIDITE UNIT PROFILES WITH THOSE OF CORE MD24.
4. CHEMICAL PARTITIONING STUDIES OF SELECTED SAMPLES (IF NECESSARY).
5. MODEL DATA OBTAINED.
Fields of science
Topic(s)
Data not availableCall for proposal
Data not availableFunding Scheme
CSC - Cost-sharing contractsCoordinator
GU8 5UB Godalming
United Kingdom