Uranium Transport and the Partitioning of U, Th, and Ra Isotopes Between Solid and Aqueous Phases in the Krunkelbach Mine, Federal Republic of Germany

Abstract

This paper discusses some of the results from a natural geochemical analogue study on the Krunkelbach mine, F.R.G. These data, based largely on uranium series disequilibrium measurements, are used to compare the results of groundwater modelling programmes with observations made in the mine.

Aspects of Uranium/Thorium Series Disequilibrium Applications to Radionuclide Migration Studies

“…For example, whole rock analyses often yield equilibrium amounts of the uranium series members whereas the associated waters exhibit great radioactive disequilibrium; depending on how closed is the rock/water system, a complementary disequilibrium of at least the surface exposed to the water, must exist. In an attempt to overcome this difficulty, some investigators have conducted detailed phase separation studies, attempting to extract just the surface layers for disequilibrium analysis [15,16,20,21].…”

“…and fluid phases of some low permeability rock matrices Based on some pioneering work carried out by Airey and coworkers [11,13,14], Ivanovich and coworkers [15,16,20,21,23] or 'mudrock' (Fulbeck). Phases I through IV, readily ion-exchangeable component (IE), adsorbed ions (AH), amorphous ferromanganese oxyhydroxides (AM) and carbonates (CO) are regarded as the main components of the solid phase involved in direct reaction with the fluid phase whilst phases V and VI, crystalline (CR) and resistate phases (R), are regarded as taking relatively little part in these interactions on a medium to short timescale.…”

“…The above approach was extended to Barhalde granite as part of a natural analogue and rock/water interaction study of the Krunkelbach uranium mine, FRG [20,21,25]. The purpose of the project was to study the mobility of natural radionuclides and their retention by granite and fracture-filling clay minerals.…”

“…[D( 1 -φ)/φ] where R { is retardation factor (inverse of 222 Rn/radionuclide activity ratio[20], D is density of aquifer solid (1.48 g cm -3 ) and φ is porosity of solid phase (70%). b Measured R d is concentration in solid phase/concentration in liquid phase.…”

Natural Analogue Aspects of Radionuclide Transport in the Geosphere

“…In granites, many analogue studies have carefully investigated the processes of elemental migration/retardation, in particular for uranium, thorium and rare earths, which are assumed to mimic the behaviour of transuranium elements [10,15,16,17]. The main output of these studies was to show that, in addition to classical "sorption" which was for long the only phenomenon taken into account in models, retardation of radionuclides should also occur via (co)precipitation with secondary phases.…”