Anthropogenic Induced Redox Disequilibrium in Uranium Ore Zones Richard Abitz, Savannah River National Laboratory Bruce Darling, Southwest Groundwater Consulting, LLC Please extend my regrets for absence at the meeting, due to a conflict with work travel to the UK. GSA 2010, Denver, Colorado

Drilling Issues Related to Redox Disequilibrium Physical change to the ore minerals Chart assumes constant volume based on a 1000 um diameter particle

Drilling Issues Related to Redox Disequilibrium Chemical reactions in the ore zone 7/2O2 + H2O + FeS2 → 2H+ + Fe++ + 2SO4-- ½O2 + 2H+ + UO2 → H2O + UO2++ Airlift purge and pump adds O2 Introduction of oxygen from drilling fluids and airlift purge during well development. Arsenic release from pyrite oxidation.

Mineral Dissolution Rates General form of rate law (Lasaga, 1995)1: Rate = k0*Amin*e-Ea/RT*anH+*g(I)*Πiani*f(ΔGr) Increase in both surface area (Amin) and O2 activity (anO2) will increase dissolution rate. 1 Lasaga, A.C., 1995, Fundamental Approaches in Describing Mineral Dissolution and Precipitation Reactions, in Reviews in Mineralogy, Volume 31, Chemical Weathering Rates of Silicate Minerals, Mineralogical Society of America. Introduction of oxygen from drilling fluids and airlift purge during well development. Arsenic release from pyrite oxidation.

Goliad Project about 130 mi SW of Houston 12 mi N of Goliad 15 mi E of Victoria

UEC Permit UR03075 Cartoon of Goliad section at the proposed ISL site About 350 to 400 ft of sand with gravel, silt, clay Target sand horizons 50 to 80 feet thick Fluvial deposits exposed in area, change to deltaic down dip UEC Permit UR03075

UEC Permit UR03075 Initial ISL target is B Sand, yellow pattern Permit Area about 3 km E-W First ore body proposed to develop; Sand B (yellow pattern) Proposed aquifer exemption zone is black dashed line surrounding proposed production sands Private water wells within 1 km of permit boundary (blue dots) Note 44 (Abrameit Windmill) located within PA

Production Test Wells (PTW), Sand B URANIUM: Apr 2008: 0.005 to 0.804 mg/L July 2009: <0.003 to 0.090 mg/L Nov 2009: <0.003 to 0.010 mg/L Variation due to redox instability, and not natural variation of ion concentrations (see F plot slide). April 2008 sampling round after initial well development All November results below EPA DW std of 0.030 mg/L Low U results in line with reducing conditions for uranium ore body One-half detection limit plotted

Production Test Wells (PTW), Sand B ARSENIC: Apr 2008: 0.001 to 0.022 mg/L July 2009: <0.010 mg/L Nov 2009: <0.010 mg/L Indication of oxidation in some wells. Other wells have no source for As? Lower values for Round 1 are an artifact of a lower reported detection limit for round 1

Production Test Wells (PTW), Sand B FUORIDE: Apr 2008: 0.50 to 0.79 mg/L July 2009: 0.50 to 0.54 mg/L Nov 2009: 0.50 to 0.69 mg/L F results show U variation is not due to natural fluctuations in ion concentrations. All rounds show similar results

Production Test Wells (PTW), Sand B RADIUM: Apr 2008: 10 to 1,680 pCi/L July 2009: 17 to 2,000 pCi/L Nov 2009: 10 to 1,590 pCi/L Similar results for all 3 rounds…exception is PTW 13 (low first round) After ore has been disturbed, radium will not return to low values (not redox sensitive and mobilized by chloride ion)

B Monitor Wells (BMW), Sand B URANIUM: Apr 2008: <0.001 to 0.188 mg/L July 2009: <0.003 to 0.006 mg/L Nov 2009: <0.003 mg/L April 2008 sampling round after initial well development All July and November results below EPA DW std of 0.030 mg One-half detection limit plotted

B Monitor Wells (BMW), Sand B ARSENIC: Apr 2008: 0.001 to 0.069 mg/L July 2009: <0.010 mg/L Nov 2009: <0.010 mg/L Indication of oxidation in some wells. Other wells have no source for As? Lower values for Round 1 are an artifact of a lower reported detection limit for round 1

B Monitor Wells (BMW), Sand B RADIUM: Apr 2008: 0.90 to 41 pCi/L July 2009: 1.3 to 48 pCi/L Nov 2009: 0.10 to 40 pCi/L Similar results for all 3 rounds After ore has been disturbed, radium will not return to low values (not redox sensitive and mobilized by chloride ion) BMW 10, 11, 14, 15 have similar uranium results…no significant U ore or no significant oxidation. Radium is less than 5 pCi/L in these wells.

Overlying Monitor Wells (OMW), Sand A URANIUM: Apr 2008: 0.006 to 0.014 mg/L July 2009: 0.003 to 0.013 mg/L Nov 2009: 0.009 to 0.012 mg/L Similar variation of U over all three rounds No uranium ore to oxidize

Overlying Monitor Wells (OMW), Sand A ARSENIC: Apr 2008: 0.010 to 0.031 mg/L July 2009: 0.005 to 0.010 mg/L Nov 2009: 0.005 to 0.010 mg/L Reduction of As in Rounds 2 & 3

Overlying Monitor Wells (OMW), Sand A RADIUM: Apr 2008: 0.5 to 6.0 pCi/L July 2009: 0.2 to 3.2 pCi/L Nov 2009: 0.4 to 1.0 pCi/L

Uranium solubility as a function of Eh Boxes show range of concentration and Eh for sampling rounds Note boxes shift to lower Eh range as one progresses from round 1 to round 3. Implies concentration control by redox decrease and uranium solubility.