Title 40 CFR Part 191 Subparts B and C Compliance Recertification Application 2019 for the Waste Isolation Pilot Plant Appendix SOTERM-2019 Actinide Chemistry Source Term United States Department of Energy Waste Isolation Pilot Plant Carlsbad Field Office Carlsbad, New Mexico Compliance Recertification Application 2019 Appendix SOTERM-2019 Actinide Chemistry Source Term Title 40 CFR Part 191 Subparts B and C Compliance Recertification Application 2019 Table of Contents SOTERM-1.0 Introduction ........................................................................................ SOTERM-1 SOTERM-2.0 Ambient Geochemical Conditions, Repository Conditions and Emplacement Chemistry in the WIPP ............................................................... SOTERM-3 SOTERM-2.1 Ambient Geochemical Conditions ................................................ SOTERM-3 SOTERM-2.2 Repository Conditions: Assumptions and Role of the Engineered Barrier and Key WIPP Processes ....................................................................... SOTERM-5 SOTERM-3.0 Post-emplacement Inventory, Chemical, and Radiolytic Processes .. SOTERM-7 SOTERM-3.1 Inventory of Emplaced Materials in the WIPP ............................. SOTERM-7 SOTERM-3.2 WIPP-Relevant Brine Chemistry ................................................ SOTERM-11 SOTERM-3.3 Complexation of Actinides by Organic Chelating Agents ......... SOTERM-12 SOTERM-3.3.1 Projected Concentration of Organic Chelating Agents under WIPP-relevant Conditions ......................................................... SOTERM-12 SOTERM-3.3.2 Stability Constants for Organic Complexation with Actinides SOTERM-13 SOTERM-3.3.3 WIPP-Relevant Organic Complexation Studies ................. SOTERM-13 SOTERM-3.3.4 New Literature Organic Interaction Results Since CRA- 2014 SOTERM-16 SOTERM-3.3.5 WIPP-specific Data on Organic Complexation Effects Since CRA-2014 .................................................................................. SOTERM-17 SOTERM-3.4 Radiolysis Effects in the WIPP ................................................... SOTERM-17 SOTERM-3.4.1 Radiation Chemistry of Brine Systems............................... SOTERM-17 SOTERM-3.4.2 Potential Radiolytic Effects on Actinide Speciation and Solubility SOTERM-20 SOTERM-3.4.3 WIPP Relevant and Literature Data Since the CRA-2014 . SOTERM-21 SOTERM-3.5 Actinide Colloids ........................................................................ SOTERM-22 SOTERM-3.5.1 Actinide Colloids in the Environment ................................ SOTERM-23 SOTERM-3.5.2 WIPP-Specific Results since the CRA-2014 PA ................ SOTERM-24 SOTERM-4.0 Microbial Effects in the WIPP ......................................................... SOTERM-27 SOTERM-4.1 Effects of the Biodegradation of CPR ........................................ SOTERM-27 SOTERM-4.1.1 Current WIPP PA Gas Generation Model .......................... SOTERM-27 SOTERM-4.1.2 Evolution of the WIPP Microbial Gas Generation Model .. SOTERM-28 SOTERM-4.1.3 WIPP-Relevant Gas Generation Results Since CRA-2014 SOTERM-29 SOTERM-4.2 Microbial Activity in the WIPP .................................................. SOTERM-30 SOTERM-4.2.1 Constraints on Activity ....................................................... SOTERM-30 SOTERM-4.2.2 Modes of Metabolism Among Extreme Halophiles in an Anoxic Environment ............................................................................ SOTERM-31 SOTERM-4.2.3 Variations in Microbial Communities and Activity with Time and Space ............................................................................................ SOTERM-32 SOTERM-4.2.4 WIPP-relevant Microbial Degradation of CPR .................. SOTERM-33 SOTERM-4.3 Microbial-Actinide Interactions .................................................. SOTERM-34 DOE/WIPP-19-3609, Rev. 0 SOTERM-i December 18, 2019 Title 40 CFR Part 191 Subparts B and C Compliance Recertification Application 2019 SOTERM-4.3.1 Actinide Toxicity Towards WIPP-Relevant Microorganisms ................................................................................... SOTERM-35 SOTERM-4.3.2 Bioreduction of Multivalent Actinides ............................... SOTERM-36 SOTERM-4.3.3 Biological Influence on Actinide Mobility via Association or Influence on Solubility .................................................................... SOTERM-36 SOTERM-4.3.4 WIPP-Specific Results since CRA-2014 ............................ SOTERM-37 SOTERM-5.0 WIPP-Relevant Actinide Chemistry ................................................ SOTERM-40 SOTERM-5.1 Changes/Status in Actinide Chemistry Information since the CRA- 2014 SOTERM-41 SOTERM-5.2 Actinide Inventory in the WIPP .................................................. SOTERM-44 SOTERM-5.3 Actinium Chemistry .................................................................... SOTERM-47 SOTERM-5.3.1 Actinium Environmental Chemistry ................................... SOTERM-48 SOTERM-5.3.2 New Literature Results Since the CRA-2014 ..................... SOTERM-48 SOTERM-5.3.3 WIPP-Specific Results Since the CRA-2014 ..................... SOTERM-49 SOTERM-5.4 Thorium Chemistry ..................................................................... SOTERM-49 SOTERM-5.4.1 Thorium Environmental Chemistry .................................... SOTERM-49 SOTERM-5.4.2 Literature review since CRA-2014 ..................................... SOTERM-57 SOTERM-5.4.3 WIPP-Specific Results since the CRA-2014 and the CRA-2014 PABC................................................................................. SOTERM-58 SOTERM-5.5 Uranium Chemistry ..................................................................... SOTERM-58 SOTERM-5.5.1 Uranium Environmental Chemistry .................................... SOTERM-58 SOTERM-5.5.2 Literature review since CRA-2014 ..................................... SOTERM-70 SOTERM-5.5.3 WIPP-Specific Results since the CRA-2014 ...................... SOTERM-73 SOTERM-5.6 Neptunium Chemistry ................................................................. SOTERM-73 SOTERM-5.6.1 Neptunium Environmental Chemistry ................................ SOTERM-74 SOTERM-5.6.2 New Literature Results Since the CRA-2014 ..................... SOTERM-76 SOTERM-5.6.3 WIPP-Specific Results since the CRA-2014 ...................... SOTERM-78 SOTERM-5.7 Plutonium Chemistry .................................................................. SOTERM-78 SOTERM-5.7.1 Plutonium Environmental Chemistry ................................. SOTERM-79 SOTERM-5.7.2 Thermodynamic Stability of Higher-Valent Plutonium: PuO2+x ............................................................................................ SOTERM-82 SOTERM-5.7.3 New Literature Results Since the CRA-2014 ..................... SOTERM-83 SOTERM-5.7.4 WIPP-Specific Results since the CRA-2014 ...................... SOTERM-83 SOTERM-5.8 Americium and Curium Chemistry ............................................. SOTERM-89 SOTERM-5.8.1 Americium and Curium Environmental Chemistry ............ SOTERM-90 SOTERM-5.8.2 New Literature Results Since CRA-2014 ........................... SOTERM-94 SOTERM-5.8.3 WIPP-Specific Results since the CRA-2014 PA ................ SOTERM-94 SOTERM-6.0 Calculation of the WIPP Actinide Source Term .............................. SOTERM-95 SOTERM-6.1 Overview of WIPP Approach to Calculate Mobile Actinide Concentrations ...................................................................................................................95 SOTERM-6.1.1 WIPP Mobile Actinide Source Term .................................. SOTERM-96 SOTERM-6.1.2 Conservatisms and Assumptions in the WIPP Source- Term Modeling Approach ............................................................................................ SOTERM-98 SOTERM-6.1.3 Overview of Changes Implemented in CRA-2019 PA ..... SOTERM-100 DOE/WIPP-19-3609, Rev. 0 SOTERM-ii December 18, 2019 Title 40 CFR Part 191 Subparts B and C Compliance Recertification Application 2019 SOTERM-6.1.4 Critical Assessment of the Current WIPP Modeling Approach SOTERM-101 SOTERM-6.2 Role, Importance and Impacts of the Actinide Inventory Data SOTERM-102 SOTERM-6.3 Role and Use of Oxidation-State-Invariant Analogs ................ SOTERM-103 SOTERM-6.4 Redox and Oxidation State Distribution in the WIPP .............. SOTERM-106 SOTERM-6.5 Actinide Speciation Reactions Used in EQ3/6 ......................... SOTERM-109 SOTERM-6.5.1 The III Actinides: Ac(III), Pu(III), Am(III), Cm(III) ....... SOTERM-109 SOTERM-6.5.2 The IV Actinides: Th(IV), U(IV), Pu(IV), Np(IV) .......... SOTERM-111 SOTERM-6.5.3 The V Actinides: Np(V) ................................................... SOTERM-113 SOTERM-6.5.4 The VI Actinides: U(VI) ................................................... SOTERM-114 SOTERM-6.6 Calculations of Actinide Solubility Using the EQ3/6 Computer Code SOTERM-114 SOTERM-6.6.1 Pitzer Approach for High-Ionic-Strength Brines .............. SOTERM-115 SOTERM-6.6.2 Calculated Actinide Solubilities ....................................... SOTERM-116 SOTERM-6.6.3 Calculation of Colloidal Contribution to Actinide Solution Concentrations ................................................................................... SOTERM-117 SOTERM-6.6.4 WIPP Actinide Source Term (Total Mobile Actinide Concentration).................................................................................... SOTERM-118 SOTERM-7.0 References .....................................................................................