On April 10, 2006, the U.S. Department of Energy (DOE) submitted a planned change request pertaining to the amount of MgO emplaced in the WIPP repository. MgO is an engineered barrier that DOE included as part of the original WIPP Certification Decision that ensures repository releases will be well within the EPA's regulatory limits.

• EPA Fact Sheet - WIPP: Planned Change Request for Magnesium Oxide (MgO) (PDF)(1 pg, 119 K)
  This fact sheet provides an overview of the planned change request related to MgO.
• DOE Fact Sheet - WIPP Technical Fact Sheet: Planned Change Request for Magnesium Oxide (PDF)(2 pp, 348 K)
  This fact sheet summarizes the planned change request for magnesium oxide.
• Letter from EPA to DOE announcing the completeness of their review of the DOE planned change request (PDF)(2 pp, 130 K)
  This letter responds to DOE's request to propose a reduction in the MgO safety factor from 1.67 to 1.2 times the amount of emplaced carbon materials.
• Attachments to correspondence dated 2/11/08 - Overview Summary of Planned Change Request Decision (PDF)(30 pp, 267 K)
  These attachments are related to DOE's submitted planned change request to decrease the amount of emplaced magnesium oxide (MgO) from 1.67 to 1.2 times the quantity of emplaced carbon in the disposed waste.
• Attachment to correspondence dated 2/11/08 - Final Report: Review of MgO-Related Uncertainties in the Waste Isolation Pilot Plant (PDF)(71 pp, 933 K)
  Anhydrous, granular, bulk magnesium oxide (MgO) backfill has been included as an engineered barrier in WIPP to mitigate possible impacts of CO2 on the waste by fulfilling a repository design requirement "to prevent or substantially delay the movement of water or radionuclides toward the accessible environment" [40 CFR 194.44(a)]. The MgO is expected to react with CO2, which should reduce gas pressures and buffer pH so that actinide solubilities are constrained.
• DOE Letter to EPA on approval of MgO (PDF)(12 pp, 3 MB)
  This letter request EPA approval to emplace 1.2 moles of MgO for every mole of consumable carbon contained in the transuranic waste emplaced in the WIPP.
• Letter from EPA to DOE discussing DOE's request for approval to reduce the amount of excess magnesium oxide (MgO) emplaced in the WIPP. (PDF)(2 pp, 146 K)
  Letter requesting approval to reduce the amount of excess magnesium oxide (MgO) emplaced in the WIPP.
• Preliminary Review of the Degradation of Cellulosic, Plastic, and Rubber Materials in the Waste Isolation Pilot Plant, and Possible Effects on Magnesium Oxide Safety Factor Calculations (PDF)(55 pp, 435 K, 402-R-01-009)
  As a result of DOE's request to reduce the WIPP MgO safety factor, EPA developed this preliminary review to identify technical questions and uncertainties associated with a further reduction in the MgO safety factor.
• DOE Letter to EPA requesting the withdrawal of Brush et. al - Report from the MgO Uncertainty Analysis (PDF)(4 pp, 305 K, November 21, 2006)
  This letter and its enclosures provide an uncertainty analysis that support the U.S. Department of Energy's request for a reduction in the amount of magnesium oxide (MgO) emplaced at the Waste Isolation Pilot Plant (WIPP).
• Analysis of Martin Marietta MagChem 10 WTS-60 MgO (11/21/06 Enclosure) (PDF)(28 pp, 2 MB)
  The objective of this report is to address uncertainties concerning the amount of periclase plus lime in Martin Marietta (MM) MgO.
• Consumption of Carbon Dioxide by Precipitation of Carbonate Minerals Resulting from Dissolution of Sulfate Minerals in the Salado Formation In Response to Microbial Sulfate Reduction in the WIPP (11/21/06 Enclosure) (PDF)(100 pp, 373 K)
  This analysis report describes simulations of the effects of consumption of carbon dioxide (CO2) by the precipitation of carbonate minerals on the excess factor for the magnesium oxide (MgO) being emplaced in the U.S. Department of Energy's (DOE's) Waste Isolation Pilot Plant (WIPP).
• Geochemical Information for Calculation of the MgO (11/21/06 Enclosure) (PDF)(36 pp, 226 K)
  This memorandum provides geochemical information required to calculate the effective excess factor for the magnesium oxide (MgO) being emplaced in the U.S. Department of Energy's (DOE's) Waste Isolation Pilot Plant (WIPP).
• Normalized moles of Castile sulfate entering the repository and fraction of MgO lost due to brine flow out of the repository (11/21/06 Enclosure) (PDF)(20 pp, 141 K)
  Calculations were performed to address and quantify the amount of sulfate that could enter the repository from the Castile brine and the amount of MgO that could be lost due to dissolution in brine and subsequent movement of that brine out of the repository.
• Updated Analysis of Characteristic Time and Length Scales for Mixing Processes in the WIPP Repository to Reflect the CRA-2004 PABC Technical Baseline and the Impact of Supercompacted Mixed Waste and Heterogeneous Waste Emplacement (11/21/06 Enclosure) (PDF)(12 pp, 83 K)
  This memorandum is designed to address EPA's request, with respect to the analysis of mixing processes
• Uncertainty in Cellulose, Plastic, and Rubber Measurements for the Waste Isolation Pilot Plant Inventory (11/21/06 Enclosure) (PDF)(16 pp, 88 K)
  The purpose of this memo is to address the EPA's questions concerning uncertainties in CPR measurements and their impact upon long-term performance and the MgO safety factor.
• Uncertainties Affecting MgO Effectiveness and Calculation of the MgO Effective Excess Factor, Revision 0 (11/21/06 Enclosure) (PDF)(52 pp, 269 K)
  This report documents the uncertainty review and the results of this analysis.
• DOE Letter to EPA regarding the DOE planned change request to reduce the amount of MgO emplaced in the repository (PDF)(2 pp, 60 K)
  This letter addresses DOE's submittal of an uncertainty analysis.