The solubility of actinides is very important to calculating the releases from the repository. The CCA uses a model known as FMT to calculate these solubilities. EEG found that the model predicts differences for actinide sulfate solubilities that cannot be explained by chemistry, thus raising questions about the reliability of this model.Rather than using an extensive plutonium data base, the FMT predictions relied on thermodynamic data for other elements and an oxidation state analog argument. EEG recommends that the calculations be performed using data for plutonium and the values for solubility and complex ion formation contained in the peer-reviewed data compilation by the Organization for Economic Cooperation and Development/Nuclear Energy Agency (OECDLNEA).EEG agrees with EPA's documentation of the shortcomings of the solubility uncertainty ranges advanced by DOE. However, EEG questions EPA's argument that the ranges are adequate. As noted by EPA, there is a lack of data to determine the uncertainty ranges for oxidation states IV and VI. EEG recommends that the uncertainty range needs to be determined with the appropriate plutonium data.In the solubility calculations, the CCA inappropriately discounts the role of organic ligands on plutonium solubility by arguing that EDTA is the strongest complexing agent and there is not enough amount present in the inventory to make a difference. But citrate forms very strong complexes with actinides in the +4 oxidation state and very weak complexes with other cations. Thus, the solubility of a stable plutonium-citrate complex in individual waste containers needs to be calculated.There are serious unanswered questions about the impact of magnesium oxide backfill on the solubility of the actinides. It is proposed that magnesium oxide will reduce the solubility of the actinides by controlling the pH. But, it is not known how long the early reaction product, nesquehonite, will persist. The FMT model calculates that the presence of nesquehonite drives the xxi solubility of the +4 actinides, such as plutonium, higher than in the no backfill case. This requires further investigation. SpallingsThe CCA spallings model was rejected by the DOE'S peer review after submission of the CCA, but a new coherent model and a computer code that calculates the projected releases has not been developed. The EEG finds the basis of accepting the predicted release volumes due to spallings as determined by the CCA to be both unnecessarily convoluted and faulty. Since this is a mechanism for the largest projected releases from the repository, it is essential that it is treated through defensible conceptual and numerical models. Air DrillingThe air drilling scenario proposed by Dr. John Bredehoeft was rejected on the basis of regulation, despite records of such drilling in the Delaware Basin. Low probability and low consequence are also discussed in EPA's Air Drilling Analysis (U.S. EPA, 1998), and the scenario was ruled out again. However, the EEG does not believe that the issue has been resolved...

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