We acknowledge the contributions made in the development of the ideas, concepts and positions on technical issues that form the basis of this report by OUT colleagues who were previously with the EEG.

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...

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, , manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Performance/safety assessments have been conducted for the Waste Isolation Pilot Plant, a repository for transuranic waste in salt. We challenge two key assumptions in the 1992 Performance Assessment that led to non-conservative results. The predicted release rate of radionuclides appears underestimated due to the use of expert elicited solubilities. The overall release has been underestimated due to the use of improperly elicited human intrusion probabilities.

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