A summary is presented of the results of a number of studies conducted prior to March 1992 that have led to a conceptual model describing how the porosity (and therefore the permeability) of waste and backfill in a Waste Isolation Pilot Plant disposal room changes with time and also describes how results from calculations involving mathematical models of these processes are used to provide input into performance assessment of the repository. Included in the report are descriptions of essential material response or constitutive models that include the influence of gas generation and the response of simple gas-pressurized cracks and fractures in salt, marker beds, and clay seams. Two-dimensional versus three-dimensional disposal room configurations and descriptions of the differences between numerical codes are also discussed. Calculational results using the mathematical models for disposal room response are described, beginning with closure of empty rooms and becoming progressively more complex. More recent results address some of the effects of gas generation in a room containing waste and backfill and intersected by a gas permeable marker bed. Developments currently in progress to improve the evaluation of the disposal room performance are addressing the coupling between brine flow and closure and the two-dimensional capability for analyzing a complete panel of rooms. Next, a method is described for including disposal room closure results into performance assessment analyses that determine if the repository is in compliance with regulatory standards. The coupling is accomplished using closure surfaces that describe the relationship among porosity, total amount of gas in the repository, and time. A number of conclusions about room response and recommendations for further work are included throughout the report.

THE SPMAPPROACHThe goal of SPM was to provide information about how potential activities-twenty-one scientific investigations, three engineered alternatives, and two waste acceptance criteria-when viewed singly or in combination, codd contribute to a demonstration of compliance with EPA long-term performance requirements for the WIPP disposal system:4 For each activity set (a combination of activities), SPM calculated the probability of demonstrating compliance (PDC) if the activity set was implemented, along with the activity set's projected cost and duration.These performance measures (PDC, cost and duration) were contained in a decision matrix t h a t was analyzed to find programmatic options that maximized incremental PDC while minimizing activity set cost and duration. SNL performance assessment models were used to estimate how the disposal system might perform if activities were implemented, and this evaluation. was the basis for calculating an activity set's PDC. SPM analyzed roughly 46,700 activity sets. Probabilistic performance calculations for these activity sets resulted in over 1.3 million complementary cumulative distribution functions (CCDFs).

The in situ formation of conductive carbon lines in polymeric substrates was demonstrated by “writing” with CO2 and Nd:YAG lasers. The formation of conductive carbon lines on polymer substrates proceeds through a series of steps including; absorption of light, initiation of decomposition reactions, and thermal propagation of the pyrolysis. The effect of material composition, power density, energy density, and wavelength on the electrical resistance and morphology of the carbon lines was investigated. Above a critical laser energy density (= 400 J/cm2) sufficient light is absorbed by the substrate such that initiation of the pyrolysis reactions occurs. The decomposed polymer strongly absorbs the incident radiation and the thermal propagation of the reactions forms shiny, conductive, carbon lines. The dimensions of these lines are dependent on the energy density impinging on the polymer and are independent of the wavelengths investigated. If too high a power density is employed (∼ 104 Watts/cm2), an ablated track is formed down the center of the carbon line. This results in the relative insensitivity of the linear resistance with increasing power above 104 Watts/cm2.

Systems Prioritization Method (SPM) is a decision-aiding tool developed by Sandia National Laboratories for the U.S. Department of Energy Carlsbad Area Office to provide an analytical basis for programmatic decision making for the W a s t e Isolation Pilot Plant (WIPP). SPM inkgrates decision-analysis techniques, performance and risk-assessment tools, and advanced information technology. The results are presented in a decision matrix showing cost, duration, and maximum probability of demonstrating compliance (PDC) for all activities in a given cost and duration category. This is the second volume in the series The Second Iteration of the Systems Prioritization Method: A Systems Prioritization and Decision-Aiding Tool for the Taste Isolation Pilot Plant, a three-volume report on the second iteration of SPM (SPM-2). The scope of SPM-2 was restricted to evaluating the predicted performance of the disposal system with respect to selected portions of the applicable U.S. Environmental Protection Agency' s long-term performance regulations, 40 CFR 191.13 (radionuclide containment requirements) and 40 CFR 268.6 (hazardous constituent concentration requirements). A technical baseline based on existing information on the disposal system was developed and evaluated with respect to its adequacy for demonstrating compliance. When the baseline proved to be inadequate, the PDC was calculated for potential future states of knowledge about the disposal system using elicited outcomes of proposed activities and combinations of activities (activity sets) that, if implemented, would potentially lead to compliance. SPM-2 defined the most viable combinations of scientific investigations, engineered alternatives, and waste acceptance criteria for supporting the final compliance application for WIPP. This volume provides a summary of the technical input for SPM-2. It

Systems Prioritization Method (SPM) is a decision-aiding tool developed by Sandia National Laboratories for the U.S. Department of Energy Carlsbad Area Office (DOWCAO) to provide an analytical basis for programmatic decision making for the W a s t e Isolation Pilot Plant (WIPP). SPM integrates decisionanalysis techniques, performance and risk-assessment tools, and advanced information technology. Potential outcomes of proposed activities and combinations of activities (activity sets) are used to calculate a probability of demonstrating compliance (F' DC). The results are presented in a decision matrix showing cost, duration, and maximum PDC for all activities in a given cost and duration category. This is the first volume in the series The Second Iteration of the Systems Prioritization Method: A Systems Prioritization and Decision-Aiding Tool for the Waste Isolation Pilot Plant, a three-volume report on the second iteration of SPM (SPM-2). SPM-2 analyzed the most viable combinations of scientific investigations, engineered alternatives @As), and waste acceptance criteria (WAC) for supporting the final compliance application for WIPP. The scope of SPM-2 was restricted to evaluating the predicted performance of the disposal system with respect to selected portions of the .. 11 ACKNOWLEDGMENTSSPM was a team effort that required the dedicated commitment of many people. To acknowledge everyone that made essential contributions to this analysis would take pages. However, we would like to gratefully acknowledge the efforts of all the 53% WIPP program s t a including the principal investigators and PA analysts, for defining the SPM-2 baseline and activity sets models, developing the technical input, and performing the SPM-2 calculations. We would like to thank Peter SwiR for his carefd review and coordination with the SNL W P compliance efforts, Me1 Marietta for leading the WIPP PA team, and Hong-Nian Jow for his leadership and support in getting the calculations completed. We appreciate the WID staff for supplying the RCRA models and source term, Dr. H. V. Ravinder and Dr. Sul Kassecieh for conducting the elicitations, SAIC for documenting many of the meetings, Tech Reps, Inc., for documentation support, LATA for development of the decision matrix visualization tools and the CD-ROM product, and Informatics Corporation for invaluable scientific and administrative support.We would also like to thank Paul Davis for having the initial vision of SPM and supporting its use in this application. We want to acknowledge Dori Ellis and Wendell Weart for their strong commitment and personal guidance to the SPM management team. And.finally, we wish to thank Bob Bills of DOE/CAO for his contributions both in terms of guidance and support to the SPM effort. iv EXECUTIVE SUMMARYIn March 1994, the U.S. Department of Energy Carlsbad Area Office @OE/CAO) embarked on an effort to design and implement a performance-based decision-aiding tool to provide an analytical basis for planning, prioritizing, and selecting programmatic opt...