Basic Research Needs for Geosciences - Energetics Meetings and ...

APPENDIX 1: TECHNICAL PERSPECTIVES RESOURCE DOCUMENTkinetics, and colloid-facilitated transport). Moreover, methodologies are needed to upscale,downscale, and appropriately average the highly heterogeneous transport parameters, processes,and resulting radionuclide breakthrough curves. Finally, alternative conceptual models need tobe developed, capable of analyzing anomalous transport behaviors such as early arrival ofradionuclides as well as multimodal and heavy-tailed breakthrough curves.6. Disruptive eventsDisruptive events (such as volcanic and seismic events) may affect repository performance in away that is fundamentally different from features, events, and processes described in the nominalcase. Disruptive events are fundamentally different in terms of their occurrence probability, theirconsequence, and their discreteness. Challenges in geosciences in need of further researchinclude the prediction of the occurrence of low-probability disruptive events, their impact on thenatural and engineered systems, their aleatory and epistemic uncertainty characteristics, andmathematical and computational methods to embed them into a performance analysis (e.g.,Woods et al. 2002; Ho et al. 2006).Additional cross-cutting needsIn addition to research needs for the repository system elements, there are several cross-cuttingareas that have technology and applied research and development needs. These are discussednext in more detail.1. Repository design and nuclear fuel cycleChanges in repository design or the consideration of alternative nuclear fuel cycles (which mayinclude reprocessing of spent nuclear fuel and waste partitioning and transmutation technologies)may significantly affect the requirements for and performance of the natural barrier system.Possible variants in repository design could include a low temperature (sub-boiling) vs. hightemperature (boiling) waste configuration, backfill vs. no backfill in the emplacement drifts, andthe use of an extended period of ventilation in the drifts. A technology is needed to fully coupleand optimize decisions on the nuclear fuel cycle and repository design as they relate to overallsystem performance. (Note also that uranium ore exploration and mining is an essential part ofthe nuclear fuel cycle that is addressed by geosciences.) Alternative disposal technologies (e.g.,the deep borehole approach, Kuo et al. 1995) need to be evaluated as well.2. MonitoringMonitoring the natural system during the early stages of repository operation is a critical aspectof a defensible nuclear waste disposal strategy. The rationale for monitoring a variety ofvariables representing the state of the repository system is to: (1) provide early warning ofunforeseen system behavior and consequences of repository operation, and (2) provide data forconfirming site conditions and previous model predictions, or for progressively adjusting theparameters of such models. Designing a monitoring system suitable for adaptive repositorymanagement is expensive and challenging, because of: (1) the variety of performance-relevantparameters that need to be observed, (2) the size and inherent complexity, heterogeneity, anddiscreteness of the natural system, (3) the fact that the system to be monitored may exhibitpreviously unknown or unanticipated behavior, and (4) the need to minimize the risk of notdetecting a performance failure. There is a need to design robust, efficient, comprehensive, andcost-effective monitoring systems of large natural and man-made systems. These approachesmust evaluate the scope of monitoring, identify observable variables, and optimize measurementBasic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems Appendix 1 • 41