HR: 0800h
AN: V11D-0810    [Abstracts]
TI: Igneous Activity at Yucca Mountain: Technical Basis for Decision Making
AU: * Hinze, W
EM: bima@insightbb.com
AF: Purdue University, 30 Brook Hollow, West Lafayette, IN 47906, United States
AU: Marsh, B
EM: bmarsh@jhu.edu
AF: Johns Hopkins University, 322 Olin Hall, Baltimore, MD 21218, United States
AU: Weiner, R
EM: rfweine@sandia.gov
AF: Sandia National Laboratories, P. O. Box 5800, Albuquerque, NM 87185, United States
AU: Coleman, N
EM: nmc@nrc.gov
AF: US NRC, MS T2-E26, Washington, DC 20555, United States
AB: Eighty thousand years ago a small-volume basaltic volcano erupted 20 km south of the Department of Energy's (DOE) proposed high-level radioactive waste repository at Yucca Mountain, Nevada. Lathrop Wells is one of the infrequent basaltic volcanoes that have occurred near Yucca Mountain during the past 10 million years. The Advisory Committee on Nuclear Waste and Materials (ACNW&M) has prepared a summary and analysis of the technical views on the nature, likelihood and potential consequences of future igneous activity at the proposed repository. The technical views have been abstracted from public literature and agency reports. Alternate views reflect uncertainties of the igneous processes that have occurred in the region and those that are likely to occur, as well as the interaction of these processes with the proposed repository. There is general agreement that either extrusive or intrusive igneous activity may occur. The extrusive scenario is likely to cause a larger risk and the effect is greatest within the first thousand years. The nature of igneous activity that could occur will probably be similar in composition, structure, and style to the Lathrop Wells volcano. Certain styles of volcanism, like explosive phreatic eruptions (maar volcanism) are not expected because conditions necessary for these do not exist at Yucca Mountain. The volcanic record, particularly during the past 5 million years, suggests a variety of models for evaluating the probability of future igneous activity. The anticipated range of probability of an igneous event intersecting the proposed repository is low, between 1E-9 and 1E-7/yr. An ongoing DOE expert elicitation incorporating the latest geophysical and drilling data will provide an up-to-date, credible estimate of the probability of volcanic intersection. An understanding of the processes involved in interaction between magma and drifts, waste packages, and waste is evolving and providing new insights. As a result, there is limited consensus regarding the consequences of igneous activity in either the extrusive or intrusive scenario. The proposed alternative models differ significantly. The application of magma physics will reduce differences and conservatisms, and suggests that the ability of magma to intrude waste drifts could be limited. Variability and uncertainty exist in evaluating conceptual models in estimating the probability of an igneous event intersecting the repository, and in estimating the consequences of such an event, particularly in the intrusive scenario. Assessment of the performance of the proposed repository as a result of igneous activity requires evaluation of a range of credible views on both the extrusive and intrusive scenarios and the range of parameter uncertainty. These analyses will be useful in evaluating risk from the repository as well as those aspects of igneous activity that are important to risk and thus worthy of further investigation to reduce uncertainties. The ACNW&M report is available online at: http://www.nrc.gov/reading-rm/doc-collections/acnw/letters/2007/.
DE: 8400 VOLCANOLOGY
DE: 8425 Effusive volcanism
DE: 8429 Lava rheology and morphology
DE: 8434 Magma migration and fragmentation
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting