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Volcanic hazards: Perspectives from eruption prediction to risk assessment for disposal of radioactive waste

Description: This document summarizes an oral presentation that described the potential for volcanic activity at the proposed Yucca Mountain, Texas repository site. Yucca Mountain is located in a broad zone of volcanic activity known as the Death Valley-Pancake Ridge volcanic zone. The probability estimate for the likelihood that some future volcanic event will intersect a buried repository at Yucca Mountain is low. Additionally, the radiological consequences of penetration of a repository by basaltic magma followed by eruption of the magma at the surface are limited. The combination of low probability and limited consequence suggests that the risk posed by waste storage at this site is low. (TEM)
Date: December 31, 1980
Creator: Crowe, B.
Partner: UNT Libraries Government Documents Department

Basaltic volcanic episodes of the Yucca Mountain region

Description: The purpose of this paper is to summarize briefly the distribution and geologic characteristics of basaltic volcanism in the Yucca Mountain region during the last 10--12 Ma. This interval largely postdates the major period of silicic volcanism and coincides with and postdates the timing of major extensional faulting in the region. Field and geochronologic data for the basaltic rocks define two distinct episodes. The patterns in the volume and spatial distribution of these basaltic volcanic episodes in the central and southern part of the SNVF are used as a basis for forecasting potential future volcanic activity in vicinity of Yucca Mountain. 33 refs., 2 figs.
Date: March 1, 1990
Creator: Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Disruptive event analysis: volcanism and igneous intrusion

Description: An evaluation is made of the disruptive effects of volcanic activity with respect to long term isolation of radioactive waste through deep geologic storage. Three major questions are considered. First, what is the range of disruption effects of a radioactive waste repository by volcanic activity. Second, is it possible, by selective siting of a repository, to reduce the risk of disruption by future volcanic activity. And third, can the probability of repository disruption by volcanic activity be quantified. The main variables involved in the evaluation of the consequences of repository disruption by volcanic activity are the geometry of the magma-repository intersection (partly controlled by depth of burial) and the nature of volcanism. Potential radionuclide dispersal by volcanic transport within the biosphere ranges in distance from several kilometers to global. Risk from the most catastrophic types of eruptions can be reduced by careful site selection to maximize lag time prior to the onset of activity. Certain areas or volcanic provinces within the western United States have been sites of significant volcanism and should be avoided as potential sites for a radioactive waste repository. Examples of projection of future sites of active volcanism are discussed for three areas of the western United States. Probability calculations require two types of data: a numerical rate or frequency of volcanic activity and a numerical evaluation of the areal extent of volcanic disruption for a designated region. The former is clearly beyond the current state of art in volcanology. The latter can be approximated with a reasonable degree of satisfaction. In this report, simplified probability calculations are attempted for areas of past volcanic activity.
Date: August 1, 1980
Creator: Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Approach, methods and results of an individual elicitation for the volcanism expert judgment panel

Description: Probabilistic volcanic hazard assessment (PVHA) of future magnetic disruption of the Yucca Mountain site was completed as a participating member of the volcanism export judgment panel conducted by Geomatrix Consultants for the Department of Energy. The purpose of this summary is to describe the data assumptions, methods, and results of the elicitation and to contrast this assessment with past volcanism studies conducted for the Yucca Mountain Project.
Date: June 1, 1996
Creator: Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Status of evaluation of tuff in southern Nevada for geologic disposal of high level nuclear wastes

Description: Siliceous tuff in southern Nevada occurs in a complex and locally active geological environment. Regional thrust faulting, Basin and Range faulting, and present-day seismicity complicate exploration and site characterization activities. The inherent variability of tuff and the complexity of caldera complexes also complicate siting efforts, but may serve to enhance long-term containment. Time--space trends of silicic volcanism are moderately well-established, while those of recent basaltic volcanism are not. At present, the final consequences for repository siting of the geologic complexities described in this paper are not known. Evidence from laboratory cation exchange measurements indicate that tuff and tuffaceous alluvium can serve as effective natural barriers to migration of radionuclides. This fact, coupled with multiple hydrologic barriers and long flow paths, as in the vicinity of the Nevada Test Site, might well result in tuff being a suitable medium for the safe long-term geologic disposal of nuclear wastes. Preliminary thermal modeling indicates the strong influence of varying assumptions regarding in situ fluid pressures and geothermal heat flux on acceptable initial areal power loadings.
Date: December 31, 1979
Creator: Lappin, A. R. & Crowe, B. M.
Partner: UNT Libraries Government Documents Department

Preliminary report on the statistical evaluation of sorption data: Sorption as a function of mineralogy, temperature, time, and particle size

Description: This report studies the transport of radionuclides from a repository to the environment by dissolution of the stored solid-waste form and subsequent transport in water. The sorption process may retard this movement of radionuclides from the repository to the accessible environment. A measure of this retardation process is the sorption ratio, R/sub D/, where R/sub D/ = (activity in solid phase per unit mass of solid)(activity in solution per unit volume of solution). In this study, predictions of the R/sub D/ values for the elements barium, cerium, cesium, europium, and strontium are developed from linear regression techniques. An R/sub D/ value was obtained for numerous drill core samples. Additional data include the particle size of the rock, temperature condition during the experiment, concentration of the sorbing element, and length of the sorption experiment. Preliminary regression results based on these data show that the temperature and length of the experiment are the most significant factors influencing the R/sub D/ values. Particle size has a slight effect, and based on a small amount of data, it appears that concentration had no effect. The x-ray diffraction data are used to classify the samples by mineralogy, and regression techniques are used to develop estimates of the R/sub D/ values. Zeolite abundance of 10% or more with some addition of clay increases the sorption values significantly. 12 refs., 3 figs., 6 tabs.
Date: May 1, 1988
Creator: Beckman, R.; Thomas, K. & Crowe, B.
Partner: UNT Libraries Government Documents Department

Geochemical evidence for waning magmatism and polycyclic volcanism at Crater Flat, Nevada

Description: Petrologic and geochemical studies of basaltic rocks in the Yucca Mountain region are currently focused on understanding the evolution of volcanism in the Crater Flat volcanic field and the mechanisms of polycyclic volcanism at the Lathrop Wells volcanic center, the youngest center in the Crater Flat volcanic field. Geochemical and petrologic data indicate that the magma chambers which supplied the volcanic centers in Crater Flat became situated at greater crustal depths as the field evolved. Deep magma chambers may be related to a waning magma flux that was unable to sustain upper crystal magma conduits and chambers. Geochemical data from the Lathrop Wells volcanic center indicate that eruptive units identified from field and geomorphic relationships are geochemically distinct. The geochemical variations cannot be explained by fractional crystallization of a single magma batch, indicating that several magma batches were involved in the formation of the Lathrop Wells center. Considering the low magma flux in the Yucca Mountain region in the Quaternary, the probability of several magma batches erupting essentially simultaneously at Lathrop Wells in considered remote. It is more likely that the Lathrop Wells center was formed by a series of eruptions that took place over many thousands of years. The geochemical data from Lathrop Wells is consistent with the concept of a complex, polycyclic volcano, which was originally proposed based on geomorphic and soil-development data.
Date: December 31, 1991
Creator: Perry, F.V. & Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Research and development related to the Nevada nuclear waste storage investigations. Progress report, July 1-September 30, 1980

Description: Sorption of americium and plutonium was measured in a controlled, oxygen-free atmosphere and in air on a series of tuff samples. Sorption of plutonium was greater in the controlled atmosphere than in air. Sorption of both elements is higher on zeolitized tuff than devitrified tuff. Sorption of strontium, cesium, barium, cerium, and europium is being measured on tuff samples of mineralogies not previously studied, and samples from the USW-G1 drill hole have been selected for study. Work on the dependence of the sorption ratio on element concentration (barium and europium) and on solution-to-solid ratios is reported. Progress on controlling Eh and making Eh measurements is presented. Some tuff-water systems exhibit reduced or negative Eh values under oxygen-free conditions. Development of a method for encasing cores for flow studies is discussed. Field geologic mapping is being conducted in the Lunar Crater volcanic field of central Nevada. Mineralogy-petrology studies are being conducted on core samples from the USW-G1 exploration hole in Yucca Mountain. Zeolite heating tests of core samples from UE25a-1 show density, volume, and weight changes that correlate with alteration of mineral assemblages. Hydrogen-deuterium ratios in water evolved from a clinoptilolite specimen from Yucca Mountain have been measured. Jacket seals leaked during the first attempt at high temperature exposure in the hydrothermal soak tests. Revised seals using temperature-cured epoxy are being developed. Data from strength tests for various types of tuff conducted at ambient pressure and 400{sup 0}C for 16 h are presented. A densely welded specimen showed a 40% reduction in strength.
Date: February 1, 1981
Creator: Wolfsberg, K.; Erdal, B.R. & Crowe, B.M. (comps.)
Partner: UNT Libraries Government Documents Department

Aspects of possible magmatic disruption of a high-level radioactive waste repository in southern Nevada

Description: The Nevada Test Site (NTS) region is located within the central section of a north-northeast-trending basaltic volcanic belt of late Cenozoic age, a part of the Quaternary volcanic province of the Great Basin. Future volcanism within the belt represents a potential hazard to storage of high-level radioactive waste within a buried repository located in the southwestern NTS. The hazards of future volcanism in the region are being characterized through a combination of volcanic hazards studies, probability determinations, and consequence analyses. Basaltic activity within the NTS regions is divided into two age groups consisting of relatively large-volume silicic cycle basalts (8 to 10 Myr) and rift basalts (< 8 to 0.3 Myr). This paper describes the processes of basaltic magmatism ranging from derivation of basalt melts at depth, through ascent through the upper mantle and crust, to surface eruption. Each stage in the evolution and dispersal of basaltic magma is described, and the disruption and potential dispersal of stored radioactive waste is evaluated. These data document areas of knowns and unknowns in the processes of basaltic volcanisms and provide background data necessary to assist calculations of radiation release levels due to disruption of a repository. 9 figures, 11 tables.
Date: October 1, 1982
Creator: Crowe, B.; Amos, R.; Perry, F.; Self, S. & Vaniman, D.
Partner: UNT Libraries Government Documents Department

Status of volcanic hazard studies for the Nevada Nuclear Waste Storage Investigations

Description: Volcanism studies of the Nevada Test Site (NTS) region are concerned with hazards of future volcanism with respect to underground disposal of high-level radioactive waste. The hazards of silicic volcanism are judged to be negligible; hazards of basaltic volcanism are judged through research approaches combining hazard appraisal and risk assessment. The NTS region is cut obliquely by a N-NE trending belt of volcanism. This belt developed about 8 Myr ago following cessation of silicic volcanism and contemporaneous with migration of basaltic activity toward the southwest margin of the Great Basin. Two types of fields are present in the belt: (1) large-volume, long-lived basalt and local rhyolite fields with numerous eruptive centers and (2) small-volume fields formed by scattered basaltic scoria cones. Late Cenozoic basalts of the NTS region belong to the second field type. Monogenetic basalt centers of this region were formed mostly by Strombolian eruptions; Surtseyean activity has been recognized at three centers. Geochemically, the basalts of the NTS region are classified as straddle A-type basalts of the alkalic suite. Petrological studies indicate a volumetric dominance of evolved hawaiite magmas. Trace- and rare-earth-element abundances of younger basalt (<4 Myr) of the NTS region and southern Death Valley area, California, indicate an enrichment in incompatible elements, with the exception of rubidium. The conditional probability of recurring basaltic volcanism and disruption of a repository by that event is bounded by the range of 10{sup -8} to 10{sup -10} as calculated for a 1-yr period. Potential disruptive and dispersal effects of magmatic penetration of a repository are controlled primarily by the geometry of basalt feeder systems, the mechanism of waste incorporation in magma, and Strombolian eruption processes.
Date: March 1, 1983
Creator: Crowe, B.M.; Vaniman, D.T. & Carr, W.J.
Partner: UNT Libraries Government Documents Department

Preliminary geologic map of the Sleeping Butte volcanic centers

Description: The Sleeping Butte volcanic centers comprise two, spatially separate, small-volume (<0.1 km{sup 3}) basaltic centers. The centers were formed by mildly explosive Strombolian eruptions. The Little Black Peak cone consists of a main scoria cone, two small satellitic scoria mounds, and associated lobate lava flows that vented from sites at the base of the scoria cone. The Hidden Cone center consists of a main scoria cone that developed on the north-facing slope of Sleeping Butte. The center formed during two episodes. The first included the formation of the main scoria cone, and venting of aa lava flows from radial dikes at the northeast base of the cone. The second included eruption of scoria-fall deposits from the summit crater. The ages of the Little Black Peak and the Hidden Cone are estimated to be between 200 to 400 ka based on the whole-rock K-Ar age determinations with large analytical undertainty. This age assignment is consistent with qualitative observations of the degree of soil development and geomorphic degradation of volcanic landforms. The younger episode of the Hidden Cone is inferred to be significantly younger and probably of Late Pleistocene or Holocene age. This is based on the absence of cone slope rilling, the absence of cone-slope apron deposits, and erosional unconformity between the two episodes, the poor horizon- development of soils, and the presence of fall deposits on modern alluvial surfaces. Paleomagnetic data show that the centers record similar but not identical directions of remanent magnetization. Paleomagnetic data have not been obtained for the youngest deposits of the Hidden Cone center. Further geochronology, soils, geomorphic, and petrology studies are planned of the Sleeping Butte volcanic centers 20 refs., 3 figs.
Date: July 1, 1991
Creator: Crowe, B.M. & Perry, F.V.
Partner: UNT Libraries Government Documents Department

Low-level radioactive waste (LLW) management at the Nevada Test Site (NTS)

Description: In 1978, the Department of Energy, Nevada Operations Office (DOE/NV), established a managed LLW disposal project at the Nevada Test Site (NTS). Two, sites which were already accepting limited amounts of on-site generated waste for disposal and off-site generated Transuranic Waste for interim storage, were selected to house the disposal facilities. In those early days, these sites, located about 15 miles apart, afforded the DOE/NV the opportunity to use at least two technologies to manage its waste cost effectively. The Area 5 Radioactive Waste Management Site (RWMS) uses engineered shallow-land burial cells to dispose packaged waste while the Area 3 RWMS uses subsidence craters formed from underground testing of nuclear weapons for the disposal of packaged and unpackaged bulk waste. The paper describes the technical attributes of both Area 5 and Area 3 facilities, the acceptance process, the disposal processes, and present and future capacities of both sites.
Date: December 31, 1998
Creator: Becker, B.D.; Gertz, C.P.; Clayton, W.A. & Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Status of volcanic hazard studies for the Nevada Nuclear Waste Storage Investigations. Volume II

Description: Volcanic hazard investigations during FY 1984 focused on five topics: the emplacement mechanism of shallow basalt intrusions, geochemical trends through time for volcanic fields of the Death Valley-Pancake Range volcanic zone, the possibility of bimodal basalt-rhyolite volcanism, the age and process of enrichment for incompatible elements in young basalts of the Nevada Test Site (NTS) region, and the possibility of hydrovolcanic activity. The stress regime of Yucca Mountain may favor formation of shallow basalt intrusions. However, combined field and drill-hole studies suggest shallow basalt intrusions are rare in the geologic record of the southern Great Basin. The geochemical patterns of basaltic volcanism through time in the NTS region provide no evidence for evolution toward a large-volume volcanic field or increases in future rates of volcanism. Existing data are consistent with a declining volcanic system comparable to the late stages of the southern Death Valley volcanic field. The hazards of bimodal volcanism in this area are judged to be low. The source of a 6-Myr pumice discovered in alluvial deposits of Crater Flat has not been found. Geochemical studies show that the enrichment of trace elements in the younger rift basalts must be related to an enrichment of their mantle source rocks. This geochemical enrichment event, which may have been metasomatic alteration, predates the basalts of the silicic episode and is, therefore, not a young event. Studies of crater dimensions of hydrovolcanic landforms indicate that the worst case scenario (exhumation of a repository at Yucca Mountain by hydrovolcanic explosions) is unlikely. Theoretical models of melt-water vapor explosions, particularly the thermal detonation model, suggest hydrovolcanic explosion are possible at Yucca Mountain. 80 refs., 21 figs., 5 tabs.
Date: January 1, 1986
Creator: Crowe, B.M.; Wohletz, K.H.; Vaniman, D.T.; Gladney, E. & Bower, N.
Partner: UNT Libraries Government Documents Department

Preliminary evaluation of the radioactive waste isolation potential of the alluvium-filled valleys of the Great Basin

Description: The occurrences, geologic features, hydrology, and thermal, mechanical, and mineralogical properties of the alluvium-filled valleys are compared with those of other media within the Great Basin. Computer modeling of heat conduction indicates that heat generated by the radioactive waste can be dissipated through the alluvium in a manner that will not threaten the integrity of the repository, although waste emplacement densities will be lower than for other media available. This investigation has not revealed any failure mechanism by which one can rule out alluvium as a primary waste isolation medium. However, the alluvium appears to rank behind one or more other possible media in all properties examined except, perhaps, in sorption properties. It is therefore recommended that alluvium be considered as a secondary isolation medium unless primary sites in other rock types in the Great Basin are eliminated from consideration on grounds other than those considered here.
Date: August 1, 1979
Creator: Smyth, J.R.; Crowe, B.M.; Halleck, P.M. & Reed, A.W.
Partner: UNT Libraries Government Documents Department

Low-level radioactive waste management at the Nevada Test Site -- Year 2000 current status

Description: This paper describes the technical attributes of the facilities, present and future capacities and capabilities, and provides a description of the process from waste approval to final disposition. This paper also summarizes the current status of the waste disposal operations.
Date: February 1, 2000
Creator: Becker, B.D.; Clayton, W.A.; Gertz, C.P. & Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Recurrence models of volcanic events: Applications to volcanic risk assessment

Description: An assessment of the risk of future volcanism has been conducted for isolation of high-level radioactive waste at the potential Yucca Mountain site in southern Nevada. Risk used in this context refers to a combined assessment of the probability and consequences of future volcanic activity. Past studies established bounds on the probability of magmatic disruption of a repository. These bounds were revised as additional data were gathered from site characterization studies. The probability of direct intersection of a potential repository located in an eight km{sup 2} area of Yucca Mountain by ascending basalt magma was bounded by the range of 10{sup {minus}8} to 10{sup {minus}10} yr{sup {minus}1 2}. The consequences of magmatic disruption of a repository were estimated in previous studies to be limited. The exact releases from such an event are dependent on the strike of an intruding basalt dike relative to the repository geometry, the timing of the basaltic event relative to the age of the radioactive waste and the mechanisms of release and dispersal of the waste radionuclides in the accessible environment. The combined low probability of repository disruption and the limited releases associated with this event established the basis for the judgement that the risk of future volcanism was relatively low. It was reasoned that that risk of future volcanism was not likely to result in disqualification of the potential Yucca Mountain site.
Date: March 1, 1992
Creator: Crowe, B.M.; Picard, R.; Valentine, G. & Perry, F.V.
Partner: UNT Libraries Government Documents Department

Geology and hydrogeology of the proposed nuclear waste repository at Yucca Mountain, Nevada and the surrounding area

Description: In late 1987 Congress issued an amendment to the Nuclear Waste Policy Act of 1982 which directed the characterization of Yucca Mountain, Nevada as the only remaining potential site for the Nation`s first underground high-level radioactive waste repository. The evaluation of a potential underground repository is guided and regulated by policy established by the Department of Energy (DOE), Nuclear Regulatory Commission (NRC), Environmental Protection Agency (EPA), Department of Transportation (DOT), and the US Congress. The Yucca Mountain Project is the responsibility of the DOE. The purpose of this field trip is to introduce the present state of geologic and hydrologic knowledge concerning this site. This report describes the field trip. 108 refs., 6 figs., 1 tab.
Date: July 1989
Creator: Mattson, S. R.; Broxton, D. E.; Crowe, B. M.; Buono, A. & Orkild, P. P.
Partner: UNT Libraries Government Documents Department

Physical processes and effects of magmatism in the Yucca Mountain region

Description: This paper describes initial studies related to the effects of volcanism on performance of the proposed Yucca Mountain radioactive waste repository, and to the general processes of magmatism in the Yucca Mountain region. Volcanism or igneous activity can affect the repository performance by ejection of waste onto the earth`s surface (eruptive effects), or by subsurface effects of hydrothermal processes and altered hydrology if an intrusion occurs within the repository block. Initial, conservative calculations of the volume of waste that might be erupted during a small-volume basaltic eruption (such as those which occurred in the Yucca Mountain region) indicate that regulatory limits might be exceeded. Current efforts to refine these calculations, based upon field studies at analog sites, are described. Studies of subsurface effects are just beginning, and are currently focused on field studies of intrusion properties and contact metamorphism at deeply eroded analog sites. General processes of magmatism are important for providing a physical basis for predictions of future volcanic activity. Initial studies have focused on modeling basaltic magma chambers in conjunction with petrographic and geochemical studies. An example of the thermal-fluid dynamic evolution of a small basaltic sill is described, based on numerical simulation. Quantification of eruption conditions can provide valuable information on the overall magmatic system. We are developing quantitative methods for mapping pyroclastic facies of small basaltic centers and, in combination with two-phase hydrodynamic simulation, using this information to estimate eruption conditions. Examples of such hydrodynamic simulations are presented, along with comparison to an historical eruption in Hawaii.
Date: December 31, 1991
Creator: Valentine, G.A.; Crowe, B.M. & Perry, F.V.
Partner: UNT Libraries Government Documents Department

Waste Management at the Nevada Test Site Fiscal Year 2001 Current Status

Description: The performance objectives of the U. S. Department of Energy's National Nuclear Security Administration Nevada Operations Office (NNSA/NV) Low-level Radioactive Waste (LLW) disposal facilities located at the Nevada Test Site transcend those of any other radioactive waste disposal site in the United States. Situated at the southern end of the Great Basin, 244 meters (800 feet) above the water table, the Area 5 Radioactive Waste Management Site (RWMS) has utilized a combination of engineered shallow land disposal cells and deep augured shafts to dispose a variety of waste streams. These include high volume low-activity waste, classified radioactive material, and high-specific-activity special case waste. Fifteen miles north of Area 5 is the Area 3 RWMS. Here bulk LLW disposal takes place in subsidence craters formed from underground testing of nuclear weapons. Earliest records indicate that documented LLW disposal activities have occurred at the Area 5 and Area 3 RWMSs since 1961 and 1 968, respectively. However, these activities have only been managed under a formal program since 1978. This paper describes the technical attributes of the facilities, present and future capacities and capabilities, and provides a description of the process from waste approval to final disposition. The paper also summarizes the current status of the waste disposal operations.
Date: May 2002
Creator: Becker, B. D.; Clayton, W. A. & Crowe, B. M.
Partner: UNT Libraries Government Documents Department

Stratigraphy of the Bandelier Tuff in the Pajarito Plateau. Applications to waste management

Description: The Bandelier Tuff within the Pajarito Plateau consists of a lower sequence of air-fall and ash-flow deposits (Otowi Member) disconformably overlain by an upper sequence of air-fall and ash-flow deposits (Tshirege Member). The ash-flow sequence of the Tshirege Member consists of three cooling units throughout much of the Pajarito Plateau. The lower cooling unit is formed by three to as many as six pyroclastic flow units; the middle and upper cooling units each consist of at least three pyroclastic flow units. The contact between the lower and middle cooling unit coincides with a pyroclastic flow unit contact. This horizon is a prominent stratigraphic marker within distal sections of the Tshirege Member. Major and trace element analyses of unaltered and altered samples of the Bandelier Tuff were determined by neutron activation and delayed neutron activation and delayed neutron activation techniques. Petrographic, granulometric and morphologic characteristics of the Bandelier Tuff were determined to provide background information on the suitability of the Tuff as a medium for radioactive waste disposal. The hydrologic characteristics of the Bandelier Tuff are controlled primarily by secondary features of the Tuff (cooling zones). These features vary with emplacement temperature and transport distance of the Tuff. Primary depositional features provide second order control on transport pathways in distal sections of the Tuff.
Date: April 1, 1978
Creator: Crowe, B.M.; Linn, G.W.; Heiken, G. & Bevier, M.L.
Partner: UNT Libraries Government Documents Department

An informal expert judgment assessment of subsidence mitigation options for low-level radioactive waste management sites on the Nevada Test Site

Description: An assessment of options to mitigate the effects of subsidence at low-level radioactive waste disposal sites on the Nevada Test Site was conducted using an informal method of expert judgment. Mitigation options for existing waste cells and future waste cells were identified by a committee composed of knowledgeable personnel from the DOE and DOE-contractors. Eight ranking factors were developed to assess the mitigation options and these factors were scored through elicitation of consensus views from the committee. Different subsets of the factors were applied respectively, to existing waste cells and future waste cells, and the resulting scores were ranked using weighted and unweighted scores. These scores show that there is a large number of viable mitigation options and considerable flexibility in assessing the subsidence issue with a greater range of options for future waste cells compared to existing waste cells. A highly ranked option for both existing and future waste cells is covering the waste cells with a thick closure cap of native alluvium.
Date: March 1, 1999
Creator: Crowe, B.M.; Leary, K.; Jacobson, R.; Bensinger, H. & Dolenc, M.
Partner: UNT Libraries Government Documents Department

Volcanic hazard studies for the Yucca Mountain project

Description: Volcanic hazard studies are ongoing to evaluate the risk of future volcanism with respect to siting of a repository for disposal of high-level radioactive waste at the Yucca Mountain site. Seven Quaternary basaltic volcanic centers are located a minimum distance of 12 km and a maximum distance of 47 km from the outer boundary of the exploration block. The conditional probability of disruption of a repository by future basaltic volcanism is bounded by the range of 10{sup {minus}8} to 10{sup {minus}10} yr{sup {minus}1}. These values are currently being reexamined based on new developments in the understanding of the evaluation of small volume, basaltic volcanic centers including: (1) Many, perhaps most, of the volcanic centers exhibit brief periods of eruptive activity separated by longer periods of inactivity. (2) The centers may be active for time spans exceeding 10{sup 5} yrs, (3) There is a decline in the volume of eruptions of the centers through time, and (4) Small volume eruptions occurred at two of the Quaternary centers during latest Pleistocene or Holocene time. We classify the basalt centers as polycyclic, and distinguish them from polygenetic volcanoes. Polycyclic volcanism is characterized by small volume, episodic eruptions of magma of uniform composition over time spans of 10{sup 3} to 10{sup 5} yrs. Magma eruption rates are low and the time between eruptions exceeds the cooling time of the magma volumes. 25 refs., 2 figs.
Date: May 1, 1989
Creator: Crowe, B.; Turrin, B.; Wells, S.; Perry, F.; McFadden, L.; Renault, C.E. et al.
Partner: UNT Libraries Government Documents Department

Isotopic prediction of eruption volume at continental volcanoes

Description: This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective of this project was to determine whether isotopic techniques can be used to assess the eruption potential and eruption volume of continental stratovolcanoes. Large-volume eruptions from stratovolcanoes pose significant hazards to population and infrastructure in many parts of the world. We are testing whether this technique will allow a short- to medium-term (decades to millennia) probabilistic hazard assessment of large-volume eruptions. If successful, the technique will be useful to countries or regions that must consider medium to long-term volcanic (e.g., nuclear waste facilities). We have begun sample acquisition and isotopic measurements at two stratovolcanoes, Pico de Orizaba in eastern Mexico and Daisen in western Japan.
Date: October 1, 1997
Creator: Perry, F.V.; Valentine, G.A. & Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Intermediate depth burial of classified transuranic wastes in arid alluvium

Description: Intermediate depth disposal operations were conducted by the US Department of Energy (DOE) at the DOE`s Nevada Test Site (NTS) from 1984 through 1989. These operations emplaced high-specific activity low-level wastes (LLW) and limited quantities of classified transuranic (TRU) wastes in 37 m (120-ft) deep, Greater Confinement Disposal (GCD) boreholes. The GCD boreholes are 3 m (10 ft) in diameter and founded in a thick sequence of arid alluvium. The bottom 15 m (50 ft) of each borehole was used for waste emplacement and the upper 21 m (70 ft) was backfilled with native alluvium. The bottom of each GCD borehole is almost 200 m (650 ft) above the water table. The GCD boreholes are located in one of the most arid portions of the US, with an average precipitation of 13 cm (5 inches) per year. The limited precipitation, coupled with generally warm temperatures and low humidities results in a hydrologic system dominated by evapotranspiration. The US Environmental Protection Agency`s (EPA`s) 40 CFR 191 defines the requirements for protection of human health from disposed TRU wastes. This EPA standard sets a number of requirements, including probabilistic limits on the cumulative releases of radionuclides to the accessible environment for 10,000 years. The DOE Nevada Operations Office (DOE/NV) has contracted with Sandia National Laboratories (Sandia) to conduct a performance assessment (PA) to determine if the TRU wastes emplaced in the GCD boreholes complies with the EPA`s 40 CFR 191 requirements. This paper describes DOE`s actions undertaken to evaluate whether the TRU wastes in the GCD boreholes will, or will not, endanger human health. Based on preliminary modeling, the TRU wastes in the GCD boreholes meet the EPA`s requirements, and are, therefore, protective of human health.
Date: April 1, 1999
Creator: Cochran, J.R.; Crowe, B.M. & Di Sanza, F.
Partner: UNT Libraries Government Documents Department