scholarly journals A Demonstration of Dose Modeling at Yucca Mountain

1992 ◽  
Vol 294 ◽  
Author(s):  
Terri B. Miley ◽  
Paul W. Eslinger

ABSTRACTThe U. S. Environmental Protection Agency is currently revising the regulatory guidance for high-level nuclear waste disposal. In its draft form, the guidelines contain dose limits. Since this is likely to be the case in the final regulations, it is essential that the U.S. Department of Energy be prepared to calculate site-specific doses for any potential repository location. This year, Pacific Northwest Laboratory (PNL) has made a first attempt to estimate doses for the potential geologic repository at Yucca Mountain, Nevada as part of a preliminary total-systems performance assessment.A set of transport scenarios was defined to assess the cumulative release of radionuclides over 10,000 years under undisturbed and disturbed conditions at Yucca Mountain. Dose estimates were provided for several of the transport scenarios modeled. The exposure scenarios used to estimate dose in this total-systems exercise should not, however, be considered a definitive set of scenarios for determining the risk of the potential repository.Exposure scenarios were defined for waterborne and surface contamination that result from both undisturbed and disturbed performance of the potential repository. The exposure scenarios used for this analysis were designed for the Hanford Site in Washington. The undisturbed performance scenarios for which exposures were modeled are gas-phase release of 14C to the surface and natural breakdown of the waste containers with waterborne release. The disturbed performance scenario for which doses were estimated is exploratory drilling. Both surface and waterborne contamination were considered for the drilling intrusion scenario.

1993 ◽  
Vol 333 ◽  
Author(s):  
Edward C. Taylor ◽  
Lawrence D. Ramspott ◽  
William M. Sprecher

ABSTRACTThe U. S. Department of Energy (DOE) is developing a nuclear waste management system that will accept high-level radioactive waste, transport it, store it, and ultimately emplace it in a deep geologic repository. The key activity now is determining whether Yucca Mountain, Nevada is suitable as a site for the repository. If so, the crucial technological advance will be the demonstration that disposal of nuclear waste will be safe for thousands of years after closure. This paper assesses the impact of regulatory developments, legal developments, and scientific developments on such a demonstration.


Author(s):  
Sandra Dalvit Dunn ◽  
Stephen W. Webb ◽  
John Del Mar ◽  
Michael T. Itamura ◽  
Nicholas D. Francis

The Yucca Mountain Project (YMP) is currently designing a geologic repository for high level nuclear waste. The design encompasses two distinct phases, the pre-closure period where temperatures within the repository will be controlled by active ventilation, and the post-closure period where the repository will be sealed. A prerequisite for designing the repository is the ability to both understand and control the heat generated from the decay of the nuclear waste. This decay heat affects the performance of both the waste packages and the emplacement drift. The ability to accurately model the complex heat transfer within the repository is critical to the understanding of the repository performance. Currently, computational fluid dynamics codes are being used to model the post-closure performance of the repository. Prior to using the codes on the project they were required to be thoroughly validated. Eight pilot-scale tests were performed at the Department of Energy North Las Vegas Atlas Facility to evaluate the processes that govern thermal transport in an environment that scales to the proposed repository environment during the post closure period. The tests were conducted at two geometric scales (25 and 44% of full scale), with and without drip shields, and under both uniform and distributed heat loads. The tests provided YMP specific data for model validation. A separate CFD model was developed for each of the four test configurations. The models included the major components of the experiment, including the waste packages (heated steel canisters), invert floor, and emplacement drift (insulated concrete pipe). The calculated model temperatures of the surfaces and fluids, and velocities, are compared with experimental data.


2012 ◽  
Vol 5 (4) ◽  
pp. 3853-3905
Author(s):  
Y. V. Dublyansky

Abstract. A unique conceptual model envisaging conductive heating of rocks in the thick unsaturated zone of Yucca Mountain, Nevada by a silicic pluton emplaced several kilometers away is accepted by the US Department of Energy (DOE) as an explanation of the elevated depositional temperatures measured in fluid inclusions in secondary fluorite and calcite. Acceptance of this model allowed the DOE not to consider hydrothermal activity in the performance assessment of the proposed high-level nuclear waste disposal facility. Evaluation shows that validation of the model by computational modeling and by observations at a natural analog site was unsuccessful. Due to the lack of validation, the reliance on this model must be discontinued and the scientific defensibility of decisions which rely on this model must be re-evaluated.


1984 ◽  
Vol 44 ◽  
Author(s):  
M. J. Steindler ◽  
W. B. Seefeldt

Some nuclear waste is destined for disposal in deep geological formations. The disposal system for wastes from commercial nuclear activities, and perhaps also for high-level wastes from defense-related activities, is to be designed and operated by the Department of Energy (DOE) and licensed by the Nuclear Regulatory Commission (NRC). The Nuclear Waste Policy Act [1] outlines some of the procedures and schedules that are to be followed by DOE in carrying out its assignment in the disposal of high-level nuclear waste (HLW). The regulations of the NRC that deal with HLW [2] are only partly in place, and amendments (e.g., related to the unsaturated zone) are yet to be approved and issued. The Environmental Protection Agency (EPA) has issued only draft versions of the regulations pertaining to HLW disposal [3], but key features of these drafts are at present in adequate agreement with NRC documents. On the basis of the trends that have become evident in the last few years, the DOE will be required to substantiate performance predictions for all pertinent aspects of a repository, especially the performance of the engineered waste package. The basis for demonstrating that the waste package performance in the repository will be in concert with the requirements is data on the waste package materials. These key materials data must clearly be highly reliable, and DOE will be required to assure this reliability. This paper addresses the organization and functions that have been assembled to aid in establishing the quality of materials data that are important in the licensing of a waste repository.


Author(s):  
R. Glenn Vawter

The U.S. Congress recently approved the Yucca Mountain Project in Nevada as the site for the nation’s high level nuclear waste repository. The Project now moves into the licensing, construction and operating phases. The question posed by this paper is what organization approach is best suited to carry out those functions as well as the affiliated transportation and waste acceptance activities? Currently the U.S. Department of Energy and its contractors are responsible for the implementation of the Project. Other alternatives include a government corporation, private industry, a different U.S. government agency, or a combination of the above? There are pros and cons to each approach. This paper will present pros and cons and discuss the implications of each alternative. It will also discuss experience from other similar endeavors around the world. The U.S Federal Administration will need to consider this important question to assure the success of the program, because it is so important to the energy and national security of the nation. And its success or failure will set a precedent for repository programs around the world.


2014 ◽  
Vol 7 (4) ◽  
pp. 1583-1607
Author(s):  
Y. V. Dublyansky

Abstract. A unique conceptual model describing the conductive heating of rocks in the thick unsaturated zone of Yucca Mountain, Nevada by a silicic pluton emplaced several kilometers away is accepted by the US Department of Energy (DOE) as an explanation of the elevated depositional temperatures measured in fluid inclusions in secondary fluorite and calcite. Acceptance of this model allowed the DOE to keep from considering hydrothermal activity in the performance assessment of the proposed high-level nuclear waste disposal facility. The evaluation presented in this paper shows that no computational modeling results have yet produced a satisfactory match with the empirical benchmark data, specifically with age and fluid inclusion data that indicate high temperatures (up to ca. 80 °C) in the unsaturated zone of Yucca Mountain. Auxiliary sub-models complementing the DOE model, as well as observations at a natural analog site, have also been evaluated. Summarily, the model cannot be considered as validated. Due to the lack of validation, the reliance on this model must be discontinued and the appropriateness of decisions which rely on this model must be re-evaluated.


2002 ◽  
Vol 757 ◽  
Author(s):  
Thomas E. Kiess ◽  
Stephen H. Hanauer

ABSTRACTThe Yucca Mountain site was designated in July 2002 as the United States' location for a geological repository for spent nuclear fuel and other high-level radioactive wastes. This site designation was a watershed event in the history of the project, enabling the U.S. Department of Energy to seek a license from the U.S. Nuclear Regulatory Commission to construct and operate a geologic repository. Summarized below are the history and technical basis for this site designation and some key anticipated future events. Many of the significant events to date have been framed by the Nuclear Waste Policy Act (and Amendments) and the requirements of the regulatory standard.


1986 ◽  
Vol 84 ◽  
Author(s):  
M.D. Merz ◽  
F. Gerber ◽  
R. Wang

AbstractThe Materials Characterization Center (MCC) at Pacific Northwest Lab- oratory is performing three kinds of corrosion tests for the Basalt Waste Isolation Project (BWIP) to establish the interlaboratory reproducibility and uncertainty of corrosion rates of container materials for high-level nuclear waste. The three types of corrosion tests were selected to address two distinct conditions that are expected in a repository constructed in basalt. An air/steam test is designed to address corrosion during the operational period and static pressure vessel and flowby tests are designed to address corrosion under conditions that bound the condi ring the post-closure period of the repository.The results of tests at reference testing conditions, which were defined to facilitate interlaboratory comparison of data, are presented. Data are reported for the BWIP/MCC-105.5 Air/Steam Test, BWIP/MCC-105.1 Static Pressure Vessel, and BWIP/MC-105.4 Flowby Test. In those cases where data are available from a second laboratory, a statistical analysis of interlaboratory results is reported and expected confidence intervals for mean corrosion rates are given. Other statistical treatment of data include analyses of the effects of vessel-to-vessel variations, test capsule variations for the flowby test, and oven-to-oven variations for air/steam tests.


2004 ◽  
Vol 824 ◽  
Author(s):  
Lietai Yang ◽  
Miriam R. Juckett ◽  
Roberto T. Pabalan

AbstractThe electrical conductance or conductivity of three salt mixtures, Na-K-Cl-NO3, Ca-K-Cl and Ca-Na-Cl, were measured at 25, 50 and 70°C [77, 122, and 158 °F] as a function of relative humidity (RH). Mutual deliquescence and efflorescence RH (MDRH and MERH) values were determined based on the conductivity measurements. It was found that the conductivity of the three salt mixtures started to increase at RH values that are approximately 40 % of their MDRH and increased by 1to 2 orders of magnitude just before reaching the MDRH. At the MDRH, a significant increase in conductivity was observed. The MDRH and MERH for the Ca-K-Cl and Ca-Na-Cl mixtures were found to be approximately 15 % in the temperature range of 50 to 70 °C [122 to 158 °F]. The MDRH and MERH for the Na-K-Cl-NO3system were found to be approximately 54 % at 50 °C [122 °F] and decreased significantly with an increase in temperature.


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