Distributions of Concentration Limits for the Source Term in Performance Assessments

2004 ◽  
Vol 824 ◽  
Author(s):  
William M. Murphy ◽  
Steve Soldavini ◽  
Colin M. Gallagher
Keyword(s):  
Nuclear Waste ◽  
Source Term ◽  
Bimodal Distribution ◽  
Distribution Functions ◽  
Performance Assessments ◽  
Concentration Limit ◽  
Statistical Distributions ◽  
Radionuclide Concentration ◽  
Geologic Disposal ◽  
Concentration Limits

AbstractRadionuclide concentration limits are important parameters in performance assessments for geologic disposal of nuclear waste, but their statistical distributions are challenging to define. Thermodynamic solubilities provide an attractive theoretical constraint, but solubilities do not provide a basis for distribution functions, and concentration limits can exceed solubilities in irreversible systems. Distributions of natural concentrations are broad and do not correspond to distributions of concentration limits. Interpretations of natural nickel and lead concentrations suggest that they do not represent concentration limit distributions. Interpretation of groundwater data for dissolved calcium indicates a bimodal distribution, which hypothetically corresponds to a solubility-limited population and a population of values below the solubility limits.

Probabilistic Analysis of Human Intrusion in a High Level Nuclear Waste Repository in Salt Using Draft EPA Assumptions

1984 ◽  
Vol 44 ◽  
Author(s):  
William V. Harper ◽  
Gilbert E. Raines
Keyword(s):  
Nuclear Waste ◽  
Probabilistic Analysis ◽  
Discrete Event ◽  
Distribution Functions ◽  
Performance Assessments ◽  
Limiting Factors ◽  
Nuclear Waste Repository ◽  
Cumulative Probability ◽  
High Level Nuclear Waste ◽  
High Level

AbstractThe Office of Nuclear Waste Isolation (ONWI) has planned performance assessments that will quantify various performance measures for the eventual licensing of a repository in salt. In addition to studying “expected” conditions, selected discrete event scenarios must be analyzed. This paper presents a probabilistic analysis of a human intrusion scenario in which boreholes may be drilled into the repository, contact nuclear waste, and release the radionuclides to the environment. A stochastic analysis using draft EPA limiting factors regarding probability of drilling and quantities of water flow is compared to the proposed EPA 10,000 year limits. The years in which boreholes penetrate the repository are probabilistically determined in each iteration of the analysis. For each borehole, the probability of contacting radioactivity is an increasing function of time. When a borehole does make contact with radioactivity, the curie release of a given nuclide is a function of solubility limits and current inventory. Prediction intervals and complementary cumulative probability distribution functions are developed for the curie release as a fraction of the EPA limits. Radionuclide releases are small fractions of the EPA limits. This study shows that there is a high expectation that the EPA requirements would be met with a repository in salt.

Source-Term Constraints for the Proposed Repository at Yucca Mountain, Nevaida, Derived from the Natural Analog at PeÑa Blanca, Mexico

1991 ◽  
Vol 257 ◽  
Author(s):  
William M. Murphy ◽  
English C. Pearcy
Keyword(s):  
Nuclear Waste ◽  
Source Term ◽  
Yucca Mountain ◽  
Performance Assessments ◽  
Nuclear Waste Repository ◽  
Advective Transport ◽  
Silicate Minerals ◽  
Natural Analog ◽  
Rate Limiting ◽  
Nuclear Waste Forms

ABSTRACTThe source term for nuclear waste repository performance assessments can be constrained by the solubilities of radioelement-bearing solids and/or the rates of release of radioelements from nuclear waste forms. Both solubility and rate limits for the proposed repository at Yucca Mountain, Nevada, can be assessed using information from the natural analog at PeÑa Blanca, Mexico. Petrographic and field relations indicate that uraninite oxidation and transformation to secondary uranyl silicate minerals have been rapid relative to mass transport of uranium out of the PeÑa Blanca system. The rate limiting process for uranium removal is likely to be advective transport in groundwaters with uranium contents controlled by interactions with uranyl silicate minerals such as uranophane. A maximum limit on the rate of uraninite oxidation at PeÑa Blanca is calculated to be 0.032 tons of UO2 per year using geologic constraints on the amount of oxidation and the available time.

Performance Assessments of Geologic Repositories for High-Level Nuclear Waste: Are They Necessary or Sufficient?

2004 ◽  
Vol 824 ◽  
Author(s):  
Rodney C. Ewing
Keyword(s):  
Performance Assessment ◽  
Nuclear Waste ◽  
System Analysis ◽  
Regulatory Compliance ◽  
Performance Assessments ◽  
Data Uncertainty ◽  
Emergent Properties ◽  
Total System ◽  
High Level Nuclear Waste ◽  
High Level

AbstractPerformance assessments of geologic repositories for high-level nuclear waste will be used to determine regulatory compliance. The determination, that with a “reasonable expectation” regulatory limits are met, is based on the presumption that all of the relevant physical, chemical and biological processes have been modeled with enough accuracy to insure that a confident judgment of safety may be made. For the geologic disposal of high-level nuclear waste, this generally means that models must be capable of calculating radiation exposures to a specified population at distances of tens of kilometers for periods of tens to hundreds of thousands of years. A total system performance assessment will consist of a series of cascading models that are meant in toto to capture repository performance. There are numerous sources of uncertainty in these models: scenario uncertainty, conceptual model uncertainty and data uncertainty. These uncertainties will propagate through the analysis, and the uncertainty in the total system analysis must necessarily increase with time. For the highly-coupled, non-linear systems that are characteristic of many of the physical and chemical processes, one may anticipate emergent properties that cannot, in fact, be predicted. For all of these reasons, a performance assessment is not in and of itself a sufficient basis for determining the safety of a repository, but it remains a necessary part of the effort to develop a substantive understanding of a repository site.

Materials Interactions Relating to Long-Term Geologic Disposal of Nuclear Waste Glass

1986 ◽  
Vol 84 ◽  
Author(s):  
Ned E. Bibler ◽  
Carol M. Jantzen
Keyword(s):  
Nuclear Waste ◽  
Review Paper ◽  
Waste Glass ◽  
Waste Form ◽  
Glass Waste ◽  
Waste Package ◽  
Geologic Disposal ◽  
Nuclear Waste Glass ◽  
Backfill Materials

AbstractIn the geologic disposal of nuclear waste glass, the glass will eventually interact with groundwater in the repository system. Interactions can also occur between the glass and other waste package materials that are present. These include the steel canister that holds the glass, the metal overpack over the canister, backfill materials that may be used, and the repository host rock. This review paper systematizes the additional interactions that materials in the waste package will impose on the borosilicate glass waste form-groundwater interactions. The repository geologies reviewed are tuff, salt, basalt, and granite. The interactions emphasized are those appropriate to conditions expected after repository closure, e.g. oxic vs. anoxic conditions. Whenever possible, the effect of radiation from the waste form on the interactions is examined. The interactions are evaluated based on their effect on the release and speciation of various elements including radionuclides from the glass. It is noted when further tests of repository interactions are needed before long-term predictions can be made.

scholarly journals Higher-order dissipation in the theory of homogeneous isotropic turbulence

2016 ◽  
Vol 803 ◽  
pp. 250-274 ◽  
Author(s):  
Norbert Peters ◽  
Jonas Boschung ◽  
Michael Gauding ◽  
Jens Henrik Goebbert ◽  
Reginald J. Hill ◽  
...  
Keyword(s):  
Source Term ◽  
Isotropic Turbulence ◽  
Stokes Equations ◽  
Higher Order ◽  
Distribution Functions ◽  
Order Structure ◽  
Source Terms ◽  
Homogeneous Isotropic Turbulence ◽  
Higher Order Moments ◽  
Even Order

The two-point theory of homogeneous isotropic turbulence is extended to source terms appearing in the equations for higher-order structure functions. For this, transport equations for these source terms are derived. We focus on the trace of the resulting equations, which is of particular interest because it is invariant and therefore independent of the coordinate system. In the trace of the even-order source term equation, we discover the higher-order moments of the dissipation distribution, and the individual even-order source term equations contain the higher-order moments of the longitudinal, transverse and mixed dissipation distribution functions. This shows for the first time that dissipation fluctuations, on which most of the phenomenological intermittency models are based, are contained in the Navier–Stokes equations. Noticeably, we also find the volume-averaged dissipation $\unicode[STIX]{x1D700}_{r}$ used by Kolmogorov (J. Fluid Mech., vol. 13, 1962, pp. 82–85) in the resulting system of equations, because it is related to dissipation correlations.

Comparison of International Source-Term Codes

1993 ◽  
Vol 333 ◽  
Author(s):  
W. Zhou ◽  
M. J. Apted ◽  
P. Robinson
Keyword(s):  
Nuclear Waste ◽  
Preliminary Analysis ◽  
Source Term ◽  
Near Field ◽  
Different Types ◽  
Solution Methods ◽  
Initial Comparison ◽  
Models Comparison ◽  
The Impact ◽  
Transport Factors

ABSTRACTSource-term codes to predict the release of radionuclides from nuclear waste packages have been developed and implemented worldwide. A survey and initial comparison of the attributes and capabilities of 13 international source-term codes was recently completed. This preliminary analysis focused on comparison of transport factors/processes and solution methods. This initial comparison is a necessary first step in a properly-conceived, systematic benchmarking of source-term codes. Advantages of such a comparison include assurance of the mathematical correctness of implemented models, comparison and quantification of variances introduced by different types of simplifications, and identification and quantification of the impact of near-field processes.

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