Approach to geologic repository post closure system performance assessment Page: 4 of 11
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
be thought of as being composed of three levels. The levels are
not completely distinct; a single model may sometimes be thought
of as in one level and sometimes in another, depending on how it
is used. The division between process and subsystem models,
however, is especially indistinct. For this reason the boundary
between process and subsystem models has been shown as a dashed
line on Figure 2.
Process models are usually deterministic numerical codes
that incorporate coupled interactions such as the interactions
among water, water vapor, gas, and heat flow. These models
closely represent the physical (chemical) processes that occur
and are used to evaluate the effects of parameter uncertainty by
conducting parameter sensitivity analyses over the ranges of
model input parameters that exist at the site.
Subsystem models are either deterministic or probabilistic
models, which are used in analysis of individual sequences of
processes and events that may occur at a repository site,
bounding analyses, or determinations of process uncertainty. An
example of a subsystem model is the waste-package model, which
incorporates chemical/geochamical, flow, stress, ard thermal
processes in an abstracted (simplified) form. Subsystem models
are used to investigate process uncertainty through incorporation
of the range of expected processes that could occur at the site.
System models are capable of describing combinations of
potential site scenarios (i.e., sequences of processes and events
that could occur at a site); they can be used to estimate the
effects of these combinations on the entire repository system.
Because they generally treat the combinations probabilistically,
they are useful in calculating complementary cumu'.ative
distribution functions for examining compliance with 40 CFR Part
191. These models, in comparison with the rest of the hierarchy,
incorporate the highest levels of abstraction.
The base of the hierarchy of models used in performance
assessment (Figure 2) is thought of as containing models that are
more complete. Toward the apex, models contain all of the major
components of mcdels at the base, but process descriptions are in
an abstracted (less detailed) form. For this reason, the models
toward the apex are useful in showing the sensitivity of the
system to variations in the parameters that describe processes
and events. The models toward the base are useful in deriving
information about the effects of uncertainties in those
parameters.
Iterative assessments of total-system performance can be
envisioned as beginning at either the base of the triangle or the
apex. Useful transfers of information between levels of the
hierarchy may be accomplished either upwards of downwards in the
triangle, When information is passed upwards, the results of
studies with process models may formulate input for subsystem
models, whose resultai are in turn used as a basis for
calculations with system models. In this way the uncertainties4
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Pahwa, S.B.; Felton, W. & Duguid, J.O. Approach to geologic repository post closure system performance assessment, article, August 1, 1992; Albuquerque, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc620018/m1/4/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.