Savannah River Laboratory DOSTOMAN code: a compartmental pathways computer model of contaminant transport Page: 3 of 15
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heterogeneous and subject to change and environmental transport is governed
by a variety of physical, chemical, and biological processes that are diffi-
cult to quantify. In spite of these difficulties and uncertainties, trans-
port estimates must be made in order to assess the hazard associated with
existing disposal sites or to evaluate the suitability of new ones. For.
example, federal regulations1-2 governing the licensing of radioactive waste
disposal sites require estimates of long term transport. For low-level
waste, predictions are required to 500 years; for high-level waste they are
required to 10,000 years. It is reasonable to expect analogous requirements
to be established eventually for hazardous chemical waste sites.
One method of predicting transport through complex environmental
systems is by compartmental modeling. Developed and used extensively in
biological tracer applications,3-6 the compartmental method has only
recently been applied to environmental transport problems.7-9
Although not very elegant, compartmental modeling is an extremely
practical method for making transport predictions. It is a semiempirical
technique in which complex environmental transport pathways are approximated
as a series of discrete, interconnected, homogeneous compartments. An
environmental compartment is conceptually analogous to the continuous-flow,
stirred-tank reactor (CFSTR) used in chemical engineering reactor modeling.
Material accumulation in a CFSTR is dependent on influent flow concentration
and various gains and losses within the reactor vessel. An environmental
compartment is essentially a CFSTR in which material inputs, material
outputs, and reactions are approximated as first-order processes and thus
are quantified by first-order rate constants. The rate constants are given
the name transfer coefficients and are based either on field data,
laboratory data, or theory.
The time rate of change of material inventory in a given compartment is
given by a first-order differential equation. A complete compartmental
model consists of a series of simultaneous, linear, first-order differential
equations. Solution of the set of equations yields compartment inventories
as a function of time. Generally, closed-form analytical solutions are
possible only for simple systems. For example, systems consisting of com-
partments in series with unidirectional transport are described by a set of
equations identical to those for a radioactive decay chain. Solution of the
set of equations yields the Bateman equations.10 Systems with only a few
compartments and bidirectional transfer, such as those encountered in many
biological applications, can be solved analytically using Laplace trans-
forms.11 A four compartment system which includes the transport of radio-
active daughters of a transuranic nuclide was solved by the eigenvalue
technique. For systems containing more than three compartments with either
multiple inputs to any given compartment or bidirectional transport, the
analytical techniques mentioned above are generally not practical and
numerical methods are usually required.12 One such large system is a 70
compartment model used to estimate long term dose to man due to shallow land
burial of radioactive wastes at the Savannah River Plant.7
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King, C M; Wilhite, E L; Root, Jr, R W; Fauth, D J; Routt, K R; Emslie, R H et al. Savannah River Laboratory DOSTOMAN code: a compartmental pathways computer model of contaminant transport, article, January 1, 1985; United States. (digital.library.unt.edu/ark:/67531/metadc1055609/m1/3/: accessed November 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.