ML20024E575
| ML20024E575 | |
| Person / Time | |
|---|---|
| Issue date: | 05/31/1983 |
| From: | Thomas Nicholson NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| Shared Package | |
| ML20024E572 | List: |
| References | |
| TASK-ES-115-4, TASK-RE REGGD-03.XXX, REGGD-3.XXX, NUDOCS 8308150313 | |
| Download: ML20024E575 (25) | |
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~ U.S. NUCLEAR REGULATORY COMMISSIUN 0
'n OFFICE OF NUCLEAR REGULATORY RESEARCH May 1983 i
i Division 3 I
DRAFT REGULATORY GUIDE AtlD VALUE/ IMPACT STATEMENT Task ES 115-4 Q**C M $
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Contact:
T. J. Nicholson (301) 427-4585 8
GUIDELINES FOR MODELING GROUND-WATER TRANSPORT OF RADI0 ACTIVE AND NONRADI0 ACTIVE CONTAMINANTS AT TAILINGS DISPOSAL SITES A.
INTRODUCTION j
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Anapplicantforanewlicenseorrenewalofanexistinglicensgtoreceive, possess, or use source material in conjunction with uranium, mill n -is required by S 40.31, " Applications for Specific Licenses," of 10 CFR,Part 40, " Domestic Licensing of Sortce Material," to provide, among other t gs[proposedwritten specifications relating to milling operations and the disposition of the byproduct material to achieve the requirements an bjhetives set forth in Part 40.
Each application must clearl demonst a e how these requirements and objectives have been addressed.
Thus the ap ichnt must assess potential i
ground-water seepage, chemical leaching o.f\\ tailings piles and impoundments, and associated transport of radioactive an'd Jo'nradioactive contaminants in ground water.
This may involve he use of models.
This draft regulatory guide dis-cusses the use of models, o dicti'ng ground-water contaminant. transport associated wit -tai in hisposal activities at uranium recovery facilities.
It provide utdance on describing the models chosen and their reliability, validity, and u d.
Modeling at in situ uranium solution mining facilities is not covered.
Any guidance in this document related to information collection activities has been cleared under OMB Ciearance No. 3150-0020.
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DISCUSSION c
l The dispostil of uranium mill tailings may involve environmental impacts on f
the local ground-water system.
To determine the level of impact, an assessment k
This regulatory guide and the associated value/ impact statement are being issued in draf t form to insol re (D
the puplic in the early stages of the development of a regulatory positten in this area. They nave net received ccoolete staff review and do not represent an of ficial NRC staf f position.
g Public coments are being solicited on both drafts, the guide (including any implementation scheoule) anc OCD the value/ impact statement. Comments on the value/imoact statement should he accompanied ey suceertine ID W ><
data.
Coments on both draf ts should be sent to the Secretary of the C mmissicn.A'UG. 5
%3 utetort t %c f b2 fy Commission, Warhington, D.C. 20555 Attention: Docketing'and Service 3ranc3 ny Ox.
03A r"l-Requests f?r single copies of draft guides (which may be reoroduced) Jr #Se DiaCe9ent "n 96 lutemat.
. D3.0 distributfon list for single cooles of future draf t guices in soecific dietsmns snoul1 ?e mace "t
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writing to the U.S. NuCItar 4egulatory Commission. %.lington, 3.C. D555. ittantiye:
Ibrot*n.
Diviston of Technical Inforeation 4nd Document Control.
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is needed of ground-water seepage, chemical leaching, and. contaminant transport 7')
in ground water.
The assessment may include the use of models, including a
computer codes, to characterize the potential environmental consequences.
Regu-latory Guide 3.8, " Preparation of Environmental Reports for Uranium Mills,"
requests information on ground-water systems in sufficient detail to facilitate an independent review of the effects of construction and operation of uranium recovery facilities on the ground-water resource.
Also discussed is the use of models to predict such effects as changes in ground-water levels, disper-sion of contaminants, and eventual transport through aquifers to surface-water bodies.
1.
GROUNO-WATER SEEPAGE ANALYSIS Since ground-water conditions differ greatly at the various uranium recovery facilities, this discussion is for the general case of combined saturated and partially saturated flow conditions.
An important consideration in choosing the appropriate model is that the assumptions inherent in the analytical
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method chosen to characterize the ground-water sys' tem be compatible with the field conditions and seepage control design criteria.
For example, a computer code that was developed exclusively for simulating ground-water flow in non-deformable saturated parous media is not appropriate for analyzing ground-water seepage in saturated or partially saturated mill tailings subject to compac-tion.
Further, it is important that the solution techniques chosen be compat-ible with the ground-water flow conditions and be stable over the field of interest.
For example,' analysis of partially saturated flow conditions involves solvino nonlinear equations that are difficult to handle, either numerically or analytically.
Numerical instabilities can arise from large contrasts of the moisture content and pressure head associated with an advancing wetting front in unsaturated media.
The numerical, methods available vary in complexity from simple graphical methods such as flow nets to sophisticated computer codes.
The conventional l
techniques for solving ground-water seepage and dewatering problems can be found in engineering textbooks such as Reference 1.
An excellent discussion of modeling techniques for ground-water evaluation is presented in Reference 2.
Recently, the TRUST code, a sophisticated computer code that can handle deform-able media under partially saturated conditions with fluid and particle
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l density variations has been documented (Ref. 3).
It is suggested that refer-ence be made to the TRUST code or a comparable code if computer modeling of ground-water seepage is anticipated.
A critical aspect of selecting and applying the model is that it contain valid assumptions and good numerical controls and, for transient solutions, be stable over time.
An important quality control procedure is to verify the model against a different data base to understand its capabilities and limitations in simulating the same system under different conditions.
The initial and boundary conditions, derived from field investigation, depend on the seepage control design features such as tailings pond liners, dewatering systems, and recovery wells.
Testing techniques for investigating the natural ground-water system are discussed in a draft branch technical posi-tion.* A more definitive discussion of this subject is found in Reference 4.
Models can be used for assessing the effectiveness,of various design features for seepage control at a particular site (Ref. 5).
The principal objective in modeling is to simulate the seepage paths, ground-water bulk velocities, and mass / time seepage rates.
Commonly, the seepage analysis is for steady-state conditions, yet just as important is time-variant behavior if seepage paths and (f
flow rates for natural conditions are significantly disturbed by tailings disposal activities.
The choice of the numerical solution technique depends on the field condi-tions and level of detail desired.
For example, flow net constructions are relatively simple and least time consuming; yet they can become extremely complicated and ultimately impossible if large permeability contrasts and moving boundaries exist (Ref. 1).
Large fluctuations of the water table elevation or the presence of a perched water table can further complicate and limit the use of graphical solutions.
Finite difference or finite element techniques, which are fundamentally simple, can solve simultaneous equations that describe the combined saturated and partially satu' rated systems and therefore may be more i
favorable.
For complicated geometries and boundary conditions, the finite ele-ment approach 'may be more applicable.
The user's manual for the FEMWATER code, a finite element ground-water flow model for saturated-unsaturated porous A"Hydrogeologic Characterization of Uranium Solution Mine and Mill Tailings l
Disposal Sites," WM-8203, July 1982; copies are available on request from i hj Chief, Uranium Recovery Licensing Branch, U.S. Nuclear Regulatory Commission, Mail Sto,p 905-S5, Washington, DC 20555, 7
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media, has an example seepage pond problem solution (Ref. 6).
Oster (Ref. 7)'
provides a review of ground-water flow and transport models for the unsaturated j{
zone.
l 2.
CHEMICAL LEACHING ANALYSIS I
Contaminant transport depends on contaminant loading at the source, chemical 1eaching, and continued mobility, as well as ground-water movement.
The prin-cipal radionuclides of interest (radium-226, uranium-238 and -234, thorium-230, and lead-210), chemical contaminants associated with the process reagents (chloride, nitrate, and sulfate), and heavy metals in the ore -(selenium, arsenic, i
molybdenum, and vanadium) are subject to chemical leaching and mobilization.
i Important factors in determining the concentrations of the contaminants during transport for different chemical conditions (e.g., pH and Eh variations), are i
the degree of initial loading, leaching and subsequent oxidation / reduction, dissolution / precipitation, and sorptive reactions.
The chemical partitioning of a contaminant between the solid and liquid phases in an aqueous system can be determined by (1) laboratory experiments, (2) field experiments, (3) field measurements at existing contaminated sites, GE and (4) geochemical models (Ref, 8). The success of all four methods is based on the accuracy of determining and representing the chemical character-istics of the (1) native ground water, (2) leaching solutions, (3) host rock, including the uranium ore, its daughter products and sediment mineralogy, and (4) mitigating agents used to immobilize the contaminants by chemical or physical means, such as lime or limestone, tailings pond liners, and grout.
Laboratory experiments using column or batch studies can provide insights
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into the leaching mechanisms and sorptive ' properties but' have. drawbacks owing to difficulty in duplicating field conditions such as maintaining anoxic condi-tions (Ref. 8).
Field experiments, therdfore, are the most reliable method, yet require numerous field tests (Ref. 8).
The previously mentioned draft branch technical position on hydrogeologic characterization provides guidance on basic field investigations needed. Williams discusses the limitations and i
advantages of both techniques (Ref. 4}.
Examination of existing tailings sites and analysis of contributing factors of leaching behavior of radium, thorium, 4
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uranium, and related nonradioactive constituents is also valuable for evaluating the potential for leaching at a particular site (Ref. 9).
The laboratory method presently used for collecting chemical leaching data is the single pass-through column test.
Gee et al. describe the laboratory apparatus, methods, conditions, and analysis procedures for performing such tests (Ref. 10).
The columns are filled with the tailings, either untreated or treated depending on the experiment's objective, and are repeatedly flushed with ground water or rain water collected at the mill location of interest (Ref. 10).
The column material is analyzed for leachant chemistry (pH, Eh, and electrical conductivity (EC)), average pore volume, particle density, average bulk density, and leaching rate (Ref.10).
Separately, the tailings are char-acterized for pH, Eh, and cation exchange capacity (Ref. 10).
The leached solutions are analyzed for chemical constituents (i.e., calcium (Ca), magnesium l
(Mg), sodium (Na), iron (Fe+2, +s),. manganese (Mn),' silica (Si), aluminum '(A1),
arsenic (As), selenium (Se), molybdenum (Mo), lead (21oPb), thorium (2soTh),
uranium (23s,2ssV), radium (2ssRa), sulfate (50 ), chlorine (C1), and nitrate 4
(NO ) (Ref. 10).
The resultant effluent is analyzed' against previous pore 3
t" volume solutions to generate a time-dependent seepage / leach data inventory.
In order to both analyze and predict chemical leaching and mobility at a v
given tailings disposal site for a variety of management alternatives, an aqueous chemical model* may be used.
The important factors in developing and using an aqueous chemical model are:**
a.
The representative chemical reactions being solved, b.
The chemical equilibrium or mass balance assumptions upon which the model is based, c.
The reliability of the equilibrium constants or free energies used in the model, d.
Redox state assumptions of the aqueous system, o
AAn aqueous chemical model is defined in Reference 11 as "a theoretical con-struction which allows us to predict the phermodynamic properties of elec-trolyte solutions."
xxSee Reference 11 for a detailed description.
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The total number of complexes considered, 7
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The carbonate system considerations, and j
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The temperature corrections incorporated into the model.
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An excellent review of geochemical modeling that would be useful in iden-tifying the geochemical processes controlling the concentration of dissolved constituents is found in Reference 12.
A computer program incorporating ura-nium speciation and mineralogy into an aqueous chemical model for conducting chemical equilibrium analyses of natural waters, "WATEQ3 - A Geochemical Model with Uranium Added," was documented following verification (Reference 13).
However, since the WATEQ3 model deals with input data from solutions, not solids, it can only be used to detensine whether the minerals in its data bank are over saturation and should precipitate in the resultant leachate. To model leaching / precipitation mechanisms, it is important that'the chemical model be capable of mass transfer from the liquid to solid phases and vice versa, for example, EQ6 (Ref. 14), PHREEQUE (Ref. 15), and EQUILIB (Ref. 16).
At present, modeling of mill tailings ~1eaching is extremely difficult because of the inabil-ity to quantify the tailings mineralogy and because of the undetennined and ggg.
possibly nonsingular thermochemical data for a significant portion of the amorphous reactive constituents.
La'ngmuir (Ref.17) provides a compilation of thermodynamic data that would be useful.
Geochemical models can be used for assessing the chemical causes for changes in the permeability of liner materials (Ref.18).
Peterson et al. (Ref. 18) used the ion speciation-solubility portions of the WATEQ3 (Ref. 13) and MINTEQ (Ref. 19) codes to test solubility hypotheses for various liner materials reacted with tailings solutions and demonstrated the usefulness of these codes to guide the analyses of important constituents and parameters for these solu-i tions. Other tailings disposal management decisions dealing with prediction of contaminant transport based on solubility controls can be aided by similar-geochemical modeling efforts.
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3.
CONTAMINANT TRANSPORT ANAL.YSIS The transport analysis can not proceed until the ground-water flow field and the leachate concentrations of the contaminants versus seepage time or volume are defined.
The important aspects of the transport analysis are the delineation of the flow pathways, the evaluation of the advective, dispersive, and diffusive components of ground-water transport, and the chemical and physical interaction between the contaminants and the surrounding fluids and solids.
The analysis may be a simple vectcr analysis in conjunction with graphical methods such as flow nets or solution of the advection-dispersion equation using analytic or digital computer models.
The solution method chosen is based on the complexity of the ground-water flow field, the boundary condi-tions, the detail desired, and quantity and quality of data available.
- Often, conditions are too complicated for use of hand-drawn flow nets or one-dimensional analyses.
Prior to selecting the contaminant transport model, the recommended approach is to list the assumptions chosen for the given site, using, for r-example, the following questions:
a.
Are the tailings and underlying materials under hydraulically saturated or partially saturated conditions?
b.
To what extent are the tailings and underlying materials homogeneous?
c.
Are the hydraulic flow properties isotropic?
d.
Is the solution method for steady-state or transient conditions?
e.
Is the ground-water flow predominately uniform?
f.
What is the nature of the initial source term and its mechanism and geometry of release?
g.
What is the relative importance and effect of such factors as chemical reactions, biological transformations, and radioactive decay on transport concentrations?
o An important consideration in contaminant transport analysis is the chemical and physical interactions between soluble contaminants and solids.
For acid tailings, the simple Kd (distribution coefficient) approach may not be very effective.
The major sink process is neutralization of the acidic seepage l
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l by the native sediments and ground water with subsequent contaminant precipita-7 tion, coprecipitation, and scavenging within the reaction products.
Solubility
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l product constraints appear to better describe the process and are outlined in Ref. 20.
r' Numerous textbooks (e.g., Refs. 8, 21, 22) and technical professional journals (e.g., Refs. 23-26) provide methods and examples for solving the various governing equations and underlying assumptions.
The FEMWASTE code, a i
finite-element model for waste transport through porous media, is compatible with the previously cited FEMWATER code (Ref. 27).
The FEMWASTE use 's manual includes an example solution for the transport aspects of the seepage pond problem, handling hydrodynamic dispersion, chemical sorption, and first-order decay (Ref. 27).
C.
REGULATORY POSITION Modeling may be needed to evaluate the potential impacts of contaminant transport at a uranium recovery facility on the ground-water system. This section. identifies the technical information acceptable to the NRC staff to dg describe (1) the relevant site-specific data collection activities, (2) model input parameters and their charscterization, (3) modeling procedures, and (4) analysis techniques for predicting radioactive and nonradioactive trans-port associated with uranium recovery operations.
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g The applicant should provide a rationale for selecting the model with emphasis on compatibility between the model's inherent assumptions and the Q
site conditions.*
k The applicant should provide information on the following subjects:
(1) site-specific data collection needs for modeling, (2) model input param-eters and their characterization, (3) model development, (4) modeling proce-dures, and (5) model results in terms 'f fluid potential (head) and solute o
concentrations in time and space.
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Guidance on documentation of a seldcted computer code is'available in NUREG-0856, " Draft Technical Position on Documentation of Models," December 1981.
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SITE-SPECIFIC DATA COLLECTION ACTIVITIES The applicant should indicate the site-specific data used in the modeling effort. The applicant's Environmental Report should provide much of the detailed geologic, geochemical, and hydrologic site characteristics needed in j
the modeling effort.
Reference should be made to the relevant sections of the Environmental Report where the data are provided.
Table 1 lists the recom-mended site-specific data needs for modeling tailings disposal sites.
Not all the data in Table 1 may be needed for every site depending upon the nature of the contaminant movement and geologic and hydrologic conditions.
j Specifically, the discussion should identify the method of data collec-tion, its location in a geologic, hydrologic, spatial, and temporal context, and the assumptions associated with the testing or collection method.
For example, the discussion on saturated hydraulic conductivity studies should state when and where the core samples were collected or the field test was performed, and in which hydrogeologic unit.
If laboratory studies were con-ducted, a comparison of test versus in situ field conditions is warranted.
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This guidance also applies to geochemical parameter studies.
For example,
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sample collection and preservation details and analytical procedures used to obtain the chemical data should be included.
I 2.
MODEL INPUT PARAMETERS i
A listing of the model input parameters, including their numerical values, should be provided.
If the values were not obtained directly from field or laboratory studies, a discussion of their characterization is needed.
For example, if potentiometric head levels are used as input parameters,'each value not derived from field observations should be identified (e.g., potentiometric level contouring approximations).
Further, the method of data processing (e.g., hand contouring, distance weighting of data, polynomial interpolation, or least squar'es) for spatial characterization should be identified and refer-enced (see Reference 28).
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r Table 1 m
Recommended Site-Specific Data Needs for 2
Modeling Tailings Disposal Sites
- 1.
Depth to water table, including perched water tables, if present.
2.
Distance to nearest points of ground-water, spring-water, or surface-water usage, including well and spring inventory survey.
3.
Ratio of pan evaporation to precipitation, minus runoff by month for a period of 2 years or longer.
4.
Water table contour map.
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5.
Magnitude of annual water table fluctuation.
6.
Stratigraphy and geologic structure to base of shallowest confined aquifer.
7.
Baseflow data on perennial streams traversing or adjacent to disposal-site.
8.
Chemistry including pH, Eh, temperature, and solute concentrations of major minerals and trace constituents of ground water in aquifers, confining units, and waste leachate emanating from the tailings disposal facility.
9.
Laboratory measurements of hydraulic conductivity, effective porosity, and mineralogy of core and grab samples from the disposal site for each p%
hydrogeologic unit of the unsaturated.and saturated (to base of 7
shallowest confined aquifer). zones.
Unsaturated hydraulic conductivity to be measured for different moisture contents and pressure heads.
10.
Neutron moisture meter measurements of moisture content in the unsaturated zone made in specially constructed holes.
11.
In situ measurements of soil moisture tension in upper 15-30 feet (4.5-9.0 m) of the unsaturated zone.
12.
Three-dimensional distribution of hydraulic head in all saturated hydrogeologic units to base of shallowest confined aquifer.
13.
Field measurements of transmissivity and storage coefficients of saturated porous media using pumping, bailing, or slug tests.
I 14.
Definition of recharge and discharge areas for unconfined and shallowest confined aquifers.
1 15.
Field measurements of dispersivity coefficients.
16.
Laboratory or field determination of the solubility product constraints for movement of important dissolved ions through all hydrogeologic units.
17.
Laboratory determination of adsorption /fon exchange constraints for l
movement of important dissolved' ions through all hydrogeologic units.
Modified after Reference 29.
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a 3.
M0_ DEL DEVELOPMENT s
i Information on the model development should be provided.
The discussion 2
should include the following topics:
Theoretical basis of the model, including the model assumptions and a.
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physical and/or chemical laws being considered (Ref. 30),
f' b.
Governing equations or reactions being solved, c.
Numerical solution techniques or methods, d.
Calibration techniques used to verify the model, e.g., the applicant l
could run hydrologic model comparisons with the TRUST code (Ref. 3) i using the same data base to verify the submitted model, Analysis procedures for evaluating the model results and predictions, e.
f.
Error analysis of the model and its inpyt parameters.
If the applicant uses an existing code to implement a particular model, reference should be made to the source material, including the user's manual
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or established procedures document.
The discussion should state and explain j k.*
any modifications made to the model.
If substantial changes to the existing l
model were necessary to handle the site-specific conditions and assumptions, l
a detailed discussion following the previously listed discussion topics should be provided.
4.
MODELING PROCEDURES Information on modeling procedures should be provided.
Specifically, documentation of the computer program or analytical method is needed.
This may involve transmittal of the computer code listing and technical reports.
l If physical or analog models are use'd, a visit by NRC technical reviewers to analyze and observe test runs of the model may be necessary.
In all cases, a user's manu'al should be provided wit'h a companion document outlining the input data and procedures implemented.
If computer plots are generated, a discussion of graphic capabilities and inherent error bands are warranted.
The NRC technical reviewers will consult with the applicant and its contrac-tors for independent-verification of model development, procedures, and results..
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Information on the quality assurance program to independently check the model and results should be provided.
For example, the procedures to deter-y mine the validity of the input parameters, governing equations, and numerical solution techniques are important and should be described. The values of input parameters and quantitative results should be characterized for statis-tical moments and error analysis.
5.
MODEL RESULTS At the conclusion of the modeling effort, the following data should be included on the expected inputs and results for modeling ground-water flow, chemical leaching, and transport of radioactive constituents and other possible contaminants associated with uranium recovery operations.
5.1 Near-Field Zone
- The discussion on the near-field zone should include:
a.
Graphical presentations of data and modeling results (i.e., cross-sections or multidimensional profiles);
b.
For unsaturated-saturated flow modeling:
(1) Moisture content variations as a function of depth and pressure
- head, (2) Unsaturated hydraulic conductivity values as a function of j
pressure head, (3) Pressure head as a function of time, (4) Vertical and horizontal setpage model velocity vector plots and distributions of pressure head, total head, and moisture con-tent on cross-sectional diagrams at selected locations depend-ing on site conditions; AHear-field zone means the zone affected by vertical or horizontal seepage from the tailings pile in the immediate vicinity of the tailings pile or impoundment.
It includes the unsaturated zone or perched water table below 9
the tailings pile and above the regional perennial water table. The complex-y ity of the site-specific hydrogeology will dictate the horizontal and vertical extent of this zone.
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c.
For saturated flow modeling:
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~(1) Distribution of saturated hydraulic conductivity values, (2) Distribution of effective porosity values, (3)
Potentiometric levels and gradients as a function of time and
- distance, (4) Flow path computations, including flow field characterization (e.g., flow nets, velocities);
d.
For geochemical modeling:
(1) Chemical analyses of the uranium ore, gangue minerals, ground water, leaching reagents, and leachate, including temperature, pH, and Eh conditions, (2) Mineralogy of the sediments, liners, and tailings, (3) Chemical reactions considered, (4) Thermochemical data used for the chemical reactions considered, c' '
(5). Kinetic data used for the chemical reactions considered, jc; (6) Calculations of the speciation of uranium, daughter products, and other potential contaminants and degree of chemical satura-tion with respect to these solid phases, (7) Calculations of the net adsorption and mass transfer of the principal contaminants, (8) Overall assessment of the dissolution / precipitation trends for the solid phases of the radioactive and nonradioactive contami-nant materials along the ground-water flow paths, (9) An estimation should be made of the effect that reaction
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kinetics may have on the modeling results if a purely equilib-rium thermodynamic model was used to simulate the system; i
e.
For transport modeling:
(1)
Initial concentration d1stributions and release model, f
(2) Dispersivity tensor values for the geologic media, (3) Retardation faccors, s
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l (4) Diffusion coefficients,
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l (5) Radionuclide and other contaminant chemical concentrations as a function of time and distance, (6) Concentration distribution plots for the various time and T-~
boundary conditions.
5.2 Far-Field Zone
- The discussion on the far-field zone should include:
a.
Graphical presentation of geologic and hydrologic data (i.e., hydro-geologic unit stratigraphy and flow paths),
b.
Potentiometric levels as a function of time and location, c.
Hydraulic properties (i.e., hydraulic conductivities, effective porosity, and dispersivities),
d.
Flowpath computations, e.
Chemical composition of ground water, leachate, and mineralogy of
. sediments,
,.g, f.
Chemical interactions and transport computations using near-field zone results.
- Far-field zone means the zone beyond the immediate vicinity of the tailings pile or impoundment.
The complexity of the site-specific hydrogeologic flow system will dictate the horizontal and vertical extent of the zone.
c.
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REFERENCES h
1.
K. R. Rushton and S. C. Redshaw, Seepage and Groundwater Flow, John Wiley and Sons, Ltd., New York, New York, 1979.
2.
T. A. Prickett, "Modeling Techniques for Groundwater Evaluation," in V. T. Chow, Ed., Advances in Hydrosciences, Academic Press, New York, New York, Vol. 10, p. 1143, 1975.
3.
A. E. Reisenauer et al., Battelle-Pacific Northwest Laboratories, TRUST:
A Computer Program for Variably Saturated Flow In Multidimensional, j
Deformable Media, NUREG/CR-2360 (PNL-3975), Nuclear Regulatory Commission, Washington, D.C., January 1982.
n l
4.
R. E. Williams, A Guide to the Prevention of Ground-water Contamination by Uranium Mill Wastes:
Geotechnical Engineerina, Colorado State University, Fort Collins, Colorado, 1982.
5.
R. W. Nelson et al., Battelle-Pacific Northwest Laboratory, Model Assessment of Alternatives for Redacina Seepage from Buried Uranium Mill Tailinas at the Morton Ranch Site in Central Wyomina, NUREG/CR-1495 (PNL-3378), Nuclear Regulatory Commission, Washington, D.C., June 1980.
6.
G. T. Yeh and D. S. Ward, FEMWATER:
A Finite-Element Model of Water Flow Through Saturated-Unsaturated Porous Media, ORNL-5567, Oak Ridge National Laboratory, Oak Ridge, Tennessee, October 1980.
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7.
C. A. Oster, Pacific Northwest Laboratories, Review of Ground-Water Flow and Transport Models in the Unsaturated Zone, NUREG/CR-2917 (PNL-4427),
Nuclear Regulatory Commission, Washington, D.C., 1982.
4 f
8.
R. A. Freeze and J. A. Cherry, Groundwater, Prentice-Hall, Inc.,
i Englewood Cliffs, New Jersey, 1979.
9.
E. Landa, I olation of Uranium Mill Tailinas and Their Component Radionuclides from the Biosphere - Some Earth Science Prespective, U.S.
l Geological Survey Circular 814, Washington, D.C., 1980.
M 10.
G. W. Gee et al., " Ground-Water Leaching of Neutralized and Untreated
/s Acid-Leached Uranium Mill Tailings," in Uranium Mill Tailinas Manaaement, Proceedinas of the Fourth Symposium on Uranium Mill Tailinas Manaaement, Colorado State University, Fort Gollins, Colorado, pp. 457-472, October 26-27, 1981.
11.
D. K. Nordstrom et al., "A Comparison of Computerized Chemical Models for Equilibrium Calculations In Aqueous Systems," in E. A. Jenne, Ed.,
Chemical Modelina In Aqueous Systems-Speciation, Sorption, Solubility, and Kinetics, ACS Symposium Series 93, American Chemical Society, Washington, D.C.', 1979.
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i j l
12.
E. A. Jenne, Geochemical Modeling: A Review, Waste / Rock Interactions m ;l Technology Program, PNL-3574, Pacific Northwest Laboratory, Richland,
>1 Washington, June 1981.
13.
J. A. Ball et al., WATEQ3 - A Geochemical Model with Uranium Added,
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U.S. Geological Survey Open-File Report 81-83, Menlo Park, California,1981.
4 14.
T. J. Wolery, " Calculation of Chemical Equilibrium Between Aqueous i
Solutions and Minerals:
The EQ3/6 Software Package," UCRL-52658, Lawrence Livermore Laboratory, Livermore, California,1979.
15.
D. L. Parkhurst et al., "PHREEQUE - A Computer Program for Geochemical Calculations," USG/WRI-80-96, U.S. Geological Survey, Reston, Virginia, 1980.
16.
J. R. Morrey, "EQUILIB - A Computer Program to Predict Ccmplex Aqueous Equilibria from 0 to 300*C," BN-SA-1297, Battelle-Northwest, Richland, Washington, 1981.
j I
17.
D. Langmuir, " Uranium Solution-Mineral Equilibria,at Low Temperatures with Applications to Sedimentary Ore Deposits," Geochimica et Cosmochimica Acta, Vol. 42, pp. 547-569, 1978.
i 18.
S. R. Peterson et al., Pacific Northwest Laboratories, The Lona Term l
t Stability of Earthen Materials in Contact with Acidic Tailinas Solutions, NUREG/CR-2946 (PNL-4463), Nuclear Regulatory Commission, Washington, D.C.,
1982.
19.
A. R. Felsy and E. A. Jenne, MINTE0:
A Computer Procram for Calculatina y
Acueous Geochemical Equilibria, EPA-68-03-3089, U.S. Environmental Protection Agency, Washington, D.C., 1982.
i 20.
S. R. Peterson and K. M. Krupka, " Contact of Clay Liner Materials with
)r[Q Acidic Tailings Solutions II. Geochemical Modeling," in Uranium Mill Tail-
/
inas Manaaement, Proceedinas of the Fourth Symposium on Uranium Mill Tailinas Manaaement, Colorado State University, Fort Collins, Colorado, pp. 609-626, October 26-27, 1981'.
21.
J. J. Fried, Groundwater Pollution - Theory. Methodoloay. Modellina, and Practical Rules, Elsevier Scientific Publishing Company. New York, New York, 1975.
22.
International Association for Hydraulic Research (IAHR), Fundamentals of a
Transport Phenomena In Porous Media, Elsevier Publishing Company, New York, New York, 1972.
{
23.
R. W. Nelson, " Evaluating the Environmental Consequences of Groundwater Contamination, 1.
An Overview of, Contaminant Arrival Distributions as t
Genera) Evaluation Requirements," Water Resources Research, Vol. 14, No. 3, pp. 409-415, June 1978.
N-v, 16
--e m.e n.
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m
- - -,wv.
,..y er-%,m,-a.m.--
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--y,w.,.---.p
-y-&se,,.-
,p-,-
-g
,f.,y,, - ~me.p +
y, rm..c
24.
R. W. Nelson, " Evaluating the Environmental Consequences of Groundwater Contamination, 2.
Obtaining Location / Arrival Time and Location / Outflow Quantity Distributions for Steady Flow Systems," Water Resources Research, Vol. 14, No. 3, pp. 416-428, June 1978.
25.
R. W. Nelson, " Evaluating the Environmental Consequences of Groundwater Contamination, 3.
Obtaining Contaminant Arrival Distributions for Steady Flow in Heterogeneous Systems," Water Resources Research, Vol. 14, No. 3, pp. 429-440, June 1978.
26.
R. W. Nelson, " Evaluating the Environmental Consequences of Groundwater g
Contamination, 4.
Obtaining and Utilizing Contaminant Arrival Distribu-tions in Transient Flow Systems," Water Resources Research, Vol. 14, No. 3, pp. 441-450, June 1978.
's 27.
G. T. Yeh and D. S. Ward, FEMWASTE:
A Finite-Element Model of Waste Transport Through Porous Media, ORNL-5601, Oak Ridge National Laboratory, Oak Ridge, Tennessee, April 1981, 28.
J. P. Delhomme, " Kriging in the Hydrosciences," Advances in Water Resources, Vol. 1, No. 5, pp. 251-266, 1978.
29.
S. S. Papadopulos and I. J. Winograd, Storage of Low-Level Radioactive i
Wastes in the Ground:
Hydrogeologic and Hydrochemical Factors, EPA-520/
3-74-009, U.S. Environmental Protection Agency, Washington, D.C., 1974.
I" 5/30.
P. A. Domenico, Concepts and Models In Groundwater Hydrology, McGraw-Hill
\\
Book Co., New York, New York, 1972.
1 o
17
~
_.a BIBLIOGRAPHY 7
Aggelides, S., and Young, E. G., "The Dependence of the Parameters in tha Green and Ampt Infiltration Equation on the Initial Water Content in Draining and i
Wetting States," Water Resources Research, Vol. 14, No. 5, pp. 857-862, October
. r.-
1978.
l l
Bear, J., " Hydrodynamic Dispersion " Dynamics of Fluids in Porous Media, American Elsevier Publishing Co., Inc., New York, New York, Chapter 10, pp. 579-660, 1972.
Dagan, G., "The Generalization of Darcy's Law for Nonuniform Flows," Water Resources Research, Vol. 15, No. 1, pp. 1-7, February 1979.
g l
Gee, G. W., et al., Battelle-Pacific Northwest Laboratory, " Interaction of Uranium Mill Tailings Leachate with Soils and Clay Liners," NUREG/CR-1494, Nuclear Regulatory Commission, Washington, D.C., June 1980.
Haverkamp, R., and Vauclin, M., "A Note on Estimating Finite Difference Interblock Hydraulic Conductivity Values for Transient Unsaturated Flow Problems," Water Resources Research, Vol.15, No.1, pp.181-187, February 1979.
McWhorter, D. B., and Nelson, J. D., " Unsaturated Flow Beneath Tailings Impoundments," Journal of the Geotechnical Enaineerina Division,14999, GT11, pp. 1317-1334, November 1979.
Narasimhan, T. N.
Neuman, S. P., and Witherspoon, P. A., " Finite Element
$tp M
Methods for Subsurface Hydrology using a Mixed Explicit-Implicit Scheme,"
Water Resources Research, Vol.14', No. 5, pp. 863-877, October 1978.
Narasimhan, T. N., and Witherspoon, P.
A., "An Integrated Finite Difference Method for Analyzing Fluid Flow in Porous Media," Water Resources Research, Vol. 12, No. 1, pp. 57-64, February 1976.
Harasimhan, T. N., and Witherspoon, P. A., " Numerical Model for Saturated-Unsaturated Flow in Deformable Porous Media, 3.
Applications," Water Resources j
l Research, Vol. 14, No. 6, pp. 1017-1034, December 1978.
Nelson, R. W., et al., Pacific Northwest' Laboratory, "Model Evaluation of Seepage from Uranium Tailings Disposal Above and Below the Water Table,"
NUREG/CR-3078 (PNL-4461), Nuclear Regulatory Commission, Washington, D.C.,
March 1983.
j Neuman, S.
P., " Wetting Front Pressure Head in the Infiltration Model of Green and Ampt," Waten Resources Research, Vol.12, No. 3, pp. 564-566, June 1976.
l Relyea, J. F., and Serne, J. R., Controlled Sample Program Publication Number 2:
Interlaboratory Comparison of Batch Kd values, Waste Isolation Safety Assessment Program, PNL-2872, Pacific Northwest Laboratory, Richland, Washington, June 1979.
3 J
~
~
Relyea, J.
F., et al., Methods for Determining Radionuclide-Retardation Factors:
Status Reoort, PNL-3349, Pacific Northwest Laboratory, Richland, Washington, April 1980.
Serne, R. J., et al., Pacific Northwest Laboratory, " Laboratory Measurements of Contaminant Attenuation of Uranium Mill Tailings Leachates by Sediments and Clay Liners," NUREG/CR-3124 (PNL-4605), Nuclear Regulatory Commission, Washington, D.C., April 1983.
U.S. Nuclear Regulatory Commission, " Final Environmental Statement Related to the Operation of Gas Hills Uranium Project," NUREG-0702, Washington, D.C.,
July 1980.
U.S. Nuclear Regulatory Commission, " Final Environmental Statement Related to '
Operation of Split Rock Uranium Mill, Western Nuclear, Inc.," NUREG-0639, Washington, D.C., February 1980.
U.S. Nuclear Regulatory Commission, " Final Generic Environmental Impact State-ment on Uranium Milling," NUREG-0706, Vols. I-III, Washington, D.C., September 1980.
Uziemblo, N. H., et al., " Contact of Cla~y Liner Materials'with Acidic Tailings Solutions - I.
Mineral Characterization," Uranium Mill Tailings Management, Proceedings of the Fourth Symposium on Uranium Mill Tailings Management, Colorado State University, Fort Collins, Colorado, pp. 597-608, 1981.
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3 DRAFT VALUE/ IMPACT STATEMENT 1.
PROPOSED ACTION 1.1 Description The proposed action is to provide guidance on selection and documentation of models used for contaminant transport analysis in ground-water systems asso-ciated with uranium mill waste disposal facilities.
This guidance provides information to the applicant when making numerical predictions of ground-water transport of radioactive and nonradioactive contaminants at tailings disposal sites.
Specifically, the guidance will provide recommendations on (1) selec-tion of analytical methods thht include numerical techniques that should be used to predict ground-water transport of radionuclides and nonradioactive materials, (2) the documentation of assumptions inherent in the use of these methods that may limit their applicability, (3) the documentation of sprecific computer models that are used to calculate ground-water transport, and (4) presentation of expected input data and model results.
3 EU
- 1. 2 Need for Proposed Action As discussed in the October 3, 1980, Federal Register Notice (45 FR 65521),
ground-water protection was a principal issue addressed in the public comments to NUREG-0511, " Draft Generic Environmental Impact Statement on Uranium Mill-ing." Further, ground-water protection is mandated by the Uranium Mill Tail-ings Radiation Control Act of 1978.
Paragraph 40.32(e) of 10 CFR Part 40 requires an applicant for a license to provide'information and analysis that the activity to be conducted will not significantly affect the quality of the
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environment.
Guidance is specifically needed to provide an applicant and the general public with information on selection and documentation of methods, data, assumptio'ns, and models that may be used for predicting ground-water transport of radioactive and nonradioactive contaminants at tailings disposal sites.
o 20
1.3 Value/ Impact of Proposed Action i
1.3.1 NRC The proposed action will provide applicants and staff with acceptable guidance on evaluating various methods for evaluating ground-water systems at uranium tailings disposal sites, which will save NRC staff resources from reviewing inadequate submittals.
Further, the value to NRC is the codifica-tion of established ground-water transport modeling criteria that should reduce public inquiries as to acceptable procedures.
This guidance will reduce ambiguities in documentation and submittal of methodology, results, and verifi-cation studies.
The established procedures will simplify licensing activities by resolving uncertainties associated with the application of various methods.
The impact on NRC staff will be the expenditure of manpower on the development of acceptable procedures based on sound technical, principles.
Completion of the proposed action is anticipated to require a 1.0 staff year effort.
Addf-tional impact will be routine office expenses and printing and distribution costs of the draft regulatory guide for public comment.
- 1. 3. 2 Other Government Agencies The value to other government agencies, including State and local govern-ments, will be reflected in their comments on the draft regulatory guide as it relates to their programs. The principal impact will be on applicant agencies (e.g., TVA) similar to " Industry" as discussed in Section 1.3.3.
Other Federal, State, and local agencies may be affected during the public comment period upon issuance of the guidance.
The greatest value will be to the various Agreement States in providing a useful standard by which they can develop their own particular criteria..
I
-1.3.3 Industry The industry will benefit from this guidance in that they will be aware of the acceptable selection and documentation criteria for models that predict ground-water transport of radioactive and nonradioactive contaminants asso-ciated with uranius' mill tailings' disposal sites.
Specifically, the guidance will provide for the submittal of information to describe data sources.and t
analytical procedures.
No additional impact beyond present licensing-incurred costs is anticipated.
21
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1.3.4 Workers No direct impact on workers is foreseen.
1.3.5 Public j
The direct costs t'o the public will be through government agencies who are applicants or those who will review and comment on the guidance.
The public will benefit from the assurance that the ground-water systems asso-ciated with uranium recovery facilities are well defined and operations are maintained such that e.quifers are protected from seepage of radioactive and nonradioactive contaminants.
The public will be informed as to what the NRC staff considers acceptable guidance on evaluating ground-water systems at uranium recovery sites.
1.4 Decision on Proposed Action 1
1..e proposed action should be accomplished on a priority basis because of the aforementioned benefits and public interest.
- h 2.
TECHNICAL APPROACH
'p Not applicable.
3.
PROCEDURAL APPROACH 3.1 Procedural Alternatives The alternative procedural methods of accoinplishing the proposed action are:
ANSI standard, endorsed by a regulatory guide NUREG Branch technical position Regulatory guide l
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STATUTORY CONSIDERATIONS S
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4.1 NRC Authority
'..T Authority for this regulatory guide is derived directly from the Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978, the Atomic Energy Act of 1954, as amended, and the Energy Reorganization Act of 1974, as amended, and is implemented through the Commission's regulations, in particular, 10 CFR Part 40,
" Domestic Licensing of Source Material."
4.2 Need for NEPA Assessment The proposed action does not require the preparation of an environmental impact statement since it does not fulfill the requirements. of S 51.5 of 10 CFR Part 51.
5.
RELATIONSHIP TO OTHER EXISTING'OR PROPOSED REGULATIONS OR POLICIES The proposed action is part,of an integrated program to develop guidance in the area of ground-water and surface-water siting, design, and analysis criteria for uranium recovery operations.
No conflicts exist with similarly proposed guidance in the areas of ground-water investigati.ons and monitoring.
Existing regulatory guides that apply to ground-water transport of radioactive and nonradioactive materials also do not appear to be in conflict.
The following regulatory guides are related:
Regulatory Guide 3.5, " Standard Format and Contenti of License a.
Applications for Uranium Mills" b.
. Regulatory Guide 3.8, " Preparation of Environmental Reports for Uranium Mills" c.
Regulatory Guide 4.14. " Radiological Effluent and Environ-mental Monitoring at Uranium Mills."
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3.2 Discussion of Procedural Alternatives 1
j a.
Endorsed ANSI Standard i
The development of an ANSI standard to be followed by an endorsing regula-i tory guide would allow a working partnership between industry and the NRC.
However, it would require a one-to two-year delay.
Further, the standard f
would have to be separately reviewed and adopted by the NRC.
b.
NUREG i
By definition, a NUREG could only provide technical information, which would be useful, but would not provide the guidance specified by the proposed action.
c.
Branch Technical Position A branch technical position is not presently being developed in-house because,of a lack of manpower resources in uranium recovery licensing.
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d.
Regulatory Guide A regulatory guide would provide wide distribution of the needed guidance.
It would also provide an established review that would include a public comment ~
review period.
The regulatory guide would use both licensing review experience and NRC contractor technical reports as the technical basis and outline a formalized acceptance criteria that would eliminate any procedural uncertainty in predicting ground-water contaminant transport associated with uranium tailings disposal sites.
The regulatory guide would require manpower commitments from NRC offices involved in reviewing, writi,ng, and publishing standards.
3.3 Decision on Procedural Alternatives The development and issuance of a regulatory guide for public' comment
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would best achieve the need for the proposed action.
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The proposed action will supplement these regulatory guides in providing more detailed guidance.
Subsequent changes to these existing guides may be needed to implement UMTRCA but not in the pursuance of this pro' posed action.
No backfitting requirements will result from this proposed action.
6.
SUMMARY
AND CONCLUSIONS The NRC has both the need and authority to implement the proposed action.
The technical and procedural alternatives most favored are to have the proposed action developed as a regulatory guide.
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