Waste Form and Indrift ColloidsAssociated Radionuclide Concentrations: Abstraction and Summary Rev 00, ICN 00

MDL-EBS-PA-000004

June 2003

1. PURPOSE 
The purpose of this model report is to present and describe the abstraction of the colloids process 
model for the waste form and engineered barrier system components of the total system 
performance assessment calculations to be performed with the Total System Performance 
Assessment (TSPA)-License Application (LA) model. The model describes (1) the types and 
concentrations of colloids that could be generated in the waste package from degradation of the 
waste forms and the corrosion of the waste package materials, (2) types and concentrations of 
colloids produced from the steel components of the repository and their potential role in 
radionuclide transport, and (3) types and concentrations of colloids present in natural waters in 
the vicinity of Yucca Mountain. In addition, attachment/detachment characteristics and 
mechanisms of colloids anticipated in the repository are addressed and discussed. The 
abstraction of the process model is intended to capture the most important characteristics of 
radionuclide-colloid behavior for use in predicting the potential impact of colloid-facilitated 
radionuclide transport on repository performance. 
Experimental data developed from ongoing research (BSC 2002 [DIRS 161534]; BSC 2002 
[DIRS 161535]; BSC 2002 [DIRS 158197]), primarily by Argonne National Laboratory, Los 
Alamos National Laboratory, and at the University of Nevada at Las Vegas and information 
from other pertinent studies reported in the open literature are used as the basis for the selection 
of input parameters used in the process models. The application of new testing data to the 
development of the model parameters and model abstractions for TSPA-LA are discussed in 
Section 4, Inputs, and Section 6.0, Model Discussion. 
1.1 APPLICABILITY OF MODEL TO REPOSITORY 
It is anticipated that unsaturated conditions will prevail within the engineered barrier system 
during the 10,000-year regulatory compliance period. The TSPA-LA model examines two cases: 
(1) condensation of water vapor (pure water) onto engineered barrier system components with 
development of thin films and (2) seepage influx to the engineered barrier system with no 
accumulation of seepage water within the WP and water films up to about 0.25 cm thick, for 
three seepage water compositions: J-13 and two pore water compositions (BSC 2003 [DIRS 
163919]. 
The colloid model abstraction is used in TSPA-LA to estimate the stability and concentration of 
colloids, as well as concentrations of radionuclides associated with the colloids, based on 
in-package and in-drift fluid chemistry and in-package dissolved radionuclide concentrations. 
As such, the colloid parameters are estimated based on fluid chemistry only, i.e., regardless of 
fluid quantity and spatial distribution. Feeds for in-package ionic strength and pH are received 
from In-Package Chemistry Abstraction (BSC 2003 [DIRS 163919]) and feeds for in-drift ionic 
strength and pH are received from the engineered barrier system physical and chemical 
environment (BSC 2002 [DIRS 160315], analysis described in Section 1.2.2). Feeds for 
dissolved radionuclide concentrations are developed in Dissolved Concentrations of Radioactive 
Elements (BSC 2003 [DIRS 163152]). 
The colloid model abstraction relies on laboratory tests of waste form degradation (performed at 
Argonne National Laboratory, mentioned above) that are specific to Yucca Mountain conditions

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 13 June 2003 
and objectives. These tests can be broadly described as immersion tests in which the sample is 
completely submerged in water, drip tests in which measured quantities of water are injected into 
the vessel onto the waste form sample, and humid-condition tests in which samples are degraded 
under humid conditions with no liquid water contacting the sample. The test data used directly 
or indirectly in the abstraction come from all test types but primarily the first two (immersion 
and drip). Generally, at the end of the tests, colloids were removed from the fluid and both 
colloids and fluid analyzed. Measured stabilities and concentrations of colloids were related to 
fluid compositions. The abstraction also relies on fundamental properties of colloids taken from 
the literature. Colloid properties are determined by testing (in water) and by calculation and 
modeling. Because in-package chemistry calculations, including fluid chemistry, are performed 
for scenarios in which water layers or films are modeled, and since colloid behavior is 
determined by fluid properties, regardless of fluid quantity or shape, the methodology employed 
in the colloid model abstraction is deemed appropriate for its purpose. 
Although colloid transport under saturated conditions is not postulated for the regulatory period 
of concern, limited movement of colloids within thin water films could occur. The extent and 
longevity of these thin films depend upon the specific hydrologic conditions within the waste 
package and various locations in the surrounding engineered barrier system environment at a 
particular time, as does the degree of continuity of the films. Consequently, transport of colloids 
and associated radionuclides from the waste package to the invert may be impeded to some 
degree. Transport in the engineered barrier system is described in EBS Radionuclide Transport 
Abstraction (BSC 2003 [DIRS 163935]). 
1.2 MODEL LIMITATIONS AND RANGE OF APPLICATION 
For the purposes of this report, colloidal systems are defined as those in which the component 
phases are dispersed in an aqueous medium ranging in size from approximately 1 to 10 nm to 
1 m. The environmental behavior of colloids has been studied extensively over the past few 
decades but, due largely to their small size and unique surface-dominated chemical and physical 
characteristics, colloids have proven difficult to study. Additionally, testing on the degradation 
of high-level radioactive waste and the formation of colloids from these materials has generally 
been limited to government-sponsored research. The approach taken in this analysis and 
modeling effort was to bound the probable behavior of colloid-associated radionuclides, using 
accessible data from these government-sponsored projects to the fullest extent possible. The 
absence of certain data can be mitigated as well by comparing these bounds with other relevant 
laboratory and field studies and with other sites in which environmental conditions are analogous 
in critical respects to those anticipated in the repository. These approaches have been used to the 
fullest extent possible to reduce the uncertainties associated with predictions of colloidassociated 
radionuclide concentrations, stability, and subsequent transport characteristics. 
Colloid facilitated transport may play a significant role in radionuclide transport, and recent 
studies of plutonium (Pu) migration in natural (non-karst) hydrologic systems suggest relatively 
rapid transport times for Pu in association with colloids (Kersting et al. 1999 [DIRS 103282]; 
Penrose et al. 1990 [DIRS 100811]). However, in some cases, other researchers have concluded 
that other mechanisms may have been responsible for the transport of this radionuclide. For 
example, Marty et al. (1997 [DIRS 161670]) concluded that transport through rapid flow 
transport paths (i.e., uncapped sampling wells) might have led to the accelerated movement of Pu

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 14 June 2003 
at Mortandad Canyon at Los Alamos National Laboratory (Penrose et al. 1990 [DIRS 100811]. 
Consequently, it is apparent that a complex assemblage of processes would play a role in the 
potential transport of radionuclides from waste package containers emplaced within the 
repository through the engineered barrier system and the underlying natural barrier system 
(unsaturated and saturated zones). The models described in this report focus first on the 
processes and physical/hydrological factors that might lead to the formation of colloid-size waste 
products from the degradation of the high-level nuclear wastes materials and secondly on their 
subsequent stability within the waste package and surrounding engineered barrier system 
environment. Other analysis and models developed for the TSPA-LA address the processes and 
mechanisms responsible for the stability and transport/retardation of radionuclides associated 
with colloids released from the engineered barrier system to the underlying unsaturated zone 
(BSC 2002 [DIRS 160819]) and saturated zone environments (BSC 2001 [DIRS 156308]). 
Colloid source term is defined here as the total of those radionuclides associated in some manner 
with colloids that (1) are mobilized at the surface of the waste form, (2) are transported within 
the waste package to the waste package wall, (3) leave the waste package at a breach or breaches 
in the waste package wall, and (4) enter the drift. 
The model describing colloid formation through waste form degradation and their subsequent 
stability within the drift is valid only over the range of chemical and hydrological conditions 
anticipated within the waste package and drift during the postclosure regulatory compliance 
period. Discussion on the valid range of application for the various process models is included 
in Section 7, Validation. 
1.3 SCOPE OF MODEL DOCUMENTATION 
This model report was developed, in part, by building upon previously developed concepts on 
colloid formation and stability within the waste form (CRWMS M&O 2001 [DIRS 153933]) and 
in-drift (CRWMS M&O 2000 [DIRS 129280]) environments. 
The modeling and abstraction activities reported in this document are specified in and are carried 
out in accordance with the work scope described in the technical work plan for the Waste Form 
Department (BSC 2002 [DIRS 160779]). Additionally, implementation of this model will rely 
on inputs from models developed from activities within the engineered barrier system model 
component (BSC 2002 [DIRS 160315], analysis described in Section 1.2.2), as well as other 
activities within the Waste Form Department (BSC 2003 [DIRS 163919], 2003 [DIRS 163152]). 
There were no deviations from the work/activities outlined in Technical Work Plan for Waste 
Form Degradation Modeling, Testing, and Analyses in Support of SR and LA (BSC 2002 
[DIRS 160779]). 
1.4 MODEL REPORT OVERVIEW 
Section 2.0 lists the procedures, technical work plan, and requirements under which this report 
was prepared. Section 3.0 discusses the software used in report preparation. 
A summary of parameters used in the process models developed and used in this abstraction is 
listed in Section 4.1, Data and Parameters, Table 1. Section 4.0 describes the development of 
inputs for the colloid model abstraction and lists the information used in Table 1 (direct input

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 15 June 2003 
Q data) and Table 2 (other input, including corroborative non-Q data). The Yucca Mountain 
Review Plan (NRC 2002 [DIRS 158449]) acceptance criteria and the codes and standards that 
apply to this report are listed as well. 
Section 5.0 presents the assumptions used in the colloid abstraction with their rationale, 
confirmation status, and the report sections in which the assumptions are used. The assumptions 
are used primarily in two situations. In those cases where data are inadequate to support a 
particular concept or model technique (e.g., sorptive properties of protactinium), a bounding 
assumption is generally used. Similarly, where a process would add complexity to the model 
without adding a significant and defensible component to the output (e.g., gravitational settling), 
it was left out of the model and a bounding assumption was established. An assumption 
regarding colloid-microbe interactions (Section 5, Assumption 5.9) is based on a review of 
literature and on professional judgment; a review of the issue and description of pertinent data is 
presented in Section 6.3.4. 
Conceptual models and background information on colloid formation and behavior (including 
potential stability and their potential role in radionuclide transport) are presented in Section 6. A 
description of the model and its objectives are presented in Section 6.1. Pertinent features, 
events, and processes (FEPs) evaluated for their pertinence to this analysis are addressed in 
Section 6.2. 
Section 6.3 presents the base-case colloid model elements in several subsections. The 
background information and rationale are provided for the approaches used as well as for 
elements considered but not incorporated into the model (e.g., colloids from commercial spent 
nuclear fuel [SNF] and U.S. Department of Energy [DOE] SNF). Colloid formation, stability, 
and concentration; radionuclide attachment to colloids; and microbial interactions are discussed 
within each of these subsections. Section 6.4 describes alternative models that were considered 
during the development of the colloid model and the rationale for not using them. 
Section 6.5 presents the abstraction of the colloid model elements and the methodology and logic 
for implementing the abstraction in the TSPA-LA model calculations. The section begins with a 
summary description of the abstraction and a schematic overview figure (Figure 17). Section 
6.5.1 presents the in-package abstraction in some detail, with figures; Section 6.5.2 similarly 
provides the in-drift abstraction. Section 6.5.3 presents an overview of the disposition of 
colloids and associated radionuclides downstream from the engineered barrier system in the 
unsaturated zone and saturated zone. 
Sections 6.6, 6.7, and 6.8 present the model results, description and analyses of the barrier 
capability, and an evaluation of the alternative models. 
Section 7.0 validates the colloids process model. It also describes the waste form, corrosion 
products, and groundwater colloid parameters (used as surrogates for seepage water colloids in 
this analysis); radionuclide attachment characteristics; model uncertainty; and processes not 
incorporated into the model abstraction.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
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Section 8.0 provides a summary of analysis, describes the developed output parameters and 
uncertainties, and presents conclusions drawn from the model results. Section 9.0 lists 
references cited, codes, standards, regulations, procedures, and source data. 
2. QUALITY ASSURANCE 
Development of this analysis and model report and the supporting analyses have been 
determined to be subject to the Yucca Mountain Projects quality assurance program (BSC 2002 
[DIRS 160779], Section 2.1.4.4, Work Package AWFM01). Quality Assurance Requirements 
and Description (DOE 2003) applies to the development of this Model Report. Approved 
quality assurance procedures identified in the technical work plan (BSC 2002 [DIRS 160779], 
Section 4, Implementing Procedures) have been used to conduct and document the activities 
described in this model report. The technical work plan also identifies the methods used to 
control the electronic management of data (BSC 2002 [DIRS 160779], Section 8)there were 
no deviations from these methods. 
The report contributes to the analysis and modeling data used to support performance assessment 
by developing and providing source terms for waste form colloids, corrosion product colloids, 
and natural groundwater colloids for the TSPA-LA model; the conclusions do not directly impact 
engineered features or engineered and natural barriers important to waste isolation, as defined in 
AP-2.22Q, Classification Criteria and Maintenance of the Monitored Geologic Repository 
Q-List. 
3. USE OF SOFTWARE 
No computer software was used for calculations and/or modeling in support of this analysis. No 
codes or routines were developed. 
Reference to parameters used in calculations by the TSPA-LA model is made in this model 
report. The parameters are provided for use by the TSPA-LA model, but no total system 
performance assessment model calculations were performed for this model report. The logic 
presented in this report is intended for implementation in the TSPA-LA model, but no computer 
runs with GoldSim (BSC 2003 [DIRS 161572]) were executed for this report. 
Graphs and figures were prepared with Microsoft Excel 2000, Microsoft PowerPoint 2000, and 
Adobe Illustrator 8.0.1. Excel was used for tabular presentation of data only and to execute 
simple mathematical operations (addition, subtraction, and multiplication) in the evaluation of 
these data; no built-in functions or mathematical operations were employed. PowerPoint was 
used for presentation (i.e., figures) of data extracted from Excel spreadsheets. These off-theshelf 
software programs are exempt per AP-SI.1Q, Software Management, Sections 2.1.1 and 
2.1.2. 
4. INPUTS 
Technical product inputs and sources are direct inputs (Table 1). Corroborating/supporting data 
and information are used to develop the model (Table 2) as stipulated by AP-SIII.10Q, Models.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 17 June 2003 
4.1 DATA AND PARAMETERS 
Direct technical inputs have been taken from data inputs provided by Argonne National 
Laboratory and Los Alamos National Laboratory (Table 1, direct Q-data inputs) that address the 
types of colloids formed from waste form degradation, steel corrosion degradation products, and 
natural seepage water colloids that might potentially come in contact with waste forms and the 
surrounding engineered barrier system. Also included in the input tables are sources of data 
used for the development of sorption partition coefficients (Kd values) that are used to model 
radionuclide attachment to colloids. During the colloids source term model implementation by 
the TSPA-LA model, pertinent output parameters from the in-package (BSC 2003 [DIRS 
163919]) and in-drift chemistry calculations (BSC 2002 [DIRS 160315] analysis described in 
Section 1.2.2) are used as direct input during each model iteration (i.e., these inputs are sampled 
stochastically during each modeled time step). For purposes of description, the parameters 
developed in this analysis have been broadly grouped as follows: 
 Waste form colloid parameters (modeled colloid: smectite; experimental work at 
Argonne National Laboratory has shown that the colloids formed from defense 
high-level waste glass are smectite). 
 Corrosion product colloid parameters (modeled colloid: iron oxyhydroxide/goethite) 
 Seepage water (groundwater) colloid parameters (modeled colloid: smectite) 
 Radionuclide sorption partition coefficients (Kd values) 
These parameter groups are described in the next section, and the parameters are listed and 
described in Table 1. The parameters listed in Table 1 are based technically on findings from 
applicable analytical, laboratory, and field research, including investigations specific to the 
Yucca Mountain region and the Yucca Mountain Project (YMP). More detailed discussion on 
the technical bases for the development of these parameters may be found in Section 5, 
Assumptions, and Section 6, Model Discussion. 
Uncertainty associated with the model analysis, including development of parameter values and 
their implementation in the TSPA-LA model, is discussed in Section 6.6.2, Uncertainty 
Associated with the Model Analysis. Parameter uncertainties are addressed by providing ranges, 
probability distributions, and bounding assumptions as appropriate for each given parameter. 
Many of the parameters are derived from data directly relevant to colloid formation, stability, 
and capacity to associate with radionuclides. However, many of these data were not collected 
from the YMP site and may not fully represent the physical and chemical conditions of the 
repository. Departure from anticipated repository conditions is addressed by acknowledging 
uncertainties in the parameters and providing a means to incorporate these uncertainties into the 
total system performance assessment calculations. These uncertainties are addressed by 
providing ranges, probability distributions, and bounding assumptions as appropriate for each 
given parameter or process.

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Table 1. Summary of Direct Input Data Used in Model Parameter Development 
Data Tracking Number (DTN) or 
Report Data/Parameter Description Unitsa Locations in 
Model Report 
Waste Form Colloids 
LL000905312241.018 [DIRS 152621] 
LL991109751021.094 [DIRS 142910] 
Plutonium concentration 
associated with DHLWG colloids 
from ANL testssee Figures 3 
and 8 
mol/L Section 6.3.1 
LA0003NL831352.002 [DIRS 148526], 
LA0005NL831352.001 [DIRS 149623] 
EPA 1999 [DIRS 147475]; Honeyman 
and Rainville 2002 [DIRS 161657]; 
Stenhouse 1995 [DIRS 147477]; Lu et al. 
1998 [DIRS 100946]; Lu et al. 2000 
[DIRS 154422] 
Kd values for radionuclides on 
rocks, minerals, and colloids; 
modeling results for partitioning 
of radionuclides between colloids 
and stationary phases 
mL/g Section 
6.3.3.1, 
Table 6, 7, 8. 9 
Corrosion-Generated [iron oxyhydroxide] Colloids 
MO0212UCC034JC.002 [DIRS 161457] Concentration of iron 
oxyhydroxide colloids resulting 
from the corrosion of steel 
corrosion products in waste 
packages 
mg/L Section 6.3.1.3 
LA0003NL831352.002 [DIRS 148526], 
LA0005NL831352.001 [DIRS 149623] 
EPA 1999 [DIRS 147475]; Honeyman & 
Ranville 2002 [DIRS 161657]; Stenhouse 
1995 [DIRS 147477] 
Kd values for radionuclides on 
rocks, minerals, and colloids; 
modeling results for partitioning 
of radionuclides between colloids 
and stationary phases 
mL/g Section 
6.3.3.1, 
Table 6, 7, 8. 9 
Groundwater Colloids 
LA0002SK831352.001 [DIRS 149232]; 
LA0002SK831352.002 [DIRS 149194], 
LA9910SK831341.005 [DIRS 144991] 
LA0211SK831352.002 [DIRS 161581], 
LA0211SK831352.004 [DIRS 161458], 
LA0211SK831352.001 [DIRS 161580] 
LA0211SK831352.003 [DIRS 161582] 
Colloid particle size distributions 
and concentration values for 
groundwater samples in the 
Yucca Mountain vicinity 
nm 
(size); 
pt/ml 
(conc.) 
Section 6.3.2.5 
and 
Attachment I 
Lide 1995 [DIRS 101876] Particle density values for silicate 
mineralsused to estimate 
general particle density value for 
groundwater colloids. 
g/cm3 Attachment I 
LA0003NL831352.002 [DIRS 148526], 
LA0005NL831352.001 [DIRS 149623] 
Kd values for radionuclides on 
rocks, minerals, and colloids 
mL/g Section 
6.3.3.1, 
Table 6 
NOTES: a mol/L Pu = moles per liter of dispersion, not molarity in the strict sense. 
ANL = Argonne National Laboratory; N/A = not applicable. 
Parameters Developed in this Model Analysis/Abstraction: 
Waste Form Colloid ParametersThe parameters listed under the category Waste 
Form Colloids in Table 1 relate primarily to the expected colloid composition resulting 
from the degradation of defense high-level waste glass, commercial SNF, and DOE SNF, 
determination of colloid stability and estimated colloid mass concentrations, and estimated

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MDL-EBS-PA-000004 REV 00 19 June 2003 
concentrations of radionuclides embedded within these colloids. Parameters used to 
describe reversible radionuclide attachment (sorption) include sorption partition 
coefficients (Kd values), colloid specific surface areas, and effective Kd values derived 
from surface complexation calculations. Ionic strength and pH are parameters taken 
directly from In-Package Chemistry Abstraction (BSC 2003 [DIRS 163919]), Dissolved 
Concentrations of Radioactive Elements (BSC 2003 [DIRS 163152]), and near-field 
chemical environment analyses (BSC 2002 [DIRS 160315], analysis described in Section 
1.2.2). In addition there are functions and intermediate parameters listed in Table 16 
resulting from the model abstraction as implemented in the total system performance 
assessment calculations. 
Waste form parameter ranges and distributions were established using the available 
knowledge of processes and principles, utilizing necessary conceptual simplifications, and 
consideration of measurement error. Parameter ranges and/or distributions are listed in 
Table 16. 
Corrosion-Generated (Iron Oxyhydroxide) Colloid ParametersThe colloid 
parameters listed under Corrosion-generated (iron oxyhydroxide) Colloids in Table 1 are 
related to estimates of corrosion product colloid mass concentrations in the waste package 
and the invert and determination of their stability. Parameters used to describe reversible 
radionuclide attachment (sorption) include sorption partition coefficients (Kd values), 
colloid specific surface areas, and effective Kd values derived from surface complexation 
calculations. Ionic strength, pH, and dissolved radionuclide concentrations are input 
parameters taken directly from data resulting from In-Package Chemistry Abstraction 
(BSC 2003 [DIRS 163919]) and Dissolved Concentrations of Radioactive Elements (BSC 
2003 [DIRS 163152]). In addition, listed in Table 16 are functions and intermediate 
parameters resulting from model abstraction for total system performance assessment 
calculations. 
Parameter ranges and distributions were formulated using the available knowledge of 
processes and principles associated with iron oxyhydroxide colloids, utilizing necessary 
conceptual simplifications, and consideration of measurement error. Parameter ranges 
and/or distributions are listed in Table 16. 
Seepage Water Colloid ParametersThe colloid parameters listed under Groundwater 
Colloids in Table 1 define seepage water colloid mass concentrations entering the waste 
package and other components of the engineered barrier system. Groundwater parameter 
ranges and distributions (as appropriate) were formulated using all known available data on 
groundwater colloid concentration in wells evaluated in the vicinity of Yucca Mountain. 
Data sources are listed in Table 1 (direct input). 
Radionuclide Attachment ParametersSorption partition coefficients (Kd values) are 
used, with one exception, in the abstraction to estimate concentrations on colloids of the 
reversibly sorbed radionuclides considered in the abstraction. The ranges and distributions 
of these Kd values are given in Table 16. In the exception (reversible sorption of Pu on 
corrosion-generated colloids), surface complexation calculations were performed and/or 
reliance was placed on laboratory, field, and modeling investigations in the peer-reviewed

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 20 June 2003 
literature to derive effective Kd values, which were derived from the effective, or 
specific, surface areas (SA) of the colloids. 
Other Parameters Critical to the Implementation of this Abstraction in the TSPA-LA 
Model:
Chemical and Environmental Parameters When this colloids process model is 
implemented in the TSPA-LA model, it is fed certain chemical and environmental 
parameters from other submodels implemented in the TSPA-LA. Ionic strength and pH 
are developed in the in-package chemistry model (BSC 2003 [DIRS 163919]) and 
engineered barrier system physical and chemical environment model (BSC 2002 [DIRS 
160315]) abstractions, and dissolved radionuclide concentrations are developed in 
Dissolved Concentrations of Radioactive Elements (BSC 2003 [DIRS 163152]). In-drift 
chemical environmental parameters (e.g., seepage water pH and ionic strength) are 
provided in the engineered barrier systems physical and chemical environment model 
(BSC 2002 [DIRS 160315], analysis described in Section 1.2.2). This abstraction does 
not use these parameters directly, rather the parameters are used to implement the colloid 
subprocess models within the TSPA-LA model calculations. 
4.2 CRITERIA 
The following Yucca Mountain Review Plan, Information Only (NRC 2002 [DIRS 158449]) 
acceptance criteria as outlined in Table 5 of Technical Work Plan for Waste Form Degradation 
Modeling, Testing, and Analyses in Support of SR and LA (BSC 2002 [DIRS 160779]) apply to 
this model report: 
Degradation of Engineered Barriers: 
 AC1: System Description and Integration Are Adequatethat is, total system 
performance assessment adequately incorporates important physical phenomena, 
and couplings, and uses consistent and appropriate assumptions throughout the 
engineered barrier system abstraction process. 
 AC2: Data Are Sufficient for Model Justificationthat is, parameters used to evaluate 
the degradation of engineered barriers in the safety case are adequately justified 
(e.g., colloid concentrations formed from waste degradation and steel corrosion). 
Additionally, sufficient data have been collected to establish initial boundary 
conditions for abstraction of degradation of engineered barriers. 
 AC3: Data Uncertainty Is Characterized and Propagated through the Model 
Abstractionthat is, subprocess models use parameter values, assumed ranges, 
probability distributions, and bounding assumptions that are technically 
defensible, reasonably account for uncertainties and variabilities, and do not result 
in an under representation of the risk estimate. 
 AC4: Model Uncertainty Is Characterized and Propagated through the Model 
Abstractionthat is, alternative modeling approaches of FEPs are considered and

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MDL-EBS-PA-000004 REV 00 21 June 2003 
are consistent with available data and current scientific understanding, and the 
results and limitations are appropriately considered in the abstraction. Conceptual 
model uncertainties are defined and documented and conclusions are properly 
assessed. 
Quantity and Chemistry of Water Contacting Waste Packages and Waste Forms: 
 AC1: System Description and Integration Are Adequatethat is, the total system 
performance assessment adequately incorporates important design features, 
physical phenomena, and couplings and uses consistent and appropriate 
assumptions throughout the modeling of the quantity and chemistry of water 
contacting waste packages and waste forms. Additionally, sufficient technical 
bases and justification are provided for modeling coupled processes, including the 
waste package chemical environment, and the chemical environment for 
radionuclide release. 
4.3 CODES AND STANDARDS 
This Model Report was prepared to comply with the Yucca Mountain Review Plan, Draft for 
Comment (NRC 2002 [DIRS 158449]) and the specified subparts/sections of the U.S. Nuclear 
Regulatory Commission (NRC) high-level waste rule, 10 CFR Part 63 [DIRS 158535]. Subparts 
of this rule that are particularly applicable to data include Subpart B, Section 15 (Site 
Characterization) and Subpart E, Section 114 (Requirements for Performance Assessment). 
Subparts applicable to models are outlined in Subpart E, Sections 114 (Requirements for 
Performance Assessment) and 115 (Requirements for Multiple Barriers). The work conforms to 
the guidance provided in American Society of Testing and Materials (ASTM) Standard 
C 1174-97 [DIRS 105725] as stated in Section 3 of Technical Work Plan for Waste Form 
Degradation Modeling, Testing, and Analyses in Support of SR and LA (BSC 2002 [DIRS 
160779]). Another regulatory requirement adhered to in this analysis is the U.S. Environmental 
Protection Agency's (EPA) rule 40 CFR Part 197 [DIRS 155238] with reference to screening of 
FEPs. 
4.4 INDIRECT INPUTS TO MODEL ANALYSIS 
Corroborating/supporting data and information sources used in the model analysis are listed in 
Table 2.

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Table 2. Summary of Corroborating/Supporting Information Used in Model Parameter Development 
Reference Data/Parameter Description Units 
Locations 
in Model 
Report 
Corrosion-Generated (iron oxyhydroxide) Colloids 
Laaksoharju et al. (1995 [DIRS 
106449]); Vilks et al. (1993) [DIRS 
108261] 
Concentration of iron oxyhydroxide 
colloids observed in natural 
groundwaters. 
mg/L Section 
6.3.1.3 
Langmuir 1997 [DIRS 100051]; 
Dzombak and Morel 1990 [DIRS 
105483]; Davis and Kent 1990 [DIRS 
143280] 
Specific surface area and site 
density estimates for iron phases. 
m2/g 
and # 
sites/ 
nm2 
Section 
6.3.3.2 
Langmuir 1997 [DIRS 100051]; 
Dzombak and Morel 1990 [DIRS 
105483]; Davis and Kent [DIRS 
143280]; Jenne 1998 [DIRS 162328] 
Specific surface area (SA) for iron 
oxyhydroxide colloids 
m2/g Sections 
5.12, 6.3.3.2 
Groundwater Colloids 
LA0002SK831352.003 [DIRS 161771], 
LA0002SK831352.004 [DIRS 161579] 
Colloid particle size distributions 
and concentration values for 
groundwater samples in the Yucca 
Mountain vicinity 
nm 
(size); 
pt/ml 
(conc.) 
Section 
6.3.2.5 and 
Attachment I 
5. ASSUMPTIONS 
The assumptions used in the colloid abstraction are presented here along with their rationale, 
confirmation status, and the report sections in which the assumptions are implemented. The 
assumptions were established under one of two distinct circumstances. First, a bounding 
assumption was established when data were deemed to be inadequate to fully support a particular 
concept or model technique (see Assumptions 5.1, 5.2, 5.3, 5.5, 5.12). Additionally, an 
assumption that it is appropriate to exclude a particular process from the modeling effort was 
established if it was determined that consideration of the process (or in some cases the 
subprocesses needed to define the process) in the TSPA-LA analyses would add complexity to 
the model without significantly impacting the output (see Assumptions 5.4, 5.6, 5.7, 5.8, 5.9, 
5.10, 5.11). 
5.1 AMERICIUM BEHAVES SIMILARLY TO PLUTONIUM WITH RESPECT TO 
ATTACHMENT TO COLLOIDS 
AssumptionIt is assumed that Am behaves in a similar manner to Pu in terms of mobilization 
from waste degradation and irreversible association with (i.e., embedment within) smectite 
colloids formed from defense high-level waste glass. 
RationaleReasonable assumption based on chemical characteristics of Pu and Am. The 
binding of Am to soil components has been shown to be similar to Pu and the sorption partition 
coefficient (Kd value) of Am to freshwater sediments is similar to that of Pu (Coughtrey et al. 
1985 [DIRS 154494], see pp. 11 and 119). 
Confirmation StatusNo confirmation required; this is a bounding assumption.

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Section(s) Used InSection 6.3.1, Colloid Formation and Occurrence, and Section 6.3.3, 
Radionuclide Sorption to Colloids 
5.2 DISTRIBUTION COEFFICIENTS OF THORIUM AND PROTACTINIUM ARE 
THE SAME AS THAT OF AMERICIUM 
AssumptionThe Kd values ranges and distributions for Th and Pa are assumed to be those of 
Am primarily because of limited data on Th and Pa. 
RationaleBecause Kd values ranges and distributions for Am are the highest reported in the 
input data formulating the ranges and distributions (see Table 10, Section 6.3.3.1), this is a 
conservative bounding assumption with respect to radionuclide attachment to colloids. 
Confirmation StatusNo confirmation required; this is a bounding assumption. 
Section(s) Used InSection 6.3.3.1, Table 10. 
5.3 SORPTIVE CHARACTERISTICS OF CESIUM 
AssumptionThe Kd value ranges and distributions for Cs are assumed to be those lower than 
those of Pu, Am, Th, and Pa. Additionally, it is assumed that the adsorption and retention of Cs 
to smectite is greater than to iron oxyhydroxides. 
RationaleIn contrast to the other radionuclides modeled in this analysis (see Table 10, Section 
6.3.3.1), dissolved Cs in groundwater tends to be present in the monovalent form (Cs+). 
Additionally, unlike the other radionuclides considered in this reversible sorption analysis in this 
report (see Table 10, Section 6.3.3.1), there is strong evidence that the Kd value ranges and 
distributions for Cs adsorption and retention should be different for smectite and iron 
oxyhydroxides. This is based largely on the fact that Cs has been shown to attach very strongly 
to certain sheet silicate minerals (Brady et al. 2002 [DIRS 161649]). 
Confirmation StatusNo confirmation required; this is a bounding assumption. The 
establishment of the Kd value ranges and distributions intentionally encompass a broad range of 
Kd values, and this approach is deemed to be conservative to the TSPA-LA model analysis. 
Section(s) Used InSection 6.3.3.1, Table 10 
5.4 EFFECT OF TEMPERATURE ON WASTE FORM COLLOIDS 
AssumptionIt is assumed that waste form colloids produced at 90oC are stable at 25oC. 
RationaleThe colloid stability ratio predicts increased stability as temperature drops (Section 
6.3.2.1, Equation 2); therefore if colloids are stable at 90oC, they should be stable at 25oC. 
Confirmation StatusNo confirmation required; this is a bounding assumption. 
Section(s) Used InSection 6.3.2, Colloid Stability and Concentration

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5.5 PU AND AM EMBEDDED WITHIN DEFENSE HIGH-LEVEL WASTE GLASS 
COLLOIDS 
AssumptionIt is assumed that Pu and Am associated with defense high-level waste glass 
colloids are embedded within the colloids. 
RationaleIt was observed that Pu was associated with abundant colloids generated from the 
corrosion of defense high-level waste glass, but the mechanism of attachment was not 
determined. The irreversibility of attachment estimates or over-estimates the concentration of 
radionuclides associated with colloids. Inclusion of Am is based on assumption in Section 5.1. 
Confirmation StatusNo confirmation required; this is a bounding assumption. 
Section(s) Used InSection 6.3.1, Colloid Formation and Occurrence, and Section 6.3.3, 
Radionuclide Sorption to Colloids 
5.6 PHYSICAL FILTRATION OF COLLOIDS 
AssumptionIt is assumed that physical filtration of colloids will not occur within the waste 
package and the drift. 
RationaleColloid filtration as discussed here refers to the physical removal of colloids from a 
flow system by pore clogging, sieving, and straining. Filtration of colloids generally means the 
retention of colloids moving with the suspending fluid in pores, channels, and fracture apertures 
that are too small or dry to allow passage of the colloids. Two types of physical filtration are 
recognized (e.g., Wan and Tokunaga 1997 [DIRS 108285]), conventional straining and film 
straining. Conventional straining filters colloids if they are larger than a pore throat diameter or 
fracture aperture. Where water saturation is low, colloids may be filtered by film straining if 
their size is greater than the thickness of the adsorbed water film coating the grains of the rock. 
The rate of colloid transport through thin water films depends upon the colloid size relative to the 
film thickness. 
Within the waste package, colloids may form within the defense high-level waste glass 
(e.g., corroded waste fuel pellets) and at its outer surfaces (e.g., corroded defense high-level 
waste glass). They could be filtered within fractures in fuel pellets or trapped at the boundaries 
of disaggregating grains. Colloids forming within fuel rods whose cladding has been breached 
could be filtered at perforations in the cladding. Colloids formed and spalled from the defense 
high-level waste glass could be filtered at perforations in the stainless steel high-level radioactive 
waste container. Colloids reaching the interior of the waste package (after escaping from fuelrod 
cladding and high-level radioactive waste containers) could be filtered at perforations in the 
skin of the waste package. 
Existing colloid filtration models are empirically derived and so are specific to the system 
experimentally characterized. There have been no comprehensive studies of colloid filtration 
within the spent fuel and defense high-level waste glass waste package environments. 
Meaningful analysis of colloid filtration within the waste package is currently not feasible. 
Therefore, a conservative assumption is made: all colloids formed within the waste package (the 
calculated colloid source term) are assumed to exit the waste package and enter the drift without 
filtration. Inclusion of colloid transport processes resulting in retardation in the waste form or

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MDL-EBS-PA-000004 REV 00 25 June 2003 
waste package in the TSPASite Recommendation (SR) calculation would reduce interpreted 
doses. 
As an example of a model applied to nuclear waste disposal, Aguilar et al. (1999 [DIRS 
161648]) modeled the filtration potential of degraded concrete material in plugged boreholes in 
an analysis for the performance assessment of the Waste Isolation Pilot Plant in Carlsbad, New 
Mexico. Their model predicted complete filtration of colloids suspended in Waste Isolation Pilot 
Plant brines, often in borehole vertical distances of a few meters or less. In this abstraction, all 
stable colloids are considered to leave a failed waste package through the failure opening and are 
subsequently not filtered in the surrounding engineered barrier system materialthis assumption 
overestimates the potential consequences of colloid-facilitated transport of radionuclides and is 
considered bounding. 
Confirmation StatusNo confirmation required; this is a bounding assumption. 
Section(s) Used InThis assumption is used throughout. This process is not modeled and 
therefore a discussion on its application is not included in this report. 
5.7 COLLOID SORPTION AT THE AIR-WATER INTERFACE 
AssumptionIt is assumed that colloid sorption at the air-water interface will not occur within 
the waste package. 
RationaleColloid sorption at the air-water interface may occur within the waste package but is 
not considered in the abstraction. As colloid sorption to stationary air-water interfaces would 
retard colloid transport, the assumption that such colloid sorption does not occur over-estimates 
the potential consequences of colloid-facilitated transport and is considered bounding. 
Both hydrophilic and hydrophobic colloids may be sorbed irreversibly at the gas-water interface 
under partially saturated conditions (Wan and Wilson 1994 [DIRS 114430]). Models of colloid 
transport in partially saturated media have been developed in recent years, but there have been no 
experimental studies of transient flow in partially saturated porous media for model comparison 
and calibration. 
As summarized, the concentration of colloids sorbed at the gas-water interface is a function of 
the following conditions: 
 The interface surface area available for colloid uptake, which is a function of the total 
gas saturation 
 The affinity of colloids for the gas-water interface (hydrophobic colloids have higher 
affinities than hydrophilic colloids) 
 The electrostatic charge on the colloidcolloids with lower negative charge exhibit a 
stronger affinity 
 The salinity of the aqueous phase with higher salinity promoting sorption.

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MDL-EBS-PA-000004 REV 00 26 June 2003 
Empirical evidence suggests that the sorption of colloids at the gas-water interface is irreversible 
and the affinity may be stronger than to the rock matrix (Wan and Wilson 1994 [DIRS 114430]). 
Partially saturated conditions may be described or classified by considering degrees of 
saturation. At low water saturations the surface area of the gas-water interface approximates that 
of the rock matrix. Overall, colloid migration is retarded, although colloids may still move 
through the adsorbed water films. At intermediate water saturations there is still an 
interconnected gas phase, although gas flux may be lower. The interface may act as a static 
sorbing surface, but the estimating geometry and surface area is complicated, more so under 
changing saturation state. At high water saturations the majority of the gas is present at small 
gas bubbles that may migrate, transporting sorbed colloids. However, a proportion of the 
bubbles may become trapped in the rock and will effectively immobilize sorbed colloids. 
Colloid migration rates depend more strongly on colloid size as lower saturation states are 
considered (CRWMS M&O 2000 [DIRS 152773]; McGraw 1996 [DIRS 108218]). To examine 
the influence of colloid size on transport, McGraw (1996 [DIRS 108218]) investigated transport 
of monodisperse colloids (five different sizes, between 20 nm and 1900 nm) under both saturated 
and unsaturated conditions in a quartz sand. The results indicated that under saturated conditions 
the time required for breakthrough of each colloid at C/Co = 50 percent was the same as that of 
the breakthrough of a non-reactive tracer, indicating no relationship of colloid size to migration 
under saturated conditions. However, the times required for breakthroughs of the colloids under 
highly unsaturated conditions exhibited a strong relationship between the colloid breakthrough 
and the colloid size with fairly complete breakthrough of the 20-nm colloid and little or no 
breakthrough of the 1900-nm colloid. 
In another set of experiments, McGraw (1996 [DIRS 108218]) compared four sets of 
hydrophobic and hydrophilic colloids (functionalized latex microspheres). Her results indicated 
that transport of hydrophobic colloids depends on colloid size, water film thickness, and colloid 
charge density. In contrast, hydrophilic colloids were not affected by these variables and were 
rapidly transported through the system even under very low moisture contents. McGraw (1996 
[DIRS 108218]) concluded that for hydrophobic colloids, the cumulative mass of colloids 
recovered relative to that input into the column was logarithmically dependent upon the ratio of 
the water film thickness to colloid diameter. In contrast, for hydrophilic colloids, the cumulative 
mass of colloids recovered relative to that input into the column was linearly dependent upon the 
ratio of the water film thickness to colloid diameter, similar but more pronounced than the effect 
with the non-reactive tracer. McGraws findings suggest that unsaturated porous media may not 
greatly impede colloid migration, even for relatively large colloids, although larger colloids will 
tend to be retarded more than smaller ones. 
Although the potential effects of degree of saturation on colloid transport are varied and 
complex, on balance it appears that colloids would be somewhat retarded under low-saturation 
conditions. Therefore, neglect of colloid sorption onto the air-water interface in the total system 
performance assessment calculations is conservative. 
Confirmation StatusNo confirmation required; this is a bounding assumption. 
Section(s) Used InThis assumption is used throughout. This process is not modeled and 
therefore a discussion on its application is not included in this report.

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5.8 GRAVITATIONAL SETTLING OF COLLOIDS 
AssumptionIt is assumed that gravitational settling of colloids will not occur within the waste 
package. 
RationaleGravitational settling of colloids may occur within the waste package, but this 
process is not considered in the abstraction. The use of this assumption, that gravitational 
settling will not occur within the waste package, results in an overestimation of the consequences 
of potential colloid-facilitated transport of radionuclides and is considered bounding because all 
stable colloids are assumed not to settle but to leave a failed waste package through the failure 
opening. 
Confirmation StatusNo confirmation required; this is a bounding assumption. 
Section(s) Used In This assumption is used throughout. This process is not modeled and 
therefore a discussion on its application is not included in this report. 
5.9 MICROBES AND COLLOIDAL ORGANIC COMPONENTS 
AssumptionIt is assumed that processes involving interactions between contaminants and 
microbes and organic components (such as humic, fulvic acids, and microbial debris) do not 
affect the stability of inorganic colloids. 
RationaleThe assumption that it would be appropriate to ignore colloid-microbe interactions 
within the engineered barrier system is based on the review of pertinent literature and on 
professional judgment. This is considered to overestimate the consequences and is considered 
bounding because biological influences are, for the most part, known to encourage colloid 
agglomeration (flocculation and settling out). The basis for this argument is presented in 
Section 6.3.4. 
Confirmation StatusNo confirmation required; this is a bounding assumption. 
Section(s) Used InSection 6.3.4, Potential Effects of Microbes and Organic Components. 
5.10 PARTICLE DENSITY AND SHAPE OF GROUNDWATER COLLOIDS 
AssumptionA colloid mineral density of 2.5 g/cm3 (2.5E-18 mg/nm3) was assumed in the 
calculation of colloid mass concentrations from colloid particle data. Furthermore, all colloid 
particles were assumed to be spherical. 
RationaleThese assumptions were founded on documented measurements of particle density 
on a large range of minerals, including silicate layer-lattice clays (Lide 1995 [DIRS 101876]). 
Silicate minerals have shown to have a particle density of ranging from 2.27 to 2.33 g/cm3 at the 
low range, cristobalite and tridymite, respectively, and 2.67 g/cm3 at the high range (pure quartz) 
(Lide 1995 [DIRS 101876], pp. 4-132 through 4-138). Due to the variability in the particle 
density of silicate layer-lattice clays it is therefore assumed that a value of 2.5 g/cm3 should be 
used for groundwater colloids that are primarily silicate layer-lattice clay minerals. The 
assumption that all colloid particles are spherical is reasonable and is ultimately conservative in 
that it results in larger masses than the use of other configurations such as sheet or rod shaped

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MDL-EBS-PA-000004 REV 00 28 June 2003 
particles of a given diameter size. Note that in Section 6.3.1.3 it is stated that natural 
groundwater colloids in the vicinity of Yucca Mountain include hematite and goethite. 
However, for the purposes of modeling the potential effects of groundwater colloids on 
radionuclide transport, it is stipulated that all natural groundwater/seepage water colloids are 
smectite. 
Confirmation StatusThis assumption is used throughout; no confirmation requiredassumed 
density is based on recorded data from standard Handbook of Chemistry and Physics. 
Confirmation of assumed particle shape (spherical) is not necessary since this is established as a 
bounding assumption. 
Section(s) Used InAttachment I. 
5.11 COLLOIDS ARE UNSTABLE IN GROUNDWATER SAMPLES WITH IONIC 
STRENGTH EXCEEDING 0.05 M 
AssumptionFor ionic strengths greater than or equal to 0.05 M, the concentration of colloids 
is assumed to be 1 x 10-6 mg/L. This small deterministic value represents that colloids are 
unstable (i.e., will agglomerate and settle out of suspension). 
RationaleThis assumption is based upon experimental work that has shown the virtual 
complete flocculation of colloids at high ionic strengths (Liang and Morgan 1990 [DIRS 
109524]; Tombacz et al. 1990 [DIRS 112690]; CRWMS M&O 2001 [DIRS 154071]). 
Confirmation StatusNo confirmation required; this is a bounding assumption. Assumption is 
deemed sound based on credible published scientific literature. 
Section(s) Used InAttachment I. 
5.12 SPECIFIC SURFACE AREA OF IRON OXYHYDROXIDE COLLOIDS 
AssumptionIt is assumed that the specific surface area (SA) for iron oxyhydroxide colloids, 
including a-FeOOH (goethite), a-Fe2O3 (hematite), and Fe(OH)3nH2O (ferrihydrite or hydrous 
ferric oxide) can range from values as low as 1 to 2 m2/g to as high as greater than 700 m2/g. 
RationaleThe assumptions are based upon published values in the literature (Langmuir 1997 
[DIRS 100051]; Dzombak and Morel 1990 [DIRS 105483]; Davis and Kent 1990 [DIRS 
143280]). Davis and Kent and Jenne (1998 [DIRS 162328]) acknowledged that there is large 
uncertainty in the measurements of specific surface area on iron oxyhydroxide minerals. 
Therefore, a wide range in SA values is recommended for use in the TSPA-LA model. 
Confirmation StatusNo confirmation required; this is a bounding assumption. Assumption is 
deemed sound based on credible published scientific literature. 
Section(s) Used InSection 6.3.3.2.

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6. MODEL DISCUSSION 
This section describes the (1) model objectives, (2) features, events, and processes considered in 
the analysis, (3) base-case model, (4) consideration of alternative models, (5) model formulation 
for base-case assessment, (6) base-case model results, (7) description and analysis of the barrier 
capability, and (8) evaluation of alternative models. The supporting information 
(indirect/corroborative data) used in the analysis is described in Section 4.4. 
6.1 MODEL OBJECTIVES 
The purpose of this colloid model abstraction is to provide colloid source terms to the total 
system performance assessment system model. Four waste package types, each containing a 
different waste type or combination of waste types, are defined in Yucca Mountain Science and 
Engineering Report (DOE 2002 [DIRS 155943]): (1) commercial spent nuclear fuel, (2) a 
combination of defense high-level waste glass and DOE spent nuclear fuel (codisposal package), 
(3) defense high-level waste glass, and (4) naval fuel. Colloids will likely be produced as a 
result of the alteration of defense high-level waste glass (commercial and defense SNF waste 
forms have not been shown to produce significant quantities of colloids and those that do form 
are unstable in highly oxidizing environments; see Section 6.3.1.2). The abundance of colloids 
within the breached waste package will depend on the degree of waste form alteration, on the 
quantity of steel corrosion product colloids formed, and on quantities of natural colloids present 
in seepage water. Colloid abundance and stability also depend on many environmental factors 
including the ionic strength, pH, cation concentrations, colloid content of waters entering the 
waste package from the drift, presence or absence of fulvic and humic acids, and microbe 
fragments. Suspended colloids may subsequently flocculate (i.e., particles may coalesce and 
coagulate) and settle by gravity, be chemically or mechanically filtered, or dissolve. If the 
environmental factors change through time colloids may be peptized (i.e., dispersed), colloidsized 
particles may precipitate, or other natural processes may occur. Furthermore, colloids may 
sorb readily at the interfaces between air and water in rocks and engineered barriers. Also, 
depending upon the degree of saturation of the porous medium as well as its configuration, 
colloids may be retarded (or perhaps even be immobilized) or may be transported. These issues 
are relevant to colloid transport, which is of primary concern within the engineered barrier 
system within the drift and in the far field. 
Colloids may affect repository performance if they are generated in significant quantities and are 
stable within the waste package, engineered barrier system, and unsaturated and saturated zones, 
respectively, and are transported. Colloids could potentially carry a significant radionuclide load 
and readily transport these contaminants from the engineered barrier system to the unsaturated 
zone and saturated zone and beyond (see Section 1.1) (Kersting et al. 1999 [DIRS 103282]; 
Penrose et al. 1990 [DIRS 100811]). Processes relevant to the waste package and surrounding 
engineered barrier system environment are discussed in this section in the context of the 
approach to abstraction used in this effort. 
In this section the types and concentrations of colloids that could potentially be generated in the 
waste package from the degradation of the waste (waste form colloids) and corrosion of the 
waste package (corrosion-generated iron oxyhydroxide colloids) are described. Additionally, the 
types of colloids that might be produced from the degradation of steel materials introduced

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MDL-EBS-PA-000004 REV 00 30 June 2003 
during repository construction and operations are discussed. Additional materials that might be 
present in the repository include ferrous alloys such as those used in rockbolts and waste package 
support structures; inorganic liquids such as water for drilling and dust control; organic liquids 
such as antifreeze, hydraulic fluids, and lubricants. There is currently no concrete or cement 
grout in the repository design. The treatment here on man-made materials is focused only on 
steel corrosion products. Potential interactions between inorganic colloids and microbes and 
organic compounds are discussed in Sections 5.9 and 6.3.4. Also the observed types and 
concentrations of colloids naturally present in groundwater (groundwater colloids) that would 
potentially seep or flow into the engineered barrier system during the postclosure regulatory 
period are described. In addition, sorption and desorption of dissolved radionuclides to and from 
colloid surfaces are discussed as well as transport characteristics and mechanisms of colloids 
anticipated in the repository environment. The abstraction is intended to capture the most 
important characteristics of radionuclide-colloid behavior for use in predicting the potential 
impact of colloid-facilitated radionuclide transport on repository performance. Colloid transport 
in the waste package and drift is discussed in EBS Radionuclide Transport Abstraction (BSC 
2003 [DIRS 163935]). 
Output quantities from the waste form and engineered barrier system colloid abstraction to the 
unsaturated zone include defense high-level waste glass colloid concentrations, corrosion 
product (iron oxyhydroxide) colloids, and natural groundwater colloids, discussed in Sections 
6.3.1 and 6.3.2. Colloids potentially produced from degradation of commercial and DOE SNF 
are not modeled, for reasons discussed in Section 6.3.1. Three types of radionuclide association 
with colloids are modeled and described in Section 6.3.3: (1) embedded Pu and Am as a 
consequence of the formation of colloids from defense high-level waste glass; (2) irreversibly 
sorbed Pu and Am on iron oxyhydroxide corrosion products colloids; and (3) reversible sorption 
of Pu, Am, Th, Pa, and Cs onto all colloid types including oxyhydroxide corrosion products. 
Model inputs from upstream data sources include ionic strength and pH of the in-package fluid 
resulting from reaction of water with the waste, ionic strength and pH of the seepage water 
entering the drift, estimates of colloid masses formed from waste form degradation (Argonne 
National Laboratory testing), the concentrations of radionuclides generated from degradation of 
the waste, and Kd values for radionuclides on rocks, minerals, and colloids. 
Model outputs feed the unsaturated zone transport models and include (as described above) 
defense high-level waste glass colloids with embedded radionuclides, irreversibly- and 
reversibly-sorbed radionuclides, and colloid masses. 
The uncertainty associated with the development of parameters representing major processes or 
features modeled in this analysis is described in general terms in Section 6.6.2, Uncertainty 
Associated with the Model Analysis. Additionally, specific details on the types of uncertainties 
associated with the various components of the model elements and the cause(s) for these 
uncertainties are provided within each of the pertinent subsections of Section 6, Model 
Discussion and Section 6.3, Base-Case Model.

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6.2 FEATURES, EVENTS, AND PROCESSES CONSIDERED IN MODEL 
As stipulated in Technical Work Plan for Waste Form Degradation Modeling, Testing, and 
Analyses in Support of SR and LA (BSC 2002 [DIRS 160779], Section 2.1.4), this model report 
addresses the key colloid-oriented FEPs for the waste form and engineered barrier system 
components of the repository that are screened in (i.e., Included FEPs) for TSPA-LA (Table 3). 
FEPs that were screened out (i.e., Excluded FEPs) for TSPA-LA are listed in Table 4. 
Each FEP was screened for inclusion or exclusion in the total system performance assessment 
against three criteria, which are stated as regulatory requirements at NRCs rule 
10 CFR 63.114(d)(e)(f)) [DIRS 158535]. The development of a comprehensive list of FEPs 
potentially relevant to postclosure performance of the potential Yucca Mountain repository is an 
ongoing, iterative process based on site-specific information, design, and regulations. The 
approach for developing an initial list of FEPs, in support of TSPA-SR (CRWMS M&O 2000 
[DIRS 153246]), was documented in Freeze et al. (2001 [DIRS 154365]). The initial FEP list 
contained 328 FEPs, of which 176 were included in TSPA-SR models (CRWMS M&O 2000 
[DIRS 153246], Tables B-9 through B-17). To support TSPA-LA, the FEP list was re-evaluated 
in accordance with the Enhanced FEP Plan (BSC 2002 [DIRS 158966]). 
Tables 3 and 4 provide lists of FEPs that are evaluated in this model analysis, summarize the 
details of their implementation in the TSPA-LA model, and provide specific references to the 
various sections within this document where the issues associated with the FEPs are addressed. 
The TSPA-SR FEP identification numbers and names have been changed for the TSPA-LA; 
however, the changes to the FEPs related to this analyses and document are generally a switch in 
numbers ending in .00 to .0A (or in one case .0B). Technical Work Plan for Waste Form 
Degradation Modeling, Testing, and Analyses in Support of SR and LA (BSC 2002 [DIRS 
160779]) lists the FEPs related to waste form that should be included in the total system 
performance assessment model and refers to this report as the source for the disposition of eight 
FEPs (see BSC 2002 [DIRS 160779], Table 3A). Deviations from the list of FEPs assigned to 
this Model Report include: 
 Removal of FEP No. 2.1.09.14.00 (see BSC 2002 [DIRS 160779], Table 3A). This 
FEP was deemed to be too general (i.e., redundant, and should be split to other FEPs), 
and the effects of the FEP are addressed more succinctly in other FEPs of more detailed 
scope. 
 Addition of FEP No. 2.1.09.02.0A Chemical Interaction with Corrosion Products (see 
Table 3, this document). This FEP was reviewed and determined to be appropriately 
included in discussion in this document. 
 Title of FEP No. 2.1.09.23.00 (BSC 2002 [DIRS 160779], Table 3A) has been changed 
to Stability of Colloids in EBS (see FEP No. 2.1.09.23.0A, Table 3, this document). 
 FEP No. 2.1.09.01.00 (BSC 2002 [DIRS 160779], Table 3A) has been split and 
changed to FEP No. 2.1.09.01.0A and FEP No. 2.1.09.01.0B, which are addressed in

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engineered barrier system models (see BSC 2002 [DIRS 160315], Section 1.2.2.3, 
Table 7) and in the in-package chemistry model report (BSC 2003 [DIRS 163919]). 
 Addition of FEP No. 2.1.09.18.0A Formation of Microbial Colloids in EBS (see 
Table 4, this document). 
 Removal of FEP Nos. 2.1.09.24.00, 2.1.09.19.00, 2.1.09.05.00, 2.1.09.19.0B, 
2.1.09.20.0A, 2.1.09.21.0A, 2.1.09.22.0A, 2.1.09.26.0A, and 2.1.13.03.0A. Of these, the 
FEPs related to in-package and in-drift transport processes are included in BSC (2003 
[DIRS 163935]).

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Table 3. Features, Events, and Processes Included (Screened In) in TSPA-LA and Addressed in this Model Report 
FEP YMP 
No. FEP Title FEP Description 
Location 
Addressed 
in Report 
TSPA-LA Disposition 
2.1.09.02. 
0A 
Chemical 
Interaction with 
Corrosion 
Products 
Corrosion products produced during 
degradation of the waste form and the 
metallic portions of the waste package may 
affect the mobilization and transport of 
radionuclides. Corrosion products may 
facilitate sorption/desorption and 
coprecipitation/dissolution processes. 
Corrosion products may form a rind 
around the fuel that could (1) restrict the 
availability of water for dissolution of 
radionuclides or (2) inhibit advective or 
diffusive transport of water and 
radionuclides from the waste form to the 
EBS. Corrosion products also have the 
potential to retard the transport of 
radionuclides to the EBS. Finally, 
corrosion products may alter the local 
chemistry, possibly enhancing dissolution 
rates for specific waste forms, or altering 
radionuclide solubility. 
Sections 
6.3.1.1, 
6.3.1.3, 
6.3.2.2, 
6.3.2.3, 
6.3.2.4, 
6.3.3.1, 
6.3.3.2 
With respect to colloids, the development of altered fuel and 
glass waste surfaces has been implicitly included by incorporating 
laboratory data derived from fuel and glass waste corrosion 
experiments. Corrosion of steel within the waste package is 
modeled such that iron oxyhydroxide colloids form to which 
radionuclides may sorb and be transported. 
The following phenomena related to colloids and waste form 
degradation are modeled in this Model Report: 
 Formation of smectite colloids containing embedded 
(permanently attached) Pu and Am from corrosion of Defense 
High-Level Waste Glass (DHLWG) (Section 6.3.1.1). 
 Estimation of stability and mass concentration of smectite 
waste form colloids, and concentrations of associated Pu and 
Am, from experimental data and calculated ionic strength and 
pH of in-package and in-drift fluids (Section 6.3.2.2 and 
6.3.2.4). 
 Reversible sorption of dissolved Pu, Am, Pa, Th, and Cs onto 
the smectite colloids using developed Kd values and the 
estimated colloid mass concentrations (Section 6.3.3.1). 
The following phenomena related to colloids and steel corrosion 
are modeled in this Model Report: 
 Formation of iron oxyhydroxide colloids and fixed corrosion 
products in the waste package (Section 6.3.1.3). 
 Estimation of stability and mass concentration of iron 
oxyhydroxide colloids from experimental results and calculated 
ionic strength and pH of in-package and in-drift fluids (Section 
6.3.2.3). 
 Irreversible sorption of Pu and Am onto iron oxyhydroxide 
colloids and fixed corrosion products (Section 6.3.3.2). 
 Reversible sorption of dissolved Pu, Am, Pa, Th, and Cs onto 
iron oxyhydroxide colloids using developed Kd values and the 
estimated colloid mass concentrations (Section 6.3.3.1).

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 34 June 2003 
Table 3. Features, Events, and Processes Included (Screened In) in TSPA-LA and Addressed in this Model Report (Continued) 
FEP YMP 
No. FEP Title FEP Description 
Location 
Addressed 
in Report 
TSPA-LA Disposition 
2.1.09.16. 
0A 
Formation of 
Pseudocolloids 
(Natural) in EBS 
Pseudo-colloids are colloidal-sized 
assemblages (between approximately 1 
nanometer and 1 micrometer in diameter) 
of nonradioactive material that has 
radionuclides bound or sorbed to it. 
Natural pseudo-colloids include microbial 
colloids, mineral fragments (clay, silica, 
iron oxyhydroxides), and humic and fulvic 
acids. This FEP addresses radionuclidebearing 
colloids formed from host-rock 
materials and all interactions of the waste 
and EBS with the host rock environment 
except Pseudo-colloids formed from 
corrosion of the waste form and EBS are 
discussed in FEP 2.1.09.17.0A. Microbial 
colloids are discussed in FEP 
2.1.09.18.0A. Humic and fulvic acids are 
discussed in FEP 2.1.09.13.0A. 
Sections 
6.3.1, 
6.3.1.4, 
6.3.2.2, 
6.3.2.5, 
6.3.3.1 
Natural colloids are modeled as smectite clay colloids in this 
Model Report (Section 6.3.1.4). Pseudocolloids generally form as 
a result of dissolved (aqueous) radionuclides sorbing to existing 
colloids (Section 6.3.1). Kd values are developed to model 
reversible sorption of Pu, Am, Th, Pa, and Cs onto smectite 
groundwater colloids to form pseudocolloids (Section 6.3.3.1). 
Stability of the colloids is determined based on ionic strength and 
pH; concentration is modeled as a sampled parameter based on 
field observations in the Yucca Mountain vicinity (Section 6.3.2.2 
and 6.3.2.5). 
2.1.09.17. 
0A 
Formation of 
Pseudo-colloids 
(Corrosion 
Product) in EBS 
Pseudo-colloids are colloidal-sized 
assemblages (between approximately 1 
nanometer and 1 micrometer in diameter) 
of nonradioactive material that has 
radionuclides bound or sorbed to it. 
Corrosion product pseudo-colloids include 
iron oxyhydroxides from corrosion and 
degradation of the metals in the EBS and 
silica from degradation of cementitious 
materials. Pseudo-colloids formed from 
host-rock materials and all interactions of 
the waste and EBS with the host rock 
environment except corrosion are 
discussed in FEP 2.1.09.16.0A. Microbial 
colloids are discussed in FEP 
2.1.09.18.0A. Waste form glass colloids 
are discussed in FEP 2.1.09.25.0A. 
Sections 
6.3.1, 
6.3.1.3, 
6.3.2.3, 
6.3.3.1, 
6.3.3.2 
Colloids formed from the corrosion of steel in the EBS are 
modeled as iron oxyhydroxide colloids in this Model Report 
(Section 6.3.1.3). Pseudocolloids generally form as a result of 
dissolved (aqueous) radionuclides sorbing to existing colloids 
(Section 6.3.1). Kd values are developed to model reversible 
sorption of Pu, Am, Th, Pa, and Cs onto iron oxyhydroxide 
corrosion colloids to form pseudocolloids (Section 6.3.3.1). In 
addition, Pu and Am are modeled as sorbing irreversibly to iron 
oxyhydroxide corrosion colloids (Section 6.3.3.2). 
Stability of iron oxyhydroxide corrosion colloids is determined 
from the ionic strength and pH of in-package and in-drift fluids 
(Section 6.3.2.3); mass concentrations are modeled as a sampled 
parameter based on laboratory studies of the corrosion of 
miniature waste packages under YMP-relevant conditions and on 
published studies of iron oxyhydroxide colloid concentrations in 
groundwaters associated with high-iron bearing geologic strata 
(Section 6.3.2.3). 
Both fixed and colloidal corrosion products are modeled in the 
waste package (Section 6.3.3.2).

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 35 June 2003 
Table 3. Features, Events, and Processes Included (Screened In) in this Model Report (Continued) 
FEP YMP 
No. FEP Title FEP Description 
Location 
Addressed 
in Report 
TSPA Disposition 
2.1.09.23. 
0A 
Stability of 
Colloids in EBS 
For radionuclide-bearing colloids to 
affect repository performance, the colloids 
in the dispersion must remain suspended, 
that is, be stable, for time scales that are 
long relative to time required for 
groundwater travel. Further, they must 
carry significant concentrations of 
radionuclides. The stability of smectite 
colloids, which is applicable for YMP 
groundwater colloids and waste form 
colloids, is determined primarily by ionic 
strength but also to an extent by pH. The 
stability of iron oxyhydroxide colloids, 
which is applicable to corrosion-product 
colloids, is determined by both ionic 
strength and pH. 
Sections 
6.3.2, 6.3.3, 
6.5 
Colloids in the EBS modeled in this Model Report are smectite 
(waste form and groundwater colloids) and iron oxyhydroxide 
(steel corrosion colloids). Their stabilities are determined from 
ionic strength and pH of the in-package and in-drift fluids, as 
calculated in the TSPA-LA model calculations. 
The stabilities of both smectite and iron hydroxide colloids are 
determined at each time step executed in the TSPA-LA 
calculations (Section 6.3.2). These determination are then used 
to calculate concentrations of radionuclides associated with the 
colloids (Section 6.3.3). Ionic strength, pH values, and dissolved 
radionuclide concentrations are taken from intermediate TSPA-LA 
calculation values from submodels described in the in-package 
chemistry waste package (ionic strength and pH), solubility limits 
(dissolved radionuclides), and near-field chemical environment 
(drift ionic strength and pH) model reports (Section 6.5). 
2.1.09.25. 
0A 
Formation of 
Colloids (Waste 
Form) by 
Coprecipitation 
in the EBS 
Dissolved radionuclides and other ions 
may co-precipitate to form colloids. Coprecipitates 
may consist of radionuclides 
bound in the crystal lattice of a dominating 
mineral phase or may consist of 
radionuclides engulfed by a dominating 
mineral phase. 
Sections 
6.3.1.1, 
6.3.2.2, 
6.3.2.4 
Colloids apparently formed from coprecipitation of smectite and 
embedded radionuclide-bearing phases were observed in the 
DHLWG degradation tests (Section 6.3.1.1). Colloids produced 
from degradation of DHLWG are modeled as smectite colloids 
with embedded (assumed permanently attached) radionuclides 
(Pu and Am). These may, in a broad sense, be considered 
coprecipitates. The concentrations of radionuclides associated 
with those colloids are based on empirical results from YMPrelevant 
DHLWG corrosion experiments (Section 6.3.1.1 and 
6.3.2.4). Mass concentrations of the colloids are based on those 
experiments together with consideration of colloid mineralogy and 
the effects of ionic strength and pH on the stability of the colloids 
(Section 6.3.1.1, 6.3.2.2, and 6.3.2.4). 
NOTE: EBS = engineered barrier system; TSPA = total system performance assessment; DHLWG = defense high-level waste glass.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 36 June 2003 
Table 4. Features, Events, and Processes Excluded (Screened Out) in this Model Report 
FEP YMP 
No. 
FEP Title FEP Description 
Location 
Addressed 
in Report Technical Basis for Exclusion 
2.1.09.18. 
0A 
Formation of 
Microbial 
Colloids in EBS 
Biological activity is important to 
consider because of the potential impact on 
aqueous chemical conditions within the 
waste and EBS. In deep subsurface 
environments, biological activity is limited 
to microbiological activity and may include 
effects of natural and anthropogenic 
bacteria (e.g., anaerobic, methanogenic, 
sulfate reducers, etc.), protozoans, yeast, 
viruses, and algae. This FEP includes a 
broad range of effects of biological impacts, 
including the effects of microbes on 
corrosion of waste containers, cladding, 
and the waste form; bioreduction of 
multivalent contaminants, metals, and 
sulfate; generation of organic complexants 
and gases as metabolic by-products; and 
the formation of biofilms and impact on 
transport. 
Sections 5.9, 
6.3.4 
The effects of colloid-facilitated radionuclide transport 
stemming from biological activity have generally been excluded 
from the TSPA-LA on the basis of low probability and 
consequence. Because inorganic aqueous conditions dominate 
DHLWG degradation rates, and microbial degradation is 
secondary, this is excluded on the basis of low consequence. The 
potential influence of organic complexants from microbial 
metabolism on radionuclide transport is assumed not to affect the 
stability of inorganic (mineral) colloids (Sections 5.9 and 6.3.4), 
i.e., inorganic colloid stability is determined by fluid chemistry 
(ionic strength and pH); therefore this process is also excluded on 
the basis of low consequence. 
Microbe-induced reduction of radionuclide, metal, and sulfate 
contaminants would decrease their mobility (see Section 6.3.4), 
which is beneficial, and therefore excluded on the basis of low 
consequence. Since biofilms would tend to retard radionuclides, 
which is beneficial, this process is also excluded on the basis of 
low consequence. 
Consequently, it is concluded that there will not be a 
significant change in either time or magnitude of the expected 
annual dose due to microbial activity in the EBS. 
2.1.09.15. 
0A 
Formation of 
true (intrinsic) 
colloids in EBS 
True colloids are colloidal-sized 
assemblages (between approximately 1 
nanometer and 1 micrometer in diameter) 
consisting of hydrolyzed and polymerized 
radionuclides. They may form in the waste 
package and EBS during waste-form 
degradation and radionuclide transport. 
True colloids are also called primary 
colloids, real colloids, Type I colloids, 
Eigenkolloide, and intrinsic colloids (or 
actinide intrinsic colloids, for those 
including actinide elements). 
Section 
6.3.1 
True colloids may form from saturated solutions in close proximity 
to degrading waste (Section 6.3.1). However, true colloids may 
not be routinely detectable, as they would be determined as 
dissolved radionuclides. Further, they would be likely to dissociate 
in dilute fluids as well as sorb to substrates. Therefore, the 
formation of true colloids in the EBS has been excluded from the 
TSPA-SR on the basis of low consequence. 
NOTE: EBS = engineered barrier system; DHLWG = defense high-level waste glass.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 37 June 2003 
6.3 BASE-CASE MODEL 
A discussion of the colloid model is presented here, organized by major concepts considered and 
the specific ideas and values developed and incorporated into the model. Accordingly, the 
following subjects are discussed: colloid formation from defense high-level waste glass, 
commercial SNF, and DOE SNF; formation of corrosion products, including colloids, from 
degradation of steel within the waste package and drift; natural occurrence of groundwater 
colloids; stability and concentration of all modeled colloid types; radionuclide attachment to 
colloids; and microbial interactions. 
For reasons explained in the following respective sections, colloids potentially generated from 
the degradation of commercial and DOE SNF are not included in the colloid model abstraction. 
However, to present the background information that was necessary to reach this decision, 
relevant research is described in Section 6.3.1, including laboratory testing and natural analog 
field observations. 
Colloids formed from corrosion of introduced materials are modeled only as iron oxyhydroxide 
colloids. As described in Section 6.1, materials introduced during repository construction may 
include various steel alloys, organic liquids, and cementitious materials. Concrete and cement 
grout are currently not a part of the repository design, and colloids derived from them are not 
considered. The assumption is made that microbes and organic compounds do not affect the 
stability of inorganic colloids (colloids comprised of mineral fragments); therefore, organic 
colloids are not modeled (see Section 5, Assumption 5.9). Potential interactions between 
inorganic colloids and microbes and organic compounds are discussed in Sections 5.9 and 6.3.4. 
6.3.1 Colloid Formation and Occurrence 
Following is a discussion of colloid types, definitions, and pertinence to the repository. A 
summary of the colloid types modeled in this abstraction is provided at the end of this section. 
Figure 1 is a schematic illustrating colloid types. 
Colloids by definition have at least one dimension between 1 nm and 1 m. Often, particularly 
in reporting of experimental results, the upper end of the colloid size range is 450 nm, due to 
conventional dimensions of laboratory equipment (primarily filters). 
True ColloidsTrue colloids are colloidal-sized assemblages (between approximately 
1 nanometer and 1 micrometer in one dimension) formed from the hydrolysis and polymerization 
of actinide ions dissolved in solution. They may form in the waste package and engineered 
barrier system during waste form degradation and radionuclide transport. True colloids are also 
called primary colloids, real colloids, Type I colloids, Eigenkolloide, and intrinsic colloids (or 
actinide intrinsic colloids, for those including actinide elements). The formation of real colloids 
will be solubility limited, based on the solution chemistry. This prevents significant introduction 
of real colloids to the environment (CRWMS M&O 2001 [DIRS 154071], Section 6.1). There 
has been no evidence of their formation in Argonne National Laboratory defense high-level 
waste glass degradation tests (Ebert 1995, Sections 6.2.1 and 6.2.2 [DIRS 113219]), and even if 
present they would be difficult to detect. Degradation of commercial SNF may form real 
colloids (e.g., schoepite-like U hydroxides) close to the fuel surface where the fluid may be

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 38 June 2003 
saturated with respect to U, but they are likely to dissolve in unsaturated fluid. In addition, the 
generation and migration of real colloids is of no consequence in natural aquifer systems because 
real colloidsundergo formation of pseudocolloids in the near- or far-field aquifer system 
(Kim 1994 [DIRS 109521], p 50). For these reasons, true colloids are not modeled in the 
abstraction. 
Waste Form ColloidsWaste form colloids may provide one of the most significant 
contributions to colloid-facilitated radionuclide transport. These colloids form from the 
nucleation of colloids from waste form dissolution and from spallation (flaking off) of 
colloid-sized waste form alteration products. Waste form colloids contain radionuclides and 
have the potential for increasing mobile radionuclide concentrations to levels higher than 
achievable with real colloids or pseudocolloids (CRWMS M&O 2001 [DIRS 154071], Section 
6.1). Dissolved radionuclides and other ions may co-precipitate to form colloids. Co-precipitates 
may consist of radionuclides bound in the crystal lattice of a dominating mineral phase or may 
consist of radionuclides engulfed by a dominating mineral phase. 
Four broad categories of waste form are to be placed in the repository (DOE 2002 [DIRS 
155943]). The most abundant waste type is commercial SNF from commercially owned and 
operated electric power reactors. DOE SNF is a diverse collection of waste from reactors at 
DOE nuclear complex sites. Defense high-level waste glass is a borosilicate glass-based waste 
form containing radionuclides. In the following descriptions, commercial and DOE SNF are 
treated together. 
Investigations of the degradation of defense high-level waste glass (CRWMS M&O 2001 [DIRS 
154071]) show that waste form colloids have formed by co-precipitation of radionuclide-bearing 
phases with colloid-sized clay phases formed homogeneously in the solution contacting the 
waste. Under conditions in which water drops onto the waste, spallation of colloid-sized 
fragments of co-precipitated clay (primarily) and radionuclide-bearing phases from the alteration 
layers formed on the waste form surfaces. Through these mechanisms, radionuclide-bearing 
phases can become embedded in alteration phases, primarily clays. 
PseudocolloidsPseudocolloids are colloidal-sized particles (between approximately 
1 nanometer and 1 micrometer in diameter) that consist of usually (but not necessarily) 
nonradioactive particles with radionuclides sorbed to them. Natural pseudocolloids include 
mineral fragments formed from the host rock, microbes and microbe fragments, and humic and 
fulvic acids. Pseudocolloids form as a result of dissolved (aqueous) radionuclides sorbing to 
existing colloids (e.g., clay, iron oxyhydroxides, silica). At YMP, pseudocolloids may develop 
as a result of radionuclide association with waste form colloids formed during degradation of 
defense high-level waste glass; radionuclide association with corrosion-product colloids formed 
during corrosion of waste package materials and other metallic materials; and radionuclide 
association with naturally occurring groundwater colloids present in YMP groundwater. 
Seepage/Groundwater ColloidsNaturally occurring colloids (referred to in this report as 
groundwater colloids) may be inorganic (mineral fragments) or organic (microbes and humic 
substances). At YMP, inorganic groundwater colloids, primarily consisting of clay, silica, and 
iron oxyhydroxides, may be transported in seepage water into the repository from the vadose 
zone above it or may be formed due to changes in chemical conditions near the repository.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 39 June 2003 
Pseudocolloids may form due to the sorption onto these natural colloids of radionuclides 
mobilized from degradation of the waste form. Pseudocolloids thus formed in the waste and 
engineered barrier system may influence radionuclide transport. At YMP, organic colloids are 
not important. Humic substances are not sufficiently abundant in YMP groundwaters to impact 
transport (Section 6.3.1.4). Microbes, as large colloids, are susceptible to filtration during 
transport. 
Colloids are modeled in the abstraction as follows: 
 Waste form colloids. Colloids from the corrosion of defense high-level waste glass 
(Section 6.3.1.1) are modeled as smectite colloids with embedded Pu and Am. 
Colloids from the corrosion of commercial and DOE SNF are not modeled (Section 
6.3.1.2). 
 Corrosion product colloids. Colloids from the corrosion of steel components in the 
engineered barrier system are modeled as iron oxyhydroxide colloids, as they will likely 
be a mixture or combination of hydrous ferric oxide, goethite (FeOOH), and hematite 
(Fe2O3) (Section 6.3.1.3). 
 Seepage/groundwater colloids. Naturally occurring colloids are modeled as smectite 
colloids (Section 6.3.1.4). Such components of groundwater colloids as humic and fulvic 
acids, microbes and their detritus and metabolic products are not modeled. 
O-Pu-O-Pu-O 
O-Pu-O-Pu-O 
O 
O
O 
O
O O 
groundwater 
colloid Rn+ 
waste form 
alteration phases 
Rn+ 
(a) (b) (c) 
NOTE: Several types of radionuclide-bearing colloids are depicted: (a) pseudocolloids, (b) true colloids, and 
(c) waste form colloids. The radionuclide (Rn+) associated with the pseudo and waste form colloids can be 
an ionic species, a real colloid, or a discrete radionuclide-bearing phase. The size range for the colloids is 
approximately 1 to 1000 nm. 
Source: Adapted from CRWMS M&O 2001 [DIRS 154071], Figure 1. 
Figure 1. Several Types of Radionuclide-Bearing Colloids 
6.3.1.1 Colloids from the Corrosion of Defense High-Level Waste Glass 
A description of colloids formed from the corrosion of defense high-level waste glass under 
unsaturated (drip) test conditions and under static-saturated (product consistency test) test 
conditions is presented in this section. The unsaturated tests are thought to be representative of 
conditions likely to occur in a geologic repository with simulated aged canister components

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 40 June 2003 
present and periodic injection of groundwater and air. The unsaturated tests allow the spallation 
mechanism to be examined (Section 6.4.2). The static tests appear to be a suitable method for 
simulating colloid formation from glass reaction (Buck and Bates 1999 [DIRS 109494]) where 
similar colloids (smectite clay and rhabdophane colloids) are formed in both unsaturated and 
saturated tests. Metal-bearing oxide colloids (birnessite, asbolane, and iron oxides) have been 
detected only in the unsaturated tests, most likely due to the presence of the aged canister 
components. Uranyl silicates and U-Ti phases have only been found in the saturated tests under 
conditions that promote saturated silica solutions from the reacted glass corrosion. 
Colloids formed from the corrosion of defense high-level waste glass are included in the colloid 
model and abstraction (Sections 6.3.2.4 and 6.5.1). They are modeled as smectite with 
associated Pu and Am embedded within (or otherwise permanently attached to) the colloids. 
This is based on observations of colloids with associated Pu that formed during corrosion testing 
of defense high-level waste glass at Argonne National Laboratory. A description of the testing 
follows. 
Testing on corrosion of defense high-level waste glass has gone on for over four years in the case 
of static-saturated tests wherein glass samples are immersed in fluid and for over sixteen years in 
the case of drip tests where fluid is dripped at specified rates onto the glass sample (CRWMS 
M&O 2001 [DIRS 154071]). In the static tests, surface area (SA) of the sample was varied 
relative to the volume (V) of fluid used; this proportion is referred to as SA/V. SA was 
determined using geometric estimates of crushed materials, not by a gas adsorption method. 
Glass waste forms tested include Savannah River Laboratory and West Valley Demonstration 
Project glasses. Fluids used were tuff-equilibrated J-13 water (EJ-13) and deionized water. 
Methods used to characterize colloids produced during the tests include transmission electron 
microscopy and filtration (analysis of filtrates with inductively coupled plasma-mass 
spectrometry or alpha spectroscopy; CRWMS M&O 2001 [DIRS 154071], Section 6.2). 
Descriptions of the tests may be found in Colloid-Associated Radionuclide Concentration 
Limits: ANL (CRWMS M&O 2001 [DIRS 154071], Section 6.2.1) and Ebert (1995 [DIRS 
113219]). 
Colloids produced from the degradation of both types of glass waste were primarily smectite clay 
containing discrete radionuclide-bearing phases, which are incorporated (embedded) in the clay 
(CRWMS M&O 2001 [DIRS 154071], Section 6.2.1). Iron silicate colloids were also observed. 
The embedded phases were identified as primarily brockite (thorium calcium orthophosphate) 
and an amorphous thorium-titanium-iron silicate, similar to thorutite. The phases also contained 
other actinides and rare earth elements. Uranium was detected within the clays and iron silicates 
in some samples. 
Currently, limited data are available on the chemical and physical properties of the embedded 
phases, so that their solubility and disassociation/association properties with the clay cannot be 
derived and used in the model. The colloidal properties of the embedded radionuclide-bearing 
phases, therefore, appear to be governed by the properties of the smectite, and the stability (and 
therefore mobility) of smectite colloids will control the mobility of the embedded phases. 
Accordingly, the radionuclides are stipulated to be embedded within the smectite colloids.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 41 June 2003 
As stated above, other colloidal phases (besides smectite) have been identified from the saturated 
and unsaturated defense high-level waste glass corrosion tests. These include manganese-based 
clays (asbolane and birnessite), phosphate phases (calcium silica phosphate and rare-earth 
phosphates), carbonate-bearing phases (calcite and dolomite), and uranyl silicates (weeksite) or 
uranium Si-Ti bearing phases (Buck and Bates 1999 [DIRS 109494]). 
Figure 2 depicts the process of defense high-level waste glass degradation with the subsequent 
formation of waste form colloids. As the glass corrodes, the clay alteration product forms, 
grows, and evolves as a layer on the surface of the glass. The clay layer grows as the glass 
beneath the clay is altered and clay-forming elements saturate in the solution and subsequently 
precipitate on the clay surface. Through these mechanisms colloid-sized clay that does not 
attach to the clay layer may also precipitate from the solution in proximity to the clay layer 
(CRWMS M&O 2001 [DIRS 154071], Section 6.2.1). 
NOTE: Schematic of colloid formation from waste form corrosion whereby several processes are represented: 
(1) spallation of radionuclide bearing alteration phases from the waste form that are within the colloidal size 
range, and (2) nucleation of colloids from ions dissolved from the waste form and sorption of ionic 
radionuclide species or radionuclide -bearing phases. Particle growth occurs by precipitation on nuclei and 
is controlled by factors such as ionic strength, temperature, pH, and solubility. When particle diameters 
exceed 1 micron or solution chemistry destabilizes the colloids, deposition, or coagulation and gravitational 
settling of radionuclide-bearing alteration phases occur. 
Source: Modified from Figure 2, CRWMS M&O 2001 [DIRS 154071]. 
Figure 2. Schematic of Colloid Formation from Waste Form Corrosion 
It was observed in the static-saturated tests that colloids developed and increased in 
concentration (population) with time, up to a point where the colloid concentration reached a

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 42 June 2003 
maximum and produced an unstable dispersion. This was attributed by the investigators 
primarily to the concomitant increase in ionic strength to a threshold above which the colloids 
flocculated and settled by gravity (CRWMS M&O 2001 [DIRS 154071], Section 6.2.1). 
Based on these Argonne National Laboratorys experimental results (DTNs: 
LL991109751021.094 [DIRS 142910], LL000905312241.018 [DIRS 152621], the following 
approximate relationship was developed from inspection of the data presented in Figures 3 and 8 
and may be used to relate the Pu concentration to colloid concentration: 
1 ppm colloids = 2 x 10-8M Pucoll (Eq. 1) 
Pucoll is the concentration of Pu associated with colloids. To enable the use of bounding values 
for applying the relationship, the approximate maximum (and bounding) value for Pucoll of 
1 x 10-7 from Figure 8 was adopted to correspond with the approximate maximum (and 
bounding) colloid mass concentration of 5.0 ppm from Figure 3. Division of maximum Pucoll by 
the maximum colloid mass concentration yields the relationship in Equation 1. 
Since Pu and Am are assumed to behave similarly (Section 5.1), the colloid-associated Am 
concentration was calculated by multiplying the ratio of Am to Pu in the radionuclide inventory 
by the Pu concentration at each time step of the TSPA-LA model calculations. 
[Colloids] total (ppm) 
0E+0 
1E-9 
2E-9 
3E-9 
4E-9 
5E-9 
6E-9 
0 50 100 150 200 250 300 350 
Time (days) 
0.0 
1.0 
2.0 
3.0 
4.0 
5.0 
Pu-colloids (filt) Total Colloids (DLS) 
[Pu colloid] (M) 
NOTE: Plutonium concentration associated with colloids fraction (6 to 450 nm size fraction from filtration data) 
and total colloid concentration (from dynamic light scattering measurements) as a function of test 
duration for the SRL 131A glass at 2,000/m (T = 90C). The triangles, representing concentration of 
plutonium in filtered colloids, correspond to the left axis. The circles, representing the total colloid mass, 
correspond to the right axis. Note that, with the scales used in the graph, the triangles and circles 
coincide. 
Source: Adapted from CRWMS M&O 2001 [DIRS 154071], Figure 24; DTN: LL000905312241.018 [DIRS 
152621], data: p. 70, 131A/2K, time 14980 days, Pu_s(M); right-hand x-axis values from DTN: 
LL991109751021.094 [DIRS 142910], p. 32. 
Figure 3. Concentrations of Pu and Colloids as a Function of Defense High-Level Waste Glass 
Corrosion Test Duration

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MDL-EBS-PA-000004 REV 00 43 June 2003 
6.3.1.2 Colloids from the Corrosion of Commercial and DOE Spent Nuclear Fuel 
Long-term corrosion testing of commercial SNF and DOE SNF under hydrologically 
unsaturated, oxidizing conditions have been performed to examine the release of radionuclides 
and, specifically for the context of this report, the release in the form of colloids. Testing was 
designed to simulate a variety of Yucca Mountain repository relevant water-exposure conditions 
for several spent nuclear fuels with a range of fuel burnups and compositions. Results from the 
unsaturated testing of commercial SNF and DOE SNF indicated spallation of alteration products 
containing low concentrations of uranium-based colloids (and low concentrations of actinides), 
dissolution of the uranium-based colloids over a short time duration (less than several months), 
and sorption dominating the behavior of the actinides (onto clay colloids or onto metal surfaces). 
Thus, colloids from commercial SNF and DOE SNF were neglected in the colloid modeling and 
abstraction based upon the unsaturated testing results from the commercial SNF and DOE SNF, 
characterization of uranium phase colloid suspensions, and natural analog studies. A summary 
of results affecting colloid release from the fuels during unsaturated testing is presented in 
Sections 6.3.1.2.1 and 6.3.1.2.2. 
6.3.1.2.1 Commercial Spent Nuclear Fuel 
Assessment of the importance of potential colloid formation from commercial SNF is based on 
four major observations: (1) very low colloid concentrations were observed in the commercial 
SNF degradation tests, at least an order of magnitude less than concentrations observed in the 
defense high-level waste glass degradation tests (based on dynamic light scattering 
measurements) (Mertz et al. 2003 [DIRS 162032]); (2) the fraction of uranium in the colloid 
mass was uniformly low in the commercial SNF tests, the only deviation from this occurring 
immediately following one of two changes in vessel configuration in which the uranium fraction 
increased but rapidly decreased to the approximate level of earlier values (Mertz et al. 2003 
[DIRS 162032]); (3) suspensions of meta-schoepite and UO2+x colloids in J-13 groundwater 
appear to dissolve in short-term hydrologically saturated tests; their stability in unsaturated 
solutions has not been tested (Mertz et al. 2003 [DIRS 162032]); and (4) field studies at 
uranium-bearing deposits indicate generally that under oxidizing conditions at near-neutral pH, 
colloid particles contain little uranium and there is little sorption of uranium complexes to 
colloids. 
In contrast to the defense high-level waste glass unsaturated tests, few colloids have been 
detected in the test solutions from unsaturated corrosion tests of commercial SNF under likely 
water contact scenarios at Yucca Mountain (Mertz et al. 2003 [DIRS 162032]). A detailed 
discussion of the tests and uncertainties is found elsewhere (Mertz et al. 2003 [DIRS 162032]); 
only a summary of the test results and uncertainties associated with the testing follows here. One 
of the reasons surmised for the low colloid release in the commercial SNF tests was the test 
configuration in which the Zircaloy-4 support for the fuel fragments had 7-micron holes. 
However, the results from the unirradiated UO2 tests also show few colloids after the formation 
of alteration products (Wronkiewicz et al. 1997 [DIRS 102048]). The unsaturated tests on 
unirradiated UO2 had a test configuration with large 23 mm holes at the holder base allowing 
for the spallation of UO2+x particulate during initial corrosion; however, the formation of a dense 
mat of alteration products during the UO2 corrosion apparently reduced particulate release by 
trapping particulate in the altered products (Wronkiewicz et al. 1997 [DIRS 102048]). A similar

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MDL-EBS-PA-000004 REV 00 44 June 2003 
mechanism whereby the alteration products minimize particulate release may be applicable to the 
commercial SNF unsaturated tests. 
The concentration of released particulates or colloids from the commercial SNF tests is very low 
except during test conditions corresponding to disruptive events, such as movement of the fuel 
from one retainer to another (Mertz et al. 2003 [DIRS 162032]). In that case, colloid and 
particulate concentrations increased temporarily but returned to very low concentrations after the 
disruption (Mertz et al. 2003 [DIRS 162032]). While this indicates that disruptive events may 
contribute to the release of particulates and colloids from commercial SNF, it also indicates that 
the longevity of the colloids in the leachate is short. It is possible that the dense mat of alteration 
products acts as a filter for reducing particulate concentrations under unsaturated test conditions 
as was observed in the unirradiated UO2 tests (Wronkiewicz et al. 1997 [DIRS 102048]). The 
stability of these alteration phases is unknown at this time. Likewise, it is possible that the 
uranium-bearing colloidal material dissolved in the chemically under-saturated leachate. 
During the oxidative dissolution of commercial SNF in the Argonne National Laboratory 
unsaturated tests, a suite of alteration products were formed on the fuel surface. In the vapor 
tests (corrosion of UO2 with water vapor), uranyl oxyhydroxides were observed, such as 
dehydrated schoepite and meta-schoepite. However, the introduction of sodium and silicon-rich 
groundwater in the drip tests allow the incorporation of sodium and silicon in the alteration 
products. In the high drip rate tests, Na-, Ca-, and Si-bearing uranyl compounds were identified 
(such as Na-boltwoodite, (Na,K)(UO2)(SiO3OH)(H2O)). Of those colloids identified in the 
commercial SNF tests (CRWMS M&O 2001 [DIRS 154071], Section 6.2.2), one sample 
contained primarily a hydrous uranium oxide (schoepite) and a partially crystalline uranium 
silicate (soddyite). The colloids contained the rare earth elements: La, Ce, Pr, Nd, Sm, and Eu. 
Plutonium was not detected in these colloids; however, alteration on the corroded surface of the 
spent fuel contained significant concentrations of Pu, along with Zr, Ru, and rare earth elements 
in a layer approximately 100 nm thick (CRWMS M&O 2001 [DIRS 154071], Section 6.2.2). In 
another sample, smectite clay colloids were formed that were similar structurally and 
compositionally to the smectites produced in the glass tests. 
The primary sources of uncertainty include measurement errors and limitations associated with 
the test design and apparatus. Measurement uncertainties arise from determination of mass, 
calculation of volume, determination of particle sizes by filtration, and measurement of 
concentrations by inductively coupled plasma mass spectroscopy. Experimental uncertainties 
include localized inhomogeneity of nuclides in irradiated fuel and loss of leachate or fuel during 
sampling operations. Discussion of these uncertainties is found in the commercial SNF colloid 
data report (Mertz et al. 2003 [DIRS 162032]). 
6.3.1.2.2 DOE Spent Nuclear Fuel 
Of the approximately 250 different types of fuel in the DOE SNF inventory, metallic uranium 
fuel comprises approximately 85 percent (by weight) of that inventory and thus was selected for 
corrosion testing. An irradiated uranium metal fuel from the N-Reactor at Hanford was tested in 
an experimental setup similar to that used at Argonne National Laboratory for testing 
commercial SNF. Additional details on the testing can be found elsewhere (DTN: 
MO0306ANLSF001.459 [DIRS 163910]). Corrosion testing of metallic uranium samples

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MDL-EBS-PA-000004 REV 00 45 June 2003 
resulted in rapid oxidization (within a few months) of the uranium primarily to an oxide sludge 
consisting of UO2 and higher oxides of uranium (DTN: MO0306ANLSF001.459 [DIRS 
163910]). Although the uranium fuel disintegrated rapidly, corrosion testing was continued to 
determine the effect of groundwater leaching on the fuel sludge. Results from the corrosion tests 
showed that the composition of the DOE SNF colloids evolve over time from an initially UO2- 
rich population, to a mixed colloid population containing UO2 and higher oxides of U as well as 
smectite clays, to a population that appears to be dominated by U-containing smectite clays. 
After approximately one year of testing the DOE SNF, the total quantity of uranium in the sludge 
represented approximately 99 weight percent of the original uranium fuel sample, while that in 
the colloid size group corresponded to 0.002 to 0.006 weight percent of the original uranium fuel 
sample. The quantity of uranium in the sorbed fraction was 0.1 to 0.3 weight percent of the 
original fuel sample (DTN: MO0306ANLSF001.459 [DIRS 163910]). Sorbed material is 
operationally defined as material that adhered to the stainless steel vessel wall and was 
subsequently solubilized in HNO3; it includes sorbed solutes, sorbed colloids, and precipitates 
(DTN: MO0306ANLSF001.453 [DIRS 163910]). The disposition of Pu during DOE SNF 
corrosion showed that Pu is associated predominantly with the colloidal, particulate, and sorbed 
size fractions. The 239Pu/ 238U ratios in the colloid fraction are significantly larger than those in 
the other fractions (sorbed, particulate, and dissolved) and is the only fraction that showed 
enrichment of Pu in comparison to that in the fuel prior to corrosion 
(DTN: MO0306ANLSF001.459 [DIRS 163910]). Results from the testing support a model of 
metallic uranium corrosion in which Pu is both incorporated in spalled particulates and colloids 
and is significantly adsorbed to the surface of colloids (such as groundwater clays) upon 
dissolution of spalled particulates or colloids (DTN: MO0306ANLSF001.459 [DIRS 163910]). 
Uncertainties associated with these data and experiments include measurement uncertainties and 
uncontrolled experimental factors. Measurement uncertainties arise from determination of mass, 
calculation of volume, determination of particle sizes by filtration, and measurement of 
concentrations by inductively-coupled plasma mass spectroscopy. Experimental uncertainties 
include localized inhomogeneity of nuclides in irradiated metallic uranium fuel, loss of sludge 
particles from the sample holder during sampling operations, and most significantly the 
extrapolation of results from only two samples of irradiated fuel. Additional discussion of the 
uncertainties associated with the DOE SNF unsaturated testing is found elsewhere 
(DTN: MO0306ANLSF001.459 [DIRS 163910]). 
6.3.1.2.3 Uranium Phase Colloid Suspensions 
As uranium-based spent nuclear fuels will be prevalent at the high-level waste repository at 
Yucca Mountain, the colloidal properties of a mixture of two uranium minerals under saturated 
conditions that promote stable colloids have been examined (Mertz et al. 2003 [DIRS 162032]). 
The results suggest that meta-schoepite, (UO2)4(OH)65H2O, and UO2+x colloids are stable under 
short-duration tests with respect to dissolution and interparticle interactions at near neutral and 
higher pH values in solutions saturated with respect to these phases (Mertz et al. 2003 [DIRS 
162032]). However, under repository relevant conditions, these colloids appear to dissolve after 
introduction to J-13 groundwater in short duration tests (reduction in colloid size and 84 percent 
of the uranium was in the dissolved fraction) (Mertz et al. 2003 [DIRS 162032]).

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6.3.1.2.4 Field Evidence from Natural Analogs 
There are several published studies of uranium mobility and transport at uranium mines and 
deposits and at locations where other metals are mined. Examples are the Koongarra and 
Nabarlek uranium deposits in Australia (Short et al. 1988 [DIRS 113937]; Payne et al. 1992 
[DIRS 124812]) and the Freiberg zinc-lead-silver mine in Germany (Znker et al. 2000 [DIRS 
162746]). All of the references studied suggest that colloidal uranium will not be a significant 
contributor to colloid-associated radionuclides under the oxic and essentially pH-neutral 
conditions prevailing at Yucca Mountain. 
Znker et al. (2000 [DIRS 162746]) investigated a unique situation at the Freiberg mine in which 
anoxic, relatively acidic mine water issued into oxic drainage gallery water and formed, in the 
authors words, a large geochemical colloid generator. The colloids sampled in the drainage 
gallery were primarily iron and aluminum hydroxides, ranging in size from 100 to 300 nm and in 
concentrations of about one mg/L. In the mine water (pH approximately 5) uranium occurred 
mainly as UO2CO3,aq, and approximately 50 percent of total uranium was associated with the 
relatively few colloids measured. In the oxidized, more neutral drainage gallery water (pH 
approximately 7.2), uranium occurred mainly as Ca2UO2(CO3)3,aq and UO2(CO3)2
-2, and the 
fraction of uranium associated with colloids was essentially zero. 
Znker et al. (2000 [DIRS 162746]) stated that, [u]ranium showed strictly non-colloidal 
behavior, and conducted experiments (acidification of samples with nitric acid) to investigate 
the phenomena observed. They noted that the colloid fraction decreased with decreasing pH, and 
that the maximum uranium sorption onto colloids occurred at about pH 5. They concluded that 
acidification destroys uranyl carbonato complexes of ligand numbers greater than one, and as a 
result uranyl prevails and sorbs to colloids in the mine water. In the neutral drainage gallery 
water the prevailing uranyl carbonato complexes prevent the uranyl from being adsorbed to the 
colloids while not sorbing themselves. 
The uranium deposit at Koongarra and Narbalek, Northern Territory, Australia, has groundwater 
that is of low salinity, pH from approximately 6.5 to 7.5, Eh above about +50, and with Mg2+ and 
HCO3
- as the primary dissolved ions (Short et al. 1988 [DIRS 113937]). Colloids are primarily 
iron oxyhydroxides and clays, with variable amounts of silica and discrete silica colloids. The 
colloid sizes ranged from about 18 nm to 1 m. Fe-colloid concentrations ranged from 1.6 to 4.9 
g/L (one value was 7.9 g/L); Si-colloids from less than 1 to 37 g/L (Short et al. 1988 [DIRS 
113937]). Particles containing primarily uranium were noted, with sizes of 0.04 to 0.3 m and 
concentrations of about 108 pt/L (particles per liter; mass concentrations were not reported; 
Payne et al. 1992 [DIRS 124812]). 
Short et al. (1988 [DIRS 113937]) noted that uranium occurs mostly as soluble species; the 
fraction of total uranium associated with colloids is reported as 2 percent at Nabarlek and up to 
11 percent at Koongarra. Payne et al. (1992 [DIRS 124812]) report that in the ore zone the 
uranium particles comprised less than 1 percent of the total uranium; generally the colloidal 
uranium makes up from 0.1 to 0.5 percent of the total uranium (one sample was measured at 6.5 
percent, but it was distant from the ore body where the total uranium was several orders of 
magnitude lower).

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Dissolved uranium concentrations at Nabarlek and Koongarra decline logarithmically to 
background with distance down gradient (three orders of magnitude over distances of 125m, 
Nabarlek, and 200m, Koongarra) (Short et al. 1988 [DIRS 113937]). Colloids down gradient 
were found to be more depleted in 234U than the solute; this was interpreted by Short et al. (1988 
[DIRS 113937]) as systematic leaching of uranium from the colloids. Payne et al. (1992 [DIRS 
124812]) estimated that the down-gradient uranium dispersion fan has developed over about two 
million years. 
The Cigar Lake uranium deposit in northern Saskatchewan was studied to evaluate analog 
features with respect to nuclear fuel disposal. Colloids (1450 nm) and suspended particles 
(greater than 450 nm) were measured from 501 groundwater samples. The groundwater has low 
ionic strength and pH values from 5.6 to 7.7 (Vilks et al. 1993 [DIRS 108261]). Particles ranged 
in size from 10 nm to about 20 m; concentrations of colloid-size particles were mostly 1 mg/L 
or less, although several samples up to 4 mg/L, and two samples up to 13 mg/L, were noted. 
Low-integrity rock and overburden yielded groundwater with the highest colloid concentrations. 
Colloid compositions were primarily clay minerals, X-ray-amorphous Fe-Si oxyhydroxides, 
quartz, and organic particles. The larger colloid-size fractions contain more iron than the smaller 
fractions. U concentrations associated with all particles analyzed (including particles larger than 
colloids) ranged from about 60 to 600 g/g. 
Vilks et al. (1993 [DIRS 108261]) conclude that colloid concentrations at Cigar Lake are 
sufficiently low that they would have little impact on radionuclide migration, as long as 
radionuclide attachment is reversible. In that regard, Vilks et al. report that while 230Th and 234U 
are in secular equilibrium in the host rock, dissolved 230Th/234U is very low, as is the ratio for 
230Th and 234U sorbed onto particles. This is interpreted as 230Th not having had time to reach 
secular equilibrium with its parent. Vilks et al. state further that if 230Th on particles has ingrown 
from 234U, and has not been sorbed from water, then the particles could be as much as 8,000 
years in age. 
6.3.1.3 Colloids from the Corrosion of Waste Package and Metallic Invert Materials 
The occurrence of iron oxyhydroxide colloids from the corrosion of waste package and metallic 
invert materials is included in the colloid model. Conceptually (and for purposes of estimating 
specific surface area and site density for irreversible sorption calculations; see Section 6.3.3.2) 
the iron oxyhydroxide colloids are likely to be comprised of three species, under the anticipated 
repository conditions: a-FeOOH (goethite), a-Fe2O3 (hematite), and Fe(OH)3nH2O (ferrihydrite, 
or hydrous ferric oxide) (Langmuir 1997 [DIRS 100051], p. 436-437). Goethite forms from 
hydrous ferric oxide by dissolution-reprecipitation, while hematite will form by direct solid-solid 
transformation (aging of hydrous ferric oxide) (Langmuir 1997 [DIRS 100051], p. 437). The 
iron oxyhydroxides will occur in three forms: immobile scale, large particles that will settle out, 
and colloid-sized particles. 
Maximum concentration values for colloids have been estimated based on experiments 
performed at the University of Nevada at Las Vegas (see below, this section) and on professional 
judgment. TSPA-LA model calculations of total quantities of corrosion products are based on 
known masses of metallic components. The iron oxyhydroxide phases may be expected to

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MDL-EBS-PA-000004 REV 00 48 June 2003 
provide abundant sorption sites for dissolved (aqueous) radionuclides in amounts determined by 
the appropriate Kd value (Section 6.3.3.1). Stable iron oxyhydroxide colloid suspensions may 
serve to increase the mobility of sorbed radionuclides (see Sections 6.3.2 and 6.3.3). Their 
stability is controlled by fluid conditions including ionic strength and pH. 
An ongoing DOE-funded research project at the University of Nevada at Las Vegas is currently 
evaluating the corrosion of scaled-down miniature waste packages exposed to groundwater 
similar to that found at Yucca Mountain. The miniature waste packages are composed of carbon 
steel and are scaled-down to approximately 1/70 the size of actual waste packages slated for 
disposal in the Yucca Mountain repository. Corrosion products released from the miniature 
waste packages were characterized by X-ray diffraction (DTN: MO0302UCC034JC.003 [DIRS 
162871]) and the quantity of corrosion products transported out of the waste packages was 
measured by micro-filtration (DTN: MO0212UCC034JC.002 [DIRS 161457]). 
Two configurations were used to introduce water into the miniature waste packages and induce 
corrosion: (1) a bath tub configuration in which water was introduced from the top of the 
miniature waste package and exits from an opening on the side of the miniature waste package 
after it has accumulated along the bottom, and (2) a flow through configuration in which water 
was introduced from the top of the miniature waste package and directly exits from the bottom. 
Water with chemical composition similar to Well J-13 (near Yucca Mountain) water was used in 
the experiments and the rate of water introduction was similar to projected rates of water 
movement within the drifts at Yucca Mountain. To establish the total amount of corrosion 
material transported out of the miniature waste packages, the effluent was passed through a 
micro-filtration system capable of separating particles of 0.1 micron and upward. Identification 
of the oxidation corrosion products is ongoing, although to date the data suggest a preponderance 
of cryptocrystalline corrosion products, including magnetite (Fe3O4), lepidocrocite (FeOOH), 
and goethite (FeOOH) (DTN: MO0302UCC034JC.003 [DIRS 162871]). 
The colloidal size fraction of these materials represent viable analogs for the nature and quantity 
of corrosion-generated iron oxide colloids that could potentially be produced and transported 
from the engineered barrier system early during the corrosion of the waste packages after 
breaching. The cumulative results of the miniature waste package corrosion tests to date have 
yielded average concentrations of colloidal size material in the range of 20 mg/L within the 
initial four weeks of the experiments (DTN: MO0212UCC034JC.002 [DIRS 161457]). The 
University of Nevada at Las Vegas researchers have observed that all the miniature waste 
packages have clogged after several weeks of water influx, probably due to the formation and 
accumulation of corrosion products (e.g., iron oxyhydroxide) of larger molar volume than the 
original materials prior to corrosion. 
Few data for iron oxyhydroxide colloid concentrations have been found in the scientific 
literature. Three studies reported groundwater colloid concentrations dominated by iron 
oxyhydroxide colloids, and the colloid concentrations reported varied greatly. Values ranging 
from 0.6 mg/L to 261 mg/L were measured in the vicinity of a mined uranium ore formation at 
Cigar Lake in Northern Saskatchewan (Vilks et al. 1993 [DIRS 108261]). Two Swedish 
groundwater colloid concentrations measurements were 0.02 mg/L and 0.043 mg/L for saline 
and none-saline groundwater samples, respectively (Laaksoharju et al. 1995 [DIRS 106449]).

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MDL-EBS-PA-000004 REV 00 49 June 2003 
Uncertainty in the data generated by the miniature waste package experiments and the 
consideration of iron oxyhydroxide colloid concentrations reported in the literature for 
groundwaters in iron-rich geologic environments is discussed in Section 6.6.2, Uncertainty 
Associated with the Model Analysis. 
6.3.1.4 Natural Colloids Originating from Unsaturated Zone Seepage Water/Groundwater 
Natural colloids occurring in seepage water/groundwater in the repository vicinity are modeled 
as smectite. Seepage water and colloids enter the drift and breached waste package. 
Three types of seepage water/groundwater colloids may be present at Yucca Mountain: 
1. Mineral fragments are generally hydrophobic, hard particles (i.e., particles that tend not 
to interact with water molecules) that are kinetically stabilized or destabilized by 
electrostatic forces and may consist of crystalline or amorphous solids (Kim 1994 [DIRS 
109521]). Steric coatings (i.e., coatings whose molecular topology may result in 
protuberances) may enhance the stability of mineral fragments by preventing close 
contact. Mineral fragments may act as substrates for sorption of radionuclides. 
2. Humic substances are generally hydrophilic particles (i.e., particles that tend to interact 
with water molecules) that are stabilized by solvation forces (i.e., the forces involved in 
particlewater molecule interactions, generally involving electrostatic and van der 
Waals forces). They can be powerful substrates for uptake of metal cations and are 
relatively small (less than 100,000 atomic mass units). 
3. Microbes are relatively large colloidal particles that are stabilized by hydrophilic coatings 
on their surfaces, which behave as steric stabilizing compounds. They may act as 
substrates for extracellular actinide sorption, or they may actively bioaccumulate 
radionuclides intracellularly. 
Clays, silica, hematite, and goethite colloids occur in groundwater in the vicinity of Yucca 
Mountain (cf. Kingston and Whitbeck 1991 [DIRS 113930]), and the colloid model calls for 
these colloids to enter a failed waste package and be available to interact with released 
radionuclides. The presence and potential influence of natural seepage water colloids on the 
formation of radionuclide-bearing colloids in the engineered barrier system are considered by 
modeling all seepage water colloids as smectite; these are referred to as groundwater colloids 
throughout this document. 
An assessment of the concentration of humic substances in groundwaters collected near the 
Yucca Mountain was conducted by Minai et al. (1992 [DIRS 100801]). In that study, humic 
substances were extracted from several thousand gallons of J-13 well water through a series of 
steps including acidification, purifying with ion exchange columns, and freeze drying. The 
humic substances that were collected were characterized with nuclear magnetic resonance and 
other spectroscopic techniques. Experiments were conducted to characterize site binding 
densities and complexation with Am. Results and supporting calculations indicated that the 
presence of humic substances in J-13 well water could affect oxidation speciation by reducing 
some radionuclide species. Considering the presence of calcium in J-13 well water, however, the 
authors estimated that the effective complexation capacity of humic substances is about

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MDL-EBS-PA-000004 REV 00 50 June 2003 
2.3 x 10-10 eq/L (equivalents per liter) at pH 6.9 and 2.7 x 10-11 eq/L at pH 8.2 (Minai et al. 1992 
[DIRS 100801], p. 199). Considering the very low complexation capacity of humic substances 
in this system, they are not included among the groundwater colloids considered in this 
abstraction. 
Because of the relatively large sizes of microbes (up to tens of microns), they are very 
susceptible to filtration in geologic media and, partly because of this microbe-radionuclide 
complexes, are not modeled in this abstraction. Discussion on the probable influences of 
microbes on the colloids that are considered in this analysis (inorganic waste form colloids, steel 
corrosion product colloids, and natural seepage water/groundwater colloids) is presented in 
Section 6.3.4. 
6.3.2 Colloid Stability and Concentration 
In order for radionuclide-bearing colloids to affect repository performance, the colloidal 
dispersion must be stable for the time frame of transport and must carry significant amounts of 
radionuclides. Transport times can range from days/months/years for transport out of a failed 
waste package under a large seep, to hundreds of thousands of years for retarded transport to the 
accessible environment. Thus, some relatively unstable colloids generated at the waste form 
may persist long enough to be transported out of the waste package, increasing the radionuclide 
release from the waste package, but likely would not travel a significant distance away from the 
repository. The more stable colloids, however, may remain suspended for years and travel a 
much greater distance. The clay colloids observed in the defense high-level waste glass and to a 
limited extent in the SNF corrosion tests are reasonably considered to have similar stability 
characteristics as natural clay colloids because the waste form-derived clays exhibit similar 
crystallographic and chemical properties as natural clays (CRWMS M&O 2001 [DIRS 154071]). 
The iron oxyhydroxide colloids stipulated to form from internal corrosion of the waste package 
are similarly considered as analogous to natural iron oxyhydroxide colloids. Uranium-phase 
colloids generated in the commercial SNF and DOE SNF tests are probably not as stable or 
persistent, as suggested by test results and field observations near uranium deposits (see Section 
6.3.1.2.4). 
6.3.2.1 DLVO Theory and Surface Complexation 
Basic principlesThe surfaces of dispersed, stable colloids have an electric charge sufficient to 
maintain the particles separation by mutual repulsion. The surface charge of a particle can have 
two general causes: (1) specific characteristics of the crystal structure (see below) and 
(2) preferential adsorption of specific ions onto the surface (van Olphen 1977 [DIRS 114428], p. 
18). The surface charges are compensated by the attraction of counter-ions, which have the 
opposite charge to the surface charges and to the vicinity of the particle surface. The charges at 
the particle surface and the oppositely charged, closely associated counter-ions make up the 
electric double layer (van Olphen 1977 [DIRS 114428], p. 18). The counter-ions are 
electrostatically attracted to the oppositely charged surface. However, they tend in water to 
diffuse away from the surface along a decreasing concentration gradient. As a result, counterions 
develop an atmosphere around the colloid that decreases in concentration away from the 
particle (van Olphen 1977 [DIRS 114428], p. 30).

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There are three causes of surface charge related to sheet-silicate crystal structure (Langmuir 1997 
[DIRS 100051], pp. 346 to 347): (1) isomorphous substitution in the crystal lattice (e.g., Al3+ for 
Si4+ in the tetrahedral layer and Mg2+ for Al3+ in the octahedral layer resulting in an excess of O2- 
bonds, the chief cause of negative surface charge in smectites); (2) lattice imperfections or 
defects (e.g., deficits in octahedral Al3+ or interlayer K+ causing a net negative surface charge, 
also important for smectites); and (3) broken or unsatisfied bonds (e.g., at crystal plate corners 
and edges usually resulting in a net negative surface charge due to exposed O2- and OH-, 
important for smectites). As clay particles decrease in size, the importance of broken bonds 
increases (Langmuir 1997, p. 346 [DIRS 100051]). 
The surface charge of oxides, hydroxides, phosphates, and carbonates originates chiefly from 
ionization of surface groups or surface chemical reactions (Langmuir 1997 [DIRS 100051], p. 
349). Surface charge among this group is strongly dependent upon pH, being positive at lower 
pH and negative at higher pH. For example, in oxides and hydroxides, this is due largely to the 
adsorption of H+ at lower pH and OH- at higher pH. The pH at which the net surface charge is 
neutral is called the zero point of charge; if the change in charge is solely due to adsorption of H+ 
or OH- ions, the pH at neutrality is called the point of zero net proton charge (Langmuir 1997 
[DIRS 100051], p. 350). 
Far from the zero point of charge or point of zero net proton charge, the surface-charge density is 
relatively high; the particles are mutually repelled, and the suspension is stable. At or near the 
zero point of charge or point of zero net proton charge the repulsion force decreases to near zero, 
and the particles are more likely to agglomerate (stick) when particle collisions occur. 
The stability and the coagulation, or agglomeration, of colloids is controlled by electrostatic and 
chemical processes at the colloid surfaces. In the 1940s and 1950s, research on particle 
coagulation centered around the electrostatic properties of the particles wherein the Derjaguin 
and Landau, and Verwey and Overbeek theory (DLVO) of the particle electrical double layer 
was used to explain particle stability in terms of surface charge and potential, the ionic strength 
of solutions, and the van der Waals forces between particles (Liang and Morgan 1990 [DIRS 
109524], p. 33). It was subsequently realized that the double-layer theory by itself was not 
complete, and that the origin of surface charges and the role of specific chemical interactions in 
the stabilization and destabilization of colloidal particles should be considered. At low surface 
potential and low surface charge density of particles, experiments to verify DLVO theory agreed 
with theoretical prediction. However, at high surface potential and charge density, due to the 
large repulsive forces of the particles, the theory predicted orders of magnitude higher stability 
ratios than were observed (Liang and Morgan 1990 [DIRS 109524], p. 34). Beginning in the 
1970s, surface complexation adsorption models were developed (Langmuir 1997 [DIRS 
125369], p. 771]; these models were used to analyze changes in particles surface potential and 
charge brought about by complexation reactions (described by mass law equations) at the 
particle surface involving specific adsorbed chemical species (Dzombak and Morel 1987 [DIRS 
109505], p. 430; Liang and Morgan 1990, p. 34 [DIRS 109524]).

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TemperatureTemperature effects have also been shown to influence the stability of colloids 
(Langmuir 1997 [DIRS 100051], p. 439). The rate of particle coagulation is described by the 
stability ratio, W, defined as: 
kT 
W Vmax exp = (Eq. 2) 
where 
Vmax = height of free-energy barrier preventing particle coagulation 
. = Boltzmann constant 
T = temperature in K 
When log W  0, coagulation is rapid and colloids settle out of the liquid media. Inspection of W 
shows that when T increases, W decreases. Therefore, increased temperature causes a colloid 
suspension to become less stable. Conversely, decreasing temperature will result in an increase 
in the stability of a suspension formed at a higher temperature. For the purposes of this 
abstraction, temperature effects are ignored, and it is assumed that waste form colloids produced 
at 90C are stable at 25C (Section 5, Assumption 5.4). The net effect of this assumption on 
TSPA-LA is that colloids formed at the higher temperatures remain stable as the repository 
cools. 
Ionic strengthIn nearly pure water, dissolved ions are likely to contact only other water 
molecules. As the concentrations of the ions increase, the ions are likely to come in contact with 
one another. The interactions between and among the ions is proportional to their charge, as 
reflected in the definition of ionic strength: 
I =  S (mi zi
2) (Eq. 3) 
where I (and m) is in molal units and zi is the charge of ion i (e.g., Langmuir 1997 [DIRS 
100051]). 
According to DLVO theory, colloids become unstable as ionic strength in a solution increases 
due to compression of the diffuse counter-ion atmosphere and decreases in surface potential, i.e., 
decreases in repulsive forces. Further, the degree of compression of the electric double layer is 
dependent on the concentration and valence of ions of opposite sign from that of the surface 
charge (van Olphen 1977 [DIRS 114428], p. 34). The effect of valence is captured by the 
Schulze-Hardy rule, which incorporates the principle that for a given counter-ion concentration, 
the higher the valence of the counter-ions, the more unstable the colloids and the greater the 
tendency to flocculate (van Olphen 1977, p. 24) [DIRS 114428].

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Critical Coagulation ConcentrationCritical coagulation concentration is defined as the 
minimum concentration of an electrolyte that results in the flocculation (coagulation) of a 
colloidal suspension. In his treatise on clay colloidal dispersions, van Olphen (1977 p. 24) 
[DIRS 114428] summarized empirically determined critical coagulation concentration values as 
follows: 
Counterion Valence Critical Coagulation Concentration (M) 
1 25,000 to 150,000 
2 500 to 2000 
3 10 to 100 
At pH values below the pHZPC for a mineral, the negatively charged counterions are important; 
above the pHZPC, positively charged counterions are important (see Basic Principles, this 
section). 
For comparison, concentrations of counterions in J-13 well water were reported in a previous 
report (CRWMS M&O 2000 [DIRS 111880], Table 2, p. 16) as follows: 
Ion Valence Concentration (M) 
Na +1 1990 
K +1 129 
Ca +2 324 
Mg +2 82.7 
Al +3 0.0255 
Cl -1 201 
S (sulfate) -2 192 
Note that none of the concentrations of individual ions in J-13 well water exceeds van Olphens 
empirical critical coagulation concentration values (although Ca2+ is close) nor does the sum of 
the concentrations. The conclusion then is that colloid dispersions will probably be stable in J-13 
water, as well as water compositions whose cation and anion concentrations remain below the 
valence-determined critical coagulation concentrations. 
6.3.2.2 Stability of Smectite Colloids as a Function of pH and Ionic Strength 
The zero point of charge of smectite is approximately pH 2 (see Figure 4). Since a pH this low is 
not anticipated in the repository, it is reasonable to expect that smectite colloids will remain in a 
stable pH range much of the time under anticipated repository conditions (unless ionic strength 
exceeds a certain threshold). However, it should be recognized that with decreasing pH, the 
charge density of smectite particle surfaces will decrease as more and more H+ sorb to the 
surface and offset negative charges, generally decreasing stability (Buck and Bates 1999 [DIRS 
109494]; Tombacz et al. 1990 [DIRS 112690]). 
The defense high-level waste glass tests conducted at Argonne National Laboratory resulted in 
measured pH ranging between approximately 9 and 11.5 (Buck and Bates 1999 [DIRS 109494])

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MDL-EBS-PA-000004 REV 00 54 June 2003 
which is part of the range at which smectite colloids exhibit the highest surface charge and, 
hence, are most stable. Tombacz et al. (1990) [DIRS 112690] investigated the stability of 
smectite (referred to as montmorillonite by Tombacz et al.) suspensions as a function of pH and 
ionic strength in an NaCl solution. It was found that suspensions became unstable and 
flocculated at pH 2, 4, and 8 in 0.01 M, 0.025 M, and 0.04 M NaCl solutions, respectively 
(Figure 4). Figure 5 illustrates the abstraction and extension of this data to pH 10 and ionic 
strength of 0.05M for use in the TSPA-LA calculations. Schematic representation was abstracted 
from data presented in Figure 4. The established relationship between ionic strength and 
smectite colloid stability (STcoll, wf, pH) as a function of pH for use in the TSPA-LA model is 
shown in Figure 5. 
Ionic Strength (NaCl) 
2 6 8 10 
zpc 
pH 
0.01 
0.02 
4 
0.03 
0.04 
0.05 
MONTMORILLONITE 
UNSTABLE 
MONTMORILLONITE 
STABLE 
NOTE: Data points represent combinations of ionic strength and pH at which montmorillonite 
stability is significantly decreased. 
Source: Adapted from Tombacz et al. 1990 [DIRS 112690]. 
Figure 4. Experimental Determination of Montmorillonite (i.e., Smectite) Stability as a Function of pH 
and Ionic Strength

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MDL-EBS-PA-000004 REV 00 55 June 2003 
Figure 5. Schematic Representation of Smectite Stability as a Function of pH and Ionic Strength 
6.3.2.3 Stability and Concentration of Iron Oxyhydroxide Colloids as a Function of pH 
and Ionic Strength 
The point of zero net proton charge of iron oxyhydroxide colloids ranges between approximately 
pH 5 and 8.5 (cf., Langmuir 1997 [DIRS 100051], p. 351, Table 10.3), depending on colloid and 
water composition, and in this range they will tend to be unstable and tend to agglomerate. At 
higher or lower pH, however, iron oxyhydroxide colloids are stable, depending upon ionic 
strength. Liang and Morgan (1990 [DIRS 109524]) demonstrated that for a given ionic strength 
iron oxyhydroxide stability increases as pH both increases and decreases away from the zero 
point of charge (Figure 6). In general the higher the ionic strength, the wider the pH range about 
the zero point of charge that iron oxyhydroxide is unstable. For example, at an ionic strength of 
0.05 M, iron oxyhydroxide is unstable between approximately pH 6 and 11. The pH of zero 
proton condition for hematite is indicated in Figure 6 (i.e., pH 8.5). Dashed lines are drawn 
through the specific experimental points as a guide. The solid line represents a DLVO model 
calculation for ionic strength 0.05 M. Note that Wexp represents the stability of the dispersion, in 
terms of the rate at which colloidal particles in the dispersion agglomerate (see Equation 2, 
Section 6.3.2.1, DLVO Theory and Surface Complexation). A high value represents a stable 
dispersion and a value of zero indicates rapid agglomeration. At ionic strengths of about 0.05 m 
or more, the stability ratio is very low between pH values of about 6 and 11. A relatively low log 
Wexp of approximately 0.2 was selected for abstraction of pH and ionic strength data for use in 
Figure 7.

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MDL-EBS-PA-000004 REV 00 56 June 2003 
Source: Langmuir 1997 [DIRS 100051]. 
Figure 6. Experimentally Derived Stability Ratio, Wexp, of a Hematite Suspension Plotted as a Function 
of pH for Differing Ionic Strengths 
As described in Section 6.3.1.3, it is stipulated for modeling purposes that iron will corrode and 
form iron oxyhydroxides. It is further stipulated that the iron oxyhydroxides will occur as 
immobile scale, large particles that will settle out, and colloid-sized particles. (For modeling 
purposes two parameters are established, the expected maximum and minimum mass 
concentrations of iron oxyhydroxide colloids, Mcoll,FeOx,sampled and Mcoll,FeOx,min, respectively.) 
The University of Nevada at Las Vegas research (see Section 6.3.1.3) on miniature waste 
packages has shown that corrosion proceeds rapidly, and colloid-sized particles have been 
observed to leave the miniature waste package in concentrations of around 20 mg/L. The release 
is more or less continuous until it decreases and the aperture clogs with corrosion products. 
While it was not observed in the University of Nevada at Las Vegas experiments, it is possible 
that in a repository setting clogging material may become dislodged by an event or changed 
condition, and release could resume, the overall process possibly occurring more than once. 
Accordingly, the mass concentration range was chosen to include the 20 mg/L, and to allow for 
releases dwindling to a low quantity (0.05 mg/L), as well as for a pulse-like release (up to 50 
mg/L). This maximum value is well within the range of colloid concentrations observed 
experimentally and in natural groundwater (see, for example, Lu et al. 2000 [DIRS 154422], who 
performed experiments with colloid concentrations of up to 200 mg/L; and Honeyman and 
Ranville 2002 [DIRS 161657], who acknowledge colloid concentrations in groundwater 
occasionally in excess of 100 mg/L).

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The distribution was chosen to emphasize the upper end of the range, i.e., the 5 to 50 mg/L 
portion, to reflect the steady state conditions and pulses, but also allow for occasional clogging 
of the aperture in the waste package. The emphasis of the upper end of the range is conservative 
as it tends toward predicting higher colloid concentrations to which dissolved radionuclides may 
sorb. 
This distribution is valid for ionic strengths less than 0.05 M. The colloid mass concentration at 
ionic strengths greater than 0.05 M is stipulated to be 1 x 10-3 mg/L, representing a very small 
non-zero number for modeling purposes. This concentration value is between one and two orders 
of magnitude lower than the lower bound of the distribution used for ionic strengths less than 
0.05 M. This value is reasonable based on experimental observations that have shown a very 
low stability ratio. This very low stability ratio essentially implies complete agglomeration of 
colloids at ionic strengths exceeding 0.05 M (Liang and Morgan 1990 [DIRS 109524]. 
Therefore the use of a non-zero value for colloid concentration above ionic strength 0.05 M is 
conservative. 
NOTE: Schematic representation (used in abstraction) of iron oxyhydroxide colloid stability as a 
function of ionic strength and pH. At and near the zero point of charge colloids are unstable, 
even at low ionic strengths. At higher ionic strengths the pH range at which colloids are 
unstable is greater. Above ionic strength 0.05 colloids are assumed to be unstable for all pH 
Source: Abstracted from Liang and Morgan 1990, [DIRS 109524], Figure 1. 
Figure 7. Schematic Representation of Iron Oxyhydroxide Colloid Stability as a Function of pH and Ionic 
Strength 
6.3.2.4 Stability and Concentration of Waste Form Colloids 
Colloids were formed in the course of static defense high-level waste glass tests on several of the 
glasses for different SA/V. It was observed that as the ionic strength increased, colloid 
concentration generally decreased, and ultimately a threshold value was reached above which the 
colloids were not observed or were observed in very low quantities (Figure 8). As this threshold 
6 8 9 11 
zpc 
pH 
0.01 
0.05 
Ionic Strength 
iron oxyhydroxide colloid 
zone of instability 
I = -0.02 pH + 0.17 
I = 0.02 pH - 0.17

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MDL-EBS-PA-000004 REV 00 58 June 2003 
was approached, it was also observed for one glass that the colloid size increased significantly 
due to aggregation of the colloids. The threshold at which flocculation occurred was 
approximately I = 0.05m. During the drip tests, ionic strength remained below this value, and 
colloids were stable throughout the tests. 
0E+0 
2E-8 
4E-8 
6E-8 
8E-8
0.000 0.020 0.040 0.060 0.080 0.100 
Relative Ionic Strength (mol/kg) 
[Pucolloids] (M) 
202A_2K 
202A_20K 
131A_2K 
131A_20K 
NOTE: Plutonium-bearing colloids as a function of ionic strength for corrosion tests on glass samples SRL 
202A and SRL 131A at SA/V or 2,000 and 20,000/m (at 90C) 
Source: Figure 8 in CRWMS M&O 2001 [DIRS 154071]; DTNs: LL000905312241.018 [DIRS 152621], 
p. 71; LL991109751021.094 (DIRS 142910], p. 30. 
Figure 8. Concentrations of Pu and Colloids as a Function of Ionic Strength in Corrosion Tests 
The stability of smectite colloids (including smectite colloids formed from defense high-level 
waste glass degradation) is determined primarily by ionic strength, but also to an extent by pH, 
as described in Section 6.3.2.2 and shown in Figures 4 and 5. The concentration of total colloidassociated 
radionuclides in the pH range 2 to 10 is determined by bounding the data shown in 
Figure 9 as follows: 
For 0.01 <I <0.05, [Pu colloid] = -2.50E-6  I +1.25E-7, for .01 <I <.05 (Eq. 4) 
This relationship is valid for ionic strengths greater than 0.01 M and less than 0.05 M. The 
concentration at ionic strengths greater than 0.05 M is stipulated to be 1 x 10-11 M, representing a 
very small non-zero number for modeling purposes (Figure 9). This concentration value is 
approximately three orders of magnitude lower than the lowest value modeled at ionic strengths 
less than 0.05 and is reasonable based on experimental observations that have shown complete 
agglomeration of colloids at ionic strengths exceeding 0.05M (CRWMS M&O 2001 [DIRS 
154071], Section 6.2.1). At ionic strengths less than 0.01 M, the Pu concentration is modeled as 
1 x 10-7 M, also based on experimental observations (Figure 9). 
Am concentration is based on Pu concentration. It is determined by multiplying the calculated 
Pu concentration by the ratio of Am to Pu in the radionuclide inventory of the defense high-level 
waste glass at each TSPA-LA calculation time step. 
Cpu,coll (M)

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MDL-EBS-PA-000004 REV 00 59 June 2003 
NOTE: Schematic relationship (used in abstraction) between Pu concentration embedded in defense 
high-level waste glass and ionic strength. The function represents the bound of the defense 
high-level waste glass corrosion experimental data (see Figure 8); the maximum value 
represented, 1 x 10-7, bounds the maximum concentration of colloids observed in the defense 
high-level waste glass experiments. (The straight line representing the relationship should 
actually be portrayed with a slight curve, concave downward.) The low value, 1 x 10-11, 
represents the steep decline in colloid concentration above ionic strength 0.05 M. 
Figure 9. Schematic Relationship Between Pu Concentration in Defense High-Level Waste Glass 
Colloids and Ionic Strength 
6.3.2.5 Stability and Concentration of Seepage Water Colloids 
Colloids are thought to exist naturally in groundwater in all subsurface environments with the 
composition and concentration of colloids being site specific and determined by the geologic 
nature of the subsurface. Transport of radionuclides by groundwater colloids is a potentially 
important transport mechanism and is thought to be generally more prevalent than transport by 
true colloids (McCarthy and Zachara 1989 [DIRS 100778]). It is important to note here that 
waters and associated colloids potentially coming in contact with repository waste will originate 
at the ground surface as precipitation. These waters will move downward through the soils, 
regolith, and tuff materials overlying the repository before coming in contact with the wastes. 
Groundwater samples extracted from the underlying saturated zone in the vicinity of Yucca 
Mountain are used as surrogates for these waters. 
1 x 10-11 
1 x 10-7 
1 x 10-8 
1 x 10-9 
1 x 10-10 
0.00 0.01 0.02 0.03 0.04 0.05 0.06 
Ionic Strength (M) 
CPu, coll (M) 
CPu = function (STcoll, wf, is) 
Colloid Zone 
of Instability 

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MDL-EBS-PA-000004 REV 00 60 June 2003 
McCarthy and Degueldre (1993 [DIRS 108215]) and Degueldre et al. (2000 [DIRS 153651]) 
have characterized the colloids from groundwaters sampled at various locations around the world 
from crystalline and sedimentary rocks in saturated and unsaturated hydrologic regimes. They 
showed that the colloid concentration and stability is dependent, among other things, upon pH, 
redox potential, ionic strength (including relative concentrations of the major cations Na, K, Ca, 
and Mg), counterion valence, and organic carbon; these factors were studied in the investigation. 
The results indicate that, in general, colloids tend to be stable if the concentration of alkalis (Na 
and K) is below approximately 10-2 M and if alkali-earth elements (Ca and Mg) are below 
approximately 10-4 M (Figure 10). This provides a guideline for assessing colloid stability and 
allows for very rough estimation of concentration. Whereas the DLVO calculations provide 
useful inferences on mechanisms of colloid destabilization, these empirical observations are 
more useful in developing approaches to performance assessment calculations. 
NOTE: Here, concentrations of colloids are compared on the basis of alkali and alkaline-earth element 
concentration for colloid size greater than 100 nm. 
Source: Degueldre et al. 2000 [DIRS 153651]. 
Figure 10. Colloid Concentrations Versus Alkali and Alkaline-Earth Concentration for Groundwaters from 
Around the World 
Colloid concentration is difficult to correlate precisely with ionic strength because there are other 
factors that can significantly affect concentration, such as pH. As described above, for example, 
at a pH of around 8, some iron oxyhydroxide colloids would have a zero net surface charge 
(since their zero point of charge is approximately 8) resulting in elimination of mutual repulsive 
forces and the tendency to flocculate, even if the ionic strength were very low. (This is an 
exampleonly smectite colloids are modeled as representative of natural seepage 
water/groundwater colloids.)

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MDL-EBS-PA-000004 REV 00 61 June 2003 
Further, site-specific studies of groundwater colloids (e.g., Kingston and Whitbeck 1991 [DIRS 
113930]; Degueldre et al. 2000 [DIRS 153651]) suggest that when groundwater conditions favor 
colloid stability, there may be a very wide range of colloid concentrations observed for a narrow 
range of groundwater chemistry. 
Consideration of the recently acquired data from the Yucca Mountain area and the Nevada Test 
Site by Los Alamos National Laboratory confirms a highly variable colloid concentration over a 
relatively narrow range of ionic strength. Figure 11 plots the groundwater colloid concentrations 
in water samples collected in the vicinity of Yucca Mountain. Data sources included in the 
figure are: 
Groundwater colloid populationsDTNs: LA0002SK831352.001 [DIRS 149232] 
LA0002SK831352.002 [DIRS 149194], LA0002SK831352.004 [DIRS 161579], 
LA9910SK831341.005 [DIRS 144991], LA0211SK831352.001 [DIRS 161580], 
LA0211SK831352.002 [DIRS 161581], LA0211SK831352.003 [DIRS 161582], 
LA0211SK831352.004 [DIRS 161458], LA0002SK831352.003 [DIRS 161771]) and 
colloid concentrations in groundwaters sampled around the world Degueldre et al. (2000 
[DIRS 153651]) and DTN: SNT05080598002.001 [DIRS 162744] data. 
Ionic Strength dataDTNs: SNT05080598002.001 [DIRS 162744], LA0304PR831232.001 
[DIRS 163196], and LA0304PR831232.002 [DIRS 163197]. 
It is important to note here that the groundwater colloid samples analyzed by Los Alamos 
National Laboratory represent colloid particle size distributions from 50 nm to 200 nm in 
diameter while the data from groundwaters around the world (DTN: SNT05080598002.001 
[DIRS 162744]) represent colloid particle size distributions from 100 nm to 1000 nm (1.0 m 
diameter). Evaluation of the colloid populations in the various size fraction classes for each 
groundwater sample did not reveal a systematic increase in the number of particles with 
decreasing particle size class (see Table I-2). Therefore, inclusion of particle size classes smaller 
than 50 nm should not result in a substantially greater mass concentration in the water sample, 
especially since the smaller particles would have exponentially lower masstherefore, omission 
of the less than 50 nm particle-sized fraction in the mass concentration calculations is reasonable.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 62 June 2003 
NOTE: Degueldre data (DTN: SNT05080598002.001 [DIRS 162744]) has a greater range in ionic strength 
than waters in the vicinity of Yucca Mountain. 
Figure 11. Groundwater Colloid Concentration Data Collected in the Vicinity of Yucca Mountain 
Compared with Data Collected from Groundwaters Around the World (the ordinate values are 
in particles per milliliter) 
Colloid particle number data (pt/ml) for groundwater samples from the Yucca Mountain area and 
Idaho National Engineering and Environmental Laboratory were converted to mass 
concentrations (mg/L) (Attachment I). It is important to note here that the Degueldre et al. (2000 
[DIRS 153651]) and DTN: SNT05080598002.001 [DIRS 162744] data were not used to 
calculate the mass colloid concentrations (mg/L) and were only used to establish the generally 
weak relationship between ionic strength and colloid populations in groundwaters around the 
world and specifically in the Yucca Mountain area (Figure 11). 
The groundwater colloid data from the vicinity of Yucca Mountain and Idaho National 
Engineering and Environmental Laboratory were pooled, and a discrete cumulative distribution 
function was established to evaluate the uncertainty in colloid concentration distribution. The 
colloid concentrations data included qualified data (i.e., LA0002SK831352.001 [DIRS 149232], 
LA0002SK831352.002 [DIRS 149194], LA9910SK831341.005 [DIRS 144991], 
LA0211SK831352.001 [DIRS 161580], LA0211SK831352.002 [DIRS 161581], 
LA0211SK831352.003 [DIRS 161582], and LA0211SK831352.004 [DIRS 161458]) used as 
direct input, and LA0002SK831352.003 [DIRS 161771] and LA0002SK831352.004 [DIRS 
161579] used as corroborating/supporting data. Inclusion of the Idaho National Engineering and 
Environmental Laboratory groundwater colloid data (LA0002SK831352.003) [DIRS 161771] 
was deemed appropriate for inclusion in the data analysis as corroborative data even though 
these groundwater colloid data are not from the vicinity of Yucca Mountain (see Attachment I). 
Water samples that had been filtered were not considered in the development of the uncertainty 
distribution. Since the colloid particles were measured by dynamic light scattering techniques, 
any potential error in measurement of colloid populations for the various particle size classes due 
to filter ripening (i.e., clogging of filter pores through time during the filtration process) was 
avoided by using only non-filtered sample data. 
Colloid Populations in Groundwater 
1.0E+04 
1.0E+05 
1.0E+06 
1.0E+07 
1.0E+08 
1.0E+09 
1.0E+10 
1.0E+11 
0.000 0.001 0.010 0.100 
Ionic Strength (M) 
pt/mL 
Yucca Mtn Data 
Collected by LANL 
Degueldre et al. 
2000

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MDL-EBS-PA-000004 REV 00 63 June 2003 
The data shown in Figure 12 reflect observed variability in groundwater colloid concentrations. 
The goal of the uncertainty distribution for groundwater colloid concentrations is to numerically 
capture our knowledge about uncertainty on a large scale. Based on the groundwater colloid 
concentration collected at the two sites (Yucca Mountain and Idaho National Engineering and 
Environmental Laboratory) and the large uncertainty associated with the collection of 
groundwater colloids, a reasonable representation of the uncertainty is shown in the discrete 
cumulative distribution function shown in Figure 12 (see Table 5 for the probabilities associated 
with the discrete cumulative distribution function). Major factors that contribute to uncertainty 
in the collection of groundwater colloids include (1) collection techniques, (2) differences in 
pumping rates at each well, and (3) unknowns factors including the types of additives introduced 
in the wells during the drilling process itself. 
The waste form and engineered barrier system components of the TSPA-LA analyses implement 
the uncertainty shown in Figure 12 only for ionic strength less than 0.05 M. For ionic strengths 
greater than or equal to 0.05 M, colloids are assumed to be unstable, based upon experimental 
work that has shown the flocculation of colloids at high ionic strengths (Liang and Morgan 1990 
[DIRS 109524]; Tombacz et al. 1990 [DIRS 112690]; CRWMS M&O 2001 [DIRS 154071]), 
and a single low value (1 x 10-6 mg/L) is used in the waste form and engineered barrier system 
analysis to represent minimum, non-zero colloid concentration. 
0 
0.2 
0.4 
0.6 
0.8 
1 
1.2
0.00 0.01 0.10 1.00 10.0 100.0 1000.0 
Concentration of Colloids 
Probability 
Technical Information 
(non-Q) 
Uncertainty Distribution 
Direct Input (Q) 
Figure 12. Cumulative Distribution Function Showing the Probability of Occurrence of Colloid 
Concentration Levels in Groundwater Samples in the Yucca Mountain Area and Idaho 
National Engineering and Environmental Laboratory

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MDL-EBS-PA-000004 REV 00 64 June 2003 
Table 5. Uncertainty Distribution for Groundwater Colloid Concentrations for the Total System 
Performance AssessmentLicense Application Analyses Based on Ionic Strength (I) of the 
Water Sample 
Ionic Strength 
(I) 
Groundwater Colloid 
Concentration (mg/L) 
Probability of 
Occurrence 
0.001 to 0.1 50 
0.1 to 1.0 25 
1.0 to 10 15 
10 to 50 8 
I < 0.05 M 
50 to 200 2 
I =0.05 M 1  10-6 100 
Review of the colloid data in Attachment I reveals that the largest proportion of groundwater 
colloid samples had colloid concentration populations between 0.001 and 0.1 mg/L and thus the 
values between these concentrations are modeled as having a sampling probability of 50 percent 
if the ionic strength of the solution is less than 0.05 M. Colloid concentration values of 0.1 to 10 
mg/L indicate a reasonable probability of occurrence of 40 percent. To account for colloid 
concentrations between 10 mg/L and 50 mg/L a probability of 8 percent was included. Some of 
the corroborative (non-Q) data included values as high as 171 to 200 mg/L (see Table I-1, 
Attachment I), but the uncertainty distribution for the pooled data indicates that these values 
have a low probability of occurring. Honeyman and Ranville (2002 [DIRS 161657]) point out 
that although most systems of interest for radioactive waste disposal exhibit relatively low 
colloid concentrations (less than 10 mg/L), concentrations exceeding 100 mg/L are not 
uncommonly reported. Therefore, it is recommended that the concentration values between 
50 mg/L and 200 mg/L be assigned only a sampling probability of 2 percent when the ionic 
strength of the solution is less than 0.05 M within the waste form and engineered barrier system 
components of the TSPA-LA model calculations. 
6.3.3 Radionuclide Sorption to Colloids 
A description of radionuclide sorption to colloids is presented in this section. Nonradioactive 
colloids are only important to repository performance insofar as radionuclides sorb to them. 
Sorption as used here is a general term that is governed by: (1) electrostatic forces, (2) ion 
exchange, (3) surface reaction, and (4) co-precipitation. Sorption may occur by a number of 
mechanisms and may be considered reversible or irreversible in the time frame of transport. The 
rate of sorption, desorption, and transport determine the effective reversibility of the sorption. 
When sorption is fast and reversible, transport on colloids will be controlled by local 
equilibrium, and simple models, e.g., linear isotherm models, using effective distribution 
coefficients reasonably describe the radionuclide behavior. When sorption is irreversible or 
desorption is slow relative to transport times, then local equilibrium models may fail, resulting in 
over- or under-predictions of transport. 
6.3.3.1 Reversible Sorption 
Perhaps the most common approach used in assessment of contaminant-rock interactions in the 
subsurface is the linear isotherm, or Kd value (distribution coefficient) approach, based on results

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MDL-EBS-PA-000004 REV 00 65 June 2003 
of batch sorption experiments. The linear isotherm model relationship is defined as follows 
(Langmuir 1997 [DIRS 100051]): 
S = Kd C (Eq.5) 
where 
S = mass of a solute adsorbed on a unit mass of solid 
Kd = distribution coefficient (mass-based, e.g., mL/g) 
C = concentration of the adsorbing solute in solution 
The amount of solute adsorbed on a solid can also be defined on the basis of area as follows: 
S = Ka C (Eq. 6) 
where 
S = mass of a solute adsorbed on a unit area of solid 
Ka = distribution coefficient (area-based, e.g., m2/g) 
C = concentration of the adsorbing solute in solution 
Three critical conditions must be met for this relationship to be applicable. First, the watercontaminant-
rock system must be in thermodynamic equilibrium, i.e., sorption must be 
completely reversible. Second, contaminant uptake must scale linearly with contaminant 
concentration. Third, the presence of other solutes in the system cannot affect the sorption. 
Because of the nature of the formation of waste form colloids and the interactions of some 
radionuclides, particularly some actinides, with mineral surfaces, certain conditions of the linear 
isotherm model are not met, and other approaches must be taken, as described below. 
A large quantity of data exist in published literature for sorption, and, in the past several decades, 
increasing attention has been given to understanding the mechanisms of sorption. In this section, 
the development of Kd values for uptake of strontium (Sr), cesium (Cs), thorium (Th), uranium 
(U), protactinium (Pa), neptunium (Np), plutonium (Pu), and americium (Am) on colloids is 
described, with caveats. These radionuclide elements were chosen for consideration because 
they are considered to be important to dose (BSC 2001 [DIRS 154841]), and significant 
uncertainty surrounds their potential behavior as pseudocolloids. 
The radionuclides considered for reversible sorption, and the rationale for their selection, are 
listed below. Characteristics of the radionuclides considered were a combination of long 
half-life, relatively strong sorption characteristics, relatively large abundance during the initial 
10,000 years in the repository, and observed field and laboratory behavior. 
 Plutonium. A large quantity of Pu will exist in the repository. Pu is sparingly soluble but 
sorbs strongly to oxide mineral surfaces (generally less strongly to silicates). The 
formation of pseudocolloids through the sorption of Pu particularly to iron oxyhydroxide 
colloids from corrosion of steel in the repository would increase the effective mobility of

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MDL-EBS-PA-000004 REV 00 66 June 2003 
Pu. Pu is observed to sorb strongly to soil minerals, and laboratory investigations have 
shown that it sorbs readily to colloids as well. 
 Americium. Am will be a significant contributor to radioactivity during the first 10,000 
years. As is Pu, Am is sparingly soluble but sorbs strongly to mineral surfaces, including 
colloids. Laboratory investigations have shown that it sorbs strongly to colloids. 
 Cesium. 135Cs has a long half-life and can attach strongly to certain sheet silicates 
(including clays) by means of ion exchange. For this reason Cs has been observed to 
sorb to soil minerals, and it could potentially form pseudocolloids particularly with 
groundwater and defense high-level waste glass-derived clay colloids. 
 Protactinium. Pa will be a significant contributor to radioactivity during the first 
10,000 years. Because of this, and the fact that relatively little is known of the colloidrelated 
behavior of Pa, it was included in this analysis. 
 Thorium. Th will be a significant contributor to radioactivity during the first 
10,000 years. Because of this, and the fact that there is evidence that Th sorbs strongly to 
oxides, it was included in this analysis. There is relatively little known of the 
colloid-related behavior of Th. 
 Neptunium. Because Np will be the most significant contributor to radioactivity beyond 
the first 10,000 years, it was considered for inclusion in this analysis. Np is more soluble 
under anticipated repository conditions than many of the other important radionuclides, 
and it sorbs considerably less strongly than, for example, Pu and Am. It would appear 
then that the mobility of Np is influenced most by its solubility. For these reasons, and to 
simplify the modeling, Np was not included in the reversible-sorption portion of the 
colloid-associated radionuclide transport analysis. 
 Uranium. U will be by far the most abundant radioactive element in the repository and 
primarily for this reason was considered for the analysis. U is more soluble under 
anticipated repository conditions than many of the other important radionuclides, and it 
sorbs considerably less strongly than, for example, Pu and Am. As with Np, the mobility 
of U is influenced most by its solubility. Further, field observations at U deposits and 
mine sites have indicated that little or no colloid-associated U transport occurs 
(Section 6.3.1.2.4). For these reasons, and to simplify modeling, U was not included in 
the reversible-sorption portion of the colloid-associated radionuclide transport analysis. 
 Strontium. Sr is expected to be a potentially significant contributor to dose but because 
of its very short half-life was not considered further in this analysis. 
To a large extent, the effectiveness of colloids at facilitating contaminant transport is due to their 
very large surface area (relative to mass and volume) available for sorption. Depending on the 
size distribution of colloids in the dispersion, the impact of choosing a mass-based Kd value, or a 
surface-area-based Ka, may be significant. The greatest deviation exists in situations in which an 
inordinately large number of very small colloids exist, which have a high surface-area-to-mass 
ratio. Since nearly all available sorption information is mass-based, and conversion to surface

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MDL-EBS-PA-000004 REV 00 67 June 2003 
area-based information is not always straightforward, a mass-based Kd value approach is used 
here. 
By considering the effect of aqueous chemical conditions on sorption, the selection of relevant 
Kd values is simplified. The behavior of the mineral surface is primarily controlled by pH and 
ionic strength (particularly concentrations of sodium, calcium, and potassium). The behavior of 
the sorbate is primarily controlled by its oxidation state, pH, and the partial pressure of carbon 
dioxide (Pco2). For minerals in which the sorption mechanism is primarily by ion exchange 
(e.g., clay minerals), ionic strength impacts sorption of Cs on clay minerals (especially at their 
edges), because cations compete with radionuclides for exchange sites. Ionic strength is less 
important for actinides, in that some anions and cations contributing to ionic strength affect 
sorption by forming complexes with the actinides. 
Under the oxidizing conditions at Yucca Mountain, radionuclides will occur in oxidized forms 
which, in general, results in decreased sorption. Plutonium will disproportionate and be 
simultaneously present in multiple valence states (IV, V, and VI at YMP). The actinide elements 
discussed exhibit strong hydrolysis behavior and tend to form strong carbonate complexes. The 
actinides tend to be completely hydrolyzed at pH values above about 6 where they are present as 
neutral hydroxo complexes. At slightly alkaline pH values and above, they will exist as 
negatively charged anionic hydroxyl complexes. Consequently, sorption is greatest in the near 
neutral pH range. The Pco2 of the system has minor or negligible effect on sorption of Cs but a 
strong effect on sorption of the actinides. Carbonate is a strong complexant, and at alkaline pH 
values, the actinides may form mono-, di-, and tri-carbonato complexes, depending on the 
actinide (and valence). The presence of these complexes tends to decrease sorption. 
To develop colloid Kd values, information provided by project data, a previous project report 
(CRWMS M&O 2000 [DIRS 152773]), and published literature was considered. Several 
sources of YMP-specific sorption data exist from Los Alamos National Laboratory research. Lu 
et al. (1998 [DIRS 100946], 2000 [DIRS 154422]) provide useful information on the sorption of 
Pu(IV) and Pu(V) on colloidal dispersions of hematite, goethite, montmorillonite, and silica. 
Information on Am(III) is provided for all but goethite. Sorption was measured as a function of 
time up to 4 or 10 days. Desorption was measured after 150 days because desorption tends to be 
much slower in these mineral-sorbate systems. The experimentally determined Kd values are 
summarized in Table 6.

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MDL-EBS-PA-000004 REV 00 68 June 2003 
Table 6. Experimentally Determined Kd Values for Pu and Am Sorption Onto Hematite and 
Montmorillonite 
Kd Values, mL/g Phenomena 
Investigated J-13 Water Synthetic J-13 Water 
Plutonium-Hematite (DTN: LA0003NL831352.002 [DIRS 148526]) 
Sorption (forward, up to 10 days; colloid 
concentration not specified in DTN) 5.00 x 103 to 1.10 x 105 1.20 x 105 to 7.00 x 105 
Desorption (backward, 200 days; colloid 
concentration not specified in DTN) 3.40 x 105 3.20 x 105 
Colloid Concentration (forward, 10 to 150 
mg/L, 10 days) 7.50 x 103 to 3.70 x 104 7.70 x 103 to 2.60 x 104 
Temperature (forward, 20o to 80o C, 10 
days) 1.70 x 105 to 4.90 x 106 [ not in DTN ] 
Plutonium-Montmorillonite (DTN: LA0003NL831352.002 [DIRS 148526]) 
Sorption (forward, up to 10 days; colloid 
concentration not specified in DTN) 2.30 x 102 to 5.80 x 103 2.40 x 102 to 6.50 x 103 
Desorption (backward, 200 days; colloid 
concentration not specified) 6.70 x 103 36.50 x 103 
Colloid Concentration (forward, 10 to 150 
mg/L, 10 days) 5.20 x 103 to 2.70 x 104 3.20 x 103 to 2.40 x 104 
Temperature (forward, 20o to 80o C, 10 
days) 9.50 x 103 to 2.00 x 105 [ not in DTN ] 
Americium-Hematite (DTN: LA0005NL831352.001 [DIRS 149623]) 
Sorption (forward, up to 10 days; colloid 
concentration not specified in DTN) 7.90 x 104 to 1.00 x 107 1.20 x 105 to 6.20 x 106 
Desorption (backward, 200 days; colloid 
concentration not specified) 1.90 x 105 8.40 x 104 
Colloid Concentration (forward, 10 to 150 
mg/L, 10 days) 1.90 x 106 to 1.60 x 107 1.80 x 106 to 2.80 x 107 
Temperature (forward, 20o to 80o C, 10 
days) 1.80 x 105 to 6.50 x 105 (not in DTN) 
Sorption (forward, up to 10 days; colloid 
concentration not specified in DTN) 7.10 x 103 to 6.50 x 104 2.30 x 104 to 1.10 x 105 
Desorption (backward, 200 days; colloid 
concentration not specified) 9.10 x 104 1.80 x 104 
Colloid Concentration (forward, 10 to 150 
mg/L, 10 days) 1.60 x 105 to 1.50 x 106 1.60 x 105 to 8.40 x 105 
Temperature (forward, 20o to 80o C, 10 
days) 6.00 x 104 to 2.70 x 106 (not in DTN) 
Source: Lu et al. 1998 [DIRS 100946]; Lu et al. 2000 [DIRS 154422]; DTNs: LA0003NL831352.002 [DIRS 148526], 
LA0005NL831352.001 [DIRS 149623]. 
Several significant compendia of sorption data have been assembled in the past decade. One 
useful example is the compendium developed by the National Cooperative for the Disposal of 
Radioactive Waste (NAGRA, Switzerland) (Stenhouse 1995 [DIRS 147477]). The objective of 
that work was to compile a set of Kd values useful for evaluation of waste-disposal in 
hypothetical sites in Switzerland. The sorbents considered were crystalline rock, marl, and 
bentonite, all with reducing groundwaters (or pore water, in the case of bentonite). Ionic 
strengths are similar to J-13 water or greater. Despite differences in those conditions, the 
information compiled in the National Cooperative for the Disposal of Radioactive Waste 
document is useful for YMP in that it includes consideration of phenomena affecting sorption.

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MDL-EBS-PA-000004 REV 00 69 June 2003 
The mineralogic compositions of crystalline rock, marl, and smectite (bentonite) were compiled 
and used to weight relevant sorption values from their compendium. The chemical compositions 
of relevant groundwaters or pore waters, all somewhat reducing, were also compiled. For Yucca 
Mountain colloid calculations, the sorption values for crystalline rock were selected for two 
reasons. First, the mineral phase dominating sorption is similar in mineralogy to Yucca 
Mountain waste form and groundwater colloids. A significant observation made in the National 
Cooperative for the Disposal of Radioactive Waste report is that sorption by a rock is typically 
dominated by one mineral constituent, usually a phyllosilicate mineral. Second, the groundwater 
is closest to Yucca Mountain groundwater in terms of pH, ionic strength, and redox conditions. 
National Cooperative for the Disposal of Radioactive Waste proposed realistic values and 
conservative values. The conservative values for the actinides were developed by National 
Cooperative for the Disposal of Radioactive Waste to account for uncertainty in oxidation states 
(composite Kd values were reduced by an order of magnitude). With respect to the oxidation 
state, the conservative values would be more relevant to Yucca Mountain. However, to 
compensate for the use of a mass-based Kd approach on colloids, the realistic values are useful. 
In Table 7, the rock composite Kds and individual Kd values for smectite and oxides/quartz are 
compiled. The individual mineral values are probably more suitable to consider for Yucca 
Mountain colloid Kd values. 
Table 7. Summary of Sorption Data Developed by National Cooperative for the Disposal of 
Radioactive Waste for Bentonite, Crystalline Rock, and Marl 
Radionuclide 
and 
Oxidation 
State(s) 
NAGRA Database NAGRA Rock 
Kd (mL/g) 
(page) 
NAGRA Mineral Kd (mL/g) 
Sr(II) 461 entries; 
39 references 
1,000 
(p. Sr-11) 
smectite = 20; 
oxides, quartz = 0 
Cs(I) 516 entries; 
41 references 
1,000 
(p. Cs-11) 
smectite = 2,000; 
oxides, quartz = 40 
Th(IV) 79 entries; 
22 references 
5,000 
p. Th-7) 
smectite = 2,000; 
oxides, quartz = 1,000 
Pa(V) 21 entries; 
12 references 
1,000 
(p. Pa-3) 
NAGRA uses Zr(IV) as analog for 
Pa(IV); 
use Np(V) for Pa(V) for YMP 
U(VI) 382 entries; 
32 references 
5,000 
(p. U-7) 
smectite = 100; 
oxides, quartz = 20 
Np(V) 389 entries; 
53 references 
5,000 
(p. Np-8) 
smectite = 100; 
oxides, quartz = 20 
Pu(IV, V, VI) 298 entries; 
25 references 
5,000 
(p. Pu-10) 
smectite = 1,000; 
oxides, quartz = 200 
Am(III) 198 entries; 
34 references 
5,000 
(p. Am-9) 
smectite = 10,000; 
oxides, quartz = 1,000 
NOTE: NAGRA = National Cooperative for the Disposal of Radioactive Waste 
Source: Stenhouse 1995 [DIRS 147477].

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A second useful compendium was developed for the U.S. Environmental Protection Agency 
(EPA 1999 [DIRS 147475]). In that work, information on radionuclides including Sr, Cs, Th, U, 
and Pu is compiled (no information for Pa, Np, or Am). The assembled data are interpreted to 
predict ranges of Kd values for soils in shallow subsurface environments. Redox conditions for 
that system are oxidizing, which makes it useful for the redox-sensitive radionuclides at YMP. 
Unfortunately, the group of radionuclides covered does not provide an analog element for 
trivalent or pentavalent elements, such as Am(III), Pa(V), or Np(V). 
In the EPA (1999 [DIRS 147475]) study, published literature was reviewed to determine the 
predominant aqueous chemical conditions affecting sorption in soils for each contaminant. For 
Sr, soil clay content and groundwater pH were used as criteria to recommend Kds. For Cs, clay 
content was also used, but pH is less important because Cs exists as an aqueous ion and does not 
complex, and it sorbs by ion exchange, a process that is not affected by pH-dependent surface 
charge. For Th, pH and sorbate concentration are important. At concentrations close to its 
solubility limit, Kds tend to increase. For U, the pH was important. For Pu, carbonate 
complexation has a strong influence on sorption, and so carbonate concentration, as well as clay 
content, were considered as criteria to select a relevant Kd. In Table 8, Kd values are compiled 
based on aqueous chemical conditions closest to those expected in ambient groundwater at 
Yucca Mountain. Unfortunately, the Kd values are expressed in a minimum to maximum format, 
with no indication of distribution. Some ranges, for example U, span almost six orders of 
magnitude. To narrow the range, the geometric means were calculated below and reported in 
Table 8, column 4. 
Table 8. Summary of Sorption Data Developed by U.S. Environmental Protection Agency 
Radionuclide 
and Oxidation 
State(s) 
Database 
Soil and pH Categories: 
Smectite Colloids (high clay) 
Iron Oxyhydroxide Colloids 
(low clay) 
Smectite Kd (mL/g) Range of 
Geometric Means 
Iron Oxyhydroxide Kd (mL/g) 
Range of Geometric Means 
Sr(II) 63 entries 
(166 in Appendix) 
high clay (20-60 wt%); pH 8-10; 
low clay (<4 wt%); pH 8-10 
300 to 1,700 (714); 
3 to 120 (19) 
Cs(I) 177 Kd values high clay (20-60 wt%) 
low clay (<4 wt%) 
80 to 26,700 (1,462); 
30 to 9,000 (520) 
Th(IV) 17 entries pH 8-10; [Th] <10-9 M 
(pH and Th concentration important) 
20 to 2,000 (200) 
Pa(V) not discussed, 
no good analog --------- --------- 
U(VI) 20 references pH 8 
(pH important) 
0.4 to 250,000 (316) 
Np(V) not discussed, 
no good analog --------- --------- 
Pu(IV, V, VI) high clay (51-70 wt%); 3-4 meq/L CO3
2-; 
low clay (<4 wt%); 3-4 meq/L CO3
2- 
1,860 to 2,550 (2,178); 
80 to 470 (194) 
Am(III) not discussed, 
no good analog --------- --------- 
Source: EPA 1999 [DIRS 147475].

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MDL-EBS-PA-000004 REV 00 71 June 2003 
A second source of sorption data from Los Alamos National Laboratory research is compiled in 
the project report focusing on transport properties in the unsaturated and saturated zones 
(CRWMS M&O 2000 [DIRS 152773]), which also considers previous Yucca Mountain reviews 
by Meijer (1992 [DIRS 100467]) and others. These ranges are generally comparably to values 
extracted from the National Cooperative for the Disposal of Radioactive Waste report (Table 7). 
For sorption onto colloids, their large surface areas suggest the use of the larger Kd values in the 
ranges, which is also conservative with respect to radionuclide transport. 
Another source of Yucca Mountain-specific sorption analytical results is presented in Honeyman 
and Ranville (2002 [DIRS 161657]). This paper investigated several aspects of colloidfacilitated 
radionuclide transport, including reduction of effective retardation of radionuclides by 
colloids and the effectiveness of colloids with respect to radionuclide mobility in the presence of 
stationary phases available for radionuclide sorption. The colloid-stationary phase system is 
discussed further in Section 6.3.3.2 in the context of irreversible sorption. 
Honeyman and Ranville (2002 [DIRS 161657]) summarize an analysis by Contardi et al. (2001 
[DIRS 162732]) that incorporated Yucca Mountain-vicinity groundwater chemistry and colloid 
size and concentration data from Kingston and Whitbeck (1991 [DIRS 113930]). Kd values were 
calculated with the use of a diffuse layer model and based on three principles: (1) the system is 
symmetrical, i.e., the colloids and stationary phases are similar with respect to mineralogy; (2) 
the colloids are stable; and (3) the system is in sorptive equilibrium. The ratio of stationary 
phase to colloid surface areas ranged up to roughly two orders of magnitude (3.2 to 63). Colloid 
concentrations of up to about 100 mg/L were included. In the system analyzed, approximate Kd 
value ranges (mL/g) for five radionuclides were given (Table 9). 
Table 9. Modeled Kd Values for Pu, Am, Th, Np, and U Sorption Onto Yucca Mountain-Vicinity Colloids 
Radionuclide Sorbate and 
Oxidation State(s) at YMP Kd Values, mL/g 
U(VI) 1 x 100 to 6 x 102 
Np(V) 1 x 101 to 1 x 102 
Pu(V) 1 x 103 to 1 x 104 
Th(IV) 2 x 103 to 9 x 104 
Am(III) 1 x 104to 1 x 107 
Source: Honeyman and Ranville 2002 [DIRS 161657]. 
Table 10 lists Kd value ranges used in the TSPA-LA model calculations with their uncertainties 
developed after examination of the references supporting Tables 6, 7, 8, and 9. Note that values 
for Am are also used for Th because its properties are not well known and because it has similar 
sorption tendencies as Am. Values for Am are also used for Pa because its sorption properties 
are likewise poorly known. Given the non-exact nature of these Kd values, encompassing 
(bounding) ranges are adopted, with distributions that emphasize the upper parts of the ranges. 
Waste form colloids, corrosion-generated colloids, and seepage water/groundwater colloids may 
become pseudocolloids through reversible sorption of aqueous radionuclides onto them. Kd 
values for combined adsorption and desorption of Pu, Am, Pa, Th, and Cs on waste form, iron

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MDL-EBS-PA-000004 REV 00 72 June 2003 
oxyhydroxides, and groundwater colloids are used to determine effective reversibility of the 
radionuclides on colloids according to the relationship: 
RNadsorbed/desorbed = RNdissolved x Kd,RN x Mcolloid (Eq. 7) 
The Kd values in Table 10 are based on the following: 
 Ranges are drawn from the following references: EPA (1999 [DIRS 147475]), Stenhouse 
(1995 [DIRS 147477]), Lu et al. (1998 [DIRS 100946]), Lu et al. (2000 [DIRS 154422]), 
CRWMS M&O (2000 [DIRS 152773]), and Honeyman and Ranville (2002 [DIRS 
161657]). 
 For a given radionuclide (except Cs) the maximum value of each range is the same to 
allow for the possibility that iron oxyhydroxide will occur both as iron oxyhydroxide 
colloids and as coatings on, or microcrystalline aggregates in association with, smectite 
colloids in the iron-rich waste package environment. For Cs, which attaches more 
strongly to smectite (by ion exchange) than iron oxyhydroxide, the ranges are different 
for iron oxyhydroxide and smectite. 
 The Kd intervals and probabilities are intended to cover the entire ranges and emphasize 
the higher ends of the ranges but de-emphasize the highest intervals. These distributions 
are used because (1) the ranges are based on data for both colloids and larger minerals, 
and it is believed that Kd values for colloids will be higher than for larger minerals due to 
their higher specific surface area; and (2) because of the mechanisms of surface 
phenomena that actually prevail, Kd values tend to over-predict desorption over time of 
actinide metals from iron oxyhydroxide colloids, i.e., they under-predict retention by the 
colloids. 
 Kd values ranges and distributions for Th and Pa are assumed to be those of Am primarily 
because of limited data on Th and Pa. 
 The ranges are believed to incorporate adequately the uncertainties inherent in uncertain 
data from disparate sources.

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MDL-EBS-PA-000004 REV 00 73 June 2003 
Table 10. Kd Values (mL/g) Used for Reversible Radionuclide Sorption on Colloids in Total System 
Performance Assessment-License Application Calculations 
Radionuclide Colloid Kd Value Range 
(mL/g) 
Kd Value Intervals 
(mL/g) 
Kd Value Interval 
Probabilities 
Iron Oxyhydroxide 104 to 106 
<1 x 104 
1 x 104 to 5 x 104 
5 x 104 to 1 x 105 
1 x 105 to 5 x 105 
5 x 105 to 1 x 106 
> 1 x 106 
0 
0.15 
0.2 
0.5 
0.15 
0 
Pu 
Smectite 103 to 106 
< 1 x 103 
1 x 103 to 5 x 103 
5 x 103 to 1 x 104 
1 x 104 to 5 x 104 
5 x 104 to 1 x 105 
1 x 105 to 5 x 105 
5 x 105 to 1 x 106 
> 1 x 106 
0 
0.04 
0.08 
0.25 
0.2 
0.35 
0.08 
0 
Iron Oxyhydroxide 105 to 107 
< 1 x 105 
1 x 105 to 5 x 105 
5 x 105 to 1 x 106 
1 x 106 to 5 x 106 
5 x 106 to 1 x 107 
> 1 x 107 
0 
0.15 
0.2 
0.55 
0.1 
0 
Am, Th, Pa 
Smectite 104 to 107 
< 1 x 104 
1 x 104 to 5 x 104 
5 x 104 to 1 x 105 
1 x 105 to 5 x 105 
5 x 105 to 1 x 106 
1 x 106 to 5 x 106 
5 x 106 to 1 x 107 
> 1 x 107 
0 
0.07 
0.1 
0.23 
0.2 
0.32 
0.08 
0 
Iron Oxyhydroxide 
101 to 103 
< 1 x 101 
1 x 101 to 5 x 101 
5 x 101 to 1 x 102 
1 x 102 to 5 x 102 
5 x 102 to 1 x 103 
> 1 x 103 
0 
0.13 
0.22 
0.55 
0.1 
0 Cs Smectite 102 to 104 < 1 x 102 
1 x 102 to 5 x 102 
5 x 102 to 1 x 103 
1 x 103 to 5 x 103 
5 x 103 to 1 x 104 
> 1 x 104 
0 
0.2 
0.25 
0.5 
0.05 
0 
NOTE: In engineered barrier system calculations, upper bound of Kd ranges for Pu and Am on iron oxyhydroxide 
reduced by a factor of 100 to be compatible with mechanistic sorption model described in Section 6.3.3.2. 
6.3.3.2 Irreversible Sorption of Pu and Am to Colloids and Stationary Phases 
The criteria for the linear sorption model described above are not met in defense high-level waste 
glass degradation experiments, which show that plutonium is (probably) irreversibly attached to 
smectite colloids generated during the experiments (CRWMS M&O 2001 [DIRS 154071], 
Section 6.2.2). Further, evidence from sorption experiments with Pu and Am (Lu et al. 2000 
[DIRS 154422]) with colloidal hematite and goethite show that the rates of desorption (backward 
rate) of Pu and Am are significantly slower than the rates of sorption (forward rate). More 
importantly, over a significant time period (up to 150 days in some experiments), the extent of

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MDL-EBS-PA-000004 REV 00 74 June 2003 
desorption is considerably less than the extent of sorption. Special considerations must be made 
for these situations. 
Pu and Am are considered so strongly sorbed to colloids that, in essence, can almost be 
considered irreversibly sorbed and are modeled in this manner within the engineered barrier 
system (BSC 2003 [DIRS 163935], Attachment II). Pu transport velocities in soils reflect the 
fact that Pu binds strongly to soils, leaving very little, if any, soluble Pu available for 
groundwater transport or plant uptake. Coughtrey et al. (1985 [DIRS 154494]) estimate 
exchangeable Pu (soil available, best estimate, Table 2a, p. 119) to be less than one percent. At 
Rocky Flats, soil Pu is largely bound to soil metal hydroxides. Litaor and Ibrahim (1996 [DIRS 
161667]) used 0.01M CaCl2 as an extractant and measured Pu in Rocky Flats soil to be 0.04 to 
0.08 percent exchangeable. Bunzl et al. (1995) [DIRS 154468] measured exchangeable 
239+240Pu (0.5 to 1 percent) and 241Am (1.5 to 15 percent) from fallout-contaminated soils in 
Germany using 1M C2H7NO2 (ammonium acetate NH4C2H3O2) as the extractant. Transport of 
colloidal Pu over hundreds of meters was observed at the Nevada Test Site (Kersting et al. 1999 
[DIRS 103282]). Laboratory experiments of Pu sorption onto iron oxides have shown that only 
approximately 1 percent of the initially sorbed Pu can be desorbed into solution, even after 
months of time have elapsed (Lu et al. 2000 [DIRS 154422]), which is broadly consistent with 
field observations. 
In order to accommodate these observations in the colloid abstraction, the TSPA-LA model 
calculates irreversible and reversible sorption of Pu and Am as functions of specific surface area 
(SA), site density (NA), mass of corrosion colloids, dissolved concentration of Pu and Am, 
target-flux out ratio (FRN, Table 16), and other parameters (such as flow and diffusion rate) 
internal to the TSPA-LA model. This is done in such a way that a majority (90 to 99 percent) of 
Pu and Am are irreversibly sorbed, due to incorporation of parameter uncertainties (see BSC 
2003 [DIRS 163935], Attachment II). The reversibly sorbed portion is determined according to 
an equilibrium Kd value model (per Section 6.3.3.1; see Table 10 for values, ranges, and 
distributions). 
Note that this approach is mechanistically more advanced than the approach taken for TSPA-SR 
and in prior efforts. Previous treatments have relied solely on the application of Kds to describe 
uptake of dose-critical radionuclides onto colloids. A clearer understanding of the identity and 
abundance of colloidal material in the waste form and engineered barrier system has prompted 
the more fundamental modeling effort. At the same time, more recent analyses of actinide 
transport in the environment have provided evidence for irreversible sorptionthe tendency for 
sorbed material to desorb very slowly and for a strong colloidal component to environmental 
transport of Pu. To accurately represent each feature, the updated engineered barrier 
system/waste form colloid model separates sorbed Pu and Am each into two populationsan 
irreversibly sorbed fraction and a reversibly sorbed fraction. Accordingly, in the waste form and 
engineered barrier system TSPA-LA model, the upper bound of the Kd range for the reversibly 
sorbed fraction is reduced by a factor of 100 (which constrains the Kd value to the lower bound, 
which is a fixed value). The solid fluid partitioning of Pu and Am that the model predicts are 
consistent with the magnitudes of the respective Am and Pu Kd values used elsewhere in the 
unsaturated and saturated zone.

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It should be kept in mind that Kd values are rough measures of multiple surface reactions that 
nevertheless must be relied upon to describe sorption in the absence of a more precise 
understanding of system specifics. In the engineered barrier system and waste form, the nature 
and abundance of colloidal material is more predictable than elsewhere. There is consequently 
greater justification for applying a more elaborate model of actinide sorption onto colloids in the 
waste form and the engineered barrier system. The same level of system understanding cannot 
be assumed to exist elsewhere or for all other radionuclides. Consequently, the application of the 
more involved approach described previously cannot presently be justified in other situations. 
Sorption to immobile iron oxyhydroxide within the waste package is modeled. Honeyman and 
Ranville (2002 [DIRS 161657]) incorporated a stationary phase in their analysis of the effects of 
colloids on radionuclide retardation, as described in Section 6.3.3.1. The stationary phase 
competes strongly with the colloids for radionuclide sorption. For the symmetrical system 
described in Section 6.3.3.1, by far most of the Am mass was calculated as attached to the 
stationary phase; at most, 0.001 percent of the total Am was associated with colloids (Honeyman 
and Ranville 2002 [DIRS 161657], p. 140). This is a significant finding because due to its 
strongly sorptive properties Am is one of the radionuclides with the greatest potential (of the 
radionuclides of interest here: Pu, Pa, Cs, Am) for transport on colloids. 
In the colloid abstraction the difference in specific surface areas between the colloids and the 
stationary corrosion products is taken into account as well as the total surface areas (based on 
total masses). On the one hand Pu will tend to attach to the colloids with their higher specific 
surface area; on the other hand the much larger mass of stationary corrosion products relative to 
total colloid mass results in most of the dissolved Pu attaching to the stationary corrosion 
products. In order to accommodate the field and laboratory observations as well as the modeling 
results described, distribution of Pu between colloids and the stationary corrosion products was 
implemented such that a large fraction of total Pu is sorbed to corrosion products, a small 
fraction to colloids, and a small fraction remains dissolved in the fluid. These relative fractions 
are realistic and are simulated in the TSPA-LA model (see BSC 2003 [DIRS 163935]). 
Allocating a fraction of the total Pu onto the stationary corrosion products in this way reduces the 
quantity of Pu transported by colloids, but allowing sorption onto stationary corrosion products is 
more realistic than not including this process. 
Specific Surface Area (SA) and Site Density (NS)Values for specific surface area (SA) and 
reactive site density (NS) on three different iron oxyhydroxides, a-FeOOH (goethite), a-Fe2O3 
(hematite), and Fe(OH)3nH2O (ferrihydrite or hydrous ferric oxide) as tabulated from the 
literature are listed in Table 11.

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Table 11. Published Values for Specific Surface Area (SA) and Site Density (NS) for Iron Phases 
SA (m2/g) NS (sites/area or wt.) Mineral/phase Min Max Min Max Source 
2.6/nm2 18/nm2 
a-FeOOH 
(goethite) 
45 169 
1.35 x 10-3 mol/g 
Langmuir 1997, Table 
10.2, p. 345 [DIRS 
100051] 
a-Fe2O3 
(hematite) 
1.8 
(natural) 
3.1 
(synthetic) 
5/nm2 22/nm2 
Langmuir 1997, Table 
10.2, p. 345 [DIRS 
100051] 
20/nm2 
Fe(OH)3nH2O 
(ferrihydrite) 
250 600 0.1 mole/ mole 
Fe 
0.91 mol/ mole 
Fe 
Langmuir 1997, Table 
10.2, p. 345 [DIRS 
100051] 
HFO 159 720 0.001 (Type 1) 
0.1 (Type 2) 
0.01 (Type 1) 
0.91 (Type 2) 
Dzombak and Morel 
(1990 [DIRS 105483]), 
Table 5.1, p.91 for SA 
and Tables 5.2 and 
5.3, pp. 92 to 93 for NS 
NOTE: Type 1 sites are high-affinity cation binding sites; Type 2 sites are the total reactive sites 
available for sorption of protons, cations, and anions as determined from observed sorption 
maxima (Dzombak and Morel 1990 [DIRS 105483], p. 92). HFO = hydrous ferric oxide. 
Jenne (1998 [DIRS 162328]) states, [n]otwithstanding four decades of research on methods of 
surface area (SA) and adsorption site concentration measurement, (Csite). SA measurements on 
similar materials differ by up to an order of magnitude and a priori determinations of Csite,tot 
[concentration of all reactive sites] on oxides and clay minerals by titration or tritium exchange 
are generally higher than CM,ads,max [maximum concentration of adsorbed metal] by up to an 
order of magnitude... It has been indicated that the use of a surface area measured on dry 
samples in a vacuum may not adequately represent the surface area of a mineral in suspension. 
Further, the variation in site density of Fe(OH)3 may reflect differing microporosities (which 
could also be true of other oxides and aggregates as well) (Jenne 1998 [DIRS 162328]). 
Because of the uncertainties in SA and Csite (or NS as used here) measurements, it has been 
recommended (by Davis and Kent 1990 [DIRS 143280]) that specific values be adopted for these 
parameters. They state (p. 227)a parsimonious modeling approach is needed in order to 
extend surface complexation theory to applications in natural systems. In complex mixtures of 
minerals it is often difficult to quantify the numbers of surface functional groups that are present 
from various minerals. We recommend that binding constants for strong-binding solutes be 
derived with a site density of 2.31 sites/nm2 (3.84 moles/m2) for all mineralsWhile the actual 
Gmax [maximum adsorption density] may vary from 1 to 7 sites/nm2, it is important that one value 
be selected to encourage the development of a self-consistent thermodynamic database that can 
be applied easily to soils and sedimentsTo encourage unanimity within the field, the particular 
value of 2.3l sites/nm2 because has been chosen because it is consistent with the value chosen by 
Dzombak and Morel (1990 [DIRS 105483]) to describe ferrihydrite (0.205 moles per mole of 
Fe), assuming a specific surface area of 600 m2/g of Fe2O3H2O. The value recommended

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approximates the site densities found by adsorption on various minerals, including goethiteand 
the edge sites of clay minerals 
Based on these considerations, the following values are used for SA and NS of iron oxyhydroxide 
corrosion phases in the colloid model implemented in TSPA-LA calculations: 
SA 1.8 - 720 m2/g (log uniform distribution) 
NS 2.31 sites/nm2 (fixed value) 
The SA value is provided in Table 16. 
6.3.3.3 Embedded Radionuclides in Defense High-Level Waste Glass Colloids 
The colloid model abstraction accounts for waste form smectite colloids observed in the defense 
high-level waste glass degradation experiments with embedded Pu and Am radionuclides by 
treating them as a separate colloid subtype and assuming that the embedded radionuclides are an 
intrinsic part of the colloid, not in equilibrium with the aqueous system. These embedded 
radionuclides are effectively attached irreversibly to the colloid. Pu and Am are stipulated to 
occur as embedded in defense high-level waste glass smectite colloids. In this model, waste 
form colloid parameters are represented entirely by the defense high-level waste glass 
degradation colloids with embedded radionuclides. See Sections 6.3.1.1 and 6.3.2.4 for further 
details. 
6.3.4 Potential Effects of Microbes and Organic Components 
An assumption is made in this abstraction that microbes and organic compounds do not affect the 
stability of inorganic colloids (Section 5, Assumption 5.9). The assumption is probably 
conservative, since it appears from information reviewed that such interactions would tend to 
destabilize colloids, thereby decreasing the mobility of associated radionuclides. However, 
under certain circumstances organic compounds may tend to stabilize inorganic colloids. 
Therefore the rationale for this assumption is presented in considerable detail below. 
Microbes and microbe fragments may occur in groundwater as colloid-sized particles to which 
radionuclides can sorb or be actively bioaccumulated across the cell membrane. They may 
impact local groundwater chemistry in and around the waste package, oxidation of metallic iron, 
and aggregation of colloidal materials used a food source (resulting in decreased concentration). 
The effects of microbes in colloid-facilitated transport in the repository can include: 
 Microbial oxidation of metallic iron can produce iron-oxide colloids and aggregates. 
 Microbially influenced corrosion can accelerate radionuclide release into the surrounding 
environment (CRWMS M&O 2000 [DIRS 151561]). 
 Microorganisms can decrease the concentration of stable colloids by aggregating 
colloidal material that they use as a food source. This has been shown to result in a 
decrease in colloid concentrations of up to 91 percent (Hersman 1995 [DIRS 100750]).

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Microbes can impact transport of radionuclides a number of ways. First, in some systems, 
microbes can passively or actively bioaccumulate radionuclides. If the microbes are mobile, 
they can facilitate transport of the radionuclides. Alternatively, the microbes may be readily 
filtered by the rock or may form biofilms, in which case they retard transport. Second, microbes 
may produce exudates, for example organic complexants, which may enhance the solubility of 
radionuclides and affect their sorption characteristics if complexes are formed. Third, in the 
course of extracting energy or nutrients, microbes may generate colloids by degrading materials 
or may actually destroy colloids by consuming them or by facilitating agglomeration. Fourth, in 
some systems, microbes are able to reduce the oxidation states of some multivalent 
radioelements (e.g., U, Np, and Pu). Typically, reduced forms of radionuclides are less soluble 
and more strongly sorptive. 
Development of a rigorous model for the impact of microbes would require YMP-relevant data 
on microbe concentration, size, shape, sorption properties, the effect of microbial activity on 
mobility, biofilm formation, rock-microbe interaction, plume characteristics, nutrient 
availability, microbe longevity, etc., as well as the rates of processes. Because of the complexity 
of collecting these data, a microbe-facilitated transport model was not attempted. For microbes 
to impact near-field performance, microbes must be present and sufficient energy sources and 
nutrients be available. Substantial concentrations of nutrients will not be present in the near-field 
environment. For microbes to have an unfavorable impact on performance, they must 
bioaccumulate radionuclides and must be transportable. Because of the relatively large size of 
microbes, they will be readily filtered during transport, along with any bioaccumulated 
radionuclides, which is beneficial. Inclusion of microbial colloid transport in the waste and 
engineered barrier system in the TSPA-SR calculation would reduce interpreted doses. 
The transport of microbes within the waste package and invert is not currently modeled in 
TSPA-LA. Microbe-facilitated contaminant transport in shallow saturated systems has been 
demonstrated in the literature (Fontes et al. 1991 [DIRS 147337]; Harvey et al. 1989 [DIRS 
147338]; Kim and Corapcioglu 1996 [DIRS 147342]; Weiss et al. 1995 [DIRS 147345]; Yates 
and Yates 1988 [DIRS 147348]), but few, if any, studies demonstrate transport through the 
vadose zone. Interactions among inorganic colloids and various types of organic components in 
natural systems are ubiquitous and complex. It is generally understood that some forms of 
natural organic matter, such as fulvic compounds from soils, will stabilize inorganic colloids in 
natural waters (Buffle et al. 1998 [DIRS 161653]; Hahn and Stumm 1970 [DIRS 161656]). 
However, certain types of natural organic matter, such as the polysaccharides, have been shown 
to have a tendency to destabilize colloids (Buffle et al. 1998 [DIRS 161653]; Wilkinson et al. 
1997 [DIRS 161734]; Wilkinson et al. 1997 [DIRS 161732]). Further, under certain 
circumstances they may stabilize colloids (Napper 1983 [DIRS 161735]; Liu et al. 2000 [DIRS 
161777]; Walker and Grant 1996a [DIRS 161736]; Walker and Grant 1996b [DIRS 161738]; 
Yokoyama et al. 1990 [DIRS 161675]). Polysaccharides and other types of organic compounds 
are produced by microbes and introduced to aqueous systems as byproducts of metabolism and 
cell fragments. Given the relatively low reported quantities of humic and fulvic compounds in 
groundwater near Yucca Mountain (Minai et al. 1992) [DIRS 100801], along with the potential 
for the growth of microbial colonies in the repository, a study of potential effects of microbes on 
the stability and transport of radionuclide-bearing inorganic colloids was initiated by the project.

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6.3.4.1 Potential Microbial Communities Within the Engineered Barrier System 
A case for the occurrence of microbes in some abundance in the repository has been modeled 
and is presented in In-Drift Microbial Communities (CRWMS M&O 2000 [DIRS 151561]). 
That study was performed to develop a model for the possibility and probability of microbial 
communities occurring in the engineered barrier system of the repository, and in addition to use 
the model to assist the total system performance assessment calculation group in the modeling of 
the engineered barrier system geochemical environment. Secondary reasons for the study 
included the application of portions of the conceptual model to near- and far-field 
geomicrobiological processes, unsaturated zone and saturated zone transport, portions of the 
waste package modeling affected by microbe-induced corrosion, and to provide a microbial 
source term for colloid modeling in the drift. 
In assessing the potential effects on microbial populations within the engineered barrier system, 
In-Drift Microbial Communities (CRWMS M&O 2000 [DIRS 151561]) considered the drift 
mineralogy; drift physical parameters; metals, alloys, and cement used in engineered barrier 
system components; waste dissolution rates and quantities; groundwater compositions and 
infiltration rates; and compositions and fluxes of gases (e.g., CO2, water vapor). Environmental 
limits on microbial activity considered include redox conditions, temperature, radiation, 
hydrostatic pressure, water activity, pH, salinity, available nutrients, and others. The abundance 
of water and phosphorous were found to be the two environmental components which, if in short 
supply, could limit the development of microbial communities in the Yucca Mountain repository 
under the probable physicochemical conditions likely to be present in the proposed repository 
configuration. 
Because the water and phosphorous in the repository would potentially be available in sufficient 
quantities to allow for the growth of microbial communities at certain stages of the postclosure 
period (CRWMS M&O 2000 [DIRS 151561]), the potential effects of these communities on the 
transport characteristics of radionuclide-bearing colloids become important. The colloid-type 
behavior of microbe transport is usually modeled with techniques used to analyze inorganic 
colloid transport, e.g., DLVO theory, filtration, and advection-dispersion. Microbes also adhere 
to substrates and colonize in biofilms by producing extracellular polymers, usually 
exopolysaccharides, resulting in a means of sorption to solid surfaces and to each other. 
6.3.4.2 Results of Experiments with Bacteria 
Microbes and inorganic colloids in proximity to one another may result in collisions, which 
allow mutual adhesion or adsorption and result in particle size growth (agglomeration) (Buffle et 
al. 1998 [DIRS 161653]; Hersman 1995 [DIRS 100750], 1997 [DIRS 100763]). This increase in 
particle size can have several effects on the potential for colloids to facilitate radionuclide 
transport within the repository: (1) for a given range of pore sizes in the transport medium, the 
larger composite particles may become filtered more readily than the individual microbe or 
colloid; (2) the larger particles will tend to diffuse more slowly and/or may sink through 
gravitational settling; and (3) the interactions of relatively large populations of colloids and 
microbes can result in agglomerated particles sufficiently large that the dispersion becomes 
unstable and the microbe and colloid particles flocculate. Reduced transport from increased 
particle size is even more significant in the situation where water is present as thin films within

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the pore spaces and on the engineered barrier system components. In all of these processes the 
net result is particle size increase and reduced transport of colloids and associated radionuclides. 
The mechanisms which can affect the probability of microbe-colloid interactions are many and 
include chemotaxis, Brownian motion, electrostatic attraction, van der Waals interaction, 
electrical double layer effects, and cell surface hydrophobicity (Hersman 1997 [DIRS 100763]). 
Attraction of a microbe to a stationary surface or other colloids depends on the specific polymers 
on the microbial surface, which are influenced by microbe species, substrate, and environmental 
conditions. Hersman (1995 [DIRS 100750]) conducted experiments with Yucca Mountainnative 
bacteria and bentonite clay. In one test, agglomeration of clay colloids in a sterile 
microbial growth medium was compared to agglomeration in a medium into which a bacterium 
was introduced. The test results showed greater agglomeration in the growth medium inoculated 
with bacteria. In a second test the bacteria were cultured in the medium and the test repeated 
with those bacteria, and similar results were noted. 
The development of biofilms on a substrate has been shown to result in an increased tendency to 
attract suspended inorganic colloids. Investigators of processes occurring within biofilms have 
observed water and nutrient movement within and through biofilms and measured diffusion 
coefficients (Beyenal and Lewandowski 2000 [DIRS 161652]; Lewandowski et al. 1995 [DIRS 
161664]; Wanner et al. 1995 [DIRS 161674]). Sprouse and Rittmann (1990 [DIRS 161672]) and 
Rittmann and Wirtel (1991 [DIRS 161671]) demonstrated that biofilm colonization increased the 
colloid cohesion efficiency, a, in a system where the collector was granular activated carbon in a 
methanogenic fluidized bed and the colloids were milk solids approximately 1 micron in 
diameter. Lo et al. (1996 [DIRS 161669]) concluded from an experiment with Fe(III) oxide 
colloids in a biofilm reactor that the deposition of Fe(III) oxide colloids increased slightly with 
biofilms present. Further iron deposition on surfaces increased with increasing particle size, 
suggesting interception of the colloids and/or sedimentation. 
6.3.4.3 Organic Matter and Inorganic Colloid Stability 
For purposes of discussion naturally occurring organic matter may be considered to fall into 
three classes. The most generally abundant class includes the soil-derived humic and fulvic 
acids, which typically range from 40 to 80 percent of natural organic matter in surface waters 
(Buffle et al. 1998 [DIRS 161653]). The second class of natural organic matter includes the rigid 
biopolymers, i.e., structural, fibrillar polysaccharides or peptidoglycans released from plankton 
as exudates or cell wall components, and range from 10 to 30 percent of natural organic matter in 
surface waters (Buffle et al. 1998 [DIRS 161653]). The third class includes the flexible 
biopolymers, the most persistent of which is aquagenic refractory organic matter, which forms 
from a recombination of amino acids, sugars, etc. released by plankton. aquagenic refractory 
organic matter concentrations rarely exceed a few milligrams per liter (although in pelagic 
waters of oceans and large lakes it may comprise 90 percent of the total natural organic matter; 
Buffle et al. 1998 [DIRS 161653]). Natural organic matter of all three classes may persist in the 
environment for periods of up to decades to thousands of years (Buffle et al. 1998 [DIRS 
161653]). 
Under particular circumstances suspended colloids may be mutually attracted, leading to 
aggregation and flocculation, or repelled, promoting stability of the suspension. In circumstances

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favoring aggregation, colloids of a given type (e.g., clays, fulvic acids) may aggregate together 
(homoaggregation) or with colloids of other types (heteroaggregation). DLVO theory and 
Smoluchowski equations have been used to describe phenomena involving homoaggregation. 
However, there is no general theory to describe heteroaggregation, in particular 
heteroaggregation involving biopolymers (Buffle et al. 1998 [DIRS 161653]). 
Two general types of colloid interactions may be identified: (1) electrostatic and (2) polymeric. 
Electrostatic interactions are generally evaluated and described in terms of DLVO or related 
theory and are controlled by electric double-layer repulsion and van der Waals attraction. The 
stabilizing effect of fulvic acid sorption onto iron oxyhydroxide colloids, for example, results 
primarily from electrostatic forces. 
Polymers may affect inorganic colloid stability whether they are attached to the colloids (steric 
effects) or free in solution (depletion effects). (A polymer may be defined as a molecule with 
relatively high molecular weight consisting of regularly repeating units, or chemically similar 
units.) Organic polymer chains with molecular weight of about 10,000 have a chain dimension 
roughly that of, or greater than, the range of van der Waals attraction. Further, the molecular 
dimensions are relatively insensitive to the electrolyte concentration (Napper 1983 [DIRS 
161735]). 
Steric effects, where polymers are attached to compact inorganic colloids and may exhibit 
rod-like or coil-like appendages, may lead to aggregation through bridging between the 
polymer and colloid if the attractive force between the polymer and colloid is sufficient. On the 
other hand, a repulsive force between the polymer and colloid may promote stability. Depletion 
stabilization and aggregation have had little study and are not well understood (Napper 1983 
[DIRS 161735]). 
There is little information on interactions between flexible polymers and inorganic colloids in 
natural systems, although it is known that flexible polymers are relatively quickly degraded and 
so may have limited effect. Flexible polymers act primarily by sorbing to the colloid and 
modifying its surface charge and promoting flocculation by neutralizing the net surface charge. 
Neutralization depends, however, on the degree of coverage of the colloid surfacetoo much or 
too little coverage would result in a net charge on the colloid surface, which would encourage 
stability (Buffle et al. 1998 [DIRS 161653]). According to Walker and Grant (1996a [DIRS 
161736]) relatively little flexibility is required for adsorption of polymer. 
The biopolymers associated with microbial activity are mucopolysaccharides, pectic compounds 
(microbial cell walls and extracellular products), etc. These are fibrillar structures based on 
double or triple helix formation and are considered to be rigid polymers (Buffle et al. 1998 
[DIRS 161653]). Since it has been postulated that microbial colonies will develop in the 
repository, and since only very small quantities of humic and fulvic acids have been analyzed in 
Yucca Mountain groundwater (Minai et al. 1992) [DIRS 100801], then of the several types of 
organic compounds to be considered in the repository rigid polymers may have the most 
influence on colloid mobility. However, this would depend on the quantities and nature of 
materials introduced during construction of the repository and emplacement of waste (this 
potentially important issue of introduced materials and their effects on inorganic colloids and 
microbes/microbial products has not been examined).

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Interactions between inorganic colloids and rigid biopolymers probably lead to aggregation and 
sedimentation under most circumstances (Buffle et al. 1998 [DIRS 161653]). Aggregation and 
sedimentation rates have been positively correlated with increased quantities of fibrillar 
polysaccharides released by plankton (Buffle et al. 1998 [DIRS 161653]; Wilkinson et al. 1997 
[DIRS 161734] and 1997 [DIRS 161732]). Zumstein and Buffle (1989 [DIRS 161740]) showed 
that in a eutrophic lake environment chain-like organic matter was associated with sedimented 
clay and calcite colloidal particles and that fulvic acids tended to stabilize the inorganic colloids. 
Polymers have, of course, been used in industrial processes to stabilize colloidal dispersions. 
Liu et al. (2000 [DIRS 161777]) point out that natural polysaccharides have been used in 
flotation and suppression systems for virtually every type of industrially important mineral. For 
example, starch is used to suppress hematite, apatite, calcite, and coal while floating quartz and 
pyrite. (In the TSPA-LA colloid source term model, the inorganic colloids analyzed are stable 
subject to pH and ionic strength of the fluid and are not affected by organic materials.) 
Yokoyama et al. (1990) [DIRS 161675] describe the use of water-soluble polysaccharides as 
colloid stabilizers. These acidic polysaccharides stabilized colloidal dispersions through a steric 
stabilization mechanism. Their effectiveness was dependent on the steric layer thickness relative 
to the van der Waals attractive force. Further, increasing temperature increased the thickness of 
the steric layer, which increased the stability of the dispersion (Yokoyama et al. 1990 [DIRS 
161675]). This is in contrast to the generally destabilizing effect of increasing the temperature of 
a suspension of inorganic colloids. 
6.3.4.4 Discussion 
The possible effects of the interactions among the large variety of organic compounds and 
inorganic colloids are dauntingly numerous and complex. Given the overall results of the cited 
investigators, it appears reasonable to conclude that the presence of organic polymers such as 
those produced by microbes and their byproducts will generally reduce the stability of inorganic 
colloids and result in enlargement of particles through heteroaggregation, as has been inferred 
from the study of the eutrophic lake (Wilkinson 1997 [DIRS 161734] and 1997 [DIRS 161732]; 
Zumstein and Buffle 1989 [DIRS 161740]). Further, given this conclusion (and neglecting the 
possible influences of organic materials introduced to the repository during construction and 
waste emplacement) it is also reasonable that the occurrence of microbial communities in the 
Yucca Mountain Repository will likewise tend to decrease the stability and mobility of colloids. 
To the extent that the colloids are associated with radionuclides, this would also decrease the 
transport of radionuclides. 
The large body of literature describing the use of polymers in process technology for both 
suppression and peptization of colloids for the most part has not yet been reviewed. This is 
significant as, since much of our understanding of inorganic colloidorganic polymer 
interactions has been made available from research driven by numerous commercial applications 
of these principles, a final judgment regarding the effects of microbes and their products on the 
transport of inorganic colloids and associated radionuclides in the repository should ultimately 
depend upon a thorough review of the relevant literature. 
It is currently anticipated that the repository invert, comprised of crushed volcanic tuff with 
intergranular void spaces, will remain undersaturated with respect to groundwater. The adhesion

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of microbes to unsaturated porous media like the invert can be controlled by the level of fluid 
saturation and the extent of the air-water interface network within the medium. Since microbes 
tend to adhere strongly to the air-water interface, lower saturations would result in increased 
microbe retention and reduced transport. Given the demonstrated capacity of microbes to adsorb 
uranium (CRWMS M&O 2000 [DIRS 151561]), it follows that retention of microbes within the 
invert by these processes would result in retention of radionuclides as well. However, it is 
evident that should the invert become saturated, or nearly so, microbes and fragments with any 
associated radionuclides may become mobile and be transported, subject to the influences of 
aqueous chemistry, presence of organics, and pore sizes and fracture apertures of the geologic 
media. 
It is apparent that considerable uncertainty surrounds the rate that microbes would affect the 
system around the repository. Thus, given the current knowledge, it is difficult to estimate their 
effects on the colloid source term, in particular the effect of microbes on colloid concentration 
and stability. However, it is understood that microbial action will tend to increase the sizes of 
inorganic colloids, which promotes gravitational settling and filtration. Thus, not including the 
effects of microbes in colloid source term and transport analysis is considered reasonable, and it 
follows that neglect of the effects of microbes is reasonable with respect to total system 
performance assessment dose assessments. Thus, given the available evidence, it is proposed 
that the effects of microbes on colloid-facilitated radionuclide transport in the Yucca Mountain 
Repository be neglected (see Section 5.9, Microbes and Colloidal Organic Components). 
Neglecting the effects of microbes would (1) eliminate the effects of colloid-microbe 
agglomeration, with the concomitant increase in particle size, sedimentation, and pore clogging; 
and thereby (2) eliminate the effects that result in radionuclide retardation and/or retention. 
6.4 CONSIDERATION OF ALTERNATIVE MODELS 
The following sections describe three models considered as alternatives to the base-case model. 
One model considers the potential for colloid development and mobilization from the 
actinide-rich rind on altered commercial SNF. The second model considers the rate of colloid 
generation as a function of waste form degradation rate. The third model considers colloid 
generation as a function primarily of flow rate past the degrading waste. These models are listed 
in Table 12 along with the principal bases and screening criteria.

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Table 12. Alternative Conceptual Models Considered 
Alternative 
Conceptual 
Model 
Basis for Model Screening Assessment 
Production of 
CSNF Colloids 
from Spallation 
of U- and Pu- 
Rich Alteration 
Rinds 
 Rinds containing fine-grained Pubearing 
particles and U-silicates have 
been observed on degraded CSNF 
samples. 
 Although particles from this layer did 
not spall during the tests, spallation of 
colloid-size particles could occur 
under conditions different from those 
under which the tests were conducted. 
 Given the low-water, relatively 
quiescent conditions of the ANL tests, 
more extreme conditions and likely 
disruptive events (e.g., fuel rod 
distortion) would be investigated. 
 Given the large quantity of CSNF in the 
planned repository, the possible mobilization of 
actinide-rich particles subsequent to alteration of 
CSNF should be investigated. 
 Given anticipated disruptive events such as 
the collapse of fuel rod supports within the waste 
package, investigation should focus on the 
possible and likely ranges of conditions that 
could prevail and the postulated events that are 
likely to occur. 
 Additional data would be required to support 
this alternative model. 
 This ACM could be more conservative than the 
base-case model if it can be demonstrated that 
alteration rinds will spall and be transported 
under repository conditions. 
Rate of Colloid 
Generation 
(Argonne 
National 
Laboratory) 
 Rate of colloid spallation depends 
upon the rate of waste degradation 
 The rate of waste degradation may 
be defined by the rate of release to 
the alteration fluid of B (for DHLWG) 
and Tc (for CSNF) 
 The alternative model is tailored closely to the 
specific experimental configuration from which 
the supporting data were acquired. The position 
of this analysis is that, while promising, the 
model is currently not sufficiently developed for 
application to more generalized conditions. 
 It is uncertain whether this ACM is more 
conservative than the base-case model. 
Mechanisms 
of Colloid 
Generation in 
CSNF (Pacific 
Northwest 
National 
Laboratory) 
 Colloid generation at, and 
mobilization from, the surface of 
degrading waste is primarily related to 
flow rate at the waste surface. 
 The supporting concepts and data from the 
peer-reviewed literature were developed in the 
context of deposition and remobilization of 
existing colloids under conditions of significant 
groundwater flow. These conditions likely will 
not apply to conditions anticipated in the 
repository. 
 Mechanisms of colloid generation at the 
surface of corroding fuel may be different from 
mechanisms of mobilization of a discrete 
deposited colloid. 
 It is not certain whether this ACM is more 
conservative than the base-case model, although 
under unsaturated repository conditions 
radionuclide releases from colloids may be lower 
in this ACM. 
NOTE: ANL = Argonne National Laboratory; CSNF = commercial spent nuclear fuel; DHLWG = defense highlevel 
waste glass; ACM = alternative conceptual model. 
6.4.1 Conditions Affecting Integrity of Commercial Spent Nuclear Fuel Alteration Rinds: 
Colloid Formation and Development Model 
PurposeCorrosion testing of commercial SNF has yielded few colloids, and those detected 
had no significant associated Pu. However, samples exhibited alteration rinds or crusts

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 85 June 2003 
composed of a Pu-bearing fine-grained layer overlain by a mat of U-bearing phases. The 
purpose of this model is to reduce uncertainties surrounding this alteration rind by simulating the 
spalling or disintegration of the rind, estimating the potential for colloid formation and associated 
radionuclides, and estimating the potential effects on releases from the waste package of this 
additional source of radionuclide mobility. 
Experimental ResultsAs described in Section 6.3.1.2.1 the results of SNF and unirradiated 
UO2 degradation testing showed that, although few colloids were formed (or detected), a dense 
rind of alteration products formed at the surface of the samples. The alteration products in the 
rind included a concentration of fine particulates containing high levels of Pu in addition to Zr, 
Ru, and rare earth elements, as well as (and frequently overlain by) U oxyhydroxides and Usilicates, 
depending on the test conditions. Of the few colloids identified in the commercial SNF 
tests (CRWMS M&O 2001 [DIRS 154071], Section 6.2.2), one sample contained primarily a 
hydrous uranium oxide (schoepite) and a partially crystalline uranium silicate (soddyite). The 
colloids contained the rare earth elements La, Ce, Pr, Nd, Sm, and Eu. Plutonium was not 
detected in these colloids. In another sample smectite clay colloids were formed that were 
similar structurally and compositionally to the smectites produced in the glass tests. 
Environmental Conditions Not Considered in Experimental InvestigationsSeveral 
processes that could occur in the waste package have the potential to disrupt the integrity of the 
alteration rind. Distortion and breakage of a fuel rod due to corrosion and collapse of the fuel 
rod support system (basket) inside the package could result in breaking and dislodging of the 
rind from the fuel surface. High fluid flow rates (see Section 6.4.3) over exposed fuel surfaces 
could possibly dislodge portions of the rind. High flow rates might occur from high seepage 
rates into the waste package (continuous or transient), but more likely causes might be local 
displacements of fluid due to collapse of in-package components (essentially squeezing of 
fluid past the fuel surface), and intermittent or sustained dripping of fluid onto the fuel surface. 
Vibration or shock during a seismic event could shake loose portions of the rind. 
Alternative Model Description and Data NeedsThe alternative model would, in addition to 
calculating colloid and radionuclide concentrations as in the base-case model (Section 6.3), take 
into account possible repository conditions that were not incorporated into the various 
commercial SNF degradation tests. The model would require data acquired under the conditions 
chosen for modeling, including fuel rod distortion, shaking, and breakage; dripping at various 
rates and impact forces onto the fuel sample surface; various flow rates; combinations of 
environmental conditions; and isolation of the alteration rind and direct measurement of its 
properties. 
Assessment of Alternative ModelThis alternative model is currently at an early conceptual 
stage. It is intended to supplement and/or integrate with the base-case model as well as perhaps 
the two alternative models described in Sections 6.4.2 and 6.4.3. To be viable, the model 
requires data not yet at hand but available from appropriate tests. The data and model are 
necessary for any real reduction of the uncertainties surrounding the possible effects of breakup 
of the commercial SNF surface alteration rind on radionuclide releases from the waste package.

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MDL-EBS-PA-000004 REV 00 86 June 2003 
6.4.2 Rate of Colloid Generation Model 
The following subsections describe an approach to estimating the rate of release of Pu from 
degraded waste, based on the rate of waste degradation. This modeling approach is preliminary 
and is provided here as an alternative model for prediction of colloid release and transport in the 
waste package and drift and as a basis for potential subsequent discussion and project planning. 
It is based on a colloid generation rate model presented in Colloid-Associated Radionuclide 
Concentration Limits: ANL (CRWMS M&O 2001 [DIRS 154071]). The discussions of the 
formation of colloids from defense high-level waste glass and commercial SNF described in 
Sections 6.3.1.1 and 6.3.2.2 are based on testing performed at Argonne National Laboratory and 
are relevant to the rate-of-colloid-generation model. 
BackgroundIt was noticed that as the drip tests proceeded, whereas relatively soluble 
elements such as boron and neptunium increased smoothly with time, after about eight years the 
concentration in the leachate of the less soluble elements Pu (Figure 13) and Am increased 
sharply. This was interpreted as evidence that colloid-sized fragments of the clay layer spalled 
from the clay layer on the surface of the corroding glass and were released into the fluid. This 
behavior was not observed in the static tests, probably due to increasing ionic strength, which 
would tend to inhibit colloid release and dispersion. 
0.001 
0.01 
0.1
1 
101 
0 2 4 6 8 10 12 14 16 
N2 B and Pu total 
NL(B) N2-9 
NL(B) N2-10 
NL(B) N2-12 
NL(Pu) N2-9 
NL(Pu) N2-10 
NL(Pu) N2-12 
Normalized release (g/m 2) 
time (years) 
NOTE: The cumulative normalized release of the elements B and Pu from replicate tests in the N2 
Series. 
Source: B data from MO0301ANLGNN01.527 [DIRS 161914] and Pu DTN: MO0301ANLGNN02.527 
[DIRS 161916]. 
Figure 13. The Cumulative Normalized Release of the Elements B and Pu in Drip Tests Evaluating 
Defense High-Level Waste Glass Degradation at Argonne National Laboratory

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 87 June 2003 
The experimental data on colloid generation resulting from defense high-level waste glass 
corrosion were used to develop a conceptual model for the rate and evolution of radionuclide 
release, described here, and an expression for use in predicting the rate of radionuclide release, 
described below. The amount of boron released was used as a marker for the amount of glass 
corrosion as B was observed to increase smoothly in the leachate with glass corrosion, and it did 
not become incorporated in alteration phases. 
The normalized release is the radionuclide release normalized with respect to radionuclide 
mass fraction, surface area of the corroding glass, and volume of fluid associated with the glass. 
The relationship presented in Colloid-Associated Radionuclide Concentration Limits: ANL 
(CRWMS M&O 2001 [DIRS 154071]) is: NLi (g/m2) = [(i in ng) / (volume in mL)] * (g/109ng) 
* (106 cm3/m3) / (S/V in m-1) / (fi), where the surface area to volume ratio is the SA/V (surface 
area to volume ratio) of the experiments and the weight fraction (fi) of Pu is 0.01 in the glasses. 
The normalized (to SA) mass loss of Pu, NL(Pu), from the glass was compared to the normalized 
mass loss of B, NL(B), as a function of reaction time; the ratio of the two indicates the quantity 
of Pu released relative to the quantity of glass corroded. In some of the tests, NL(Pu) was 
consistently lower than NL(B) by at least one order of magnitude. Marked decreases from this 
ratio can be attributed in specific tests to an increase in the glass corrosion rate due to secondary 
phase formation as well as destabilization of the colloids (CRWMS M&O 2001 [DIRS 154071], 
Section 6.2.1). The NL(Pu)/NL(B) can be less than 10-3 under solution conditions that inhibit 
colloid stability (CRWMS M&O 2001 [DIRS 154071, Section 6.4.1). 
During the early stages of waste glass corrosion, the glass dissolves and releases components at a 
rate proportional to the rate of corrosion of the waste form. As this occurs, clay colloids nucleate 
in the solution and clay alteration layers form on the surface of the glass. These clay phases, 
which contain embedded radionuclide-bearing phases, also sorb ionic radionuclide species 
and/or colloidal radionuclide-bearing phases. If the ionic strength of the solution is low, the 
colloids are generally stable (see Section 6.3.2.2) and the rate of formation of the 
radionuclide-bearing colloids is proportional to the amount of altered glass (CRWMS 
M&O 2001 [DIRS 154071], Section 6.2.1). 
As the glass alters, the rate of radionuclide-bearing colloids production decreases; this is 
attributed by the investigators to colloid deposition (by sorption) on the fixed clay alteration 
layer. Once the cumulative normalized B release is greater than approximately 1 to 3 g m-2, the 
radionuclide release is controlled by spallation of the clay layer. Figure 14 illustrates the 
observed increases in colloid production due to the onset of spallation. 
Thus, radionuclide release may be viewed as a two-step process: (1) alteration of the glass waste 
form and precipitation of colloids, and (2) erosion of colloid-sized fragments from the alteration 
products (CRWMS M&O 2001 [DIRS 154071], Section 6.2.1). The observed concentrations of 
defense high-level waste glass-derived colloids is discussed in Section 6.3.2, Colloid Stability 
and Concentration.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 88 June 2003 
(a) 
(b) 
(c) 
NOTE: Plutonium Release Rate versus Cumulative Boron Release Plutonium Release Rate 
(calculated for each sampling interval) Versus Cumulative Boron Release: (a) N2-9, 
(b) N2-10, (c) N2-12. The total plutonium release is used, including vessel acid strip. 
Source: Adapted from CRWMS M&O 2001 [DIRS 154071], Figure 29. 
Figure 14. Plutonium Release Rate versus Cumulative Boron Release Plutonium Release Rate

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 89 June 2003 
(d) 
(e) 
(f) 
NOTE: Plutonium release rate (calculated for each sampling interval) versus cumulative 
boron release: (d) N3-9, (e) N3-10, (f) N3-12. The total plutonium release is 
used, including vessel acid strip. 
Source: Adapted from CRWMS M&O 2001 [DIRS 154071], Figure 29. 
Figure 14. Plutonium Release Rate versus Cumulative Boron Release Rate (continued)

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 90 June 2003 
Rate of Colloid Formation from Defense High-Level Waste GlassThe normalized mass 
loss of Pu, NL(Pu), was compared to the normalized mass loss of boron, NL(B), to indicate the 
amount of Pu released relative to the amount of B released, which is stipulated to represent the 
amount of defense high-level waste glass corroded. As indicated in Figure 15 the NL(Pu) is 
consistently lower than the NL(B) by at least one order of magnitude. NL(Pu)/NL(B) decreases 
for the longer duration tests at higher SA/V, up to about 10-3 for conditions which inhibit stable 
colloids. 
10-8 
10-7 
10-6 
10-5 
10-4 
10-3 
10-2 
10-1 
100 
0 200 400 600 800 1000 
202A/2K 
202A/20K 
131A/2K 
131A/20K 
NL(Pu)/NL(B) 
time (days) 
NOTE: Ratio of normalized mass loss of plutonium to normalized mass loss of boron, NL(Pu)/NL(B), 
as a function of test duration (in days) for static corrosion tests on the SRL 202A and SRL 
131A glasses at 2,000 and 20,000/m (T = 90C) 
Source: Ebert 1995 [DIRS 113219], and adapted from Figure 27 of CRWMS M&O 2001 [DIRS 
154071]. 
Figure 15. Ratio of Normalized Mass Loss of Plutonium to Normalized Mass Loss of Boron, NL(Pu)/NL(B) 
Under low ionic strength conditions, the colloids are stable in the fluid and the rate of formation 
of Pu-bearing colloids, dmPu-coll/dt, is proportional to the amount of altered glass, Malt. As the 
glass alters, the rate of radionuclide-bearing colloids production decreases, initially following a 
power-law, attributed to their sorption by the fixed clay alteration layer (CRWMS M&O 2001 
[DIRS 154071], Section 6.4.2). The rate of colloid formation can be described by the 
relationship in Equation 8. 
( ) b 
alt 
Pucoll M a 
dt 
dm - = (Eq. 8)

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MDL-EBS-PA-000004 REV 00 91 June 2003 
The constants, a and b, derived for the various glasses may be a function of the SA/V, leachate 
composition (ionic strength, etc.), colloid composition, or other parameters. Table 13 
summarizes the ranges and bounding values for a and b. 
Table 13. Ranges and Bounds for the Constants, a and b, in Equation 8 
Static-Saturated 
Tests Drip Tests Bounding 
Values 
Constant Low High Low High 
a 8 x 10-12 4 x 10-6 2 x 10-6 5 x 10-6 10-4 
b 3 8 0.3 1.7 1 
Source: Data from CRWMS M&O 2001 [DIRS 154071], Section 6.4.2. 
At the high ionic strengths encountered in certain static tests, there was no correlation observed 
between Pu and B production rates since the quantity of colloids was very low. In the drip tests, 
ionic strength remained low because EJ-13 water was periodically injected. 
Once the cumulative B release is greater than approximately 1 to 3 g m-2, the radionuclide 
release is controlled by spallation of the clay layer. Thus, radionuclide release is a two-step 
process: (1) alteration of the glass waste form and precipitation of colloids and (2) erosion of 
colloid-sized fragments from the alteration products. 
Release of colloids due to spallation is given by the derived relationship: 
alt 
Pu M 
dt 
dm coll . = (Eq. 9) 
where coll Pu dm is the mass release of Pu suspended as colloidal particulates and . is a parameter 
that depends on, among other things, the mechanical condition of the altered waste form, the 
water flow rate over the waste form, and the water chemistry (CRWMS M&O 2001 [DIRS 
154071], Section 6.4.2). An empirical bound for . is 10-4 d-1. 
Rate of Colloid Formation from Commercial SNFThe normalized mass loss of Pu, NL(Pu), 
was compared to the normalized mass loss of technetium, NL(Tc), to indicate the amount of Pu 
released relative to the amount of Tc released, which is stipulated to represent the amount of 
SNF corroded. It was noted that the reaction of SNF under unsaturated drip test conditions does 
not exhibit a correlation between the rate of Pu-bearing colloid formation and the corrosion of 
spent fuel (see Figure 16). The scattered data indicating Pu release rate versus Tc release rate 
(which are proportional to the NL(Pu) and NL(Tc), respectively) were bounded by assuming 
conservatively that NL(Pu)/NL(Tc) is equal to 10-5 d-1.

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MDL-EBS-PA-000004 REV 00 92 June 2003 
10-11 
10-10 
10-9 
10-8 
10-7 
10-6 
0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 
ATM-103 
ATM-106 
10e-5*Cum Rel Tc 
Pu Release Rate (day -1) 
Cumulative Fractional Release of Tc 
NOTE: The fractional release rate of Pu as a function of cumulative fractional Tc release for the 
ATM-103 and ATM-106 high-drip-rate tests. The solid line is the conservative bound based 
upon a constant of 10-5 d-1 (Figure 30 from CRWMS M&O 2001 [DIRS 154071]). 
Figure 16. Fractional Release Rate of Pu as a Function of Cumulative Fractional Tc Release for the 
ATM-103 and ATM-106 High-drip-rate Tests 
Calculation of Quantity and Rate of Production of Irreversibly Attached Radionuclides 
Parameters used to calculate mobilized radionuclide quantities and rates of production are listed 
in Table 14. After the quantities of total mobilized radionuclides are calculated, they are 
distributed between radionuclides irreversibly attached to colloids, dissolved (aqueous) 
radionuclides, and radionuclides co-precipitated in immobile secondary phases. Since the 
experimental evidence indicates that most waste form colloids are radionuclides and/or 
radionuclide-bearing phases irreversibly associated with smectite colloids, this fraction is given 
as the difference between the dissolved radionuclides and the total radionuclides mobilized by 
the waste degradation time step: 
RNcoll,irrev + RNlayer,irrev = RNmobRNdissRNsecondaryphase (Eq. 10) 
The irreversibly attached radionuclides are in turn distributed between the clay layers on altered 
defense high-level waste glass and clay colloids produced from both defense high-level waste 
glass and SNF; the aqueous radionuclides are available for reversible sorption onto colloids. 
If the cumulative release of boron is less than 1 g m-2, then the following relationship is invoked 
to calculate the quantity of radionuclides irreversibly attached to colloids produced for that time 
step. The equation for calculating the mass of radionuclides is:

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MDL-EBS-PA-000004 REV 00 93 June 2003 
Mass of irreversibly attached RN = a * (Bcum)-b (Eq. 11) 
where Bcum represents the mass of defense high-level waste glass degraded and a and b are 
empirically-derived constants. 
Table 14. Parameters Used in Description of Alternative Model 
Parameter Description Value /Range/ 
Distribution Source 
Binv, Tcinv, 
Puinv, Aminv 
Masses of B, Tc, and RNs in unaltered 
waste form during time step 
-------- Would be calculated by 
TSPA-LA model 
Bmob, Tcmob, 
Pumob, Ammob 
Masses of B and RNs mobilized in WFdeg 
during time step 
-------- Would be calculated by the 
TSPA-LA model 
Bcum Cumulative mass of B mobilized in WFdeg 
for all previous time steps 
-------- Would be calculated by the 
TSPA-LA model 
Malt Amount of a altered glass -------- CRWMS M&O 2001 [DIRS 
154071] 
a Empirically derived constant used in 
expression for precipitated smectite colloids 
10-4 (bound) CRWMS M&O (2001 [DIRS 
154071]) 
b Empirically derived constant used in 
expression for precipitated smectite colloids 
1 (bound) CRWMS M&O (2001 [DIRS 
154071]) 
. Empirically derived constant used in 
expression for spalled smectite colloids 
10-4 (bound) CRWMS M&O (2001 [DIRS 
154071]) 
NOTE: RN = radionuclide; WF = waste form. 
If Bcum is greater than 3 g m-2, then the second model is invoked to calculate the quantity of 
radionuclides irreversibly attached to colloids formed from spallation of the alteration clay layer. 
The equation for calculating radionuclide mass mobilized due to spallation is: 
Mass of irreversibly attached spalled RN = . * Bcum (Eq. 12) 
where . is an empirically-derived constant. 
If Bcum is between 1 and 3, then either the first or second is chosen randomly (0.5 probability). 
In the case of SNF, the quantity of radionuclides irreversibly attached to colloids was bounded 
according to the expression: 
Mass of irreversibly attached RN = (Tcmob / Tcinv) * 10-5 (Eq. 13) 
Assessment of Rate-of-Colloid-Generation ModelThis alternative abstraction takes into 
account many of the results from the Argonne National Laboratory waste form corrosion 
experimental program as well as models derived from them. It incorporates an analytical 
approach that would couple the waste form degradation calculations by the TSPA-LA model 
more closely to the process model derived from the experiments.

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MDL-EBS-PA-000004 REV 00 94 June 2003 
While it takes advantage of the most complete information available on waste form corrosion, at 
the same time it is tailored closely to the experimental conditions and configurations. There are 
aspects of the experiments that may make them inappropriate to apply to a more general case. A 
possible example is the rate of spallation of the clay layer from altered defense high-level waste 
glass, which may be due to the specific dynamics surrounding the impacts of the drips falling on 
the sample in the defense high-level waste glass drip tests (recall that no spallation was observed 
in the static tests (CRWMS M&O 2001 [DIRS 154071], Section 6.2.1). If the corroded contents 
of a failed waste canister assume a geometry that does not allow dripping of water onto the 
alteration products, spallation may not occur. If dripping does occur, of course, spallation may 
be a viable process, and an analysis of colloid production and transport would have to consider it. 
6.4.3 Mechanisms of Colloid Generation in Commercial Spent Nuclear Fuel 
This alternative model, described in Buck 2003 [DIRS 163117], investigates the processes 
whereby colloid generation at, and mobilization from, the surface of degrading waste is primarily 
related to flow rate at the waste surface. The supporting concepts and data from the peerreviewed 
literature that support this alternative model were developed in the context of 
deposition and remobilization of existing colloids under conditions of moderate to significant 
fluid flow. Although it is possible that relatively high flow conditions could prevail or flow 
transients occur at some point, low flow conditions are expected to prevail over the regulatory 
period, so that colloid entrainment may not occur. 
Under specific experimental environments, a flow rate dependence on colloid release has been 
observed (Buck 2003 [DIRS 163117]), although a full explanation for these empirical 
relationships has not yet been developed. In this alternative model flow rate dependence of the 
entrainment and mobilization of waste form colloids would be determined. In addition, the 
influences of fluid chemistry and of the actual phases formed and their physical association in a 
model waste form system would be investigated. This model will allow quantification of 
changes in particle release under different flow rates, fluid chemistries, and particle-particle 
interaction scenarios. 
Assessment of the Colloid Generation Mechanisms ModelAlthough transport of colloids 
within the waste package may be negligible, colloid transport could be initiated and sustained if 
the system is subjected to sufficient physical or chemical perturbations. Understanding the 
effects of these perturbations regarding colloid mobilization in the waste package is important to 
understanding the potential impact of colloids on dose at Yucca Mountain (see also 
Section 6.4.1). However, this alternative colloid generation model is not considered in detail, 
and an assessment of the potential effects on the dose calculations that might result from its 
inclusion in the TSPA-LA model was deemed unnecessary; for example, seepage water flow 
rates needed to drive the component processes of this model are not anticipated in the repository 
environment (see Section 1.1). 
6.5 MODEL FORMULATION FOR BASE-CASE ASSESSMENT 
This section describes in detail the methodology used to incorporate the various model elements 
formulated in this model analysis into a colloids source term abstraction (i.e., a simplified model 
intended to retain the important principles and features of the analyses) for implementation in the

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MDL-EBS-PA-000004 REV 00 95 June 2003 
TSPA-LA model. The logic and parameters implemented in the TSPA-LA model are provided, 
although specific programming details are not. 
Figure 17 provides an overview of the model methodology with cross-references to the 
underlying model elements developed in Section 6. Figure 17a illustrates how colloids are 
modeled in the waste package (Section 6.5.1), and Figure 17b in the drift (Section 6.5.2). 
Parameters used in the abstraction are described in Table 16. Sections 6.5.1 and 6.5.2 present the 
details of the abstraction, and Figures 18 through 21 illustrate the logic and flow of the 
abstraction approach. 
At each time step executed in the TSPA-LA calculations, the colloid model uses characteristics 
of the water in the waste package (ionic strength, pH, and dissolved radionuclide concentrations) 
to describe the formation and behavior of colloids and the distribution of the radionuclides in the 
waste package. The elements considered and incorporated into the calculations are Pu, Am, Th, 
Pa, and Cs. Three types of colloids are considered in the modelwaste form, iron 
oxyhydroxide, and seepage water/groundwater. Waste form colloids generated from defense 
high-level waste glass are included in the model, but colloids from commercial and DOE SNF 
are not. Colloids formed from the defense high-level waste glass and the naturally occurring 
groundwater colloids are stipulated to be smectite colloids. The iron oxyhydroxide colloids are 
formed during corrosion of steel waste package materials. 
The stability of colloids is defined by ionic strength and pH, with separate relationships for 
smectite colloids (Section 6.3.2.2, Figure 17a and 17b, Table 16) and iron oxyhydroxide colloids 
(Section 6.3.2.3, Figure 17a and 17b, Table 16). At each time step, the values of I and pH of the 
waste package solution are used as input to determine whether or not colloids are stable. For 
both types of colloids, when unstable, a low (non-zero) limit of colloid concentration is used 
(Figure 17 and Table 16 for smectite; Table 16 for iron oxyhydroxide). Within the stability zone 
for defense high-level waste glass smectite colloids, a function is used that relates Pu and colloid 
concentrations to ionic strength (Figures 8, 9, and 17). For iron oxyhydroxide colloids upper and 
lower limits of ionic strength are used in the definition of stability (Figures 7 and 17; Table 16); 
for groundwater smectite colloids, an upper limit of colloid concentration is used (Figures 12 
and 17; Table 16). 
Reversible sorption onto the smectite colloids for each of the five considered radionuclides is 
modeled (Section 6.3.3.1). For iron oxyhydroxide colloids, irreversible sorption of Pu and Am is 
also included (Section 6.3.3.2). Within the waste package, the major fractions of total Pu and 
Am available at each time step are sorbed to stationary corrosion products, a smaller fraction to 
colloids, and a smaller fraction remains dissolved. Further, a high percentage of the sorbed Pu is 
irreversibly sorbed onto colloids and stationary corrosion products; a small percentage is 
reversibly sorbed. Distribution coefficients (Kd values) for each of the radionuclides are used for 
both smectite and iron oxyhydroxide colloids (Table 16). 
The model calculates the concentration of dissolved radionuclides, the concentration of Pu and 
Am embedded in defense high-level waste glass smectite colloids, the concentration of 
radionuclides sorbed reversibly onto all colloids, the concentration of radionuclides sorbed 
irreversibly onto iron-hydroxide colloids, and the mass concentration of each colloid type 
(Figure 17a).

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MDL-EBS-PA-000004 REV 00 96 June 2003 
The colloid and radionuclide concentration values along with the ionic strength and pH of 
solution serve as source term for the invert. The TSPA-LA model calculates the ionic strength 
and pH of the resulting solution of the waste package effluent mixed with the invert water (this is 
not a component of the colloid model). Based on the new values of ionic strength and pH in the 
invert, the model determines colloid stabilities at the new fluid composition and redistributes the 
reversibly sorbed radionuclides and dissolved radionuclides based on the distribution coefficients 
and the total mass of each type of colloid (Figure 17b). All colloids flow unimpeded through the 
invert to the unsaturated zone. The irreversibly sorbed radionuclides do not get redistributed. 
6.5.1 Waste Form Abstraction Implementation in Total System Performance Assessment 
License Application 
The abstraction uses a set of input parameters for the TSPA-LA model, listed and described in 
Table 1 in Section 4.1. Input parameters have been taken from the Argonne National Laboratory 
colloid-related report (CRWMS M&O 2001 [DIRS 154071]) and DTNs: LL000905312241.018 
[DIRS 152621] and LL991109751021.094 [DIRS 142910]; others have been extracted from 
available project documents and the scientific literature. 
In addition, the abstraction requires parameters calculated by the TSPA-LA model as output 
from in-package chemistry, solubility limits, and near-field chemical environment calculations: 
CRN,diss, Iwp, and pHwp (see Table 16) (Dissolved Concentrations of Radioactive Elements, BSC 
2003 [DIRS 163152]; Engineered Barrier System: Physical and Chemical Environment Model, 
BSC 2002 [DIRS 160315], analysis described in Section 1.2.2). 
The concentrations of colloids and colloid-associated radionuclides were calculated on the basis 
of abstractions of the laboratory and field observations and chemical principles described in 
Section 6.3. A stepwise approach was taken in the abstraction, and each step is set out below 
with a flow diagram and logic statements that describe the abstraction step. Parameters are 
defined in Table 16. 
6.5.1.1 Waste Form (Smectite) Colloids 
Table 1 lists waste form colloid-related input parameters used in the abstraction. 
Corroborating/supporting data and information used to develop the parameters are listed in 
Table 2.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 97 May 2003 
NOTE: RN = radionuclide; SW = seepage water; DHLWG = defense high-level waste glass. 
Figure 17a. Processes Within the Waste Package 
To 
(invert) 
See Figure 9 See Figure 13 See Figure 5 
See Figure 7 
See Figure 5 See Figure 12 
See Figure 7 
CO 
LLOIDS IN WASTE PACKAGE 
COLLOID STABILITY 
(In-package I, pH) COLLOID CONCENTRATION 
WASTE FORM CORROSION GROUNDWATER 
Sum of colloidassociated 
radionuclide 
concentrations 
Sum of colloid 
mass 
concentrations 
In-package 
ionic strength 
and pH
To 
Drift 
(invert) 
0.00 
0.10 
0.20 
0.30 
0.40 
0.50 
0.60 
0.70 
0.80 
0.90 
1.00 
1.10 
0.0010 0.0100 0.1000 1.0000 10.0000 100.0000 1000.0000 
Concentration of Colloids (mg/L) 
Probability 
Qualified data 
Corroborative Data 
Uncertai nty 
distribution 
1 x 10- 
11 
1 x 10-7 
1 x 10-8 
1 x 10-9 
1 x 10- 
10 
0.00 0.01 0.02 0.03 0.04 0.05 0.06 
Ionic Strength (M) 
CPu,, coll (M)
CPu = function (STcoll, wf, is) 
Colloid Zone of Instability 
Concentrations of 
Corrosion Colloids; 
irreversibly sorbed 
Pu, Am; and 
reversibly sorbed Pu, AM, 
Pa, Th, Cs 
Concentrations of 
GW Colloids and 
reversibly sorbed Pu, 
Am, Pa, Th, Cs 
Concentrations of 
DHLWG Colloids; 
embedded Pu, Am; 
and reversibly 
sorbed Pu, Am, Pa, 
Th, Cs 
[Colloids] total (ppm) 
0E+0 
1E-9 
2E-9 
3E-9 
4E-9 
5E-9 
6E-9
0 50 100 150 200 250 300 350 
Time(days) 
0.0 
1.0 
2.0 
3.0 
4.0 
5.0 
Pu-col l oids (fi l t) Total Colloids (DLS) 
[Pu colloid ] (M) 
[Colloids] total (ppm) 
0E+0 
1E-9 
2E-9 
3E-9 
4E-9 
5E-9 
6E-9
0 50 100 150 200 250 300 350 
Time(days) 
0.0 
1.0 
2.0 
3.0 
4.0 
5.0 
Pu-col l oids (fi l t) Total Colloids (DLS) 
[Pu colloid ] (M) 
In-package 
Corrosion Colloids 
(sampled) 
Ionic Strength (M) 
0.00 0.01 0.02 0.03 0.04 0.05 0.06 
Concentration (mg/L) 
50 
0.05 
0.001 
Iron-(hydro)oxide colloid 
Zone of Instability 
Outside of Sampled Range 
Outside of Sampled Range 
In-package 
Corrosion Colloids 
(sampled) 
Ionic Strength (M) 
0.00 0.01 0.02 0.03 0.04 0.05 0.06 
Concentration (mg/L) 
50 
0.05 
0.001 
Iron-(hydro)oxide colloid 
Zone of Instability 
Outside of Sampled Range 
Outside of Sampled Range 
See Figure 24 See Figure 5 
See Figure 20 
See Figure 22 
See Figure 27 See Figure 20 
RADIONUCLIDE SORPTION 
(Reversibly and Irreversibly 
Sorbed RNs) 
Colloidassociated 
radionuclide 
concentrations 
Colloid mass 
concentrations 
Drift 
SEEPAGE WATER 
SW 
See Figure 9 See Figure 3 See Figure 5 
See Figure 5 See Figure 12 
Am, 
See Figure 7

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 98 May 2003 
NOTE: WP = waste package; RN = radionuclide; SW = seepage water; HLW = high-level waste; UZ = unsaturated zone. 
Figure 17b. Processes within the Drift (Invert) 
From WP: 
 Colloid 
associated 
RNs 
 Colloid mass 
concentrations 
Ionic strength, pH of 
Invert Wicking 
Scenario 
Ionic strength, pH of 
WP Surface 
Dripping Scenario 
Ionic strength, pH of 
WP Leakage 
Scenario 
Corrosion 
Colloids 
Waste Form 
Colloids 
Seepage 
Water 
Colloids 
Concentration of 
corrosion colloids; 
reversibly sorbed 
Pu, Am, Pa, Th, 
Cs; and irreversibly 
sorbed Pu, Am 
Concentrations of 
HLW glass 
colloids; reversibly 
sorbed Pu, Am, 
Pa, Th, Cs; and 
embedded Pu, Am 
Concentration of 
SW colloids and 
reversibly sorbed 
Pu, Am, Pa, Th, Cs 
 Sum of colloidassociated 
radionuclide 
concentrations 
 Sum of colloid 
mass 
concentrations 
 Dissolved 
radionuclide 
concentrations 
WITHIN DRIFT (INVERT) 
To 
UZ 
or or 
IN-DRIFT FLUID 
CHEMISTRY 
COLLOID STABILITY 
(in-drift I, pH) 
SORBED 
RADIONUCLIDE 
CONCENTRATIONS

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 99 June 2003 
Step 1a. The radionuclides Pu and Am are modeled in Step 1a (Figure 18a) as embedded within 
waste form colloids, which are produced from corrosion of defense high-level waste glass. The 
concentrations are defined by ionic strength, based on experimental observations (Sections 
6.3.1.1 and 6.3.2.4). 
Input Iwp 
IF I = Ihi-thresh,coll,wf 
THEN CRNcoll,wf.embed = CRNcoll,wf,embed,min 
ELSE 
IF (I > Ilo-thresh,coll,wf) AND (I < Ihi-thresh,coll,wf) 
THEN CRNcoll,wf,embed = function(STcoll,wf,is) 
ELSE CRNcoll,wf,embed = CRNcoll,wf,embed,.max 
function(STcoll,wf,is): -2.50E-6  I +1.25E-7 (see Equation 4, Section 6.3.2.4) 
Figure 18a. Flow Chart and Logic Statements: Effect of Ionic Strength on the Concentration of Waste 
Form Colloid-Associated Radionuclides Generated Defense High-Level Waste Glass 
Degradation Based on Experiments Conducted at Argonne National Laboratory (see 
Figure 9) 
Ihi-thresh,coll,wf and Ilo-thresh,coll,wf are threshold values of the ionic strength of the fluid in the waste 
package used to calculate the concentration of embedded Pu used in the abstraction. (Am is 
calculated as the product of the Pu concentration times the Am/Pu ratio in the inventory, which is 
determined at each time step of the TSPA-LA model calculations. Stability of the defense high- 
CRN coll, wf, embed = CRN coll, wf, embed, max 
CRN coll, wf, embed = function (STcoll, wf, is) 
CRN coll, wf, embed = CRN coll, wf, embed, min 
Ionic Strength and pH 
from TSPA-LA 
Calculation (Iwp) 
Ionic Strength (Iwp) 
and pH from TSPA-LA 
Calculation

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 100 June 2003 
level waste glass-derived colloids is determined in Step 1b. Colloid mass concentrations are 
calculated from the amount of Pu embedded in smectite waste form colloids in Step 1c. 
Step 1b. The stability of waste form colloids from defense high-level waste glass is determined 
on the basis of the fluid ionic strength and pH (Figure 18b), based on known properties of 
smectite colloidal suspensions (Section 6.3.2.2). 
Input pHwp 
IF (Iwp = Ihi-thresh,coll,wf) OR (I = function(STcoll,wf,pH)) 
THEN CRNcoll,wf,embed = CRNcoll,wf,embed,min 
function(STcoll,wf,pH): pH/200 
Figure 18b. Flow Chart and Logic Statements: Effect of pH and Ionic Strength on Waste Form Colloid- 
Associated Radionuclide Concentration Based on Stability Behavior of Montmorillonite 
Colloids (see Figure 5) 
The Ihi-thresh,coll,wf and Ilo-thresh,coll,wf parameters are the same threshold values of the ionic strength 
of the fluid in the waste package used to determine Pu concentration (Step 1a). They are used 
here to determine, along with pH, whether or not the colloids are stable. These threshold values 
may vary due to specific chemical and environmental conditions and are therefore sampled over 
a range (Table 16). 
Step 1c. Calculation of the mass concentration of waste form colloids from defense high-level 
waste glass (Figure 18c) is done on the basis of experimental observations (Section 6.3.1.1, 
Figure 3, Equation 1).
CRNcoll, wf, embed= CRNcoll, wf, embed, min 
Iwp > Ihi-thresh, coll, wf 
OR 
Iwp > function (STcoll, wf, pH)

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 101 June 2003 
Mcoll, wf, both = Mcoll, wf, both, max 
CRN coll, wf, embed 
CRN coll, wf, embed, max 
1d 1b 
Mcoll,wf,both = Mcoll,wf,both,max  CRNcoll,wf,embed  CRNcoll,wf,embed,max 
Figure 18c. Flow Chart and Logic Statements: Determination of Mobile Mass Concentration of Waste 
Form Colloids Mcoll,wf,both) 
The colloid mass concentration is related to the embedded Pu concentration (Equation 1). With 
reference to Equation 1, Mcoll,wf,both,max is the maximum colloid mass concentration corresponding 
to the maximum Pu concentration, CRNcoll,wf,embed,max. It is an intermediate result based on the 
experimental data showing the relationship between embedded Pu concentration and colloid 
mass concentration (see DTNs, listed in Table 16). Mcoll,wf,both is a parameter that represents the 
total mass concentration of defense high-level waste glass colloids with both embedded and 
reversibly sorbed radionuclides (Table 16). 
Step 1d. The calculation of the concentration of radionuclides (Pu, Am, Th, Pa, Cs) reversibly 
sorbed on waste form colloids from defense high-level waste glass (Section 6.3.3.1, Figure 18d) 
is based on the mass concentration of waste form colloids, Kd values describing the distribution 
of radionuclides between the fluid and smectite colloids, and the dissolved concentration of 
radionuclides as calculated by the TSPA-LA model. 
CRNcoll,wf,rev = CRNdiss  Kd,RN,coll,wf  Mcoll,wf,both x 1E-6 
Figure 18d. Flow Chart and Logic Statements: Sorption of Radionuclides on Waste Form Colloids 
The CRNdiss is the concentration of radionuclide RN, determined by the TSPA-LA model as 
output from the solubility concentration model, that is used as an input to the colloid abstraction. 
Kd,RN,wf is a parameter derived from several sources (see Tables 6-10) and is an equilibrium 
sorption coefficient used to approximate the partitioning of dissolved radionuclide RN 
between colloids and fluid. 
6.5.1.2 Corrosion-Generated (Iron Oxyhydroxide) Colloids 
Table 1 lists waste form colloid-related input parameters used in the abstraction. 
Corroborating/supporting data and information used to develop the parameters are listed in 
Table 2.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 102 June 2003 
Step 2a. The stability and mass concentration of iron oxyhydroxide colloids formed as a result 
of the corrosion of waste package components is determined on the basis of the fluid ionic 
strength and pH (Section 6.3.2.3, Figures 17a and 18e). 
IF 
BEGIN 
(I > Ihi-thresh,coll,FeOx) 
OR ((I = Ilo-thresh,coll,FeOx) 
AND (I > function(STcoll,FeOx,pHhi)) OR (I > function(STcoll,FeOx,pHlo))) 
OR ((I < Ilo-thresh,coll,FeOx) AND (function(STcoll,FeOx,pHint))) 
END 
THEN 
Mcoll,FeOx = Mcoll,FeOx,min 
ELSE 
Mcoll,FeOx = Mcoll,FeOx,sampled 
function(STcoll,FeOx,pHhi): -0.02  pH + 0.17 
function(STcoll,FeOx,pHlo): +0.02  pH0.17 
function(STcoll,FeOx,pHint) (boolean): ((pH = 8) AND (pH = 9)) 
Figure 18e. Flow Chart and Logic Statements: Effect of Ionic Strength and pH on Stability of Iron 
Oxyhydroxide Colloids (see Figure 7) 
Mcoll, FeOx =Mcoll, FeOx, sampled 
Ionic Strength 
and pH from 
TSPA-LA 
calculation 
Step 2a Iron Oxyhydroxide Colloids  Effect of pH and Ionic Strength on Stability and Concentration 
AND

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 103 June 2003 
The Ihi-thresh,coll,wf,FeOx and Ilo-thresh,coll,FeOx are threshold values of the ionic strength of the fluid in 
the waste package used to calculate the stability and concentration of corrosion-generated 
colloids, similar to the waste form colloid stability determination in Step 1a. STcoll,FeOx,pHhi and 
STcoll,FeOx,pHlo are functions which incorporate threshold values of pH for determining the 
stability and concentration of corrosion-generated colloids in conjunction with the ionic strength 
thresholds. 
Step 2b. In this step two types of sorption are modeled, irreversible sorption of Pu and Am onto 
iron oxyhydroxide corrosion colloids and fixed corrosion products (Section 6.3.3.2, Figure 18f); 
and reversible sorption of Pu, Am, Pa, Th, and Cs onto iron oxyhydroxide colloids (Section 
6.3.3.1). The distribution of irreversibly sorbed Pu and Am onto fixed and colloidal substrates is 
performed in the TSPA-LA model. It is a kinetic model that is described in EBS Radionuclide 
Transport Abstraction (BSC 2003 [DIRS 163935]). Parameters used include specific surface 
area (SA), the sampled corrosion colloid mass concentration (Mcoll,FeOx,sampled), concentration of 
dissolved radionuclides (CRNdiss), and flux out ratio (FRN). 
Reversible sorption is calculated from the sampled mass concentration of corrosion colloids, Kd 
values describing the distribution of radionuclides between the fluid and iron oxyhydroxide 
colloids, and the dissolved concentration of radionuclides as calculated by the TSPA-LA model. 
CRNcoll,FeOx = CRNdiss  Kd,RN,FeOx  Mcoll,FeOx x 1E-6 
Figure 18f. Flow Chart and Logic Statements: Sorption of Radionuclide RN on Iron Oxyhydroxide 
Colloids 
In Step 2b the irreversibly sorbed Pu and Am are determined, along with reversibly sorbed Pu, 
Am, Pa, Th, and Cs. The CRNdiss is the concentration of radionuclide RN, determined by the 
TSPA-LA model as output from the solubility concentration model, which is used as an input to 
the colloid abstraction. Kd,RN,FeOx is a parameter derived from several sources (see Tables 6-10) 
and is an equilibrium sorption coefficient used to approximate the partitioning of dissolved 
radionuclide between colloids and fluid. The 1E-6 portion of the relationship designates a 
correction factor to accommodate differences in units among the various parameters. 
  4 
4 , , , 
CRN coll, FeOx, rev = CRN diss Kd, RN, FeOx Mcoll, FeOx 
CRN coll FeOx irrev =(SA; Mcoll FeOx, sampled;CRN diss; 
parameters internal to TSPA-LA 
2a 
Step 2b Iron Oxyhydroxide Colloids  Sorption of Radionuclides 
FRN)

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 104 June 2003 
6.5.1.3 Seepage Water (Smectite) Colloids 
Seepage water/groundwater colloid-related input parameters used in the abstraction are listed in 
Table 16. All information used to develop the parameters is listed in the table, including 
corroborative information. 
Step 3a. The mass concentration of seepage water colloids is calculated on the basis of fluid 
ionic strength in Step 3a (Sections 6.3.2.2 and 6.3.2.5, Figure 18g). 
IF Iwp= Ihi-thresh,coll,gw 
THEN Mcoll,gw = Mcoll,gw,min (1E-6 mg/L) 
ELSE IF (Iwp < Ihi-thresh,coll,gw) 
THEN Mcoll,gw = Mcoll,gw,sampled (distribution in Table 5) 
Figure 18g. Flow Chart and Logic Statements: Effect of Ionic Strength on Mass Concentration of 
Seepage Water Colloids 
Ihi-thresh,coll,gw is a threshold value of the ionic strength of the fluid in the waste package used to 
calculate the concentration of groundwater colloids (stability is determined in Step 3b). It is 
identical to the upper threshold used for determining stability and concentration of waste form 
colloids, since both waste form and groundwater colloids are modeled as smectite. Groundwater 
colloids are modeled as present in groundwater seeping into the drift and as entering a breached 
waste package. Colloid concentrations are sampled if the ionic strength is below Ihi-thresh,coll,gw 
(see Section 6.3.2.5). This ionic strength threshold value may vary due to specific chemical and 
environmental conditions and therefore is sampled over a range. The groundwater colloid 
concentration range (and distribution) is an intermediate parameter derived from several sources 
containing groundwater concentration data vs. ionic strength from the Yucca Mountain vicinity 
and elsewhere (Sections 6.3.1.4 and 6.3.2.5). 
GoldSi 
Mcoll, gw = Mcoll, gw, min 
I >Ihi-thresh, coll, gw Mcoll, gw = Mcoll, gw, sampled 
3b Yes 
No 
Step 3a Seepage Water Colloids  Effect of Ionic Strength on Mobile Mass 
Ionic Strength 
and pH from 
TSPA-LA 
calculation 
wp I

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 105 June 2003 
Step 3b. The stability of groundwater colloids is determined in Step 3b on the basis of the fluid 
ionic strength and pH (Figure 18h), based on known properties of smectite colloidal suspensions 
(Section 6.3.2.2). 
gw 
IF (I = Ihi-thresh,coll,gw) OR (I = function(STcoll,wf,pH)) 
THEN Mcoll,gw = Mcoll,gw,min 
function(STcoll,wf,pH): pH/200 
Figure 18h. Flow Chart and Logic Statements: Effect of pH and Ionic Strength on Groundwater Colloids 
Stability Based on Stability Behavior of Montmorillonite Colloids 
Ihi-thresh,coll,gw is the same upper threshold value of the ionic strength of the fluid in the waste 
package used to determine Pu concentration in Step 1a. It is used here with pH to determine the 
stability of the smectite groundwater colloids. This threshold value may vary due to specific 
chemical and environmental conditions and is therefore sampled over a range (Table 16). 
Step 3c. The concentrations of radionuclides (Pu, Am, Th, Pa, Cs) reversibly sorbed on 
groundwater colloids are calculated in Step 3c (Figure 18i), based on the mass of groundwater 
colloids, Kd values describing the distribution of radionuclides between the fluid and 
montmorillonite, and the dissolved concentration of radionuclides within the waste package as 
calculated by the TSPA-LA model. 
CRNcoll,gw = CRNdiss  Kd,RN,coll,gw  Mcoll,gw x 1E-6 
Figure 18i. Flow Chart and Logic Statements: Radionuclide Sorption on Groundwater Colloids 
The CRNdiss is the concentration of radionuclide RN, determined by the TSPA-LA model as 
output from the solubility concentration model, that is used as an input to the colloid abstraction.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 106 June 2003 
Kd,RNcoll,gw is a parameter derived from several sources (see Tables 6-10) and is an equilibrium 
sorption coefficient used to approximate the partitioning of dissolved radionuclide between 
colloids and fluid. The 1E-6 portion of the relationship designates a correction factor to 
accommodate differences in units among the various parameters. 
6.5.1.4 Outputs from the Waste Package to the Drift 
In Steps 1 through 3 the total colloid-associated radionuclide concentrations, total colloid mass 
concentrations and the remaining radionuclide concentrations in the fluid were calculated for 
waste form colloids derived from defense high-level waste glass (Step 1), colloids derived from 
the corrosion of the waste package interior (Step 2), and seepage water/groundwater colloids that 
entered the waste package. In Step 4 these quantities are passed from the waste package interior 
to the drift environment. 
Step 4. Outputs from the waste package, which are also inputs to the drift, are colloid-associated 
radionuclide concentrations and colloid mass concentration (Figure 17a). 
The colloid-associated radionuclide source term is calculated in Step 4 by passing to the invert 
the contributions to the source term from Steps 1d, 2b, and 3c (Figure 18j). 
Figure 18j. Flow Chart and Logic Statements: Transfer of Colloid-associated Radionuclide Source Term 
to Invert 
The radionuclide component of the source term is made up of individual radionuclide mass 
concentrations embedded in and reversibly attached to waste form (smectite) colloids 
(CRNcoll,wf,embed and CRN,wf,rev), irreversibly and reversibly attached to corrosion-generated iron 
oxyhydroxide colloids (CRNcoll,FeOx,irrev and CRNcoll,FeOx,rev), and reversibly attached to groundwater 
(smectite) colloids (CRNcoll,gw). 
The colloid component of the source term is the sum of the mass concentrations of the waste 
form colloids (Mcoll,wf,both; both signifies the inclusion of all smectite waste form colloids with 
embedded radionuclides, or reversibly associated with radionuclides, or both); the iron 
Mcoll, wf, both 
CRN coll = CRN coll, wf, embed 
+CRN coll, wf, rev 
+CRN coll, FeOx, irrev 
+CRN coll, FeOx, rev 
+CRN coll, gw Transport 
to Invert 
, 
,
,
, , 
Mcoll Mcoll, FeOx, both 
Mcoll, gw 
CRN coll, wf, rev 
CRN coll, FeOx, irrev 
CRN coll, FeOx, rev 
CRN coll, gw Waste-form Colloids 
Waste-form Colloids 
Reversible RN 
Embedded RN 
Iron-(hydr)oxide Colloids 
Reversible RN 
Iron-(hydr)oxide Colloids 
Irreversible RN 
Groundwater Colloids 
Reversible RN 
1d 
1d 
2b 
2b 
3c 
Step 4 Colloidal Radionuclide Source Term in Waste Package

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 107 June 2003 
oxyhydroxide corrosion-generated colloids (Mcoll,FeOx,both; both signifies that all corrosiongenerated 
iron oxyhydroxide colloids irreversibly or reversibly associated with radionuclides, or 
both, are included); and the smectite groundwater colloids. 
6.5.2 In-Drift Abstraction Implementation in Total System Performance Assessment 
License Application 
6.5.2.1 In-Drift Colloid Stability and Mass Concentrations 
Step 5 incorporates the outputs from the waste package in Step 4 with the invert fluid properties, 
ionic strength (Iinv) and pH (pHinv), from TSPA-LA calculations. 
Table 1 lists in-drift seepage water/groundwater colloid-related input parameters (qualified data) 
used in the abstraction. Corroborating/supporting data and information used to develop the 
parameters are listed in Table 2.. 
Step 5. The primary function of Step 5 is incorporation of the invert fluid chemical properties 
and the calculation of resulting stabilities and mass concentrations of colloids entering the invert 
fluid from the waste package as shown in Figure 19. 
Figure 19. Inputs to Drift from Waste Package 
The Iinv and pHinv are inputs calculated by the TSPA-LA model (in-drift environment 
calculations) (BSC 2002 [DIRS 160315], analysis described in Section 1.2.2). The 
concentrations of colloids and colloid-associated radionuclides within the drift are calculated on 
the basis of abstractions of the laboratory and field observations and chemical principles 
described in Section 6.3, with methods similar to those used to determine radionuclide and 
colloid concentrations within the waste package (these calculations are described in Section 6.5.1 
and illustrated in Figures 18a through 18e and 18g through 18i). A stepwise approach was taken 
in the abstraction, and each step is set out below with a flow diagram and logic statements that 
describe the abstraction step. Parameters are defined in Table 16. 
Stability 
and Mass 
Calculations 
coll wf , both 
, 
, wf, embed 
, In-Drift 
Fluid 
Chemistry 
(I, pH) from 
TSPA-LA 
Calculation 
Stability 
and Mass 
Calculatio 
In-Drift Fluid 
Chemistry 
(Iinv, pHinv) 
from 
TSPA-LA 
Calculation M
Mcoll , gw 
, 
Mcoll FeOx , both 
C
C
CRN coll FeOx , rev , 
RN coll , gw 
RN coll wf 
wf CRN coll , , rev 
CRN coll , FeOx , irrev 
Stability and 
Mass 
Calculation 
From 
WP

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 108 June 2003 
In the TSPA-LA model calculations, the colloids with embedded and sorbed radionuclides leave 
the failed waste package and enter the drift geochemical environment. The drift geochemical 
environment is modeled as one of three possible scenarios (Aguilar 2003 [DIRS 163770]): (1) 
the waste package surface dripping scenario, (2) the invert wicking scenario, and (3) the effluent 
from the failed waste package. The colloids leave in-package chemical conditions and enter 
invert chemical conditions which are potentially different from in-package conditions. Once the 
colloids are subject to the invert chemical conditions, the stability and concentration of the 
colloids are recalculated, based on Iinv and pHinv. Therefore, if the colloid mass concentrations 
change (due to loss of colloid stability), the concentrations of sorbed radionuclides are 
recalculated as shown in Figure 20. 
6.5.2.2 Recalculation of Colloid-Associated Radionuclides Concentrations in Drift 
Step 6. In Step 6, the concentrations of radionuclides sorbed to colloids exiting the waste 
package are recalculated because of different chemical conditions in the invert. The new 
concentrations of dissolved radionuclides sorbed onto the colloids are determined. This step is 
illustrated by the flow chart in Figure 20 and by the logic statements below. 
Figure 20. Recalculation of Colloid-Associated Radionuclides in Drift 
CRNdiss,net is the net concentration of dissolved radionuclides after removal of radionuclides from 
fluid by sorption onto waste form, corrosion, and seepage water colloids. CRNtotal is therefore 
equivalent to CRNdiss in Steps 1d, 2b, and 3c. 
Calculation of radionuclide sorption on colloids: 
CRNcoll,wf,rev = CRNdiss x Kd,RN,wf x Mcoll,wf,both 
CRNcoll,FeOx,rev = CRNdiss x Kd,RN,FeOx x Mcoll,FeOx,both 
CRNcoll,gw = CRNdiss x Kd,RN,gw x Mcoll,gw 
,
, 
Stability and 
Mass 
Calculations 
Irreversibly Sorbed 
Colloidal RN 
(passed to 
unsaturated zone) 
, , CRN coll, wf, embed +C RNcoll FeOx irrev 
Colloid 
Source 
Term 
Reversibly Sorbed 
Colloidal RN and 
Dissolved RN 
(recalculated) 
CRN diss, net 
CRN coll, wf, rev 
CRN coll, FeOx, rev 
CRN coll, gw

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 109 June 2003 
6.5.2.3 Calculation of Colloid Source Term for Radionuclide Element (RN) 
Step 7. The colloid source term is calculated by summing the determined concentrations of 
waste form, iron oxyhydroxide, and seepage water/groundwater colloids and the concentrations 
of the radionuclides associated with the colloids, as shown in Figure 21. 
RN coll, FeOx, irrev 
+CRN coll, FeOx, rev 
+CRN coll, gw 
CRN coll, wf, rev 
CRN coll, FeOx, irrev 
CRN coll, FeOx, rev 
CRN coll, gw 
UZ 
Radionuclide 
Concentration 
Recalculation 
CRN coll, wf, embed 
Figure 21. Source Term Summation for Colloid-Associated Radionuclide Concentrations in Drift 
The sum of all of the radionuclides sorbed to colloids (embedded, reversibly sorbed, and 
irreversibly sorbed) and net dissolved radionuclides (those remaining after sorption) are passed 
to the unsaturated zone for disposition in TSPA-LA calculations. 
6.5.3 Implementation of Colloid-Facilitated Transport in the Natural Barrier System 
The maximum groundwater colloid concentration used in the unsaturated zone and saturated 
zone models is a sampled value based on the data presented in Sections 6.3.2.5 and in Figures 11 
and 12. The groundwater colloid mineralogy is stipulated as smectite; smectite colloids are 
available to form pseudocolloids through sorption of dissolved radionuclides. The radionuclides 
Pu, Am, Th, Pa, and Cs are considered in the unsaturated zone and saturated zone models for 
colloid-facilitated transport. The colloids considered in the models include, in addition to 
groundwater colloids, primary waste form colloids (smectite) and corrosion-product colloids 
(iron oxyhydroxides). The smectite waste form colloids, which originate from alteration of highlevel 
waste glass, contain both embedded radionuclides (Pu and Am that are stipulated to be 
irreversibly sorbed) and reversibly-sorbed radionuclides. Corrosion-product colloids also 
contain both reversibly- and irreversibly-sorbed radionuclides, although the latter are not thought 
to be embedded; they simply have extremely high sorption affinities for the iron oxyhydroxides. 
All of these colloids and associated radionuclides are passed to the unsaturated zone from the 
engineered barrier system. 
Colloid parameters used in the waste form/engineered barrier system models and recommended 
for the unsaturated zone/saturated zone models are listed in Table 15.

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Table 15. Colloid Parameters Used in the Waste Form and Engineered Barrier System and 
Recommended for the Unsaturated Zone, and Saturated Zone Models 
Parameter WF/EBS UZ SZ 
Groundwater colloid 
concentration CDFa CDFa CDFa 
KdPu on colloids 
(mL/g) 
104 to 106 (Iron 
Oxyhydroxide) 
103 to 106 (Smectite) 
103 to 106 (Smectite) 103 to 106 (Smectite) 
KdAm on colloids 
(mL/g) 
105 to 107 (Iron 
Oxyhydroxide) 
104 to 107 (Smectite) 
104 to 107 (Smectite) 104 to 107 (Smectite) 
KdTh on colloids 
(mL/g) 
105 to 107 (Iron Oxyhydroxide) 
104 to 107 (Smectite) 
104 to 107 (Smectite) 104 to 107 (Smectite) 
KdPa on colloids 
(mL/g) 
105 to 107 (Iron Oxyhydroxide) 
104 to 107 (Smectite) 
104 to 107 (Smectite) 104 to 107 (Smectite) 
KdCs on colloids 
(mL/g) 
101 to 103 (Iron 
Oxyhydroxide) 
102 to 104 (Smectite) 
102 to 104 (Smectite) 102 to 104 (Smectite) 
NOTES: aCumulative Distribution Function (CDF)Figure 12, Section 6.3.2.5, Groundwater Concentration in 
mg/L. 
UZ = unsaturated zone; SZ = saturated zone; CDF = cumulative distribution function; WF = waste form; 
EBS = engineered barrier system. 
All colloid transport in the unsaturated zone (BSC 2003 [DIRS 163933]) and saturated zone 
(BSC 2003 [DIRS 163932]) occurs by advective transport; colloid diffusion is considered 
negligible because colloids have free diffusion coefficients that are 2 to 4 orders of magnitude 
smaller than solutes. Colloids will transport wherever water flows, which in the unsaturated 
zone is a combination of fractures and the matrix, and in the saturated zone it is almost 
exclusively in fractures or through advective flow pathways in alluvium. The project has no sitespecific 
data on colloid transport under unsaturated conditions, so colloid transport parameters 
developed from tests conducted in saturated fractured volcanic tuffs are applied to the 
unsaturated zone (BSC 2003 [DIRS 163933]). This approach is considered conservative, as it is 
widely recognized that colloids tend to be more retarded under unsaturated conditions than under 
saturated conditions in media that is otherwise similar. This greater retardation in the 
unsaturated zone occurs because (1) immobile air-water interfaces serve as additional surfaces to 
trap colloids and (2) unsaturated zone porewaters tend to have higher ionic strengths than 
saturated zone porewaters, resulting in a greater tendency for colloids to attach to rock surfaces. 
Some of the Pu and Am leaving the engineered barrier system is stipulated to be irreversibly 
sorbed/embedded to colloids. The irreversibly sorbed/embedded fractions of these radionuclides 
travel through the unsaturated zone and saturated zone at the same rate as the colloids they are 
associated with. Irreversibly sorbed radionuclides on colloids leaving the engineered barrier 
system are split into two fractions: one retarded by colloid filtration and detachment processes 
and the other assumed to be completely unretarded. The fraction that travels unretarded depends 
on the groundwater travel time through the natural barrier system (unsaturated zone and

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saturated zone combined), with greater travel times resulting in smaller fractions. However, the 
unretarded fraction is always less than 0.01, so the vast majority of the colloids experience 
filtration processes in the natural barriers that result in colloid retardation. The fraction of 
unretarded colloids is determined by a procedure described in the Saturated Zone Colloid 
Transport report (BSC 2003 [DIRS 163932]). The rationale for assuming that a small colloid 
mass fraction travels unretarded through the natural barriers is that (1) some finite fraction of 
colloids almost always travels unretarded in laboratory and field transport tests, and (2) there 
have been several observations of very small mass fractions of contaminants migrating with 
colloids over large distances in relatively short times in field settings (e.g., Kersting et al. 1999 
[DIRS 103282]; Penrose et al. 1990 [DIRS 100811]; Buddemeier and Hunt 1988 [DIRS 
100712]). 
For colloids that experience filtration in the natural barrier system, colloid retardation factors, Rc, 
are randomly sampled from cumulative distribution functions developed separately for both the 
fractured volcanics and the alluvium. These cumulative distribution functions are constructed 
using retardation factors derived from laboratory and field colloid transport tests conducted 
under varying geochemical conditions with different colloid types and sizes. The value of c R is 
dependent on several factors such as colloid size, colloid type and geochemical conditions 
(e.g., pH, Eh, and ionic strength). For any total system performance assessment simulation, the 
cumulative distribution functions are sampled independently for the volcanics and alluvium. 
However, the value sampled for the volcanics is used for both the unsaturated zone and the 
volcanic portion of the saturated zone flow system, implying perfect correlation between the 
colloid retardation factors in the unsaturated zone and saturated zone. No correlation is assumed 
between retardation factors in the volcanics and alluvium. The cumulative distribution functions 
in both the volcanics and the alluvium are truncated at the lower end so that the minimum 
retardation factor in the volcanics is 6 and the minimum in the alluvium is 8. These truncations 
result in the vast majority of colloids (with the exception of the small unretarded fraction) 
experiencing significant retardation in the natural barrier system. 
The transport of radionuclides that are reversibly sorbed to colloids is governed by equilibrium 
partitioning of the radionuclides between the solution phase, the immobile rock matrix, and 
mobile colloids. Radioisotopes of Pu are transported as one group, radioisotopes of Am, Th, and 
Pa are transported as a second group, and Cs is transported as a third species. Groundwater 
travel times through the natural barriers are slow enough that equilibrium sorption can be 
assumed even for very slow radionuclide sorption and desorption rates. Any radionuclide mass 
that desorbs from colloids at rates slow enough to be comparable to travel times through the 
system is inherently considered part of the irreversibly sorbed/embedded radionuclide mass 
fraction. Colloid-facilitated transport of reversibly sorbed radionuclides depends on colloid 
transport parameters, the mobile colloid mass concentrations, and radionuclide partition 
coefficients onto both colloids and the immobile rock matrix. High colloid concentrations and 
large radionuclide partition coefficients onto colloids (relative to the rock matrix) favor colloidfacilitated 
radionuclide transport at rates that can significantly exceed transport rates in the 
absence of colloids. Because reversibly-sorbed radionuclides will readily desorb from retarded 
colloids to resume partitioning between the solution phase, mobile colloids, and the immobile 
rock matrix, the retardation of colloids works to counterbalance the otherwise enhanced mobility

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MDL-EBS-PA-000004 REV 00 112 June 2003 
of the radionuclide. However, because the sorption of this fraction is assumed to be reversible, 
colloids still serve to facilitate transport, even if they are retarded due to filtration processes. 
6.6 BASE-CASE MODEL RESULTS 
This section provides an overview of the model abstraction results, with a general discussion of 
the range of results, important couplings among processes and their impact on performance 
measures, and data uncertainty and propagation of the uncertainties through the model. 
6.6.1 Overview 
As discussed in Section 6.1, colloids may affect repository performance if they are generated in 
significant quantities, are stable within the waste package, engineered barrier system, and 
unsaturated and saturated zones (respectively). Colloids could potentially carry a significant 
radionuclide load and readily transport these contaminants from the engineered barrier system to 
the unsaturated zone and saturated zone and beyond. Output quantities from the waste form and 
engineered barrier system colloids models to downstream natural barrier system models and/or 
analyses include waste form colloid source terms, including defense high-level waste glass 
colloid concentrations with embedded radionuclides and dissolved waste form radionuclides 
derived from commercial and DOE SNF waste form colloids. Also, the waste form and 
engineered barrier system colloids models determine the concentration of natural seepage 
water/groundwater colloids and corrosion product (iron oxyhydroxide) colloids that are 
propagated from the engineered barrier system onto the underlying natural barrier system. 
6.6.2 Uncertainty Associated with the Model Analysis 
As discussed previously in Section 4.1, Data and Parameters, the parameters developed in this 
model analysis are in some cases based on data that are not site- or Yucca Mountain Project 
(YMP)-specific. Additionally, supporting technical and corroborative information may not have 
been developed specifically from physical and chemical conditions approximating those of the 
repository. Therefore, departure from anticipated repository conditions must be accounted for by 
acknowledging uncertainties in the parameters developed and providing a means to incorporate 
these uncertainties into the total system performance assessment calculations. In this model 
analysis, value ranges and probability distributions, and bounding assumptions deemed 
appropriate for each given parameter or process modeled have been established as a means to 
incorporate these uncertainties into the TSPA-LA model calculations. Another potential 
uncertainty issue is related to the circumstances and conditions of data acquisition and the 
departure from those circumstances and conditions assumed during the application of the data to 
the total system performance assessment models. The three types of parameter range-related 
issues relate to (1) temporal scaling,(2) spatial scaling, and (3) extrapolation from the 
physical and chemical conditions of data acquisition. 
Temporal ScalingIn the implementation of a total system performance assessment, it is often 
necessary to use experimental data gathered over days to a few years and field observations 
recorded over days to a few decades to arrive at conclusions on what is anticipated to occur over 
the repositorys regulatory compliance period and beyond (i.e., periods extending from 
thousands to hundreds of thousands of years). Parameters based on fundamental physical and/or

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MDL-EBS-PA-000004 REV 00 113 June 2003 
chemical principles, such as radionuclide half-life, should be robust over these extended time 
parameters. Other types of parameters such as association of dissolved radionuclide ions with 
attachment sites on the surface of colloids, which is influenced by kinetics, must be used 
cautiously when speculating about future conditions. This aspect of uncertainty is best addressed 
with the formulation and use of scientifically sound assumptions. 
Spatial ScalingThis refers to the extrapolation or application of a documented process 
occurring at laboratory scale (centimeters), for example, to the scale of the repository setting 
(kilometers). Theory and observations of colloid behavior at the molecular and microscopic 
level used in this model report have been corroborated and/or validated to the extent possible 
with empirical field observations. An example of data that could be used to validate model 
predictions with actual field observations is the data reported by Kersting et al. (1999 [DIRS 
103282]). In this study observations of colloidal Pu transport over kilometer-scale distances at a 
nuclear detonation site (Kersting et al. 1999 [DIRS 103282]) were used to demonstrate the 
potential for long-distance transport of colloid-associated Pu within and from the repository to 
the accessible biosphere  these results can be used to assess the validity of Pu transport models 
at a more localized scale (i.e., perhaps at the localized scale of meters or even smaller distances 
of transport). This aspect of uncertainty is best addressed with the application of established 
physical and chemical principles with the formulation of scientifically sound assumptions 
applicable at the scale in question, coupled with the consideration of limitations inherent to the 
application of these assumptions at other scales. 
Extrapolation From Physical and Chemical Conditions of Data AcquisitionExperiments, 
both in the laboratory and field, may yield potentially useful data for total system performance 
assessment models, but these may have employed several parameters (e.g., pH or redox 
conditions) whose ranges may not have been directly relevant to repository conditions. In such 
cases the experimental conditions must be examined in detail so that a valid comparison between 
the experimental conditions and the conditions incorporated into the model can be madeonly 
then can a valid judgment be made regarding the applicability of the data to the model in 
question. An example is the measurement of colloid particle concentrations in solutions of high 
pH and the validity of using those measurements to describe modeled processes at moderate 
(neutral) pH. Again, this aspect of uncertainty is best addressed with the application of 
established physical and chemical principles and the formulation and use of scientifically sound 
assumptions. 
Uncertainty Associated with Waste Form Colloid FormationThere is uncertainty in the 
model for colloid generation and the quantity of colloids generated from the three waste forms 
(defense high-level waste glass, commercial SNF, and DOE SNF) considered in this analysis. 
Uncertainties associated with these data and the Argonne National Laboratory experiments used 
to obtain them include measurement uncertainties and uncontrolled experimental factors and the 
subsequent extrapolation of these results to potential repository conditions. For example, a 
potentially significant contribution to this uncertainty for commercial SNF is the potential for the 
sequestration of colloids formed during the degradation process within rinds of waste 
degradation products. The formation of alteration product rinds on the surface of the waste 
forms could impede the release of colloids from the waste and result in an underestimation of the 
total quantity of colloids produced (see Section 6.3.1.2.1). Additionally, uncertainties during the 
measurement of colloids formed from the various waste forms can potentially arise in the course

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MDL-EBS-PA-000004 REV 00 114 June 2003 
of determination of mass, calculation of volume, determination of particle sizes by filtration, and 
measurement of concentrations by the various detection methods employed. Specific uncertainty 
associated with the measurement of all three types of waste form colloids is discussed in 
Sections 6.3.1.1, Colloids from the Corrosion of Defense High-Level Waste Glass, and Section 
6.3.1.2, Potential for Colloids from the Corrosion of Commercial and DOE SNF. 
Uncertainty Associated with Corrosion Product Colloid FormationThere is limited 
information in the literature on the quantity of corrosion product colloids that could potentially 
form during the degradation of waste package materials and the corrosion of other steel 
components in the engineered barrier system (see Section 6.3.1.3, Colloids from the Corrosion of 
Waste Package and Metallic Invert Materials). Therefore, the values and ranges developed for 
the corrosion colloid source term parameters have a large degree of uncertainty. To reduce some 
of this uncertainty and increase the defensibility of the developed parameters, consideration was 
given to the observed quantities of iron oxyhydroxide colloids observed in scaled-down 
miniature waste package degradation experiments by an ongoing DOE-funded research project at 
University of Nevada at Las Vegas (see Section 6.3.1.3). The use of appropriately scaled-down 
waste package configurations (i.e., surface area to total package volume scaled-down 
proportionally to approximately 1/70 the size of actual proposed repository waste packages) and 
the use of water of similar chemical composition to the groundwater found at Yucca Mountain 
render the experiments directly relevant to conditions anticipated in the proposed Yucca 
Mountain repository. Additionally, conservative, but realistic bounding values have been 
established for the corrosion product colloid parameters recommended for use in the model in 
order to propagate the uncertainty associated with these parameters throughout the TSPA-LA 
analysis. 
Uncertainty Associated with the Measurement of Seepage Water/Groundwater Colloids 
The determination of colloid concentrations in groundwater samples presents many challenges 
that add to the uncertainty of developed parameters. Major factors that contribute to uncertainty 
in the concentrations of colloids in the groundwater samples used to establish parameters for use 
in the total system performance assessment analysis include (1) field sampling techniques, 
including differences in pumping rates at each well during extraction of the water samples, (2) 
other unknown factors affecting the quantities of particles suspended in the water samples, 
including the types of additives introduced in the wells during the drilling process itself, (3) 
errors inherent to the laboratory methods used to measure the quantities of colloids suspended in 
the water samples (e.g., filter ripening, interference and detection limitations for dynamic light 
scattering measurement techniques). At the spatial scale, there is the issue of the appropriateness 
of extrapolation of specific water sample measurements to represent the colloid concentrations in 
waters over a wider region or area. Temporal scaling issues could include potential seasonal 
variations in the quantities of colloids suspended in water samples extracted, or even shorter 
time-scale changes in colloid concentrations in water samples during the sampling of wells. To 
reduce some of this uncertainty, mass concentrations considered to establish the groundwater 
colloid concentration parameters were pooled using primarily groundwater samples extracted in 
the vicinity of Yucca Mountain (a few samples collected from Idaho National Engineering and 
Environmental Laboratory were also used in the analysis) and a discrete cumulative distribution 
function was established to evaluate the uncertainty in colloid concentration distribution (see 
Section 6.3.2.5, Figure 12). The goal of the uncertainty distribution for groundwater colloid 
concentrations is to numerically estimate uncertainty on a large scale. Based on the groundwater

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MDL-EBS-PA-000004 REV 00 115 June 2003 
colloid concentration collected at the two sites (Yucca Mountain and Idaho National Engineering 
and Environmental Laboratory) and the high uncertainty associated with the collection of 
groundwater colloids, a reasonable representation of the uncertainty is shown in the cumulative 
distribution function. The establishment of groundwater colloid concentrations from the 
cumulative distribution function allowed for the stochastic sampling over a wide range of 
colloid mass concentrations, including the sampling of high concentrations (i.e., exceeding 100 
mg/L) in the TSPA-LA model calculations some of the time (2 percent of the model iterations), 
while probabilistically allowing for the selection of lower mass concentrations (0.0011.0 mg/L) 
75 percent of the time, as observed in the majority of samples used in the analysis. Exclusive 
consideration of samples collected by the same research team from Los Alamos National 
Laboratory reduces the uncertainty that could potentially result from differences in field 
sampling techniques. 
Uncertainty Associated with the Determination of Colloid StabilityThe ionic strength and 
pH of the water are the major considerations influencing the stability of all colloids considered in 
the model analysis (Section 6.3.2, Colloid Stability and Concentration). As with other 
parameters and data used or established in this analysis, uncertainty in the stability of colloids 
(smectite and iron oxyhydroxide) as a function of pH and ionic strength is associated mostly with 
the extrapolation of laboratory data reported in the literature or project-supported experimental 
work to actual conditions (i.e., solution chemistry) that would be present in the repository 
environment over the regulatory compliance period. Again, much of this uncertainty is 
accommodated by establishing conservative, but reasonable, bounding values and ranges of 
parameter values whose stability is affected by pH and ionic strength. This uncertainty is 
propagated through the TSPA-LA model by stochastic sampling of these distributions during 
Monte Carlo simulations employed in the model calculations. 
Uncertainty Associated with Radionuclide Sorption Onto ColloidsA large degree of 
uncertainty associated with the development of sorption partition coefficients (Kd values) to 
describe the degree of sorption of specific radionuclides to colloids results from the scarcity of 
pertinent published data. Values reported in the literature are primarily the result of 
experimental work designed to establish Kd values for contaminants sorbed onto rocks, soils and 
other minerals, but literature specific to colloid-size minerals is not readily available. For this 
reason, the Kd value parameters established for smectite and iron oxyhydroxide colloids in this 
analysis relay heavily on limited experimental work conducted at Los Alamos National 
Laboratory (see Section 6.3.3.1, Reversible Sorption). Corroborative data reported in the 
literature were evaluated to augment the limited Los Alamos National Laboratory data. 
Therefore, the use of data from multiple sources contribute to uncertainties due to differences in 
laboratory techniques employed. Within specific experimental data sets, results were subject to 
experimental measurement uncertainties (e.g., detection limitations, quantification methods, 
interferences, etc.). The establishment of reasonable, bounding values and ranges of Kd values 
for each radionuclide considered in the model analysis reduces the potential effects of these 
uncertainties in the overall TSPA-LA model. 
Model Implementation of UncertaintyImplementation of the uncertainties associated with 
the parameters established during this model analysis is accomplished through the use of 
parameter ranges and distributions, rather than single, deterministic parameter values in the 
model analysis  reasonable bounding values were established for most of the parameters.

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Within the TSPA-LA model, implementation of the colloids model abstraction incorporates the 
parameter uncertainties through the use of Monte Carlo simulation techniques, thereby ensuring 
that parameter uncertainties are propagated throughout the abstraction during computation and 
therefore reflected in the calculated results. Implementation of the various sub-model 
components of the model abstraction during their implementation in the TSPA-LA model is 
detailed in Section 6.5, Model Formulation for Base-Case Assessment. In general, the 
uncertainty associated with each of these submodel components is related to the incomplete 
knowledge of the system and its properties (epistemic).

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Table 16. Summary of Intermediate Parameters and Results Produced in Abstraction 
Data Tracking 
Number (DTN) 
Parameter 
Name 
Data/Parameter Description Unitsa Locations in Model 
Report 
Value/ Range Distribution/ 
Uncertainty 
Waste Form Colloids 
SN0304T0504103.004 CRNcoll,wf,embed,max Highest observed or expected 
concentration of irreversibly 
attached (embedded as a solid 
inclusion) Pu associated with 
waste form colloids 
mol/L Section 6.3.2.4 
Figure 18a 
1E-7 mol/Lb Fixed value 
Epistemic 
SN0304T0504103.004 CRNcoll,wf,embed,min Lowest observed or expected 
concentration of irreversibly 
attached (embedded as a solid 
inclusion) Pu associated with 
waste form colloids 
mol/L Section 6.3.2.4 
Figure 18a 
1E-11 mol/Lb 
(small non-zero 
number) 
Fixed value 
Epistemic 
N/A CRNcoll,wf,embed Concentration of irreversibly 
attached (embedded as a solid 
inclusion) radionuclide element 
RN (Pu, Am) associated with 
waste form colloids 
mol/L Section 6.5.1 and 
Figure 18a 
N/A; calculated 
at each time step 
N/A; calculated at each 
time step 
Epistemic 
SN0304T0504103.004 Mcoll,wf,both,max Highest observed or expected 
mass of waste form colloids per 
unit volume or mass of water 
mg/L Sections 6.3.1.1 and 
6.3.2.4 
Figure 18c 
5.0 mg/Lc Fixed value 
Epistemic 
LL000905312241.018 
[DIRS 152621] 
LL991109751021.094 
[DIRS 142910] 
Mcoll,wf,both,min Lowest observed or expected 
mass of waste form colloids per 
unit volume or mass of water 
mg/L Sections 6.3.1.1 and 
6.3.2.4 
Figure 18c 
5.0 x 10-4 mg/Lc Fixed value 
Epistemic 
LL000905312241.018 
[DIRS 152621] 
LL991109751021.094 
[DIRS 142910] 
Mcoll,wf,both Mass of waste form colloids with 
reversibly sorbed or irreversibly 
attached (embedded) 
radionuclide element RN per unit 
volume or mass of water 
mg/L Section 6.5.1 and 
Figures 18c and 18d 
N/A; calculated 
at each time step 
N/A; calculated at each 
time step 
Epistemic 
N/A; References: 
Tombacz et al. 1990 
[DIRS 112690]; Figure 4 
Ilo-thresh,coll,wf Ionic strength below which waste 
form colloids are stable 
mol/L Sections 6.3.2.2 and 
6.3.2.3 and Figures 4, 
5, 8, and 9 
0.01 mol/L Fixed value 
Epistemic 
N/A; References: 
Tombacz et al. 1990 
[DIRS 112690]; Figure 4 
Ihi-thresh,coll,wf Ionic strength above which waste 
form colloids are unstable 
mol/L Sections 6.3.2.2 and 
6.3.2.3 and Figures 4, 
5, 8, and 9 
0.05 mol/L Fixed value 
Epistemic

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Table 16. Summary of Intermediate Parameters and Results Produced in Abstraction (Continued) 
Data Tracking 
Number (DTN) 
Parameter 
Name 
Data/Parameter Description Unitsa Locations in Model 
Report 
Value/ Range Distribution/ 
Uncertainty 
N/A STcoll,wf,is Function relating stability of 
waste form colloids to ionic 
strength, based on results of 
DHLWG degradation 
experiments (based on Pu 
concentration) 
mol/L Section 6.5.1 and 
Figure 18b 
[Pu colloid] = - 
2.50E-6  I 
+1.25E-7 
N/A; calculated at each 
time step 
Epistemic 
N/A STcoll,wf,pH Function relating stability of 
waste form colloids to ionic 
strength and pH, over limited pH 
range (pH 2 to 10), based on 
results of montmorillonite stability 
experiments 
mol/L Section 6.3.2.2 and 
6.3.2.3 and Figures 4, 
5, 8, and 9 
Section 6.5.1 and 
Figure 18b 
I = pH/200 N/A; calculated at each 
time step 
Epistemic 
SN0304T0504103.002 Kd,Pucoll,wf Distribution coefficient for 
reversible sorption of Pu onto 
waste form (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18d 
103 to 106 mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Amcoll,wf Distribution coefficient for 
reversible sorption of Am onto 
waste form (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18d 
104 to 107 mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Thcoll,wf Distribution coefficient for 
reversible sorption of Th onto 
waste form (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18d 
104 to 107 mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Pacoll,wf Distribution coefficient for 
reversible sorption of Pa onto 
waste form (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18d 
104 to 107 mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Cscoll,wf Distribution coefficient for 
reversible sorption of Cs onto 
waste form (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18d 
102 to 104 mL/g 
colloid 
See Table 10 
Epistemic 
N/A CRNcoll,wf,rev Concentration of reversibly 
attached radionuclide element 
RN (Pu, Am, Th, Pa, Cs) 
associated with waste form 
colloids 
mol/L Section 6.5.1 
Figure 18d 
N/A; calculated 
at each time step 
N/A; calculated at each 
time step 
Epistemic 
N/A; calculated by the 
TSPA-LA model (inpackage 
chemistry) 
Iwp Ionic strength of fluid within and 
exiting breached waste package 
mol/L Section 6.5.1 and 
Figure 18a 
N/A N/A

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Table 16. Summary of Intermediate Parameters and Results Produced in Abstraction (Continued) 
Data Tracking 
Number (DTN) 
Parameter 
Name 
Data/Parameter Description Unitsa Locations in 
Model Report 
Value/ Range Distribution/ 
Uncertainty 
N/A; calculated by the 
TSPA-LA model (inpackage 
chemistry) 
pHwp pH of fluid within and exiting 
breached waste package 
pH units Section 6.5.1 and 
Figure 18b 
N/A N/A 
N/A; calculated by the 
TSPA-LA model 
(solubility limits) 
CRNdiss Concentration of dissolved 
radionuclide element RN per unit 
volume or mass of water (Pu, 
Am, Th, Pa, Cs) 
mol/L Sections 6.5.1 and 
6.5.2 
N/A N/A 
N/A; calculated by the 
TSPA-LA model 
Iinv I of fluid within drift resulting from 
mixing of WP fluid and 
groundwater 
mol/L Section 6.5.2 
Figure 19 
N/A N/A 
N/A; calculated by the 
TSPA-LA model 
pHinv pH of fluid within drift resulting 
from mixing of WP fluid and 
groundwater 
pH units Section 6.5.2 
Figure 19 
N/A N/A 
Corrosion-Generated Colloids 
SN0304T0504103.003 Mcoll,FeOx,sampled Highest observed or expected 
mass of iron oxyhydroxide 
colloids per unit volume or mass 
of water 
mg/L Section 6.3.2.3 
Figure 18e 
0.05 to 50 mg/L Uniform 
Epistemic 
SN0304T0504103.003 Mcoll,FeOx,min Lowest observed or expected 
mass of iron oxyhydroxide 
colloids per unit volume or mass 
of water 
mg/L Section 6.3.2.3 
Figure 18e 
1E-3 mg/L Fixed value 
Epistemic 
N/A Mcoll,FeOx Mass of iron oxyhydroxide 
colloids per unit volume or mass 
of water 
mg/L Section 6.5.1 and 
Figure 18e 
N/A; calculated 
at each time step 
N/A; calculated at each 
time step 
Epistemic 
N/A Mcoll,FeOx, both Mass of iron oxyhydroxide 
colloids per unit volume or mass 
of water with both reversibly and 
irreversibly sorbed Pu and Am. 
mg/L Section 6.5.1 and 
Figure 18j 
N/A; calculated 
at each time step 
N/A; calculated at each 
time step 
Epistemic 
SN0304T0504103.002 Kd,Pucoll,FeOx Distribution coefficient for 
reversible sorption of Pu onto 
corrosion-generated (iron 
oxyhydroxide) colloids 
mL/g 
colloid 
Sections 6.3.3.1 and 
6.3.3.2 
Figure 18f 
104 mL/g colloid 
(EBS) 
104 to 106 mL/g 
colloid (UZ/SZ) 
See Table 10 
Epistemic

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 120 June 2003 
Table 16. Summary of Intermediate Parameters and Results Produced in Abstraction (Continued) 
Data Tracking 
Number (DTN) 
Parameter 
Name 
Data/Parameter Description Unitsa Locations in 
Model Report 
Value/ Range Distribution/ 
Uncertainty 
SN0304T0504103.002 Kd,Amcoll,FeOx Distribution coefficient for 
reversible sorption of Am onto 
corrosion-generated (iron 
oxyhydroxide) colloids 
mL/g 
colloid 
Sections 6.3.3.1 and 
6.3.3.2 
Figure 18f 
105 mL/g colloid 
(EBS) 
105 to 107 mL/g 
colloid (UZ/SZ) 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Thcoll,FeOx Distribution coefficient for 
reversible sorption of Th onto 
corrosion-generated (iron 
oxyhydroxide) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18f 
105 to 107 mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Pacoll,FeOx Distribution coefficient for 
reversible sorption of Pa onto 
corrosion-generated (iron 
oxyhydroxide) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18f 
105 to 107 mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Cscoll,FeOx Distribution coefficient for 
reversible sorption of Cs onto 
corrosion-generated (iron 
oxyhydroxide) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18f 
101 to 103 mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.003 SA,FeOx,coll Specific (effective) surface area 
of corrosion-generated (iron 
oxyhydroxide) colloids 
m2/g 
colloid 
Section 6.3.3.2 
Figure 18f 
1.8 to 720 m2/g Log Uniform 
Epistemic 
SN0304T0504103.003 FRN Target-flux out ratio: ratio of 
radionuclide mass associated 
with colloids (reversible and 
irreversible) to radionuclide mass 
associated with colloids and 
dissolved radionuclide mass 
------ 
Section 6.3.3.2 
Figure 18f 
0.9 to 0.99 Uniform 
Epistemic 
N/A CRncol 
l,FeOx,rev 
Concentration of radionuclide 
element RN sorbed reversibly 
onto corrosion-generated (iron 
oxyhydroxide) colloids (Am, Th, 
Pa, Cs) 
mol/L Section 6.5.1.2 and 
Figure 18f 
N/A; calculated 
at each time step 
N/A; calculated at each 
time step 
Epistemic 
N/A CPuAm,coll,FeOx,irrev Concentration of Pu and Am 
irreversibly sorbed onto 
corrosion-generated (iron 
oxyhydroxide) colloids 
mol/L Section 6.5.1.2 and 
Figure 18f, and 
Section 6.3.3.2 
N/A; calculated 
at each time step 
N/A; calculated at each 
time step 
Epistemic

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MDL-EBS-PA-000004 REV 00 121 June 2003 
Table 16. Summary of Intermediate Parameters and Results Produced in Abstraction (Continued) 
Data Tracking 
Number (DTN) 
Parameter 
Name 
Data/Parameter Description Unitsa Locations in Model 
Report 
Value/ Range Distribution/ 
Uncertainty 
N/A STcoll,FeOx,pHlo Function relating stability of iron 
oxyhydroxide colloids to pH and 
ionic strength at relatively low pH 
values 
mol/L Section 6.5.1 and 
Figure 18e 
I = -0.02  pH 
+0.17 
N/A; calculated at each 
time step 
Epistemic 
N/A STcoll,FeOx,pHhi Function relating stability of iron 
oxyhydroxide colloids to pH and 
ionic strength at relatively high 
pH values 
mol/L Section 6.5.1 and 
Figure 18e 
I = +0.02  pH 
0.17 
N/A; calculated at each 
time step 
Epistemic 
N/A STcoll,FeOx,pHint Function relating stability of iron 
oxyhydroxide colloids to pH and 
ionic strength at intermediate pH 
values 
Boolea 
n 
Section 6.5.1 and 
Figure 18e 
Boolean 
(pH = 8 AND pH 
= 9) 
N/A; calculated at each 
time step 
Epistemic 
N/A; Reference: Liang 
and Morgan 1990 [DIRS 
109524] 
Ilo-thresh,coll,FeOx Ionic strength below which iron 
oxyhydroxide colloids are stable 
mol/L Section 6.3.2.3 
Figures 6 and 7 
0.01 mol/L Fixed value 
Epistemic 
N/A; Reference: Liang 
and Morgan 1990 [DIRS 
109524] 
Ihi-thresh,coll,FeOx Ionic strength above which iron 
oxyhydroxide colloids are 
unstable 
mol/L Section 6.3.2.3 
Figures 6 and 7 
0.05 mol/L Fixed value 
Epistemic 
N/A; calculated by the 
TSPA-LA model (inpackage 
chemistry) 
Iwp Ionic strength of fluid within and 
exiting breached waste package 
mol/L Section 6.5.1 and 
Figure 18e N/A N/A 
N/A; calculated by the 
TSPA-LA model (inpackage 
chemistry) 
pHwp pH of fluid within and exiting 
breached waste package 
pH 
units 
Section 6.5.1 and 
Figure 18e N/A N/A 
N/A; calculated by the 
TSPA-LA model (solubility 
limits) 
CRNdiss Concentration of dissolved 
radionuclide element RN per unit 
volume or mass of water (Pu, 
Am, Th, Pa, Cs) 
mol/L Sections 6.5.1 and 
6.5.2; 
Figure 18f 
N/A N/A 
N/A; calculated by the 
TSPA-LA model 
Iinv I of fluid within drift mol/L Section 6.5.2 
Figure 19 
N/A N/A 
N/A; calculated by the 
TSPA-LA model 
pHinv pH of fluid within pH 
units 
Section 6.5.2 
Figure 19 
N/A N/A

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MDL-EBS-PA-000004 REV 00 122 June 2003 
Table 16. Summary of Intermediate Parameters and Results Produced in Abstraction (Continued) 
Data Tracking 
Number (DTN) 
Parameter 
Name 
Data/Parameter Description Unitsa Locations in Model 
Report 
Value/ Range Distribution/ 
Uncertainty 
Groundwater Colloids 
N/A Mcoll,gw Mass of groundwater colloids per 
unit volume or mass of water 
mg/L Section 6.5.1 
Figure 18g 
N/A; calculated 
at each time step 
N/A; calculated at each 
time step 
Epistemic 
SN0304T0504103.001 Mcoll,gw, sampled Mass of groundwater colloids per 
unit volume or mass of water 
sampled at each time step 
mg/L Section 6.3.2.5 
Figure 18g 
See Table 5 See Table 5 
SN0304T0504103.001 Mcoll,gw, min Minimum mass of groundwater 
colloids per unit volume or mass 
of water sampled at each time 
step 
mg/L Section 6.3.2.5 
Figure 18g 
1 10-6 N/A 
SN0304T0504103.002 Kd,Pucoll,gw Distribution coefficient for 
reversible sorption of Pu onto 
groundwater (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18i 
103 to 106mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Amcoll,gw Distribution coefficient for 
reversible sorption of Am onto 
groundwater (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18i 
104 to 107mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Thcoll,gw Distribution coefficient for 
reversible sorption of Th onto 
groundwater (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18i 
104 to 107mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Pacoll,gw Distribution coefficient for 
reversible sorption of Pa onto 
groundwater (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18i 
104 to 107mL/g 
colloid 
See Table 10 
Epistemic 
SN0304T0504103.002 Kd,Cscoll,gw Distribution coefficient for 
reversible sorption of Cs onto 
groundwater (smectite) colloids 
mL/g 
colloid 
Section 6.3.3.1 
Figure 18i 
102 to 104 mL/g 
colloid 
See Table 10 
Epistemic 
N/A CRNcoll,gw Concentration of reversibly 
attached radionuclide element 
RN associated with groundwater 
colloids (Pu, Am, Th, Pa, Cs) 
mol/L Section 6.5.1 and 
Figure 18i 
N/A; calculated 
at each time step 
N/A; calculated at each 
time step 
Epistemic 
N/A; calculated by the 
TSPA-LA model (inpackage 
chemistry) 
Iwp Ionic strength of fluid within and 
exiting breached waste package 
mol/L Section 6.5.1 and 
Figure 18g 
N/A N/A

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MDL-EBS-PA-000004 REV 00 123 June 2003 
Table 16. Summary of Intermediate Parameters and Results Produced in Abstraction (Continued) 
Data Tracking 
Number (DTN) 
Parameter 
Name 
Data/Parameter Description Unitsa Locations in Model 
Report 
Value/ Range Distribution/ 
Uncertainty 
N/A; calculated by the 
TSPA-LA model (inpackage 
chemistry) 
pHwp pH of fluid within and exiting 
breached waste package 
pH 
units 
Section 6.5.1 
and Figure 18h 
N/A N/A 
N/A; calculated by TSPALA 
model (solubility 
limits) 
CRNdiss Concentration of dissolved 
radionuclide element RN per unit 
volume or mass of water (Pu, 
Am, Th, Pa, Cs) 
mol/L Sections 6.5.1 and 
6.5.2; 
Figure 18i 
N/A N/A 
N/A; References: 
Tombacz et al. 1990 
[DIRS 112690]; Figure 4 
Ihi-thresh,coll,gw Ionic strength above which 
groundwater colloids are 
unstable 
mol/L Sections 6.3.2.2 and 
6.3.2.5 
Figures 4 and 5 
0.05 mol/L Fixed value 
Epistemic 
N/A; calculated by the 
TSPA-LA model (solubility 
limits and near-field 
chemical environment) 
CRNdiss Concentration of dissolved 
radionuclide element RN per unit 
volume or mass of water (Pu, 
Am, Th, Pa, Cs) 
mol/L Sections 6.5.1 and 
6.5.2; 
Figure 18i 
N/A N/A 
Invert Parameters 
N/A; calculated by the 
TSPA-LA model 
CRndiss,net Net concentration of dissolved 
radionuclides after removal of 
radionuclides by sorption to 
colloids 
mol/L Section 6.5.2.2 and 
Figure 20 
N/A N/A 
Epistemic 
N/A; calculated by the 
TSPA-LA model 
CRNtotal Sum of net dissolved and 
sorbed-to-colloids radionuclide 
concentrations 
mol/L Section 6.5.2.2 and 
Figure 20 
N/A N/A 
Epistemic 
N/A; calculated by the 
TSPA-LA model 
Iinv I of fluid within drift mol/L Section 6.5.2 
Figure 19 
N/A N/A 
Epistemic 
N/A; calculated by the 
TSPA-LA model 
pHinv pH of fluid within drift pH 
units 
Section 6.5.2 
Figure 19 
N/A N/A 
Epistemic 
NOTES: aConcentration, mol/L, is treated here as moles/liter of dispersion and therefore is not molarity in the strict sense 
bUncertainty is linked to uncertainty for ionic strength, an input parameter in the TSPA-LA model (no additional uncertainty is added) 
cMass is correlated with irreversible radionuclide concentration 
WP = waste package; DHLWG = defense high-level waste glass; N/A = not applicable; RN = radionuclide; UZ = unsaturated zone; SZ = saturated zone; 
EBS = engineered barrier system.

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MDL-EBS-PA-000004 REV 00 124 June 2003 
6.7 DESCRIPTION AND ANALYSES OF THE BARRIER CAPABILITY 
As discussed in Section 1, Purpose, the abstraction of the process models reported in this 
document is intended to capture the most important characteristics of radionuclide-colloid 
behavior for use in predicting the potential impact of colloid-facilitated radionuclide transport on 
repository performance. Colloid information from this report will be considered in evaluation of 
the unsaturated zone as a barrier to radionuclide transport. As modeled in total system 
performance assessment, colloids may act to facilitate transport of radionuclides from the waste 
package to the surrounding engineered barrier system and beyond to the underlying unsaturated 
zone component of the natural barrier system of the repository. Therefore, a description and 
analyses of barrier capability associated with colloids is not applicable and is not included in this 
document. 
6.8 EVALUATION OF ALTERNATIVE MODELS 
The alternative models described in Section 6.4 were evaluated and considered not to be 
desirable as alternative approaches to generating a colloid source term. Justification for not 
considering these alternative models was that either (1) the additional data required to support 
the alternative model is not available, and therefore the model cannot be developed for 
application to the repository environment, or (2) the conditions necessary to drive the alternative 
model processes are not anticipated in the repository (see Table 12, Section 6.4). Accordingly, 
the models were not quantitatively evaluated. 
7. VALIDATION 
The waste form and in-drift colloids abstraction model is used to describe the possible 
consequences of colloid-facilitated radionuclide transport during postclosure. Sensitivity studies 
(BSC 2002 [DIRS 160780]) showed that the colloid model had a small effect on the TSPA-LA 
results and therefore was given an importance to expected risk of Not Significant. Therefore 
a relatively low level of confidence is required in validating this model (BSC 2002 [DIRS 
160780], Section 4.6, p. 4-4). 
The types and characteristics (including stability and concentration) of colloids formed from the 
degradation of the waste forms as used in the abstraction is based on extensive observations of 
colloids from testing programs and natural groundwaters. Because of the minute dimensions and 
unique properties of colloids, their study presents formidable difficulties; the body of work used 
for the abstraction developed in this analysis represents a significant fraction of the state-of-theart 
colloid research performed to date. 
The validation activities for this model analysis and abstraction took into account the criteria 
established in the Yucca Mountain Review Plan (NRC 2002 [DIRS 158449]) (see Section 4.2). 
Post-model development validation is accomplished through corroboration of model predictions 
and data used with data published in refereed journals or literature and through corroboration by 
comparison to data from natural analog sites. Validation is described in the following 
subsections. Corroborating/supporting data and information used to develop and validate the 
parameters are listed in Table 17.

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MDL-EBS-PA-000004 REV 00 125 June 2003 
Table 17. Supporting (Corroborating) Information Used to Validate the Colloid Model 
Criterion Supporting (Corroborating) 
Information Source Data/Information 
----- BSC 2002 [DIRS 160780] Measure of importance to expected risk of colloid 
model 
2 Tombacz et al. 1990 [DIRS 
112690] 
Stability of smectite (which is used as a surrogate 
mineralogy for defense high-level waste glass colloids) at 
full range of conditions anticipated in TSPA-LA 
calculations 
3,4 Mertz et al. 2003 [DIRS 162032] Corroborative data supporting conclusion of no 
significant colloids generated from CSNF degradation. 
3,4 Short et al. 1988 [DIRS 113937] Corroborative information and data regarding low colloidassociated 
U concentrations in the vicinity of mines 
3,4 Payne et al. 1992 [DIRS 124812] Corroborative information and data regarding low colloidassociated 
U concentrations in the vicinity of mines 
3,4 Zanker et al. 2000 [DIRS 
162746] 
Corroborative information and data regarding low colloidassociated 
U concentrations in the vicinity of mines 
3,4 Vilks et al. 1993 [DIRS 108261] Corroborative information and data regarding low colloidassociated 
U concentrations in the vicinity of mines 
3,4 Brady et al. 2002 [DIRS 161649] Corroborative information and data regarding limited 
extent of dissolved U plumes 
6 
DTN LA0002SK831352.003 
[DIRS 161771] 
DTN LA0002SK831352.004 
[DIRS 161579] 
Corroborative (non-Q) data for qualified groundwater 
data 
8 Coughtrey et al. 1985 [DIRS 
154494] 
Corroborative information regarding irreversibility of Pu 
on mineral particles 
8 Litaor and Ibrahim 1996 [DIRS 
161667] 
Corroborative information regarding irreversibility of Pu 
on mineral particles 
8 Bunzl et al. 1995 [DIRS 154468] Corroborative information regarding irreversibility of Pu 
on mineral particles 
7.1 VALIDATION OF WASTE FORM COLLOID PARAMETERS 
Consistant with Technical Work Plan for Waste Form Degradation Modeling, Testing, and 
Analyses in Support of SR and LA (BSC 2002 [DIRS 160779], Section 2.1.4.3), model validation 
will require meeting the following criteria: 
Criterion 1 (Relevant to Technical Work Plan Validation Criterion 2) 
Are the concentrations of colloids and associated Pu produced in defense high-level waste glass 
degradation experiments and incorporated into the colloid abstraction reasonable with respect 
to scientific principles and observed colloid concentrations in the Project and peer-reviewed 
literature? 
Of the laboratory data generated from the defense high-level waste glass testing at Argonne 
National Laboratory, colloid mass (smectite) and colloid-associated Pu concentration were used 
in the model and therefore need to be validated. Other radionuclides were detected in the 
colloids (see Section 6.3.1.1) but not quantified and so these were not incorporated into the 
model. The experimentally determined colloid masses and Pu concentrations were loosely 
bounded in order to account for the potential effects of the other detected embedded 
radionuclides, as well as to address potential uncertainty described in Criterion 2.

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MDL-EBS-PA-000004 REV 00 126 June 2003 
The specific defense high-level waste glass test data set used in the model were validated by 
assessing their reasonableness and by comparing the data to other defense high-level waste glass 
data generated during the testing program. Smectite colloids from any particular source must 
behave similarly under a given set of physicochemical conditions in terms of stability and 
maximum concentration. As can be seen in Figure 3, the smectite colloid concentrations 
encountered in the defense high-level waste glass testing (up to ~5 mg/L) are within the range of 
observed smectite concentrations in natural groundwaters, which can range up to a few hundred 
mg/L. Therefore the concentrations determined are reasonable. 
Since the Argonne National Laboratory defense high-level waste glass tests are one-of-a-kind, 
the mechanism of Pu attachment has not been specifically determined, and no natural analogs 
allow comparison, the stipulation that Pu is irreversibly associated with the colloids cannot be 
directly validated. However, the stipulation is definitely conservative, in that irreversible 
attachment of Pu to the colloids maximizes Pus potential mobility. 
Criterion 2 (Relevant to Technical Work Plan Validation Criterion 1) 
Were the test conditions for the defense high-level waste glass colloid generation experiments 
representative of physicochemical conditions anticipated in the proposed repository and 
incorporated into the abstraction? 
The range of chemical conditions in the laboratory testing represent a subset of the conditions 
expected in the repository. Specifically, the pH encountered in the experiments ranged from 
approximately 9 and 11.5 (Buck and Bates 1999 [DIRS 109494]). The pH range anticipated in 
the waste form and drift environments for the majority of the time is expected to be 4 to 11. 
According to the in-package chemistry modeling study (BSC 2003 [DIRS 163919]), the pH 
range for fluids reacting with commercial SNF is 3.9 to 8.1, while the range for fluids reacting 
with co-disposal materials is from 4.8 to 10. This suggests that this portion of the model upon 
which these high-pH data are based does not adequately represent the full range of conditions 
expected and that extrapolation of the model to substantially lower pHs is tenuous. 
In defense of the data, it is well known that smectite colloids have a zero point of charge of 
approximately 2 (see Section 6.3.2.2) and thus are stable at pH greater than 2. The stability does 
decrease as the zero point of charge is approached and maximum colloid concentration increases. 
This relationship is accommodated by the pH vs. ionic strength stability relationship described in 
Section 6.3.2.2 and Figure 5. This does not account for the decreased maximum possible 
concentration of smectite colloids at lower pH, but this turns out to be conservative, as it 
overestimates the smectite concentration at pHs lower than those of the experimental conditions. 
Further, high pH would be reasonable in proximity to the surface of degrading defense high-level 
waste glass, consistent with the high-pH experimental conditions (Section 6.3.2.2) (Buck and 
Bates 1999 [DIRS 109494]). Smectite colloids would remain stable if and when the fluids in 
which they occur became diluted (lower ionic strength) and became lower in pH. 
The above argument in defense of the high-pH data does not account for the possibility that the 
colloid-associated Pu concentration may be different at lower pH. This is difficult to evaluate, 
since the Argonne National Laboratory defense high-level waste glass tests are one-of-a-kind,

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MDL-EBS-PA-000004 REV 00 127 June 2003 
the mechanism of Pu attachment has not been specifically determined, and there are no natural 
analogs for comparison. If the attached Pu decreases with lower pH, the model is conservative, 
since the Pu concentration on colloids would be overestimated at lower pH. If, however, the 
attached Pu increases with lower pH, the model would underestimate the Pu concentration. The 
relationship for the colloid-associated Pu concentrations described in Criterion 1 was chosen to 
bound loosely the experimental data. 
Criterion 3 (Relevant to Technical Work Plan Validation Criteria 1 and 2) 
Is the model approach used, which stipulates that commercial SNF will not produce colloids in 
significant quantities, consistent with commercial SNF-specific test results and peer-reviewed 
literature on field observations near uranium mines and deposits? 
Data on experimental degradation of commercial SNF (drip tests) have been collected for several 
years, and to date very few colloids have been observed (Section 6.3.1.2.1). It was tentatively 
concluded in Waste Form Colloid-Associated Concentrations Limits: Abstraction and Summary 
(CRWMS M&O 2001 [DIRS 153933]), pending additional confirmation data, that commercial 
SNF was not an important source of colloids, and therefore potential colloid-associated 
radionuclides from commercial SNF could be omitted from the colloid model. The original 
conclusion, based on the first five years of data, has not changed. It is corroborated with the 
subsequent three years of data (Section 6.3.1.2.1); with preliminary data from a recent set of 
experiments that characterized the mineralogy, size characteristics, and stability of particles in a 
U-bearing-colloid dispersion (Section 6.3.1.2.3); and with field observations (see Section 
6.3.1.2.4). 
The three additional years of testing have not yielded anything to alter that conclusion. A 
possible criticism of the test design, namely that the apertures in the sample-holding zircaloy 
screen were small and became clogged with alteration products, was addressed with the 
introduction of a redesigned screen. This change had no apparent effect on the results, i.e., an 
increased number of particles was not observed after the change in screen configuration, 
although on two occasions somewhat elevated colloid concentrations were encountered at the 
first sampling after a configuration change (Section 6.3.1.2.1). 
A recent set of experiments involved the generation under ideal chemical conditions of a stable 
colloidal suspension composed of meta-schoepite and UO2. It was observed that the colloid 
concentrations were stable over the short term but appear to dissolve under repository-relevant 
conditions (Section 6.3.1.2.3). This observation may be consistent with the small numbers of 
colloids developed in the Argonne National Laboratory drip tests. It is emphasized that the data 
are preliminary. 
However, the creation of a stable U-substrate colloid suspension is significant and merits further 
investigation. Determination and confirmation that meta-schoepite and UO2 colloid suspensions 
are inherently unstable under potential repository conditions would increase confidence in that 
conclusion. 
Field evidence from investigations in the vicinity of uranium deposits and uranium mines appear 
to corroborate the conclusions from testing that persistent U-substrate colloid suspensions are

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MDL-EBS-PA-000004 REV 00 128 June 2003 
unlikely to form (Section 6.3.1.2.4). Studies in the literature (Short et al. 1988 [DIRS 113937]; 
Payne et al. 1992 [DIRS 124812]; Vilks et al. 1993 [DIRS 108261]; Znker et al. 2000 [DIRS 
162746]) suggest that no significant primary U-bearing colloids have been observed in the 
vicinities of uranium and other types of mines under repository-relevant conditions. 
Criterion 4 (Relevant to Technical Work Plan Validation Criteria 1 and 2) 
Is the model approach used, which stipulates that DOE SNF will not produce colloids in 
significant quantities, consistent with DOE SNF-specific test results and peer-reviewed literature 
on field observations near uranium mines and deposits? 
Degradation tests on metallic uranium fuel, one type of DOE SNF, have resulted in the rapid 
breakdown of the fuel to abundant particles, some as small as colloids (Section 6.3.1.2.2). The 
particle compositions were primarily meta-schoepite and UO2 as well as smectite (see below). 
The conclusion that these types of colloids from DOE SNF degradation will not persist in the 
repository setting is based on arguments similar to those presented under Criterion 3. It is 
corroborated with data from a recent set of experiments that characterized the mineralogy, size 
characteristics, and stability of particles in a U-bearing-colloid dispersion, and with field 
observations. The reader is referred to the discussion in Criterion 3. 
The majority (approximately 90%) of the total waste slated for the repository is commercial 
spent nuclear fuel, with approximately 8% of the total being co-disposed defense high-level 
waste glass and DOE SNF and less than two percent being Naval Fuel (DOE 2002 [DIRS 
155943], Table 3-3). It is currently planned that of the DOE waste approximately two-thirds will 
be defense high-level waste glass and DOE SNF will constitute about one-third (Lytle 1995 
[DIRS 104398]). Therefore, DOE SNF would constitute less than three percent of the total 
repository waste inventory. N Reactor fuel comprises approximately 85% of the DOE SNF 
inventory (DOE 2002 [DIRS 158405]) and is the surrogate for DOE SNF in the TSPA-LA 
model. As stated previously, during degradation testing uranium metal has undergone rapid 
oxidation, breaking down to abundant particulate corrosion products including colloids. The 
colloids range from UO2 to higher oxides of U to U- and Pu-bearing smectite. Preliminary 
findings from testing on the degradation of DOE SNF (Section 6.3.1.2.2) suggest that the U 
concentrations associated with colloids (either U oxides or smectite or both) can be high. In 
summary, these lines of evidence support the conclusion that although some primary uranium 
colloids may form from degradation of DOE SNF, colloid-related U transport will not be a major 
contributor to radionuclide transport. Further investigation may be necessary to ascertain the 
growth and potential contribution to release of Pu-bearing smectite. 
ConclusionBased on the discussions presented under Criteria 1 through 4, it is concluded that 
the waste form colloid concentration values appear to conform with accepted scientific principles 
with respect to colloid suspensions, and they are reasonable with respect to observations of 
colloids of similar mineralogy in the Project and peer-reviewed literature (Criterion 1). The 
stipulation that commercial and DOE SNF (Criteria 3 and 4) do not produce colloids in 
significant quantities is corroborated by the few observations of colloids in the vicinity of 
uranium mines and deposits. The applicability of the conditions of the defense high-level waste 
glass tests to repository conditions (Criterion 2) has been evaluated by considering the 
physicochemical properties of smectite colloids, similarities between test conditions and the

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MDL-EBS-PA-000004 REV 00 129 June 2003 
probable microenvironment at the degrading glass surface, and uncertainty in Pu concentration 
by using a bounding value believed to be conservative. It is therefore concluded that the 
validation activities performed for building confidence in the model elements and data discussed 
have sufficiently strong scientific bases, and that Criteria 1 through 4 used to determine that the 
required level of confidence in the model have been achieved. 
7.2 CORROSION PRODUCT COLLOID PARAMETERS 
Criterion 5 (Relevant to Technical Work Plan Validation Criterion 2) 
Is the range of 0.05 to 50 mg/L adopted for maximum iron oxyhydroxide colloid concentrations 
from corrosion of ferrous repository materials reasonable, considering the lack of relevant peerreviewed 
literature? 
Iron oxyhydroxide colloids are expected to form as a result of internal and external corrosion of 
the waste package and associated engineered barrier system components (Section 6.3.1.3). There 
are few, if any, peer-reviewed publications that present information on colloid concentrations as 
a function of aqueous chemistry. For the colloid model, a reasonable estimate was made based 
on expert judgment, corroborated by laboratory experiments investigating the corrosion of 
small-scale waste package replicas, and by maximum colloid concentrations observed in 
groundwater. 
The range of values for maximum iron oxyhydroxide colloids concentration, 0.05 to 50 mg/L, 
was chosen so that it was substantially greater than iron oxyhydroxide colloid levels found in 
groundwater, but high enough to reflect the masses of corroded ferrous metal anticipated in the 
repository. Additionally, the value acknowledges the high end of the range of colloids in general 
reported in groundwaters. 
Research at the University of Nevada at Las Vegas have been studying the corrosion 
characteristics of miniature stainless steel waste packages and has characterized the quantities of 
corrosion particles produced with a variety of aqueous chemical conditions (Sections 6.3.1.3 and 
6.3.2.3). While the measured colloid quantities may not be directly transferable to colloid model 
quantities, the experiments suggest that abundant colloids will be produced (as much as 20 mg/L 
in the first four weeks of the experiment (DTN: MO0212UCC034JC.002) [DIRS 161457]). 
Further, it has been demonstrated in every case in which a hole has been placed in a canister to 
simulate a breach that the hole, after passing quantities of corrosion particles, relatively quickly 
plugs with corrosion product and effectively seals against further outflows. The stipulation that 
continuous production and outflow of colloids in the waste package would continue unimpeded 
is therefore considered conservative. 
ConclusionBased on this line of reasoning, the value chosen for continuous production of 
corrosion-generated iron oxyhydroxide colloids over the regulatory period is reasonable and 
realistic. This value is perhaps on the high side (conservative with respect to mobility of 
attached radionuclides). The production of iron oxyhydroxides has been corroborated by 
laboratory-scale waste package corrosion tests. The stipulation that colloid production will 
continue unimpeded from the waste packages as corrosion proceeds is probably conservative, 
based on the observations that small apertures in the waste package become plugged and prevent

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MDL-EBS-PA-000004 REV 00 130 June 2003 
subsequent corrosion products from passing through the aperture. It is concluded that the criteria 
established to achieve the required level of confidence in the model have been satisfied. 
7.3 SEEPAGE WATER/GROUNDWATER COLLOID PARAMETERS 
Criterion 6 (Relevant to Technical Work Plan Validation Criteria 1 and 2) 
Is the determined range and distribution for concentrations of groundwater colloids, based on a 
limited set of Yucca Mountain-vicinity data, reasonable? 
Several hydrologic investigations in the Yucca Mountain vicinity have yielded a quantity of data 
on groundwater chemistry and colloid content (cf. Kingston and Whitbeck 1991 [DIRS 113930]; 
DTNs listed in Section 6.3.2.5). Most of the colloid data include information on total colloid 
concentrations and concentrations of several size ranges. Aqueous parameters such as major ion 
concentration, ionic strength, and pH were obtained for many of the samples. These data have 
been used in the colloid model to provide a colloid concentration range as a function of ionic 
strength. Validation of the groundwater colloid data used in the colloid model was accomplished 
by corroborating the mean, range, and distribution by comparison of independently generated 
subsets within the overall data set (see Section 6.3.2.5 and Figures 11 and 12), and with similar 
data from several different sites and geologic settings around the world (see CRWMS M&O 
2001 [DIRS 153933], Figure 9). 
ConclusionThe groundwater colloid data are site-specific, have been bounded conservatively 
and realistically, are internally consistent, and are determined to be similar to colloid 
concentration data from disparate geologic terrains around the world. Therefore the criteria 
established to achieve the required level of confidence in the established distribution in 
groundwater colloid concentrations have been satisfied. 
7.4 RADIONUCLIDE SORPTION CHARACTERISTICS 
Criterion 7 (Relevant to Technical Work Plan Validation Criterion 1) 
Is the stipulation that Pu is embedded or otherwise irreversibly sorbed to defense high-level waste 
glass colloids reasonable and conservative with respect to radionuclide mobility? 
The assumption of embedded Pu in smectite waste form colloids is based on the results of 
defense high-level waste glass degradation testing at Argonne National Laboratory (see 
Section 5, Assumption 5.5 and Section 6.3.1.1). Data derived from the testing indicated that Pu 
was associated with the colloids. The colloid-associated Pu concentrations were quantified, 
although the mechanisms of attachment or incorporation were not determined. Validation of 
these one-of-a-kind data can only be accomplished by noting the similar results from repeated 
sample analyses and the professional judgment of the investigators regarding the Pu-colloid 
association. The stipulation that the Pu is permanently attached, whatever the mechanism of 
attachment, is conservative, as it effectively increases the potential mobility of the Pu.

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MDL-EBS-PA-000004 REV 00 131 June 2003 
Criterion 8 (Relevant to Technical Work Plan Validation Criteria 1 and 2) 
Is the use of a modeling approach in which a large fraction of Pu sorbed onto iron oxyhydroxide 
pseudocolloids is irreversibly sorbed reasonable? 
A modeling approach is taken to characterize sorption onto iron oxyhydroxide colloids in which 
a large fraction of sorbed Pu effectively becomes permanently sorbed (see Section 6.3.3.2). This 
approach is validated by laboratory experiments, which show almost complete retention of Pu 
onto iron oxyhydroxide colloids over the duration of the experiments (up to approximately 
6 months), and field observations (over periods up to about 50 years), which indicate that soils 
strongly bind Pu, leaving little dissolved Pu in the pore fluids (see Section 6.3.3.2). Based on 
these observations it is concluded that providing for this type of irreversible attachment in the 
abstraction is reasonable and justified. 
Criterion 9 (Relevant to Technical Work Plan Validation Criteria 1 and 2) 
Are the distribution coefficients for radionuclides onto colloids (Kd values) reasonable and 
supported by peer-reviewed literature and analytical modeling results? 
The Kd value ranges chosen for reversibly attached radionuclides are based on Project laboratory 
results and peer-reviewed literature, which are described in detail in Section 6.3.3. Validation of 
Kd values for several radionuclides adopted in the abstraction, and particularly validation of the 
use of published literature, was accomplished by considering alternative calculations for 
determining effective Kd values. Table 10 lists the radionuclides to which Kd values have been 
assigned in this model report. Tables 6, 7, and 8 list colloid types and Kd values based on the 
Los Alamos National Laboratory results and literature review (see Section 6.3.3.1). Table 9 lists 
Kd values which are the results of modeling described by Honeyman and Ranville (2002 [DIRS 
161657], from Figure 7-5). As described in Section 6.3.3.1, Yucca Mountain vicinity-specific 
colloid concentrations and groundwater chemistry from Kingston and Whitbeck (1991 [DIRS 
113930]) were used as input to a mechanistic sorption model and surface complexation 
calculations. The Kd ranges vary in part as a function of colloid concentration, which ranged 
from 0.1 to 100 mg/L. 
Comparison among the Kd values listed in Tables 6, 7, and 8; and the modeled Kd values in 
Table 9 indicates that there is rather good agreement between the literature- and observationbased 
Kd values and those derived from mechanistic model calculations for Pu, Am, U, and Np; 
these data may be considered mutually corroborative, assuming a fairly high degree of 
uncertainty. 
ConclusionThe modeling approach regarding the three types of radionuclide attachment to 
colloids (Criteria 7 through 9) either have strong scientific bases (Criteria 8 and 9) or are 
conservative with respect to radionuclide mobility (Criterion 7). It is concluded that these 
criteria, used to determine that the required level of confidence in the model, have been satisfied.

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MDL-EBS-PA-000004 REV 00 132 June 2003 
7.5 PROPAGATION OF MODEL UNCERTAINTY THROUGH ABSTRACTION 
Criterion 10 (Not Specifically Relevant to any Criteria Specified in the Technical Work 
Plan) 
Has model uncertainty been propagated throughout the abstraction satisfactorily? 
Ranges and distributions are provided to TSPA-LA to represent uncertainties of input 
parameters. The abstraction logic is provided along with the parameters to total system 
performance assessment. Within the TSPA-LA model, the abstraction implementation 
incorporates the parameter uncertainties with Monte Carlo simulation techniques. In this way 
parameter uncertainties are propagated throughout the abstraction during computation and are 
reflected in the calculated results. 
ConclusionUncertainty propagation throughout the abstraction has been addressed by means 
of the methodology of incorporating the abstraction into the TSPA-LA calculations. It is 
concluded that the level of confidence required of the model has been achieved through the use 
of this methodology. 
7.6 PROCESSES NOT INCORPORATED INTO THE ABSTRACTION 
Certain processes were not incorporated into the abstraction, including filtration of colloids in the 
waste package, sorption to the air-water interfaces in unsaturated environments, and gravitational 
settling. It was considered realistic and conservative to do so. It may be argued that 
gravitational settling would facilitate the exit of colloids from a breach at the bottom of the waste 
package; the net effect, however, is the same. 
ConclusionOmission of these processes is conservative, in that it maximizes the mobility of 
colloids and associated radionuclides. 
7.7 VALIDATION ACTIVITIES EXTENDING BEYOND CURRENT 
DOCUMENTATION OF THE MODEL 
The disposition of the various validation criteria described in Sections 7.1 through 7.5 is that the 
level of confidence required for validation of the various components considered in this model 
analysis has been achieved. No further validation activities are needed to complete the models 
validation for its intended use. 
8. CONCLUSIONS 
8.1 SUMMARY OF MODEL AND ITS IMPLEMENTATION 
The colloids process models for the waste form and engineered barrier system components of the 
TSPA-LA model describe the types and concentrations of colloids that could potentially be 
generated in the waste package from degradation of the waste forms and the corrosion of the 
waste package materials and the concentrations of colloids present in natural waters in the 
vicinity of Yucca Mountain that could potentially come in contact with the repository waste. In 
addition, stability and sorption/desorption mechanisms and transport characteristics of colloids

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MDL-EBS-PA-000004 REV 00 133 June 2003 
anticipated in the repository are addressed, based on the range in geochemical conditions 
anticipated in the repository environment within the regulatory compliance period. 
The types and quantities of colloid formed from the degradation of defense high-level waste 
glass, commercial and DOE SNF are based largely on ongoing experimental work at Argonne 
National Laboratory and appropriate studies, albeit limited, documented in the open literature. 
The quantities and characteristics of defense high-level waste glass are well documented based 
on several years of research at Argonne National Laboratory (see Section 6.3.1.1). The colloids 
formed from the degradation products of high-level waste glass have been shown to be primarily 
smectite clay containing discrete radionuclide-bearing phases, which are incorporated in the clay. 
These embedded radionuclides are stipulated to be permanently fixed in the clay particles and 
therefore are modeled as irreversible sorbed colloids that will be transported with the colloids 
and will not be detached from the colloid particles. 
There are no direct colloid source term contributions from commercial and DOE SNF wastes in 
the TSPA-LA model. Argonne National Laboratory investigations (described in Section 6.3.1.2) 
indicate the formation of some quantities of stable colloids. However, these research findings 
are too preliminary at this time to incorporate into the TSPA-LA model. Specifically, U colloids 
that have been observed to form are meta-schoepite or other oxyhydroxides that are soluble at 
(more dilute) anticipated repository chemical conditions. Consequently, these colloids will 
eventually dissolve, in part because of their very small size and large reactive surface area, and in 
part because of increasingly dilute groundwater conditions away from the waste package and 
drift. The model is set up such that the U will be present within the engineered barrier system as 
U aqueous complexes and not associated with colloids. Therefore, commercial and DOE SNF 
degradation is accommodated in the colloid model with the stipulation that degradation-product 
U will occur entirely as aqueous complexes and will be transported with the fluid within the 
breached WP and released into the drift. U sorption onto stationary corrosion materials is 
modeled within the waste package, but this process is ignored in the engineered barrier system 
outside the waste package. This approach was taken because of the uncertainty in the quantity 
and physical/chemical characteristics of the drift stationary corrosion materials and also because 
ignoring sorption onto these materials would lead to a more pessimistic contribution to the dose 
calculations by U. 
The TSPA-LA colloid model has been constructed in such a way that a large fraction of 
dissolved Pu and Am sorbed onto colloids is irreversibly sorbed (i.e., is embedded within or 
becomes permanently attached) and the remainder is reversibly sorbed according to an 
equilibrium Kd value model with a small fraction occurring as dissolved species. Further, a 
parameter (the target-flux out ratio, FRN) defines the ratio of Pu and Am mass sorbed to colloids 
(irreversibly and reversibly) to the total Pu and Am mass leaving the waste package (sorbed to 
colloids plus dissolved). This ratio ranges between 0.9 and 0.99. Additionally, sorption to 
immobile iron oxyhydroxide corrosion products is modeled. The difference in specific surface 
areas between the colloids and the stationary corrosion products is taken into account. 
Allocating a fraction of the total Pu and Am onto the stationary corrosion products would reduce 
the quantity of Pu and Am transported by colloids, but some degree of sorption onto stationary 
corrosion products is realistic.

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MDL-EBS-PA-000004 REV 00 134 June 2003 
Stability of all colloids (smectite, both natural seepage water/groundwater colloids and those 
formed from defense high-level waste glass degradation products, and iron oxyhydroxide 
colloids formed from steel corrosion) is evaluated based on solution chemistry, specifically ionic 
strength and pH (Section 6.3.2). 
In the TSPA-LA model, natural seepage water/groundwater colloids are stipulated to come in 
contact with and enter breached waste packages and will subsequently sorb radionuclides. The 
resulting pseudocolloid (radionuclide complexes) will subsequently be subjected to transport 
from the engineered barrier system to the downstream unsaturated and saturated zones. 
Furthermore, in contrast to the modeling effort for the TSPA-SR, wherein colloid concentration 
parameters were based upon data from groundwaters around the world (Degueldre et al. 2000 
[DIRS 153651], DTN: SNT05080598002.001 [DIRS 162744], more recent data from 
groundwater samples collected from wells within the Yucca Mountain area and Idaho National 
Engineering and Environmental Laboratory are used to develop the parameters used for the 
TSPA-LA. These data suggested higher seepage water/groundwater colloids concentrations 
(perhaps as high as one to two orders of magnitude greater than those used previously in the 
TSPA-SR) and are appropriate for the TSPA-LA model calculations. 
Recent experimental work on the corrosion of miniature steel waste packages have provided 
needed data on the probable concentrations of iron oxyhydroxide colloids that might be expected 
within the engineered barrier system upon contact of seepage water and subsequent corrosion of 
the waste packages. These data indicate that values as high as 50 mg/L should be sampled in the 
TSPA-LA model calculations. These high values represent a reasonable maximum for iron 
oxyhydroxide colloid releases from a waste package following a potential breach (Section 
6.3.2.3). 
In summary: 
 A model has been developed for TSPA-LA to calculate radionuclide and colloid mass 
concentrations as a function of fluid chemistry (ionic strength and pH), dissolved 
radionuclide concentrations, and sorption characteristics of the radionuclides. Colloids 
from waste form degradation, corrosion of steel repository components, and seepage 
water/groundwater are included in the model. 
 The abstraction incorporates bounding data and relationships that are based on the results 
colloid-related research programs (both laboratory and field) conducted at Argonne 
National Laboratory and Los Alamos National Laboratory. 
 The abstraction is intended to be conservative and realistic. 
There are several significant sources of uncertainty attached to this abstraction. The potential 
formation of colloids from degradation of N-Reactor fuel, and the potential contribution of these 
colloids to repository performance, bears further investigation. For now, the position is taken 
that, due to the small quantity of N-Reactor fuel in a codisposal canister, radionuclide-bearing 
colloids generated from degradation of N-Reactor fuel will add little to the releases provided by 
defense high-level waste glass.

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MDL-EBS-PA-000004 REV 00 135 June 2003 
In degradation testing of commercial SNF, rinds were observed containing fine-grained Pubearing 
particles and U silicates. Spallation of the rinds did not occur during the tests but could 
possibly spall under different test conditions. Given the large quantity of commercial SNF 
planned for the repository, the possible fate of Pu-rich rinds also bears further investigation. 
The abstraction is considered valid and usable in TSPA-LA calculations for any time after the 
temperature in the repository has decreased to below boiling after the thermal pulse. Many of 
the waste degradation tests were performed at 90C, but colloids produced were mostly sampled 
at near room temperature. Therefore the test results may be applied to this post-thermal period. 
The range of ionic strength and pH for which colloid masses and stability are calculated in the 
abstraction are within the ranges anticipated from in-package chemistry calculations and 
abstraction. 
In general, the bounding relationships employed in the abstraction incorporate uncertainty 
present in the data to formulate the abstraction. Additional uncertainty may result from the 
TSPA-LA model and the ways in which the dose calculations are performed. For example, the 
choices of distributions and the method of sampling specific distributions may result in 
uncertainties in determination of colloid concentrations, ionic strength, pH, and radionuclide 
concentrations. 
8.2 MODEL OUTPUTS 
Developed data for use directly by the TSPA-LA calculations or other submodel components in 
the TSPA-LA model calculations include both intermediate parameters (see Table 16 for 
parameter listing and associated DTNs) and model output parameters (see Table 17). 
In the colloid model abstraction, several parameters are calculated with TSPA-LA model as 
outputs from the model and are passed to the unsaturated zone component of TSPA-LA to be 
used as inputs. These colloid model outputs are listed and described in Table 18. 
The parameters calculated as intermediate results within the TSPA-LA model calculations are 
listed in Table 16. 
Table 18. Summary of Model Output Parameters 
Parameter 
Name Parameter Description Units Basis for Value/ Source Value/Range/ 
Distribution 
CRncoll,wf,embed 
CRncoll,wf,rev 
CRncoll,FeOx,irrev 
CRncoll,FeOx,rev 
CRncoll,gw 
Concentration of mobile 
colloidal radionuclide 
element RN per unit volume 
or mass of water 
mol/L Determined in PA 
calculation; Figure 21 
Calculated at each 
time step; uncertainty 
propagated through 
the TSPA-LA model 
calculations 
NOTE: PA = performance assessment; RN = radionuclide. 
Additionally, parameters developed in this analysis for use elsewhere in the TSPA-LA model 
include waste form colloid mass concentrations (derived from defense high-level waste glass), 
corrosion product colloid mass concentrations, Kd values for selected radionuclides onto smectite 
and iron oxyhydroxide colloids, and specific surface area on iron oxyhydroxide colloids.

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MDL-EBS-PA-000004 REV 00 136 June 2003 
Developed DTNs include: SN0304T0504103.001, SN0304T0504103.002, 
SN0304T0504103.003 and SN0304T0504103.004 (see Table 16). 
The uncertainties associated with the output parameters result from propagation of the individual 
aleatoric uncertainties (explicitly represented by ranges and distributions, and implicitly 
represented by bounding values) of the inputs and epistemic uncertainty (implicit uncertainty in 
the model elements) through the TSPA-LA model calculations. The TSPA-LA model represents 
a parameter uncertainty with a probability distribution. The aggregate uncertainties associated 
with the individual inputs are translated into output uncertainties, using Monte Carlo simulation, 
by sampling all of the parameters probability distributions for each of a large number of 
realizations. The overall effects of the input uncertainties on the outputs are estimated 
(approximated) from observation of the output parameter ranges resulting from the realizations. 
9. INPUTS AND REFERENCES 
9.1 DOCUMENTS CITED 
Aguilar, R. 2003. "P&CE Model Report Citation in MDL-EBS-PA-000004 Rev 00D." E-Mail 
from R. Aguilar to T. Reeder, June 13, 2003. ACC: MOL.20030615.0217. [DIRS 163770] 
Aguilar, R.; Papenguth, H.W.; and Rigby, F. 1999. "Retardation of Colloidal Actinides through 
Filtration in Intrusion Borehole Backfill at the Waste Isolation Pilot Plant (WIPP)." Actinide 
Speciation in High Ionic Strength Media, Experimental and Modeling Approaches to Predicting 
Actinide Speciation and Migration in the Subsurface, Proceedings of an American Chemical 
Society Symposium on Experimental and Modeling Studies of Actinide Speciation in Non-ideal 
Systems, held August 26-28, 1996, in Orlando, Florida. Reed, D.T.; Clark, S.B.; and Rao, L.; 
eds. Pages 215-225. New York, New York: Kluwer Academic/Plenum Publishers. TIC: 253961. 
[DIRS 161648] 
Beyenal, H. and Lewandowski, Z. 2000. "Combined Effect of Substrate Concentration and Flow 
Velocity on Effective Diffusivity in Biofilms." Water Research, 34, (2), 528-538. [New York, 
New York]: Elsevier. TIC: 253702. [DIRS 161652] 
Brady, P.V.; Jov-Colon, C.F.; Carr, G.; and Huang, F. 2002. "Soil Radionuclide Plumes." 
Chapter 8 of Geochemistry of Soil Radionuclides. Zhang, P-C., and Brady, P.V., eds. SSSA 
Special Publication Number 59. Madison, Wisconsin: Soil Science Society of America. TIC: 
253952. [DIRS 161649] 
BSC (Bechtel SAIC Company) 2001. Inventory Abstraction. ANL-WIS-MD-000006 REV 00 
ICN 02. Las Vegas, Nevada: Bechtel SAIC Company. ACC: MOL.20010416.0088. 
[DIRS 154841] 
BSC 2001. Technical Work Plan for Saturated Zone Flow and Transport Modeling and Testing. 
TWP-NBS-MD-000001 REV 02. Las Vegas, Nevada: Bechtel SAIC Company. ACC: 
MOL.20010924.0269. [DIRS 156308]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 137 June 2003 
BSC 2002. Risk Information to Support Prioritization of Performance Assessment Models. TDRWIS-
PA-000009 REV 01 ICN 01. Las Vegas, Nevada: Bechtel SAIC Company. ACC: 
MOL.20021017.0045. [DIRS 160780] 
BSC 2002. Technical Work Plan for Waste Form Degradation Modeling, Testing, and Analyses 
in Support of SR and LA. TWP-WIS-MD-000008 REV 02. Las Vegas, Nevada: Bechtel SAIC 
Company. ACC: MOL.20020819.0359. [DIRS 160779] 
BSC 2002. Technical Work Plan for: Engineered Barrier System Department Modeling and 
Testing, FY 02 Work Activities. TWP-MGR-MD-000015 REV 02. Las Vegas, Nevada: Bechtel 
SAIC Company. ACC: MOL.20021014.0209. [DIRS 160315] 
BSC 2002. Technical Work Plan for: Performance Assessment Unsaturated Zone. TWP-NBSHS-
000003 REV 02. Las Vegas, Nevada: Bechtel SAIC Company. ACC: MOL.20030102.0108. 
[DIRS 160819] 
BSC 2002. Test Plan for: Laboratory Sorption Measurements  UZ and SZ. SITP-02-UZ-011 
REV 00. Las Vegas, Nevada: Bechtel SAIC Company. ACC: MOL.20020225.0261. [DIRS 
158197] 
BSC 2002. Test Plan for: Laboratory Sorption Measurements-SZ. SITP-02-SZ-004 REV 01. Las 
Vegas, Nevada: Bechtel SAIC Company. ACC: MOL.20020906.0298. [DIRS 161535] 
BSC 2002. Test Plan Waste form Colloids Characterization and Concentration Studies. SITP- 
02-WF-003 REV 00. Las Vegas, Nevada: Bechtel SAIC Company. ACC: MOL.20020402.0443. 
[DIRS 161534] 
BSC 2002. The Enhanced Plan for Features, Events, and Processes (FEPs) at Yucca Mountain. 
TDR-WIS-PA-000005 REV 00. Las Vegas, Nevada: Bechtel SAIC Company. ACC: 
MOL.20020417.0385. [DIRS 158966] 
BSC 2003. Dissolved Concentrations of Radioactive Elements. ANL-WIS-MD-000010 REV 02. 
Las Vegas, Nevada: Bechtel SAIC Company. URN-1089 [DIRS 163152] 
BSC 2003. EBS Radionuclide Transport Abstraction. ANL-WIS-PA-000001 REV 01A. Las 
Vegas, Nevada: Bechtel SAIC Company. ACC: MOL.20030617.0222. TBV-5179 [DIRS 
163935] 
BSC 2003. In-Package Chemistry Abstraction. ANL-EBS-MD-000037 REV 02B. Las Vegas, 
NV: Bechtel SAIC Company. ACC: MOL.20030617.0224. TBV-5175. [DIRS 163919] 
BSC 2003. Particle Tracking Model and Abstraction of Transport Processes. MDL-NBS-HS- 
000020 REV 00A. Las Vegas, Nevada: Bechtel SAIC Company. ACC: MOL.20030611.0040. 
TBV-5181 [DIRS 163933] 
BSC 2003. Saturated Zone Colloid Transport. ANL-NBS-HS-000031 REV 01A. Las Vegas, 
Nevada: Bechtel SAIC Company. ACC: MOL.20030602.0288. TBV-5180 [DIRS 163932]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 138 June 2003 
BSC 2003. Software Code: GoldSim. 7.50.100. PC. 10344-7.50.100-00. [DIRS 161572] 
Buck, E.C. 2003. "Transmittal of Draft Alternative Conceptual Model for Colloid Generation 
from Commerical Spent Nuclear Fuel, Pacific Northwest National Laboratory." Interoffice 
memorandum from E. C. Buck (BSC) to Y. Chen, June 17, 2003, 0613037655, with attachment. 
ACC: MOL.20030617.0258. TBV-5182 [DIRS 163117] 
Buck, E.C. and Bates, J.K. 1999. "Microanalysis of Colloids and Suspended Particles from 
Nuclear Waste Glass Alteration." Applied Geochemistry, 14, 635-653. [New York, New York]: 
Elsevier. TIC: 245946. [DIRS 109494] 
Buddemeier, R.W. and Hunt, J.R. 1988. "Transport of Colloidal Contaminants in Groundwater: 
Radionuclide Migration at the Nevada Test Site." Applied Geochemistry, 3, 535-548. Oxford, 
England: Pergamon Press. TIC: 224116. [DIRS 100712] 
Buffle, J.; Wilkinson, K.J.; Stoll, S.; Filella, M.; and Zhang, J. 1998. "A Generalized Description 
of Aquatic Colloidal Interactions: The Three-Colloidal Component Approach." Environmental 
Science & Technology, 32, (19), 2887-2899. [Washington, D.C.]: American Chemical Society. 
TIC: 253710. [DIRS 161653] 
Bunzl, K.; Flessa, H.; Kracke, W.; and Schimmack, W. 1995. "Association of Fallout 239+240Pu 
and 241Am with Various Soil Components in Successive Layers of a Grassland Soil." 
Environmental Science & Technology, 29, (10), 2513-2518. Washington, D.C.: American 
Chemical Society. TIC: 234160. [DIRS 154468] 
Contardi, J.S.; Turner, D.R.; and Ahn, T.M. 2001. "Modeling Colloid Transport for Performance 
Assessment." Journal of Contaminant Hydrology, 47, ([2-4]), 323-333. [New York, New York]: 
Elsevier. TIC: 253918. [DIRS 162732] 
Coughtrey, P.J.; Jackson, D.; Jones, C.H.; Kane, P.; and Thorne, M.C. 1985. Radionuclide 
Distribution and Transport in Terrestrial and Aquatic Ecosystems, A Compendium of Data. 
Volume 6. Rotterdam, The Netherlands: A.A. Balkema. TIC: 240299. [DIRS 154494] 
CRWMS M&O 2000. In-Drift Colloids and Concentration. ANL-EBS-MD-000042 REV 00. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000509.0242. [DIRS 129280] 
CRWMS M&O 2000. In-Drift Microbial Communities. ANL-EBS-MD-000038 REV 00 ICN 01. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20001213.0066. [DIRS 151561] 
CRWMS M&O 2000. Summary of In-Package Chemistry for Waste Forms. ANL-EBS-MD- 
000050 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000217.0217. [DIRS 
111880] 
CRWMS M&O 2000. Total System Performance Assessment for the Site Recommendation. 
TDR-WIS-PA-000001 REV 00 ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20001220.0045. [DIRS 153246]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 139 June 2003 
CRWMS M&O 2000. Unsaturated Zone and Saturated Zone Transport Properties (U0100). 
ANL-NBS-HS-000019 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000829.0006. [DIRS 152773] 
CRWMS M&O 2001. Colloid-Associated Radionuclide Concentration Limits: ANL. ANL-EBSMD-
000020 REV 00 ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20010216.0003. 
[DIRS 154071] 
CRWMS M&O 2001. Waste Form Colloid-Associated Concentrations Limits: Abstraction and 
Summary. ANL-WIS-MD-000012 REV 00 ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20010130.0002. [DIRS 153933] 
Davis, J.A. and Kent, D.B. 1990. "Surface Complexation Modeling in Aqueous Geochemistry." 
Mineral-Water Interface Geochemistry. Hochella, M.F., Jr. and White, A.F., eds. Reviews in 
Mineralogy Volume 23. Pages 177-260. Washington, D.C.: Mineralogical Society of America. 
TIC: 224085. [DIRS 143280] 
Degueldre, C.; Triay, I.; Kim, J-I; Vilks, P.; Laaksoharju, M.; and Miekeley, N. 2000. 
"Groundwater Colloid Properties: A Global Approach." Applied Geochemistry, 15, ([7]), 1043- 
1051. [New York, New York]: Pergamon Press. TIC: 249340. [DIRS 153651] 
DOE (U.S. Department of Energy) 2002. DOE Spent Nuclear Fuel Information in Support of 
TSPA-SR. DOE/SNF/REP-047, Rev. 2. Idaho Falls, Idaho: U.S. Department of Energy, Idaho 
Operations Office. TIC: 252089. [DIRS 158405] 
DOE (U.S. Department of Energy) 2002. Yucca Mountain Science and Engineering Report. 
DOE/RW-0539, Rev. 1. Washington, D.C.: U.S. Department of Energy, Office of Civilian 
Radioactive Waste Management. ACC: MOL.20020404.0042. [DIRS 155943] 
DOE (U.S. Department of Energy) 2003. Quality Assurance Requirements and Description. 
DOE/RW-0333P, Rev. 13. Washington, D.C.: U.S. Department of Energy, Office of Civilian 
Radioactive Waste Management. ACC: DOC.20030422.0003. [DIRS 162903] 
Dzombak, D.A. and Morel, F.M.M. 1987. "Adsorption of Inorganic Pollutants in Aquatic 
Systems." Journal of Hydraulic Engineering, 113, (4), 430-474. New York, New York: 
American Society of Civil Engineers. TIC: 245735. [DIRS 109505] 
Dzombak, D.A. and Morel, F.M.M. 1990. Surface Complexation Modeling, Hydrous Ferric 
Oxide. New York, New York: John Wiley & Sons. TIC: 224089. [DIRS 105483] 
Ebert, W.L. 1995. The Effects of the Glass Surface Area/Solution Volume Ratio on Glass 
Corrosion: A Critical Review. ANL-94/34. Argonne, Illinois: Argonne National Laboratory. 
TIC: 215400. [DIRS 113219] 
EPA (U.S. Environmental Protection Agency) 1999. Understanding Variation in Partition 
Coefficient, Kd, Values. EPA 402-R-99-004A&B Two volumes. Washington, D.C.: U.S. 
Environmental Protection Agency. TIC: 249201. TBV-5183 [DIRS 147475]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 140 June 2003 
Fontes, D.E.; Mills, A.L.; Hornberger, G.M.; and Herman, J.S. 1991. "Physical and Chemical 
Factors Influencing Transport of Microorganisms Through Porous Media." Applied and 
Environmental Microbiology, 57, (9), 2473-2481. [Washington, D.C.]: American Society for 
Microbiology. TIC: 247563. [DIRS 147337] 
Freeze, G.A.; Brodsky, N.S.; and Swift, P.N. 2001. The Development of Information Catalogued 
in REV00 of the YMP FEP Database. TDR-WIS-MD-000003 REV 00 ICN 01. Las Vegas, 
Nevada: Bechtel SAIC Company. ACC: MOL.20010301.0237. [DIRS 154365] 
Hahn, H.H. and Stumm, W. 1970. "The Role of Coagulation in Natural Waters."American 
Journal of Science, 268, (4), 354-368. [New Haven, Connecticut: Yale University, Kline 
Geology Laboratory]. TIC: 253963. [DIRS 161656] 
Harvey, R.W.; George, L.H.; Smith, R.L.; and LeBlanc, D.R. 1989. "Transport of Microspheres 
and Indigenous Bacteria Through a Sandy Aquifer: Results of Natural- and Forced-Gradient 
Tracer Experiments." Environmental Science & Technology, 23, (1), 51-56. [Washington, D.C.]: 
American Chemical Society. TIC: 224869. [DIRS 147338] 
Hersman, L. 1995. Microbial Effects on Colloidal Agglomeration. LA-12972-MS. Los Alamos, 
New Mexico: Los Alamos National Laboratory. ACC: MOL.19971210.0253. [DIRS 100750] 
Hersman, L.E. 1997. "Subsurface Microbiology: Effects on the Transport of Radioactive Wastes 
in the Vadose Zone." Chapter 16 of The Microbiology of the Terrestrial Deep Subsurface. Amy, 
P.S. and Haldeman, D.L., eds. Boca Raton, Florida: CRC Lewis Publishers. TIC: 232570. 
[DIRS 100763] 
Honeyman, B.D. and Ranville, J.F. 2002. "Colloid Properties and their Effects on Radionuclide 
Transport through Soils and Groundwaters." Chapter 7 of Geochemistry of Soil Radionculides. 
Zhang, P-C. and Brady, P.V., eds. SSSA Special Publication Number 59. Madison, Wisconsin: 
Soil Science Society of America. TIC: 253952. TBV-5184 [DIRS 161657] 
Jenne, E.A. 1998. "Adsorption of Metals by Geomedia: Data Analysis, Modeling, Controlling 
Factors, and Related Issues." Adsorption of Metals by Geomedia. Jenne, E.A, ed. Pages 1-73. 
San Diego, California: Academic Press. TIC: 254037. [DIRS 162328] 
Kersting, A.B.; Efurd, D.W.; Finnegan, D.L.; Rokop, D.J.; Smith, D.K.; and Thompson, J.L. 
1999. "Migration of Plutonium in Ground Water at the Nevada Test Site." Nature, 397, ([6714]), 
56-59. [London, England: Macmillan Journals]. TIC: 243597. [DIRS 103282] 
Kim, J.I. 1994. "Actinide Colloids in Natural Aquifer Systems." MRS Bulletin, 19, (12), 47-53. 
Pittsburgh, Pennsylvania: Materials Research Society. TIC: 246128. [DIRS 109521] 
Kim, S. and Corapcioglu, M.Y. 1996. "A Kinetic Approach to Modeling Mobile Bacteria- 
Facilitated Groundwater Contaminant Transport." Water Resources Research, 32, (2), 321-331. 
Washington, D.C.: American Geophysical Union. TIC: 247566. [DIRS 147342]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 141 June 2003 
Kingston, W.L. and Whitbeck, M. 1991. Characterization of Colloids Found in Various 
Groundwater Environments in Central and Southern Nevada. DOE/NV/10384-36. [Las Vegas, 
Nevada]: Desert Research Institute, Water Resources Center. ACC: NNA.19930607.0073. 
[DIRS 113930] 
Laaksoharju, M.; Degueldre, C.; and Skarman, C. 1995. Studies of Colloids and Their 
Importance for Repository Performance Assessment. SKB TR-95-24. Stockholm, Sweden: 
Svensk Krnbrnslefrsrjning A.B. TIC: 223428. [DIRS 106449] 
Langmuir, D. 1997. Aqueous Environmental Geochemistry. Upper Saddle River, New Jersey: 
Prentice Hall. TIC: 237107. [DIRS 100051] 
Langmuir, D. 1997. "The Use of Laboratory Adsorption Data and Models to Predict 
Radionuclide Releases from a Geological Repository: A Brief History." Scientific Basis for 
Nuclear Waste Management XX, Symposium held December 2-6, 1996, Boston, Massachusetts. 
Gray, W.J. and Triay, I.R., eds. 465, 769-780. Pittsburgh, Pennsylvania: Materials Research 
Society. TIC: 238884. [DIRS 125369] 
Lewandowski, Z.; Stoodley, P.; and Altobelli, S. 1995. "Experimental and Conceptual Studies on 
Mass Transport in Biofilms." Water Science and Technology, 31, (1), 153-162. [London, 
England]: International Association on Water Quality. TIC: 242312. [DIRS 161664] 
Liang, L. and Morgan, J.J. 1990. "Chemical Aspects of Iron Oxide Coagulation in Water: 
Laboratory Studies and Implications for Natural Systems." Aquatic Sciences, 52, (1), 32-55. 
Basel, Switzerland: Birkhauser Verlag. TIC: 246125. [DIRS 109524] 
Lide, D.R., ed. 1995. CRC Handbook of Chemistry and Physics. 76th Edition. Boca Raton, 
Florida: CRC Press. TIC: 216194. TBV-5185 [DIRS 101876] 
Litaor, M.I. and Ibrahim, S.A. 1996. "Plutonium Association with Selected Solid Phases in Soils 
of Rocky Flats, Colorado, Using Sequential Extraction Technique." Journal of Environmental 
Quality, 25, (5), 1144-1151. Madison, Wisconsin: American Society of Agronomy. TIC: 252783. 
[DIRS: 161667] 
Liu, Q.; Zhang, Y.; and Laskowski, J.S. 2000. "The Adsorption of Polysaccharides Onto Mineral 
Surfaces: An Acid/Base Interaction." International Journal of Mineral Processing, 60, ([3-4]), 
229-245. [New York, New York]: Elsevier. TIC: 253706. [DIRS 161777] 
Lo, W.; Nelson, Y.M.; Lion, L.W.; Shuler, M.L.; and Ghiorse, W.C. 1996. "Determination of 
Iron Colloid Size Distribution in the Presence of Suspended Cells: Application to Iron 
Deposition Onto a Biofilm Surface." Water Research, 30, (10), 2413-2423. [New York, New 
York]: Elsevier. TIC: 253698. [DIRS 161669] 
Lu, N.; Conca, J.; Parker, G.R.; Leonard, P.A.; Moore, B.; Strietelmeier, B.; and Triay, I.R. 
2000. Adsorption of Actinides Onto Colloids as a Function of Time, Temperature, Ionic 
Strength, and Colloid Concentration, Waste Form Colloids Report for Yucca Mountain Program

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 142 June 2003 
(Colloid Data Summary from 1999 to 2000 Research). LA-UR-00-5121. Los Alamos, New 
Mexico: Los Alamos National Laboratory. TIC: 249708. TBV-5186 [DIRS 154422] 
Lu, N.; Triay, I.R.; Cotter, C.R.; Kitten, H.D.; and Bentley, J. 1998. Reversibility of Sorption of 
Plutonium-239 onto Colloids of Hematite, Goethite, Smectite, and Silica. LA-UR-98-3057. Los 
Alamos, New Mexico: Los Alamos National Laboratory. ACC: MOL.19981030.0202. 
TBV-5187 [DIRS 100946] 
Lytle, J.E. 1995. "Disposal of DOE-owned High Level Waste and Spent Nuclear Fuel." 
Memorandum from J.E. Lytle (DOE) to D.A. Dreyfus (DOE/OCRWM), October 26, 1995. 
ACC: HQO.19951116.0015. [DIRS 104398] 
Marty, R.C.; Bennett, D.; and Thullen, P. 1997. "Mechanism of Plutonium Transport in a 
Shallow Aquifer in Mortandad Canyon, Los Alamos National Laboratory, New Mexico." 
Environmental Science & Technology, 31, (7), 2020-2027. Washington, D.C.: American 
Chemical Society. TIC: 253960. [DIRS 161670] 
McCarthy, J.F. and Degueldre, C. 1993. "Sampling and Characterization of Colloids and 
Particles in Groundwater for Studying Their Role in Contaminant Transport." Environmental 
Particles. Buffle, J. and van Leeuwen, H.P., eds. Environmental Analytical and Physical 
Chemistry Series Volume 2. Pages 247-315. Boca Raton, Florida: Lewis Publishers. TIC: 
245905. [DIRS 108215] 
McCarthy, J.F. and Zachara, J.M. 1989. "Subsurface Transport of Contaminants." Environmental 
Science & Technology, 23, (5), 496-502. Easton, Pennsylvania: American Chemical Society. 
TIC: 224876. [DIRS 100778] 
McGraw, M.A. 1996. The Effect of Colloid Size, Colloid Hydrophobicity, and Volumetric Water 
Content on the Transport of Colloids Through Porous Media. Ph.D. dissertation. Berkeley, 
California: University of California. TIC: 245722. [DIRS 108218] 
Meijer, A. 1992. "A Strategy for the Derivation and Use of Sorption Coefficients in Performance 
Assessment Calculations for the Yucca Mountain Site." Proceedings of the DOE/Yucca 
Mountain Site Characterization Project Radionuclide Adsorption Workshop at Los Alamos 
National Laboratory, September 11-12, 1990. Canepa, J.A., ed. LA-12325-C. Pages 9-40. Los 
Alamos, New Mexico: Los Alamos National Laboratory. ACC: NNA.19920421.0117. [DIRS 
100467] 
Mertz, C.J.; Finch, R.J.; Fortner, J.A.; Jerden, J.L., Jr.; Yifen, T.; Cunnane, J.C.; and Finn, P.A. 
2003. Characterization of Colloids Generated from Commercial Spent Nuclear Fuel Corrosion. 
Activity Number: PAWTP30A. Argonne, Illinois: Argonne National Laboratory. ACC: 
MOL.20030422.0337. [DIRS 162032] 
Minai, Y.; Choppin, G.R.; and Sisson, D.H. 1992. "Humic Material in Well Water from the 
Nevada Test Site." Radiochimica Acta, 56, 195-199. Munchen, Germany: R. Oldenbourg Verlag. 
TIC: 238763. [DIRS 100801]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 143 June 2003 
Napper, D.H. 1983. "Basic Concepts of Colloid Stability." Polymeric Stabilization of Colloidal 
Dispersions. Pages 1-17. New York, New York: Academic Press. TIC: 253897. [DIRS 161735] 
NRC (U.S. Nuclear Regulatory Commission) 2002. Yucca Mountain Review Plan, Draft Report 
for Comment. NUREG-1804, Rev. 2. Washington, D.C.: U.S. Nuclear Regulatory Commission, 
Office of Nuclear Material Safety and Safeguards. TIC: 252488. [DIRS 158449] 
Payne, T.E.; Edis, R.; and Seo, T. 1992. "Radionuclide Transport by Groundwater Colloids at the 
Koongarra Uranium Deposit." Scientific Basis for Nuclear Waste Management XV, Symposium 
held November 4-7, 1991, Strasbourg, France. Sombret, C.G., ed. 257, 481-488. Pittsburgh, 
Pennsylvania: Materials Research Society. TIC: 204618. [DIRS 124812] 
Penrose, W.R.; Polzer, W.L.; Essington, E.H.; Nelson, D.M.; and Orlandini, K.A. 1990. 
"Mobility of Plutonium and Americium Through a Shallow Aquifer in a Semiarid Region." 
Environmental Science & Technology, 24, 228-234. Washington, D.C.: American Chemical 
Society. TIC: 224113. [DIRS 100811] 
Rittmann, B.E. and Wirtel, S.A. 1991. "Effect of Biofilm Accumulation on Colloid Cohesion." 
Journal of Environmental Engineering, 117, (5), 692-695. New York, New York: American 
Society of Civil Engineers. TIC: 253699. [DIRS 161671] 
Short, S.A.; Lowson, R.T.; and Ellis, J. 1988. "234U/238U and 230Th/234U Activity Ratios in 
the Colloidal Phases of Aquifers in Lateritic Weathered Zones." Geochimica et Cosmochimica 
Acta, 52, (11), 2555-2563. New York, New York: Pergamon Press. TIC: 239054. [DIRS 
113937] 
Sprouse, G. and Rittmann, B.E. 1990. "Colloid Removal in Fluidized-Bed Biofilm Reactor." 
Journal of Environmental Engineering, 116, (2), 314-329. New York, New York: American 
Society of Civil Engineers. TIC: 254391. [DIRS 161672] 
Stenhouse, M.J. 1995. Sorption Databases for Crystalline, Marl and Bentonite for Performance 
Assessment. NAGRA Technical Report 93-06. Wettingen, Switzerland: National Cooperative for 
the Disposal of Radioactive Waste. TIC: 247885. TBV-5188 [DIRS 147477] 
Tombacz, E.; Abraham, I.; Gilde, M.; and Szanto, F. 1990. "The pH-Dependent Colloidal 
Stability of Aqueous Montmorillonite Suspensions." Colloids and Surfaces, 49, 71-80. 
Amsterdam, The Netherlands: Elsevier. TIC: 246046. [DIRS 112690] 
van Olphen, H. 1977. An Introduction to Clay Colloid Chemistry for Clay Technologists, 
Geologists, and Soil Scientists. 2nd Edition. New York, New York: John Wiley & Sons. TIC: 
208918. [DIRS 114428] 
Vilks, P.; Cramer, J.J.; Bachinski, D.B.; Doern, D.C.; and Miller, H.G. 1993. "Studies of 
Colloids and Suspended Particles, Cigar Lake Uranium Deposit, Saskatchewan, Canada." 
Applied Geochemistry, 8, (6), 605-616. London, England: Pergamon Press. TIC: 237449. [DIRS 
108261]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 144 June 2003 
Walker, H.W. and Grant, S.B. 1996a. "Role of Polymer Flexibility in the Stabilization of 
Colloidal Particles by Model Anionic Polyelectrolytes." Journal of Colloid and Interface 
Science, 179, ([2]), 552-560. [New York, New York]: Academic Press. TIC: 253705. [DIRS 
161736] 
Walker, H.W. and Grant, S.B. 1996b. "Coagulation and Stabilization of Colloidal Particles by 
Adsorbed DNA Block Copolymers: The Role of Polymer Confirmation." Langmuir, 12, (13), 
3151-3156. [Washington, D.C.]: American Chemical Society. TIC: 253704. [DIRS: 161738] 
Wan, J. and Tokunaga, T.K. 1997. "Film Straining on Colloids in Unsaturated Porous Media: 
Conceptual Model and Experimental Testing." Environmental Science & Technology, 31, (8), 
2413-2420. [Washington, D.C.: American Chemical Society]. TIC: 234804. [DIRS 108285] 
Wan, J. and Wilson, J.L. 1994. "Colloid Transport in Unsaturated Porous Media." Water 
Resources Research, 30, (4), 857-864. Washington, D.C.: American Geophysical Union. TIC: 
222359. [DIRS 114430] 
Wanner, O.; Cunningham, A.B.; and Lundman, R. 1995. "Modeling Biofilm Accumulation and 
Mass Transport in a Porous Medium Under High Substrate Loading." Biotechnology and 
Bioengineering, 47, (6), 703-712. [New York, New York]: John Wiley & Sons. TIC: 253701. 
[DIRS 161674] 
Weiss, T.H.; Mills, A.L.; Hornberger, G.M.; and Herman, J.S. 1995. "Effect of Bacterial Cell 
Shape on Transport of Bacteria in Porous Media." Environmental Science & Technology, 29, (7), 
1737-1740. [Washington, D.C.]: American Chemical Society. TIC: 247490. [DIRS 147345] 
Wilkinson, K.J.; Joz-Roland, A.; and Buffle, J. 1997. "Different Roles of Pedogenic Fulvic Acids 
and Aquagenic Biopolymers on Colloid Aggregation and Stability in Freshwaters." Limnilogy 
and Oceanography, 42, (8), 1714-1724. Waco, Texas: American Society of Limnology and 
Oceanography. TIC: 253707. [DIRS 161734] 
Wilkinson, K.J.; Ngre, J.-C.; and Buffle, J. 1997. "Coagulation of Colloidal Material in Surface 
Waters: The Role of Natural Organic Matter." Journal of Contaminant Hydrology, 26, ([1-4]), 
229-243. [New York, New York]: Elsevier. TIC: 253708. [DIRS 161732] 
Williams, N.H. 2003. "Thermal Inputs for Evaluations Supporting TSPA-LA, Supplement." 
Interoffice memorandum from N.H. Williams (BSC) to Distribution, April 4, 2003, 0205035938, 
with enclosures. ACC: MOL.20030501.0081. [DIRS 162731] 
Wronkiewicz, D.J.; Buck, E.C.; and Bates, J.K. 1997. "Grain Boundary Corrosion and Alteration 
Phase Formation During the Oxidative Dissolution of UO2 Pellets." Scientific Basis for Nuclear 
Waste Management XX, Symposium held December 2-6, 1996, Boston, Massachusetts. Gray, 
W.J. and Triay, I.R., eds. 465, 519-526. Pittsburgh, Pennsylvania: Materials Research Society. 
TIC: 238884. [DIRS 102048]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 145 June 2003 
Yates, M.V. and Yates, S.R. 1988. "Modeling Microbial Fate in the Subsurface Environment." 
Critical Reviews in Environmental Control, 17, (4), 307-344. Boca Raton, Florida: CRC Press. 
TIC: 247762. [DIRS 147348] 
Yokoyama, A.; Srinivasan, K.R.; and Fogler, H.S. 1990. "Stabilization of Colloidal Particles by 
Acidic Polysaccharides. Effect of Temperature on Stability." Langmuir, 6, (3), 702-706. 
Washington, D.C.: American Chemical Society. TIC: 253703. [DIRS 161675] 
Znker, H.; Richter, W.; Brendler, V.; and Nitsche, H. 2000. "Colloid-Borne Uranium and Other 
Heavy Metals in the Water of a Mine Drainage Gallery." Radiochimica Acta, 88, ([9/11]), 619- 
624. Mnchen, Germany: R. Oldenbourg Verlag. TIC: 253959. [DIRS 162746] 
Zumstein, J. and Buffle, J. 1989. "Circulation of Pedogenic and Aquagenic Organic Matter in an 
Eutrophic Lake." Water Research, 23, (2), 229-239. New York, New York: Pergamon Press. 
TIC: 253878. [DIRS 161740] 
9.2 CODES, STANDARDS, REGULATIONS, AND PROCEDURES 
10 CFR 63. 2002. Energy: Disposal of High-Level Radioactive Wastes in a Geologic Repository 
at Yucca Mountain, Nevada. Readily available. [DIRS 158535] 
40 CFR 197. 2001. Protection of Environment: Public Health and Environmental Radiation 
Protection Standards for Yucca Mountain, Nevada. Readily available. [DIRS 155238] 
AP-2.22Q, Rev 0, ICN 1. Classification Criteria and Maintenance of the Monitored Geologic 
Repository Q-List. Washington, D.C.: U.S. Department of Energy, Office of Civilian 
Radioactive Waste Management. ACC: DOC.20030422.0009 
AP-SI.1Q, Rev 5. Software Management. Washington, D.C.: U.S. Department of Energy, Office 
of Civilian Radioactive Waste Management. ACC: DOC.20030422.0012 
AP-SIII.10Q, Rev. 1. Models. Washington D.C., Washington D.C.: Office of Civilian 
Radioactive Waste Management. ACC: DOC.20030312.0039. 
ASTM C 1174-97. 1998. Standard Practice for Prediction of the Long-Term Behavior of 
Materials, Including Waste Forms, Used in Engineered Barrier Systems (EBS) for Geological 
Disposal of High-Level Radioactive Waste. West Conshohocken, Pennsylvania: American 
Society for Testing and Materials. TIC: 246015. [DIRS 105725] 
9.3 SOURCE DATA 
LA0002SK831352.001. Total Colloidal Particles Concentration and Size Distribution in 
Groundwaters from the Nye County Early Warning Drilling Program. Submittal date: 
02/24/2000. [DIRS 149232] 
LA0002SK831352.002. Total Colloidal Particles Concentration and Size Distribution in 
Groundwaters Around Yucca Mountain. Submittal date: 02/25/2000. [DIRS 149194]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 146 June 2003 
LA0002SK831352.003. Colloid Size Distribution and Total Colloid Concentration in Ineel 
Groundwater Samples. Submittal date: 02/25/2000. [DIRS 161771] 
LA0002SK831352.004. Colloid Size Distribution and Total Colloid Concentration in 
Groundwater's from the Nuclear Test Site. Submittal date: 02/25/2000. [DIRS 161579] 
LA0003NL831352.002. The KD Values of 239Pu on Colloids of Hematite, Ca-Montmorillonite 
and Silica in Natural and Synthetic Groundwater. Submittal date: 03/29/2000. [DIRS 148526] 
LA0005NL831352.001. The Kd Values of 243Am on Colloids of Hematite, Montmorillonite and 
Silica in Natural and Synthetic Groundwater. Submittal date: 05/03/2000. [DIRS 149623] 
LA0211SK831352.001. Colloid Concentration and Size Distribution from Crater Flats Wells. 
Submittal date: 12/04/2002. [DIRS 161580] 
LA0211SK831352.002. Colloid Concentration and Size Distribution from Nye County Early 
Warning Drilling Program, Alluvial Testing Complex (ATC) Wells. Submittal date: 12/04/2002. 
[DIRS 161581] 
LA0211SK831352.003. Colloid Concentration and Size Distribution from Nellis/Desert Rsearch 
Institute (DRI) Wells. Submittal date: 12/04/2002. [DIRS 161582] 
LA0211SK831352.004. Colloid Concentration and Size Distribution from Nye County Early 
Warning Drilling Program, Fall 2000 Field Sampling. Submittal date: 12/04/2002. [DIRS 
161458] 
LA0304PR831232.001. Calculation of Ionic Strengths Based on Cation Concentrations in 
Various Groundwater Samples in which Colloid Concentrations were Measured. Submittal date: 
05/13/2003. [DIRS 163196] 
LA0304PR831232.002. Calculation of Ionic Strengths Based on Non-Q Cation Concentrations 
in Various Groundwater Samples in Which Colloid Concentrations were Measured. Submittal 
date: 05/13/2003. [DIRS 163197] 
LA9910SK831341.005. Total Colloidal Particles Concentration and Size Distribution in NTSER-
20-5-1, NTS-ER-20-5-3, and J-13 Groundwater. Submittal date: 12/07/1999. [DIRS 144991] 
LL000905312241.018. Data Associated with the Detection and Measurement of Colloids 
Recorded in Scientific Notebook 1644. Submittal date: 09/29/2000. [DIRS 152621] 
LL991109751021.094. Data Associated with the Detection and Measurement of Colloids in 
Scientific Notebook SN 1644. Submittal date: 01/10/2000. [DIRS 142910] 
MO0212UCC034JC.002. Mass Transport of Solids in Effluent Solution During Miniature Waste 
Package Corrosion. Submittal date: 12/09/2002. [DIRS 161457] 
MO0301ANLGNN01.527. Glass Unsaturated (Drip) Test Results (BSC Test Plan: SITP-02-WF- 
002): Boron Release. Submittal date: 01/15/2003. [DIRS 161914]

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 147 June 2003 
MO0301ANLGNN02.527. Glass Unsaturated (Drip) Test Results (BSC Test Plan: SITP-02-WF- 
002): TC, NP, PU, and AM Releases. Submittal date: 01/15/2003. [DIRS 161916] 
MO0302UCC034JC.003. Graphical X-Ray Diffractometer Data and Mineral Analysis of Filtered 
Solids from Effluent Solution During Miniature Waste Package Corrosion. Submittal date: 
2/10/2003. [DIRS 162871] 
MO0306ANLSf001.459. Colloids Generated from Irradiated N Reactor Fuel, Data Report. 
Submittal date: 06/04/2003. [DIRS 163910] 
SNT05080598002.001. Engineered Barrier System (EBS) Transport Sorption and Colloid 
Parameters for the TSPA-VA (Total System Performance Assessment-Viability Assessment) Rip 
Calculations. Submittal date: 11/06/1998. [DIRS 162744] 
9.4 OUTPUT DTNs 
SN0304T0504103.001. Groundwater Colloid Concentration Parameters for TSPA. Submittal 
date: 04/01/2003. 
SN0304T0504103.002. Partition Coefficients (Kd Values) for Selected Radionuclides Modeled 
in TSPA. Submittal date: 04/01/03. 
SN0304T0504103.003. Iron Oxyhydroxide Colloid Concentration Parameters and Specific 
Surface Area (SA) for Iron Oxyhydroxide Colloids. Submittal date: 04/01/03. 
SN0304T0504103.004. Concentration of Embedded Radionuclides (Pu and Am) in Waste Form 
Colloids, Mass Concentrations of Waste Form Colloids. Submittal date: 04/01/03.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 I-1 of I-6 June 2003 
ATTACHMENT ICALCULATION OF GROUNDWATER COLLOID PARAMETERS

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 I-2 of I-6 June 2003 
CALCULATION OF GROUNDWATER COLLOID PARAMETERS 
The groundwater colloid parameters for use in the TSPA-LA model were based on a dataset that 
included 79 groundwater samples collected in the vicinity of Yucca Mountain and 11 samples 
collected from the Idaho National Engineering and Environmental Laboratory (Table I-1). 
Inclusion of the Idaho National Engineering and Environmental Laboratory groundwater colloid 
data (DTN: LA0002SK831352.003) was deemed appropriate for inclusion in the data analysis 
among the groundwater data from the Yucca Mountain area because the climate in Idaho Falls is 
also arid and the bedrock geology is also volcanic in nature (fractured basalts). 
Conversion of colloid populations (pt/mL) in the groundwater samples to mass concentrations 
(mg/L) involved only simple mathematical manipulations (addition, multiplication, and division) 
and could readily have been executed with the use of a hand-held calculator. However, the 
calculations were handled with the aid of Microsoft Excel 2000. Excel was also used for 
tabular presentation of the groundwater data in Table I-1 and to graph the cumulative distribution 
function of the data (see Figure 12, Section 6.3.2.5). 
Conversion of the Colloid Populations to Mass Concentrations: 
The conversion of the colloid population to mass concentration required the establishment of two 
basic assumptions (see Section 5, Assumption 5.10): 
1. All colloid particles were assumed to be spherical colloids. The assumption that all 
colloid particles are spherical enables the calculation of volume for each colloid. This 
assumption is ultimately conservative in that it results in larger masses than the use of 
other configurations such as sheet-shaped or rod-shaped, etc., particles of a given 
diameter size. 
2. A colloid mineral density of 2.5 g/cm3 (2.5E-18 mg/nm3) was assumed to be appropriate 
for all colloid particles. This assumption was founded on the copious scientific 
measurements of particle density on a large range of minerals, including silicate layerlattice 
clays. Silicate minerals have shown to have a particle density of ranging from 
2.27 to 2.33 g/cm3 at the low range, cristobalite and tridymite respectively, and 2.67 
g/cm3 at the high range (pure quartz) (Lide 1995 [DIRS 101876], pp. 4-132 through 
4-138). 
The volume of a sphere (V) can be calculated from the radius (R) by the following relationship: 
V = 4/3 p R3 (Eq. I-1) 
The colloid population data for each groundwater sample consisted of population data recorded 
at 10 nm increments from the particle-size diameter range 50 nm to 200 nm as reported in the 
DTNs. The midpoint of the particle diameter size class ranges that are reported in the 
groundwater datasheets was used to establish the radius for the particle volume calculations 
using Equation I-1. For example, those particles with diameter ranging from 50 to 60 nm were 
assigned a size 55 nm. Thus, the radius (R), for this particle diameter size population was 27.5 
nm.

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 I-3 of I-6 June 2003 
After calculating an estimate of volume for each particle diameter size class interval, the mass 
concentration (mg/L) for each particle size interval was calculated by multiplying particle 
volume (nm3) by particle density (mg nm-3)this product was then multiplied by the total 
number of particles in the size class interval to derive an estimate of the total colloid mass in 
each particle-size class interval. The total colloid mass in the water sample (Column 4 in 
Table I-1) was then estimated by summing the mass concentrations in each particle-size class 
interval. For example, the total colloid concentration for the groundwater sample extracted from 
Well NC-EWDP-01s was calculated as outlined in Table I-2. 
Table I-1. Groundwater Samples Used to Develop Cumulative Distribution Function Developed to 
Establish Colloid Concentration Sampling Frequency in GoldSim Calculations for TSPA-LA for 
Solutions with Ionic Strength Less Than 0.05 
Groundwater 
Sample Well ID Colloid Population 
(pt/mL) 
Colloid 
Concentration 
(mg/L) 
Data Source DTN LA0002SK831352.001 [DIRS 149232] Alluvium (Direct Input) 
1 NC-EWDP-01s, Depth 170 1.07E+07 3.02E-02 
2 NC-EWDP-01s, Depth 250 2.08E+07 4.62E-02 
3 NC-EWDP-03s, Depth 449 3.56E+08 3.48E-01 
4 NC-EWDP-03s, Depth 390 1.78E+09 1.90E+00 
5 NC-EWDP-09SX, Depth 310 3.85E+07 4.49E-02 
6 NC-EWDP-09SX, Depth 270 7.24E+07 8.74E-02 
7 NC-EWDP-09SX, Depth 150 9.73E+07 1.62E-01 
8 NC-EWDP-09SX, Depth 112 7.14E+07 8.89E-02 
9 Nc airport 7.95E+07 1.41E-01 
Data Source DTN LA0002SK831352.002 [DIRS 149194] Volcanics (Direct Input) 
10 UE-25 J-13 1.19E+06* 1.35E-03 
11 UE-25 J-13 1.046E+06* 1.75E-03 
12 USW SD-6 5.07E+08* 7.24E-01 
13 USW SD-6 1.05E+08* 1.43E-01 
14 UE-25 WT #17 2.11E+09* 3.49E+00 
15 UE-25 WT #17 1.475E+09* 2.32E+00 
16 UE-25 WT #17 2.633E+07* 2.69E-02 
17 UE-25 WT #17 8.236E+07* 1.32E-01 
18 UE-25 WT #3 7.78E+06* 2.02E-02 
19 UE-18 WW #8 2.93E+06* 2.79E-03 
20 UE-18 WW #8 3.31E+06* 3.70E-03 
21 U-20 WW #20 5.16E+07* 5.83E-02 
22 U-20 WW #20 5.72E+07* 7.71E-02 
23 UE-29 a #1 7.45E+06* 1.44E-02 
24 UE-29 a #2 3.66E+07* 6.73E-02 
25 UE-25 c #1 4.63E+06* 9.68E-03 
26 UE-25 c #1 2.82E+06* 4.49E-03 
Data Source DTN LA9910SK831341.005 [DIRS 144991] Volcanics (Direct Input) 
27 NTS-ER-20-5-3 1.43E+10 1.02E+01 
28 NTS-ER-20-5-1 1.25E+10 6.74E+00 
29 UE-25 J-13 1.54E+06 3.72E-03

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 I-4 of I-6 June 2003 
Table I-1. Groundwater Samples Used to Develop Cumulative Distribution Function Developed to 
Establish Colloid Concentration Sampling Frequency in GoldSim Calculations for 
TSPA-LA for Solutions with Ionic Strength Less Than 0.05 (Continued) 
Groundwater 
Sample Well ID Colloid Population 
(pt/mL) 
Colloid 
Concentration 
(mg/L) 
Data Source DTN LA0211SK831352.004 [DIRS 161458] Nye Co. Phase 2  Alluvium (Direct Input) 
30 NC=EWDP-15P 1.34E+08 1.73E-01 
31 NC-EWDP-7S 3.02E+06 9.01E-03 
32 NC-EWDP-4PB 1.41E+09 2.03E+00 
33 NC-EWDP-4PA 2.34E+08 3.05E-01 
34 NC-EWDP-5SB 9.38E+08 2.69E+00 
35 NC-EWDP-12PA 7.52E+07 1.42E-01 
36 NC-EWDP-12PB 8.54E+07 1.53E-01 
37 NC-EWDP-12PC 2.11E+07 6.29E-02 
38 NC-EWDP-19D 8.27E+07 7.73E-02 
Data Source DTN LA0211SK831352.002 [DIRS 161581] ATC Wells (Direct Input) 
39 ATC-IM1-A 1.01E+10 7.39E+00 
40 ATC-IM1-B 9.51E+09 7.20E+00 
41 NC-EWDP-19IM-2-A 1.71E+10 1.35E+01 
42 NC-EWDP-19IM-2-B 1.76E+10 1.46E+01 
43 NC-EWDP-19IM1-Z1 6.40E+09 5.61E+00 
44 NC-EWDP-19IM1-Z2 3.23E+09 2.70E+00 
45 NC-EWDP-19IM1-Z3 7.73E+09 5.67E+00 
46 NC-EWDP-19IM1-Z4 8.52E+09 6.40E+00 
47 NC-EWDP-19IM1-Z5 2.33E+10 1.93E+01 
48 NC-EWDP-19D-Z5 1.27E+10 1.08E+01 
49 ATC-19D1-011602-1350C 1.01E+10 6.57E+00 
50 ATC-19D1-011702-1215C 9.28E+09 5.64E+00 
51 ATC-19D1-011602-011702 7.33E+10 4.84E+01 
52 ATC-19D1-012802-1500 5.19E+10 3.15E+01 
53 NC-EWDP-19D, Z1 5.13E+09 4.12E+00 
54 NC-EWDP-19D-Z1 8.27E+07 7.74E-02 
55 NC-EWDP-19D, Z2 8.73E+07 9.75E-02 
56 NC-EWDP-19D, Z2 2.29E+08 2.47E-01 
57 NC-EWDP-19D, Z2 2.24E+08 2.24E-01 
58 NC-EWDP-19D 9.34E+08 7.47E-01 
59 NC-EWDP-19D 2.77E+08 2.52E-01 
60 NC-EWDP-19D 3.51E+09 1.87E+00 
Data Source DTN LA0211SK831352.001 USGS wells at Crater Flat (Direct Input) 
61 USGS-VH-1 1.33E+07 2.45E-02 
62 USGS-VH-2 1.18E+06 5.03E-03 
63 USGS-VH-1-A 2.17E+07 2.07E-02 
64 USGS-VH-1-B 1.09E+07 1.34E-02 
Data Source DTN LA0211SK831352.003 (Direct Input) 
65 DRI-EH-2-091200-0800 2.17E+06 4.36E-03 
66 DRI-BLM-091200-0915 3.24E+07 3.93E-02 
67 DRI-TTR3B-091200-1430 4.25E+06 6.77E-03

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 I-5 of I-6 June 2003 
Table I-1. Groundwater Samples Used to Develop Cumulative Distribution Function Developed to 
Establish Colloid Concentration Sampling Frequency in GoldSim Calculations for 
TSPA-LA for Solutions with Ionic Strength Less Than 0.05 (Continued) 
Groundwater 
Sample Well ID Colloid Population 
(pt/mL) 
Colloid 
Concentration 
(mg/L) 
68 DRI-Cedar Pass-091200-1325 1.01E+06 2.67E-03 
69 DRI-EH-7-091200-1040 8.58E+05 1.89E-03 
70 DRI-Sandia 7-091300-1030 1.05E+07 1.70E-02 
71 DRI-Sandia 6-091300-0930 6.29E+07 8.29E-02 
72 DRI-Tolicha Peak-091400-0745 6.98E+06 7.62E-03 
73 DRI-Airforce 3A-091300-1500 1.34E+09 1.58E+00 
74 DRI-Roller Coaster-091300-0930 1.12E+06 4.48E-03 
Data Source DTN: LA0002SK831352.003 [DIRS 161771] INEEL Wells (Corroborating Data) 
75 USGS 117-1 4.23E+06 8.97E-03 
76 M7S-1 1.30E+06 2.35E-03 
77 USGS 120-1 3.76E+06 5.80E-03 
78 USGS 119-1 8.13E+06 1.48E-02 
79 M3S-1 1.24E+06 1.97E-03 
80 M1S-1 3.28E+06 5.42E-03 
81 USGS-87-1 2.63E+06 4.63E-03 
82 M10S-1 9.37E+07 1.71E-01 
83 BLR-99-1 7.73E+07 1.38E-01 
84 M14S-1 4.28E+06 8.21E-03 
85 USGS 92-1 8.00E+10 1.72E+02 
Data Source DTN: LA0002SK831352.004 [DIRS 161579] NTS Wells (Corroborating Data) 
86 NTS-ER-20-5-1 1.25E+10 6.74E+00 
87 NTS-ER-20-5-3 1.43E+10 1.02E+01 
88 NTS-U20n, ~2511 ft 2.57E+08 3.20E-01 
89 NTS-U20n, lower zone 5.19E+09 5.47E+00 
90 NTS-U19q 2.72E+10 3.51E+01

Waste Form and In-Drift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary 
MDL-EBS-PA-000004 REV 00 I-6 of I-6 June 2003 
Table I-2. Example Calculation for Total Colloid Mass in Well NC-EWDP-01s, Depth 170 
Particle Diameter Size 
Range (nm) 
Particle Diameter (nm) Colloid Number 
(pt/mL) 
Calculated Colloid 
Mass (mg/L) 
50-60 55 9.27E+05 2.0189E-04 
60-70 65 1.01E+06 3.6308E-04 
70-80 75 8.64E+05 4.7713E-04 
80-90 85 8.01E+05 6.4392E-04 
90-100 95 8.51E+05 9.5508E-04 
100-110 105 1.14E+06 1.7275E-03 
110-120 115 8.01E+05 1.5947E-03 
120-130 125 7.26E+05 1.8561E-03 
130-140 135 5.26E+05 1.6941E-03 
140-150 145 6.26E+05 2.4981E-03 
150-160 155 5.76E+05 2.8077E-03 
160-170 165 4.51E+05 2.6520E-03 
170-180 175 4.13E+05 2.8974E-03 
180-190 185 3.13E+05 2.5942E-03 
190-200 195 3.63E+05 3.5233E-03 
200 200 3.51E+05 3.6757E-03 
Totals 1.07E+07 3.02E-02 
Source: DTN: LA0002SK831352.001 [DIRS 149232]. 
Establishment of Groundwater Colloid Parameters for Use in the TSPA-LA Model: 
Mass concentrations (mg/L) of the groundwater in Table I-1 were pooled and a discrete 
cumulative distribution function was established to evaluate the uncertainty in colloid 
concentration distribution (see Figure 12, Section 6.3.2.5). Water samples that had been filtered 
were not considered in the development of the cumulative distribution function. Since the 
colloid particles were measured by dynamic light scattering techniques, any potential error in 
measurement of colloid populations for the various particle size classes due to filter ripening 
(i.e., clogging of filter pores through time during the filtration process) was avoided by using 
only non-filtered sample data. 
The data shown in Figure 12, Section 6.3.2.5 reflect observed variability in groundwater colloid 
concentrations. The goal of the uncertainty distribution for groundwater colloid concentrations 
is to numerically capture our knowledge about uncertainty on a large scale. Based on the 
groundwater colloid concentration collected at the two sites (Yucca Mountain and Idaho 
National Engineering and Environmental Laboratory) and the tremendous uncertainty associated 
with the collection of groundwater colloids, a reasonable representation of the uncertainty is 
shown in the cumulative distribution function. Major factors that contribute to uncertainty in the 
concentrations of colloids in the groundwater samples include (1) collection techniques, 
(2) differences in pumping rates at each well, and (3) unknowns factors including the types of 
additives introduced in the wells during the drilling process itself.