EBS FEPs/Degradation Modes Abstraction Rev 00, ICN 01

ANL-WIS-PA-000002

September 2000

1. PURPOSE 
Under the provisions of the U.S. Department of Energys (DOEs) Revised Interim Guidance 
Pending Issuance of New U. S. Nuclear Regulatory Commission (NRC) Regulations (Revision 
01, July 22, 1999,) for Yucca Mountain, Nevada (Dyer 1999; and herein referred to as DOEs 
interim guidance), the DOE must provide a reasonable assurance that the regulatory-specified 
performance objectives for the Yucca Mountain project can be achieved for a 10,000-year postclosure 
period. This assurance must be demonstrated in the form of a performance assessment 
that: (1) identifies the features, events, and processes (FEPs) that might affect the performance of 
the geologic repository; (2) examines the effects of such FEPs on the performance of the geologic 
repository; (3) estimates the expected annual dose to a specified nearby population group. The 
performance assessment must also provide the technical basis for inclusion or exclusion of 
specific FEPs. 
Although the NRC has not defined or used the term "scenario" in the pertinent regulations, the 
Yucca Mountain Total System Performance Assessment (TSPA) has chosen to satisfy the abovestated 
performance assessment requirements by adopting a scenario development process. This 
decision was made based on the Yucca Mountain TSPA adopting a definition of "scenario" as not 
being limited to a single, deterministic future of the system, but rather as a set of similar futures 
that share common FEPs. The DOE has chosen to adopt a scenario development process based on 
the methodology developed by Cranwell et al. (1990) for the NRC. The first step of this process 
is the identification of FEPs potentially relevant to the performance of the Yucca Mountain 
repository; the second step includes the screening of each FEP. 
The primary purpose of this Analysis/Model Report (AMR) is to identify and document the 
analysis, screening decision, and Total System Performance Assessment (TSPA) disposition or 
screening argument for each of the 86 FEPs that have been identified as Engineering Barrier 
System (EBS) FEPs (described in Section 1.1). The screening decisions, and associated TSPA 
disposition or screening argument, for the subject FEPs will be catalogued separately in a projectspecific 
FEPs database (see Section 1.4). This AMR and the database are being used to document 
information related to the FEPs screening decisions and associated screening argument and to 
assist reviewers during the license review process. 
1.1 SCOPE 
This AMR has been prepared to satisfy the FEP screening documentation requirements in the Work 
Scope/Objectives/Tasks section of the development plan entitled EBS FEPs/Degradation Modes 
Abstraction (CRWMS M&O 1999a). 
On January 26, 2000, a design change was initiated to resolve certain thermal design issues. This 
design change will result in a greater ability of the waste packages to reject heat after closure of 
the repository, thereby maintaining the two thermal requirements. The first requirement is

ANL-WIS-PA-000002 REV 00 ICN 01 10 September 2000 
protective of the fuel cladding, and the second requires that a section of the rock pillar between 
drifts remain below the boiling temperature of water, providing a path for water drainage. This 
design change is described in the Monitored Geologic Repository Project Description Document 
(CRWMS M&O 2000ii). This AMR originally considered a design with backfill, and is now 
being updated (REV 00 ICN1) to address the design without backfill. 
The current FEPs list consists of 1786 entries (as described in Section 1.2). The FEPs have been 
classified as Primary and Secondary FEPs (as described in Section 1.2) and have been assigned to 
various Process Modeling Reports (PMRs). The assignments were based on the nature of the 
FEPs so that the analysis and resolution for screening decisions reside with the subject-matter 
experts in the relevant disciplines. The resolution of other than EBS FEPs is documented in 
AMRs prepared by the responsible PMR groups. Several relevant FEPs do not fit neatly into the 
existing PMR structure. Criticality is the largest example, and is treated in FEP assignments as if 
it were a separate PMR. Some FEPs were best assigned to the TSPA itself (i.e., system-level 
FEPs), rather than to its component models. 
This AMR addresses the 86 Primary FEPs that have been identified as EBS FEPs. These FEPs 
represent the key features of the EBS, processes that result in degradation of these features, and 
processes that occur within the EBS that influence other aspects of the repository. The 86 Primary 
EBS FEPs addressed in this AMR are provided in Table 1 
Table 1. Primary EBS FEPs 
FEP Name - YMP FEP # 
Excavation/Construction  YMP 1.1.02.00.00 
Site Flooding (During Construction and Operation)  YMP 1.1.02.01.00 
Effects of Preclosure Ventilation  YMP 1.1.02.02.00 
Undesirable Materials Left  YMP 1.1.02.03.00 
Error in Waste or Backfill Emplacement  YMP 1.1.03.01.00 
Repository Design  YMP 1.1.07.00.00 
Quality Control  YMP 1.1.08.00.00 
Accidents and Unplanned Events During Operation  YMP 1.1.12.01.00 
Retrievability  YMP 1.1.13.00.00 
Igneous Intrusion into Repository  YMP 1.2.04.03.00 
Corrosion of Waste Containers  YMP 2.1.03.01.00 
Container Healing  YMP 2.1.03.10.00 
Container Failure (Long-term)  YMP 2.1.03.12.00 
Preferential Pathways in the Backfill  YMP 2.1.04.01.00 
Physical and Chemical Properties of Backfill  YMP 2.1.04.02.00 
Erosion or Dissolution of Backfill  YMP 2.1.04.03.00 
Mechanical Effects of Backfill  YMP 2.1.04.04.00

ANL-WIS-PA-000002 REV 00 ICN 01 11 September 2000 
Table 1. Primary EBS FEPs - Continued 
FEP Name - YMP FEP # 
Backfill Evolution - YMP 2.1.04.05.00 
Properties of Bentonite  YMP 2.1.04.06.00 
Buffer Characteristics  YMP 2.1.04.07.00 
Diffusion in Backfill  YMP 2.1.04.08.00 
Radionuclide Transport Through Backfill  YMP 2.1.04.09.00 
Degradation of Cementitious Materials in Drift  YMP 2.1.06.01.00 
Effects of Rock Reinforcement Materials  YMP 2.1.06.02.00 
Degradation of the Liner  YMP 2.1.06.03.00 
Flow Through the Liner  YMP 2.1.06.04.00 
Degradation of Invert and Pedestal  YMP 2.1.06.05.00 
Effects and Degradation of Drip Shield  YMP 2.1.06.06.00 
Effects at Material Interfaces  YMP 2.1.06.07.00 
Rockfall (Large Block)  YMP 2.1.07.01.00 
Mechanical Degradation or Collapse of Drift  YMP 2.1.07.02.00 
Movement of Containers  YMP 2.1.07.03.00 
Hydrostatic Pressure on Container  YMP 2.1.07.04.00 
Creeping of Metallic Materials in the EBS  YMP 2.1.07.05.00 
Floor Buckling  YMP 2.1.07.06.00 
Increased Unsaturated Water Flux at the Repository  YMP 2.1.08.01.00 
Enhanced Influx (Philip's Drip)  YMP 2.1.08.02.00 
Condensation Forms on Backs of Drifts  YMP 2.1.08.04.00 
Flow Through Invert  YMP 2.1.08.05.00 
Wicking in Waste and EBS  YMP 2.1.08.06.00 
Pathways for Unsaturated Flow and Transport in the Waste and EBS  YMP 2.1.08.07.00 
Induced Hydrological Changes in the Waste and EBS  YMP 2.1.08.08.00 
Saturated Groundwater Flow in Waste and EBS  YMP 2.1.08.09.00 
Resaturation of Repository  YMP 2.1.08.11.00 
Properties of the Potential Carrier Plume in the Waste and EBS  YMP 2.1.09.01.00 
Interaction with Corrosion Products  YMP 2.1.09.02.00 
In-drift Sorption  YMP 2.1.09.05.00 
Reduction-oxidation Potential in Waste and EBS  YMP 2.1.09.06.00 
Reaction Kinetics in Waste and EBS  YMP 2.1.09.07.00 
Chemical Gradients/Enhanced Diffusion in Waste and EBS  YMP 2.1.09.08.00 
Waste-Rock Contact  YMP 2.1.09.11.00 
Rind (Altered Zone) Formation in Waste, EBS, and Adjacent Rock  YMP 2.1.09.12.00 
Complexation by Organics in Waste and EBS  YMP 2.1.09.13.00 
Colloid Formation in Waste and EBS  YMP 2.1.09.14.00

ANL-WIS-PA-000002 REV 00 ICN 01 12 September 2000 
Table 1. Primary EBS FEPs - Continued 
FEP Name - YMP FEP # 
Formation of True Colloids in Waste and EBS  YMP 2.1.09.15.00 
Formation of Pseudo-colloids (Natural) in Waste and EBS  YMP 2.1.09.16.00 
Formation of Pseudo-colloids (Corrosion Products) in Waste and EBS  YMP 2.1.09.17.00 
Microbial Colloid Transport in the Waste and EBS  YMP 2.1.09.18.00 
Colloid Transport and Sorption in the Waste and EBS  YMP 2.1.09.19.00 
Colloid Filtration in the Waste and EBS  YMP 2.1.09.20.00 
Suspensions of Particles Larger than Colloids  YMP 2.1.09.21.00 
Biological Activity in Waste and EBS  YMP 2.1.10.01.00 
Heat Output / Temperature in Waste and EBS  YMP 2.1.11.01.00 
Exothermic Reactions in Waste and EBS  YMP 2.1.11.03.00 
Temperature Effects / Coupled Processes in Waste and EBS  YMP 2.1.11.04.00 
Differing Thermal Expansion of Repository Components  YMP 2.1.11.05.00 
Thermally-induced Stress Changes in Waste and EBS  YMP 2.1.11.07.00 
Thermal Effects: Chemical and Microbiological Changes in the Waste and EBS  YMP 2.1.11.08.00 
Thermal Effects on Liquid or Two-phase Fluid Flow in the Waste and EBS  YMP 2.1.11.09.00 
Thermal Effects on Diffusion (Soret effect) in Waste and EBS  YMP 2.1.11.10.00 
Gas Generation  YMP 2.1.12.01.00 
Gas Generation (He) from Fuel Decay  YMP 2.1.12.02.00 
Gas Generation (H2) from Metal Corrosion  YMP 2.1.12.03.00 
Gas Generation (CO2, CH4, H2S) from Microbial Degradation  YMP 2.1.12.04.00 
Gas Generation from Concrete  YMP 2.1.12.05.00 
Gas Transport in Waste and EBS  YMP 2.1.12.06.00 
Radioactive Gases in Waste and EBS  YMP 2.1.12.07.00 
Gas Explosions  YMP 2.1.12.08.00 
Radiolysis  YMP 2.1.13.01.00 
Radiation Damage in Waste and EBS  YMP 2.1.13.02.00 
Mutation  YMP 2.1.13.03.00 
Episodic / Pulse Release from Repository  YMP 2.2.07.06.00 
Redissolution of Precipitates Directs More Corrosive Fluids to Containers  YMP 2.2.08.04.00 
Gas Pressure Effects  YMP 2.2.11.02.00 
Drainage With Transport and Sealing  YMP 2.1.08.12 * 
Drains  YMP 2.1.08.13 * 
* These FEPs were added to the YMP database since REV 00 ICN01 of this document. 
A separate, independent evaluation of EBS FEPs was performed by the EBS process modeling 
organization (EBSO) at the Yucca Mountain Project (CRWMS M&O 2000c). The resulting

ANL-WIS-PA-000002 REV 00 ICN 01 13 September 2000 
AMR identified 37 FEPs (including 5 common mode events) relevant to the EBS. These FEPs are 
listed in table 2. These FEPs will also be considered herein. 
Table 2. EBS FEPs Developed by Project 
FEP 
ebs # FEP Name Issues(s) 
1 Pedestal Collapse The waste package, as a result of pedestal collapse, lies on or in the invert and could be 
in contact with the drip shield and the rails, and be exposed to contact corrosion. While 
bedded in the invert, the waste package is more likely to see local ponding and the 
enhanced corrosion and mobilization which might accompany it. 
2 Drip Shield Liquid water contact with the waste package is believed to affect the rate of corrosion of 
the metals, exposing the waste. The drip shield is intended to reduce direct liquid 
contact with the containers. 
3 Drip Shield Supports Failure of the drip shield supports allows the drip shield to make contact with the waste 
package or with the rails. Since the drip shield is made of Ti, the rails of steel, and the 
waste packages of a high-nickel alloy, contact could result in contact corrosion possibly 
affecting the integrity of the waste package. 
4 Backfill Crushed Rock is placed to protect the waste package, or the drip shield and waste 
package from rockfall, failure of ground support, and possibly as a Richards barrier for 
flow. Location of backfill, the size, and material type, all affect water chemistry (and the 
corrosion rates for drip shield and waste packages, dissolution rates for waste), and 
thermal properties (and waste temperatures and cladding failure). Suggestions for 
material type currently include sand, crushed limestone, marble, and crushed tuff. The 
last is the subject of investigation. 
5 Invert The invert materials, currently expected to be crushed rock, form the bed for the rails and 
will be the resting place for the waste package after the support pedestals fail. The invert 
is part of the flow pathway from the waste to the drift bottom and exit from the drift. The 
invert is also part of the flow pathway for water deflected by the drip shield from the waste 
packages. Water can accumulate in the invert, acting as a water vapor source for 
corrosion or possibly ponding. Accordingly, invert materials affect water chemistry for 
transport. 
6 Rockfall Loading Distortion 
of Drip Shield 
Contact corrosion, compromising the drip shield or the waste package develops as a 
result of displacement or distortion of the drip shield. 
7 Rails Rails represent a material, steel, added to the repository which is not necessary to longterm 
isolation, but which may have an impact on corrosion of the drip shield and on water 
chemistry for transport. If the Ti drip shield and the steel rails are in contact, contact 
corrosion is expected, which could affect the long-term ability of the drip shield to divert 
water from the waste package. Such contact would be expected locally as a result of a 
seismic disturbance, rockfall, or ground support failure. 
8 Pedestal The pedestal may be distorted or rack because of floor heave (thermo-mechanical stress 
adjustment) and ground motion (seismic event), or may fail due to corrosion. Failure by 
any mode will drop the waste package onto or into the invert. 
9 Ground Motion Ground motion, generated by seismic events, provides accelerations to components of 
the repository, including the waste packages, drip shield, surrounding rock, and ground 
support. These accelerations cause relative motion of the components and could 
generate ground support failure, rockfall, and damage to waste packages and drip 
shields. 
10 Drip Shield Movement 
Relative to Waste 
Packages/Rails 
Contact of the Ti drip shield with the waste package or with the steel rails will cause 
contact corrosion. In the former case, corrosion of the waste package will be enhanced, 
while in the latter case, that of the drip shield will be accelerated. Presumably, the fate 
of the rails is inconsequential. 
11 Relative Seismic 
Displacement 
A seismic event in the potential repository generates relative displacements between 
waste package, drip shield, and rails, and ground support failure, and rockfall. 
12 Ground Support Failure Failure of ground support, for whatever reason, allows rockfall, displacement of waste 
packages, and development of new flow pathways. Possible cases include ground 
motion, thermo-mechanical stress adjustment and corrosion.

Table 2. EBS FEPs Developed by Project  Continued 
ANL-WIS-PA-000002 REV 00 ICN 01 14 September 2000 
FEP 
ebs # FEP Name Issues(s) 
13 Thermo-Mechanical 
Evolution of a Repository 
Block 
Thermo-mechanical coupling, which alters the stress state of the rock surrounding the 
repository, affects floor buckling, fracture sealing and openings to the EBS, and loading 
and unloading of ground support. 
14 Shear Fracture/ Fault 
Movement and Relaxation 
Fractures that might otherwise be closed during the thermal period, because of 
compression from thermal expansion, are maintained as open pathways because of 
shear movement. Movement also allows distortion of the drift and the relative location of 
drip shield, rails, and waste packages, with possible contact being established. 
15 Condensation Beneath Drip 
Shield 
Condensation on the inner surface of the drip shield circumvents its performance and 
provides water to drip onto the waste package and its supporting pedestal. Enhanced 
corrosion of waste package and pedestal becomes possible. 
16 Reflux Drainage of 
Condensate Zone 
Condensate zones could contain a substantial amount of mobile water able to flow back 
into the drifts, perhaps as a single extended episode. 
17 Flow along Drip Shield 
(inside) Wall 
Water vapor is available from water otherwise diverted from the waste packages, which 
flows down the drip shield and enters the invert, where it may accumulate. 
18 Flow Through Backfill Flow through the backfill reacts chemically with the backfill. This chemically altered 
water then interacts with the drip shield and rails to eventually reach the invert. 
19 Movement of Backfill 
Through Gaps and 
Separations in Drip Shield 
The continuity of the drip shield and its ability to deflect liquid water could be 
compromised as a result of movement produced by thermo-mechanical or seismic 
processes. 
20 Fluid Flow into Gaps and 
Separations in Drip Shield 
The ability of the drip shield to deflect liquid water could be compromised as a result of 
the movement of liquid water through gaps or spaces which develop between drip shield 
segments. 
21 Ground Support  Wire 
Mesh and Rockbolts 
The expected life of ground support after the operational phase of the repository is 
unknown. Failure of ground support allows rockfall and development of a chimney or 
enlarged drift and filling of fracture or fault zones. 
22 Ground Support  
Rockbolts and Grout 
The issues are that ground support introduces materials (Fe, grout, etc.) into the facility, 
which affects water chemistry. All ground support eventually fails, allowing rockfall, 
altering drift size and properties, and affecting flow pathways. 
23 Drains (if used) Water accumulation in the drift would wet the invert materials, possibly pond, and provide 
a continuing source of water vapor beneath the drip shield and backfill for interaction with 
waste packages and their supports. 
24 Flow Along Drip Shield 
(outside) Wall 
Since the segmented drip shield will see liquid water, the concerns are the effectiveness 
of the diversion (i.e., will liquid flow pass through the overlaps) and the corrosion 
resistance of the drip shield material to the water chemistry in the impinging water. 
25 Microbial Activity The concern is microbially accelerated corrosion and mobilization occurring in the warm, 
moist environment of the EBS. 
26 Rockbolt/Grout Corrosion The corrosion and alteration changes the flow path for water entrance and alters the 
chemistry of the water following those flow paths. 
27 Drainage with Transport  
Sealing and Plugging 
Normal functioning of drainage in the drifts is not established, so how drainage will 
change if fractures are plugged is unclear. Suggestions include ponding until fractures in 
the wall are reached by the water level or until there is sufficient head to clear the 
fractures. 
28 Drainage  Through 
Constructed Drains 
Water accumulation would be possible in a drift, particularly in a region of floor buckling, 
if normal drainage is blocked. Such blockage could occur if fines and debris are 
deposited in fractures or as sediment along the drift floor. Excess water could allow 
more rapid corrosion and contaminant mobilization. 
The conundrum here is that rapid draining of water sooner might also mean rapid draining 
of contaminated water later. 
29 Drainage with Transport  
Ponding 
Water could accumulate in the invert in sufficient amounts to flood the waste package, 
enhancing corrosion and eventual mobilization. 
Criticality could be a possible consequence. 
30 Drip Shield Corrosion  
Flow of Backfill Through 
The continuity of the drip shield and its ability to deflect liquid water could be 
compromised as a result of holes produced by corrosion.

Table 2. EBS FEPs Developed by Project  Continued 
ANL-WIS-PA-000002 REV 00 ICN 01 15 September 2000 
FEP 
ebs # FEP Name Issues(s) 
Corroded Elements 
31 Drip Shield Corrosion  
Fluid Flow Through 
Corroded Elements to 
Waste Packages 
Deflection of liquid water away from the waste packages depends on continuity of the drip 
shield and the absence of penetrations. 
32 Corrosion of Drip Shields 
and Waste Packages 
Corrosion may contribute to waste package failure. Corrosion is most likely to occur at 
locations where water drips on the waste packages, but other mechanisms should be 
considered. 
33 Local, disruptive ground 
motion is produced by an 
earthquake occurring 
outside the potential 
repository 
Local, disruptive ground motion is produced by an earthquake occurring outside the 
potential repository 
34 Faulting or movement on an 
existing fault occurs 
through the potential 
repository 
Faulting or movement on an existing fault occurs through the potential repository 
35 Thermo- chemical alteration 
of glasses to clays and 
zeolites, in this unit 
beneath the potential 
repository, accompanied by 
volume increases which 
appear at the nearest free 
surface, namely the drift 
floors. 
Thermo- chemical alteration of glasses to clays and zeolites, in this unit beneath the 
potential repository, accompanied by volume increases which appear at the nearest free 
surface, namely the drift floors. 
36 A basaltic intrusion 
intersects potential 
repository drifts and may 
reach the surface. EBS 
design and performance is 
of little significance for this 
occurrence. 
A basaltic intrusion intersects potential repository drifts and may reach the surface. EBS 
design and performance is of little significance for this occurrence. 
37 Stress alteration, increase, 
and relaxation during 
repository life causes 
massive failure of ground 
support, initiating a 
sequence of associated 
failures 
Stress alteration, increase, and relaxation during repository life causes massive failure of 
ground support, initiating a sequence of associated failures 
Note: FEPs ebs # 33-37 were not numbered in CRWMS M&O 2000c 
1.2 FEPs IDENTIFICATION AND ANALYSIS 
For the YMP TSPA, a scenario is defined as a subset of the set of all possible futures of the 
engineered barrier system that contains the futures resulting from a specific combination of FEPs. 
The first step of the scenario development process is the identification of FEPs potentially relevant 
to the performance of the Yucca Mountain repository. The most current list of FEPs is contained 
in the YMP FEPs database (CRWMS M&O 2000nn). A comprehensive discussion of the origin of 
these FEPs, their organization, and their assignment to the various PMRs is provided in the 
documentation accompanying the database (CRWMS M&O 2000nn). A brief summary of that 
discussion follows.

ANL-WIS-PA-000002 REV 00 ICN 01 16 September 2000 
The initial set of FEPs was created for the Yucca Mountain TSPA by combining lists of FEPs 
previously identified as relevant to the Yucca Mountain Project (YMP) (e.g., Total System 
Performance Assessment-1995: An Evaluation of the Potential Yucca Mountain Repository, 
CRWMS M&O 1995a) with a draft FEP list compiled by the Nuclear Energy Agency (NEA) of the 
Organization for Economic Co-Operation and Development (OECD) (Safety Assessment 
Management 1997). The NEA list is maintained as an electronic FEP database and is the most 
comprehensive list available internationally. The list currently contains 1261 FEPs from 
Canadian, Swiss, and Swedish spent-fuel programs, intermediate and low-level waste programs of 
the U.K., and the US Waste Isolation Pilot Plant (WIPP) program. An additional 292 FEPs have 
been identified from YMP literature and site studies, and 82 FEPs have been identified during 
YMP project staff workshops. These FEPs are organized under 151 categories, based on NEA 
category headings, resulting in a total of 1786 entries. Consistent with the diverse backgrounds of 
the programs contributing FEPs lists, FEPs have been identified by a variety of methods, including 
expert judgement, informal elicitation, event tree analysis, stakeholder review, and regulatory 
stipulation. All potentially relevant FEPs have been included, regardless of origin. This approach 
has led to considerable redundancy in the FEP list, because the same FEPs are frequently 
identified by multiple sources, but it also ensures that a comprehensive review of narrowly 
defined FEPs will be performed. The FEPs list (CRWMS M&O 2000nn) is considered open and 
will continue to grow as additional FEPs are identified. 
Under the definition adopted for the Yucca Mountain TSPA, a scenario is defined as a subset of 
the set of all possible futures of the engineered barrier system that contains the futures resulting 
from a specific combination of FEPs. There is no uniquely correct level of detail at which to 
define scenarios or FEPs. Decisions regarding the appropriate level of resolution for the analysis 
are made based on consideration of the importance of the scenario in its effect on overall 
performance and the resolution desired in the results. The number and breadth of scenarios 
depend on the resolution at which the FEPs have been defined: coarsely defined FEPs result in 
fewer, broad scenarios, whereas narrowly defined FEPs result in many narrow scenarios. For 
efficiency, both FEPs and scenarios should be aggregated at the coarsest level at which a 
technically sound argument can be made that is adequate for the purposes of the analysis. 
Consequently, each FEP has been identified as either a Primary or Secondary FEP. Primary FEPs 
are those FEPs for which the project proposes to develop detailed screening arguments. The 
classification and description of Primary FEPs strives to capture the essence of all the Secondary 
FEPs that map to the primary. For example, the Primary FEP "Physical and Chemical Properties 
of Backfill" can be used appropriately to resolve multiple and redundant Secondary FEPs that 
address various aspects of the backfill properties and their impact on groundwater flow and 
radionuclide transport at YMP. By working to the Primary FEP description, the subject matter 
experts assigned to the Primary FEP address all relevant Secondary FEPs, and arguments for 
Secondary FEPs can be rolled into the Primary FEP analysis. Secondary FEPs are either FEPs 
that are completely redundant or that can be aggregated into a single Primary FEP. 
To perform the screening and analysis, the FEPs have been assigned based on the PMR structure 
so that the analysis, screening decision, and TSPA disposition reside with the subject matter 
experts in the relevant disciplines. The TSPA recognizes that FEPs have the potential to affect

ANL-WIS-PA-000002 REV 00 ICN 01 17 September 2000 
multiple facets of the project, may be relevant to more than one PMR, or may not fit neatly within 
the PMR structure. For example, many FEPs affect waste form (WF), waste package (WP), and 
the EBS. Rather than create multiple separate FEPs, the FEPs have been assigned, as applicable, 
to one or more process modeling groups, which are responsible for the AMRs. 
At least two approaches have been used to resolve overlap and interface problems of multiple 
assigned FEPs. FEP owners from different process modeling groups may decide that only one 
PMR will address all aspects of the FEP, including those relevant to other PMRs. Alternatively, 
FEP owners may each address only those aspects of the FEP relevant to their area. In either case, 
the FEP AMR produced by each process modeling group lists the FEP and summarizes the 
screening result, citing the appropriate work in related AMRs as needed. 
This AMR addresses the 86 FEPs that have been identified as Primary EBS FEPs, as discussed in 
CRWMS M&O 2000nn. In addition, the 37 EBS FEPs identified internal to the project (CRWMS 
M&O 2000c) are also addressed. In those cases where the FEP is relevant to other process 
modeling groups, only the relevance of the FEP to the EBS is discussed herein. Overlap with 
other process modeling groups occurs for the following areas; WF degradation (CRWMS M&O 
2000x), WP degradation (CRWMS M&O 2000dd), tectonics evaluation (CRWMS M&O 2000z), 
the near-field environment (NFE) as defined by its thermal hydrology and coupled processes 
(CRWMS M&O 2000y), and the unsaturated zone (CRWMS M&O 2000bb). It should be noted 
that in a few cases such a FEP has been designated as excluded from the TSPA relative to the 
EBS. It is important to note, however, that such a designation of exclude for the EBS does not 
mean that the FEP is necessarily excluded relative to another process modeling group. 
1.3 FEPs SCREENING AND ANALYSIS PROCESS 
As described in Section 1.2, the first step in the scenario development process was the 
identification and analysis of FEPs. The second step in the scenario development process includes 
the screening of each FEP. Each FEP is screened for inclusion or exclusion in the TSPA against 
three criteria, which are stated as regulatory requirements at NRCs proposed rule 10 CFR Part 63 
(64 FR 8640), and in the U.S. Environmental Protection Agency's (EPA) proposed rule 40 CFR 
Part 197 (64 FR 46976). The screening criteria are discussed in more detail in Section 4.2 and 
are summarized here. 
 Is the FEP specifically ruled out by the guidance or proposed regulations, or contrary to 
the stated guidance or regulatory assumptions? 
 Does the FEP have a probability of occurrence less than 10-4 in 104 years? 
 Will the resulting expected annual dose be significantly changed or the results of the 
performance assessment be changed significantly by omission of the FEP? (Note: 
significantly changed and changed significantly are undefined terms in the DOE

ANL-WIS-PA-000002 REV 00 ICN 01 18 September 2000 
Interim Guidance and in the EPAs proposed regulations. These terms are inferred to be 
equivalent to having no or negligible effect.) 
The regulatory screening criteria contained in DOEs interim guidance (Dyer 1999) and in the 
proposed 40 CFR Part 197 (64 FR 46976) are relevant to many of the FEPs. FEPs that are 
contrary to DOEs interim guidance, or specific proposed regulations, regulatory assumptions, or 
regulatory intent are excluded from further consideration. Examples include: the explicit exclusion 
of consideration of all but a stylized scenario to address treatment of human intrusion (10 CFR 
63.113(d)), assumptions about the critical group to be considered in the dose assessment (10 
CFR 63.115), and the intent that the consideration of "the human intruders" be excluded from the 
human intrusion assessment (64 FR 8640, Section XI. Human Intrusion). 
Probability estimates used in the FEPs screening process may be based on technical analysis of the 
past frequency of similar events (such as igneous and seismic events) or, in some cases, on expert 
elicitation. Probability arguments, in general, require including some information about the 
magnitude of the event in its definition. Probability arguments are also sensitive to the spatial and 
temporal scales at which FEPs are defined. For example, the definition of the probability of a 
seismic event depends on the magnitude of the event. Probability arguments are therefore made at 
reasonably coarse scales. 
Consequence-based screening arguments can be established in a variety of ways. Various methods 
include TSPA sensitivity analyses, modeling studies outside of the TSPA, or reasoned arguments 
based on literature research. For example, consequences of many geomorphic processes such as 
erosion and sedimentation can be evaluated by considering bounding rates reported in geologic 
literature. More complicated processes, such as igneous activity, require detailed analyses 
conducted specifically for the Yucca Mountain Project. Low-consequence arguments are often 
made by demonstrating that a particular FEP has no effect on the distribution of an intermediate 
performance measure in the TSPA. For example, by demonstrating that including a particular WF 
has no effect on the concentrations of radionuclides transported from the repository in the aqueous 
phase, it is also demonstrated that including this waste form in the inventory would not 
compromise compliance with the performance objectives. Explicit modeling of the characteristics 
of this waste form could therefore be excluded from the TSPA. 
Using the type of arguments discussed above, each FEP identified as relevant to the EBS was 
reviewed against the three exclusion criteria. Those that were determined to meet one of the three 
criteria were designated as excluded from further consideration within the TSPA. Those that 
did not meet one of these criteria must, by definition, be included. 
1.4 ORGANIZATION OF FEP DATABASE 
Under a separate scope, the TSPA team is constructing an electronic database to assist project 
reviewers during the license review process. Each FEP has been entered as a separate record in 
the database. Fields within each record provide a unique identification number, a description of 
the FEP, the origin of the FEP, identification as a Primary or Secondary FEP for the purposes of

ANL-WIS-PA-000002 REV 00 ICN 01 19 September 2000 
the TSPA, and mapping to related FEPs and to the assigned PMRs. Fields also provide summaries 
of the screening arguments with references to supporting documentation and AMRs, and, for all 
retained FEPs, statements of the disposition of the FEP within the TSPA modeling system. The 
AMRs, however, contain the detailed arguments and description of the disposition of the subject 
FEPs. 
Alphanumeric identifiers (called the NEA category) previously used have been retained in the 
database for traceability purposes. Each FEP has also been assigned a unique YMP FEP database 
number, based on the NEA categories. The database number is the primary method for identifying 
FEPs, and consists of an eight-digit number of the form x.y.zz.pp.qq. The general structure of the 
database is reflected in the first two digits (x.y) as shown below: 
0.0. Assessment Basis 
1.0. External Factors 
1.1 Repository Issues 
1.2 Geological Processes and Effects 
1.3 Climatic Processes and Effects 
1.4 Future Human Actions (Active) 
1.5 Other 
2.0. Disposal System - Environmental Factors 
2.1 Wastes and Engineered Features 
2.2 Geologic Environment 
2.3 Surface Environment 
2.4 Human Behavior 
3.0. Disposal System - Radionuclide/Contaminant Factors 
3.1 Contaminant Characteristics 
3.2 Contaminant Release/Migration Factors 
3.3 Exposure Factors 
The next four digits (zz.pp) define a grouping structure for the FEPs, with zz designating the 
category, and pp designating the heading. The exact details of this grouping structure are not 
important to the evaluation, since each FEP will be evaluated regardless of the database 
organization. Finally, the last two digits (qq) signify whether the FEP is primary (00) or 
Secondary (other than 00). Each heading has a Primary FEP associated with it, and may or not 
have any Secondary FEPs. In those cases where Secondary FEPs do exist, the Primary FEP 
encompasses all the issues associated with the Secondary FEPs. The Secondary FEPs either 
provide additional detail concerning the primary, or are a restatement of the primary based on 
redundant input from a different source.

ANL-WIS-PA-000002 REV 00 ICN 01 20 September 2000 
2. QUALITY ASSURANCE 
The activities documented in this AMR were evaluated in accordance with QAP-2-0, Conduct of 
Activities and were determined to be quality affecting and subject to the requirements of the U.S. 
DOE Office of Civilian Radioactive Waste Management (OCRWM) Quality Assurance 
Requirements and Description (QARD) (DOE 2000). This evaluation is documented in Conduct 
of Performance Assessment (CRWMS M&O 1999d). Accordingly, the modeling or analysis 
activities documented in this AMR have been conducted in accordance with the Civilian 
Radioactive Waste Management System Management and Operating Contractor (CRWMS M&O) 
quality assurance program, using approved procedures identified in Development Plan: EBS 
FEPs/Degradation Modes Abstraction (CRWMS M&O 1999a). 
More specifically, this AMR has been developed in accordance with procedure AP-3.10Q, 
Analyses and Models. Preparation of this analysis did not require the classification of items in 
accordance with QAP-2-3, Classification of Permanent Items. This activity is not a field 
activity. Therefore, an evaluation in accordance with NLP-2-0, Determination of Importance 
Evaluations was not required. 
The initial list of 86 Primary EBS FEPs addressed in this AMR was derived from the YMP FEP 
Database Rev. 00 (CRWMS M&O 2000nn). The additional 37 EBS FEPs identified internal to 
the project (CRWMS M&O 2000c) will also be addressed herein to determine if additional EBS 
Primary FEPs need to be included in the database. Rev 00 of the FEPs database is a Level 3 
Milestone, as part of the Total System Performance Assessment - Site Recommendation (TSPASR) 
deliverables. Thus, it will be maintained and modified as appropriate in accordance with 
AP-SV.1Q, Control of the Electronic Management of Data. 
3. COMPUTER SOFTWARE AND MODEL USAGE 
This AMR uses no computational software or model. The AMR was developed using only 
commercially available software (Microsoft Word 97) for word processing, which is exempt from 
qualification requirements in accordance with AP-SI.1Q, Software Management. There were no 
additional applications (routines or macros) developed using this commercial software. The 
analyses and arguments presented herein are based on regulatory requirements, results of analyses 
presented and documented in other AMRs, or technical literature.

ANL-WIS-PA-000002 REV 00 ICN 01 21 September 2000 
4. INPUTS 
4.1 DATA AND PARAMETERS 
The nature of the FEPs screening arguments and TSPA dispositions is such that cited data and 
values form the basis of reasoned argument, as opposed to inputs to computational analyses or 
models. The data cited in the FEPs screening arguments is largely non-critical, and conclusions 
will be formulated such that they will not be affected by the degrees of uncertainty accounted for in 
the TSPA. 
In addition to the above input, the potential repository baseline design (CRWMS M&O 2000ii) 
was used as the reference design for the purpose of FEP identification and analysis. The design 
documented therein does consider the use of backfill material within the EBS. On January 26, 
2000, a design change was initiated to resolve certain thermal design issues. This design change 
will result in a greater ability of the waste packages to reject heat after closure of the repository, 
thereby maintaining the two thermal requirements. The first requirement is protective of the fuel 
cladding, and the second requires that a section of the rock pillar between drifts remain below the 
boiling temperature of water, providing a path for water drainage. This design change is described 
in the Monitored Geologic Repository Project Description Document (CRWMS M&O 2000ii). 
This AMR originally considered a design with backfill, and is now being updated to address the 
design without backfill. 
4.2 CRITERIA 
This AMR complies with the DOE interim guidance (Dyer 1999). Subparts of the interim 
guidance that apply to this analysis or modeling activity are those pertaining to the characterization 
of the Yucca Mountain site (Dyer 1999, Subpart B, Section 15). In particular, relevant parts of the 
guidance include the compilation of information regarding geology, hydrology, and geochemistry 
of the site (Dyer 1999, Subpart B, Section 21(c)(1)(ii)), and the definition of geologic, hydrologic, 
and geochemical parameters and conceptual models used in performance assessment (Dyer 1999, 
Subpart E, Section 114(a)). 
Technical screening criteria are provided in DOEs interim guidance (Dyer 1999) and have also 
been identified by the NRC in the proposed 10 CFR Part 63 (64 FR 8640) and by the EPA in the 
proposed 40 CFR Part 197 (64 FR 46976). Both proposed regulations specifically allow the 
exclusion of FEPs from the TSPA if they are of low probability (less than one chance in 10,000 of 
occurring in 10,000 years) or if occurrence of the FEP can be shown to have no significant effect 
on expected annual dose. There is no quantified definition of significant effect in the guidance 
or proposed regulations. 
4.2.1 Low Probability 
The probability criterion is explicitly stated by the NRC in the proposed 10 CFR 63.114 (d):

ANL-WIS-PA-000002 REV 00 ICN 01 22 September 2000 
Consider only events that have at least one chance in 10,000 of occurring over 10,000 
years. 
The EPA provides essentially the same criterion in 40 CFR 197.40: 
The DOEs performance assessments should not include consideration of processes or 
events that are estimated to have less than one chance in 10,000 of occurring within 10,000 
years of disposal. 
4.2.2 Low Consequence 
Criteria for low consequence screening arguments are provided in DOEs interim guidance (Dyer 
1999, Section 114(e) and (f)), which indicates that performance assessment shall: 
(e) Provide the technical basis for either inclusion or exclusion of specific features, 
events, and processes of the geologic setting in the performance assessment. Specific 
features, events, and processes of the geologic setting must be evaluated in detail if the 
magnitude and time of the resulting expected annual dose would be significantly 
changed by their omission. 
(f) Provide the technical basis for either inclusion or exclusion of degradation, 
deterioration, or alteration processes of engineered barriers in the performance 
assessment, including those processes that would adversely affect the performance of 
natural barriers. Degradation, deterioration, or alteration processes of engineered 
barriers must be evaluated in detail if the magnitude and time of the resulting expected 
annual dose would be significantly changed by their omission. 
The EPA provides essentially the same criteria in 40 CFR 197.40: 
with the NRCs approval, the DOEs performance assessment need not evaluate, in detail, 
the impacts resulting from any processes and events or sequences of processes and events 
with a higher chance of occurrence if the results of the performance assessment would not be 
changed significantly. 
The terms significantly changed and changed significantly are undefined terms in the DOE 
interim guidance and in the EPAs proposed regulations. These terms are inferred for FEPs 
screening purposes to be equivalent to having no or negligible effect. Because the relevant 
performance measures differ for different FEPs (e.g., effects on performance can be measured in 
terms of changes in concentrations, flow rates, travel times, and other measures, as well as overall 
expected annual dose), there is no single quantitative test of significance.

ANL-WIS-PA-000002 REV 00 ICN 01 23 September 2000 
4.2.3 Reference Biosphere 
Both DOEs interim guidance (Dyer 1999) and EPAs proposed regulations specify assumptions 
(which in effect serve as criteria) pertinent to screening many of the EBS FEPs. Particularly 
germane are explicit assumptions regarding the reference biosphere (10 CFR 63.115), and less so 
are assumptions regarding the location and use of groundwater by the critical group used for 
calculation of exposure doses. 
The assumptions pertaining to the characteristics of the reference biosphere are presented in 
DOEs interim guidance (Dyer 1999, Section 115(a)(1,4)). The specified characteristics pertinent 
to the EBS FEPs are that: 
(1) Features, events, and processes shall be consistent with present knowledge of the 
conditions in the region surrounding the Yucca Mountain site. 
(4) Evolution of the geologic setting shall be consistent with present knowledge of natural 
processes. 
The EPA has specified a similar assumption in proposed 40 CFR 197.15. This assumption is 
stated as: 
 DOE must vary factors related to the geology, hydrology, and climate based on 
environmentally protective but reasonable scientific predictions of the changes that could 
affect the Yucca Mountain disposal system over the next 10,000 years. 
4.3 CODES AND STANDARDS 
There are no Codes or Standards directly applicable to this analysis. 
5. ASSUMPTIONS 
5.1 GENERAL ASSUMPTIONS 
There are two general assumptions used in the screening of the EBS FEPs. 
5.1.1 Future Geologic Setting 
As directed by DOEs interim guidance (Dyer 1999, Section 114(1)), the TSPA assumes that 
future geologic settings will be within the range of conditions that are consistent with present 
knowledge of natural processes.

ANL-WIS-PA-000002 REV 00 ICN 01 24 September 2000 
This assumption is particularly germane to EBS FEPs, since the FEPs are screened based on 
known processes or phenomena that could potentially affect future states of the system. 
Discernible impacts from past events on the geologic setting are inherently reflected in the present 
knowledge of natural processes that form the basis of the TSPA. If the subject FEP phenomena do 
not have a documented past occurrence within the geologic time scale of concern and/or within the 
study area, or if past events are of an insignificant consequence, then it is by definition a low 
probability or low consequence event and can be excluded from consideration. 
5.1.2 Repository Closure 
The TSPA is based on an assumption that the repository will be constructed, operated, and closed 
according to regulatory requirements during the construction period. 
This assumption is particularly germane to FEPs involving off-normal events during the 
construction phase of the repository or deviations from the as-designed repository configuration. 
By definition, such events and/or design deviations will not be explicitly considered in the TSPA. 
These two assumptions are justified based on the conditions specified in DOEs interim guidance 
(Dyer 1999), which require special and periodic reporting of (1) progress of construction, (2) data 
not within predicted limits on which the facility design is based, and (3) any deficiency, that if 
uncorrected, could adversely affect safety. Additionally, restrictions on subsequent changes to the 
features or procedures will be a condition of construction authorization. Furthermore, the existing 
regulations specified in 10 CFR 63 Subpart F (Dyer 1999) require that a performance confirmation 
program be instituted. The focus of the program is to confirm the geotechnical design parameters 
and to ensure that appropriate action is taken to inform the NRC of changes needed to 
accommodate actual field conditions. It also includes provisions for design testing and monitoring 
of testing of waste packages to verify in-situ performance of the waste package design. The 
requirement is for these activities to be conducted in a manner that does not adversely affect the 
ability of the geologic and engineered elements of the geologic repository to meet the performance 
objectives. Additionally, all of these activities are subject to the quality assurance requirements 
specified in 10 CFR 63 Subpart G (Dyer 1999). Regardless of this assumption, the TSPA includes 
the possibility that engineered systems may not perform optimally for the full 10,000 years. For 
example, the premature failure of some waste packages is included in the TSPA through the 
probabilistic treatment of waste package degradation. 
5.2 FEP-SPECIFIC ASSUMPTIONS 
This section lists the EBS-specific assumptions used in Section 6. All of the assumptions were 
used as reference or logical analysis assumptions to facilitate the identification and analysis of 
FEPs and degradation scenarios. None of the assumptions are a requirement that need to be 
substantiated and, hence, none carries a TBV. It is particularly noted that, conceptually, all of 
the events and processes identified are potential scenarios, and as such, are assumed to occur for

ANL-WIS-PA-000002 REV 00 ICN 01 25 September 2000 
the purpose of analysis. It is also noted that the current repository baseline design (CRWMS 
M&O 2000ii) is used as a point of departure for FEP identification, but the latter is not restricted 
by the configuration or design requirements specified in that baseline. Examples of FEPs that go 
beyond the baseline are the development of gaps between drip shield segments due to a seismic 
event. 
5.2.1 Engineered Barrier System Description 
The EBS is assumed to extend as far into the rock as the reach of the ground support system 
(approximately 5 m if rock bolts are used). Thus, chemical processes involving such rock bolts 
and the surrounding cement are considered, as is degradation of the drift wall in this region. 
However, the determination of seepage flow into the tunnel, including the impact of geophysical 
changes in this region of the rock, is an NFE issue and is not considered as part of this EBS 
discussion. All flow into the tunnel is assumed to be provided as a boundary condition by the NFE 
analysis. 
5.2.2 Reference Repository Design 
The Enhanced Design Alternative II, as described in the baseline design (CRWMS M&O 2000ii), 
is used as the reference design for FEP identification. Additional information is provided in the 
License Application Design Selection Report (LADS) (CRWMS M&O 1999b), as well as earlier 
documentation on subsurface facilities (CRWMS M&O 2000gg) and ground control systems 
(CRWMS M&O 2000hh). Key features of this design include the waste package sitting atop a 
pedestal and invert and a drip shield to minimize water contact with the waste packages. No 
backfill is considered in the current design, although the potential use of backfill can be reevaluated 
if that option is selected in the future. An extended period of preclosure ventilation 
ensures that maximum waste package temperatures are kept below allowable limits. However, 
departures from the baseline due to the potential occurrence of FEPs are also addressed. 
5.2.3 Degradation 
Evolution of the repository over time is assumed to never result in improvements in performance. 
 As the potential repository and Yucca Mountain evolve, the properties of EBS components 
such as the ground support and the drip shield, which are subjected to processes, depart 
from their original design characteristics. By assumption, it is presumed that any such 
departure degrades the function of the component, and design lifetimes and safety factors are 
selected on the basis of that premise. 
 The design philosophy currently assumes no credit for favorable alterations to the repository 
system (e.g., encasement of WPs in calcium carbonate precipitated from incoming water).

ANL-WIS-PA-000002 REV 00 ICN 01 26 September 2000 
5.2.4 Degradation During Preclosure Period 
Degradation that occurs during the preclosure period would be detected and fixed. Thus, the 
FEPs identified are mostly those that occur during the postclosure period. 
5.2.5 Process Starting Point 
The starting point of most EBS processes is assumed to be the entry of water into the emplacement 
drift. It is with the introduction of water that key degradation processes such as corrosion start to 
occur. However, there are certain processes that are independent of water ingress that must also 
be considered. These include, for example, rock fall and the deposition of dust on the waste 
packages and drip shields during the preclosure period. Rock fall may occur at any time and could 
represent a mechanism for drip shield damage. Dust deposited on the drip shields and waste 
packages would serve as loci for surface wetting when the relative humidity increases, but prior to 
liquid water entry. 
All data associated with water entry into the emplacement drift, including timing, rate, 
temperature, chemistry, etc., are assumed to be developed in the unsaturated zone and near field 
environment PMRs. 
6. ANALYSIS/MODEL 
The method used for this analysis is a combination of qualitative and quantitative screening of 
FEPs. The analyses are based on the criteria provided in the DOEs interim guidance (Dyer 1999) 
and by the EPA in the proposed 40 CFR Part 197 (64 FR 46976). These criteria are used to 
determine whether each FEP should be included in the TSPA. 
For FEPs that are excluded based on specific regulatory requirements (e.g., requirements 
regarding the location and composition of the critical group), the screening argument includes the 
regulatory reference and a short discussion of the applicability of the standard. 
For FEPs that are excluded from the TSPA based on DOEs interim guidance or EPA criteria, the 
screening argument includes the basis of the exclusion (low probability, low consequence) and 
provides a short summary of the screening argument. As appropriate, screening arguments cite 
work done outside this activity, such as in other AMRs. 
For FEPs that are included in the TSPA, the TSPA Disposition includes a reference to the AMR 
that describes how the FEP has been incorporated in the process models or the TSPA abstraction.

ANL-WIS-PA-000002 REV 00 ICN 01 27 September 2000 
6.1 ALTERNATIVE APPROACHES 
To ensure clear documentation of the treatment of potentially relevant future states of the system in 
the Yucca Mountain License Application, the DOE has chosen to adopt a scenario development 
process based on the methodology developed by Cranwell et al. (1990) for the NRC. The 
approach is fundamentally the same as that used in many performance assessments. The approach 
has also been used by the DOE for the Waste Isolation Pilot Plant (WIPP) (DOE 1996), by the 
NEA, and by other radioactive waste programs internationally (e.g., Skagius and Wingefors 1992). 
Regardless of the "scenario" method chosen for the performance assessment, the initial steps in the 
process involve development of a FEPs list and screening of the FEPs list for inclusion or 
exclusion. 
The approach used to identify, analyze, and screen the FEPs (as described in Sections 1.2 and 1.3) 
was also considered. Alternative classification of FEPs as Primary or Secondary is possible in an 
almost infinite range of combinations. Classification into Primary and Secondary FEPs is based 
primarily on redundancy and on subject matter. Subsequent assignment and analysis by 
knowledgeable subject matter experts for evaluation appeared to be the most efficient methodology 
for ensuring a comprehensive assessment of FEPs as they relate to the TSPA. Alternative 
classifications and assignments of the FEPs are entirely possible, but would still be based on 
subjective judgement. Alternative approaches for determining probabilities and consequences 
used as a basis for screening are discussed in Section 6.2 under the individual FEP analysis. 
In practice, regulatory-type criteria were examined first, and then either probabilities or 
consequences were examined. FEPs that are retained on one criterion are also considered against 
the others. Consequently, the application of the analysts judgement regarding the order in which 
to apply the criteria does not affect the final decision. Allowing the analyst to choose the most 
appropriate order to apply the criteria prevents needless work, such as developing quantitative 
probability arguments for low consequence events or complex consequence models for low 
probability events. For example, there is no need to develop detailed models of the response of 
the repository to faults shearing a WP, if it can be shown that this event has a probability below the 
criteria threshold. 
Regardless of the specific approach chosen to perform the screening, the screening process is in 
essence a comparison of the FEP against the criteria specified in Section 4.2. Consequently, the 
outcome of the screening is independent of the particular methodology or assignments selected to 
perform the screening. 
Alternative interpretations of data as they pertain directly to the FEPs screening are provided in 
the Analysis and Discussion section for each FEP, as discussed below. The FEPs screening 
decisions may also rely on the results of analyses performed and documented as separate 
activities. Alternate approaches related to separate activities and analyses are addressed in the 
AMRs for those analyses and are not discussed in this AMR.

ANL-WIS-PA-000002 REV 00 ICN 01 28 September 2000 
6.2 EBS FEPs EVALUATION AND ANALYSIS 
This AMR addresses the 86 Primary FEPs that have been identified as EBS FEPs in the FEPs 
database (CRWMS M&O 2000nn), as well as the 37 EBS FEPs identified internal to the project 
by the EBSO. Because the internally identified FEPs were developed independently, there is 
considerable overlap between the two sets of FEPs. Many of the EBSO developed FEPs are a 
restatement of ones that are already in the database. Thus they can be considered to be secondary 
FEPs that do not need to be explicitly discussed herein. Table 3 lists the 37 FEPs developed by 
the EBSO along with a reference to the associated FEPs database primary FEP. In those cases 
where an appropriate existing primary FEP does not exist, the EBSO FEP would be designated as 
new primary. 
Table 3. Relationship of EBSO FEPs to Database FEPs 
FEP 
ebs # FEP Name Corresponding Primary Database FEP 
1 Pedestal Collapse 2.1.06.05.00  Degradation of Invert and Pedestal 
2 Drip Shield 2.1.06.06.00  Effects and Degradation of Drip Shield 
3 Drip Shield Supports 2.1.07.03.00  Movement of Containers (a) 
4 Backfill 2.1.04.0x.00  Five Backfill FEPs (b) 
5 Invert 2.1.06.05.00  Degradation of Invert and Pedestal 
6 Rockfall Loading Distortion of Drip Shield 2.1.07.01.00 - Rockfall 
7 Rails 2.1.09.02.00  Interaction with Corrosion Products 
8 Pedestal 2.1.06.05.00  Degradation of Invert and Pedestal 
9 Ground Motion 2.1.06.05.00  Degradation of Invert and Pedestal (c) 
2.1.06.06.00  Effects and Degradation of Drip Shield 
2.1.06.07.00  Effects at Material Interfaces 
2.1.07.01.00  Rockfall 
2.1.07.02.00  Mechanical Degradation or Collapse of Drift 
10 Drip Shield Movement Relative to Waste 
Packages/Rails 
2.1.06.06.00  Effects and Degradation of the Drip Shield 
11 Relative Seismic Displacement 2.1.06.05.00  Degradation of Invert and Pedestal (c) 
2.1.06.06.00  Effects and Degradation of Drip Shield 
2.1.06.07.00  Effects at Material Interfaces 
2.1.07.01.00  Rockfall 
2.1.07.02.00  Mechanical Degradation or Collapse of Drift 
12 Ground Support Failure 2.1.06.02.00  Effects of Rock Reinforcement Materials 
13 Thermo-Mechanical Evolution of a 
Repository Block 
2.1.08.08.00  Induced Hydrological Changes in the Waste and EBS (d) 
14 Shear Fracture/ Fault Movement and 
Relaxation 
2.1.08.08.00  Induced Hydrological Changes in the Waste and EBS (d) 
(also see ebs #11) 
15 Condensation Beneath Drip Shield 2.1.06.06.00  Effects and Degradation of Drip Shield 
16 Reflux Drainage of Condensate Zone 2.2.07.06.00  Episodic / Pulse Release from Repository 
17 Flow along Drip Shield (inside) Wall 2.1.06.06.00  Effects and Degradation of Drip Shield

Table 3. Relationship of EBSO FEPs to Database FEPs - Continued 
ANL-WIS-PA-000002 REV 00 ICN 01 29 September 2000 
FEP 
ebs # FEP Name Corresponding Primary Database FEP 
18 Flow Through Backfill 2.1.04.01.00  Preferential Pathways in the Backfill 
19 Movement of Backfill Through Gaps and 
Separations in Drip Shield 
2.1.06.06.00  Effects and Degradation of Drip Shield 
20 Fluid Flow into Gaps and Separations in 
Drip Shield 
2.1.06.06.00  Effects and Degradation of Drip Shield 
21 Ground Support  Wire Mesh and 
Rockbolts 
2.1.06.02.00  Effects of Rock Reinforcement Materials 
22 Ground Support  Rockbolts and Grout 2.1.06.01.00  Degradation of Cementitious Materials in Drift 
2.1.06.02.00  Effects of Rock Reinforcement Materials 
23 Drains (if used) 2.1.08.13.00  Drains 
24 Flow Along Drip Shield (outside) Wall 2.1.06.06.00  Effects and Degradation of Drip Shield 
25 Microbial Activity 2.1.10.01.00  Biological Activity in Waste and EBS 
26 Rockbolt/Grout Corrosion 2.1.06.01.00  Degradation of Cementitious Materials in Drift (d) 
2.1.06.02.00  Effects of Rock Reinforcement Materials 
27 Drainage with Transport  Sealing and 
Plugging 
2.1.08.12.00  Drainage With Transport, Sealing and Plugging (d) 
28 Drainage  Through Constructed Drains See ebs # 23 
29 Drainage with Transport  Ponding See ebs # 27 
30 Drip Shield Corrosion  Flow of Backfill 
Through Corroded Elements 
2.1.06.06.00  Effects and Degradation of Drip Shield 
31 Drip Shield Corrosion  Fluid Flow 
Through Corroded Elements to Waste 
Packages 
2.1.06.06.00  Effects and Degradation of Drip Shield 
32 Corrosion of Drip Shields and Waste 
Packages 
2.1.06.06.00  Effects and Degradation of Drip Shield 
33 Local, disruptive ground motion is 
produced by an earthquake occurring 
outside the potential repository 
See database FEP 1.2.01.01.00  Tectonic Activity  large scale, FEP 
1.2.02.01.00  Fractures, and FEP 1.2.03.01.00  Seismicity for 
discussion of integrated effects (e). Specific effects within EBS are 
covered by FEPs above. 
34 Faulting or movement on an existing fault 
occurs through the potential repository 
See database FEP 1.2.01.01.00  Tectonic Activity  large scale, FEP 
1.2.02.01.00  Fractures, and FEP 1.2.03.01.00  Seismicity for 
discussion of integrated effects (e). Specific effects within EBS are 
covered by FEPs above. 
35 Thermo- chemical alteration of glasses to 
clays and zeolites, in this unit beneath the 
potential repository, accompanied by 
volume increases which appear at the 
nearest free surface, namely the drift 
floors. 
2.1.07.06.00  Floor buckling 
36 A basaltic intrusion intersects potential 
repository drifts and may reach the 
surface. EBS design and performance is 
of little significance for this occurrence. 
1.2.04.03.00  Igneous Intrusion 
37 Stress alteration, increase, and relaxation 
during repository life causes massive 
failure of ground support, initiating a 
sequence of associated failures 
2.1.07.02.00  Mechanical Degradation or Collapse of Drift 
(a)  actual WP corrosion due to drip shield contact with waste package is a WP issue 
(b)  5 primary FEPs are included in the database dealing with backfill

Table 3. Relationship of EBSO FEPs to Database FEPs - Continued 
ANL-WIS-PA-000002 REV 00 ICN 01 30 September 2000 
(c)  each of these FEPs is impacted by seismic events 
(d)  effects occurring in the rock outside of the drift are considered in the NFE analysis and would be accounted for in the EBS analysis 
via inlet flow boundary conditions 
(e)  these FEPs are not EBS specific and are not discussed herein 
Each of the 86 primary FEPs from the database (no new primary FEPs taken from the EBSO list 
were identified) is discussed in the sections that follow. For the primary FEPs, the section title 
for each discussion provides the FEP name as incorporated in the FEPs database (CRWMS M&O 
2000nn), as well as the Yucca Mountain FEP number that has been assigned. The FEP description 
is also taken directly from the database, with the exception that in several cases additional text has 
been added to reference applicable Secondary FEPs relevant to the EBS discussion. For the 
additional new primary FEPs, a similar format is used. 
The ongoing modeling and analysis of the EBS is documented in numerous AMRs. These AMRs 
represent the principal references for the discussion on how each FEP is dealt with in the TSPA. 
A list of the AMRs is provided in Table 4 below. In the following discussion on the EBS FEPs, 
the AMR ID number (rather than the document ID number) will be used to reference the relevant 
EBS AMR for that discussion. It should be noted that the key AMRs that define most of the direct 
feeds to the TSPA are E0010, Physical and Chemical Environment Abstraction Model (CRWMS 
M&O 2000b); E0095, EBS Radionuclide Transport Abstraction (CRWMS M&O 2000q); and 
E0080, Drift Degradation Analysis (CRWMS M&O 2000n). For the most part, the other AMRs 
provide supporting modeling detail that support these abstractions, but do not feed the TSPA 
directly. Hence they will typically not be referenced directly in the discussion. 
Also provided in each FEP section is a cross reference to key technical issues identified by the 
NRC (NRC 1998 a-b, NRC 1999a-f, Reamer 1999) as being important for the Yucca Mountain 
repository. These are identified as Issue Resolution Status Report (IRSR) issues. The key 
technical issues and subissues are listed below. The relevance of these subissues to the EBS FEPs 
is identified in Sections 6.2.1 through 6.2.84. Whenever the key technical issue (CLST, for 
example) is identified rather than a specific subissue, all subissues apply. 
Table 4. Engineered Barrier System Relevant Analysis Model Report Identification 
AMR Title AMR ID Reference Document ID Number 
Invert Diffusion Properties Model E0000 CRWMS M&O 2000a ANL-EBS-MD-000031 
Physical and Chemical Environment 
Abstraction Model 
E0010 CRWMS M&O 2000b ANL-EBS-MD-000046 
Engineered Barrier System Features, 
Events, and Processes/Degradation 
Modes Analysis 
E0015 CRWMS M&O 2000c ANL-EBS-MD-000035 
In Drift Corrosion Products E0020 CRWMS M&O 1999c ANL-EBS-MD-000041 
Seepage/Backfill Interactions E0030 CRWMS M&O 2000d ANL-EBS-MD-000039 
In-Drift Gas Flux & Composition E0035 CRWMS M&O 2000e ANL-EBS-MD-000040 
In-Drift Microbial Communities E0040 CRWMS M&O 2000f ANL-EBS-MD-000038 
In-Drift Colloids and Concentrations E0045 CRWMS M&O 2000g ANL-EBS-MD-000042 
EBS Radionuclide Transport Model E0050 CRWMS M&O 2000h ANL-EBS-MD-000034

ANL-WIS-PA-000002 REV 00 ICN 01 31 September 2000 
AMR Title AMR ID Reference Document ID Number 
Seepage/Cement Interactions E0055 CRWMS M&O 2000i ANL-EBS-MD-000043 
Seepage/Invert Interactions E0060 CRWMS M&O 2000j ANL-EBS-MD-000044 
In-Drift Thermal-Hydrological-Chemical 
Model 
E0065 CRWMS M&O 2000k ANL-EBS-MD-000026 
Water Drainage Model E0070 CRWMS M&O 2000l ANL-EBS-MD-000029 
Ventilation Model E0075 CRWMS M&O 2000m ANL-EBS-MD-000030 
Drift Degradation Analysis E0080 CRWMS M&O 2000n ANL-EBS-MD-000027 
Water Diversion Model E0085 CRWMS M&O 2000o ANL-EBS-MD-000028 
Water Distribution and Removal Model E0090 CRWMS M&O 2000p ANL-EBS-MD-000032 
EBS Radionuclide Transport Abstraction E0095 CRWMS M&O 2000q ANL-WIS-PA-000001 
Physical and Chemical Environment 
Model 
E0100 CRWMS M&O 2000r ANL-EBS-MD-000033 
In-Drift Precipitates/Salts Analysis E0105 CRWMS M&O 2000s ANL-EBS-MD-000045 
Multiscale Thermohydrologic Model E0120 CRWMS M&O 2000t ANL-EBS-MD-000049 
Abstraction of Near Field Environment 
Drift Thermodynamic Environment and 
Percolation Flux 
E0130 CRWMS M&O 2000u ANL-EBS-HS-000003 
In-Package Chemistry Abstraction for 
TSPA-LA 
F0170 CRWMS M&O 2000w ANL-EBS-MD-000037 
Container Life and Source Term (CLST) 
CLST1 The effects of corrosion processes on the lifetime of the containers 
CLST2 The effects of phase stability of materials and initial defects on the mechanical 
failure and lifetime of the containers 
CLST3 The rate at which radionuclides in spent nuclear fuel (SNF) are released from the 
EBS through the oxidation and dissolution of spent fuel 
CLST4 The rate at which radionuclides in high-level break (HLW) glass are leached and 
released from the EBS 
CLST5 The effect of in-package criticality on WP and EBS performance 
CLST6 The effect of alternate EBS design features on container lifetime and radionuclide 
release from the EBS 
Evolution of the Near-Field Environment (ENFE) 
ENFE1 Effects of coupled thermal-hydrologic-chemical processes on seepage and flow

ANL-WIS-PA-000002 REV 00 ICN 01 32 September 2000 
ENFE2 Waste package chemical environment 
ENFE3 Chemical environment for radionuclide release 
ENFE4 Effects of thermal-hydrological-chemical (THC) processes on radionuclide 
transport through engineered and natural barriers 
ENFE5 Coupled THC processes affecting potential nuclear criticality in the near field 
Igneous Activity (IA) 
IA1 Probability of future IA 
IA2 Consequences of IA within the repository setting 
Radionuclide Transport (RT) 
RT1 Physical and chemical system affecting RT 
RT2 RT through fractured rock 
RT3 RT through porous rock 
RT4 RT through alluvium 
Repository Design and Thermal-Mechanical Effects (RDTME) 
RDTME1 Design control processes 
RDTME2 Seismic design methodology 
RDTME3 Thermal-mechanical effects on underground facility design and performance 
RDTME4 Design and long-term contribution of seals to performance 
Structural Deformation and Seismicity (SDS) 
SDS1 Fault slip 
SDS2 Seismic motion 
SDS3 Fractures and site discontinuities 
SDS4 Tectonics and crustal conditions 
Thermal Effects on Flow (TEF) 
TEF1 Sufficiency of thermal-hydrologic testing program to assess thermal flux

ANL-WIS-PA-000002 REV 00 ICN 01 33 September 2000 
TEF2 Sufficiency of thermal-hydrologic modeling to predict the nature and bounds of 
thermal effects on flow in the near field 
TEF3 Adequacy of total system performance assessment with respect to thermal effects 
on flow 
Total System Performance Assessment and Integration (TSPAI) 
TSPAI1 Demonstration of the overall performance objective 
TSPAI2 Demonstration of multiple barriers 
TSPAI3 Model abstraction 
TSPAI4 Scenario analysis 
TSPAI5 Transparency and traceability of the analysis 
Unsaturated and Saturated Flow under Isothermal Conditions (USFIC) 
USFIC1 Range of future climates 
USFIC2 Hydrologic effects of climate change 
USFIC3 Amount and spatial distribution of present-day shallow groundwater infiltration 
USFIC4 Amount and spatial distribution of groundwater percolation through repository 
horizon (present-day, and through period of repository performance) 
USFIC5 Ambient flow conditions in the saturated zone and likely dilution mechanisms 
USFIC6 Extent of matrix diffusion in unsaturated and saturated zones 
6.2.1 Excavation/Construction  YMP 1.1.02.00.00 
FEP Description: This FEP is concerned with the effects associated with 
excavation/construction of the underground regions of the repository on the long-term behavior of 
the engineered and natural barriers. Excavation-related effects include changes to rock properties 
due to boring and blasting and chemical changes to the rock and incoming groundwater due to 
potential explosives residue. Excavation and other construction activities could also directly 
cause groundwater chemistry changes within the tunnel due to the impact of such contaminants as 
diesel exhaust, explosives residues, or other organic contaminants (Secondary FEP 1.1.02.00.03). 
Finally, oxidizing water introduced into the repository during excavation/construction could 
impact repository conditions/performance (Secondary FEP 1.1.02.00.04).

ANL-WIS-PA-000002 REV 00 ICN 01 34 September 2000 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Excavation-related effects may impact both the natural and 
engineered barriers in the repository. The impact on the natural barrier (i.e., rock surrounding the 
tunnel) may be both mechanical and chemical. The mechanical effects from construction could 
impact the calculation of drift degradation/rock fall. However, this is explicitly accounted for in 
the rock properties used for these degradation analyses (see E0080 - Drift Degradation Analysis 
(CRWMS M&O 2000n)), and thus no further analysis is required. 
Any chemical effects on rock properties and/or the properties of incoming water due to residues 
deposited within the rock matrix fall within the scope of the NFE analysis and are not an issue 
relative to the EBS analysis. To the extent that incoming water properties are initially impacted by 
excavation-related effects, this would be provided to the EBS analysis from the NFE analysis via 
appropriate boundary conditions. 
Additional changes to the groundwater chemistry could occur as a result of materials 
left/deposited within the tunnel (diesel exhaust, explosives residues, residual organic 
contaminants, etc.). A detailed assessment of such groundwater chemistry changes can be found in 
CRWMS M&O 1995b. This document determines acceptable upper bounds on materials 
introduced into the repository prior to closure such that the impact of these materials has negligible 
consequences on repository performance. It is assumed that these limits will be adhered to during 
the preclosure phase of operation. 
Because the emplacement drifts are situated in the unsaturated zone of the repository, any water 
entering the drifts will be oxidizing throughout the entire history of the repository. Thus, there are 
no effects associated with influx of oxidizing water during construction/excavation that are not 
already modeled implicitly in the TSPA. 
TSPA Disposition This FEP is excluded from the TSPA (for the EBS) on the basis of 
low consequences. 
IRSR Issues: ENFE1, ENFE2, ENFE3, ENFE4, RT1 
References: E0080 (CRWMS M&O 2000n) 
6.2.2 Site Flooding (During Construction and Operation)  YMP 1.1.02.01.00 
FEP Description: Flooding of the site during construction and operation could 
introduce water into the underground tunnels, which could affect the long-term performance of the 
repository. (Note that this is a specific example of an accident or unplanned event discussed under 
FEP 1.1.12.01.00.) 
Screening Decision: Exclude

ANL-WIS-PA-000002 REV 00 ICN 01 35 September 2000 
Screening Decision Basis: Regulatory (see Section 5.1.2 for discussion) 
Screening Argument: The possibility of flooding was considered in the location of 
the entry ramps and surface buildings. As a result of this, the current design makes flooding of the 
underground areas, which would require redirection of runoff (e.g., down ramps), highly unlikely. 
In general, operational issues are outside the scope of the TSPA. Operation will be according to 
procedures acceptable to the NRC and EPA. Quality control procedures are designed to detect 
operational events resulting in deviations from the repository design that might affect long-term 
performance. Any deviation would be detected during regulator audits and inspections and be 
corrected before further work in the repository would be allowed to continue. Examples of 
accidents and unplanned events include: repository flooding, sabotage, handling damage to waste 
containers, leaks of undesirable materials, and explosions. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of regulatory 
considerations (outside the scope of the TSPA objectives). 
IRSR Issues: None 
References: Dyer 1999, 64 FR 8640, 64 FR 46976 
6.2.3 Effects of Preclosure Ventilation  YMP 1.1.02.02.00 
FEP Description The duration of preclosure ventilation acts together with waste 
package spacing (as per design) to control the extent of the boiling front within the NFE. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: The early thermal history of the repository (and associated 
water inflow) are strongly influenced by preclosure ventilation, and these in turn have a significant 
impact on EBS component performance. Thus, these are important issues relative to EBS 
performance. However, this is primarily accounted for via the NFE boundary conditions (water 
influx and temperature) provided to the EBS analysis, and thus is not strictly speaking an EBS 
analysis issue. 
TSPA Disposition: The effects of preclosure ventilation are considered in the EBS 
analysis via suitable boundary conditions (temperature, flow) from the NFE analysis. 
IRSR Issues: TEF1, TEF2, TEF3 
References: E0095 (CRWMS M&O 2000q), E0010 (CRWMS M&O 2000b), 
E0105 (CRWMS M&O 2000s)

ANL-WIS-PA-000002 REV 00 ICN 01 36 September 2000 
6.2.4 Undesirable Materials Left  YMP 1.1.02.03.00 
FEP Description: During construction and preclosure operation of the repository there 
might be possibilities for leaving unwanted material in the vicinity of the radioactive waste. These 
materials could be of different kinds and could to some extent affect many long-term processes in 
the repository from canister corrosion to transport mechanisms of radionuclides. (Note that this 
FEP has some overlap with the issues discussed under FEP 1.1.02.00.00.) 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Materials introduced during the preclosure construction and 
operation phase of the repository may, if not controlled, have a conceivably unconstrained impact 
on groundwater chemistry within the EBS, thereby impacting corrosion processes, radionuclide 
transport, etc. A detailed assessment of such groundwater chemistry changes can be found in 
CRWMS M&O 1995b. This document determines acceptable upper bounds on materials 
introduced into the repository prior to closure such that the impact of these materials has negligible 
consequences on repository performance. It is assumed that these limits will be adhered to during 
the preclosure phase of operation. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: ENFE1, ENFE2, ENFE3, ENFE4, RT1 
References: E0010 (CRWMS M&O 2000b) 
6.2.5 Error in Waste or Backfill Emplacement  YMP 1.1.03.01.00 
FEP Description: Deviations from the design and/or errors in waste and backfill 
emplacement could affect long-term performance of the repository. A specific example of such an 
error that has been raised involves erroneously emplacing the waste packages in the saturated zone 
of the repository (Secondary FEP 1.1.03.01.04). This would clearly impact the repository 
performance both by impacting container corrosion and failure as well as by impacting 
radionuclide transport. 
Screening Decision: Exclude 
Screening Decision Basis: Regulatory (see Section 5.1.2 for discussion) 
Screening Argument: Waste and backfill (should backfill be included in the 
repository design in the future) will be emplaced according to repository design. Alternative 
emplacement designs, with and without backfill have been considered, but the TSPA assumes a 
single emplacement strategy. Within this single emplacement strategy, the impact of uncertainties 
in such parameters as environmental conditions and the impact of allowable tolerances in design 
parameters is explicitly accounted for in the TSPA. Deviations beyond those considered are

ANL-WIS-PA-000002 REV 00 ICN 01 37 September 2000 
excluded on the basis of the repository quality control program. In general, the TSPA is based on 
an assumption that the repository will be constructed, operated, and closed according to design. 
Deviations from design during the operational period are the subject of an extensive quality 
control program, and are outside the scope of the long-term performance assessment. Significant 
deviations that are detected during the operational period will be corrected. Residual uncertainty 
remaining after implementation of quality control has been included in the TSPA in the 
performance of some design features (allowing, for example, for the possibility of juvenile failure 
of some waste packages). 
The specific example of waste package emplacement within the wet zone of the repository is most 
relevant to a particular design option - vertical, in-floor borehole emplacement - that is no longer 
considered. The current design involves horizontal, in-drift emplacement of very large containers 
(to 100 tonnes). Wet zones are readily detectable and thus can be avoided. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of regulatory 
considerations (beyond the scope of the TSPA objectives). 
IRSR Issues: CLST1, CLST2, ENFE1, ENFE4, TEF1, TEF2, TEF3 
References: Dyer 1999, 64 FR 8640, 64 FR 46976 
6.2.6 Repository Design  YMP 1.1.07.00.00 
FEP Description: This category contains FEPs related to the design of the repository, 
and the ways in which the design contributes to long-term performance. Changes to or deviations 
from the specified design may affect the long-term performance of the disposal system. 
Screening Decision: Include (exclude deviations from design) 
Screening Decision Basis: N/A 
Screening Argument: All aspects of the repository design are accounted for in the 
TSPA. Individual elements of this design (drip shield, pedestal, invert, ground support, etc.) are 
covered by other EBS FEPs. In general, the TSPA is based on an assumption that the repository 
will be constructed, operated, and closed according to design. Deviations from design during the 
operational period are the subject of an extensive quality control program, and are outside the 
scope of the long-term performance assessment. If the repository does not meet regulatory criteria, 
it will not be licensed and waste will not be emplaced. Significant deviations that are detected 
during the operational period will be corrected, and therefore, are excluded from the TSPA on the 
basis of regulatory considerations. 
TSPA Disposition: The TSPA is based on an assumption that the repository will be 
constructed, operated, and closed according to design. Modifications and/or deviations from the 
design are excluded on the basis of regulatory requirements (deliberate design changes) and low 
probability (significant effects from undetected deviations).

ANL-WIS-PA-000002 REV 00 ICN 01 38 September 2000 
IRSR Issues: All 
References: Dyer 1999, 64 FR 8640, 64 FR 46976 
6.2.7 Quality Control  YMP 1.1.08.00.00 
FEP Description: This category contains FEPs related to quality assurance and control 
procedures and tests during the design, construction, and operation of the repository, as well as the 
manufacture of the waste forms, containers, and engineered features. Lack of quality control could 
result in material defects, faulty waste package fabrication, and faulty or non-design-standard 
construction, all of which may lead to reduced effectiveness of the engineered barriers. 
Screening Decision: Include (exclude defects and deviations) 
Screening Decision Basis: N/A 
Screening Argument: In general, the TSPA is based on an assumption that the 
repository will be constructed, operated, and closed according to design. Deviations from design 
during the operational period are the subject of an extensive quality control program, and are 
outside the scope of the long-term performance assessment. If the repository does not meet 
regulatory criteria, it will not be licensed and waste will not be emplaced. Significant deviations 
that are detected during the operational period will be corrected, and therefore, are excluded from 
the TSPA on the basis of low probability. 
Residual uncertainty remaining after implementation of quality control has been included in the 
TSPA in the performance analysis of some design features (allowing, for example, for the 
possibility of juvenile failure of some waste packages). 
TSPA Disposition: The TSPA is based on an assumption that the repository will be 
constructed, operated, and closed according to design under an acceptable quality control plan. 
Deviations from the design due to poor quality control are excluded on the basis of regulatory 
requirements (deliberate design changes) and low probability (significant effects from undetected 
deviations). Material defects are included only in juvenile failures of containers. 
IRSR Issues: All 
References: Dyer 1999, 64 FR 8640, 64 FR 46976 
6.2.8 Accidents and Unplanned Events During Operation  YMP 1.1.12.01.00 
FEP Description: The long-term performance of the disposal system might be 
seriously affected by unplanned or improper activities that take place during construction, 
operation, and closure of the repository.

ANL-WIS-PA-000002 REV 00 ICN 01 39 September 2000 
Screening Decision: Exclude 
Screening Decision Basis: Regulatory (see Section 5.1.2 for discussion) 
Screening Argument: In general, operational issues are outside the scope of the 
TSPA. Operation will be according to procedures acceptable to the NRC and EPA. Quality 
control procedures are designed to detect operational events resulting in deviations from the 
repository design that might affect long-term performance. Any deviation would be detected 
during regulator audits and inspections and would be corrected before further work in the 
repository would be allowed to continue. Examples of accidents and unplanned events include: 
repository flooding, sabotage, handling damage to waste containers, leaks of undesirable 
materials, and explosions. 
For the purposes of the TSPA, the effects of these types of events are assumed to be corrected 
before closure. Therefore, accidents and unplanned events during the operational phase that could 
have a significant effect on long-term performance and that remain undetected at the time of closure 
are excluded from the TSPA on the basis of regulatory considerations. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of regulatory 
considerations (outside the scope of the TSPA objectives). 
IRSR Issues: None 
References: Dyer 1999, 64 FR 8640, 64 FR 46976 
6.2.9 Retrievability  YMP 1.1.13.00.00 
FEP Description: This category contains FEPs related to design, emplacement, 
operational, or administrative measures that might be applied or considered in order to enable or 
ease retrieval of wastes. There may be a requirement to retrieve all or part of the waste stored in 
the repository (e.g., to recover valuable fissile materials or to replace defective containers). 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: This FEP is explicitly considered in the design requirements 
for the repository. Regulation requires that the repository be designed in such a way that removing 
the waste is not precluded for a reasonable period of time after emplacement. Current DOE policy 
allows for the possibility of keeping the repository open at least 100 years after the initiation of 
emplacement, with a reasonable expectation that the repository could, with appropriate 
maintenance, be kept open for up to 300 years after the initiation of waste emplacement. Aspects 
of the repository design related to waste retrievability (such as the design of the drifts and 
emplacement of the waste packages) are included in the repository design that is used as the basis 
for the TSPA modeling. 
TSPA Disposition: Retrievability is implicitly considered in all phases of the TSPA

ANL-WIS-PA-000002 REV 00 ICN 01 40 September 2000 
through the repository design parameters. 
IRSR Issues: All 
References: CRWMS M&O 2000ii 
6.2.10 Igneous Intrusion Into Repository  YMP 1.2.04.03.00 
FEP Description: Magma from an igneous intrusion may flow into the drifts and extend 
over a portion of the repository site, forming a sill. The sill could be limited to the drifts or a 
continuous sill could form along the plane of the repository, bridging between adjacent drifts. 
Note that this FEP also encompasses FEP ebs # 36 from table 3. 
Screening Decision: Exclude (for EBS) 
Screening Decision Basis: N/A for EBS 
Screening Argument: The impact of an igneous intrusion into the repository is significant 
in that it changes the fundamental response of the EBS. For this reason, this FEP is not considered 
as part of the EBS analyses, but rather is considered as part of a stand-alone tectonics analysis 
documented in CRWMS M&O 2000z. 
TSPA Disposition: This FEP is not considered as part of the EBS analysis. 
IRSR Issues: IA1, IA2 
References: CRWMS M&O 2000z 
6.2.11 Corrosion of Waste Containers  YMP 2.1.03.01.00 
FEP Description: Corrosion may contribute to waste package failure. Corrosion is 
most likely to occur at locations where water drips on the waste packages, but other mechanisms 
should be considered. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: The time-dependent water distribution and the chemistry of 
this water relative to waste package corrosion are important parameters relative to repository 
performance. Special consideration of anoxic corrosion (FEP 2.1.03.01.04) can be excluded from 
the TSPA on the basis of low probability, because for a repository located in the unsaturated zone, 
the connection to the atmosphere ensures an oxidizing environment at all times. 
TSPA Disposition: The TSPA corrosion model considers general corrosion, pitting,

ANL-WIS-PA-000002 REV 00 ICN 01 41 September 2000 
and stress corrosion cracking in both wet and dry environments for the drip shield and waste 
package materials. The treatment of these phenomena is part of the WP analysis effort, and a 
discussion of their treatment may be found in the FEPs summary discussion for WP documented in 
CRWMS M&O 2000dd. The EBS analysis provides two key sets of parameters to the WP 
analysis; the time-dependent rate of water contact with both drip shield and waste package (as 
described in E0095 (CRWMS M&O 2000q)), and the chemistry of this water (as described in 
E0010 (CRWMS M&O 2000b)). 
IRSR Issues: CLST1, ENFE2 
References: E0095 (CRWMS M&O 2000q), E0010 (CRWMS M&O 2000b), 
CRWMS M&O 2000dd 
6.2.12 Container Healing  YMP 2.1.03.10.00 
FEP Description: Pits and holes in waste packages could be partially or fully plugged 
by chemical or physical reactions during or after their formation, affecting corrosion processes and 
water flow and radionuclide transport through the breached container. Passivation by corrosion 
products is a potential mechanism for container healing. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Container healing is not considered by itself. Rather, container 
failure and breach (when liquids can leave a container) are described by a distribution function for 
analyses (CRWMS M&O 2000ff). 
TSPA Disposition: For purposes of the EBS response analysis, the timing of waste 
package failure is provided by the results of the WP analysis (CRWMS M&O 2000cc), as input 
into the EBS radionuclide transport abstraction, E0095 (CRWMS M&O 2000q). While the 
potential for container healing is inherently a WP analysis issue (see WP FEPs discussion 
(CRWMS M&O 2000dd)), the EBS analysis does provide to the WP analysis the chemistry of the 
groundwater contacting both the drip shield and waste package. This is discussed in the EBS 
physical and chemical environmental abstraction, E0010 (CRWMS M&O 2000b). 
IRSR Issues: CLST1, ENFE2, RT1 
References: E0010 (CRWMS M&O 2000b), E0095 (CRWMS M&O 2000q), 
CRWMS M&O 2000cc, CRWMS M&O 2000dd 
6.2.13 Container Failure (Long-term)  YMP 2.1.03.12.00 
FEP Description Waste packages and drip shields have a potential to fail over long 
periods of time by a variety of mechanisms, including general corrosion, stress corrosion cracking, 
pit corrosion, hydride cracking, microbially-mediated corrosion, internal corrosion, and

ANL-WIS-PA-000002 REV 00 ICN 01 42 September 2000 
mechanical impacts. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Long-term failure of the WPs and drip shields must be 
accounted for in TSPA analyses as this defines the timing of radionuclide release and transport. 
TSPA Disposition: WP and drip shield failure is calculated explicitly as part of the 
waste package analysis (CRWMS M&O 2000cc). A discussion of these issues relative to the WP 
analysis may be found in the WP FEPs (CRWMS M&O 2000dd). The EBS TSPA models provide 
critical inputs for that analysis including the timing of water contact as discussed in E0095 
(CRWMS M&P 2000q), the chemistry of the water as discussed in E0010 (CRWMS M&O 
2000b), and the timing and impact of rock-fall as discussed in E0080 (CRWMS M&O 2000n). 
Note that the properties of the failed containers relative to their impact on EBS performance are 
addressed as part of FEP 2.1.08.07.00, and the chemical buffering effects of the failed containers 
are addressed as part of FEP 2.1.09.02.00. 
IRSR Issues: CLST1, CLST2 
References: E0010 (CRWMS M&O 2000b), E0095 (CRWMS M&O 2000q), 
E0080 (CRWMS M&O 2000n), CRWMS M&O 2000cc, CRWMS 
M&O 2000dd 
6.2.14 Preferential Pathways in the Backfill  YMP 2.1.04.01.00 
FEP Description: Preferential pathways for flow and diffusion may exist within the 
backfill and may affect long-term performance of the waste packages. Backfill may not preclude 
hydrological, chemical, and thermal interactions between waste packages within a drift. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: There is no backfill used in the design baseline (CRWMS 
M&O 2000ii) at Yucca Mountain, thus there is less than one chance in 10,000 in 10,000 years that 
this FEP will occur. 
Should backfill be included in the repository design in the future, it would represent a preferential 
pathway for seepage into the drift because it tends to funnel fluid into the emplacement drift due to 
its capillarity. This has an important impact on water contact with the drip shield and the resulting 
corrosion. In addition, the potentially high water content of the backfill impacts the in-drift 
thermal response due to waste package heat generation. 
The effect of the backfill on water transport within the drift would have to be accounted for in the 
EBS radionuclide transport abstraction, E0095 (CRWMS M&O 2000q). Most notably, this 
would need to consider the capillary effects of the backfill as a mechanism for enhanced water

ANL-WIS-PA-000002 REV 00 ICN 01 43 September 2000 
transport to the drip shield. 
Note that this FEP also encompasses FEPs ebs # 5 and 18 from table 3. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low probability 
(not relevant to the YMP design). 
IRSR Issues: ENFE1, ENFE2, ENFE3, ENFE4, RT1 
References: E0095 (CRWMS M&O 2000q), CRWMS M&O 2000ii 
6.2.15 Physical and Chemical Properties of Backfill  YMP 2.1.04.02.00 
FEP Description: The physical and chemical properties of the backfill may affect 
groundwater flow, waste package and drip shield durability, and radionuclide transport in the 
waste disposal region. 
Note that this FEP also encompasses FEP ebs # 5 from table 3. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: There is no backfill used in the design baseline (CRWMS 
M&O 2000ii) at Yucca Mountain, thus there is less than one chance in 10,000 in 10,000 years that 
this FEP will occur. 
Should backfill be included in the repository design in the future, the properties of the backfill 
would have a significant effect on the transport of water to the drip shield, and hence must be 
considered explicitly in the TSPA. 
The porosity and permeability of the quartz sand backfill (and crushed tuff in the invert) would 
need to be represented in the thermal/hydrological response of the WPs and drip shields in the 
emplacement drifts as discussed in E0120 (CRWMS M&O 2000t). These calculations define the 
fluid flux due to capillarity (if it exists), the temperature and relative humidity at the WP, and the 
potential for condensation on the underside of the drip shield due to evaporation from the invert. 
The effects of the chemical properties of the sand backfill and the crushed tuff on transport would 
be ignored in the TSPA analyses because of two conservative assumptions that would be made: 
(1) there is no sorption in the invert and in the sand backfill, and (2) chemical changes to the 
backfill seem likely to divert seepage away from the WP. The chemical properties of the backfill 
would, however, need to be considered in the analysis of seepage/backfill chemical interactions as 
discussed in E0030 (CRWMS M&O 2000d) and E0010 (CRWMS M&O 2000b). 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low probability 
(not relevant to the YMP design). 
IRSR Issues: ENFE1, ENFE2, ENFE3, ENFE4, RT1 
References: E0010 (CRWMS M&O 2000b), E0030 (CRWMS M&O 2000d), 
E0120 (CRWMS M&O 2000t), E0095 (CRWMS M&O 2000q),

ANL-WIS-PA-000002 REV 00 ICN 01 44 September 2000 
CRWMS M&O 2000ii 
6.2.16 Erosion or Dissolution of Backfill  YMP 2.1.04.03.00 
FEP Description: Solid material in buffer or backfill is carried away by flowing 
groundwater, either by erosion of particulate matter or by dissolution. 
Note that this FEP also encompasses FEP ebs # 5 from table 3. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: There is no backfill used in the design baseline (CRWMS M&O 
2000ii) at Yucca Mountain, thus there is less than one chance in 10,000 in 10,000 years that this 
FEP will occur. 
Should backfill be included in the repository design in the future, the material likely to be used is 
quartz sand. Thus, it will not be highly soluble and no significant loss due to dissolution is 
anticipated. Furthermore, flow rates in the unsaturated environment of the repository will be too 
low to cause significant erosion. Any limited erosion that does occur would be expected to have 
negligible impact on repository performance. Wicking of water to the drip shield surface would 
be unimpacted by a slight reduction in backfill volume. Further, the degree of backfill erosion 
would not be expected to be significant enough to reduce drip shield protection from rock fall. 
Thus, even with backfill included in the design, this FEP would be excluded on the basis of low 
consequences. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
probability (not relevant to the YMP design). 
IRSR Issues: ENFE1, ENFE2, ENFE3, ENFE4, RT1 
References: E0030 (CRWMS M&O 2000d), CRWMS M&O 2000ii 
6.2.17 Mechanical Effects of Backfill  YMP 2.1.04.04.00 
FEP Description: Backfill may alter the mechanical evolution of the drift environment 
by providing resistance to rock creep and rock fall, by changing the thermal properties of the drift, 
or by other means. Impacts of the evolution of the properties of the backfill itself should be 
considered. 
Note that this FEP also encompasses FEP ebs # 5 from table 3. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: There is no backfill used in the design baseline (CRWMS 
M&O

ANL-WIS-PA-000002 REV 00 ICN 01 45 September 2000 
2000ii) at Yucca Mountain, thus there is less than one chance in 10,000 in 10,000 years that this 
FEP will occur. 
Should backfill be included in the repository design in the future, it would be a key component of 
the EBS and as such must be explicitly accounted for in the TSPA. The presence of the backfill 
would need to be explicitly included in estimating the mechanical response of the drip shield to 
rockfall by distributing the load from a rockfall over a larger area of the drip shield. It would 
also need to be included in evaluating the waste package environment because the backfill would 
be assumed to fall through any penetrations through the drip shield and form a continuous fluid path 
between the backfill and the waste package. Finally, in addition to the direct impacts delineated 
above, the backfill also influences the thermal response of the repository, which in turn can 
influence the character of rock fall. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
probability (not relevant to the YMP design). 
IRSR Issues: CLST2, CLST6 
References: E0080 (CRWMS M&O 2000n), CRWMS M&O 2000ii 
6.2.18 Backfill Evolution - YMP 2.1.04.05.00 
FEP Description: Properties of the backfill may change through time, due to processes 
such as silica cementation, alteration of minerals, thermal effects, and physical compaction. These 
changes could then affect the movement of water and radionuclides in the backfill. 
Note that this FEP also encompasses FEP ebs # 5 from table 3. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: There is no backfill used in the design baseline (CRWMS M&O 
2000ii) at Yucca Mountain, thus there is less than one chance in 10,000 in 10,000 years that this 
FEP will occur. 
Should backfill be included in the repository design in the future, the evolution of backfill 
properties would potentially need to be considered. However, as discussed below, the neglect of 
such changes in the current TSPA would be conservative relative to water transport to the waste 
packages and thus radionuclide transport to the unsaturated zone (UZ). 
Backfill affects the performance of the drip shields and WPs in two ways: It acts to mitigate the 
impact of rock fall, and it serves to create a uniform water distribution via wicking of water 
through this material. While localized cementation of the backfill material would not be 
expected for the temperatures in the EBS, even if such localized agglomeration did occur, it 
would have an insignificant impact on repository performance. Mitigation of rockfall impacts 
would still occur. In addition, such localized cementation could only serve to reduce the rate of 
water transport to the drip shield surface. Thus, excluding such an effect would be conservative.

ANL-WIS-PA-000002 REV 00 ICN 01 46 September 2000 
The same argument holds for the formation of a low permeability rind on the top of the backfill. 
Such a rind will tend to divert seepage from the drip shield and WP, and thus it is conservative to 
neglect this effect. Thus, the physical properties (porosity, permeability) of the backfill could be 
assumed to remain constant over time in the EBS radionuclide transport abstraction, E0095 
(CRWMS M&O 2000q). Detailed chemical studies are evaluating the geochemical environment 
during the first few thousand years, when the backfill will be very hot and evaporation will 
generate strong ionic solutions and precipitated salts in the backfill or on the drip shield. The 
chemical processes in the backfill would need to be assessed in the seepage/backfill interaction 
analysis, E0030 (CRWMS M&O 2000d) in support of E0010 (CRWMS M&O 2000b). 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
probability (not relevant to the YMP design). 
IRSR Issues: CLST2, ENFE1, ENFE2, ENFE3, ENFE4, RT1 
References: E0010 (CRWMS M&O 2000b), E0030 (CRWMS M&O 2000d), 
E0095 (CRWMS M&O 2000q), CRWMS M&O 2000ii 
6.2.19 Properties of Bentonite  YMP 2.1.04.06.00 
FEP Description: This category contains FEPs specific to the properties of bentonite 
buffers. Because the Yucca Mountain design does not include bentonite backfill, all FEPs in this 
category are irrelevant to the YMP TSPA. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: Bentonite is not part of the design baseline (CRWMS M&O 
2000ii) for Yucca Mountain, thus there is less than one chance in 10,000 in 10,000 years that 
this FEP will occur. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
probability (not relevant to YMP design). 
IRSR Issues: None 
References: CRWMS M&O 2000ii 
6.2.20 Buffer Characteristics  YMP 2.1.04.07.00 
FEP Description: This category contains FEPs specific to repository designs that 
include chemical buffering agents in the waste disposal region. The Yucca Mountain design does 
not include buffering agents, and all FEPs in this category are irrelevant to the YMP TSPA. 
Screening Decision: Exclude

ANL-WIS-PA-000002 REV 00 ICN 01 47 September 2000 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: There is no buffer used in the design baseline (CRWMS M&O 
2000ii) at Yucca Mountain, thus there is less than one chance in 10,000 in 10,000 years that this 
FEP will occur. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
probability (not relevant to YMP design). 
IRSR Issues: None 
References: CRWMS M&O 2000ii 
6.2.21 Diffusion in Backfill  YMP 2.1.04.08.00 
FEP Description: Diffusion processes in backfill may affect waste package 
performance and radionuclide transport. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: There is no backfill used in the design baseline (CRWMS M&O 
2000ii) at Yucca Mountain, thus there is less than one chance in 10,000 in 10,000 years that this 
FEP will occur. 
Should backfill be included in the repository design in the future, diffusion in backfill could still 
be excluded from the TSPA on the basis of low consequence. The quartz sand backfill is upstream 
of the waste package from a flow viewpoint. In this situation, radionuclides can only reach the 
backfill when the downward advective flux through the drip shield is negligible and when there is 
a continuous fluid pathway that allows upward diffusion across the gap between drip shield and 
waste package. When the drip shield is intact there is no flow path. When the drip shield has been 
breached there will be a flow path (through backfill sitting on the waste package); however, 
upward diffusion will be negligible in comparison to downward advection. Diffusion through the 
backfill could therefore still be screened out for the TSPA analyses. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
probability (not relevant to YMP design). 
IRSR Issues: ENFE1, RT1 
References: E0095 (CRWMS M&O 2000q), CRWMS M&O 2000ii 
6.2.22 Radionuclide Transport Through Backfill  YMP 2.1.04.09.00 
FEP Description: Radionuclide transport in the drift environment may be affected by 
the presence of backfill. Transport of both dissolved and colloidal species, advective and 
diffusive effects and sorption processes should be considered.

ANL-WIS-PA-000002 REV 00 ICN 01 48 September 2000 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: There is no backfill used in the design baseline (CRWMS M&O 
2000ii) at Yucca Mountain, thus there is less than one chance in 10,000 in 10,000 years that this 
FEP will occur. 
Should backfill be included in the repository design in the future, radionuclide transport in backfill 
could be excluded from the TSPA on the basis of low consequence. The quartz sand backfill is 
upstream of the waste package from a flow viewpoint. In this situation, radionuclides can only 
reach the backfill when the downward advective flux through the drip shield is negligible and 
when there is a continuous fluid pathway that allows upward diffusion across the gap between drip 
shield and waste package. When the drip shield is intact there is no flow path. When the drip 
shield has been breached there will be a flow path (through backfill sitting on the waste package); 
however, upward diffusion would be negligible in comparison to downward advection and 
transport. Radionuclide transport through the backfill could therefore be screened out for the 
TSPA analyses. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
probability (not relevant to YMP design). 
IRSR Issues: ENFE1, ENFE4, RT1 
References: E0095 (CRWMS M&O 2000q), CRWMS M&O 2000ii 
6.2.23 Degradation of Cementitious Materials in Drift  YMP 2.1.06.01.00 
FEP Description: Degradation of cementitious material used for any purposes in the 
disposal region may affect long-term performance through both chemical and physical processes. 
Degradation may occur by physical, chemical, and microbial processes. 
Note that this FEP also encompasses FEPs ebs # 22 and 26 from table 3. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Degradation of cementitious materials has an impact on water 
chemistry, and thus must be considered in the TSPA. 
TSPA Disposition: The effects of the degradation of cementitious material in the driftstabilization 
structures are analyzed in the cement seepage interactions analysis, E0055 (CRWMS 
M&O 2000i), supporting E0010 (CRWMS M&O 2000b). The specific chemical concerns 
associated with cementitious materials are further discussed in FEP 2.1.09.01.00. 
IRSR Issues: CLST1, ENFE1, ENFE2, ENFE3, ENFE4, RT1 
References: E0010 (CRWMS M&O 2000b), E0055 (CRWMS M&O 2000i)

ANL-WIS-PA-000002 REV 00 ICN 01 49 September 2000 
6.2.24 Effects of Rock Reinforcement Materials  YMP 2.1.06.02.00 
FEP Description: Degradation of rock bolts, wire mesh, and other materials used in 
ground control may affect the long-term performance of the repository. 
Note that this FEP also encompasses FEPs ebs # 12, 21, 22, and 26 from table 3. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Degradation of ground control materials has two potentially 
important effects on repository performance that must be considered in the TSPA; the impact on 
drift stability/degradation and the impact on water chemistry due to evolved corrosion products. 
TSPA Disposition: The effect of ground control devices (rock bolts and wire mesh) and 
their associated degradation is considered explicitly in the drift degradation analysis, E0080 
(CRWMS M&O 2000n). The effects of the corrosion products due to the degradation of metal 
reinforcing components in the drift-stabilization structures are analyzed in the corrosion products 
analysis, E0020 (CRWMS M&O 1999c), supporting E0010 (CRWMS M&O 2000b). 
IRSR Issues: CLST1, CLST2, ENFE1, ENFE2, ENFE3, ENFE4, RT1 
References: E0010 (CRWMS M&O 2000b), E0020 (CRWMS M&O 1999c), 
E0080 (CRWMS M&O 2000n) 
6.2.25 Degradation of the Liner  YMP 2.1.06.03.00 
FEP Description Degradation of materials used to line the drifts may occur by 
physical, chemical, or microbial processes, and may affect long-term performance. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: No liner is planned for the repository (other than the steel mesh for 
ground support) (CRWMS M&O 2000ii). Thus, there is less than one chance in 10,000 in 10,000 
years that this FEP will occur. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
probability (not relevant to YMP design). 
IRSR Issues: None 
References: CRWMS M&O 2000ii

ANL-WIS-PA-000002 REV 00 ICN 01 50 September 2000 
6.2.26 Flow Through the Liner  YMP 2.1.06.04.00 
FEP Description: Groundwater flow may occur through the liner. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: No liner is planned for the repository (other than the steel mesh for 
ground support) (CRWMS M&O 2000ii). Thus, there is less than one chance in 10,000 in 10,000 
years that this FEP will occur. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low probability 
(not relevant to YMP design). 
IRSR Issues: None 
References: CRWMS M&O 2000ii 
6.2.27 Degradation of Invert and Pedestal  YMP 2.1.06.05.00 
FEP Description: Degradation of the materials used in the invert and the pedestal 
supporting the waste package may occur by physical, chemical, or microbial processes, and may 
affect the long-term performance of the repository. 
Note that this FEP also encompasses FEPs ebs # 1, 5, 8, 9, and 11 from table 3. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Physical degradation of the invert and invert materials has been 
screened out of the TSPA on low consequence. The invert is a minor barrier to flow in 
comparison to the drip shield, waste package, and unsaturated zone beneath the drift. Minor 
changes in the physical properties of the invert will have negligible impact on system performance. 
As such, the invert is assumed to provide no resistance to flow in the EBS radionuclide transport 
abstraction, E0095 (CRWMS M&O 2000q). 
Physical degradation of the pedestal is an important process because (1) the waste package will be 
in direct contact with the invert after the pedestal collapses, and (2) the waste package may roll off 
a degraded invert and impact the drip shield during a seismic event. 
TSPA Disposition: To account for potential pedestal failure, the radionuclide transport 
abstraction for the EBS, E0095 (CRWMS M&O 2000q) conservatively assumes that the waste 
package is in direct contact with the invert at all times. The TSPA model for drip shield 
separation demonstrates that the impact from pedestal failure and contact between waste package 
and drip shield is incorporated in the large uncertainty in the seismic displacement model for the 
drip shield. The effects of pedestal degradation products on seepage water chemistry are

ANL-WIS-PA-000002 REV 00 ICN 01 51 September 2000 
analyzed explicitly in the TSPA as discussed in the In Drift Corrosion Products AMR, E0020 
(CRWMS M&O 1999c), supporting E0010 (CRWMS M&O 2000b). 
IRSR Issues: CLST2, ENFE1, RT1, RDTME1, RDTME2, RDTME3 
References: E0010 (CRWMS M&O 2000b), E0020 (CRWMS M&O 1999c), 
E0095 (CRWMS M&O 2000q) 
6.2.28 Effects and Degradation of Drip Shield  YMP 2.1.06.06.00 
FEP Description: The drip shield will affect the amount of water reaching the waste 
package. Behavior of the drip shield in response to rockfall, ground motion, and physical, 
chemical degradation processes should be considered. Effects of the drip shield on the disposal 
region environment (for example, changes in relative humidity and temperature below the shield) 
should be considered for both intact and degraded conditions. Degradation processes specific to 
the chosen material should be identified and considered. For example, oxygen embrittlement 
should be considered for titanium drip shields. 
Note that this FEP also encompasses FEPs ebs # 2, 9, 10, 11, 15, 17, 19, 20, 24, 30, 31, and 32 
from table 3. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: The drip shield is an important element of the EBS, and as such its 
as-designed function and degradation must be explicitly considered in the TSPA. Certain aspects 
of this functionality (degradation of the drip shield due to chemical processes) are considered 
directly in the WP analysis (see WP FEPs summary (CRWMS M&O 2000dd). However, the 
remaining aspects of drip shield behavior are considered as part of the EBS analysis. 
TSPA Disposition: The EBS radionuclide transport abstraction, E0095 (CRWMS M&O 
2000q) explicitly considers the impact of the drip shield on flow. Prior to drip shield failure, no 
direct pathway for water flow to the waste package exists. However, the potential for 
condensation of water on the underside of the drip shield and the subsequent dripping of this 
condensate on the waste packages is considered. Failure of the drip shield is provided via the WP 
analysis outputs (CRWMS M&O 2000cc) for chemically-induced failures or is explicitly 
considered as part of the EBS analysis for drift shield separation due to seismic events (CRWMS 
M&O 2000q). Subsequent to the calculation of such failures, fluid can reach the waste packages 
directly. For chemically-induced failures (corrosion), the EBS analysis provides directly the 
chemical environment on these structural surfaces (CRWMS M&O 2000ee), which has a key 
influence on the rate of such corrosion. The effects of the corrosion products associated with drip 
shield degradation on seepage water chemistry are analyzed as part of the In Drift Corrosion 
Products AMR, E0020 (CRWMS M&O 1999c), supporting E0010 (CRWMS M&O 2000b). 
IRSR Issues: CLST1, CLST2, ENFE2, RT1, SDS

ANL-WIS-PA-000002 REV 00 ICN 01 52 September 2000 
References: E0010 (CRWMS M&O 2000b), E0020 (CRWMS M&O 1999c), 
E0095 (CRWMS M&O 2000q), CRWMS M&O 2000cc, CRWMS 
M&O 2000dd, CRWMS M&O 2000ee 
6.2.29 Effects at Material Interfaces  YMP 2.1.06.07.00 
FEP Description: Physical and chemical effects that occur at the interfaces between 
materials in the drift, such as at the contact between the backfill and the drip shield, may affect the 
performance of the system. 
Note that this FEP also encompasses FEPs ebs # 9 and 11 from table 3. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: The basic chemical processes that occur at phase boundaries 
(principally liquid/solid) are included in the geochemical modeling supporting E0010 (CRWMS 
M&O 2000b) and its associated submodel AMRs. Solid/solid contact either does occur or could 
occur between the drip shield and the invert and/or backfill (if included in the YMP design), 
between the waste package and the invert and/or backfill (if included in the YMP design); between 
the pedestal and the waste package and/or drip shield; and between the waste form and any of the 
other EBS component materials. Since these materials are all relatively inert, no solid/solid 
interaction mechanisms have been identified that are significant relative to the basic seepage water 
induced corrosion of the EBS components. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0095 (CRWMS M&O 2000q) 
6.2.30 Rockfall (Large Block)  YMP 2.1.07.01.00 
FEP Description: Rockfalls may occur that are large enough to mechanically tear or 
rupture waste packages. 
Note that this FEP also encompasses FEPs ebs # 6, 9, and 11 from table 3. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Large-block rockfall is a possibility in the drifts. Such 
blocks could be loosed during the thermal period when thermal expansion causes considerable 
compressive forces and reorientation of the least principal stress. However, such rockfall is

ANL-WIS-PA-000002 REV 00 ICN 01 53 September 2000 
excluded from the TSPA based on low consequences. An analysis of the possible formation of key 
blocks within the repository horizon has been provided in the Drift Degradation Analysis AMR, 
E0080 (CRWMS M&O 2000n). Block failure due to seismic and thermal effects has also been 
analyzed in that document. 
Based on these results for expected rockfall source terms, an analysis of the waste packages 
(CRWMS M&O 2000jj, CRWMS M&O 2000kk, CRWMS M&O 2000ll) and drip shields 
(CRWMS M&Omm) has been performed to develop a design capable of surviving the impacts of 
rockfall. Thus, because the design of both the waste packages and drip shield is required to meet 
the expected rock fall threat, the consequences of rockfall can be excluded on the basis of low 
consequences. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: CLST2, RDTME, SDS 
References: E0080 (CRWMS M&O 2000n), CRWMS M&O 1999b, 
CRWMS M&O 2000jj, CRWMS M&O 2000kk, 
CRWMS M&O 2000ll, CRWMS M&O 2000mm 
6.2.31 Mechanical Degradation or Collapse of Drift  YMP 2.1.07.02.00 
FEP Description: Partial or complete collapse of the drifts, as opposed to discrete 
rockfall, could occur as a result of seismic activity, thermal effects, stresses related to excavation, 
or possibly other mechanisms. Drift collapse could affect stability of the engineered barriers and 
waste packages. Drift collapse may be localized as stopping at faults or other geologic features. 
Rockfall of small blocks may produce rubble throughout part or all of the tunnel. 
Note that this FEP also encompasses FEPs ebs # 9, 11, and 37 from table 3. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Changing stress state, either from fault (tectonic) adjustment 
or from seismic waves arriving from distal sources, produces rockfall and liner failure. Such 
displacement of surrounding rocks into the tunnels and attendant growth of the tunnel (possibly 
by chimneying) is categorized as tunnel failure. A distinction is made between the thermal and 
post-thermal states because the thermally induced compression around the drifts is expected to 
require higher ground accelerations in order to induce tunnel failure than for the post-thermal 
relaxing environment. However, such mechanical degradation or collapse of the drift is excluded 
from the TSPA based on low consequences. It is unlikely that drift degradation could penetrate 
the designed engineered barriers and impact a waste package. A detailed analysis of drift 
degradation is provided in E0080 (CRWMS M&O 2000n). That analysis provides a time history 
of expected rockfall due to ongoing degradation of the drift as well due to a 10,000 year 
seismic event. That analysis further demonstrates that a mechanical threat to the drip shield and

ANL-WIS-PA-000002 REV 00 ICN 01 54 September 2000 
waste package beyond that considered in the drip shield CRWMS M&O 2000mm) and waste 
package (CRWMS M&O 2000jj, CRWMS M&O 2000kk, CRWMS M&O 2000ll) design analyses 
does not occur. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: CLST2, RDTME, SDS 
References: E0080 (CRWMS M&O 2000n), CRWMS M&O 1999b, 
CRWMS M&O 2000jj, CRWMS M&O 2000kk, 
CRWMS M&O 2000ll, CRWMS M&O 2000mm 
6.2.32 Movement of Containers  YMP 2.1.07.03.00 
FEP Description: Waste packages may move as a result of seismic activity, 
degradation of the invert or pedestal, rockfall, fault displacement, or other processes (See also 
FEP 2.1.06.05.00 - Degradation of Invert and Pedestal.) 
Note that this FEP also encompasses FEP ebs # 3 from table 3. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Movement of the waste packages is potentially important because 
it can result in direct contact between the waste package and the invert (and thus, to additional 
contact with water if the invert is wet). In addition, movement of the waste packages against the 
drip shield can result in drip shield separation. 
TSPA Disposition: The mechanisms of rockfall, floor heave, and thermal expansion 
have been screened out of the TSPA as causing drip shield separation because of low 
consequence (see E0095 (CRWMS M&O 2000q)). The mechanism of seismic response has 
been retained in the TSPA through the drip shield separation model. The mechanism of pedestal 
failure has also been retained because it is assumed to be included in the bounding model for 
seismic response. The radionuclide transport abstraction for the EBS (as documented in E0095 
(CRWMS M&O 2000q)) conservatively ignores the pedestal and assumes that the waste package 
is in direct contact with the invert at all times. Thus, any accelerated corrosion due to the 
presence of saturated water in the invert would be automatically accounted for. 
The abstraction for drip shield separation (as documented in E0095 (CRWMS M&O 2000q)) 
screens out container movement against the drip shield as a significant contributor to drip shield 
separation. It is argued therein that the consequences of contact between waste package and drip 
shield from pedestal failure are accounted for in the large uncertainty that is considered in the 
seismic displacement model for the drip shield. 
IRSR Issues: CLST1, CLST2, RDTME, SDS

ANL-WIS-PA-000002 REV 00 ICN 01 55 September 2000 
References: E0095 (CRWMS M&O 2000q) 
6.2.33 Hydrostatic Pressure on Container  YMP 2.1.07.04.00 
FEP Description: Waste packages emplaced in the saturated zone will be subjected to 
hydrostatic pressure in addition to stresses associated with the evolution of the waste and barrier 
system. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: A repository at Yucca Mountain locates waste above the water 
table in a fractured, porous medium. Thus, the pressure is approximately atmospheric. 
Consequently, this FEP is not relevant for the YMP design, which calls for emplacement in the 
unsaturated zone, and there is less than one chance in 10,000 in 10,000 years that this FEP will 
occur. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low probability 
(not relevant to YMP design). 
IRSR Issues: CLST2 
References: None 
6.2.34 Creeping of Metallic Materials in the EBS  YMP 2.1.07.05.00 
FEP Description: Metals used in the waste package or drip shield may deform by 
creep processes in response to deviatoric stress. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: The size of the containers is such that creep, as a response to 
pressurization or external damage or manufacturing stress, is a second order process compared to 
corrosion and is simply subsumed in its description. Temperatures in the drift will not exceed 
creep temperature of 350 degrees C (CRWMS M&O 2000k). Any potential uncertainty associated 
with this phenomenon is covered by the uncertainty analysis done for the WP and drip shield 
failure analysis (CRWMS M&O 2000ff). 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of negligible 
consequences. 
IRSR Issues: CLST2 
References: CRWMS M&O 2000ff, CRWMS M&O 2000k

ANL-WIS-PA-000002 REV 00 ICN 01 56 September 2000 
6.2.35 Floor Buckling  YMP 2.1.07.06.00 
FEP Description: Buckling, or heave, of the drift floor occurs in response to 
changing stress. Floor buckling may affect the performance of components of the EBS such as 
the drip shield, the invert, and the pedestal. Effects may include movement of EBS components, 
and changes in the topography of the surface of the drift floor and invert that may affect water 
flow. 
Note that this FEP also encompasses FEP ebs # 35 from table 3. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: The effect of floor heave and buckling on drip shield response has 
been screened out of the TSPA because of low consequence. Calculations documented in E0095 
(CRWMS M&O 2000q) demonstrated that the vertical displacement of the floor due to in situ 
stress and thermal response will be on the order of 10 mm. This displacement will produce only 
minor shifting in the drip shields and will not compromise their integrity because the overlap 
between adjacent drip shields is much larger, between 200 mm and 600 mm. The effect of floor 
heave on position of the waste packages is also minor. A displacement of 10 millimeters at one 
end of a 5000 millimeter long package results in an angle of inclination of less than one degree. 
The impacts of floor heave and buckling have therefore been screened out of the TSPA. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of negligible 
consequences. 
IRSR Issues: RDTME3 
References: E0095 (CRWMS M&O 2000q) 
6.2.36 Increased Unsaturated Water Flux at the Repository  YMP 2.1.08.01.00 
FEP Description: An increase in the unsaturated water flux at the repository affects 
thermal, hydrological, chemical, and mechanical behavior of the system. Extremely rapid influx 
could reduce temperatures below the boiling point during part or all of the thermal period. 
Increases in flux could result from climate change, but the cause of the increase is not an essential 
part of the FEP. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Climate is expected to change. As a surrogate for that 
change, three climate states with different infiltration fluxes have been considered in TSPA 
modeling

ANL-WIS-PA-000002 REV 00 ICN 01 57 September 2000 
TSPA Disposition: This is implicitly included in the EBS modeling through the water 
influx time histories as provided from the NFE analysis (CRWMS M&O 2000aa). 
IRSR Issues: None for EBS 
References: CRWMS M&O 2000aa 
6.2.37 Enhanced Influx (Philip's drip)  YMP 2.1.08.02.00 
FEP Description: An opening in unsaturated rock alters the hydraulic potential, 
affecting local saturation around the opening and redirecting flow. Some of the flow is directed 
to the opening where it is available to seep into the opening. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Philips drip is a consequence of a drift of a certain dimension and 
shape intercepting a homogeneous, isotropic phreatic zone in such a way that it produces 
saturated conditions at the crown of the drift. This type of flow is esoteric, has been derived 
analytically, but is not currently supported experimentally. It is also not expected to compete in 
volume with drip from infiltrate or condensate (Philip et al. 1989). 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of negligible 
consequences. 
IRSR Issues: None for EBS 
References: (Philip et al. 1989) 
6.2.38 Condensation Forms on Backs of Drifts  YMP 2.1.08.04.00 
FEP Description: Emplacement of waste in drifts creates a large thermal gradient 
across the drifts. Moisture condenses on the roof and flows downward through the backfill. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: All potential pathways for water to reach the waste package must 
be considered to predict the onset of waste package failure. 
TSPA Disposition: The possibility of condensation forming on the backs of drifts is 
included in the thermal/hydraulical calculations of emplacement drift response, as documented in 
E0120 (CRWMS M&O 2000t). The possibility of condensation forming on the underside of the 
drip shield due to evaporation from the invert is also calculated and included in the EBS model 
for the TSPA (E0120 (CRWMS M&O 2000t)). Both of these water seepage mechanisms are 
incorporated in the EBS radionuclide transport abstraction, E0095 (CRWMS M&O 2000q).

ANL-WIS-PA-000002 REV 00 ICN 01 58 September 2000 
IRSR Issues: CLST1, ENFE, RT1, TEF 
References: E0095 (CRWMS M&O 2000q), E0120 (CRWMS M&O 2000t) 
6.2.39 Flow Through Invert  YMP 2.1.08.05.00 
FEP Description: The invert, a porous material consisting of crushed tuff, separates 
the waste package from the bottom of the tunnel (boundary to the UZ). 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Flow of seepage water and associated radionuclides, as applicable, 
through the invert must be modeled to characterize the source term for the UZ. 
TSPA Disposition: Advective and diffusive flow through the invert are included in the 
EBS radionuclide transport abstraction for TSPA, E0095 (CRWMS M&O 2000q). No credit for 
radionuclide transport delay mechanisms (for example, sorption) is included; a conservative 
modeling simplification. 
IRSR Issues: ENFE1, ENFE4 
References: E0095 (CRWMS M&O 2000q) 
6.2.40 Wicking in Waste and EBS  YMP 2.1.08.06.00 
FEP Description: Capillary rise, or wicking, is a potential mechanism for water to 
move through the waste and engineered barrier system. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Wicking is a water transport mechanism that must be 
accounted for in the TSPA. 
TSPA Disposition: Wicking in the invert is included in the calculated 
thermal/hydraulical response of the emplacement drift and surrounding host rock as documented in 
E0120 (CRWMS M&O 2000t). This wicking flux is included in calculating the fluid influx into 
the EBS as documented in E0095 (CRWMS M&O 2000q). Should backfill be included in the 
repository design, wicking in the quartz backfill would also need to be considered. 
IRSR Issues: ENFE1, ENFE2, ENFE4, RT1 
References: E0095 (CRWMS M&O 2000q), E0120 (CRWMS M&O 2000t)

ANL-WIS-PA-000002 REV 00 ICN 01 59 September 2000 
6.2.41 Pathways for Unsaturated Flow and Transport in the Waste and EBS  YMP 
2.1.08.07.00 
FEP Description: Unsaturated flow and radionuclide transport may occur along 
preferential pathways in the waste and EBS. Physical and chemical properties of the EBS and 
waste form, in both intact and degraded states, should be considered in evaluating pathways. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: The details of internal pathways providing release from a 
container are subsumed in an integrated release distribution. 
TSPA Disposition: The EBS radionuclide transport abstraction, E0095 (CRWMS M&O 
2000q) uses conservative assumptions to bound the impact of potential pathways on flow and 
transport. First, the waste form and waste package are represented as a single mixing cell. This 
mixing cell instantaneously equilibrates chemically with the waste form. In addition, there is no 
flow resistance into or out of the mixing cell. Second, pathways through the invert are ignored 
because the invert is a minor barrier to flow and transport in comparison to the waste package, the 
drip shield, or the UZ beneath the drift. 
IRSR Issues: ENFE1, ENFE2, ENFE4, RT1 
References: E0095 (CRWMS M&O 2000q) 
6.2.42 Induced Hydrological Changes in the Waste and EBS  YMP 2.1.08.08.00 
FEP Description: Thermal, chemical, and mechanical processes related to the 
construction of the repository and the emplacement of waste may induce changes in the 
hydrological behavior of the system. 
Note that this FEP also encompasses FEPs ebs # 13 and 14 from table 3. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: The hydrological behavior of the repository is influenced by 
the presence of the emplacement drift and the associated waste material. This must be accounted 
for in the performance assessment of the repository. 
TSPA Disposition: Relative to the EBS analysis, there are two ways in which induced 
hydrologic changes are accounted for. To the extent that the repository outside the tunnel is 
impacted (temperature, seepage flow, gas flow, etc.), this is accounted for in the EBS analysis 
through the boundary conditions provided by the NFE analysis and is not explicitly an EBS issue. 
Within the tunnel, the hydrological response of the EBS system is explicitly considered through the 
in-drift thermal-hydrologic analysis, E0120 (CRWMS M&O 2000t), taking into

ANL-WIS-PA-000002 REV 00 ICN 01 60 September 2000 
account the emplacement of the waste packages. This analysis is then an integral part of the EBS 
radionuclide transport abstraction, E0095 (CRWMS M&O 2000q) that feeds the TSPA. 
IRSR Issues: ENFE1, ENFE4, RDTME3, TEF 
References: E0095 (CRWMS M&O 2000q), E0120 (CRWMS M&O 2000t) 
6.2.43 Saturated Groundwater Flow in Waste and EBS  YMP 2.1.08.09.00 
FEP Description: Saturated flow and radionuclide transport may occur along 
preferential pathways in the waste and EBS. Physical and chemical properties of the EBS and 
waste form, in both intact and degraded states, should be considered in evaluating pathways. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Saturated flow pathways in the waste are screened out 
because the failed canister is conservatively assumed to provide no resistance to flow. Saturated 
flow pathways in the quartz sand backfill (if backfill were to be included in the repository design) 
would be screened out because wicking, driven by capillary forces, would distribute seepage 
uniformly throughout the drifts. Finally, saturated flow pathways in the invert are ignored because 
the invert is a very minor engineered barrier in the repository system, so that fast pathways in the 
invert will have negligible impact on performance. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: ENFE1, ENFE4 
References: E0095 (CRWMS M&O 2000q), E0090 (CRWMS M&O 2000p) 
6.2.44 Resaturation of Repository  YMP 2.1.08.11.00 
FEP Description: Water content in the repository will increase following the peak 
thermal period. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: The time-dependent water content in the repository is a key 
parameter that affects corrosion processes as well as waste form degradation. 
TSPA Disposition: The seepage influx and the capillary influx to the EBS are calculated 
as part of the NFE analysis as documented in E0130 (CRWMS M&O 2000u). This analysis 
calculates the coupled thermal/hydraulic response of the emplacement drifts and EBS

ANL-WIS-PA-000002 REV 00 ICN 01 61 September 2000 
and provides this as input to the EBS radionuclide transport abstraction, E0095 (CRWMS M&O 
2000q). 
IRSR Issues: None for EBS 
References: E0095 (CRWMS M&O2000q), E0130 (CRWMS M&O 2000u) 
6.2.45 Properties of the Potential Carrier Plume in the Waste and EBS  YMP 2.1.09.01.00 
FEP Description: When unsaturated flow in the drifts is re-established following the 
peak thermal period, water will have chemical and physical characteristics influenced by the near 
field host rock and EBS. Water chemistry may be strongly affected by interactions with 
cementitious materials. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: When the flow system re-establishes itself through the 
repository, because of repository temperature and introduced materials (principally concrete and 
Fe) the flow system will include the characteristics of the repository (pH, temperature, dissolved 
constituents, etc.). Thus, for example, fluids entering the drift interact chemically with the 
cementitious reinforcement around the rock bolts, producing a hyperalkaline fluid. It is this 
hyperalkaline fluid which interacts with the waste container and its contents. The chemistry of this 
plume determines the solubility of contaminants and their behavior in transport. Such a 
hyperalkaline plume interacts rapidly with glassified waste, converting glasses to clays, and thus 
must be considered in the TSPA. 
TSPA Disposition: The chemical and other properties of the carrier plume are assumed 
to be those of water in the invert where it is in contact with the UZ flow system. These properties 
are developed in the Seepage/Invert Interactions AMR, E0060 (CRWMS M&O 2000j), 
supporting E0010 (CRWMS M&O 2000b). These properties are influenced by the effects of the 
degradation of cementitious material in the drift-stabilization structures, which are analyzed in the 
Seepage/Cement Interactions AMR, E0055 (CRWMS M&O 2000i), and the corrosion of EBS 
metallic components, which are analyzed in the In Drift Corrosion Products AMR, E0020 
(CRWMS M&O 1999c). 
IRSR Issues: ENFE2, ENFE3, RT1 
References: E0095 (CRWMS M&O 2000q), E0010 (CRWMS M&O 2000b), 
E0020 (CRWMS M&O 1999c), E0060 (CRWMS M&O 2000j), 
E0055 (CRWMS M&O 2000i)

ANL-WIS-PA-000002 REV 00 ICN 01 62 September 2000 
6.2.46 Interaction with Corrosion Products  YMP 2.1.09.02.00 
FEP Description Corrosion products produced during degradation of the metallic portions of 
the EBS and waste package may affect the mobility of radionuclides. Sorption/desorption and 
coprecipitation/dissolution processes may occur. 
Note that this FEP also encompasses FEP ebs # 7 from table 3. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Interaction of contaminants with corrosion products (from 
the breached waste package or its carcass, from the pedestal, from rock reinforcement materials, 
etc.) is expected to control mobilization and speciation of the contaminants (e.g., Fe oxyhydroxides 
and colloids) and thus must be included in the performance assessment. 
TSPA Disposition: The effects of corrosion products on seepage water chemistry are 
analyzed in the In Drift Corrosion Products AMR, E0020 (CRWMS M&O 1999c) and the inpackage 
chemistry abstraction documented in F0170 (CRWMS M&O 2000w) supporting E0010 
(CRWMS M&O 2000b). (See also FEPS 2.1.06.02.00.) Flow interactions with these corrosion 
products have been screened out of the TSPA radionuclide transport abstraction, E0095 (CRWMS 
M&O 2000q). Corrosion products can potentially sorb radionuclides and provide resistance to 
flow through patches and pits. However, these features are conservatively ignored in the TSPA 
model. 
IRSR Issues: ENFE3, RT1 
References: E0095 (CRWMS M&O 2000q), E0010 (CRWMS M&O 2000b), 
E0020 (CRWMS M&O 1999c), F0170 (CRWMS M&O 2000w) 
6.2.47 In-drift Sorption  YMP 2.1.09.05.00 
FEP Description: Sorption of radionuclides within the waste and EBS may affect the 
aqueous concentrations. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Sorption of radionuclides on other materials within the EBS 
would serve to delay release to the environment. Thus, it is conservative from a consequences 
perspective to ignore this effect. 
TSPA Disposition: As a bounding estimation, sorption of fission products within the 
EBS, which would act to delay release, is conservatively ignored. 
IRSR Issues: RT1

ANL-WIS-PA-000002 REV 00 ICN 01 63 September 2000 
References: E0095 (CRWMS M&O 2000q) 
6.2.48 Reduction-oxidation Potential in Waste and EBS  YMP 2.1.09.06.00 
FEP Description: The redox potential in the waste and EBS influences the oxidation of 
barrier and waste-form materials and the solubility of radionuclide species. Local variations in 
the redox potential can occur. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Redox potential in the waste and engineered barrier system 
is included in TSPA modeling of the waste form and waste package. Redox potential in the drift 
environment has been considered in analysis of the potential for criticality. 
TSPA Disposition: Because of the location of the repository in the UZ, oxidizing 
conditions are assumed for all geochemical modeling supporting the TSPA. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0035 (CRWMS M&O 2000e), 
F0170 (CRWMS M&O 2000w) 
6.2.49 Reaction Kinetics in Waste and EBS  YMP 2.1.09.07.00 
FEP Description: Chemical reactions, such as radionuclide dissolution/precipitation 
reactions and reactions controlling the reduction-oxidation state, may not be equilibrium in the 
drift and waste environment. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Effects of kinetics on waste-form dissolution reactions are 
considered in the in-package chemistry abstraction documented in F0170 (CRWMS M&O 2000w) 
supporting E0010 (CRWMS M&O 2000b). However, relative to the EBS modeling, subtleties of 
the reduction-oxidation reactions are only of interest if they actually significantly affect 
radionuclide transport. Use of experimentally derived Kds (reaction rate coefficients) already 
averages over interactions (and material heterogeneity). Thus, the specific effects of redox 
kinetics (separate from those incorporated in the data) are therefore excluded from the TSPA in 
E0010 (CRWMS M&O 2000b) on the basis of low consequence. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1

ANL-WIS-PA-000002 REV 00 ICN 01 64 September 2000 
References: E0010 (CRWMS M&O 2000b), F0170 (CRWMS M&O 2000w) 
6.2.50 Chemical Gradients/Enhanced Diffusion in Waste and EBS  YMP 2.1.09.08.00 
FEP Description: The existence of chemical gradients within the disposal system, 
induced naturally or resulting from repository material and waste emplacement, may influence the 
transport of contaminants of dissolved and colloidal species. This could include, for example, 
diffusion in and through failed canisters. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: In Yucca Mountain, the establishment of carrier plumes, 
each with the signature of the repository (with respect to temperature and chemistry-including 
hyperalkalinity), means that there are persistent chemical gradients, which identify the boundaries 
of the plumes. Sorption and reaction of contaminants with host rock occur within these plumes, at 
least until they become well-mixed with connate waters. Thus, the chemistry of the plumes is 
important, in contrast to the chemical gradients across their boundaries. At the present time, the 
waste form is represented by a mixing cell that conservatively assumes instantaneous chemical 
equilibrium. Chemical gradients and enhanced diffusion will have no impact on waste form 
performance. In addition, there is no flow resistance into or out of the failed waste packages, so 
advective transport will move radionuclides out of the failed containers at a much faster rate than 
would be calculated based on diffusion. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: ENFE4, RT1 
References: E0095(CRWMS M&O 2000q), E0045 (CRWMS M&O 2000g) 
6.2.51 Waste-Rock Contact  YMP 2.1.09.11.00 
FEP Description: Waste and rock are placed in contact by mechanical failure of the 
drip shields and waste packages. Reactions between uranium, rock minerals, and water, in contact 
with both, precipitate uranium, leading spent fuel to dissolve more rapidly than if constrained by 
the equilibrium solubility of uranium. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Waste and rock could come in contact by mechanical failure 
of the drip shields and waste packages. Reactions between uranium, rock minerals, and water, in 
contact with both, could precipitate uranium, leading spent fuel to dissolve more rapidly than if

ANL-WIS-PA-000002 REV 00 ICN 01 65 September 2000 
constrained by the equilibrium solubility of waste-form uranium phases. To the extent that such 
enhanced dissolution could occur, this is a waste form degradation issue and not modeled 
explicitly in the EBS analysis. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: ENFE3 
References: E0010 (CRWMS M&O 2000b) 
6.2.52 Rind (Altered Zone) Formation in Waste, EBS, and Adjacent Rock  YMP 
2.1.09.12.00 
FEP Description: Thermo-chemical processes involving precipitation, condensation, 
and redissolution alter the properties of the waste, EBS, and the adjacent rock. These alterations 
may form a rind, or altered zone, in the rock, with hydrological, thermal, and mineralogical 
properties different from the current conditions. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: The thermo-chemical-hydrological processes that will 
produce a rind are known to occur; the questions are, at what rate and to what depth. However, 
the effects of such a rind would manifest themselves as changes in the water seepage rate coming 
into the drift, the chemistry of that seepage, and the rate of gas influx. These parameters all 
represent boundary conditions to the EBS performance assessment. Thus, while this FEP may be 
of importance from an overall repository performance perspective, it is not germane to the EBS 
analysis other than through input from the NFE. 
TSPA Disposition: This FEP is not directly relevant to modeling of the EBS other than 
through flow boundary conditions derived from the NFE. 
IRSR Issues: None for EBS 
References: E0100 (CRWMS M&O 2000r) 
6.2.53 Complexation by Organics in Waste and EBS  YMP 2.1.09.13.00 
FEP Description: The presence of organic complexants in water in the waste and EBS 
could augment radionuclide transport by providing a transport mechanism in addition to simple 
diffusion and advection of dissolved material. Organic complexants may include materials found 
in natural groundwater such as humates and fulvates, or materials introduced with the waste or 
engineered materials.

ANL-WIS-PA-000002 REV 00 ICN 01 66 September 2000 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Complexation of radionuclides with organic species has 
been excluded from the TSPA on the basis of negligible consequences for two reasons. First, this 
mechanism would be most significant if it could alter the form of the dissolved radionuclides 
thereby reducing the likelihood of sorption in the invert. However, since sorption is presently 
ignored in the TSPA (see FEP 2.1.09.05.00), the transport of radionuclides is already maximized, 
and the neglect of complexation has no impact on the calculated release rate. Second, 
complexation in the immediate vicinity of the waste form could increase the rate of radionuclide 
release if the release rate is concentration limited. However, the low concentration of organics in 
the Yucca Mountain repository (CRWMS M&O 2000f) makes this effect negligible. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: ENFE4, RT1 
References: E0010 (CRWMS M&O 2000b), E0040 (CRWMS M&O 2000f) 
6.2.54 Colloid Formation in Waste and EBS  YMP 2.1.09.14.00 
FEP Description: Colloids in the waste and EBS may affect radionuclide transport. 
Different types of colloids may exist initially or may form during the evolution of the system by a 
variety of mechanisms. This FEP aggregates all types of colloids into a single category. Technical 
discussions of colloids for the Yucca Mountain repository are presented separately for true 
colloids (FEP 2.1.09.15.00), natural pseudo-colloids (FEP 2.1.09.16.00), pseudo-colloids formed 
from corrosion products (FEP 2.1.09.17.00), and microbial colloids (FEP 2.1.09.18.00) 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: See separate discussion under FEPs 2.1.09.15.00, 
2.1.09.16.00, 2.1.09.17.00, and 2.1.09.18.00. 
TSPA Disposition: See separate discussion under FEPs 2.1.09.15.00, 2.1.09.16.00, 
2.1.09.17.00, and 2.1.09.18.00. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0045 (CRWMS M&2000g) 
6.2.55 Formation of True Colloids in Waste and EBS  YMP 2.1.09.15.00 
FEP Description: True colloids are colloidal-sized assemblages (between

ANL-WIS-PA-000002 REV 00 ICN 01 67 September 2000 
approximately 1 nanometer and 1 micrometer in diameter) of radionuclide-containing compounds. 
They may form in the waste and EBS during waste-form degradation and radionuclide transport. 
True colloids are also called radionuclide intrinsic colloids (or actinide intrinsic colloids, for 
those including actinide elements). 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: The formation of true colloids may occur as part of the 
waste form degradation process (as discussed in F0170 (CRWMS M&O 2000w)). Additional 
true colloid formation within the EBS is excluded in the TSPA on the basis of negligible 
consequences. This is because the EBS radionuclide transport abstraction, E0095 (CRWMS 
M&O 2000q) does not consider any retardation mechanisms that would cause radionuclides to 
precipitate out anywhere within the EBS. Thus, even if radionuclide-bearing true colloids were to 
form, it would not impact the radionuclide source term to the NFE as the rate of radionuclide 
transport is already maximized. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of negligible 
consequences. 
IRSR Issues: RT1 
References: E0095 (CRWMS M&O 2000q), F0170 (CRWMS M&O 2000w) 
6.2.56 Formation of Pseudo-colloids (natural) in Waste and EBS  YMP 2.1.09.16.00 
FEP Description: Pseudo-colloids are colloidal-sized assemblages (between 
approximately 1 nanometer and 1 micrometer in diameter) of nonradioactive material that has 
radionuclides bound to it. Pseudo-colloids include microbial colloids, mineral fragments, and 
humic and fulvic acids. This FEP addresses radionuclide-bearing colloids formed from host-rock 
materials and all interactions of the waste and EBS with the host rock environment except 
corrosion. Pseudo-colloids formed from corrosion of the waste form and EBS are discussed in 
FEP 2.1.09.17.00. Microbial colloids are discussed in FEP 2.1.09.18.00. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Natural colloids (clay, silica, and iron oxyhydroxides) may 
be transported in groundwater into the repository from the vadose zone above it or may be formed 
from the erosion of natural backfill (if backfill were included in the repository design in the future) 
and invert materials (e.g., crushed tuff). Pseudo-colloids may form due to the sorption onto these 
natural colloids of radionuclides mobilized from degradation of the waste form. Pseudo-colloids, 
thus formed in the waste and EBS, may influence radionuclide transport. Analyses and field 
studies show that radionuclides attached to colloids may be transported long distances relative to 
the aqueous radionuclide.

ANL-WIS-PA-000002 REV 00 ICN 01 68 September 2000 
TSPA Disposition: The impact of natural pseudo-colloids on radionuclide transport is 
accounted for through the determination of colloid-associated radionuclide concentration limits 
(CRWMS M&O 2000v) the implementation of which is discussed in E0045 (CRWMS M&O 
2000g). 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0045 (CRWMS M&O 2000g), 
CRWMS M&O 2000v 
6.2.57 Formation of Pseudo-colloids (corrosion products) in Waste and EBS  YMP 
2.1.09.17.00 
FEP Description: Pseudo-colloids are colloidal-sized assemblages (between 
approximately 1 nanometer and 1 micrometer in diameter) of nonradioactive material that has 
radionuclides bound to it. Pseudo-colloids include microbial colloids, mineral fragments, and 
humic and fulvic acids. This FEP addresses pseudo-colloids such as iron oxyhydroxides formed 
from corrosion and degradation of the metals in the waste form and EBS. Radionuclide-bearing 
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 2.1.09.16.00. Microbial colloids are 
discussed in FEP 2.1.09.18.00. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Artificial materials (e.g., cement grout, carbon steel, 
stainless steel, aluminum, titanium-7, and Alloy-22) will be introduced during construction of the 
repository. The corrosion of these materials may produce significant quantities of colloids, 
primarily metal oxyhydroxides. Radionuclides will tend to sorb onto the colloids, forming 
pseudo-colloids as well as onto larger particles and scale. In addition, the degradation of waste 
glass and spent nuclear fuel will likely produce clays (with and possibly without entrained 
radionuclide-bearing phases), another substrate for pseudo-colloids in the drift. Pseudocolloids 
thus formed in the waste and EBS may influence radionuclide transport. Analyses and 
field studies show that radionuclides attached to colloids may be transported long distances 
relative to the aqueous radionuclide. 
TSPA Disposition: The impact of pseudo-colloids (from corrosion products) on 
radionuclide transport is accounted for through the determination of colloid-associated 
radionuclide concentration limits (CRWMS M&O 2000v), the implementation of which is 
discussed in E0045 (CRWMS M&O 2000g). 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0045 (CRWMS M&O 2000g), 
CRWMS M&O 2000v

ANL-WIS-PA-000002 REV 00 ICN 01 69 September 2000 
6.2.58 Microbial Colloid Transport in the Waste and EBS  YMP 2.1.09.18.00 
FEP Description: This FEP addresses the formation and transport of microbial 
colloids in the waste and EBS. Pseudo-colloids formed from corrosion and degradation of the 
metals in the waste form and EBS are discussed in FEP 2.1.09.16.00. Radionuclide-bearing 
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 2.1.09.17.00. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Microbes can affect the amount of mobile colloidal material 
such as clay, hematite, goethite, and silica by influencing the rate of waste package corrosion. 
Given the present state of knowledge, estimates of the effects of microbes on corrosion processes 
are highly uncertain. However, the quantities of microbes that will be available to accelerate 
corrosion rates are very low, as calculated in E0040 (CRWMS M&O 2000f). Also, microbial 
action tends to increase colloid size, which would result in increased gravitational settling and 
filtration. Therefore, exclusion of microbial effects from TSPA may be considered conservative. 
A more comprehensive discussion of such microbial colloids is presented in CRWMS M&O 
2000v. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of negligible 
consequences. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0045 (CRWMS M&O 2000g), 
E0040 (CRWMS M&O 2000f), CRWMS M&O 2000v 
6.2.59 Colloid Transport and Sorption in the Waste and EBS  YMP 2.1.09.19.00 
FEP Description: Interactions between radionuclide-bearing colloids and the waste 
and EBS may result in retardation of the colloids during transport by sorption mechanisms. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: The TSPA considers that all radionuclide-bearing colloids 
generated from waste form degradation within a failed waste package will leave the waste 
package and enter the drift and EBS. In reality, interactions between these radionuclide-bearing 
colloids and the waste and EBS would result in some retardation of the colloid transport by 
sorption mechanisms. However, as with in-drift sorption of dissolved radionuclides (FEP 
2.1.09.05.00), this phenomenon is conservatively ignored. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low expected 
consequences, coupled with the fact that its exclusion is conservative.

ANL-WIS-PA-000002 REV 00 ICN 01 70 September 2000 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0045 (CRWMS M&O 2000g), 
E0095 (CRWMS M&O 2000q) 
6.2.60 Colloid Filtration in the Waste and EBS  YMP 2.1.09.20.00 
FEP Description: Filtration processes may affect transport of radionuclide-bearing 
colloids in the waste and EBS. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Transport of colloids within the EBS (within the tunnel) 
conservatively excludes consideration of colloid filtration. In this way, the rate of transport of 
radionuclides into the unsaturated zone is maximized. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low expected 
consequences, coupled with the fact that its exclusion is conservative. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0045 (CRWMS M&O 2000g), 
E0095 (CRWMS M&O 2000q) 
6.2.61 Suspensions of Particles Larger than Colloids  YMP 2.1.09.21.00 
FEP Description: Groundwater flow through the waste could remove radionuclidebearing 
particles by a rinse mechanism. Particles of radionuclide bearing material larger than 
colloids could then be transported in water flowing through the waste and EBS by suspension. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Suspension of radionuclide bearing particles in groundwater 
flowing downward through the invert could lead to an enhanced radionuclide source term at the UZ 
boundary. However, it is shown in CRWMS M&O 2000v that the suspension of particles larger 
than colloids in the UZ and saturated zone (SZ) can be excluded on the basis of consequences. 
Hence, any transport of such particulate within the tunnel is irrelevant to repository performance 
and can be excluded on the consequences. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1

ANL-WIS-PA-000002 REV 00 ICN 01 71 September 2000 
References: E0095 (CRWMS M&O 2000q), CRWMS M&O 2000v 
6.2.62 Biological Activity in Waste and EBS  YMP 2.1.10.01.00 
FEP Description: Biological activity in the waste and EBS may affect disposal-system 
performance by altering degradation processes such as corrosion of the waste packages and waste 
form (including cladding), by affecting radionuclide transport through the formation of colloids and 
biofilms, and by generating gases. 
Note that this FEP also encompasses FEP ebs # 25 from table 3. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Microbes can affect the mobility of colloidal material, as 
well as influence the rate of waste package corrosion. 
TSPA Disposition: The maximum mass of microbes is calculated in the In-Drift 
Microbial Communities AMR, E0040 (CRWMS M&O 2000f) and passed to the TSPA as a factor 
affecting patch corrosion of the drip shield and canister. A more comprehensive discussion of this 
FEP for all aspects of repository performance can be found in CRWMS M&O 2000v. It should be 
noted that this discussion concludes that from an overall repository performance perspective, this 
FEP can be excluded on the basis of consequences. 
IRSR Issues: CLST1, ENFE2, ENFE3, ENFE4, RT1 
References: E0010 (CRWMS M&O 2000b), E0045 (CRWMS M&O 2000g), 
E0040 (CRWMS M&O 2000f), CRWMS M&O 2000v 
6.2.63 Heat Output/Temperature in Waste and EBS  YMP 2.1.11.01.00 
FEP Description: Temperature in the waste and EBS will vary through time. Heat 
from radioactive decay will be the primary cause of temperature change, but other factors to be 
considered in determining the temperature history include the in-situ geothermal gradient, thermal 
properties of the rock, EBS, and waste materials, hydrological effects, and the possibility of 
exothermic reactions (see FEP 2.1.11.03.00). Considerations of the heat generated by radioactive 
decay should take different properties of different waste types, including DSNF, into account. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Decay heat is a major issue in repository design, particularly 
at Yucca Mountain, where high loading densities and high temperatures are intended to be part of 
the waste isolation scheme.

ANL-WIS-PA-000002 REV 00 ICN 01 72 September 2000 
TSPA Disposition: Relative to the performance assessment of the EBS, the temperature 
history is calculated explicitly as part of the Multiscale Thermohydrologic Model, E0120 
(CRWMS M&O 2000t). 
IRSR Issues: TEF 
References: E0120 (CRWMS M&O 2000t) 
6.2.64 Exothermic Reactions in Waste and EBS  YMP 2.1.11.03.00 
FEP Description: Exothermic reactions liberate heat and will alter the temperature of 
the disposal system and affect the properties of the repository and surrounding materials. 
Hydration of concrete used in the underground environment is an example of a possible exothermic 
reaction. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: A repository at Yucca Mountain is planned to be "hot." 
Maximum rock temperatures in the drift walls are expected to reach 165-185C (CRWMS M&O 
2000k). The temperature changes suggested in this FEP are inconsequential by comparison. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: TEF 
References: E0010 (CRWMS M&O 2000b), E0055 (CRWMS M&O 1999i), 
CRWMS M&O 2000k 
6.2.65 Temperature Effects/Coupled Processes in Waste and EBS  YMP 2.1.11.04.00 
FEP Description: This FEP broadly encompasses all coupled-process effects of 
temperature changes within the waste and EBS. Technical discussions relevant to this FEP are 
provided individually for each relevant process. See FEP 2.1.11.01.00 for a discussion of the 
temperature history of repository. See FEP 2.1.11.03.00 for a discussion of possible exothermic 
reactions. See FEP 2.1.11.05.00 for a discussion of the effects of differential thermal expansion of 
repository components. See FEP 2.1.11.07.00 for a discussion of thermally-induced stresses in 
the waste and EBS. See FEP 2.1.11.08.00 for a discussion of thermal effects on chemical and 
microbial processes. See FEP 2.1.11.09.00 for a discussion of thermal effects on fluid flow in the 
waste and EBS. See 2.1.11.10.00 for a discussion of the Soret effect. 
Screening Decision: Include 
Screening Decision Basis: N/A

ANL-WIS-PA-000002 REV 00 ICN 01 73 September 2000 
Screening Argument: Yucca Mountain evolves mechanically, chemically, and 
hydrologically under the influence of heat. This thermal evolution has a significant impact on all 
aspects of repository performance, including water seepage rates, corrosion rates, dissolution 
chemistry, etc. See discussion for each specific FEP identified in the FEP definition for more 
detail. 
TSPA Disposition: The temperature history of the in-drift environment is calculated 
explicitly as part of the Multiscale Thermohydrologic Model, E0120 (CRWMS M&O 2000t). 
Relative to EBS performance, the effect of this temperature history on chemistry is included in the 
rates of waste form degradation processes abstracted in F0170 (CRWMS M&O 2000w) and in the 
temperature-dependent equilibrium constants included in the geochemical models supporting the 
EBS Physical and Chemical Environmental Abstraction Model, E0010 (CRWMS M&O 2000b) 
and its submodels. See discussion for each specific FEP identified in the FEP definition for more 
detail. 
IRSR Issues: TEF 
References: E0120 (CRWMS M&O 2000t), E0010 (CRWMS M&O 2000b), 
F0170 (CRWMS M&O 2000w) 
6.2.66 Differing Thermal Expansion of Repository Components  YMP 2.1.11.05.00 
FEP Description: Thermally-induced stresses could alter the performance of the waste 
or EBS. For example, thermal stresses could create pathways for preferential fluid flow in the 
backfill or through the drip shield. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Thermal expansion induced failure (separation) of the drip 
shields has been screened out because the anticipated change in length is generally much less than 
the overlap between adjacent drip shields (see discussion in E0095 (CRWMS M&O 2000q)). 
Thermal expansion of other components, such as the waste package and pedestal, will not be a 
problem because the separation between adjacent waste packages is adequate to accommodate this 
small amount of expansion. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: CLST2, ENFE1, ENFE4, RDTME3 
References: E0095 (CRWMS M&O 2000q)

ANL-WIS-PA-000002 REV 00 ICN 01 74 September 2000 
6.2.67 Thermally-induced Stress Changes in Waste and EBS  YMP 2.1.11.07.00 
FEP Description: Thermally-induced stress changes in the waste and EBS may affect 
performance of the repository. Relevant processes include rockfall, drift stability, changes in 
physical properties of the disturbed rock zone around the repository, and changes in the physical 
properties of the surrounding rock. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Repository heat at Yucca Mountain will drive the 
mechanical and chemical evolution of the repository and the mountain, producing durable changes. 
Thermal expansion (and thermo-mechanical coupling) is expected to rotate the least principal 
stress, currently NNW-SSE, to vertical, and after cooling, thermal contraction will rotate it back. 
Durable changes to the fracture flow systems are anticipated. 
TSPA Disposition: Relative to the EBS analysis effort, the only relevant effect 
delineated above involves the impact of thermal stress on drift degradation (and thus rockfall). 
This is explicitly accounted for in the Drift Degradation Analysis, E0080 (CRWMS M&O 
2000n). Impacts on the physical properties of the surrounding rock are implicitly accounted for, 
relative to EBS modeling, through changes in the water seepage influx boundary conditions from 
the NFE analysis. 
IRSR Issues: CLST2, ENFE1, ENFE4, RDTME3 
References: E0080 (CRWMS M&O 2000n) 
6.2.68 Thermal Effects: Chemical and Microbiological Changes in the Waste and EBS  
YMP 2.1.11.08.00 
FEP Description: Temperature changes may affect chemical and microbial processes 
in the waste and EBS. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Chemical reaction and microbial process rates are very 
sensitive to temperature. Thus, this dependence must be accounted for. 
TSPA Disposition: The effects of temperature on chemical reaction properties are 
included in the geochemical models supporting E0010 (CRWMS M&O 2000b) and its submodels. 
The effects of temperature on microbial growth are included in the In-Drift Microbial 
Communities AMR, E0040 (CRWMS M&O 2000f). 
IRSR Issues: ENFE1, ENFE2, ENFE3, ENFE4, RT1 
References: E0010 (CRWMS M&O 2000b) and all its submodel abstractions

ANL-WIS-PA-000002 REV 00 ICN 01 75 September 2000 
6.2.69 Thermal Effects on Liquid or Two-phase Fluid Flow in the Waste and EBS  YMP 
2.1.11.09.00 
FEP Description: Temperature differentials may result in convective flow in the waste 
and EBS. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Thermal effects may have an important influence on the rate 
of water contact with the waste package and/or drip shield (thereby influencing the corrosion rate) 
and on the rate of water influx into a failed waste package (thereby influencing the rate of waste 
form dissolution). Examples of this include localized dryout in the immediate vicinity of the waste 
packages during the early thermal phase of the repository history, as well as evaporation 
condensation on the underside of the drip shield providing an additional source term of water for 
dripping onto the waste package. 
TSPA Disposition: Thermal effects on liquid or two-phase flow within the waste and 
EBS are explicitly accounted for in the Multiscale Thermohydrologic Model, E0120 (CRWMS 
M&O 2000t). This includes consideration of dryout near the waste packages, as well as 
evaporation/condensation within the drift and underneath the drip shield. The results of these 
analyses then feed the EBS Radionuclide Transport Abstraction, E0095 (CRWMS M&O 2000q). 
IRSR Issues: ENFE1, ENFE2, ENFE3, RT1 
References: E00120 (CRWMS M&O 2000t), E0095 (CRWMS M&O 2000q) 
6.2.70 Thermal Effects on Diffusion (Soret effect) in Waste and EBS  YMP 2.1.11.10.00 
FEP Description: The Soret effect is a diffusion process caused by a thermal gradient. 
In liquids having both light and heavy molecules (or ions), the heavier molecules tend to 
concentrate in the cold region. Temperature differences in the waste and EBS may result in a 
component of diffusive solute flux that is proportional to the temperature gradient. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: The potential for the Soret effect should be greatest during 
the first 3,000 years when the maximum thermal response occurs in the repository (CRWMS M&O 
2000k). However, during this time, the waste packages and drip shields will be essentially intact, 
and thus there will be near-zero release during this time. Later in time, the thermal gradients 
within the EBS are reduced. Further, the seepage flow conditions are such that the invert (the 
primary region through which contaminant transport occurs) is expected to remain unsaturated,

ANL-WIS-PA-000002 REV 00 ICN 01 76 September 2000 
further minimizing the likelihood of thermally-driven diffusion. In light of the various simplifying, 
conservative assumptions currently made in the EBS Radionuclide Transport Abstraction, E0095 
(CRWMS M&O 2000q), which includes full advective transport of all radionuclides released 
from the waste form with no consideration of delay mechanisms such as sorption, the neglect of the 
Soret effect is considered to be of negligible consequences. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: ENFE1, ENFE4, RT1 
References: E0095 (CRWMS M&O 2000q) 
6.2.71 Gas Generation  YMP 2.1.12.01.00 
FEP Description: Gas may be generated in the repository by a variety of mechanisms. 
Gas generation might lead to pressurization of the repository, produce multiphase flow, and affect 
radionuclide transport. This FEP aggregates all types of gas generation into a single category. 
Technical discussions are presented separately for gas generation from fuel decay (FEP 
2.1.12.02.00), corrosion (FEP 2.1.12.03.00), microbial degradation (FEP 2.1.12.04.00), concrete 
(FEP 2.1.12.02.05.00), radioactive gases within the waste (FEP 2.1.12.07.00), and radiolysis 
(2.1.13.01.00). 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Because the repository would be in the UZ, which is well 
connected to the surface, gas produced by whatever reaction is expected to escape or at least be 
only temporarily confined beneath the condensate zone above the drifts. Gas permeability, as 
measured in pneumatic tests, is believed to be adequate to allow escape. The calculation of the 
specific gas flux and composition within the EBS is delineated in the In-Drift Gas Flux and 
Composition, E0035 (CRWMS M&O 2000 e), which supports the EBS Physical and Chemical 
Environmental Abstraction Model, E0010 (CRWMS M&O 2000b). 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0035 (CRWMS M&O 2000e) 
6.2.72 Gas Generation (He) from Fuel Decay  YMP 2.1.12.02.00 
FEP Description: Helium (He) gas production may occur by alpha decay in the fuel.

ANL-WIS-PA-000002 REV 00 ICN 01 77 September 2000 
He production might cause local pressure buildup in cracks in the fuel and in the void between fuel 
and cladding, leading to cladding failure. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: He production is a result of alpha decay of actinides, so it is 
a consequence of the decay process. This He production could manifest itself in one of two ways. 
First, it could result in earlier failure of commercial spent nuclear fuel cladding as a result of 
higher internal gas pressures. This is a WF issue, and is discussed in the WF FEPs summary 
(CRWMS M&O 2000x). The second effect could be as another source of gas generation that might 
lead to pressurization of the repository (see FEP 2.1.12.01.00). This latter effect has already been 
screened out because of the placement of the drift within the UZ of the repository. Because of the 
inert nature of the He gas, no chemical effects (water chemistry changes) are expected. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0035 (CRWMS M&O 2000e), 
CRWMS M&O 2000x 
6.2.73 Gas Generation (H2) from Metal Corrosion  YMP 2.1.12.03.00 
FEP Description: Gas generation can affect the mechanical behavior of the host rock 
and engineered barriers, chemical conditions, and brine flow, and, as a result, the transport of 
radionuclides. Gas generation due to oxic corrosion of waste containers, cladding, and/or 
structural materials will occur at early times following closure of the repository. Anoxic 
corrosion may follow the oxic phase, if all oxygen is depleted. The formation of a gas phase 
around the canister may even exclude water from the iron, thus inhibiting further corrosion. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Gas generated from corrosion of metal components within 
the EBS can have three influences; the hydrogen generated may impact the chemistry of the seepage 
flow within the drift, the hydrogen generated may blanket the metal structure and inhibit further 
corrosion, and the gas generated may be another contributor to potential repository pressurization. 
Since a repository in Yucca Mountain would be located in the UZ and therefore be well-connected 
to the atmosphere, it is not expected that the oxidation state of the groundwater would be affected. 
The primary effect may be to cause some embrittlement of the metal structures, but this is only of 
potential significance to the waste package and drip shield (a WP issue). The potential blanketing 
of the metal structure with hydrogen gas, thereby inhibiting

ANL-WIS-PA-000002 REV 00 ICN 01 78 September 2000 
further corrosion, is conservatively ignored. Finally, the last effect (repository pressurization) has 
already been screened out (see FEP 2.1.12.01.00) because of the placement of the drift within the 
UZ of the repository. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0035 (CRWMS M&O 2000e) 
6.2.74 Gas Generation (CO2, CH4, H2S) from Microbial Degradation  YMP 2.1.12.04.00 
FEP Description: Microbial breakdown of cellulosic material, and possibly plastics 
and other synthetic materials, will produce mainly CO2, but also other gases. The rate of 
microbial gas production will depend upon the nature of the microbial populations established, the 
prevailing conditions (temperature, pressure, geochemical conditions), and the substrates present. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: A maximum value has been set on the quantity of organic 
materials that could be left in the repository at the time of closure (CRWMS M&O 1995b). 
Further, the level of microbial activity, as discussed in E0040 (CRWMS M&O 2000f), is expected 
to be low. Hence, the quantity of gases generated due to microbial activity is expected to be small. 
As discussed for FEP 2.1.12.01.00, any such gas generated would have negligible impact on 
repository performance because of its being situated in the UZ. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0040 (CRWMS M&O 2000f), 
E0035 (CRWMS M&O 2000e) 
6.2.75 Gas Generation from Concrete  YMP 2.1.12.05.00 
FEP Description: Production of gases from the aging and degradation of concrete may 
occur through radiolysis of water in the cement pore spaces and microbial growth on concrete. 
Screening Decision: Exclude

ANL-WIS-PA-000002 REV 00 ICN 01 79 September 2000 
Screening Decision Basis: Low Consequences 
Screening Argument: At Yucca Mountain, decomposition of concrete by radiolysis 
is not considered, because the only cementitious material (grout around rock bolts) is located far 
from any radioactive waste forms. In addition, the repository location in the UZ reduces the 
dominance of aqueous corrosion. The character of the cementitious material degradation 
processes is delineated in the Seepage/Cement Interactions Abstraction, E0055 (CRWMS M&O 
2000i). While the impact of these interactions on water chemistry is accounted for, the impact of 
the generated gases is ignored. As discussed for FEP 2.1.12.01.00, any such gas generated would 
have negligible impact on repository performance because of its being situated in the UZ. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0055 (CRWMS M&O 2000i), 
E0035 (CRWMS M&O 2000e) 
6.2.76 Gas Transport in Waste and EBS  YMP 2.1.12.06.00 
FEP Description: Gas in the waste and engineered barrier system could affect the 
long-term performance of the disposal system. Radionuclides may be transported as dissolved 
gases or in gas bubbles. These may affect flow paths, and two-phase flow conditions may be 
important. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: The only normally occurring gases of concern at Yucca 
Mountain are 14CO2, various radioactive fission gases, and Radon. For a repository in the UZ, 
these readily escape to the atmosphere. Thus, no significant gas buildup within the EBS occurs, 
and impact on flow paths is negligible. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0035 (CRWMS M&O 2000e) 
6.2.77 Radioactive Gases in Waste and EBS  YMP 2.1.12.07.00 
FEP Description: Radioactive gases may exist or be produced in the repository. These 
gases may subsequently escape from the repository. Typical radioactive gases include 14-

ANL-WIS-PA-000002 REV 00 ICN 01 80 September 2000 
C (in 14CO2 and 14CH4 ) produced during microbial degradation, tritium, fission gases (Ar, Xe, 
Kr), and radon. 
Screening Decision: Exclude (for EBS) 
Screening Decision Basis: Low Consequences 
Screening Argument: The radioactive gases are 14CO2 and 14CH4, fission gases 
(Ar, Xe, Kr) and radon (Rn). The CO2, CH4 and fission gases will in part escape from the 
mountain. To the extent that these have a significant contribution on the calculated source term, they 
are considered in the TSPA. Relative to the impact of these gases on repository performance due 
to pressurization effects, they are ignored. As discussed for FEP 2.1.12.01.00, any such gas 
generated would have negligible impact on repository performance because of its being situated in 
the UZ. 
TSPA Disposition: This FEP is excluded from the TSPA (for the EBS) on the basis of 
low consequences. 
IRSR Issues: RT1 
References: E0010 (CRWMS M&O 2000b), E0035 (CRWMS M&O 2000e) 
6.2.78 Gas Explosions  YMP 2.1.12.08.00 
FEP Description: Explosive gas mixtures could collect in the sealed repository. An 
explosion in the repository could have radiological consequences if the structure of the repository 
were damaged or near-field processes enhanced or inhibited. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: As discussed under FEPs YMP 2.1.12.01-05, there are a 
number of sources for gas generation, some of which result in the production of flammable gases 
(H2, CH4, and C2H2). Generally however, the permeability of Yucca Mountain to air will provide 
an adequate condition for the flammable/explosive gases to be diluted, diffused, and/or dispersed 
before they could reach explosive concentrations. Possibly, gases, as well as water, could 
accumulate, if there was a condensation cap or reduced permeability. However, no viable ignition 
source can be identified. Further, the possibility of a condensation cap has been essentially 
eliminated in the current design by greatly increasing the distance between the disposal tunnels 
(CRWMS M&O 2000ii). The possibility of reduced permeability to gas would also limit the 
availability of oxygen for combustion and greatly reduce the corrosion of containers, thereby 
reducing the number of containers potentially producing flammable/explosive gases. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences.

ANL-WIS-PA-000002 REV 00 ICN 01 81 September 2000 
IRSR Issues: RT1 
References: CRWMS M&O 2000ii 
6.2.79 Radiolysis  YMP 2.1.13.01.00 
FEP Description: Alpha, beta, gamma, and neutron irradiation of water can cause 
dissociation of molecules, leading to gas production and changes in chemical conditions (Eh, pH, 
concentration of reactive radicals). 
Screening Decision: Exclude for EBS 
Screening Decision Basis: N/A to EBS 
Screening Argument: Radiolysis occurs around the container and may produce 
more aggressive fluids. Only radiolysis due to gamma and neutron radiation is possible as long as 
the container is intact. It will have some impact on water chemistry in the vicinity of the canister. 
The effects of radiolysis would be included in the integrated corrosion models for the waste 
package and drip shield. See the WP FEPs summary (CRWMS M&O 2000dd) for a discussion of 
this phenomenon. Related FEPs are discussed under 2.1.12.01.00 (gas generation) and 
2.1.09.06.00 (redox potential in waste and EBS). Alpha and beta radiolysis, occurring up to .03 
mm from the fuel pellets, will be of importance after canister failure, when water gets in close 
contact with the fuel matrix. For a discussion of this relative to its impact on waste form 
degradation, see the WF FEPs summary (CRWMS M&O 2000x). 
TSPA Disposition: Excluded for the EBS analysis. 
IRSR Issues: ENFE2, ENFE3, RT1 
References: CRWMS M&O 2000x, CRWMS M&O 2000dd 
6.2.80 Radiation Damage in Waste and EBS  YMP 2.1.13.02.00 
FEP Description: Strong radiation fields could lead to radiation damage to the waste 
forms and containers (CSNF, DSNF, DHLW), backfill, drip shield, seals, and surrounding rock. 
Screening Decision: Exclude (backfill, seals, pedestal, etc.) 
Screening Decision Basis: Low Consequences 
Screening Argument: Radiation damage that affects mobilization of contaminants 
is included in the data describing such mobilization and is therefore implicitly included in 
modeling. Further, this is a WF issue as discussed in the WF FEPs summary (CRWMS M&O 
2000x). Radiation damage to the waste packages and/or drip shields is a WP issue as discussed in 
the WP FEPs summary (CRWMS M&O 2000dd). Radiation damage to other EBS structural 
components is expected to be negligible. Further, even if there were any damage to the pedestal,

ANL-WIS-PA-000002 REV 00 ICN 01 82 September 2000 
its failure is already assumed in the EBS Radionuclide Transport Abstraction, E0095 (CRWMS 
M&O 2000q). Thus, the consequences associated with this FEP relative to pedestal failure are 
already bounded in the current TSPA analysis. 
TSPA Disposition: This FEP is excluded form the TSPA on the basis of low 
consequences (included via bounding assumptions). 
IRSR Issues: All 
References: E0095 (CRWMS M&O 2000q), CRWMS M&O 2000x, CRWMS 
M&O 2000dd 
6.2.81 Mutation  YMP 2.1.13.03.00 
FEP Description: Radiation fields could cause mutation of micro-organisms, leading 
to unexpected chemical reactions and impacts. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Microbes can affect the mobility of colloidal material as 
well as influence the rate of waste package corrosion. Given present knowledge, estimates of the 
effects of microbes on corrosion processes are highly uncertain; the potential effects of mutated 
microbes are more uncertain. No analyses or experimental research have been performed to 
investigate this problem specifically. However, general principles of population genetics indicate 
that most mutations are either neutral or deleterious to the fitness of an organism and, in the 
absence of strong natural selection, are unlikely to produce any definite change in the phenotypes 
of the organisms. Thus, exclusion of effects of mutated microbes from TSPA is considered to be 
conservative. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: CLST1, ENFE2, ENFE3, ENFE4, RT1 
References: E0010 (CRWMS M&O 2000b), E0040 (CRWMS M&O 2000f) 
6.2.82 Episodic/Pulse Release from Repository  YMP 2.2.07.06.00 
FEP Description: Episodic release of radionuclides from the repository and 
radionuclide transport in the UZ may occur both because of episodic flow into the repository, and 
because of other factors including intermittent failures of waste packages. 
Note that this FEP also encompasses FEP ebs # 16 from table 3.

ANL-WIS-PA-000002 REV 00 ICN 01 83 September 2000 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Pulse releases have been screened out because a bathtub 
model, which would generate a pulse release, has been shown to be nonconservative relative to 
the flow-through model used in the EBS Radionuclide Transport Abstraction, E0095 (CRWMS 
M&0 2000q). 
TSPA Disposition: Episodic flow is explicitly included through climate change and its 
impact on seepage inflow to the drifts (boundary condition from the NFE analysis). Pulse releases 
are screened out on the basis of low consequences. 
IRSR Issues: RT1 
References: E0095 (CRWMS M&O 2000q) 
6.2.83 Redissolution of Precipitates Directs More Corrosive Fluids to Containers  YMP 
2.2.08.04.00 
FEP Description: Redissolution of precipitates that have plugged pores as a result of 
evaporation of groundwater in the hot zone, produces a pulse of fluid reaching the waste containers 
when gravity-driven flow resumes, which is more corrosive than the original fluid in the rock. 
Screening Decision: Include 
Screening Decision Basis: N/A 
Screening Argument: Re-establishment of flow will occur through the mode with 
the highest permeability, fractures through which flow persisted or which were easily unplugged. 
Plugged pores are least likely to reopen because there is no flow to dissolve the precipitates. Flow 
is likely to have chemistry associated with redissolution; however, it is still likely that the 
chemistry of the fluids will be driven by interaction with the drift liner, dissolved constituents such 
as Fe and the residual temperature of the repository. 
TSPA Disposition: The occurrence of pulses of corrosive fluids is implicit in the indrift 
water fluxes developed in E0095 (CRWMS M&O 2000q) and the water compositions 
resulting from in-drift precipitates/salts analysis in E0105 (CRWMS M&O 2000s), both 
supporting E0100 (CRWMS M&O 2000b). 
IRSR Issues: ENFE1, ENFE3, ENFE4, RT1 
References: E0095 (CRWMS M&O 2000q), E0010 (CRWMS M&O 2000b), 
E0105 (CRWMS M&O 2000s)

ANL-WIS-PA-000002 REV 00 ICN 01 84 September 2000 
6.2.84 Gas Pressure Effects  YMP 2.2.11.02.00 
FEP Description: Pressure variations due to gas generation may affect flow patterns 
and contaminant transport in the geosphere. 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: For a repository located in the UZ at Yucca Mountain, the 
connections to the atmosphere assure that a significant buildup of gas pressure is not likely. 
Studies on 2-phase flow are, however, just beginning to consider certain special aspects of the 
problem. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: RT1 
References: E0035 (CRWMS M&O 2000e) 
6.2.85 Drains  YMP 2.1.08.13.00 
FEP Description: Water accumulation in the drift would wet the invert materials, 
possibly pond, and provide a continuing source of water vapor beneath the drip shield and backfill 
for interaction with waste packages and their supports. Engineered drains are a consideration for 
mitigating such water accumulation and ponding. 
Screening Decision: Exclude 
Screening Decision Basis: Low (Zero) Probability 
Screening Argument: Drains are not part of the baseline design (CRWMS M&O 
2000ii). Thus there is less than one chance in 10,000 in 10,000 years that this FEP will occur. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low probability 
(not relevant to YMP design). 
IRSR Issues: None 
References: (CRWMS M&O 2000ii) 
6.2.86 Drainage with Transport  Sealing and Plugging  YMP 2.1.08.12.00 
FEP Description: Normal functioning of drainage in the drifts is not established, so 
how drainage will change if fractures are plugged is unclear. Suggestions include ponding until 
fractures in the wall are reached by the water level or until there is sufficient head to clear the 
fractures.

ANL-WIS-PA-000002 REV 00 ICN 01 85 September 2000 
Screening Decision: Exclude 
Screening Decision Basis: Low Consequences 
Screening Argument: Transport of contaminants to the drift floor could result in a 
layer of sediment on the floor or in blockage of the fractures in the floor. This combined with 
floor buckling could result in localized regions of water accumulation. However, the extent of 
such ponding is expected to be very small. Further, the waste packages would still sit above the 
buckled floor, and thus would not be immersed in water. Thus, the fraction of waste packages in 
continuous contact with water would be negligible and the effect on radionuclide release and 
hence dose is expected to be negligible. 
TSPA Disposition: This FEP is excluded from the TSPA on the basis of low 
consequences. 
IRSR Issues: None 
References: (CRWMS M&O 2000q)

ANL-WIS-PA-000002 REV 00 ICN 01 86 September 2000 
7. CONCLUSIONS 
Table 5 provides a summary of the EBS FEP screening decisions and the basis for "Exclude" 
decisions. 
Table 5. Summary of EBS FEP Screening Decisions 
YMP FEP # FEP Name - YMP FEP # Screening 
Decision 
Screening Basis 
YMP 1.1.02.00.00 Excavation/Construction Exclude Low 
Consequences 
YMP 1.1.02.01.00 Site Flooding (During Construction and Operation) Exclude Regulatory 
YMP 1.1.02.02.00 Effects of Preclosure Ventilation Include 
YMP 1.1.02.03.00 Undesirable Materials Left Exclude Low 
Consequences 
YMP 1.1.03.01.00 Error in Waste or Backfill Emplacement Exclude Regulatory 
YMP 1.1.07.00.00 Repository Design Include 
YMP 1.1.08.00.00 Quality Control Include 
YMP 1.1.12.01.00 Accidents and Unplanned Events During Operation Exclude Regulatory 
YMP 1.1.13.00.00 Retrievability Include 
YMP 1.2.04.03.00 Igneous Intrusion into Repository Exclude (for 
EBS) 
N/A  see DE 
PMR (a) 
YMP 2.1.03.01.00 Corrosion of Waste Containers Include Also see WP 
PMR (b) 
YMP 2.1.03.10.00 Container Healing Include Also see WP 
PMR (b) 
YMP 2.1.03.12.00 Container Failure (Long-term) Include Also see WP 
PMR (b) 
YMP 2.1.04.01.00 Preferential Pathways in the Backfill Exclude (d) Zero Probability 
(c) 
YMP 2.1.04.02.00 Physical and Chemical Properties of Backfill Exclude (d) Zero Probability 
(c) 
YMP 2.1.04.03.00 Erosion or Dissolution of Backfill Exclude Zero Probability 
(c,e) 
YMP 2.1.04.04.00 Mechanical Effects of Backfill Exclude (d) Zero Probability 
(c) 
YMP 2.1.04.05.00 Backfill Evolution Exclude (d) Zero Probability 
(c) 
YMP 2.1.04.06.00 Properties of Bentonite Exclude Zero Probability 
(c) 
YMP 2.1.04.07.00 Buffer Characteristics Exclude Zero Probability 
(c) 
YMP 2.1.04.08.00 Diffusion in Backfill Exclude Zero Probability 
(c,e) 
YMP 2.1.04.09.00 Radionuclide Transport Through Backfill Exclude Zero Probability 
(c,e) 
YMP 2.1.06.01.00 Degradation of Cementitious Materials in Drift Include 
YMP 2.1.06.02.00 Effects of Rock Reinforcement Materials Include 
YMP 2.1.06.03.00 Degradation of the Liner Exclude Zero Probability 
(c)

Table 5. Summary of EBS FEP Screening Decisions - Continued 
ANL-WIS-PA-000002 REV 00 ICN 01 87 September 2000 
YMP FEP # FEP Name - YMP FEP # Screening 
Decision 
Screening Basis 
YMP 2.1.06.04.00 Flow Through the Liner Exclude Zero Probability 
(c) 
YMP 2.1.06.05.00 Degradation of Invert and Pedestal Include 
YMP 2.1.06.06.00 Effects and Degradation of Drip Shield Include 
YMP 2.1.06.07.00 Effects at Material Interfaces Exclude Low 
Consequences 
YMP 2.1.07.01.00 Rockfall (Large Block) Exclude Low 
Consequences 
YMP 2.1.07.02.00 Mechanical Degradation or Collapse of Drift Exclude Low 
Consequences 
YMP 2.1.07.03.00 Movement of Containers Include 
YMP 2.1.07.04.00 Hydrostatic Pressure on Container Exclude Zero Probability 
(c) 
YMP 2.1.07.05.00 Creeping of Metallic Materials in the EBS Exclude Low 
Consequences 
YMP 2.1.07.06.00 Floor Buckling Exclude Low 
Consequences 
YMP 2.1.08.01.00 Increased Unsaturated Water Flux at the Repository Include 
YMP 2.1.08.02.00 Enhanced Influx (Philip's Drip) Exclude Low 
Consequences 
YMP 2.1.08.04.00 Condensation Forms on Backs of Drifts Include 
YMP 2.1.08.05.00 Flow Through Invert Include 
YMP 2.1.08.06.00 Wicking in Waste and EBS Include 
YMP 2.1.08.07.00 Pathways for Unsaturated Flow and Transport in the Waste and EBS Include 
YMP 2.1.08.08.00 Induced Hydrological Changes in the Waste and EBS Include 
YMP 2.1.08.09.00 Saturated Groundwater Flow in Waste and EBS Exclude Low 
Consequences 
YMP 2.1.08.11.00 Resaturation of Repository Include 
YMP 2.1.09.01.00 Properties of the Potential Carrier Plume in the Waste and EBS Include 
YMP 2.1.09.02.00 Interaction with Corrosion Products Include 
YMP 2.1.09.05.00 In-drift Sorption Exclude Low 
Consequences 
YMP 2.1.09.06.00 Reduction-oxidation Potential in Waste and EBS Include 
YMP 2.1.09.07.00 Reaction Kinetics in Waste and EBS Exclude Low 
Consequences 
YMP 2.1.09.08.00 Chemical Gradients/Enhanced Diffusion in Waste and EBS Exclude Low 
Consequences 
YMP 2.1.09.11.00 Waste-Rock Contact Exclude Low 
Consequences 
YMP 2.1.09.12.00 Rind (Altered Zone) Formation in Waste, EBS, and Adjacent Rock Include 
YMP 2.1.09.13.00 Complexation by Organics in Waste and EBS Exclude Low 
Consequences 
YMP 2.1.09.14.00 Colloid Formation in Waste and EBS Include 
YMP 2.1.09.15.00 Formation of True Colloids in Waste and EBS Exclude Low 
Consequences 
YMP 2.1.09.16.00 Formation of Pseudo-colloids (Natural) in Waste and EBS Include

Table 5. Summary of EBS FEP Screening Decisions - Continued 
ANL-WIS-PA-000002 REV 00 ICN 01 88 September 2000 
YMP FEP # FEP Name - YMP FEP # Screening 
Decision 
Screening Basis 
YMP 2.1.09.17.00 Formation of Pseudo-colloids (Corrosion Products) in Waste and EBS Include 
YMP 2.1.09.18.00 Microbial Colloid Transport in the Waste and EBS Exclude Low 
Consequences 
YMP 2.1.09.19.00 Colloid Transport and Sorption in the Waste and EBS Exclude Low 
Consequences 
YMP 2.1.09.20.00 Colloid Filtration in the Waste and EBS Exclude Low 
Consequences 
YMP 2.1.09.21.00 Suspensions of Particles Larger than Colloids Exclude Low 
Consequences 
YMP 2.1.10.01.00 Biological Activity in Waste and EBS Include 
YMP 2.1.11.01.00 Heat Output / Temperature in Waste and EBS Include 
YMP 2.1.11.03.00 Exothermic Reactions in Waste and EBS Exclude Low 
Consequences 
YMP 2.1.11.04.00 Temperature Effects / Coupled Processes in Waste and EBS Include 
YMP 2.1.11.05.00 Differing Thermal Expansion of Repository Components Exclude Low 
Consequences 
YMP 2.1.11.07.00 Thermally-induced Stress Changes in Waste and EBS Include 
YMP 2.1.11.08.00 Thermal Effects: Chemical and Microbiological Changes in the 
Waste and EBS 
Include 
YMP 2.1.11.09.00 Thermal Effects on Liquid or Two-phase Fluid Flow in the Waste and 
EBS 
Include 
YMP 2.1.11.10.00 Thermal Effects on Diffusion (Soret effect) in Waste and EBS Exclude Low 
Consequences 
YMP 2.1.12.01.00 Gas Generation Exclude Low 
Consequences 
YMP 2.1.12.02.00 Gas Generation (He) from Fuel Decay Exclude Low 
Consequences 
YMP 2.1.12.03.00 Gas Generation (H2) from Metal Corrosion Exclude Low 
Consequences 
YMP 2.1.12.04.00 Gas Generation (CO2, CH4, H2S) from Microbial Degradation Exclude Low 
Consequences 
YMP 2.1.12.05.00 Gas Generation from Concrete Exclude Low 
Consequences 
YMP 2.1.12.06.00 Gas Transport in Waste and EBS Exclude Low 
Consequences 
YMP 2.1.12.07.00 Radioactive Gases in Waste and EBS Exclude (for 
EBS) 
Low 
Consequences 
YMP 2.1.12.08.00 Gas Explosions Exclude Low 
Consequences 
YMP 2.1.13.01.00 Radiolysis Exclude (for 
EBS) 
N/A  see WF 
PMR (a) 
YMP 2.1.13.02.00 Radiation Damage in Waste and EBS Exclude Low 
Consequences 
YMP 2.1.13.03.00 Mutation Exclude Low 
Consequences 
YMP 2.2.07.06.00 Episodic / Pulse Release from Repository Include (also see NFE 
PMR) 
YMP 2.2.08.04.00 Redissolution of Precipitates Directs More Corrosive Fluids to 
Containers 
Include 
YMP 2.2.11.02.00 Gas Pressure Effects Exclude Low 
Consequences

Table 5. Summary of EBS FEP Screening Decisions - Continued 
ANL-WIS-PA-000002 REV 00 ICN 01 89 September 2000 
YMP FEP # FEP Name - YMP FEP # Screening 
Decision 
Screening Basis 
YMP 2.1.08.13.00 Drains Exclude Zero Probability 
(c) 
YMP 2.1.08.12.00 Drainage with Transport  Sealing and Plugging Exclude Low 
Consequences 
(a)  While the identified FEP may be important for TSPA, it is not important to modeling of the EBS. 
(b)  These are primarily WP FEPs; the EBS analysis merely provides the appropriate boundary conditions. 
(c)  This potential repository feature is not part of the current baseline design (CRWMS M&O 2000ii). 
(d)  Should backfill be included in the design, this decision would change from Exclude to Include. 
(e)  Should backfill be included in the design, this screening basis would change from Probability to Consequences. 
This document may be affected by technical product input information that requires confirmation. 
Any changes to the document that may occur as a result of completing the confirmation activities 
will be reflected in subsequent revisions. The status of the input information quality may be 
confirmed by review of the Document Input Reference System database.

ANL-WIS-PA-000002 REV 00 ICN 01 90 September 2000 
8. INPUTS AND REFERENCES 
8.1 DOCUMENTS CITED 
Cranwell, R.M.; Guzowski, R.W.; Campbell, J.E.; and Ortiz, N.R. 1990. Risk Methodology for 
Geologic Disposal of Radioactive Waste: Scenario Selection Procedure. NUREG/CR-1667. 
Washington, D.C.: U.S. Nuclear Regulatory Commission. ACC: NNA.19900611.0073. 
CRWMS M&O 1995a. Total System Performance Assessment - 1995: An Evaluation of the 
Potential Yucca Mountain Repository. B00000000-01717-2200-00136 REV 01. Las Vegas, 
Nevada: CRWMS M&O. ACC: MOL.19960724.0188. 
CRWMS M&O 1995b. Waste Isolation Evaluation: Tracers, Fluids, and Materials, and 
Excavation Methods for Use in the Package 2C Exploratory Studies Facility Construction. 
BABE00000-01717-2200-00007 REV 04. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.19950721.0172. 
CRWMS M&O 1999a. EBS FEPs/Degradation Modes Abstraction. TDP-WIS-PA-000002 REV 
00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19991117.0158. 
CRWMS M&O 1999b. License Application Design Selection Report. B00000000-01717-4600- 
00123 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19990511.0325. 
CRWMS M&O 1999c. In Drift Corrosion Products. ANL-EBS-MD-000041 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.20000106.0438. 
CRWMS M&O 1999d. Conduct of Performance Evaluation. Activity Evaluation, September 30, 
1999. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19991028.0092. 
CRWMS M&O 2000a. Invert Diffusion Properties Model. ANL-EBS-MD-000031 REV 01. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000912.0208. 
CRWMS M&O 2000b. Physical and Chemical Environment Abstraction Model. ANL-EBSMD-
000046 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000523.0155. 
CRWMS M&O 2000c. Engineered Barrier System Features, Events and Processes and 
Degradation Modes Analysis. ANL-EBS-MD-000035 REV 00 ICN 01. Las Vegas, Nevada: 
CRWMS M&O. ACC: MOL.20000727.0092. 
CRWMS M&O 2000d. Seepage/Backfill Interactions. ANL-EBS-MD-000039 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.20000509.0243.

ANL-WIS-PA-000002 REV 00 ICN 01 91 September 2000 
CRWMS M&O 2000e. In Drift Gas Flux and Composition. ANL-EBS-MD-000040 REV 00. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000523.0154. 
CRWMS M&O 2000f. In-Drift Microbial Communities. ANL-EBS-MD-000038 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.20000331.0661. 
CRWMS M&O 2000g. In-Drift Colloids and Concentrations. ANL-EBS-MD-000042 REV 00. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000509.0242. 
CRWMS M&O 2000h. EBS Radionuclide Transport Model. ANL-EBS-MD-000034 REV 00 
ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000727.0091. 
CRWMS M&O 2000i. Seepage/Cement Interactions. ANL-EBS-MD-000043 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.20000317.0262. 
CRWMS M&O 2000j. Seepage/Invert Interactions. ANL-EBS-MD-000044 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.20000523.0156. 
CRWMS M&O 2000k. In-Drift Thermal-Hydrological-Chemical Model. ANL-EBS-MD- 
000026 REV 00 ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000802.0011. 
CRWMS M&O 2000l. Water Drainage Model. ANL-EBS-MD-000029 REV 00 ICN 01. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.20000705.0095. 
CRWMS M&O 2000m. Ventilation Model. ANL-EBS-MD-000030 REV 00. Las Vegas, 
Nevada: CRWMS M&O. ACC: MOL.20000107.0330. 
CRWMS M&O 2000n. Drift Degradation Analysis. ANL-EBS-MD-000027 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.20000107.0328. 
CRWMS M&O 2000o. Water Diversion Model. ANL-EBS-MD-000028 REV 00. Las Vegas, 
Nevada: CRWMS M&O. ACC: MOL.20000107.0329. 
CRWMS M&O 2000p. Water Distribution and Removal Model. ANL-EBS-MD-000032 REV 
00 ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000822.0006. 
CRWMS M&O 2000q. EBS Radionuclide Transport Abstraction. ANL-WIS-PA-000001 REV 
00 ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000821.0358. 
CRWMS M&O 2000r. Engineered Barrier System: Physical and Chemical Environment Model. 
ANL-EBS-MD-000033 REV 00 ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000807.0093. 
CRWMS M&O 2000s. In-Drift Precipitates/Salts Analysis. ANL-EBS-MD-000045 REV 00. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000512.0062.

ANL-WIS-PA-000002 REV 00 ICN 01 92 September 2000 
CRWMS M&O 2000t. Multiscale Thermohydrologic Model. ANL-EBS-MD-000049 REV 00. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000609.0267. 
CRWMS M&O 2000u. Abstraction of NFE Drift Thermodynamic Environment and Percolation 
Flux. ANL-EBS-HS-000003 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000504.0296. 
CRWMS M&O 2000v. Waste Form Colloid-Associated Concentration Limits: Abstraction and 
Summary. ANL-WIS-MD-000012 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000525.0397. 
CRWMS M&O 2000w. In-Package Chemistry Abstraction. ANL-EBS-MD-000037 REV 00. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000418.0818. 
CRWMS M&O 2000x. Miscellaneous Waste-Form FEPs. ANL-WIS-MD-000009 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.20000526.0339. 
CRWMS M&O 2000y. Features, Events, and Processes in Thermal Hydrology and Coupled 
Processes. ANL-NBS-MD-000004 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000602.0053. 
CRWMS M&O 2000z. Disruptive Events FEPS. ANL-WIS-MD-000005 REV 00. Las Vegas, 
Nevada: CRWMS M&O. ACC: MOL.20000501.0227. 
CRWMS M&O 2000aa. Abstraction of Drift Seepage. ANL-NBS-MD-000005 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.20000322.0671. 
CRWMS M&O 2000bb. Features, Events, and Processes in UZ Flow and Transport. ANLNBS-
MD-000001 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000502.0240. 
CRWMS M&O 2000cc. WAPDEG Analysis of Waste Package and Drip Shield Degradation. 
ANL-EBS-PA-000001 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000526.0332. 
CRWMS M&O 2000dd. FEPS Screening of Processes and Issues in Drip Shield and Waste 
Package Degradation. ANL-EBS-PA-000002 REV 00. Las Vegas, Nevada: CRWMS M&O. 
ACC: MOL.20000526.0334. 
CRWMS M&O 2000ee. Environment on the Surfaces of the Drip Shield and Waste Package 
Outer Barrier. ANL-EBS-MD-000001 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000328.0590.

ANL-WIS-PA-000002 REV 00 ICN 01 93 September 2000 
CRWMS M&O 2000ff. Incorporation of Uncertainty and Variability of Drip Shield and Waste 
Package Degradation in WAPDEG Analysis. ANL-EBS-MD-000036 REV 00. Las Vegas, 
Nevada: CRWMS M&O. ACC: MOL.20000526.0333. 
CRWMS M&O 2000gg. Subsurface Facility System Description Document. SDD-SFS-SE- 
000001 REV 01. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000807.0078. 
CRWMS M&O 2000hh. Ground Control System Description Document. SDD-GCS-SE-000001 
REV 01. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000803.0355. 
CRWMS M&O 2000ii. Monitored Geologic Repository Project Description Document. TDRMGR-
SE-000004 REV 01 ICN 02. Las Vegas, Nevada: CRWMS M&O. Submit to RPC. 
URN-0529. 
CRWMS M&O 2000jj. Design Analysis for UCF Waste Packages. ANL-UDC-MD-000001 REV 
00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000526.0336. 
CRWMS M&O 2000kk. Design Analysis for the Defense High-Level Waste Disposal Container. 
ANL-DDC-ME-000001 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000627.0254. 
CRWMS M&O 2000ll. Design Analysis for the Naval SNF Waste Package. ANL-VDC-ME- 
000001 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000615.0029. 
CRWMS M&O 2000mm. Design Analysis for the Ex-Container Components. ANL-XCS-ME- 
000001 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000525.0374. 
CRWMS M&O 2000nn. The Development of Information Catalogued in Revision 00 of the YMP 
FEP Database. TDR-WIS-MD-000003 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000705.0098. 
DOE (U.S. Department of Energy) 1996. Title 40 CFR Part 191 Compliance Certification 
Application for the Waste Isolation Pilot Plant. DOE/CAO-1996-2184. Carlsbad, New 
Mexico: U.S. Department of Energy, Carlsbad Area Office. TIC: 240511. 
Philip, J.R., Knight, J.H., and Waechter, R.T. 1989. Unsaturated Seepage and Subterranean 
Holes: Conspectus, and Exclusion Problem for Circular Cylindrical Cavities. Water Resources 
Research, 25, (1), 16-28. Washington, D.C.: American Geophysical Union. TIC: 239117. 
SAM (Safety Assessment Management) n.d. Safety Assessment of Radioactive Waste 
Repositories, An International Database of Features, Events and Processes. Unpublished Draft, 
June 24, 1997. ACC: MOL.19991214.0522. 
Skagius, K. and Wingefors, S. 1992. Application of Scenario Development Methods in 
Evaluation of the Koongarra Analogue. Volume 16 of Alligator Rivers Analogue Project. SKI

ANL-WIS-PA-000002 REV 00 ICN 01 94 September 2000 
TR 92:20-16. DOE/HMIP/RR/92/086. Manai, New South Wales, Australia: Australian Nuclear 
Science and Technology Organisation. TIC: 231268. 
8.2 CODES, STANDARDS, REGULATIONS, AND PROCEDURES 
64 FR 8640. Disposal of High-Level Radioactive Wastes in a Proposed Geologic Repository at 
Yucca Mountain, Nevada. Proposed Rule. Readily Available. 
64 FR 46976. Environmental Radiation Protection Standards for Yucca Mountain, Nevada; 
Proposed Rule 40 CFR 197. Readily Available. 
AP-3.10Q, Rev. 2, ICN 3. Analyses and Models. Washington, DC: U.S. Department of Energy, 
Office of Civilian Radioactive Waste Management. ACC: MOL.20000918.0282. 
AP-SI.1Q, Rev. 2, ICN 4. Software Management. Washington, DC: U.S. Department of Energy, 
Office of Civilian Radioactive Waste Management. ACC: MOL.20000223.0508. 
AP-SV.1Q Rev. 0, ICN 2. Control of the Electronic Management of Data. Las Vegas, Nevada: 
CRWMS M&O. ACC: MOL.20000831.0065. 
DOE 2000. Quality Assurance Requirements and Description. DOE/RW-0333P, Rev. 10. 
Washington, D.C.: U.S. Department of Energy, Office of Civilian Radioactive Waste 
Management. ACC: MOL.20000427.0422. 
Dyer, J.R. 1999. "Revised Interim Guidance Pending Issuance of New U. S. Nuclear Regulatory 
Commission (NRC) Regulations (Revision 01, July 22, 1999), for Yucca Mountain, Nevada." 
Letter from J.R. Dyer (DOE/YMSCO) to D.R. Wilkins (CRWMS M&O), September 3, 1999, 
OL&RC:SB-1714, with enclosure, "Interim Guidance Pending Issuance of New NRC Regulations 
for Yucca Mountain (Revision 01)" . ACC: MOL.19990910.0079. 
NLP-2-0, Rev. 5, Determination of Importance Evaluations, Las Vegas, Nevada: CRWMS 
M&O. ACC: MOL.19981116.0120. 
NRC (U.S. Nuclear Regulatory Commission) 1998a. Issue Resolution Status Report Key 
Technical Issue: Total System Performance Assessment and Integration. Rev. 1. Washington, 
D.C.: U.S. Nuclear Regulatory Commission. ACC: MOL.19990105.0083. 
NRC 1998b. Issue Resolution Status Report Key Technical Issue: Container Life and Source 
Term. Rev. 1. Washington, D.C.: U.S. Nuclear Regulatory Commission. 
ACC: MOL.19990105.0081. 
NRC 1999a. Issue Resolution Status Report Key Technical Issue: Thermal Effects on Flow. 
Rev. 2. Washington, D.C.: U.S. Nuclear Regulatory Commission. ACC: MOL.19991021.0156.

ANL-WIS-PA-000002 REV 00 ICN 01 95 September 2000 
NRC 1999b. Issue Resolution Status Report Key Technical Issue: Evolution of the Near-Field 
Environment. Rev. 2. Washington, D.C.: U.S. Nuclear Regulatory Commission. ACC: 
MOL.19990810.0640. 
NRC 1999c. Issue Resolution Status Report Key Technical Issue: Unsaturated and Saturated 
Flow Under Isothermal Conditions. Rev. 2. Washington, D.C.: U.S. Nuclear Regulatory 
Commission. ACC: MOL.19990810.0641. 
NRC 1999d. Issue Resolution Status Report Key Technical Issue: Structural Deformation and 
Seismicity. Rev. 2. Washington, D.C.: U.S. Nuclear Regulatory Commission. 
ACC: MOL.19991214.0623. 
NRC 1999e. Issue Resolution Status Report Key Technical Issue: Repository Design and 
Thermal-Mechanical Effects. Rev. 2. Washington, D.C.: U.S. Nuclear Regulatory Commission. 
ACC: MOL.20000306.0670. 
NRC 1999f. Issue Resolution Status Report Key Technical Issue: Radionuclide Transport. 
Rev. 1. Washington, D.C.: U.S. Nuclear Regulatory Commission. ACC: MOL.19991214.0621. 
QAP-2-0, Rev. 5, ICN 1. Conduct of Activities. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.19991109.0221. 
QAP-2-3, Rev. 10, Classification of Permanent Items, Las Vegas, Nevada: CRWMS M&O. 
ACC: MOL.19990316.0006. 
Reamer, C. W. 1999. Issue Resolution Status Report (Key Technical Issue: Igneous Activity, 
Revision 2). Letter from C.W. Reamer (NRC) to Dr. S. Brocoum (DOE), July 16, 1999, with 
enclosure. ACC: MOL.19990810.0639.