Free Response to Motion - District Court of Federal Claims - federal

Case 1:98-cv-00474-JFM

Document 309-8

Filed 04/16/2004

Page 1 of 14
Reference Design

Repository

closing
and prevent water from entering through
these openings. ,

for disposal , future generations would make

Even under the most ambitious schedules

the fin~l decision to close a repository. To give future generations the option of closing the repository or monitoring it for long

At the surface, all radiological areas would be decontaminated, all structures removed
and all wastes and debris disposed of at approved sites. The surface area would be restored as closely as possible to its origi-

periods of time, DOE is designing the repository so that it could (with Nuclear Regulatory Commission approval) be either closed as early as 10 years after emplacement of the last waste package , or kept open for hundrods oryears from the start of waste

nal condition. Permanent monumen
would be erected around the site to warn any future generations of the presence and

emplacement.

nature of the buried wastes.

Permanently. closing the.repository would
require the sealing of all shafts , ramps, ex-

The DOE also would continue to oversee the

, Yucca Mountain site to prevent any activity that could

ploratory boreholes , and other underground openings. ' These actions would discourage any human intrusion into the repository

breach a repository s engineered or geologic barriers, ' or otherwise

increase the exposure of the public to radiation beyond allowable limits.

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Case 1:98-cv-00474-JFM
Performance Assessment

Document 309-8

Filed 04/16/2004

Page 2 of 14

Performance assessment models
Perforo\ance assessment evaluates how a

system are most important to how well it is

repository system is likely to work over long time periods, From the results of scientific studies , analysts build detailed mathematical models or "representations" of the fea-

likely to work , and where scientists and engineers might most usefully focus their , efforts to improve performance, These assess-

tures, events, and processes that could af. feet the performance of the design. They then incorporate the results of these detailed process models into an overall model
of the l'(!pository system , which is called the

ments are repeated and refined during the course of developing, evaluating, and improving a repository design.
A total system performanCE! assessment represents a reasonable approach to the challenging task of projecting how a repository would work over thousands of years. However~ as a National

total system performance assessment
model. The models arc used to assess how
the natural and engineered elements of a

Academy of Sciences

waste disposal system are likely to work
together ovm' the long period required to

panel observed, "Confidenc:e in the disposal

techniques must come from a combination

isolate wastes.

Performance assessments help identify
which uncertainties about the behavior of a disposal system are significant and which are not, which elements of the repository

of remoteness, engineering design, math. ematical modeling, performance assessment, natural analogues and the possibil. ity of remedial , action in the event. of unforeseen events."17 The DOE is taking

this combined approach.

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Approach to construding a total system perfOnt13l1q! assessment (TSPA) model. Analysts
develop detailed mathematical models of the natural processes that are importantto repository

perfonnance and then combine these models Into a model of the entire repository system.

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Case 1:98-cv-00474-JFM

Document 309-8

Filed 04/16/2004

Page 3 of 14

Performance Assessment

The attributes of safe disposal
The results of fifteen years of testing and

analysis, including four years of underground exploration , have validated many, but not aU, of the expectations of scientists

The results indicate that a repository at Yucca Mountain would need to exhibit four
key attributes to protect public health and

the environment for thousands of years.
The four key attributes are:
. Limited water contact with waste pack-

who first suggested -that remote desert re~ gions are wen-suited for a geologic repository. One important and U11expeeted test
result was finding underground, at the level

ages
. Long waste package
. Low rate

of the proposed repository, traces of a radioactive isotope (chlorine- 36)
that is asso-

lifetime

ciated with . above- ground nuclear weapons
tests, As atmospheric nuclear testing

be-

of release of1'8dionuclides from

. , gan in the mid- 1940s , this finding suggests that. some watel' travels from the ground

breached waste packages
. Reduction in the

surface to the level of the repository in about 50 )' cars or less. Another important finding was evidence that the average amount

conCtmtration of radio, nuclides as they are transported from
breached waste packages

mountain ~s about a third of an inch per , year, which, while only about five percent
of the average annual precipitation, is more than DOE initially expected. Taken together, th(~ findings , both expected and un-

of water that filters down through the

Based on performance assessment models DOE has evaluated the degree to which th~

reference design exhibits these four key at-

tributes, and has identified additional scientific studies and design improvements
that could reduce uncertainties and enhance long- term repository perrormance.

expected, underscore the importance of
building engineered barriers that work with

the natural barriers to keep water away
from the waste.

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Case 1:98-cv-00474-JFM
Performance Assessment

Document 309-8

Filed 04/16/2004

Page 4 of 14

Limited water contact with waste packages
In the rererence design ,

waste packages

would be placed about 1, 000 feet below the mountain s surface and about 1 000 feet

Once waste packages have been placed in the repository, the heat generated from radioactive decay would raise the temperature in the tunnels above the boiling point of water. The heat is expected to dry out th~ surrounding rock and drive any water

above the water table, Even if future cli-

mates are much wetter than today, the
mountain is not expected to erode and leave

the waste exposed, and the water table is not expected to rise high enough to reach
the waste.

away for hundreds to thousands of years.
However, as the waste decays and the reo pository cools, enough water to cause drips

would begin to seep into the drifts through
In the current semiarid climate, about seven inches of water a ' year from rain and snow fall on Yucca Mountain, Nearly all of that precipitation, about 95 perc~nt, runs off or evaporates, Only about one- third of an inch , of water per year moves down (or percolates) through the nearly 1, 000 feet of rock to reach the level of the repository. Studies of past climates indicate that the precipitation , may increase to a long- term average of about 12 inches per year, However , most
of the water still would run off or evaporate
rather than soak into the ground.
fractures in the roc

k,

Using mathematical models ,

analysts esti-

mate that, after the ' repository cools enough, about five percent of the packages could experience dripping water, under the current climate, If the climate changes to a wetter long- term average about 30 percent of the packages could experience dripping water. These estimates are based on a number of assumptions that remain to be validated. Nonetheless , the results suggest that limited water would contact the waste pack.

ages.
Ongoing testing in the exploratory tunnels is providing more information on how much
water could enter the repository and con-

tact. the waste packages under a variety of conditions, The DOE is also evaluating alternative waste package designs and other options that wouJd mitigate the effects of

a repository.

water contact and improve performance of

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Case 1:98-cv-00474-JFM

Document 309-8

Filed 04/16/2004

Page 5 of 14

Performance Assessment

Long waste package lifetime
The waste package in the reference design has two layers: a thick outer layer made of

carbon steel that provides structural
strength and delays any contact of water with the inner layer , and a thinner inner layer of a high-nickel alloy that resists corrosion after the outer layer is penetrated. '
Based on preJiminary results of corrosion

that dripping water could cause the first penetrations-tiny pinholes-to appear in some waste packages after about 4 000
years. More substantial-penetrations could

begin to occur about 10 000 years later. Projeetions of waste package performance also assume that at least one waste package will fail in 1 000 years due to a manufacturing defect,

experiments and the opinions of experts,
, computer simulations indicate that most of

To redu~ the uncertainty in waste

pack-

the waste packages would last more thaJ,1 000 years , even if water is dripping on
them. The longevity of man-made materi-

age performance , further research on ' the conditions that waste packages will ' be ex-

als in the repository environment over such
long periods of time is subject to significant

posed to and testing of waste package materials is ' underway. In addition , DOE is
evaluating alternative waste,

package de-

uncertainty, however, and some wa.ste packages could fail earlier. Scientists estimate

signs and materials that could compensate for the uncertainty and enhance longevity,

ArTlargosa Valley

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Case 1:98-cv-00474-JFM

Document 309-8

Filed 04/16/2004

Page 6 of 14

Performance Assessment

Low rate of release

of radionuclides from

breached waste packages
During the thousands of years required for water to reach ,the waste, the radioactivity

Once water enters a waste package, it would
have to penetrate the metal cladding of the spent nuclear fuel to reach th~ waste. For about 99 percent the commercial spent of nuclear fuel, the cladding is highly corrosion-resistant metal that is designed to

of most of the radionuelides would decay to

withstand the extreme temperature and ra. diation environment in the core of an operating nuclear reactor. Current models in. dicate that it would take thousands of years to corrode dadding sufficiently to allow
water to reach the waste and begin to dis-

solve the radi9nuclides. However, estimates of cladding performance are uncertain , and more work in this area is planned.

virtually zero. For the remaining radionuelides to get out of the waste package, they must be dissolved in water, but few of the remaining radionuclides could be dissolved in water at a significant rate. Thus , only the long-lived , water-soluble radionuclides such as isotopes of technetium, iodine, neptunium , and uranium , could get ou~ of the waste package. Although most ofthe waste would not migrate from tl\e package even . if it were breached, the release of any radionuclides is reason for concern and moti. vation for seeking improvements in the reo pository design. Ongoing tests are providing more information on how radio. nuclides dissolve in water.

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Case 1:98-cv-00474-JFM

Document 309-8

Filed 04/16/2004

Page 7 of 14

Performance Assessment

Reduction in the concentration the waste packages

of

radionuclides as' they are transported from
transported by moving groundwater because they do not adsorb well to minerals. Two isotopes-plutonium- 239 and plutonium- 242- tend to adsorb but could be mobile because they can attach themselves
to small particles (or colloids) and then be

Long- lived, water-soluble radionuclides that migrate from the waste packages will
, l.ave to move down through about 1, 000
feet

of rock to the water table and then travel about 20 kilometers (about 12 miles) to
reach a point where they could be taken up

in ~ well and consumed or used to irrigate crops.
As the long- lived, water-soluble radiom
elides begin to move down through the roCk

transported along with those particles.
Given the uncertainty about the rate at which groundwater moves and the posSible

existence of fast pathways or channels
through the saturated zone, the DOE is con-

some will stick (or adsorb) to the minerals in the rock and be delayed in reaching the water table. After reaching the water table, radionuclides will disperse to some extent in the larger volume o(groundwater beneath Yucca Mountain , and the concentrations ""HI be diluted. Eventually, ground-

tinuing to investigate groundwater flow
characteristics and is analyzing the possible effeets on radionuc1ide transport and dilution. '

water with varying concentrations of
differmt radio nuclides will reach locations

near Yucca Mountain where the water could
be consumed.

Of the approximately 350 different radio. active isotopes present in spent nuclear fuel and high- level radioactive waste, six are present in sufficient quantities and are sufficiently long- lived , soluble, mobile, and
hazardous to contribute significantly to calculated radiation exposures, Four of these

isotopes- technetium- 99,

iodine- 129,

nep-

tunium- 237 , and uranium- 234-can be

Amargosa Valley

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Case 1:98-cv-00474-JFM
Performance Assessment

Document 309-8

Filed 04/16/2004

Possible dose
Analysts have calculated the possible radiation dose rate to people who may be living near the repository thousands of years in
Radiation is a form of energy that is everywhere

the future, Because where and how people will be living in the distant future cannot
be predicted , analysts base their calculations on the current situation,

in the natural and man-made world. The basic
unit for measuring the damage that a given dOse of radiation can cause to human tissue Is called a rem, Each year in the United States, the average person recehfes a dose of about 360 millirem (a millirem is one one-thousandth of a rem)

They assume

that the nearest population

lives 20 kilo-

meters (about 12 miles) from the repository

from natura' and man-made sources. Natural

boundary and has a lifestyle similar to the average ' person living today in Amargosa
Valley, about 30 kilometers (about 19 miles)

sources-cosmlc rays, radon gas, soil and rock. and the human body Itself-account for aboUt
300 mlilirem of the total annual average dose,

from Yucca Mountain.
During the first 10, 000 years after the repository is closed , current models indicate that the mean peak annual dose rate to an
average individual in this futw' e ))opulation would be about 0. millirem. However, , given the uncertainties associated wit:h the assumptions and the performance assessment models, the peak dose could be higher
or lower than the estimated average, There

with man-made, mosUy m~ical , sources ae:-

counting (or the remaining 60 millirem. 18 Manmade souroes of radiation include diagnOstic Xrays and other medioal procedures, television sets, and computer monitors. Radiation exposures vary widely depending on geographic location and life choices. For example, a person ' ColOliving at an altitude 0(5,000 foot in Denver, rado. receives nearly two times as much cosmic radiation as a person living near sea level in Washington. D.

is a 5 percent (1 in 20) chance of exceeding
8 millirem and a greater than 25 percent chance of no exposure at alL

During the first 1 million years , the mean
peak annual dose rate to an average individual is estimated to reach 200 millirem, with a 5 percent chance of exceeding 1 000
mi1lirem (or 1 rem) and a 5 percent chance

During the first 100, 000 years, the mean peak annual , dose rate to an average individual is estimated to be 30 millirem with
a 5 percent chance of exceeding 200 mil.

of zero dose,

liTem and a greater than 20 percent chance

of being lower than 0. 07

millirem,

360 mrem

average pl'flent-d.y , exposure
000,000 Y'."

1;,

01 mrem

1 mrem

0 mrem

10mrem

100 mrem

1000 mrem or 1 rem

10 rem

Mean peak annual dose rate from the repository

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Case 1:98-cv-00474-JFM

Document 309-8

Filed 04/16/2004

Page 9 of 14

Performance Assessment

Other safety issues
The analysis of the safety of a repository at
Yucca Mountain must also consider both the
plore for gold ,

likelihood and the effect of possible disrup. tive processes and events , such as volcanism , earthquakes , human intrusion , and nuclear criticality, " The DOE has concluded that there is little likelihood that
Yucca Mountain would significantly affeet the long- term . performance of a repository,
such processes or events at

ture generations to drill or otherwise exhydrocarbons , or other materials,

The National Academy of Sciences (NAS)

scientific basis for predicting such human activities over the very long periods of time for which the repository must function. The NAS, there. fore , recommended that future human in.
concluded that there is no
trusion not be considered in the quantita-

Volcanism
The area aroun-d Yucca Mountain was
very
active volcanically millions of years ago,

tive performance assessments, However to evaluate how the repository would p erform ir humans were to intrude, the NAS recommended, 2O and DOg has conducted, a

The rock of Yucca Mountain--called tuffis compos(!d of volcanic ash from eruptions that occurred about 13 million years ago,

separate analysis of a theoretical casein which a waste package is penetrated by
someone drilling into the repository in the

However , large-scale volcanism in the area
ceased about 7. 5 million years ago, and the

future, Performance assessments indicate that peak dose rates would increase if a
waste package were penetrated by explor-

last, smalJ eruption occurred about 75 000
years ago. Experts have concluded that the

chance of future volcanic activity disrupting the site is negligible. As a result, volcanism would be unlikely to affect the long-

atory drilling and if waste were then carried down the drillhole to the water table,
However, as not.ed, natural resource assessments indicate that the Yucca Mountain

term performance of the repository,

site does not exhibit characteristics that
would make it an attractive location for exploratory drilling.

Earthquakes
. Yucca Mountain is located in the southern

Nuclear criticality
A nuclear criticality occurs when sufficient , quantities of fissionab)e materials come together in a precise manner and the required

Great Basin, a large region that has some
earthquakes. Yucca Mountain itself is ' a , tilted block of rock that is bounded by geo-

logic faults. A magnitude 5, 6 earthquake occurred about 12 miles away in 1992, A reposi tory and surface facilities would be designed to withstand earthquakes , as are modern tunnels , buildings , and power
plants in seismically active areas.

conditions exist to start and sustain a
nuclear chain reaction. The waste packages would be designed to prevent a criticality
from occurring inside a waste package, In
. addition , it is very unlikely that a sufficient quantity of fissionable materials could ac-

Accidental human intrusion
It is possible that future human activities
might intrude on the repository: One pos-

sible activity would be exploration for valuable natural resources, However, Yucca Mountain exhibits few characteristics that would make it an attractive location for fu-

cumulate outside of the waste packages in the precise configuration and with the required conditions to create a criticality. If somehow , an external criticality were to occur , analyses indicate that it would have

only minor effects on repository performance. An explosive external criticality is
not credible.

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Case 1:98-cv-00474-JFM

Document 309-8

Filed 04/16/2004

Page 10 of 14

Performance Assessment

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W~at we are learning
The performance assessment shows that the most significant single factor affecting the ability of the repository to protect public health and safety would be the amount of water that directly contacts the waste. Yucca Mountain itself would provide the first major barrier to such contact, ensuring that the repository would not be fl~ded by either a rise in the deep water table or by infiltration of water from the surface during
periods much wetter than the present. However, some waste packages I wHl' experience, dripping water, and the amount is uncertain.
To address this concern , the reference design includes multiple barriers

to limit water contact with the waste. The inner and outer waste package layers and the metal cladding on the spent fuel are barriers between
water and the waste.

rhe vast majority of the radionuclides in the waste are not mobile in water and thus pose no threat to public health and safety, even when the waste package and cladding are breached and the waste is exposed to
water. However, a very small fraction of the radionuc1ides (representing

less than 0. 2 percent of the initial radioactivity of all the radionuclides) are able to dissolve and move. While ~he quantities of the radionuclides that could reach the environment appear to be small. they nevertheless pose a potential health hazard that must be addressed.
Total system performance assessments of the reference design indicate that, for 10, 000 years after the repository is closed, people living near Yucca Mountain would receive ' little or no increase in radiation expo. sure. After about 300, 000 years, people living about 20 kilometers (12 miles) south of Yucca Mountain might reeeive additional radiation doses that are comparable to present- day doses from natural background radiation.

Although the performance assessments are encouraging, there are reo maining uncertainties that should be addressed before a site recommendation decision is made and a license application is submitted to the Nuclear Regulatory Commission, Therefore , DOE plans to co.nduct further tests of the site and of candidate waste package materials in support of the license application. The DOE also plans to evaluate alterna-

tive repository designs that could reduce the possible doses
living near Yucca Mountain thousands of years in the future.

to people

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Case 1:98-cv-00474-JFM

Document 309-8

Filed 04/16/2004

Page 11 of 14
License Application

Plan to compl~te a license application
In the next four years, DOlt; will focus on
, improving the
1'0

obtain an NltC license, DO~ must dem-

repository and waste package design, strengthening the understanding of the key natural processes, preparing the environmental impact statement , and developing the information needed to support the site reeommendation decision. Be-

onstrate that a repository can be con-

structed, operated , monitored, and eventually closed without unreasonable risk to the health and safety of workers and the pub-

lic. The challenge

in licensing a geologic

, cause a license application takes years to

repository is demonstrating a reasonable assurance of compliance with long-term safety

prepare, DOE has begun to assemble the information needed to support one.
Before DOE can submit a license application to the Nuclear Regulatory Commission

standards for many thousands of years.
However, the recent issuance of a permit
by the Environmental Protection Agency for the disposal oflong-lived transuranic waste

in the Waste Isolation Pilot Plant shows
that cQmpliance with long-term safety stan-

Nuclear Waste Policy Act requires tho following decisions, anyone which can stop the process:
(NRC) , the

dards is achievable.

In preparing to sub-

. The Secretary

must decide, based on a

formal evaluation of the site and after considering the views of States, affected Indian tribes, and the NRC, whether to recommend the site to the President. site recommendation must be accompa-

DOE is drawing on the Waste'Isolation Pilot Plant experience and focusing on both operational and long- term safety issues.

mit a license application ,

nied by an environmental impact statement which is scheduled for completion in 2000. Current schedules plan for a site
recommendation to be made in 2001.

_-n

1998
Viability Assessment

. The President will then decide, po$Sibly in 2001 , whether to recommend the Yucca Mountain site to Congress.
. If the

--- 2000
Environmental Impact Statement

, 2001
Governor and legislature of Nevada

Site Recommendation

submit a notice of disapproval to Con-

gress, Congress must then decide

whether to override Nevad~ s objections and approve the Yucca Mountain site,

2010
n -,

If the p receding ' decisions are made in
timely manner and ultimately support development of a repository at the Yucca
Mountain site, DOE would submit a license application to NRC in 2002,

2002
License Application

Emplacement begins

Stop if site

is unsuitable

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- ,Case 1:98-cv-00474-JFM Document 309-8 Filed 04/16/2004 Page 12 of 14
Application

---

Ucense

Operational safety
To ensure that a repository can be operated
sarely, DOE is using demonstrated teehnol-

, ers and the public during the preclosure pe-

riod of repository operations.

ogy and accepted design criteria , systematically identifying design-basis events , and
classifying aU repository structures, sys-

Identification of design-basis safety classifications and

events

tems, and components on the basis of their importance to safety.
Demonstrated technology

Nuclear Regulatory Commission regulations require DOE to

identify internal de-

and

sign-basis events (such as dropping awaste

accepted design criteria
Designing waste. handling facilities and op-

package) and external design.basis events
(such as an earthquake) that cOuld cause

erations is not a unique endeavor. Many codes, staJldards , and Nuclear Regulatory Commission regulatory guidance docu-

accidents resulting in unacceptable radialion exposures to workers or to the public.
The regulations require that DOE protect both workers and the public when design-

ments , along with many years of industry experience in the operation of nuclear fa.
. cilities, can be applied to

prec1osure reposi-

,

torydcsign and operations. (preclosure retime when waste is being fers to th!
emplaced and monitored. ) Man~' elements

ing any engineered structures, systems, or components that are important to safety: all such elements must be able to withstand design. basis events, The DOE is now identifying design- basis events , performing safety classifications, and incorporating the
resulting design requirements intO its design requirements dacumentation.

of the reference design are based on demonstrated technology and accepted design , criteria to ensure protection of both Work.

Artisrs concept of operations to move waste underground. Remote-controUed equipment would be used to place waste packages on rail cars and move the raft cars into shielded transporters. Human-operated eleclric locomotives would take loaded transporters underground,

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Page 13 of 14
License Application

Long-term safety
To reduce current uncertainties and in.
crease confidence that a repository can contain and isolate waste for

being injeeted into the rock, and scientists
are measuring how much and how quickly

thousands of

water moves through the rock. In another
experiment, microspheres are being injeeted
into the rock to simulat(, possible colloidal

years, DOE is focusing its ongoing efforts

on three major areas:
.' I ncreasing understanding of the key natural processes that are important to long. term performance of a l' epository
. Improving the

transport of radionuclides. These experiments will provide more data on how much

water might infiltrate the repository and
how water could transport

radio nuclides to

the water table.
design of key engineered components of a repository
Increasing confidence in performance as. sessment models

The DOE is also conducting experiments on the effect of heat generated by the waste

packages on moisture in the surrounding
rock. Large heaters have been placed in

areas of the existing tunnel , and scientists
These three sets of activities will be the fo. cus of DOE work between this viability assessment and the site recommendation decision, which could lead to submission of a

are observing the efrect of the heat on the unsaturated rock. These experiments will increase understanding of how water would

license application.
Increasing understanding of

be driven away from the waste packages
during the period of high temperature and how, later, declining temperatures could affect water movement through the unsaturated zone.

the key

natural processes that are important of a ' to long-term performance

repository
The key natural processes are water move.
ment through the unsaturated zone above

Additional information on the movement.

water in the saturated zone below the water table will be gained from a series of wells installed by DOE and from wells being in-

and below the repository, the effect of heat

stalled by Nye County, Nevada,

, from the waste packages on moisture in the rock around

, the tunn!ls and the movement of groundwater beneath

the repository. Increased un. derstanding of these processes will reduce the

uncertainties about the
performance of a repository.

The DOE is conducting experiments to determine how
water could move through the
unsaturated zone above and

below the repository tunnels. In one experiment, water con-

taining chemical tracers is
Completed single-e1ement heater test

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License Application

Evaluating

ways to

improve the design

of key

engineered components

of

repository
, As the design process progresses ,

DOE is

evaluating several design options and alterhatives that could reduce existing uncer-

tainty and improve the performance of the repository system. Some of these options and alternative concepts were suggested by
the Nuclear Waste Technical Review Board

and by stakeholders such as the Nuclear
Waste Repository Proje~t Office of Nye County, Nevada.
)'0

The repository design will incorporate de-

sign margin and defense in depth to increase confidence in repository perfor, mance, Design margin provides an extra of safety. For example , the waste margin
package thickness could be increased to pro-

vide extra design margin. Defense in depth is intended to ensure that failure in anyone
, 30
barrier would not lead to unacceptable performance of the entire repository system.

crence design. One alternative involves a much cooler , ventilated r(!pository design
so that moisture in the surrounding rock

J'he DCm will continue evaluating drip
shields, ceramic coatings , and backfill op-

would never reach the boiling point. This
alternative would reduce the complexity of

tions that could increase both design margin and dcfonse in depth.
The DOE is also considering alternative repository design concepts , some of which are significantly different from the current ref-

the interaction between the natural and
, engineered barriers,

Another alternative

is to use a shielded waste package that
would allow human entry into the emplacefor inspection and, if necessary, ment drifts remedial action. '

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