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

Case 1:98-cv-00154-JFM

Document 315-7

Filed 04/16/2004

Page 1 of 13

Background

million y(!ars and the long- term average

precipitation has been about 12 inches per year-comparable to that of present- day
Santa Fe, New Mexico. Even if this were to

groundwater in the region is trapped within a closed desert basin and does not flow into
any rivers that reach the ocean.

be the case in the future, most of the water would run off or evaporate rather than soak into the ground and possibly reach the repository.
A repository would be built about 1 000 feet
below the surface and 1

The concept of disposing of waste in the unsaturated zone in the desert regions of the

Southwest was first advanced by the U.
Geological Survey in the 1970s. In 1976
the director of the Geological

Survey sug-

gested that the region in and around the
Nevada nuclear weapons test site offered a variety of geologic formations and other attractive features , including remoteness and an arid climate. 15 In 1981 , a GeolQgical Sur-

000 feet above the

water table in what is called the unsaturated zone. The water table is about 2 000 feet beneath the crest of Yucca Mountain.

Any precipitation that does not run off or
evaporate at the surface would have to seep down nearly 1, 000 feet before reaching the

vey scientist noted that the desert South.
west has water tables that are among the
deepest in the world and that the region contains multiple natural barriers that

repository. Between the repository and the water table , it would have to move through
another 1

could isolate wastes for " tens of thousands

000 feet of the unsaturated zone

to perhaps hundreds of thousands of
years. "16

. beforE! reaching the water table. The

View of Yucca Mountain from \he south

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Case 1:98-cv-00154-JFM
Reference Design

Document 315-7

Filed 04/16/2004

Page 2 of 13

The design process
Designing a repository is an iterative process. The process begins with defining the
materials that are chosen to be

compatible

primary design objectives:

protecti

ng the

with the underground thermal and geochemical environment. , and the layout

. health and safety of both the workers and
the public during the period of repository

of tunnels takes into consideration the geology of the mountain.

operations; minimizing the amount of ra-

dioactive material that may eventually
reach the accessible environment; and keeping costs down to an acceptable level.
To achieve the design objectives, engineers

Through successive evaluations and im-

provements, the repository design has
evolved to the current reference design. The

reference design represents a snapshot of

work with scientists to design the manmade components ~f a repository to work effectively with the natural system. The

engineered barriers are intended to work
with the natural barriers-the
. climate of

geology and

the ongoing design process, thus providing a frame of reference to describe how a repository at Yucca Mountain could work. The repository design also offers insights about how to reduce uncertainty and modify the design to improve its performance. Im-

Yucca Mountain-to contain and . isolate waste for thousands of years. The
waste package design ,

provements are expected to continue as
more work is completed and more information about the site is obtained.

for example. includes

A conceptual model of the design process. Design ~ectives for reposilOly
components are identified, and then the de~igns are developed, evaluated,
and improved.

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Case 1:98-cv-00154-JFM

Document 315-7

Filed 04/16/2004

Page 3 of 13
Reference Design

The

reference design
. At the north

In the current reference design, spent

entrance to the underground

nuclear fuel and high- level radioactive waste would be transported to Yucta Mountain by truck or rail in specially designed shielded shipping containers licensed by the Nuclear Regulatory Commission; removed from the shipping containers and placed in
long- lived waste packages for disposal; car-

repository would be the faciliti es and
equipment to transfer waste from shipping containers to waste packages. Each

waste package would be welded closed

and thoroughly checked before being loaded- onto a shielded transporter to be
taken underground.
. At the south entrance

ried into the underground repository by rail cars; placed on supports in the tunnels; and

monitored until the repository is finally
closed and sealed.

would be the facilities to support the excavation and construction of the tunnels.

Surface facilities and operations
Surface facilities woul~ be designed to receive the waste and prepare it for final disposal, and to support the excavation, con-

. Near the

struction, loading, and ventilation of the repository tunnels. The entire surface layout would cover about 100 acres and have three main areas:

Workers would be shielded from direct exposure to radiation and contamination be~ cause waste would be handled remotely.

tory.

top of the mountain would be

the facilities that house the air intake and

exhaust fans for ventilating the reposi-

Artist's ooncept of repository surface facifilies

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Case 1:98-cv-00154-JFM

Document 315-7

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Reference Design

Underground facilities and operations
The underground repository would consist of about tOO miles of tunnels. The main . tunnels would be designed for moving workers , equipment, and waste packages. Ventilation tunnels would provide air for work-

would lift the waste package , carry it along the drift , and lower it onto its supports.

Current schedules anticipate that waste
emplacement would begin in 2010 if a license is received from the Nuclear Regulatory Commission , after construction of surface facilities , the main tunnels , ventilation system , and initial emplacement drifts. Additional drifts would be constructed over a period of about 20 years while waste is be-

ers. ')' hc emplacement tunnels (or drifts) would accommodate tho waste packages. Two gently sloping access ramps and two vertical ventilation sha,fts would connect the
undergl'Ound and surface areas.

Transportation underground would be by rail. A locomotive would haul the shielded transporter with its waste package underground from the waste- handling building . to the entrance of an emplacement drift. Then El remotely operated crane (or gantry)

ing emplaced. The current design would
accommodate 70, 000 metric tons of waste, a limit imposed by the Nuclear Waste Policy

Act of 1982. However , the site is large
enough to accommodate additional waste, if that were authorized.

Artist' s concept or repository underground facilities and operations

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Case 1:98-cv-00154-JFM

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Reference Design

The engineered barrier system
The engineered barrier syst..em is designed to work with the natural geologic barriers.
The reference repository design fea-

and includes the waste FueIA$semblyform. the' concrete tunnel ' floor (or invert), and the steel and concrete sup-

tures a long. lived

waste package

, port for the waste
pa~kage.
Inner
-, Barrier LId

Backfill would consist of
crushed rock or other granu-

The current waste
package design would have two layers: a structurally strong outer layer of carbon steel nearly four inches thick
and a cort'osion-resistant inner layer of a
high-nickel aHoy about three- fourths

lar material that would

placed around the waste packages in the emplacement drifts just before the repository is closed.
of an
The DOE also is evaluating alternative designs, some of which might reduce uncertainties regarding repository performance,
(Design alternatives are discussed further

inch thick. Thesc' two layers would work together to preserve the integrity of the

wast.c package.

under Long- Term

Safety, page 30.

Th(! wast(! forms inside the waste package would p.'ovide additional barriers against

transport of radionuclides away from the

repository, Most spent nuclear fuel is encased in Zircaloy, a metal cladding that is
highly resistant to corrosion, Defense highlevel radioactive waste would be solidified

Waste ~mplacement
Tunnel

as glass inside stainless steel canisters.
As the design process continues , DOE is evaluating several design options that

might increase the ability of the engineered
barrier system to contain waste. These include the following:
1Q

. Drip shields that could keep

water from

dripping on the waste packages
. C~ramie coating on the waste packages

that could further prevent corrosion
. Backfj)) that could protect the

waste

packages from falling rock or tunnel collapse, raise the waste packages' tempera-

. lure and lower the relative humidity

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Reference Design
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Confirmation and retrieval
Activities to confirm that a repository would

rounding rock. The effects of a repository
would be monitored ,

work as expected begin long before the first
. waste is emj)laced. In the current site char-

and the observed efactivities

fects would be compared to the model predictions. These confirmation

acterization phase, information about Yucca Mountain and the surrounding environment is being collected and compiled to pro-

would help determine whether a repository

is operating as expected.
If a problem is detected prior to closing the

vide a baseline against which to compare what would happen if a repository were . built and waste were emplaced.
Using mathematical models based on the

repository, remediai action or retrieval of
the waste would be possible using remotely
operated equipment. The Nuclear Regulatory COmmission currently requires that a
repository be designed to allow the retrieval

collected data and analyses of the engineered components, 'scientists forecast the probable behavior of the engineered system and the effects of a-repository on the Yucca Mountain environment. If repository operations begin, remote sensors would moni-

of waste at any time up to 50 years after waste operations begin. Retrieval of waste, if needed, would follow , in reverse order,

tor the waste packages , tunnels, and sur- '

waste.
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the same steps taken in emplacing the

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The performance confirmation program begins with site characterization to establish a basefine and continues until repository dosure begins,

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Case 1:98-cv-00154-JFM

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Reference Design

Repository

closing
and prevent water from entering through
these openings- .

Even under the most ambitious schedules
for disposal, future generations would make the fina,l decision to close a repository.

give future generations the option of clos-

ing the repository or monitoring it for long
periods of time, DOE is designing the repository so that it could (with Nuclear Regu-

At the surface, aU radiological areas would be decontaminated, aU 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-

latory Commission approval) be either
closed as early as 10 years after emplacement of the last waste package , or kept open for hundreds of years from the start of waste

nal condition. Permanent monumen
would be erected around the site to warn

emplacement,

nature of the buried wastes.
breach a repository s

any future generations of the presence and

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
engi-

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

neered or geologic barriers, or otherwise increase the exposure of the public to radiation beyond allowable limits.

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Case 1:98-cv-00154-JFM
Performance Assessment

Document 315-7

Filed 04/16/2004

Page 8 of 13

Performance assessment models
Performance assessment evaluates how a

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

system are most important to how well it is likely to work , and where scientists and engineers might most usefully focus their . efforts to improve performance. These assess-

ments are repeated and refined during the
course of developing, evaluating, arid im-

tures , events , and processes that could affeet the performance of the design. They
then incorporate the results of these de-

proving' a repository design.
A total system performancE! assessment rep-

tailed process models into an overall model
of the rE!pository system , which is called the

total system performance assessment
model. The models are used to assess how elements of a waste disposal system are likely to work together over the long period required to isolate wastes.
the natural and engineered

resents a reasonable approach to the challenging task of projecting how a repository would work over thousands of years. How-

ever, as a National Academy of Sciences
panel observed, " Confidence

in the disposal techniques must come from a combination of remoteness, engineering design, math-

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

ematical modeling, performance assessment, natural analogues and the possibil.

ity of remedial

this combined approach.

unforeseen events."11 The DOE is taking

action in the event of

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Approach to constructing a total system

perfo~ assessment (TSPA) model. Analysts

develop detailed mathematical models of the natural processes that are important to repository

performance and then combine these models Into a model of the entire repository system,

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Case 1:98-cv-00154-JFM

Document 315-7

Filed 04/16/2004

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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 al1, 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 auggcsted -that remote desert re
gions are well-suited for a geologic reposi-

Uliexpected test result was finding underground, at the level
tory. One important and

ages
. Long waste package
. Low rate

of the proposed repository, traces of a radioactive isotope (chlorine- 36) that is associated with , above- ground nuclear weapons tests. As atmospheric nuclear testing be, . gan in the mid - 1940s , this finding suggests

lifetime

of release ohadionuclides from breached waste packages
conc(mtration of radio-

that. some water travels from the ground
surface to the level of the repository in about 50 )' ears or less. Another important finding was evidence that the average amount

. Reduction in the

, nuclides as they are transported from
breached waste packages

of water that filters down through the
mountain is 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-

Bas~d on performance assessment models

DOE has evaluated the degree to which the reference design exhibits these four key at-

tributes , and has identified additional scientific studies and design improvements
that could reduce uncertainties and enhance

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

long- term

repository performance.

the natural barriers to keep water away
from the waste.

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Case 1:98-cv-00154-JFM
Performance Assessment

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LImited water contact with waste packages
In the reference design, waste packages

Once waste packages have been placed in
the repository, the heat gEmerated from radioactive decay would raise the temperature in the tunnels above the boiling point

would be placed about 1,000 feet. below the mountain s surface and abo\lt 1 000 feet

above the water table. Even if future climates are much wetter than today, the
mountain is not expected to erode and leave
the waste exposed, and the water table

of water. The heat is eXl)ected to dry out th~ surrounding rock and drive any water

away for hundreds to thousands of years.
However, as the waste decays and the

not expected to rise high enough to reach
the waste,

re-

pository cools, enough water to cause drips

would begin to seep into the drifts through
In the current semiarid climate, about seven inches of wuter 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 ofwatcl' per year moves down (or percolates) through the nearly 1, 000 feet of rock to of the repository. Studies of reach the level past climates indicate that 'the precipitation . may increase to a long. term average 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 rock.

Using mathematical models ,

analysts estimate 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 would mitigate the effects of
water contact and improve performance of
a repository.

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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

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. Projections of waste package performance also assume that at least one waste package will fail in 1 000 years due to a manufacturing defect.

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 preliminary results of corrosion

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 than 000 years , even if water is dripping on them. Tho longevity of man-made ma~rials in the repository environment over such
long periods of time is subject to significant

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

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

package de-

uncertainty, howev~r, and some waste packages could fail earlier. Scientists estimate

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

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Performance Assessment

Low rate of release of radionuclides from breached waste packages
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 of the commercial spent

During the thousands of years required for water to reach -the waste, the radioactivity
of most of the radionuclides would decay to

nudesT fuel, the cladding is highly corrosion-resistant metal that is designed to

withstand the extreme temperatqre and radiation environment in the core of an operating nuclear reactor. Current models in. dicate that it would take thousands of years

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, nep-

to corrode dadding sufficiently to allow
water to reach the waste and begin to dis-

tunium, and uranium , could get out of the
waste package. Although most of the waste

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

would not migrate from the package even , if it were breached , the release of any raw
dionuclides is reason for concern and motivation for seeking improvements in the re-

pository design. Ongoing tests are

providing more information on how radionuclides dissolve in water.

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Performance Assessment

Reduction in the concentration

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

the waste packages
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 a well and consumed or used to irrigate crops.
As the long- lived , water-soluble radio""lelides begin to move down through the rock

to small particles (or colloids) and then be transported along with those particles.

Given the uncertainty about the rate at which groundwater moves and the posSible

existence of fast pathways or channels

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

through the saturated zone, the DOE is con-

tinuing to investigate groundwater flow

volume o(groundwater be.

characteristics and is analyzing the possible effects on radionuc1ide transport and dilution. .

neath Yucca Mountain , and the concentrations ""HI be diluted. Eventually, ground-

water with varying concentrations
differ(mt radionuclides will reach locations near Yucca Mountain where the water could
be consumed.

Of the approximately 350 different radioactive 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, nep237, and uranium- 234-can be tunium-

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