32074 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

ENVIRONMENTAL PROTECTION

AGENCY

40 CFR Part 197

[FRL–6995–7]

RIN 2060–AG14

Public Health and Environmental

Radiation Protection Standards for

Yucca Mountain, NV

AGENCY: Environmental Protection

Agency (EPA).

ACTION: Final rule.

SUMMARY: We, the Environmental

Protection Agency (EPA), are

promulgating public health and safety

standards for radioactive material stored

or disposed of in the potential

repository at Yucca Mountain, Nevada.

Section 801 of the Energy Policy Act of

1992 (EnPA, Pub. L. 102–486) directs us

to develop these standards. Section 801

of the EnPA also requires us to contract

with the National Academy of Sciences

(NAS) to conduct a study to provide

findings and recommendations on

reasonable standards for protection of

the public health and safety. The health

and safety standards promulgated by

EPA are to be ‘‘based upon and

consistent with’’ the findings and

recommendations of NAS. On August 1,

1995, NAS released its report (the NAS

Report), titled ‘‘Technical Bases for

Yucca Mountain Standards.’’ We have

taken the NAS Report into consideration

as the EnPA directs.

The Nuclear Regulatory Commission

(NRC) will incorporate these final

standards into its licensing regulations.

The Department of Energy (DOE) must

demonstrate compliance with these

standards. The NRC will use its

licensing regulations to determine

whether DOE has demonstrated

compliance with our standards prior to

receiving the necessary licenses to store

or dispose of radioactive material in

Yucca Mountain.

DATES: Effective Date: This rule becomes

effective July 13, 2001.

ADDRESSES: Documents relevant to the

rulemaking. You can find and access

materials relevant to this rulemaking in:

(1) Docket No. A–95–12, located in

Waterside Mall Room M–1500 (first

floor, near the Washington Information

Center), 401 M Street, SW., Washington,

DC 20460; (2) an information file in the

Government Publications Section, Lied

Library, University of Nevada-Las

Vegas, 4505 Maryland Parkway, Las

Vegas, Nevada 89154; and (3) an

information file in the Public Library in

Amargosa Valley, Nevada 89020.

Background documents for this

action. We have prepared additional

documents that provide more detailed

technical background in support of

these standards. You may obtain copies

of the Background Information

Document (BID), the Economic Impact

Analysis (EIA), the Response to

Comments document, and the Executive

Summary of the NAS Report, by writing

to the Office of Radiation and Indoor Air

(6608J), U.S. Environmental Protection

Agency, Washington, DC 20460-0001.

We placed these documents into the

docket and information files. You also

may find them on our Internet site for

Yucca Mountain (see the Additional

Docket and Electronic Information

section later in this document).

FOR FURTHER INFORMATION CONTACT: Ray

Clark, Office of Radiation and Indoor

Air, U.S. Environmental Protection

Agency, Washington, DC. 20460–0001;

telephone 202–564–9310.

SUPPLEMENTARY INFORMATION:

Whom Will These Standards Regulate?

The DOE is the only entity directly

regulated by these standards. Before it

may accept waste at the Yucca

Mountain site, DOE must obtain a

license from NRC. Thus, DOE will be

subject to our standards, which NRC

will implement through its licensing

proceedings. Our standards affect NRC

only because, under the Energy Policy

Act of 1992 (EnPA, Pub. L. 102–486, 42

U.S.C. 10141 n. (1994)), NRC must

modify its licensing requirements, as

necessary, to make them consistent with

our final standards.

Additional Docket and Electronic

Information

When may I examine information in

the docket? You may inspect the

Washington, DC, docket (phone 202–

260–7548) on weekdays (8 a.m.-5:30

p.m.). The docket personnel may charge

you a reasonable fee for photocopying

docket materials (40 CFR part 2).

You may inspect the information file

located in the Lied Library at the

University of Nevada-Las Vegas,

Research and Information Desk,

Government Publications Section (702–

895-2200) when classes are in session.

Hours vary based upon the academic

calendar, so we suggest that you call

ahead to be certain that the library will

be open at the time you wish to visit (for

a recorded message, call 702–895–2255).

You may inspect the information file

in the Public Library in Amargosa

Valley, Nevada (phone 775–372–5340).

As of this date, the hours are Tuesday

through Thursday (10 a.m.–7 p.m.);

Friday (10 a.m.–5 p.m.); and Saturday

(10 a.m.–2 p.m.). The library is closed

daily from 12:30 p.m.–1 p.m. It also is

closed Sundays and Mondays.

Can I access information by telephone

or via the Internet? Yes. You may call

our toll-free information line (800–331–

9477) 24 hours per day. By calling this

number, you may listen to a brief update

describing our rulemaking activities for

Yucca Mountain, leave a message

requesting that we add your name and

address to the Yucca Mountain mailing

list, or request that an EPA staff person

return your call. You also can find

information and documents relevant to

this rulemaking on the World Wide Web

at http://www.epa.gov/radiation/yucca.

We also recommend that you examine

the preamble and regulatory language

for the proposed rule, which appeared

in the Federal Register on August 27,

1999 (64 FR 46976).

What documents are referenced in

today’s action? We refer to a number of

documents that provide supporting

information for our Yucca Mountain

standards. All documents relied upon

by EPA in regulatory decisionmaking

may be found in our docket (Docket No.

A–95–12). Other documents, e.g.,

statutes, regulations, proposed rules, are

readily available from other public

sources. The documents below are

referenced most frequently in today’s

action.

Item No.

II–A–1 Technical Bases for Yucca

Mountain Standards (The NAS

Report), National Research Council,

National Academy Press, 1995

V–A–4 Draft Environmental Impact

Statement for Yucca Mountain, DOE/

EIS–0250D, July 1999

V–A–5 Viability Assessment for Yucca

Mountain, DOE/RW–0508, December

1998

V–B–1 Final Background Information

Document (BID) for 40 CFR 197, EPA–

402–R–01–004

V–C–1 Final Response to Comments

Document for 40 CFR 197, EPA–402–

R–01–009

V–A–17 Nevada Risk Assessment/

Management Program (NRAMP)

Acronyms and Abbreviations

We use many acronyms and

abbreviations in this document. These

include:

ALARA-as low as reasonably achievable

APA-Administrative Procedure Act

BID-background information document

CAA-Clean Air Act

CEDE-committed effective dose

equivalent

CG-critical group

DEIS-Draft Environmental Impact

Statement

DOE–U.S. Department of Energy

DOE/VA–DOE’s Viability Assessment

EIS-Environmental Impact Statement

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32075

1These laws include the Atomic Energy Act of

1954, as amended (42 U.S.C. 2011–2296);

Reorganization Plan No. 3 of 1970 (5 U.S.C.

Appendix 1).

EnPA-Energy Policy Act of 1992

EPA–U.S. Environmental Protection

Agency

GCD-greater confinement disposal

HLW-high-level radioactive waste

IAEA-International Atomic Energy

Agency

ICRP-International Commission on

Radiological Protection

LLW-low-level radioactive waste

MCL-maximum contaminant level

MCLG-maximum contaminant level goal

MTHM-metric tons of heavy metal

NAS-National Academy of Sciences

NCRP-National Council on Radiation

Protection and Measurements

NEPA-National Environmental Policy

Act

NESHAPs-National Emission Standards

for Hazardous Air Pollutants

NID-negligible incremental dose

NIR-negligible incremental risk

NRC–U.S. Nuclear Regulatory

Commission

NRDC-Natural Resources Defense

Council

NTS-Nevada Test Site

NTTAA-National Technology Transfer

and Advancement Act

NWPA-Nuclear Waste Policy Act of

1982

NWPAA-Nuclear Waste Policy

Amendments Act of 1987

OMB-Office of Management and Budget

RCRA-Resource Conservation and

Recovery Act

RME-reasonable maximum exposure

RMEI-reasonably maximally exposed

individual

SAB-Science Advisory Board

SDWA-Safe Drinking Water Act

SNF-spent nuclear fuel

TDS-total dissolved solids

TRU-transuranic

UIC-underground injection control

UMRA-Unfunded Mandates Reform Act

of 1995

UNSCEAR-United Nations Scientific

Committee on the Effects of Atomic

Radiation

USDW-underground source of drinking

water

WIPP LWA-Waste Isolation Pilot Plant

Land Withdrawal Act of 1992

Outline of Today’s Action

I. What is the History of Today’s Action?

A. What is the Relationship of 40 CFR part

191 to the Yucca Mountain Standards?

1. Evolution of 40 CFR part 191

2. The Role of 40 CFR part 191 in the

Development of 40 CFR part 197

II. Background Information

A. In Making Our Final Decisions, How

Did We Incorporate Public Comments on

the Proposed Rule?

1. Introduction and the Role of Comments

in the Rulemaking Process

2. How Did We Respond to General

Comments on Our Proposed Rule?

B. What Are the Sources of Radioactive

Waste?

C. What Types of Health Effects Can

Radiation Cause?

D. What Are the Major Features of the

Geology of Yucca Mountain and the

Disposal System?

E. Background on and Summary of the

NAS Report

1. What Were NAS’s Findings

(‘‘Conclusions’’) and Recommendations?

III. What Does Our Final Rule Do?

A. What Is the Standard for Storage of the

Waste? (Subpart A, §§ 197.1 through

197.5)

B. What Are the Standards for Disposal?

(§§ 197.11 through 197.36)

1. What Is the Standard for Protection of

Individuals? (§§ 197.20 and 197.25)

a. Is the Limit on Dose or Risk?

b. What Factors Can Lead to Radiation

Exposure?

c. What Is the Level of Protection for

Individuals?

d. Who Represents the Exposed

Population?

e. How Do Our Standards Protect the

General Population?

f. What Do Our Standards Assume About

the Future Biosphere?

g. How Far Into the Future Is It Reasonable

To Project Disposal System Performance?

2. What Are the Requirements for

Performance Assessments and

Determinations of Compliance?

(§§ 197.20, 197.25, and 197.30)

a. What Limits Are There on Factors

Included in the Performance

Assessments?

b. What Limits Are There on DOE’s

Elicitation of Expert Opinion?

c. What Level of Expectation Will Meet

Our Standards?

d. Are There Qualitative Requirements to

Help Assure Protection?

3. What Is the Standard for Human

Intrusion? (§ 197.25)

4. How Does Our Rule Protect Ground

Water? (§ 197.30)

a. Is the Storage or Disposal of Radioactive

Material in the Yucca Mountain

Repository Underground Injection?

b. Does the Class-IV Well Ban Apply?

c. What Ground Water Does Our Rule

Protect?

d. How Far Into the Future Must DOE

Project Compliance With the Ground

Water Standards?

e. How Will DOE Identify Where to Assess

Compliance With the Ground Water

Standards?

f. Where Will Compliance With the Ground

Water Standards be Assessed?

IV. Responses to Specific Questions for

Public Comment

V. Severability

VI. Regulatory Analyses

A. Executive Order 12866

B. Executive Order 12898

C. Executive Order 13045

D. Executive Order 13084

E. Executive Order 13132

F. National Technology Transfer and

Advancement Act

G. Paperwork Reduction Act

H. Regulatory Flexibility Act as amended

by the Small Business Regulatory

Enforcement Fairness Act of 1996

(SBREFA) 5 U.S.C. 601 et seq.

I. Unfunded Mandates Reform Act

J. Executive Order 13211

I. What Is the History of Today’s

Action?

Spent nuclear fuel (SNF) and highlevel radioactive waste (HLW) have

been produced since the 1940s, mainly

as a result of commercial power

production and defense activities. Since

then, the proper disposal of these wastes

has been the responsibility of the

Federal government. The Nuclear Waste

Policy Act of 1982 (NWPA, Pub. L. 97–

425) formalizes the current Federal

program for the disposal of SNF and

HLW by:

(1) Making DOE responsible for siting,

building, and operating an underground

geologic repository for the disposal of

SNF and HLW;

(2) Directing us to set generally

applicable environmental radiation

protection standards based on authority

established under other laws; 1 and

(3) Requiring NRC to implement our

standards by incorporating them into its

licensing requirements for SNF and

HLW repositories.

This general division of

responsibilities continues for the Yucca

Mountain disposal system. Thus, today

we are establishing public health

protection standards (specific to the

Yucca Mountain site, rather than

generally applicable). The NRC will

issue implementing regulations for this

rule. The DOE will submit a license

application to NRC. The NRC then will

determine whether DOE has met the

standards and whether to issue a license

for Yucca Mountain. The NRC will

require DOE to comply with all of the

applicable provisions of 40 CFR part

197 before authorizing DOE to receive

radioactive material at the Yucca

Mountain site.

In 1985, we established generic

standards for the management, storage,

and disposal of SNF, HLW, and

transuranic (TRU) radioactive waste (see

40 CFR part 191, 50 FR 38066,

September 19, 1985), which apply to

any facilities for the storage or disposal

of these wastes, including Yucca

Mountain. In 1987, the U.S. Court of

Appeals for the First Circuit remanded

the disposal standards in 40 CFR part

191 (NRDC v. EPA, 824 F.2d 1258 (1st

Cir. 1987)). As discussed below, we later

amended and reissued these standards

to address issues that the court raised.

32076 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

Also in 1987, the Nuclear Waste

Policy Amendments Act (NWPAA, Pub.

L. 100–203) amended the NWPA by,

among other actions, selecting Yucca

Mountain, Nevada, as the only potential

site that DOE should characterize for a

long-term geologic repository.

In October 1992, the Waste Isolation

Pilot Plant Land Withdrawal Act (WIPP

LWA, Pub. L. 102–579) and the EnPA

became law. These statutes changed our

obligations concerning radiation

standards for the Yucca Mountain

candidate repository. The WIPP LWA:

(1) Reinstated the 40 CFR part 191

disposal standards, except those

portions that were the specific subject of

the remand by the First Circuit;

(2) required us to issue standards to

replace the portion of the challenged

standards remanded by the court; and

(3) exempted the Yucca Mountain site

from the 40 CFR part 191 disposal

standards.

We issued the amended 40 CFR part

191 disposal standards, which

addressed the judicial remand, on

December 20, 1993 (58 FR 66398).

The EnPA, enacted in 1992, set forth

our responsibilities as they relate to the

Yucca Mountain repository. In the

EnPA, Congress directed us to set public

health and safety radiation standards for

Yucca Mountain. Specifically, section

801(a)(1) of the EnPA directs us to

‘‘promulgate, by rule, public health and

safety standards for the protection of the

public from releases from radioactive

materials stored or disposed of in the

repository at the Yucca Mountain site.’’

The EnPA also directed us to contract

with NAS to conduct a study to provide

us with its findings and

recommendations on reasonable

standards for protection of public health

and safety. Moreover, it provided that

our standards shall be the only such

standards applicable to the Yucca

Mountain site and are to be based upon

and consistent with NAS’s findings and

recommendations. On August 1, 1995,

NAS released its report, ‘‘Technical

Bases for Yucca Mountain Standards’’

(the NAS Report) (Docket No. A–95–12,

Item II–A–1).

A. What Is the Relationship of 40 CFR

Part 191 to the Yucca Mountain

Standards?

Throughout today’s action, we refer to

the provisions of 40 CFR part 191 to

support the decisions we made

regarding the components of the final

Yucca Mountain rule. Pursuant to

section 8(b)(2) of the WIPP LWA, 40

CFR part 191 is not applicable to the

characterization, licensing,

construction, operation, or closure of

the Yucca Mountain repository. We

believe, however, that while 40 CFR

part 191 is not directly applicable to

Yucca Mountain, because it contains the

fundamental components for the

protection of public health and the

environment that apply to any SNF,

HLW, or TRU radioactive waste

repository, certain of its basic concepts

must be applied to Yucca Mountain as

appropriate. Further, because 40 CFR

part 191 provides fundamental support

for today’s rule, we believe it is useful

to explain here the process by which 40

CFR part 191 evolved.

1. Evolution of 40 CFR Part 191

We used the rulemaking for 40 CFR

part 191 to define the fundamental

components of any environmental

standard applicable to the disposal of

SNF, HLW, and TRU radioactive waste.

In our proposal (47 FR 58196, December

29, 1982), we recognized two basic

considerations regarding the disposal of

SNF, HLW, and TRU radioactive waste:

• The intent of disposal is to isolate

the wastes from the environment for a

very long time, longer than any time

over which active institutional controls

might be effective; and

• The disposal systems will be

designed to allow only very small

releases to the environment, if not

disturbed. A principal concern is the

possibility of accidental releases due to

unintended events or failure of

engineered barriers.

These considerations mean that any

standard that we establish and that NRC

and DOE implement: (1) Can only be

implemented during development and

operation of the repository, (2) must

address unintentional releases, and (3)

must accommodate significant

uncertainties. (See 47 FR 58198,

December 29, 1982)

From these considerations, we

proposed standards consisting of

Containment Requirements, which limit

the total amount of radionuclides that

may enter the environment over 10,000

years; Assurance Requirements, which

provide several principles enhancing

confidence that the containment

requirements will be met; and

Procedural Requirements, which assure

the proper application of the

containment requirements. We also

invited public comment on alternative

approaches for the standards,

specifically on the alternative of

establishing exposure limits for

individuals. Although the containment

requirements, as proposed, were

designed to protect people and the

environment for a long time, we did not

propose an individual exposure limit.

We believed the compliance point for

such a limit would have to be some

distance from the repository. Otherwise,

it would have to ignore the risks from

unplanned events such as human

intrusion. It seemed likely that

individuals located extremely near the

repository or who intrude into the

repository would receive doses far

exceeding any existing or reasonably

acceptable radiation limits.

EPA received substantial public

comment on the 40 CFR part 191

proposal. As a direct result of

information provided in many of the

comments, we issued a final rule (50 FR

38066, September 19, 1985) that differed

in many respects from the proposal. In

addition to containment and assurance

requirements, the final rule included

two new components:

• Individual Protection

Requirements, which protect members

of the public for 1,000 years of

undisturbed performance; and

• Ground Water Protection

Requirements, which protect ‘‘special

sources of ground water’’ for 1,000 years

of undisturbed performance.

The risk objectives for the

containment requirements in the final

rule maintained the same limiting level

of health impacts as the proposal (1000

fatal cancers over 10,000 years for a

repository containing 100,000 metric

tons of heavy metal (MTHM)); however,

we did modify the radionuclide-specific

release limits to reflect updated

performance analyses and updated

information on the health effects of

ionizing radiation. However, members

of the public and our Science Advisory

Board (SAB) expressed some concerns

regarding residual risks and the ability

of the licensee of any repository to

demonstrate compliance with the

standards given the uncertainties about

these facilities that arise over the long

time periods at issue (see the ‘‘Report on

the Review of Proposed Environmental

Standards for the Management and

Disposal of Spent Nuclear Fuel, HighLevel and Transuranic Radioactive

Wastes,’’ January 1984, Docket No. A–

95–12, Item V–A–21). To address these

concerns, we incorporated the concept

that the standards be met with

‘‘reasonable expectation’’ (§ 191.13(b)).

Improved performance assessments

indicated that the containment

requirements could, in fact, be achieved

by a variety of repository site/design

combinations without significant effects

on disposal costs. The final rule also

defined for the first time a ‘‘controlled

area,’’ or tract of land inside of which

compliance is not evaluated. The

concept of a controlled area was carried

from the proposal, where it was

included in the definition of ‘‘accessible

environment’’. In addition, we added

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32077

‘‘Guidance for Implementation,’’ which

replaced the previous procedural

requirements section. It addresses some

of the uncertainties with demonstrating

compliance, such as the limitations of

passive and active institutional controls

and the degree of certainty required to

demonstrate compliance with the

individual and ground water protection

requirements.

On the basis of public comments and

our analyses of disposal systems, we

incorporated individual protection

requirements, applicable to all pathways

of exposure effective for 1,000 years

after disposal. In addition, our analyses

of disposal systems supported setting

ground water protection requirements to

protect ‘‘special sources of ground

water’’ to limits very similar to the

Maximum Contaminant Levels (MCLs)

at 40 CFR part 141. Public comment was

very influential towards our

incorporation of individual-protection

requirements and ground-water

protection requirements. To address the

concerns expressed in the proposed rule

related to protection of individuals who

are extremely near the repository or who

may intrude into the repository, the

individual-protection requirements

apply to any member of the public in

the accessible environment for the case

of undisturbed performance.

Legal challenges required us to

reconsider the individual and ground

water protection requirements in a

subsequent rulemaking to amend 40

CFR part 191 (see 58 FR 66398,

December 20, 1993). In 1987, the U.S.

Court of Appeals for the First Circuit

remanded subpart B of the 1985

standards to EPA for further

consideration (Natural Resources

Defense Council, Inc. v. United States

Environmental Protection Agency, 824

F.2d 1258 (1st Cir. 1987)). The court

questioned the appropriateness of the

1,000 year time frame for the individual

protection requirement, the interrelationship of the individual-protection

requirement with the Safe Drinking

Water Act (SDWA), and whether the

Agency provided proper notice for the

ground water protection requirements.

For a more detailed discussion of the

court’s decision, see the preamble to the

final amendments to 40 CFR part 191

(58 FR 66399–66411, December 20,

1993). The Waste Isolation Pilot Plant

Land Withdrawal Act of 1992 reinstated

the 1985 version of 40 CFR part 191

except for those portions of the rule that

were the subject of the remand. In the

final amendments to 40 CFR part 191,

which replaced the remanded portions

of 40 CFR part 191, we set the

individual-protection requirement at 15

mrem/yr, calculated as an annual

committed effective dose, for all

pathways of exposure of any member of

the public in the accessible

environment, effective for 10,000 years

after disposal. The ground water

protection provisions limit the

concentrations of radioactivity in any

underground source of drinking water

(USDW) in the accessible environment

to the MCLs of the SDWA (40 CFR part

141).

2. The Role of 40 CFR Part 191 in the

Development of 40 CFR Part 197

The EnPA directs us to develop sitespecific public health protection

standards for the Yucca Mountain site.

To perform this task properly, we must

answer two fundamental questions

relative to the content of the standards.

These two questions are:

(1) What are the relevant components

of such standards?

(2) How can they be applied in more

detail in a reasonable but conservative

manner to the Yucca Mountain site?

There are two primary sources of

information, insight, and guidance on

repository performance standards in

general and the standards applicable to

the Yucca Mountain site in particular.

These sources are the generic standards

for land disposal of SNF, HLW, and

TRU radioactive waste (40 CFR part

191) and the NAS report mentioned

above. We relied heavily on these

sources in developing the Yucca

Mountain standards.

As described in the previous section,

we developed 40 CFR part 191 as

generic standards that apply to the land

disposal of SNF, HLW, and TRU

radioactive wastes. The components of

generic standards like 40 CFR part 191,

such as the individual-protection

requirement, would all apply to some

degree to any candidate site, but may

not be equally important at any

particular site. The WIPP LWA exempts

the Yucca Mountain site from being

licensed under the generic standards;

however, the basic components of the

generic standards clearly are valid

components for consideration in

developing standards that apply to a

specific site. For example, in the EnPA,

Congress specifically instructs us to

‘‘prescribe the maximum annual

effective dose equivalent to individual

members of the public’’ (EnPA section

801(a)(1)); such an individual dose

standard is an integral part of 40 CFR

part 191.

We believe that 40 CFR part 191 is a

logical starting point for developing the

site-specific Yucca Mountain standards

because it contains the fundamental

components necessary to evaluate

whether a potential geologic repository

site will perform satisfactorily relative

to the protection of public health and

the environment. Where appropriate in

the site-specific context of the Yucca

Mountain standards, we rely on the

precedent of, and the reasoning in, 40

CFR part 191 throughout this preamble

as support for including specific

components in the Yucca Mountain

standards. This statement does not

mean that we have applied the 40 CFR

part 191 standards to Yucca Mountain.

Rather, we evaluated the 40 CFR part

191 standards de novo to determine

whether it may be appropriate for us to

apply any of them in the Yucca

Mountain context. The NAS Report is

relevant because it contains

recommendations on scientific issues

involved with geologic disposal in

general, as well as specific

recommendations based upon

examination of the Yucca Mountain site.

We refer to these two sources in the

discussions that follow to explain why

we structured the standards in a

particular way and how we considered

the public comments we received in

response to the proposed standards.

We evaluated each generic component

of 40 CFR part 191 on an individual

basis to determine whether it is

appropriate to apply it to the Yucca

Mountain site as a component of a

standard protective of public health. If

we found it was appropriate to apply

one of 40 CFR part 191’s generic

components to Yucca Mountain, we

included that component in the Yucca

Mountain standards. Next, we

considered how to incorporate each

appropriate component in a reasonable,

but conservative, manner to the sitespecific conditions at the Yucca

Mountain site. The NAS Report was a

primary source of guidance and insight

in answering that question,

supplemented by the available data on

the characteristics of the site including

information on the distribution,

lifestyles, and other demographic

characteristics of the population in the

vicinity of the site. The BID

accompanying the 40 CFR part 197

standards contains much of this

information. Other sources of

information, such as DOE’s Yucca

Mountain DEIS, are noted in the

following discussions as appropriate.

Before selecting and formulating

specific elements of the standards, we

must consider that radiological hazards

to public health from a deep geologic

repository come from the release of

radionuclides and the subsequent

exposure of the population to these

radionuclides. This exposure occurs as

a result of two different processes: the

expected degradation over time (caused

32078 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

2NRC agreed to include assurance requirements

in its regulations for geologic repositories (10 CFR

part 60, ‘‘Disposal of High-Level Radioactive Wastes

in Geologic Repositories’’, 46 FR 13980, February

25, 1981).

3EnPA, Public Law No. 102–486, 106 Stat. 2776,

42 U.S.C. 10141 n. (1994).

by natural processes and events) of the

natural and engineered barriers in the

repository; and the breaching of these

barriers by human activities. It is

necessary to include both of these

release modes in a health-based

standard if it is to be protective. It also

is necessary to develop standards

against which it is possible, using

reasonable means, to judge repository

performance to determine compliance.

Based upon basic principles of health

physics, we believe that, any releases

and consequent exposures to the public

from the radionuclides emplaced into

the repository could affect public

health. Therefore, it is appropriate for us

to evaluate the effects of these releases

to determine whether we should

address them in our standards. The NAS

Report (Chapters 2 & 3) describes the

potential pathways through which

exposures to the public can occur from

geologic disposal. Part 191 contains

three provisions related to these

potential release pathways that we

believe are appropriate for application

at Yucca Mountain. More specifically,

40 CFR part 191 contains an individualprotection standard (which limits

exposure from all pathways by which an

individual can be exposed), groundwater protection standards (aimed at the

protection of ground water resources for

use by individuals who may be exposed

from using those resources), and a

human-intrusion component of the

containment requirements (aimed at

protection from the inadvertent

breaching of the repository containment

barriers and subsequent exposures to

the population). We believe these three

basic components of the generic 40 CFR

part 191 standards apply to the Yucca

Mountain site because they represent

avenues of exposure and mechanisms of

release that are reasonably foreseeable

given the conditions at Yucca Mountain.

We did not see the need to include in

40 CFR part 197 the containment

requirements in 40 CFR part 191 for

several reasons. First, we decided that,

unlike the generic analyses supporting

the development of release limits in 40

CFR part 191, the potential for largescale dilution of radionuclides (and

consequent wider exposure to large

populations), through ground water and

into surface water, as modeled in the

supporting analyses for 40 CFR part 191,

does not exist at Yucca Mountain. As

discussed in Chapters 7 and 8 and

Appendix IV of the BID and the

preamble to proposed 40 CFR part 197

(64 FR 46991, August 27, 1999), the

Yucca Mountain repository will be

located in an unsaturated rock

formation with limited amounts of

infiltrating water passing through it and

into the underlying tuff aquifer. Any

releases into the ground water will be

heavily constrained by the geologic

features of the surrounding rocks to

move in relatively confined pathways,

rather than widely dispersed into the

surrounding area around the repository.

The aquifer is within a ground water

system that discharges into arid areas

having high evaporation rates and very

little surface water, further limiting the

potential for widespread population

exposures.

As discussed in the preamble to the

proposed 40 CFR part 191 (58 FR

46991), we developed the containment

requirements in 40 CFR part 191 during

the siting process mandated by the

NWPA in the 1980s. In that context,

population doses are an important

consideration. The release limits in 40

CFR part 191 were found to be

reasonably achievable for several types

of geologic settings (including tuff) and

would keep the risks to future

populations acceptably small. Because

the potential for significant exposures

from the Yucca Mountain repository is

primarily through a strongly directional

ground water pathway (BID, Chapters 7

and 8), a ‘‘cautious, but reasonable’’

individual-protection standard will offer

the same protection as the containment

requirement included in 40 CFR part

191.

Although we included important

components of 40 CFR part 191 in our

Yucca Mountain standards, we did not

simply replicate the provisions of 40

CFR part 191. For example, as discussed

above, we do not include containment

requirements because we believe that

the individual-protection requirements

adequately will protect the general

population given the specific conditions

at Yucca Mountain. Similarly, we do not

include assurance requirements because

we expect NRC to incorporate

equivalent requirements into its

implementing regulations. Because the

assurance requirements in 40 CFR part

191 do not apply to NRC-licensed

facilities 2, NRC will need to include

assurance requirements in its

implementing regulations for the Yucca

Mountain repository. Measures that are

effectively equivalent to the 40 CFR part

191 assurance requirements have been

included in NRC’s proposed 10 CFR

part 63. The site-specific nature of the

Yucca Mountain standards requires us

to evaluate the unique characteristics of

the Yucca Mountain site to develop the

more detailed aspects of our standards,

such as appropriate compliance points.

The relative importance of the three

regulatory components of 40 CFR part

191 in determining compliance in the

regulatory review process is a direct

reflection of site-specific conditions. For

example, for WIPP, evaluating releases

from human intrusion (by drilling to

explore for or exploit the oil, gas and

mineral resources present at the site)

was the primary test for compliance

against the standards because under

expected undisturbed conditions no

releases from the repository are

anticipated. Compliance with the

individual-protection standard was

consequently based upon a scenario

related to the migration of radionuclides

from the repository to a near surface

aquifer via an abandoned deep borehole.

Consequently, we defined details for

assessing an intrusion scenario at the

WIPP site on the basis of current and

historical practices regarding exploring

for and recovering natural resources in

the area. In contrast, the Yucca

Mountain site is relatively poor in

known attractive natural resources,

other than ground water (see Chapter 8

of the BID). Therefore, consistent with

NAS’s recommendations, we adopted a

stylized human-intrusion scenario for

analysis. The NAS’s recommendations

and the data base of information

available about the site allowed us to

develop the specific details of the

human-intrusion scenario, which we

proposed in the draft rule. Comments

we received during the public comment

process also played an important role in

framing the contents of the scenario. See

the Response to Comments document

for a more detailed discussion of these

issues.

II. Background Information

A. In Making Our Final Decision, How

Did We Incorporate Public Comments

on the Proposed Rule?

1. Introduction and the Role of

Comments in the Rulemaking Process

Section 801(a)(1) of the EnPA requires

us to set public health and safety

radiation protection standards for Yucca

Mountain by rulemaking.3 Pursuant to

Section 4 of the Administrative

Procedure Act (APA), regulatory

agencies engaging in informal

rulemaking must provide notice of a

proposed rulemaking, an opportunity

for the public to comment on the

proposed rule, and a general statement

of the basis and purpose of the final

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32079

4 5 U.S.C. 553.

rule.4 The notice of proposed

rulemaking required by the APA must

‘‘disclose in detail the thinking that has

animated the form of the proposed rule

and the data upon which the rule is

based.’’ (Portland Cement Association v.

Ruckelshaus, 486 F. 2d 375, 392–94

(D.C. Cir. 1973)) The public thus is

enabled to participate in the process by

making informed comments on the

proposal. This provides us with the

benefit of ‘‘an exchange of views,

information, and criticism between

interested persons and the agency.’’ (Id.)

There are two primary mechanisms by

which we explain the issues raised in

public comments and our reactions to

them. First, we discuss broad or major

comments in the succeeding sections of

this preamble. Second, we are

publishing a document, accompanying

today’s action, entitled ‘‘Response to

Comments’’ (Docket No. A–95–12, Item

V–C–1). The Response to Comments

document provides more detailed

responses to issues addressed in the

preamble. It also addresses all other

significant comments on the proposal.

We gave all the comments we received,

whether written or oral, consideration

in developing the final rule.

2. How Did We Respond to General

Comments on Our Proposed Rule?

We received many comments that

addressed broad issues related to the

proposed standards. Several

commenters simply expressed their

support for, or opposition to, the Yucca

Mountain repository. The purpose of

our standards is to ensure that any

potential releases from the repository do

not result in unacceptably high

radiation exposures. Our standards

make no judgment regarding the

suitability of the Yucca Mountain site or

whether NRC should issue a license for

the site. Such a decision is beyond the

scope of our statutory authority.

Some comments suggested our

standards should consider radiation

exposures from all sources because of

the site’s proximity to the Nevada Test

Site (NTS) and other sources of

potential contamination. We are aware

of the other such sources of

radionuclide contamination in the area.

However, our mandate under the EnPA

is to set standards that apply only to the

storage or disposal of radioactive

materials in the Yucca Mountain

repository, not to these other sources.

Our standards do follow the widely

accepted principle that, to allow for the

consideration of other exposures in

developing a total acceptable dose, any

specific source accounts for only a

fraction of one’s total exposure.

Several comments supported our role

in setting standards for Yucca

Mountain. Other comments thought that

aspects of our standards duplicate

NRC’s implementation role. We believe

the provisions of this rule clearly are

within our authority and they are

central to the concept of an public

health protection standard. We also

believe our standards leave NRC the

necessary flexibility to adapt to

changing conditions at Yucca Mountain

or to impose additional requirements in

its implementation efforts, if NRC

deems them to be necessary.

We received some comments that

suggested we should have provided

more or better opportunities for public

participation in our decision making

process. For example, that we should

have rescheduled public hearings,

extended the public comment period,

and provided alternatives to the public

hearing process. We provided numerous

opportunities and avenues for public

participation in the development of

these standards. For example, we held

public hearings in four locations:

Washington, DC; Las Vegas, NV;

Amargosa Valley, NV; and Kansas City,

MO. We also opened a 90-day public

comment period and met with key

stakeholders during that time, including

Native American tribal groups. We fully

considered all comments that we

received through May 1, 2000. We have,

in effect, provided more than 240 days

of public comment on the proposal.

These measures greatly exceed the basic

requirements for notice-and-comment

rulemaking, and they are in full

compliance with the public

participation requirements of the APA.

Some comments argued that our

standards for Yucca Mountain do not

protect Nevadans to the same level as

New Mexicans around WIPP. In fact, the

individual-protection standards for

Yucca Mountain and WIPP are the

same: 15 mrem annual committed

effective dose equivalent. The

differences between the standards for

Yucca Mountain and those for WIPP

begin with the various statutes and the

subsequent regulations promulgated

under those authorities. The WIPP LWA

required us to apply our generic

radioactive waste standards (40 CFR

part 191) to WIPP. The standards for

Yucca Mountain, which we promulgate

under authority granted in the EnPA,

are site-specific, and therefore there are

some differences compared with the

standards applicable to WIPP; however,

we are confident that the standards

provide essentially the same level of

protection from radiation exposure at

both sites, as the exposure limits are the

same for both.

Many comments requested

consideration of issues outside the

scope of our authority for this

rulemaking. For example, a number of

commenters suggested that we should

explore alternative methods of waste

disposal, such as neutralizing

radionuclides. Comments also

expressed concern regarding risks of

transporting radioactive materials to

Yucca Mountain. Considerations like

these all are outside the scope of this

rulemaking. Congress delegated to us

neither the authority to postpone the

promulgation of these standards in favor

of the development of other disposal

methods nor the regulation of

transportation of waste to Yucca

Mountain.

B. What Are the Sources of Radioactive

Waste?

Radioactive wastes result from the use

of nuclear fuel and other radioactive

materials. Today, we are issuing

standards pertaining to SNF, HLW, and

other radioactive waste (we refer to

these items collectively as ‘‘radioactive

materials’’ or ‘‘waste’’) that may be

stored or disposed of in the Yucca

Mountain repository. (When we discuss

storage or disposal in this document in

reference to Yucca Mountain, please

understand that no decision has been

made regarding the acceptability of

Yucca Mountain for storage or disposal.

To save space and to avoid excessive

repetition, we will not describe Yucca

Mountain as a ‘‘potential’’ repository;

however, we intend this meaning to

apply.) These standards apply only to

facilities on the Yucca Mountain site.

Once nuclear reactions have

consumed a certain percentage of the

uranium or other fissionable material in

nuclear reactor fuel, the fuel no longer

is useful for its intended purpose. It

then is known as ‘‘spent’’ nuclear fuel

(SNF). Sources of SNF include:

(1) Commercial nuclear power plants;

(2) Government-sponsored research

and development programs in

universities and industry;

(3) Experimental reactors, such as

liquid metal fast breeder reactors and

high-temperature gas-cooled reactors;

(4) Federal government-controlled,

nuclear-materials production reactors;

(5) Naval and other Department of

Defense reactors; and

(6) U.S.-owned, foreign SNF.

It is possible to recover specific

radionuclides from SNF through

‘‘reprocessing,’’ which is a process that

dissolves the SNF, thus separating the

radionuclides from one another.

Radionuclides not recovered through

32080 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

5Health Effects of Exposure to Low Levels of

Ionizing Radiation, National Academy Press,

Washington, DC, 1990.

6The risk of interest is not at or near zero dose,

but that due to small increments of dose above the

pre-existing background level. Background in the

U.S. is typically about 3 millisieverts (mSv), that is,

300 millirem (mrem), effective dose equivalent per

year, or 0.2 Sv (20 rem) in a lifetime. Approximately

two-thirds of this dose is due to radon, and the

balance comes from cosmic, terrestrial, and internal

sources of exposure.

reprocessing become part of the acidic

liquid wastes that DOE plans to convert

into various types of solid materials.

High-level wastes (HLW) are the highly

radioactive liquid or solid wastes that

result from reprocessing SNF. The only

commercial reprocessing facility to

operate in the United States, the Nuclear

Fuel Services Plant in West Valley, New

York, closed in 1972. Since then, there

has been no reprocessing of commercial

SNF in the United States. In 1992, DOE

decided to phase out reprocessing of its

SNF, which supported the defense

nuclear weapons and propulsion

programs. The SNF that does not

undergo reprocessing prior to disposal

becomes the waste form.

Where is the waste stored now?

Today, storage of most SNF occurs in

water pools or in above-ground dry

concrete or steel canisters at more than

70 commercial nuclear-power reactor

sites across the nation. Approximately

three percent of SNF is produced by

DOE, and is in storage at several DOE

sites (see Appendix A, Figure A–2, of

DOE’s Draft Environmental Impact

Statement (DEIS) for Yucca Mountain

(DOE/EIS–0250D, Docket No. A–95–12,

Item V–A–4)). The storage of HLW

occurs at Federal facilities in Idaho,

Washington, South Carolina, and New

York.

What types of waste will be placed

into Yucca Mountain? We anticipate

that most of the waste emplaced in

Yucca Mountain will be SNF and

solidified HLW (in the rest of this

document, HLW will refer to solidified

HLW, unless otherwise noted). Under

current NRC regulations (10 CFR

60.135), liquid HLW must be solidified,

through processes such as vitrification

(mixing the waste into glass), because

non-solid waste forms are not to be

stored or disposed of in Yucca

Mountain. The DOE estimates that, by

the year 2010, about 66,000 metric tons

of SNF and 284,000 cubic meters

(containing 450 million curies of

radioactivity) of HLW in predisposal

form and 2,900 cubic meters (containing

235 million curies) of the disposable

form of HLW will be in storage at

various locations around the country

(DOE/RW–0006, Rev. 13, December

1997). For more information, see the

waste descriptions in Appendix A of

DOE’s DEIS for Yucca Mountain (DOE/

EIS–0250D, Docket No. A–95–12, Item

V–A–4).

In the future, other types of

radioactive materials could be identified

for storage or disposal in the Yucca

Mountain repository. These materials

include highly radioactive low-level

waste (LLW), known as ‘‘greater-thanClass-C waste,’’ and excess plutonium

or other fissile materials resulting from

the dismantlement of nuclear weapons.

Because the plans for the disposal of

these materials have not been finalized,

neither NRC nor DOE has analyzed their

impact upon the design and

performance of the disposal system.

However, regardless of the types of

radioactive materials that finally are

disposed of in Yucca Mountain, the

disposal system must comply with 40

CFR part 197.

C. What Types of Health Effects Can

Radiation Cause?

Ionizing radiation can cause a variety

of health effects, which can be either

‘‘non-stochastic’’ or ‘‘stochastic.’’ Nonstochastic effects are those for which the

damage increases with increasing

exposure, such as destruction of cells or

reddening of the skin. These effects

appear in cases of exposure to large

amounts of radiation. Stochastic effects

are associated with long-term exposure

to low levels of radiation. The types or

severity of stochastic effects does not

depend on the amount of exposure.

Instead, the chance that a stochastic

effect, such as cancer, will occur is

assumed to increase with increasing

exposure. For a detailed discussion of

potential health effects related to

exposure to radiation, see the preamble

to the proposed rule (64 FR 46978–

46979) and Chapter 6 of the BID.

Teratogenic effects can occur

following fetal exposure. We believe

that fetuses are more sensitive than are

adults to the induction of cancer by

radiation (see Chapter 6.5 of the BID).

The fetus also is subject to radiationinduced physical malformations, such

as small brain size (microencephaly),

small head size (microcephaly), eye

malformations, and slow growth prior to

birth. Recent studies have focused on

the apparently increased risk of severe

mental retardation (as measured by the

intelligence quotient). These studies

indicate that the sensitivity of the fetus

is greatest during 8 to 15 weeks

following conception and continues, at

a lower level, between 16 and 25

weeks.5 We do not know exactly the

relationship between mental retardation

and dose; however, we believe it

prudent to assume that there is a linear,

non-threshold, dose-response

relationship between these effects and

the dose delivered to the fetus during

the 8-to 15-week period (see Chapter 6.5

of the BID).

The NAS published its reviews of

human health risks from exposure to

low levels of ionizing radiation in a

series of reports issued between 1972

and 1990. However, scientists still do

not agree on how best to estimate the

probability of cancer occurring as a

result of the doses encountered by

members of the public 6 because it is

necessary to base estimates of these

effects on the effects observed at higher

doses (such as effects seen in the

survivors of the Hiroshima and Nagasaki

atomic bombs). Many organizations,

including the National Council on

Radiation Protection and Measurements

(NCRP), the International Commission

on Radiological Protection (ICRP), the

United Nations Scientific Committee on

the Effects of Atomic Radiation

(UNSCEAR), and the National

Radiological Protection Board of the

United Kingdom, have recommended

the use of the linear non-threshold

model for estimating cancer risks.

Over the last decade, the scientific

community has performed an extensive

reevaluation of the doses and effects in

the Hiroshima and Nagasaki survivors

(see Chapter 6.3 of the BID). These

studies have resulted in increased

estimates (roughly threefold between

1972 and 1990) of the extrapolated risk

of cancer occurring because of exposure

to environmental (background) levels of

radiation. Nonetheless, the estimated

number of health effects induced by

small incremental doses of radiation

above natural background levels

remains small compared with the total

number of fatal cancers that occur from

other causes. In addition, because

cancers that result from exposure to

radiation are the same as those that

result from other causes, it may never be

possible to identify them in human

epidemiological studies (see Chapter 6

of the BID and the example discussed

later in this section). This difficulty in

identifying stochastic radiation effects

does not mean that such effects do not

occur. It also is possible, however, that

effects do not occur as a result of these

small doses. That is, there might be an

exposure level below which there is no

additional risk above the risk posed by

natural background radiation. Sufficient

data to prove either possibility

scientifically is lacking. Thus, we

believe that the best approach is to

assume that the risk of cancer increases

linearly starting at zero dose. In other

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32081

7The traditional unit for dose equivalent has been

the rem. The unit ‘‘sievert’’ (Sv), a unit in the

International System of Units that was adopted in

1979 by the General Conference on Weights and

Measures, is now in general use throughout the

world. One sievert equals 100 rem. The prefix

‘‘milli’’ (m) means one-thousandth. The individualprotection limit being finalized today may be

expressed equivalently in either unit.

8 ‘‘Low dose rates’’ here refers to dose rates on the

order of or less than those from background

radiation.

9The risk of severe hereditary effects in the first

two generations, for exposure of the reproductive

part of the population (with both parents exposed),

is estimated to be 5 × 10¥3 per Sv (5 × 10¥5 per

rem). For all generations, the risk is estimated to be

1.2 × 10¥2 per Sv (1.2 × 10¥4 per rem). For

exposure of the entire population, which includes

individuals past the age of normal child-bearing,

each estimate is reduced to 40% of the cited value.

10Assuming a linear, non-threshold dose

response, estimated risk for mental retardation due

to exposure during the 8th through 15th week of

gestation is 4 × 10¥1 per Sv (4 × 10¥3 per rem);

under the same assumption, the estimated risk from

the 16th to 25th week is 1 × 10¥1 per Sv (1 × 10¥3

per rem).

words, any increase in exposure to

ionizing radiation results in a constant

and proportionate increase in the

potential for developing cancer.

The NAS Report stated that radiation

causes about five cancers for every

severe hereditary disorder caused by

radiation exposure. Also, NAS

concluded that nonfatal cancers are

more common than fatal cancers.

Despite this conclusion, NAS cited an

ICRP study that judged that non-fatal

cancers contribute less to overall health

impact than fatal cancers ‘‘because of

their lesser severity in the affected

individuals.’’ (NAS Report pp. 37–39).

We based our risk estimates for

exposure of the population to low-doserate radiation on fatal cancers rather

than on all cancers for the same reasons

enumerated by NAS.

For radiation-protection purposes, we

estimate (using a linear, non-threshold,

dose-response model) an average risk for

a member of the U.S. population of 5.75

in 100 (5.75 x 10¥2) fatal cancers per

sievert (Sv) 7 (5.75 × 10¥4 fatal cancers

per rem) delivered at low dose rates.8

For this calculation, as long as the

exposure rate is low, the number of

incremental cancers depends on the

amount of radiation received, not the

time period over which the dose is

delivered, because the linear nonthreshold model assumes that any

incremental dose carries a risk (see

Chapter 6.3 of the BID). For example, if

100,000 people randomly chosen from

the U.S. population each received a

uniform dose of 1 millisievert (mSv) (0.1

rem) to the entire body at a rate

equivalent to that observed from natural

background sources, the assumption is

that approximately five to six people

will die of cancer during their

remaining lifetimes because of that

exposure. These five to six deaths are in

addition to the roughly 20,000 fatal

cancers that would occur in the same

population from other causes. The risk

of fatal childhood cancer that results

from exposure while in the fetal stage is

about 3 in 100 (3 × 10¥2) per Sv (that

is, 3 × 10¥4 effects per rem). The risk

of severe hereditary effects in offspring

is estimated to be about 1 × 10¥2 per Sv

(1 × 10¥4 effects per rem). 9 The risk of

severe mental retardation from doses to

a fetus is estimated to be greater per unit

dose than the risk of cancer in the

general population. 10 However, the

period of increased sensitivity is much

shorter. Hence, at a constant exposure

rate, fatal cancer risk in the general

population remains the dominant factor.

Please see the BID for more details on

this subject.

Of course, our risk estimates do

contain some uncertainty. A recent

uncertainty analysis published by NCRP

(NCRP Report 126, Docket A–95–12,

Item II–A–13) estimated that the actual

risk of cancer from whole-body

exposure to low doses of radiation could

be between 1.5 times higher and 4.8

times lower (at the 90-percent

confidence level) than our basic

estimate of 5.75 × 10¥2 per Sv (5.75 ×

10¥4 per rem). The risks of genetic

abnormalities and mental retardation

are less well known than those for

cancer. Thus, they may include a greater

degree of uncertainty. Further, existing

epidemiological data does not rule out

the existence of a threshold. If there is

a threshold, exposures below that level

would pose no additional risk above the

risk posed by natural background

radiation. However, in spite of

uncertainties in the data and its

analysis, estimates of the risks from

exposure to low levels of ionizing

radiation are known more clearly than

are those for virtually any other

environmental carcinogen. See Chapter

6 of the BID.

D. What Are the Major Features of the

Geology of Yucca Mountain and the

Disposal System?

The geology. Yucca Mountain is in

southwestern Nevada approximately

100 miles northwest of Las Vegas. The

eastern part of the site is on NTS. The

northwestern part of the site is on the

Nellis Air Force Range. The

southwestern part of the site is on

Bureau of Land Management land. The

area has a desert climate with

topography typical of the Basin and

Range province. For more detailed

descriptions of Yucca Mountain’s

geologic and hydrologic characteristics,

and the disposal system, please see

chapter 7 of the BID and the preamble

to the proposed rule (64 FR 46979–

46980). These documents are in the

docket for this rulemaking (Docket No.

A–95–12, Items III–B–2, V–B–1).

Yucca Mountain is made of layers of

ashfalls from volcanic eruptions that

happened more than 10 million years

ago. The ash consolidated into a rock

type called ‘‘tuff,’’ which has varying

degrees of compaction and fracturing

depending upon the degree of

‘‘welding’’ caused by temperature and

pressure when the ash was deposited.

Regional geologic forces have tilted the

tuff layers and formed Yucca

Mountain’s crest (Yucca Mountain’s

shape is a ridge rather than a peak).

Below the tuff is carbonate rock formed

from sediments laid down at the bottom

of ancient seas that existed in the area.

There are two general hydrologic

zones within and below Yucca

Mountain. The upper zone is called the

‘‘unsaturated zone’’ because the pore

spaces and fractures within the rock are

not filled entirely with water. Below the

unsaturated zone, beginning at the water

table, is the ‘‘saturated zone,’’ in which

water completely fills the pores and

fractures. Fractures in both zones could

act as pathways that allow for faster

contaminant transport than would the

pores. The DOE plans to build the

repository in the unsaturated zone about

300 meters below the surface and about

300 to 500 meters above the water table

(DOE Viability Assessment (DOE/VA),

Docket No. A–95–12, Item V–A–5).

There are two major aquifers in the

saturated zone under Yucca Mountain.

The upper one is in tuff. The lower one

is in carbonate rock. Regional ground

water in the vicinity of Yucca Mountain

is believed to flow generally in a southsoutheasterly direction. See Chapters 7

and 8 of the BID for a fuller discussion

of the aquifers and the other geologic

attributes of the Yucca Mountain region.

The disposal system. The NAS Report

described the current concept of the

potential disposal system as a system of

engineered barriers for the disposal of

radioactive waste located in the geologic

setting of Yucca Mountain (NAS Report

pp. 23–27). Based on DOE’s current

design, entry into the repository for

waste emplacement would be on

gradually downward sloping ramps that

enter the side of Yucca Mountain.

Section 114(d) of the NWPAA limits the

capacity of the repository to 70,000

metric tons of SNF and HLW. Current

DOE plans project that about 90 percent

(by mass) would be commercial SNF;

and 10 percent would be defense HLW

32082 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

(NAS Report p. 23). The NAS further

stated that within 100 years after initial

emplacement of waste, the repository

would be sealed by closing the opening

to each of the tunnels and sealing the

entrance ramps and shafts (NAS Report

pp. 23, 26).

We expect the engineered barrier

system to consist of at least the waste

form (SNF assemblies or borosilicate

glass containing the HLW), internal

stabilizers for the SNF assemblies, and

the waste packages holding the waste.

Spent nuclear fuel assemblies consist of

uranium oxide, fission products, fuel

cladding, and support hardware, all of

which will be radioactive (see the What

are the Sources of Radioactive Waste?

section above).

E. Background on and Summary of the

NAS Report

Section 801(a)(2) of the EnPA directs

us to contract with NAS to conduct a

study to provide findings and

recommendations on reasonable

standards for protection of public health

and safety. Section 801(a)(2) specifically

calls for NAS to address the following

three issues:

(A) Whether a health-based standard

based upon doses to individual

members of the public from releases to

the accessible environment (as that term

is defined in the regulations contained

in subpart B of part 191 of title 40, Code

of Federal Regulations, as in effect on

November 18, 1985) will provide a

reasonable standard for protection of the

health and safety of the general public;

(B) Whether it is reasonable to assume

that a system for post-closure oversight

of the repository can be developed,

based upon active institutional controls,

that will prevent an unreasonable risk of

breaching the repository’s engineered or

geologic barriers or increasing the

exposure of individual members of the

public to radiation beyond allowable

limits; and

(C) Whether it is possible to make

scientifically supportable predictions of

the probability that the repository’s

engineered or geologic barriers will be

breached as a result of human intrusion

over a period of 10,000 years.

On August 1, 1995, NAS submitted to

us its report, entitled ‘‘Technical Bases

for Yucca Mountain Standards.’’ The

NAS Report is available for review in

the docket (Docket No. A–95–12, Item

II–A–1) and the information files

described earlier. You can order the

report from the National Academy Press

by calling 800–624–6242 or on the

World Wide Web at http://

www.nap.edu/catalog/4943.html.

1. What Were NAS’s Findings

(‘‘Conclusions’’) and Recommendations?

The NAS Report contained a number

of conclusions and recommendations.

(The EnPA used the term ‘‘findings;’’

however, the NAS Report used the term

‘‘conclusions’’). A summary of NAS’s

conclusions appears below. See pages

1–14 of the NAS Report, or the preamble

to our proposed rule (64 FR 46980), for

a list of NAS’s conclusions and

recommendations. For details on public

participation in our review of the NAS

Report, please see the preamble to the

proposed rule (64 FR 46980–46981).

Conclusions. The conclusions in the

Executive Summary of the NAS Report

(pp. 1–14) were:

(a) ‘‘That an individual-risk standard

would protect public health, given the

particular characteristics of the site,

provided that policy makers and the

public are prepared to accept that very

low radiation doses pose a negligibly

small risk’’ (later termed ‘‘negligible

incremental risk’’). (This conclusion is

the response to the issue Congress

identified in EnPA Section

801(a)(2)(A));

(b) That the Yucca Mountain-related

‘‘physical and geologic processes are

sufficiently quantifiable and the related

uncertainties sufficiently boundable that

the performance can be assessed over

time frames during which the geologic

system is relatively stable or varies in a

boundable manner;’’

(c) ‘‘That it is not possible to predict

on the basis of scientific analyses the

societal factors required for an exposure

scenario. Specifying exposure scenarios

therefore requires a policy decision that

is appropriately made in a rulemaking

process conducted by EPA;’’

(d) ‘‘That it is not reasonable to

assume that a system for post-closure

oversight of the repository can be

developed, based on active institutional

controls, that will prevent an

unreasonable risk of breaching the

repository’s engineered barriers or

increasing the exposure of individual

members of the public to radiation

beyond allowable limits.’’ (This

conclusion is the response to the issue

Congress identified in EnPA section

801(a)(2)(B));

(e) ‘‘That it is not possible to make

scientifically supportable predictions of

the probability that a repository’s

engineered or geologic barriers will be

breached as a result of human intrusion

over a period of 10,000 years.’’ (This

conclusion is the response to the issue

Congress identified in EnPA Section

801(a)(2)(C)); and

(f) ‘‘That there is no scientific basis for

incorporating the ALARA (as low as

reasonably achievable) principle into

the EPA standard or USNRC (U.S.

Nuclear Regulatory Commission)

regulations for the repository.’’

Recommendations. The

recommendations in the Executive

Summary of the NAS Report were:

(a) ‘‘The use of a standard that sets a

limit on the risk to individuals of

adverse health effects from releases from

the repository;’’

(b) ‘‘That the critical-group approach

be used’’;

(c) ‘‘That compliance assessment be

conducted for the time when the

greatest risk occurs, within the limits

imposed by long-term stability of the

geologic environment;’’ and

(d) ‘‘That the estimated risk calculated

from the assumed intrusion scenario be

no greater than the risk limit adopted for

the undisturbed-repository case because

a repository that is suitable for safe longterm disposal should be able to continue

to provide acceptable waste isolation

after some type of intrusion.’’

Other Conclusions and

Recommendations. The NAS made

other conclusions and recommendations

in addition to those listed above. Most

of them were related to or supported

those presented in the Executive

Summary.

III. What Does Our Final Rule Do?

Our rule establishes public health and

safety standards governing the storage

and disposal of SNF, HLW, and other

radioactive material in the repository at

Yucca Mountain, Nevada.

As noted earlier, section 801(a)(1) of

the EnPA gives us rulemaking authority

to set ‘‘public health and safety

standards for the protection of the

public from releases from radioactive

materials stored or disposed of in the

repository at the Yucca Mountain site.’’

The statute also directs us to develop

standards ‘‘based upon and consistent

with the findings and recommendations

of the National Academy of Sciences.’’

Section 801(a)(2) of the EnPA directs us

to contract with NAS to conduct a study

to provide findings and

recommendations on reasonable

standards for protection of the public

health and safety. Because the EnPA

directs us to act ‘‘based upon and

consistent with’’ NAS’s findings, a

major issue in this rulemaking is

whether we must follow NAS’s findings

and recommendations without

exception or whether we have

discretionary decision-making

authority.

As we discussed in the preamble to

the proposed rule, we believe we have

discretionary decision-making authority

and, therefore, are not required to adopt,

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32083

without exception, NAS’s findings and

recommendations. See 64 FR 46981–

46983 for this discussion. As a practical

matter, the difficulty of resolving this

issue is reduced because NAS expressed

some of the findings and

recommendations in a non-binding

manner. In other words, in many

instances NAS either stated its findings

and recommendations as starting points

for the rulemaking process or

recognized those recommendations that

involve public policy issues that are

addressed more properly in this public

rulemaking proceeding. However, the

report also contains some findings and

recommendations stated in relatively

definite terms. These issues present

most squarely the question of whether

we are to treat all of NAS’s findings and

recommendations as binding.

Whether the EnPA binds us to

following exactly NAS’s findings and

recommendations is a question that

warrants close attention because it

affects the scope of our rulemaking. If

we must follow every view expressed in

the NAS Report, we would have to treat

any such issue as having been addressed

conclusively by NAS. We would not

need to entertain public comment upon

the affected issues because the outcome

would be predetermined by NAS.

We believe the EnPA does not bind us

absolutely to follow the NAS Report.

Instead, we used it as the starting point

for this rulemaking. As Congress

directed, today’s rule is based upon and

consistent with the NAS findings and

recommendations. We were guided by

the panel’s findings and

recommendations because of the special

role Congress gave it and because of

NAS’s scientific expertise. However, the

entirety of our standards is the subject

of this rulemaking. Therefore, we have

not treated the views expressed by NAS

as necessarily dictating the outcome of

this rulemaking, thereby foreclosing

public scrutiny of important issues. For

the reasons described below, we believe

this interpretation of the EnPA is both

consistent with the statute and prudent,

because it avoids potential

constitutional issues. Further, this

interpretation supports an important

EPA policy objective and legal

obligation: Ensuring an opportunity for

public input regarding all aspects of the

issues presented in this rulemaking.

Section 801(a)(2) of the EnPA requires

NAS to provide ‘‘findings and

recommendations on reasonable

standards for protection of the public

health and safety.’’ This section of the

EnPA calls for NAS to address three

specific issues; however, Congress did

not place any restrictions on other

issues NAS could address. The report of

the Congressional conferees

underscored that ‘‘the (NAS) would not

be precluded from addressing additional

questions or issues related to the

appropriate standards for radiation

protection at Yucca Mountain beyond

those that are specified.’’ (H.R. Rep. No.

102–1018, 102nd Cong., 2d Sess. 391

(1992)). Thus, given the potentially

unlimited scope of NAS’s inquiry under

the statute, it could have provided

findings and recommendations that

would dictate literally all aspects of the

public health and safety standards for

Yucca Mountain, rendering our function

a merely ministerial one.

Section 801(a)(1) of the EnPA plainly

gives us the authority to issue, by

rulemaking, public health and safety

standards for Yucca Mountain. If at the

same time that Congress gave NAS the

authority to provide findings and

recommendations on any issues related

to the Yucca Mountain public health

and safety standards, Congress also

intended that NAS’s findings and

recommendations would bind us, then

Congress effectively would have

delegated to NAS a standard-setting

authority that overrides our rulemaking

authority. Carried to its logical

conclusion, under this view of the

statute, NAS would have authority to

establish the public health and safety

standards without a public rulemaking

process. Congress’ direction to EPA to

set standards ‘‘by rule’’ would be

unnecessary or relatively meaningless. It

is both reasonable and appropriate to

resolve this tension in the statute by

interpreting NAS’s findings and

recommendations as non-binding, but

highly influential, expert guidance to

inform our rulemaking.

Thus, we do not believe the statute

forces our rulemaking to adopt

mechanically NAS’s recommendations

as standards. If it did, the statutory

provisions would allow us to consider

only those issues that NAS did not

address. Further, the provisions calling

for us to use standard rulemaking

procedures in issuing the standards

would be unnecessary to reach results

that NAS already established. We

consider the NAS Report’s explicit

references to decisions that should be

made during the rulemaking process to

be support for our position.

The EnPA conference report also

reveals that Congress did not intend to

limit our rulemaking discretion. The

conference report clarifies that Congress

intended NAS to provide ‘‘expert

scientific guidance’’ on the issues

involved in our rulemaking and that

Congress did not intend for NAS to

establish the specific standards:

The Conferees do not intend for the

National Academy of Sciences, in making its

recommendations, to establish specific

standards for protection of the public but

rather to provide expert scientific guidance

on the issues involved in establishing those

standards. Under the provisions of section

801, the authority and responsibility to

establish the standards, pursuant to

rulemaking, would remain with the

Administrator, as is the case under existing

law. The provisions of section 801 are not

intended to limit the Administrator’s

discretion in the exercise of his authority

related to public health and safety issues.

(H.R. Rep. No. 102–1018, p. 391)

Our interpretation of the EnPA as not

limiting the issues for consideration in

this rulemaking is consistent with the

views we expressed to Congress during

deliberations over the legislation. The

Chair of the Senate Subcommittee on

Nuclear Regulation requested our views

regarding the bill reported by the

conference committee. The Deputy

Administrator of EPA indicated the

NAS Report would provide helpful

input. Moreover, the Deputy

Administrator pointed to the language,

cited above, stating the intent of the

conferees not to limit our rulemaking

discretion and assured Congress that

any standards for radioactive materials

that we ultimately issue would be the

subject of public comment and

involvement and would fully protect

human health and the environment (138

Cong. Rec. 33,955 (1992)).

Our interpretation also is consistent

with the role that both NAS and

Congress understood NAS would fulfill.

During the Congressional deliberations

over the legislation, NAS informed

Congress that while it would conduct

the study, it would not assume a

standard-setting role because such a role

is properly the responsibility of

government officials. (138 Cong. Rec.

33,953 (1992)) Our interpretation of the

NAS Report also avoids implicating

potentially significant constitutional

issues. Construing the EnPA as

delegating to NAS the responsibility to

determine the health and safety

standards at Yucca Mountain may

violate the Appointments Clause of the

Constitution (Art. II, sec. 2, cl. 2), which

imposes restrictions against giving

Federal governmental authority to

persons not appointed in compliance

with that Clause. In addition, the

Constitution places restrictions arising

under the separation of powers doctrine

upon the delegation of governmental

authority to persons not part of the

Federal government. We are not

concluding, at this time, that an

alternative interpretation necessarily

would run afoul of constitutional limits.

We believe, however, that it is

32084 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

reasonable both to assume that Congress

intended to avoid these issues when it

adopted section 801 of the EnPA and to

interpret the EnPA accordingly.

In summary, we do not believe we

must, in this rulemaking, adopt all of

NAS’s findings and recommendations.

The statute does, however, give NAS a

special role. As noted previously, NAS’s

findings and recommendations were

instrumental in this rulemaking. Our

proposal is consistent with those

findings and recommendations. We

included many of the findings and

recommendations in this rule. We

tended to give greatest weight to NAS’s

judgments about issues having a strong

scientific component, the area in which

NAS has its greatest expertise. In

addition, we reached final

determinations that are congruent with

NAS’s analysis whenever we could do

so without departing from the

Congressional delegation of authority to

us to promulgate, by rule, public health

and safety standards for protection of

the public. We believe our mandate

from Congress required the

consideration of public comments and

the exercise of our own expertise and

discretion.

We requested public comments

concerning: how we should view and

weigh NAS’s findings and

recommendations in the context of the

specific issues presented in this

rulemaking; whether we have given

proper consideration to NAS’s findings

and recommendations; and whether we

should give them more or less weight,

and what the resulting outcome should

be.

We received many comments

regarding our EnPA authority and our

interpretation of the NAS Report.

Several comments took issue with our

reasons for not simply adopting each of

the NAS recommendations verbatim

and stated that we are bound to do so.

One comment asserted that our

reasoning ‘‘exaggerates the impact of the

NAS Report’’ on our rulemaking

authority. However, these comments

generally recognized that we can depart

from the NAS panel’s recommendations

if it specifically stated that policy

considerations could play a role in the

decision, or if the recommendation at

issue otherwise was not definitive (e.g.,

there was disagreement among the panel

members). In particular, some

comments suggested that we cannot

include any provision if NAS did not

recommend it. We disagree with this

position. In the preamble to the

proposed rule, we clearly stated our

intentions regarding our use of the NAS

Report (see 64 FR 46980–46983). We

gave the NAS Report special

consideration as ‘‘expert scientific

guidance.’’ However, as discussed

above, we do not believe that Congress

intended the NAS Report to bind us

absolutely. We note that NAS, in its

comments on our proposed rule, did not

offer an opinion on this point. Also,

NAS acknowledges in several places in

its report that, for policy or other

reasons, we may elect to take

approaches that differ from its

recommendations. These statements

show NAS did not consider its

recommendations to be binding

directions to EPA. The NAS did,

however, identify aspects of the

proposal it believes are inconsistent

with its recommendations. A copy of

NAS’s comments on the proposal is in

the docket (Docket No. A–95–12, Item

IV–D–31). See the Response to

Comments document for additional

discussion of comments regarding our

incorporation of the NAS

recommendations (Docket No. A–95–12,

Item V–C–1).

The following sections describe our

public health and safety standards for

Yucca Mountain and the considerations

that underlie these standards. The next

section addresses the storage portion of

the standards. All of the other sections

pertain to the disposal portion of the

standards.

A. What Is the Standard for Storage of

the Waste? (Subpart A, §§ 197.1

Through 197.5)

Section 801(a)(1) of the EnPA calls for

EPA’s public health and safety

standards to apply to radioactive

materials ‘‘stored or disposed of in the

repository at the Yucca Mountain site.’’

The repository is the excavated portion

of the facility constructed underground

within the Yucca Mountain site (to be

differentiated from the disposal system,

which is made up of the repository, the

engineered barriers, and the natural

barriers). The EnPA differentiates

between ‘‘stored’’ and ‘‘disposed’’

waste, although it indicates that we

must issue standards that apply to both

storage and disposal. Congress was not

clear regarding its intended use of the

word ‘‘stored’’ in this context. Also,

NAS did not address the issue of storage

versus disposal (see § 197.2 for our

definition of ‘‘storage’’ and § 197.12 for

our definition of ‘‘disposal’’). The DOE

currently conceives of the Yucca

Mountain repository as a disposal

facility, not a storage facility; however,

this situation could change. Therefore,

we decided to interpret the statutory

language as directing us to develop

standards that apply to waste that DOE

either stores or disposes of in the Yucca

Mountain repository. The storage

standard, therefore, applies to waste

inside the repository, prior to disposal.

We received several comments

regarding our proposed definition of

‘‘disposal’’ in § 197.12, arguing that the

potential benefits of backfilling are

unknown at present. In response to

these comments, we changed the

definition in the final rule to exclude

the requirement that DOE use

backfilling in the Yucca Mountain

repository. We believe that DOE should

have the flexibility to design the

repository so that it is as protective of

public health and the environment as

possible. Therefore, in order not to

constrain DOE unnecessarily in its

choice of repository designs, we

changed the definition of ‘‘disposal’’ as

the comments suggested. Thus, under

the revised definition in our final rule,

it is no longer necessary for DOE to use

backfilling for waste disposal to occur.

Several comments also suggested that

our proposed definitions of ‘‘disposal’’

and ‘‘barrier’’ run counter to established

notions of deep geologic repositories

because they allow DOE to rely upon

both engineered and natural barriers,

instead of natural barriers alone, to

contain the radioactive material to be

stored in Yucca Mountain. These

comments suggested we amend these

definitions, as appropriate, to delete

references to engineered barriers.

According to the comments, the Yucca

Mountain repository must meet public

health and safety standards with no

assistance from manmade structures or

barriers. The EnPA mandates that we

establish site-specific standards for

Yucca Mountain. Under this mandate,

we believe it is appropriate, based on

the conditions present at Yucca

Mountain, to allow DOE the flexibility

to develop a combined system, using

engineered barriers and natural barriers,

to contain radioactive material to be

disposed of in Yucca Mountain. For

additional discussion of this topic,

please see Chapter 7 of the BID.

The DOE also will handle, and might

store, radioactive material aboveground

(that is, outside the repository). Our

existing standards for management and

storage, codified at subpart A of 40 CFR

part 191, apply to such storage

activities. Subpart A of 40 CFR part 191

requires that DOE manage and store

SNF, HLW, and transuranic radioactive

wastes at a site, such as Yucca

Mountain, in a manner that provides a

reasonable assurance that the annual

dose equivalent to any member of the

public in the general environment will

not exceed 25 millirem (mrem) to the

whole body. (Note that a demonstration

of ‘‘reasonable assurance’’ is necessary

to comply with the standard for storage,

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32085

while subpart B of both 40 CFR part 191

and today’s 40 CFR part 197 specify a

demonstration of ‘‘reasonable

expectation’’ to comply with the

disposal standards. ‘‘Reasonable

assurance’’ is an appropriate measure to

apply to storage, as the facility will be

in operation, with active monitoring and

personnel present, during this time. The

level of certainty connected with this

period of active operation is

significantly higher than can be attached

to the much longer regulatory time

period applicable to disposal standards.

See our discussion of ‘‘reasonable

expectation’’ in section III.B.2.c., What

Level of Expectation Will Meet Our

Standards?) This standard is the one

that DOE must meet for WIPP and the

greater confinement disposal (GCD)

facility. (The GCD facility is a group of

120-feet deep boreholes, located within

NTS, which contain disposed

transuranic wastes.)

We take this position regarding the

applicability of subpart A of 40 CFR part

191 because section 801 of the EnPA

specifically provides that the standards

we issue shall be the only ‘‘such

standards’’ that apply at Yucca

Mountain. Thus, the EnPA is the

exclusive authority for today’s action

regarding storage inside the repository.

The WIPP LWA does not exclude Yucca

Mountain from the management and

storage provisions in subpart A of 40

CFR part 191. The 40 CFR part 197

standards supercede our generally

applicable standards (40 CFR part 191)

only to the extent that the EnPA

requires site-specific standards for

storage inside the repository at Yucca

Mountain. Otherwise, the 40 CFR part

197 standards have no effect on our

generic standards. As noted, we

interpret the scope of section 801 to

include both storage and disposal of

waste in the repository. Thus, waste

inside the repository is subject to the

standards in today’s action. Our generic

standards (subpart A of 40 CFR part

191) will apply to waste stored at the

Yucca Mountain site, but outside of the

repository.

The storage standards in 40 CFR

191.03(a) are stated in terms of an older

dose-calculation method and are set at

an annual whole-body-dose limit of 25

mrem/yr. The storage standard for

Yucca Mountain uses a modern dosecalculation method known as

‘‘committed effective dose equivalent’’

(CEDE). Even though today’s final rule

uses the modern method of dose

calculation, we believe that the dose

level maintains a similar risk level as in

40 CFR 191.03(a) at the time of its

promulgation (see the discussion of the

different dose-calculation methods in

the What Is the Level of Protection For

Individuals? section later in this

document). The difference between

these dose calculation procedures

presents a problem in combining the

doses for regulatory purposes. However,

we have begun to develop a rulemaking

to amend both 40 CFR parts 190 and

191. That rulemaking would update

these limits to the CEDE methodology.

However, because we have not yet

finalized that change, we need to

address the calculation of doses under

the two methods in another fashion (see

the last paragraph in this section for

more detail).

As discussed in the preamble to the

proposed rule (64 FR 46983), we

considered the differences among the

conditions covered by the storage

standards in 40 CFR 191.03(a) and the

conditions that could affect storage in

the Yucca Mountain repository. The

most significant difference is that the

storage in Yucca Mountain would be

underground, whereas most storage

covered under 40 CFR part 191 is

aboveground. Otherwise, the technical

situations we anticipate under both the

existing generic standards and the

Yucca Mountain standards are

essentially the same. Also, our final rule

extends a similar level of protection as

in the 1985 version of subpart A of 40

CFR part 191. In other words, under the

40 CFR part 197 storage standard,

exposures of members of the public

from waste storage inside the repository

would be combined with exposures

occurring as a result of storage outside

the repository but within the Yucca

Mountain site (as defined in 40 CFR

197.2). The total dose could be no

greater than 150 microsieverts (μSv) (15

mrem) CEDE per year (CEDE/yr).

We requested comments regarding our

interpretation of section 801 and our

approach to coordinating the doses

originating from inside and outside the

Yucca Mountain repository. We

received two comments regarding this

issue. One comment urged us to

establish a single, new, and separate

standard for the Yucca Mountain site

that would encompass the pre-closure

operations both aboveground and in the

repository. The comment further stated

that the suggested approach would

avoid using two different rules for the

same site. This suggested approach also

would avoid the need to use the older

dose methodology currently in 40 CFR

part 191. Another comment stated that

the application of subpart A of 40 CFR

part 191 would not be inappropriate.

We considered establishing a new

standard to cover the entirety of the

management and storage operations at

Yucca Mountain, as was suggested by

one comment. This had the attractive

feature of applying one standard,

instead of two, to the management and

storage activities in and around Yucca

Mountain.

However, after considering the

comments, the wording in section

801(a)(1) of the EnPA, and the

impending rulemaking to amend

subpart A of 40 CFR part 191, we have

decided to cover the surface

management and storage activities

within the Yucca Mountain site under

40 CFR part 191 and management and

storage activities in the Yucca Mountain

repository under 40 CFR part 197.

However, the combined doses incurred

by any individual in the general

environment from these activities must

not exceed 150 μSv (15 mrem) CEDE/yr.

This will require the conversion of

doses from the surface activities from

the older dose system (under which the

40 CFR part 191 standards were

developed) into the newer system to be

able to combine the doses from the two

areas of operation. There are established

methods to do this, e.g., in the appendix

to 40 CFR part 191, but we are leaving

the methodology in this case to NRC’s

implementation process. We are

continuing to develop a rulemaking to

update the dose system used in subpart

A of 40 CFR part 191. When that

amendment is finished, the conversion

for the activities subject to subpart A of

40 CFR part 191 will be unnecessary.

B. What Are the Standards for Disposal?

(§§ 197.11 through 197.36)

Subpart B of this final rule consists of

three separate standards (or sets of

standards) that apply after final

disposal, which are discussed in more

detail in the appropriate sections of this

document. The disposal standards are:

• An individual-protection standard;

• Ground-water protection standards;

and

• A human-intrusion standard.

1. What Is the Standard for Protection of

Individuals? (§§ 197.20 and 197.25)

The first standard is an individualprotection standard. It specifies the

maximum dose that a reasonably

maximally exposed individual (RMEI)

may receive from releases from the

Yucca Mountain disposal system.

a. Is the Limit on Dose or Risk?

Section 801(a)(1) of the EnPA directed

that our standards for Yucca Mountain

‘‘shall prescribe the maximum annual

effective dose equivalent to individual

members of the public from releases to

the accessible environment from

radioactive materials stored or disposed

of in the repository * * *.’’ The EnPA

also requires us to issue our standards

32086 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

‘‘based upon and consistent with’’

NAS’s findings and recommendations.

The NAS recommended that we adopt

a risk-based standard to protect

individuals, rather than a dose-based

standard as Congress prescribed. The

NAS offered two reasons for its

recommendation. First, a risk-based

standard is advantageous relative to a

dose-based standard because it ‘‘would

not have to be revised in subsequent

rulemakings if advances in scientific

knowledge reveal that the dose-response

relationship is different from that

envisaged today’’ (NAS Report p. 64).

Second, NAS believes a risk-based

standard more readily enables the

public to comprehend and compare the

standard with human-health risks from

other sources.

We reviewed and evaluated the merits

of a risk-based standard as

recommended by NAS (NAS Report, pp.

41–ff.). However, we chose to adopt a

dose-based standard for the following

reasons. First, EnPA section 801(a)(1)

specifically directs us to promulgate a

standard prescribing the ‘‘maximum

annual dose equivalent to individual

members of the public from releases to

the accessible environment from

radioactive materials stored or disposed

of in the repository.’’ Also, the

Conference Committee specifically

stated that EPA’s standards ‘‘shall

prescribe the maximum annual dose

equivalent to individual members of the

public from releases to the accessible

environment from radioactive materials

stored or disposed of in the repository.

(H. R. Rep. 102–1018, 102nd Cong., 2d

Sess. 390 (1992)). In a situation such as

this, where both the statutory language

and the legislative history are clear, we

are obliged to implement the clearly

stated plain language of the statute and

to carry out the unambiguous intent of

the Congress.

Second, both national and

international radiation protection

guidelines developed by bodies of nongovernmental radiation experts, such as

ICRP and NCRP, generally have

recommended that radiation standards

be established in terms of dose. Also,

national and international radiation

standards, including the individualprotection requirements in 40 CFR part

191, are established almost solely in

terms of dose or concentration, not risk.

Therefore, a risk standard will not allow

a convenient comparison with the

numerous existing dose guidelines and

standards.

However, we did establish the dose

limit using the risk of developing a fatal

cancer. The level of risk, about 8.5 fatal

cancers per million members of the

population per year (see the preamble to

the proposed rule at 64 FR 46984), is a

level the Agency has judged to be

acceptable taking into account many

factors, including existing radiation

standards (such as subpart B of 40 CFR

part 191), Congressional action (the

WIPP LWA), and the comments

received on the proposed standards. On

page 46985 of the preamble to the

proposed rule, we cited a risk of

approximately seven in a million per

year. This value was based upon the

NAS risk value of 5 × 10¥2 per Sv (5

× 10¥4 per rem, NAS Report p. 47).

However, for consistency, we should

have used the value which was first

discussed on page 46979 of the

preamble to the proposed rule, 5.75 ×

10¥2 per Sv (5.75 × 10¥2 per rem), and

which is from Federal Guidance Report

13 (Docket A–95–12, Item V–A–20).

This higher value associates an annual

risk of about 8.5 in a million with 150

μSv (15 mrem). Because this underlying

risk level is a matter of public policy, it

is possible that the level could change

if future decisionmakers make a

different judgment as to the level of risk

acceptable to the general public.

Likewise, as NAS noted, it could

become necessary to change the dose

limit as a result of future scientific

findings about the cancer-inducing

aspects of radiation (i.e., in correlating

dose with risk). Therefore, no matter

which form of standard is used, it is

subject to change in the future, though

the reasons for change may not be

identical. However, either way, risk is

the underlying basis of the standards. It

is for the other reasons cited in this

section that we chose to use dose. In

addition, dose and risk are closely

related. It is possible to convert one to

the other by using the appropriate

conversion factor. We have discussed

the correlations that we used in

converting risk to dose, both in this

preamble and in Chapter 6 of the BID.

Finally, we did not receive any

comments in favor of a risk standard

that provided either a compelling

technical or policy rationale for

promulgating such a standard (see the

Response to Comments document).

Therefore, we establish a standard

stated as a dose rather than a risk.

We requested comments as to whether

the standard should be expressed as risk

or dose. Not unexpectedly, the

comments were divided between the

alternatives. Most of the comments

supported the use of dose.

One comment stated that the

calculation of a dose limit through a

probabilistic performance assessment is

a reasonable way to assure that the

repository will meet the overall health

risk objective. It is NRC’s responsibility

to determine how DOE must

demonstrate compliance with our

standards; however, we envision the use

of a probabilistic assessment for the

compliance demonstration. Another

comment stated that a dose limit is a

reasonable way for us to incorporate

cancer risk into the regulation. As

discussed to some extent in section

III.B.1.b (What Factors Can Lead to

Radiation Exposure?), and in more

detail in the preamble to the proposed

standards (beginning on 64 FR 46984),

the risk of fatal cancer, an annual risk

of about 8.5 in a million for an exposure

of 150 μSv, is the basis of the level of

protection that we have established.

A few comments supported stating

the standard in terms of risk rather than

dose. For example, NAS was concerned

that a dose standard would preclude the

public from being able to compare risks

with other hazardous materials.

According to NAS, the use of a dose

standard also makes it difficult for the

public to compare the risks inherent in

the ground-water protection standards

with the risks inherent in the

individual-protection standard. The

NAS also stated that its

recommendation to use a risk standard

did not preclude us from using a dose

standard, as long as the underlying risk

basis was clearly understood. We

believe that we have been sufficiently

clear in describing the risk basis of the

standards within this preamble and the

Response to Comments document.

b. What Factors Can Lead to

Radiation Exposure? Protection of the

public from exposure to radioactive

pollutants requires knowledge and

understanding of three factors: the

sources of the radiation, the pathways

leading to exposure, and the recipients

of the radiation dose. The standards

must consider all three factors. This

section discusses the sources of

radiation and the pathways of exposure.

The following two sections discuss the

recipients of the dose. Dose assessments

are conducted through a type of

calculational analysis called

‘‘performance assessment’’. The

performance assessment is the

quantitative analysis of the projected

behavior of the disposal system, which

considers release scenarios for the

repository and carries the analysis

through various pathways in the

environment that culminate in

exposures to members of the public.

Sources. The waste disposed of in

Yucca Mountain will contain many

radionuclides, including unconsumed

uranium, fission products (such as

cesium-137 and strontium-90), and

transuranic elements (such as

plutonium and americium).

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32087

The inventory of radionuclides over

time will depend upon the type and

amount of radionuclides originally

disposed of in the repository, the halflives of the radionuclides, and the

amount of any radionuclides formed

from the decay of parent radionuclides

(see Chapter 5 of the BID). In the time

frame of tens to hundreds of thousands

of years, the short-lived radionuclides

initially present in SNF and HLW will

decay. Therefore, the waste eventually

will have radiologic hazards similar to

a large uranium ore body; such ore

bodies naturally occur in a variety of

settings throughout the country. A

typical uranium ore body contains

relatively low concentrations of very

long-lived radionuclides similar to those

present in the radioactive wastes to be

disposed of in Yucca Mountain (see the

preamble to the final rule establishing

40 CFR part 191 (50 FR 38083,

September 19, 1985)).

Barriers to Radionuclide Movement.

To delay and limit the movement of

radionuclides into the biosphere, DOE

plans to use multiple barriers. These

barriers will be both engineered

(human-made) and natural based on the

design of, and conditions in and around,

the disposal system.

Both the natural and engineered

barriers must delay and limit releases of

radionuclides from the repository. For

example, an engineered barrier could be

the waste form. The DOE plans to

convert liquid HLW, derived from

reprocessing SNF, into a solid by

entraining the radionuclides into a

matrix of borosilicate glass. The molten

glass then would be poured into and

solidified in a second engineered

barrier, a metal container (see Chapter 7

of the BID). In addition, it is possible to

have other engineered barriers in the

repository to serve as part of the

disposal system (see Chapter 7 of the

BID).

Natural barriers at Yucca Mountain

also could slow the movement of

radionuclides into the accessible

environment. For instance, DOE plans

to construct the repository in a layer of

tuff located above the water table. The

relative dryness of the tuff around the

repository would limit the amount of

water coming into contact with the

waste, and would retard the future

movement of radionuclides from the

waste into the underlying aquifer. Any

radioactive material that dissolved in

infiltrating water, originating as surface

precipitation, still would have to move

to the saturated zone. In the saturated

zone, which lies below the unsaturated

zone, water completely fills the pores

and fractures in the rock. Minerals, such

as zeolites, in the tuff beneath the

repository could act as molecular filters

and ion-exchange agents for some of the

released radionuclides, thereby slowing

their movement. These minerals also

could limit the amount of water that

contacts the waste and could help retard

the movement of radionuclides from the

waste to the water table. This

mechanism would be most effective if

flow was predominantly through the

matrix (the pores in the rock) (see

Chapter 7 of the BID).

Pathways. Once radionuclides have

left the waste packages, water or air

could carry them to the accessible

environment. Ground water will carry

most of the radionuclides released from

the waste packages away from the

repository. However, air moving

through the mountain will carry away

those radionuclides, such as carbon-14

(14C) in the form of carbon dioxide, that

escape from the waste packages in a

gaseous form. For more detailed

discussions of the ground water and air

pathways, see the preamble to the

proposed rule (64 FR 46986) and

Chapters 8 and 9 of the BID.

Movement via water. Radionuclides

will not move instantaneously into the

water table. The length of time it will

take for radionuclides to reach the water

table depends partly on how much the

water moves via fractures or through the

matrix of the rock. Once radionuclides

reach the saturated zone, they would

move away from the disposal system in

the direction of ground water flow.

There are currently no perennial

rivers or lakes adjacent to Yucca

Mountain that could transport

contaminants. Therefore, based on

current knowledge and conditions,

ground water and its usage will be the

main pathways leading to exposure of

humans. Current knowledge suggests

that the two major ways that people

would use the contaminated ground

water are: (1) Drinking and domestic

uses; and (2) agricultural uses (see

Chapters 8 and 9 of the BID). In other

words, radionuclides that reach the

public could deliver a dose if an

individual: (1) Drinks contaminated

ground water or uses it directly for other

household uses; (2) drinks other liquids

containing contaminated water; (3) eats

food products processed using

contaminated water; (4) eats vegetables

or meat raised using contaminated

water; or (5) otherwise is exposed as a

result of immersion in contaminated

water or air or inhalation of wind-driven

particulates left following the

evaporation of the water.

Movement via air. Releases of gaseous 14C from the wastes can move through

the tuff overlying the repository and exit

into the atmosphere following release

from the waste package. Once the

radioactive gas enters the atmosphere, it

would disperse across the globe. This

global dispersion would result in

significant dilution of the 14C. The

major pathway for human exposure to

14C is the uptake of radioactive carbon

dioxide by plants that humans

subsequently eat (see Chapter 9 of the

BID).

c. What Is the Level of Protection for

Individuals? Our individual-protection

standard sets a limit of 150 μSv (15

mrem) CEDE/yr. This limit corresponds

approximately to an annual risk of fatal

cancer of about 8.5 chances in 1,000,000

(8.5 × 10¥6). It is within NAS’s

recommended starting range of 1 in

100,000 to 1 in 1,000,000 annual risk of

fatal cancer (see the NAS Report p. 5,

Docket No. A–95–12, Item II–A–1). The

NAS’s recommended risk range

corresponds to approximately 20 to 200

μSv (2 to 20 mrem) CEDE/yr.

We considered NAS’s findings and

recommendations in our determination

of the CEDE level that would be

adequately protective of human health.

We also reviewed established EPA

standards and guidance, other Federal

agencies’ standards for both radiation

and non-radiation-related actions, and

other countries’ regulations. In addition,

we evaluated guidance on dose limits

provided by national and international

non-governmental advisory groups of

radiation experts.

Section 801(a)(1) of the EnPA calls for

our Yucca Mountain standards to

‘‘prescribe the maximum annual

effective dose equivalent to individual

members of the public from releases of

radioactive materials.’’ Development of

the individual-protection standard

required us to evaluate and specify

several factors, which include the level

of protection, whom the standards

should protect, and how long the

standards should provide protection.

Determining the appropriate dose level

is ultimately a question of both science

and public policy. As NAS stated: ‘‘The

level of protection established by a

standard is a statement of the level of

the risk that is acceptable to society.

Whether posed as ‘How safe is safe

enough?’ or as ‘What is an acceptable

level?’, the question is not solvable by

science’’ (NAS Report p. 49).

We requested comment regarding the

reasonableness of our proposed 15

mrem CEDE/yr individual-protection

standard. We received many comments,

some of which supported the proposal,

while others stated that we should make

the level higher or lower. This final rule

establishes a limit of 15 mrem CEDE/yr

for the reasons discussed in the

preamble to the proposed rule (see 64

32088 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

FR 46984 and following). Principally,

the reasons were: This level is within

the NAS-recommended range (which

NAS based upon its review of other

Federal actions, guidelines developed

by national and international advisory

bodies, and the regulations in other

countries); the fact that many existing

standards are at this level, particularly

the EPA standards (40 CFR part 191)

applicable to WIPP (in the case of some

older standards, the equivalence is

based upon more recent understanding

of the damage that radiation can cause);

and, after consideration of the

comments and the site-specific

conditions, we believe that this level is

a sufficiently stringent level of

protection for this situation.

Many comments argued that the

proposed level was too low. For

example, a few comments preferred a

dose level of 25 mrem/yr to maintain

consistency with current NRC

regulations. Another comment

advocated a dose level of 70 mrem/yr,

given the long time frames, the national

importance of the repository, and other

factors. Other comments thought that

the standard should be lower. Several of

these comments supported a limit of 5

mrem/yr. Other comments supported a

zero dose limit.

Some comments stated that, though

they preferred a zero-release standard,

they realized that our level was

implementable. We agree that the

disposal program should ideally have a

goal of no releases. However, we believe

it is incumbent upon us to set a

stringent, yet reasonable, standard. We

are establishing a standard that provides

comparable protections to those of other

activities related to radioactive and nonradioactive wastes. Given the current

state of technology, it may not be

possible to provide absolute certainty

that there will be no releases over a

10,000 year or longer time frame.

Therefore, we have attempted to

establish a standard that is protective

that can be implemented to show

compliance.

Our final consideration in selecting a

level of protection was guidance from

national and international nongovernmental bodies, such as ICRP and

NCRP, which have recommended a total

annual dose limit for an individual of 1

mSv (100 mrem) effective dose from

exposure to all radiation sources except

background and medical procedures.

The dose level of 1 mSv (100 mrem)

corresponds to an annual risk of fatal

cancer of about 6 in 100,000 (6 × 10¥5).

In its Publication No. 46, ‘‘Radiation

Protection Principles for the Disposal of

Solid Radioactive Waste,’’ the ICRP

recommends apportionment of the total

allowable radiation dose among specific

practices. (Docket No. A–95–12, Item V–

A–12). The apportionment of the total

dose limit among different sources of

radiation is used to ensure that the total

of all included exposures is less than 1

mSv (100 mrem) CED/yr. Thus, ICRP

recommends that national authorities

apportion or allocate a fraction of the 1

mSv (100 mrem)-CED/yr limit to

establish an exposure limit for SNF and

HLW disposal facilities. Most other

countries have endorsed the

apportionment principle.

There are multiple sources of

potential radionuclide contamination on

and near NTS, one of which is the

Yucca Mountain site. Portions of NTS

have been subjected to both

underground and aboveground nuclear

weapon detonations. A substantial

quantity of radionuclides was created by

these tests. An estimated inventory of

300 million curies remains underground

(see Appendix II of the BID; Chapter 8

of DOE’s Draft Environmental Impact

Statement for Yucca Mountain (DOE/

EIS/0250D), Docket No. A–95–12, Item

V–A–4; and Nevada Risk Assessment/

Management Program (NRAMP), Docket

No. A–95–12, Item V–A–17). Elsewhere

on the NTS, DOE is burying LLW in

near-surface trenches and TRU

radioactive waste has been disposed of

in the Greater Confinement Disposal

facility. Finally, there is a commercial

LLW disposal system located west of

Yucca Mountain near Beatty, Nevada.

Each of these facilities could have

releases of radioactivity into the ground

water (see Chapter 8 of DOE’s Draft

Environmental Impact Statement for

Yucca Mountain (DOE/EIS/0250D),

Docket No. A–95–12, Item V–A–4; and

Nevada Risk Assessment/Management

Program (NRAMP), Docket No. A–95–

12, Item V–A–17). The regional flow of

ground water is believed to be generally

from the locations where some of these

practices have occurred toward the area

where radionuclides released from the

Yucca Mountain disposal system are

presumed to go (see Nevada Risk

Assessment/Management Program

(NRAMP), Docket No. A–95–12, Item V–

A–17). The total of the releases from

these sources should be constrained to

the total dose limit of 1 mSv (100 mrem)

CED/yr, as recommended by ICRP,

because the releases from these sources

could affect the same group of people.

The potential doses from these other

sources might contribute to individual

doses for the reasonably maximally

exposed individual (RMEI) over

different time frames. According to

Chapter 8 of the DEIS for Yucca

Mountain (DOE/EIS/0250D, Docket No.

A–95–12, Item V–A–4), potential

releases from LLW management and

disposal operations may contribute very

small individual doses. A quantitative

attempt to allocate potential dose from

these other sources would be highly

speculative; however, it would be

reasonable to maintain the allocation

approach reflected in the established

dose limits in both the United States

and internationally.

In summary, based on our review of

the guidance, regulations, and standards

cited above, and the NAS Report, we are

establishing a standard of 150 μSv (15

mrem) CEDE/yr for the Yucca Mountain

disposal system (40 CFR 197.13). This

level is 15% of the ICRP-recommended

total dose limit. It falls within the range

of standards used in other countries and

the range recommended by NAS, and is

also consistent with the individualprotection requirement in 40 CFR part

191. This level will be the CEDE level

with which the dose over the

compliance period must be compared.

The compliance period is the time

interval over which projections of the

performance of the disposal system

must be made for the purpose of

assessing the future performance of the

disposal system (see the How Far Into

the Future is it Reasonable to Project

Disposal System Performance? section

later in this document for more detail).

d. Who Represents the Exposed

Population? To determine whether the

Yucca Mountain disposal system

complies with our standard, DOE must

calculate the dose received by some

individual or group of individuals

exposed to releases from the repository

and compare the calculated dose with

the limit established in the standard.

The standard specifies, therefore, the

representative individual for whom

DOE must make the dose calculation.

We expect that NRC will define the

details, beyond those which we have

specified, necessary for the dose

calculation.

Our approach for the protection of

individuals. We examined two possible

approaches: the critical group (CG)

approach recommended by NAS (NAS

Report, pp. 49–54, Appendix C, and

Appendix D) and the reasonably

maximally exposed individual (RMEI)

approach. The goal in representing the

exposed population is to estimate the

level of exposure that is protective of

the vast majority of individuals in that

population, but still within a reasonable

range of potential exposures. We chose

the RMEI approach because we believe

it more appropriately protects

individuals and is less speculative to

implement than the CG approach given

the unique conditions present at Yucca

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32089

Mountain. Also, it remains a

conservative but reasonable approach

that accomplishes the same goal as the

CG approach.

The NAS definition of critical group.

The NAS Report recommended that we

use the risk to a CG as the basis for the

individual-protection standard. The CG

would be the group of people that,

based upon cautious, but reasonable,

assumptions, has the highest risk of

incurring health effects due to releases

from the disposal system. In its report,

NAS discussed two specific examples of

critical groups. The NAS considered the

probabilistic critical group based upon a

present-day farming community to be

more appropriate and less reliant on

speculative assumptions than the other

critical group it discussed, which was

based upon subsistence farming.

However, following due consideration,

we decided that the subsistence-farmer

approach discussed by NAS would be

inappropriate, since we could not find

nor did any other party demonstrate that

there is the subsistence-farmer lifestyle

at, or downgradient from, Yucca

Mountain. For detailed discussions of

NAS’s CG approaches, please see the

preamble to the proposed rule, 64 FR

46986–46988, and the NAS Report at

pp. 49–54 and 145–159.

The Reasonably Maximally Exposed

Individual (RMEI). As just mentioned,

NAS recommended that the standard

incorporate a CG approach for

estimating individual exposures from

repository release projections (NAS

Report p. 52). As NAS pointed out, the

CG approach has been examined

internationally and recommendations

for its application have been proposed

(NAS Report, Chapter 2). In addition to

recommending the use of the CG

approach, NAS posited the use of a

‘‘probabilistic’’ CG, which is a CG

evaluated using probabilistic techniques

for assessing exposures, not only for the

parameters that affect repository

releases but also for the probability that

an individual will use contaminated

ground water away from the site. As

NAS points out, ‘‘the components of a

probabilistic computational approach

have considerable precedent in

repository performance, we are not

aware that they have previously been

combined to analyze risks to critical

groups’’ (NAS Report, Appendix C). In

that sense, NAS ‘‘probabilistic’’ CG is a

departure from the more widely

understood application of the CG

concept. The approach we have chosen

embodies the intent of the

internationally accepted concept to

protect those individuals most at risk

from the proposed repository but

specifies one or a few site-specific

parameters at their maximum values.

We chose to use an approach involving

limiting exposure to a defined

‘‘reasonably maximally exposed

individual’’, the RMEI. There are

similarities between the probabilistic

CG and RMEI approaches, and also

some significant differences arising from

the Yucca Mountain site, that caused us

to select the RMEI alternative (see also

‘‘Characterization and Comparison of

Alternative Dose Receptors for

Individual Radiation Protection for a

Repository at Yucca Mountain’’, Docket

No. A–95–12, Item V–B–3).

In both approaches, the attempt is

made to consider a range of conditions

for the exposed individuals that affect

exposures, including geographic

population distributions, lifestyles, and

food consumption patterns for

populations at risk. The characteristics

of the RMEI are defined from

consideration of current population

distribution and ground water usage,

and average food consumption patterns

for the population in question. Such

characterizations typically are done by

surveying existing populations, and a

‘‘composite’’ RMEI is defined with one

or more parameters that significantly

affect exposure estimates set at high

values so that the individual is

‘‘reasonably maximally exposed.’’ The

CG approach typically is used under the

assumption of a larger population

within which a smaller group (the

critical group) incurs a more

homogeneous risk from exposures, in

contrast to the larger population group

where exposures will vary widely.

Characteristics of the CG also are

derived from information or

assumptions about the potentially

exposed population; however, a small

group within the larger population,

rather than a composite individual, is

defined. Both the CG and the RMEI are

then located above the path of the

contamination plume and the exposure

variations are calculated as a function of

the parameters that control radionuclide

transport from the contamination source

(here, the repository). The

‘‘probabilistic’’ CG defined in the NAS

Report (Appendix C) adds an additional

layer of analytical detail by introducing

the idea that the path of the

radionuclide contamination is subject to

considerable uncertainty and the

exposure of the CG is further qualified

by the probability that the

contamination plume is tapped by the

CG at any point in time. This approach

assumes the location of the probabilistic

CG is fixed independently of the

projected path(s) for radionuclide

migration from the repository, and the

potential exposures then are a direct

function of the probability that the

contamination plume reaches the

location of the group. The more

common approach to locating the CG,

for the purpose of estimating exposures,

is to determine where the group can

receive exposures from the

contamination plume and then locating

the CG at that place, regardless of

whether a population is currently at that

location or not. Both of these

approaches appear to give essentially

the same maximum dose levels to at

least some individuals, because at some

point in time the CG would tap into the

contamination plume and receive the

exposures. However, if assumed to be

widely distributed geographically, many

members of the CG could receive

considerably smaller doses, or no dose,

resulting in an average dose which does

not reflect the intent of the CG concept.

Overall, as explained further, below, the

difference in the distribution of doses

using the CG approach depends upon

the implementation details describing

how the total spectrum of dose

assessments would be calculated.

We relied upon many factors in

making the decision to use the RMEI

concept. First, this approach is

consistent with widespread practice,

current and historical, of estimating

dose and risk incurred by individuals

even when it is impossible to specify or

calculate accurately the exposure habits

of future members of the population, as

in this case where it is necessary to

project doses for very long periods.

Second, we believe that the RMEI

approach is sufficiently conservative

and that it is fully protective of the

general population (including women

and children, the very young, the

elderly, and the infirm). The risk factor

upon which the dose level was

established is very small, 5.75 chances

in 10,000,000 per mrem for fatal cancer.

The lifetime risk then is this factor

multiplied by the total dose received in

each year of the individual’s lifetime.

We believe that the risk prior to birth is

very similar to this risk level; however,

relative to the rest of that individual’s

lifetime, the difference is small. Third,

we believe that it provides protection

similar to the CG recommended by

NAS. The RMEI model uses a series of

assumptions about the lifestyle of a

hypothetical individual. This belief was

supported by NAS in its comments on

the proposed 40 CFR part 197. The NAS

agreed that EPA’s RMEI approach is

‘‘broadly consistent with the TYMS

report’s recommendation’’ (Docket No.

A–95–12, IV–D–31). Fourth, it is

possible to build the desired degree of

32090 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

conservatism into the model through

choices of assumed values of RME

parameters. However, these values

would be within certain limits because

we require the use of Yucca Mountainspecific characteristics in choosing

those parameters and their values. In

subpart B of 40 CFR part 197, we

establish a framework of assumptions

for NRC to incorporate into its

implementing regulations. Fifth, we

believe that the RMEI approach is more

straightforward in its application than

the CG approach (particularly the

probabilistic CG approach). The RMEI

can reasonably be assumed to incur

doses from the plume of contamination.

By locating the RMEI for dose

assessment purposes above the plume’s

direct path, high-end dose estimates

will result. A probabilistic CG implies

some, or even many, locations of the

members across a broader geographic

area than the plume covers. This

dispersal inescapably involves

additional decisions for the method to

be used for combining dose estimates

for the group members and comparison

against regulatory limits and could

average some, or many, doses with a

zero magnitude. In addition, specifying

certain assumptions regarding

consumption habits, e.g., requiring the

assumption that the RMEI drinks a highend estimate of 2 liters/day of ground

water and that dietary intake is

determined using surveys of today’s

population in the Town of Amargosa

Valley, assure that the RMEI is

‘‘reasonably maximally’’ exposed

(§ 197.21). We believe this approach is

consistent with the NAS

recommendation of ‘‘cautious, but

reasonable’’ assumptions for repository

dose assessments (NAS Report p. 6).

With these assumptions about the

location to be used for dose assessments

and food and water consumption, we

believe that the RMEI approach would

result in dose estimates comparable to a

small CG. For a CG, food and water

consumption patterns would also be

determined from surveys of the local

population and, possibly, by some

assumptions to push the dose

assessments toward higher-end dose

estimates. The important difference

between the composite RMEI and

probabilistic CG approaches is in the

assumed distribution of the group

members relative to the projected path

of radionuclide contamination from the

repository. And, finally, sixth, we

previously have used the RMEI

approach in our regulations (see FR

22888, 22922, May 29, 1992). We have

not used the CG approach. For example,

the WIPP certification criteria (40 CFR

part 194) use an approach involving

estimating doses to individuals rather

than to a defined CG.

We believe the RMEI approach is

more direct and easily understood than

the probabilistic CG approach because

the uncertainties of estimating doses for

a randomly located population is

avoided, but the approach is still

‘‘cautious, but reasonable.’’ We believe

that the ‘‘probabilistic’’ CG described by

NAS would give essentially the same

high-end dose results for situations

where the group is small, located in a

relatively small area, and is above the

path of the contamination plume.

However, this was not the concept

recommended by NAS. Therefore, we

believe our RMEI approach captures the

essential ‘‘cautious, but reasonable’’

approach recommended by NAS while

minimizing speculative aspects of the

probabilistic CG approach. We do not

mean to imply that a CG approach

would never be appropriate, or that we

would never use a CG approach in a

regulatory action or other decision.

However, in this particular site-specific

situation, had we used a CG, we would

have considered it necessary to define it

in detail (in terms of size and location)

using cautious, but reasonable,

assumptions, but as discussed

elsewhere in this document, we believe

that the RMEI approach is preferable for

Yucca Mountain.

Our RMEI is a theoretical individual

representative of a future population

group or community termed ‘‘ruralresidential’’ (see Chapter 8 of the BID for

a description of this concept). The DOE

will calculate the CEDE the RMEI

receives using cautious, but reasonable,

exposure parameters and parametervalue ranges as described below. The

NRC would use the projected CEDE in

determining whether DOE complies

with the standard. The DOE will

perform the dose calculation to estimate

exposure resulting from releases from

the waste into the accessible

environment based upon the

assumption of present-day conditions in

the vicinity of Yucca Mountain. Under

our standard, the RMEI will have food

and water intake rates, diet, and

physiology similar to those of

individuals in communities currently

living in the downgradient direction of

flow of the ground water passing under

Yucca Mountain.

We did, however, receive comments

from tribal representatives expressing

concern regarding an alternative

approach. The Paiute and Shoshone

Tribes stated that they use the Yucca

Mountain area for traditional and

customary purposes, including

traditional gathering, and it is their

belief that these uses should be

incorporated into the formula upon

which the final standards are based. We

considered the Tribes’ comments, but,

for several reasons explained below, we

conclude, after considering their

description of tribal uses of the area,

that the rural-residential RMEI is fully

protective of tribal resources.

First, the tribal use of natural springs

is apparently occurring in the vicinity of

Ash Meadows, since we are not aware

of another area downgradient from

Yucca Mountain where water discharges

in natural springs, with the possible

exception of springs in the more distant

Death Valley. These natural springs are

likely fed by the ‘‘carbonate’’ aquifer,

which is beneath the ‘‘alluvial’’ aquifer

being used Town of Amargosa Valley

(including at Lathrop Wells) now, and

which we assume will be used in the

future. The available data indicate that

although it is likely that the alluvial

aquifer would be contaminated by

releases from the potential Yucca

Mountain repository, flow is generally

upward from the carbonate aquifer into

the overlying aquifers, suggesting that

there is no potential for radionuclides to

move downward into the carbonate

system. If downward movement were to

occur, however, radionuclide

concentrations would be significantly

diluted in the larger carbonate flow

system. As a result, springs fed from the

carbonate aquifer would have lower

contamination levels than would wells

at the Lathrop Wells location, which tap

aquifers closer to, and more directly

affected by, the source of potential

contamination. A more extensive

discussion of the aquifer systems and

geology in the Yucca Mountain area

may be found in sections II.D and

III.B.4.e of this preamble, and Chapters

7 and 8 of the BID.

Second, the tribal use of wildlife and

non-irrigated vegetation should not

contribute significantly to total

individual dose estimates. Gaseous

releases from the repository are not a

significant contributor to individual

doses (NAS report, pg. 59) through

inhalation or rainfall, and should

contribute less to contamination of

wildlife and non-irrigated vegetation

than the use of contaminated well water

for raising crops and animals for food

consumption. We believe our

requirement that DOE and NRC base

food ingestion patterns on current

patterns for the agricultural area directly

down gradient from the repository is a

more conservative requirement.

Third, the dose incurred by the RMEI

is calculated at a location closer to the

disposal system than the Ash Meadows

area (approximately 18 km versus 30

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32091

km). The RMEI would receive a higher

dose from ground water consumption

than would an individual at Ash

Meadows, even if the carbonate aquifer

could be contaminated by repository

releases, for the reasons mentioned

above.

Fourth, the RMEI is assumed to be a

full-time resident continually exposed

to radiation coming from the disposal

system. It appears that the tribal uses are

intermittent and involve resources

which are less likely to be

contaminated, resulting in lower doses

than those to the RMEI.

Presently, we expect the ground water

pathway to be the most significant

pathway for exposure from

radionuclides transported from the

repository (NAS Report p. 48; Chapter 8

of the BID). Our initial evaluation of

potential exposure pathways from the

disposal system to the RMEI suggests

that the dominant fraction of the dose

incurred by the RMEI likely will be from

ingestion of food irrigated with

contaminated water (see Chapter 8 of

the BID). It is possible, however, that

DOE and NRC will determine that

another exposure pathway is more

significant. Consequently, DOE and

NRC must consider and evaluate all

potentially significant exposure

pathways in the dose assessments. As a

result of the dose assessments using

different combinations of parameter

values, there will be a distribution of

potential doses incurred by the RMEI.

The NRC will use the mean value of that

distribution of RMEI doses to determine

DOE’s compliance with the individualprotection standard. We requested

comments regarding both the use of the

RMEI approach and the use of the

higher of the mean or median value to

determine compliance with the

individual-protection standard. We also

requested comments regarding the

desirability of adopting the CG approach

rather than the RMEI approach. We

further requested that comments

supporting the CG approach address the

level of detail our rule should include

for the parameters used to describe the

CG. Comments on various aspects of the

RMEI approach appear later in this

section. Comments on the mean/median

compliance level are in the answer to

Question #13 in section IV.

We received comments supporting

both the RMEI and the CG approaches.

For example, one commenter felt that

NRC’s proposed licensing regulation for

Yucca Mountain (64 FR 8640, February

22, 1999) was more consistent with the

NAS recommendation because it

included a farming community CG (see

NRC’s proposed 10 CFR 63.115). This

commenter also stated that the proposed

10 CFR part 63 contains the appropriate

level of detail to define the CG. Other

commenters recommended the use of a

subsistence farmer CG approach on the

grounds that such an approach is more

protective than the rural-residential

RMEI. These groups stated that the

RMEI is ‘‘purely speculative.’’

As noted earlier, NAS recommended

using the CG concept. This approach

can account for differences in age, size,

metabolism, habits, and environment to

avoid heavily skewing the results based

upon personal traits that make certain

people more or less vulnerable to

radiation releases than the average

within the group. In comparison, under

the RMEI approach, the dose that the

RMEI incurs is calculated using some

maximum values and some average

values for the factors that are important

to estimating dose. Physical differences

such as age, size, and metabolism are

also incorporated into the risk value for

development of cancer, in effect making

the RMEI a ‘‘composite’’ individual.

This procedure also projects doses that

are within a reasonably expected range

rather than projecting the most extreme

cases.

Regarding the comments stating that

the RMEI is ‘‘purely speculative,’’ we

agree that the RMEI approach is

speculative; however, it is less

speculative than the scenario suggested

in the comments supporting the use of

a subsistence farmer. We are not aware

of any subsistence farmers (as defined

by the comments) in Amargosa Valley.

If we used the comments’ approach we

would, therefore, be engaging in even

more speculation than we are by using

a current lifestyle. Any future projection

involves speculation. Our basis for

using the RMEI is that we are following

NAS’s recommendation to use current

technology and living patterns because

speculation upon future society and

lifestyle variations can be endless and

not scientifically supportable (NAS

Report p. 122). As stated earlier, the

danger in defining a probabilistic CG is

that it may be skewed by including

randomly located people who will have

minimal exposures, resulting in less

conservative estimates for the group.

Given the conditions at Yucca

Mountain, we considered this to be a

very real possibility. We consider using

a composite individual to be a much

simpler means of accomplishing the

same purpose while maintaining more

control over who is represented in the

exposure assessments. Had we opted to

use a probabilistic CG, we would have

identified certain characteristics of the

group in order for it to meet our intent,

as we have done with the RMEI.

Overall, we believe that the RMEI

approach both meets the intent of NAS

and the EnPA and continues a

regulatory methodology that we

previously have used successfully.

Further, though it recommended that we

use a CG approach, NAS seemed to

recognize that a non-CG approach could

accomplish the same purpose. In its

report, NAS stated ‘‘[i]t is essential that

the scenario that is ultimately selected

be consistent with the critical-group

concept that we have advanced’’ (NAS

Report p. 10, emphasis added). In its

comments on the proposed 40 CFR part

197, NAS stated that our RMEI approach

is ‘‘broadly consistent with the TYMS

report’s recommendations’’ (Docket No.

A–95–12, Item IV–D–31). Given this

acknowledgment by NAS, and that our

evaluation of public comments

identified no significant deficiencies in

our proposed approach, we see no

compelling reason to change our

position that the RMEI is the

appropriate method to use at Yucca

Mountain.

Exposure scenario for the RMEI. A

major part of the exposure scenario is

the RMEI’s location. To make this

decision, we collected and evaluated

information about the Yucca Mountain

area’s natural geologic and hydrologic

features that may preclude drilling for

water at a specific location, such as

topography, geologic structure, aquifer

depth and quality, and water

accessibility. Based upon this

information and the current

understanding of ground water flow in

the Yucca Mountain area, it appears that

individuals theoretically could reside

anywhere along the projected ground

water flow path extending from FortyMile Wash, starting approximately five

kilometers (km) from the repository

location, to the southwestern part of the

Town of Amargosa Valley, Nevada,

where the ground water is close to the

land surface and where most of the

farming in the area occurs. However, in

practice an individual’s ability to reside

at any particular point depends upon

the available resources. To explore these

variations, we developed four scenarios

(described in the preamble to the

proposed rule). See Chapter 8 of the BID

for a fuller version of our evaluation of

the factors associated with these

scenarios. In developing scenarios, we

assumed that the level of technology

and economic considerations affecting

population distributions and life styles

in the future are the same as today (for

more detail on this assumption, see the

What Do Our Standards Assume About

the Future Biosphere? section below).

See below for a fuller discussion of our

32092 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

choice for the RMEI’s location. We

requested comments regarding the

appropriateness of these scenarios and

our preferred choice.

We selected a rural-residential RMEI

as the basis of our individual exposure

scenario. We assume that the ruralresidential RMEI, is exposed through

the same general pathways as a

subsistence farmer. However, this RMEI

would not be a full-time farmer. Rather,

this RMEI, as part of a community

typical of Amargosa Valley, might do

personal gardening and earn income

from other sources of work in the area.

We assume further that the RMEI drinks

two liters per day of water contaminated

with radionuclides, and some of the

food (based upon surveys) consumed by

the RMEI is from the Town of Amargosa

Valley. We consider the consumption of

two liters per day of drinking water to

be a high-exposure value because

people consume water and other liquids

from outside sources, such as

commercial products. We intended that

it would push the dose estimates

towards a ‘‘reasonably maximal

exposure.’’ Similarly, we assume that

local food production will use water

contaminated with radionuclides

released from the disposal system. We

believe this lifestyle is similar to that of

most people living in Amargosa Valley

today.

We received comments stating that:

we should be more specific in defining

characteristics of the RMEI; we should

take future changes in population, land

use, climate, and biota into

consideration; and that something other

than a rural-residential lifestyle would

be a more appropriate choice.

One comment suggested that we

should be more specific in setting the

location, behavior, and lifestyle, or

allow NRC to make that choice. There

were also a few comments stating that

NRC should specify the parameter

values. We believe that we have

specified the characteristics of the ruralresidential RMEI in the detail necessary,

given our current understanding, for the

concept to be implemented as we

intend. We also believe that our

specification of the parameter values

such as location for the RMEI and

drinking water intake rate is appropriate

and necessary for our standard to be

implemented in the context in which

we developed it. We further believe we

have the authority to specify other

parameter values; however, we believe

that NRC, in its role as the licensing

authority, can and should set most of

the details for implementing the

standard, such as water usage in the

community where the RMEI resides.

Also, under our standard, NRC has the

flexibility to make any assumptions,

other than those we specified

(assumptions we specified include

location, water intake rate, and diet

reflective of current residents of the

Town of Amargosa Valley), if alternative

selections prove to be more appropriate

for implementing the standard as we

intend. The location we specified is not

a fixed point but rather it must be in the

accessible environment above the

highest concentration of radionuclides

in the plume of contamination. To

assess water usage in the hypothetical

community, DOE and NRC could use an

approach similar to the representative

volume approach described later in this

document (How Does Our Rule Protect

Ground Water?). In doing so, the NRC

may wish to consider the volume we

specified as the representative volume

for ground water protection (i.e., 3,000

acre-feet). Given the extreme technical

difficulty in modeling the small

volumes of water used by an individual,

it would be reasonable for DOE and

NRC to assume that the RMEI is one of

a number of people (in the hypothetical

‘‘community’’ of which the RMEI is a

member) withdrawing water from the

plume of contamination. Such an

approach would involve assumptions

about the number of people

withdrawing water and the various uses

for which the water is withdrawn,

which would define the overall volume

of water. The RMEI would then be a

representative person using water with

‘‘average’’ concentrations of

radionuclides. These assumptions

should be reflective of current water

uses in the projected path of the plume

of contamination.

Among the comments regarding our

assumptions about future populations,

land use, climate, and biota, one stated

that it is arrogant, as well as insensitive,

to assume that all future people will be

like us today, and that it is unrealistic

to assume that future population

distribution, patterned as it is today,

will be static. The comment is correct in

that there are many possible futures.

However, it is necessary to limit

speculation about possible futures so

that the performance assessments can

provide meaningful input into the

decision process and the decision

process itself is not confounded with

speculative alternatives. Therefore, we

agreed with and followed NAS when it

recommended, ‘‘[i]n view of the almost

unlimited possible future states of

society * * * we have recommended

that a particular set of assumptions be

used about the biosphere * * * we

recommend the use of assumptions that

reflect current technologies and living

patterns’’ (NAS Report p. 122).

A similar question arose when we

developed the implementing regulations

for WIPP. We resolved the question by

developing the ‘‘future states’’

assumption (see 40 CFR 194.25). The

position we have taken for the Yucca

Mountain standards is consistent with

our previous approach to this question.

There was a spectrum of suggestions

recommending alternative RMEIs (from

a fetus to the elderly and infirm). For

example, one comment suggested

pregnant women and the unborn within

their wombs, children, the infirm, and

the elderly as appropriate RMEIs. Other

commenters urged using a subsistence

farmer. Regarding the various ages and

stages of human development, the risk

value used for the development of

cancer is an overall average risk value

(see Chapter 6 of the BID for more

details) that includes all exposure

pathways, both genders, all ages, and

most radionuclides. However, it does

not cover the ‘‘unborn within the

womb.’’ It is thought that the risk to the

unborn is similar to that for those who

have been born; however, the exposure

period for the unborn is very short

compared to the rest of the individual’s

average lifetime (see Chapter 6 of the

BID for a discussion of cancer risk from

in utero exposure). Therefore, the risk is

proportionately lower and thus would

not have a significant impact upon the

overall risk incurred by an individual

over a lifetime. On the other end of the

spectrum, radiation exposure of the

elderly at the levels of the individualprotection standard would be less than

the overall risk value because they have

fewer years to live and, therefore, fewer

years for a fatal cancer to develop.

Some comments on our RMEI

characteristics stated that they need to

be more site-specific and should

consider the alternative lifestyles of

Native Americans. Other comments

stated that the characteristics and

location of the RMEI are

implementation issues that should be

left for determination by NRC. We

believe that the final rule achieves the

proper balance of site-specific

characteristics that is fully protective of

the public health and safety, and that

the attributes of the RMEI specified in

this rule are necessary to ensure that the

Yucca Mountain disposal system

achieves the level of protection that we

intend.

Location of the RMEI. The location of

the RMEI is a basic part of the exposure

scenario. We considered locations

within a region occupying an area

bordering Forty-Mile Wash, within a

few kilometers of the repository site, to

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32093

the southwestern border of the Town of

Amargosa Valley. This region, which we

believe is hydrologically downgradient

from Yucca Mountain, can be

considered as three general subareas.

See the preamble to the proposed rule,

64 FR 46989–46990, for a fuller

discussion of these subareas.

Based upon these considerations of

the subareas, we proposed the

intersection of U.S. Route 95 and

Nevada State Route 373, known as

Lathrop Wells, as the point where the

RMEI would reside. We consider it

improbable that the rural-residential

RMEI would occupy locations

significantly north of U.S. Route 95,

because the rough terrain and increasing

depth to ground water nearer Yucca

Mountain would likely discourage

settlement by individuals because

access to water is more difficult than it

would be a few kilometers farther south.

Also, there are currently several

residents and businesses near this

location whose source of water is the

underlying aquifer (which we

understand flows beneath Yucca

Mountain). Therefore, we believe it is

reasonable to assume that a rural

community could be located near this

intersection in the future, and that

population increases in the short term

would cluster preferentially around the

main roads through the area.

We are requiring that the RMEI be

located in the accessible environment

(i.e., outside the controlled area) above

the highest concentration of

radionuclides in the plume of

contamination. Based upon a review of

available site-specific information (see

Chapter 8 of the BID), we have chosen

the latitude of the southern edge of the

Nevada Test Site (corresponding to the

line of latitude 36° 40′ 13.6661′′ North

(described in Docket A–95–12, Item V–

A–29)), as the southernmost extent of

the controlled area, i.e., DOE and NRC

could establish the southern boundary

of the controlled area farther north (and

presumably the location of the RMEI),

but no farther south (see Where Will

Compliance With the Ground Water

Standards be Assessed?). (Even if the

RMEI were to be located north of this

line of latitude, the RMEI must still have

the characteristics described in

§ 197.21.). As noted above, we proposed

the intersection of U.S. Route 95 and

Nevada State Route 373 (i.e., Lathrop

Wells) as the location of the RMEI. After

further review, we determined that the

southern edge of NTS would be a more

appropriate maximum distance from the

repository footprint than the location we

proposed because of Nye County’s plans

to develop the area between the

intersection at Lathrop Wells and NTS

and the potential for members of the

public to reside in that same area

(Docket No. A–95–12, Items V–14, 15,

16). This location is also slightly more

protective than the Lathrop Wells

location since it is approximately 2 km

closer to the repository footprint, but

still falls within the conditions which

led us to propose the Lathrop Wells

intersection, e.g., the ground water is

not significantly deeper than at the

intersection and the soil conditions are

the same.

Commercial farming occurs today

farther south, in the southwestern

portion of the Town of Amargosa Valley

in an area near the California border and

west of Nevada State Route 373.

However, soil conditions in the vicinity

of Lathrop Wells are similar to those in

southwestern Amargosa Valley.

Therefore, it should be feasible for the

RMEI to grow some food, using

contaminated water tapped by a well.

We believe that it is reasonable to

assume that other gardening, farming,

and raising of domestic animals could

occur using contaminated water (see

Appendix IV of the BID). We have

specified that selected parameters, such

as the percentage of food grown by the

RMEI, should reflect the lifestyles of

current residents of the Town of

Amargosa Valley.

Finally, we believe a rural-residential

RMEI slightly north of Lathrop Wells

would be among the most highly

exposed individuals downgradient from

Yucca Mountain, even though the

ground water nearer the repository

could contain higher concentrations of

radionuclides. If individuals lived

nearer the repository, they would be

unlikely to withdraw water from the

significantly greater depth for other than

domestic use, and in the much larger

quantities needed for gardening or

farming activities because of the

significant cost of finding and

withdrawing the ground water. It is

possible, therefore, for an individual

located closer to the repository to incur

exposures from contaminated drinking

water, but not from ingestion of

contaminated food. Based upon our

analyses of potential pathways of

exposure, discussed above, we believe

that use of contaminated ground water

(e.g., drinking water and irrigation of

crops) would be the most likely

pathway for most of the dose from the

most soluble, more mobile

radionuclides (such as technetium–99

and iodine–129). The percentage of the

dose that results from irrigation would

depend upon assumptions about the

fraction of all food consumed by the

RMEI from gardening or other crops

grown using contaminated water, which

should reflect the lifestyle of current

residents of the Town of Amargosa

Valley. Therefore, the exposure for an

RMEI located approximately 18 km

south of the repository (where ingestion

of locally grown contaminated food is a

reasonable assumption) actually would

be more conservative than an RMEI

located much closer to the repository

who is exposed primarily through

drinking water. We also are establishing

that protection of a rural-residential

RMEI would be protective of the general

population downgradient from Yucca

Mountain (see the How Do Our

Standards Protect the General

Population? section below).

As stated above, the method of

calculating the RMEI dose is to select

average values for most parameters

except one or a few of the most

sensitive, which are set at their

maximum. We believe that an RMEI

location above the highest concentration

in the plume of contamination in the

accessible environment and a

consumption rate of two liters per day

of drinking water from the plume of

contamination represent high-end

values for two of these factors. The NRC

may identify additional parameters to

assign high-end values in projecting the

dose to the RMEI. To the extent

possible, NRC should use site-specific

information for any remaining factors.

For example, NRC should use sitespecific projections of the amount of

contaminated food that would be

ingested in the future. The NRC might

base projections upon surveys that

indicate the percentage of the total diet

of Amargosa Valley residents from food

grown in the Amargosa Valley area.

We requested comment regarding the

potential approaches and assumptions

for the exposure scenario to be used for

calculating the dose incurred by the

RMEI, particularly whether:

(1) Based upon the above criteria,

there is now sufficient information for

us to adequately support a choice for the

RMEI location in the final rule or should

we leave that determination to NRC in

its licensing process based upon our

criteria;

(2) Another location in one of the

three subareas identified previously

should be the location of the RMEI; and

(3) Lathrop Wells and an ingestion

rate of two liters per day of drinking

water are appropriate high-end values

for parameters to be used to project

doses to the RMEI.

Of the three subjects listed above, the

only comments we received suggested

different locations for the RMEI. A few

commenters thought that the Lathrop

Wells location is appropriate. However,

a number of others stated that the

32094 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

RMEI’s location should be at the edge of

the footprint of the repository. Finally,

one commenter suggested that 30

kilometers away from the repository (in

the current farming area in southern

Amargosa Valley) would be reasonable;

however, this commenter also stated

that Lathrop Wells would be acceptable

using the rural-residential scenario to

provide conservatism to protect public

health and safety.

As stated earlier, we are designating

the location above the point of highest

concentration in the plume of

contamination in the accessible

environment (no farther south than 36°

40′ 13.6661′′ North) as the location of

the RMEI. This point would be

approximately 18 kilometers south of

the repository footprint. We do not

believe that an RMEI likely would live

much farther north of the compliance

point (toward Yucca Mountain) because

of the increasing depth to ground water

and the increasing roughness of the

terrain. In addition, we believe that, at

approximately 18 km, a rural-resident

RMEI will likely have the highest

potential doses in the region because of

both drinking contaminated water and

eating food grown using contaminated

water. That is, the rural resident at 18

km will receive a higher dose than

would an individual living much closer

to Yucca Mountain because the cost of

extracting the water likely will allow

only drinking the water and not having

a garden capable of supplying a portion

of an individual’s annual food

consumption (see Chapters 7 and 8 of

the BID). Likewise, we do not believe

that hypothesizing that the RMEI lives

30 km away is a cautious, but

reasonable, assumption because: (1) At

30 km, the RMEI likely would use water

that contains much lower

concentrations of (i.e., more diluted)

radionuclides; (2) the downgradient

residents closest to Yucca Mountain are

currently near Lathrop Wells; and (3)

Nye County’s short-term projections (20

years) show population growth at and

near that location (see Docket No. A–

95–12, Items V–A–14, V–A–15, and V–

A–16). Therefore, a distance of 18 km

adds to the conservatism and provides

more protection of public health,

relative to one commenter’s suggested

distance of 30 km.

There were a few other comments

related to the location of the RMEI. For

example, one comment stated that the

location should take into account the

geology and hydrology of the site rather

than be chosen in advance. Another

comment believes that we should base

the location upon the ability of the

RMEI to sustain itself consistent with

topography and soil conditions. Further,

this commenter believes that depth to

ground water should not be a factor

because it is impossible to predict either

human activities or economic

imperatives.

We determined the point of

compliance for the individualprotection standard using site-specific

factors and NAS’s recommendation to

use current conditions (NAS Report p.

54). In preparing to propose a

compliance point for the RMEI, we

collected and evaluated information on

the natural geologic and hydrologic

features, such as topography, geologic

structure, aquifer depth, aquifer quality,

and the quantity of ground water, that

may preclude drilling for water at a

specific location (see Chapter 7 of the

BID). For example, as stated above, we

do not believe that a rural-residential

individual would occupy areas much

closer to Yucca Mountain because of the

increasingly rough terrain and the

increasing depth to ground water. With

increasing depth to ground water come

higher costs: (1) To drill for water; (2)

to explore for water; and (3) to pump the

water to the surface. We agree that it is

impossible to predict either human

activities or economic imperatives.

Therefore, we followed NAS’s

recommendation to use current

conditions to avoid highly speculative

scenarios. This approach leads us to

considering the depth to ground water

as a key factor in determining the

location and activities of the RMEI. The

current location of people living in the

vicinity of the repository is a reflection

of this key factor.

And, finally, one commenter stated

that the proposed RMEI concept forces

DOE to assume the RMEI will withdraw

water from the highest concentration

within the plume without consideration

of its likelihood. Forcing such an

assumption neglects the low probability

that a well will intersect the highest

concentration within the plume.

This commenter’s approach, which

would use a probabilistic method to

determine the radionuclide

concentration withdrawn by the RMEI,

is similar to one of the example CG

approaches that NAS provided in its

report (NAS Report Appendix C). The

NAS approach would use statistical

sampling of various parameters, i.e.,

considering the likelihood (probability)

of various conditions existing to arrive

at a dose for comparison to the standard.

However, we did not use the

probabilistic CG approach for the

following reasons: (1) There is no

relevant experience in applying the

probabilistic CG approach, (2) the CG

approach is very complex relative to the

RMEI approach and is difficult to

implement in a manner that assures it

would meet the requirements of

defining a CG, and (3) we are concerned

that this approach does not appear to

identify clearly which individual

characteristics describe who is being

protected. Finally, a significant majority

of the public comments we received on

the NAS Report opposed the

probabilistic CG approach. We further

believe that prudent public health

policy requires that our approach be

followed to provide reasonable

conservatism. In this case, this is not a

prediction of exactly whom will be

exposed as much as it is a reasonable

test of the performance of the repository.

To allow the probability of any

particular location being contaminated

is not a prudent approach to the

ultimate goal of testing acceptable

performance.

e. How Do our Standards Protect the

General Population? Pursuant to section

801(a)(2)(A) of the EnPA, one of the

issues to be addressed by NAS in its

study is whether an individualprotection standard will provide a

reasonable standard for protection of the

health and safety of the general public.

NAS concluded that an individualprotection standard could provide such

protection in the case of the Yucca

Mountain disposal system. The NAS

premised this conclusion on the

condition that the public and

policymakers would accept the idea that

extremely small individual radiation

doses spread out over large populations

pose a negligible risk (NAS Report p.

57). The NAS refers to this concept as

‘‘negligible incremental risk’’ (NIR)

(NAS Report p. 59). See the preamble to

the proposed rule for a detailed

discussion of NAS’s concept of NIR (64

FR 46990–46991).

We agree with NAS that an

individual-protection standard can

adequately protect the general

population near Yucca Mountain

because of the particular characteristics

of the Yucca Mountain site. However,

we chose not to adopt either a negligible

incremental dose (NID) or NIR level

because we are concerned that such an

approach is not appropriate in all

circumstances, and because of

reservations regarding NAS’s reasoning

and analysis. We based our

determination that an individual-risk

standard is adequate to protect both the

local and general population on

considerations unique to the Yucca

Mountain site. This is not, however, a

general policy judgment by us regarding

other uses of the NID or NIR concepts.

As noted in the preamble to the

proposal (64 FR 46990), NAS referred to

the NID level of 10 μSv (1 mrem)/yr per

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32095

source or practice recommended by the

NCRP. The International Atomic Energy

Agency (IAEA) has made similar

recommendations regarding exemptions

in its Safety Series No. 89, ‘‘Principles

for the Exemption of Radiation Sources

and Practices from Regulatory Control’’

(1998) (Docket No. A–95–12, Item II–A–

6). The IAEA has recommended that

individual doses not exceed 10 μSv (1

mrem)/yr from each exempt practice

(IAEA Safety Series No. 89, p. 10). The

IAEA’s recommendations relate to

criteria for exempting whole sources or

practices, such as waste disposal or

recycling generally, not whether

radiation doses from a portion of a given

practice, such as the release of gases

from a specific geologic repository, may

be considered negligible. Finally, the

IAEA’s recommendations intend the

exemption to be for sources and

practices ‘‘which are inherently safe’’

(IAEA Safety Series No. 89, p. 11). It is

not clear that the low individual doses

or risks projected from gaseous releases

from the Yucca Mountain repository

should be considered on their own as a

‘‘source’’ or ‘‘practice,’’ given the

definitions of these terms in IAEA’s

Safety Series No. 89. Further, given the

extraordinarily large inventory of longlived radionuclides to be disposed of in

the Yucca Mountain repository, it is not

clear that such a source or practice

should be considered inherently safe.

Also, we believe it is inappropriate to

not calculate a radiation dose merely

because the dose rate from a particular

source is small.

Further, we do not believe it is

appropriate to apply the NIR concept to

consideration of population dose. A

recent NCRP report questions the

application of the NID concept to

population doses. According to NCRP

Report No. 121: ‘‘(a) Concept such as the

NID (Negligible Incremental Dose)

provides a legitimate lower limit below

which action to further reduce

individual dose is unwarranted, but it is

not necessarily a legitimate cut-off dose

level for the calculation of collective

dose. Collective dose addresses societal

risk while the NID and related concepts

address individual risk.’’ (Principles

and Application of Collective Dose in

Radiation Protection, NCRP Report No.

121, Docket No. A–95–12, Item II–A–8).

Based upon this principle, we think it

inappropriate to use the NID or NIR

concept to evaluate whether an

individual-protection standard

adequately protects the general

population.

In summary, we are establishing an

individual-protection standard for

Yucca Mountain that will limit the

annual radiation dose incurred by the

RMEI to 150 μSv (15 mrem) CEDE. At

the same time, we chose not to adopt a

separate limit on radiation releases for

the purpose of protecting the general

population. Instead, we recommended

in our proposal that DOE estimate and

consider collective dose in its analyses.

We based this recommendation upon

several factors. The first factor is NAS’s

projection of extremely small doses to

individuals resulting from air releases

from Yucca Mountain. That dose level

is well below the risk corresponding to

our individual-protection standard for

Yucca Mountain. It is also well below

the level that we have regulated in the

past through other regulations. Further,

while we decline to establish a general

Negligible Incremental Risk (NIR) level,

we do agree with NAS that estimating

the number of health effects resulting

from a 0.0003 mrem/yr dose equivalent

rate (NAS Report p. 59), in addition to

the dose rate from background radiation,

in the general population is uncertain

and controversial. The second major

factor is that, based upon current and

site-specific conditions near Yucca

Mountain, there is not likely to be great

dilution resulting in exposure of a large

population. In addition, we are

establishing additional ground water

protection standards that would set

specific limits to protect users of ground

water and that protect ground water as

a resource. Finally, we require that all

of the pathways, including air and

ground water, be analyzed by DOE and

considered by NRC under the

individual-protection standard. We

requested comment on this approach.

We requested that commenters who

disagree with this approach specifically

address why it is inappropriate for the

Yucca Mountain disposal system and

make suggestions about how we might

reasonably address this issue.

Most comments supported not

establishing a collective-dose limit for

Yucca Mountain. Two comments

supported our decision not to establish

an NIR or NID level. The NAS went

further by also opposing our suggestion

that DOE estimate collective dose for

use in examining design alternatives

because it is inconsistent with the NAS

Report and with our conclusion that a

collective-dose limit is unnecessary for

the purpose of protecting the general

public. On page 57 of its report, NAS

stated:

‘‘Earlier in this chapter, we recommend the

form for a Yucca Mountain standard based on

individual risk. Congress has asked whether

standards intended to protect individuals

would also protect the general public in the

case of Yucca Mountain. We conclude that

the form of the standards we have

recommended would do so, provided that

policy makers and the public are prepared to

accept that very low radiation doses pose a

negligibly small risk. This latter requirement

exists for all forms of the standards,

including that in 40 CFR (part) 191. We

recommend addressing this problem by

adopting the principle of negligible

incremental risk to individuals.

‘‘The question posed by Congress is

important because limiting individual dose

or risk does not automatically guarantee that

adequate protection is provided to the

general public for all possible repository sites

or for the Yucca Mountain site in particular.

As described in the previous section, the

individual-risk standard should be

constructed explicitly to protect a critical

group that is composed of a few persons most

at risk from releases from the repository. The

standards are then set to limit the risk to the

average member of that group. Larger

populations outside the critical group might

also be exposed to a lower, but still

significant, risk. It is possible that a higher

level of protection for this population

represented by a lower level of risk than the

one established by the standards might be

considered.’’

The NAS also states: ‘‘(O)n a

collective basis, the risks to future local

populations are unknowable. We

conclude that there is no technical basis

for establishing a collective populationrisk standard that would limit risk to the

nearby population of the proposed

Yucca Mountain repository’’ (NAS

Report p. 120)

After consideration of comments

received on this question, we have

determined that it is not necessary for

us to recommend that DOE calculate

collective dose, primarily because we

believe the individual-protection

standard will adequately protect the

general population.

f. What Do Our Standards Assume

About the Future Biosphere? For

assessments of potential exposures,

there are two important aspects of

defining the future biosphere

characteristics: the selection of

parameter values to define the natural

characteristics of the site, and the

assumptions necessary to define the

characteristics of the potentially

exposed population. Examples of the

site’s natural characteristics include

rainfall projections and the hydrologic

characteristics of the rocks through

which radionuclides may migrate.

Examples of the assumptions necessary

to define the potentially exposed

population’s characteristics include

assumptions regarding population

distributions, lifestyles, and eating

habits.

In conducting required analyses of

repository performance, including the

performance assessment for determining

compliance with the standards, the

assessment for determining compliance

32096 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

11We define ‘‘boundable’’ to mean that these

properties and processes fall within certain limits.

We are defining probabilities of occurrence below

with the ground water standards, and

the human-intrusion analysis, DOE and

NRC may not assume that future

geologic, hydrologic, and climatic

conditions will be the same as they are

at present. We require that these

conditions be varied within reasonably

ascertainable bounds over the required

compliance period. We are imposing

this requirement, which is consistent

with the recommendation of the NAS

Report, because we believe it is possible

to reasonably bound the parameter

values in the performance assessment

that relate to these conditions.

To avoid unsupportable speculation

regarding human activities and

conditions, we believe it is appropriate

to assume that other parameters

describing human activities and

interactions with the repository (such as

the level of human knowledge and

technical capability, human physiology

and nutritional needs, general lifestyles

and food consumption patterns of the

population, and potential pathways

through the biosphere leading to

radiation exposure of humans) will

remain as they are today. Consistent

with the NAS Report, we believe there

may be an essentially unlimited number

of predictions that could be made about

future human societies, with an

unlimited number of potential impacts

on the significance of future risk and

dose effects. Regulatory decision making

involving many speculative scenarios

for future societies and impacts would

become extraordinarily difficult without

any demonstrable improvement in

public health and safety and should be

avoided as much as possible. Therefore,

DOE and NRC must assume that future

states applicable to the repository,

except for geologic, hydrologic, and

climatic conditions, will remain

unchanged from the time of licensing.

Comments we received on this subject

strongly favored our approach,

particularly with respect to changes in

natural conditions. The comments noted

that climatic variations should be

expected to occur over the time frames

for which performance projections are

made because the climate has changed

in the past. Another reason to consider

climatic changes is that these changes

could have a significant effect on

repository performance in comparison

to performance projections made using

current day conditions. Comments also

pointed out the seismically active

nature of the area and implied that DOE

should examine the effects of seismic

activity on the disposal system’s

performance. Here again, we require

DOE to consider variations in geologic

conditions. The approach we proposed

on this subject is consistent with the

approach we used for the WIPP

certification (40 CFR 194.25) and NAS’s

recommendations. We received no

comments opposing this approach.

g. How Far Into the Future Is It

Reasonable To Project Disposal System

Performance? The NAS recommended

that the time over which compliance

should be assessed (the compliance

period) should be ‘‘the time when the

greatest risk occurs, within the limits

imposed by long-term stability of the

geologic environment’’ (NAS Report p.

7). The NAS stated that the bases for its

recommendation were technical, not

policy, considerations (NAS Report pp.

54–56). The NAS acknowledged,

however, that this is not solely a

technical decision, and that policy

considerations could be important to the

decision (NAS Report p. 56). We agree

that the selection of the compliance

period necessarily involves both

technical and policy considerations. For

example, as NAS pointed out, we could

decide that it is appropriate to establish

similar policies for managing risks

‘‘from disposal of both long-lived

hazardous nonradioactive materials and

radioactive materials’’ (NAS Report p.

56). Such a decision necessarily would

result in a compliance period that is less

than the period of geologic stability. As

NAS recognized, we had to consider, in

this rulemaking, both the technical and

policy issues associated with

establishing the appropriate compliance

period for the performance assessment

of the Yucca Mountain disposal system.

We offered for comment two

alternatives for the compliance period

for the individual-protection standard.

One alternative was to adopt a

compliance period as the time to peak

dose within the period of geologic

stability. The second alternative was to

adopt a fixed time period during which

the repository must meet the disposal

standards.

For the reasons discussed below, we

selected the second alternative, which

establishes a regulatory time period of

10,000 years. Therefore, the peak dose

within 10,000 years after disposal must

comply with the individual-protection

standard. In addition, we require

calculation of the peak dose within the

period of geologic stability. The intent

of examining the disposal system’s

performance after 10,000 years is to

project its longer-term performance. We

require DOE to include the results and

bases of the additional analyses in the

EIS for Yucca Mountain as an indicator

of the future performance of the

disposal system. The rule does not,

however, require that DOE meet a

specific dose limit after 10,000 years.

We have concerns regarding the

uncertainties associated with such

projections, and whether very long-term

projections can be considered

meaningful; however, existing

performance assessment results indicate

that the peak dose may occur beyond

10,000 years (see Chapter 7, Section 7.3,

of the BID). Such results may, therefore,

give a more complete description of

repository behavior. We acknowledge,

however, that these results, because of

the inherent uncertainties associated

with such long-term projections, are not

likely to be of the quality necessary to

support regulatory decisions based upon

a quantitative analysis and thus need to

be considered cautiously. In any case,

these very long-term projections will

provide more complete information on

disposal system performance.

As discussed below in section III.B.2.a

(What Limits Are There on Factors

Included in the Performance

Assessment?), the principal tool used to

assess compliance with the individualprotection standard is a quantitative

performance assessment. This method

relies upon sophisticated computer

modeling of the potential processes and

events leading to releases of

radionuclides from the disposal system,

subsequent radionuclide transport, and

consequent health impacts. To consider

compliance for any length of time,

several facets of knowledge and

technical capability are necessary. First,

the scientific understanding of the

relevant potential processes and events

leading to releases must be sufficient to

allow quantitative estimates of projected

repository performance. Second,

adequate analytical methods and

numerical tools must exist to

incorporate this understanding into

quantitative assessments of compliance.

Third, scientific understanding, data,

and analytical methods must be

adequately developed to allow

evaluation of performance with

sufficient robustness to judge

compliance with reasonable expectation

over the regulatory period. Finally, the

analyses must be able to produce

estimated results in a form capable of

comparison with the standards.

The NAS evaluated these

requirements for Yucca Mountain. First,

it concluded that those aspects of

disposal system and waste behavior that

depend upon physical and geologic

properties can be estimated within

reasonable limits of uncertainty. Also,

NAS believed that these properties and

processes are sufficiently understood

and boundable 11 over the long periods

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32097

which events are considered very unlikely and need

not be considered in performance assessments. We

are not otherwise constraining DOE or NRC in

identifying bounding limits.

at issue to make such calculations

possible and meaningful. The NAS

acknowledged that these factors cannot

be calculated precisely, but concluded

that there is a substantial scientific basis

for making such calculations. The NAS

concluded that by considering

uncertainties and natural variations, it

would be possible to estimate, for

example, the concentration of

radionuclides in ground water at

different locations and the times of

gaseous releases. Second, NAS

concluded that the mathematical and

numerical tools necessary to evaluate

repository performance are available or

could be developed as part of the

standard-setting or compliancedetermination processes. Third, NAS

concluded that: ‘‘[s]o long as the

geologic regime remains relatively

stable, it should be possible to assess the

maximum risks with reasonable

assurance’’ (NAS Report p. 69). The

NAS used the term ‘‘geologic stability’’

to describe the situation where geologic

processes, such as earthquakes and

erosion, that could affect the

performance assessment of the Yucca

Mountain disposal system are active or

are expected to occur (NAS Report pp.

91–95). Based upon the use of the terms

‘‘stable’’ and ‘‘boundable’’ throughout

the NAS Report, one can infer that NAS

applied the term ‘‘geologic stability’’ or

‘‘stable’’ to the situation where the rate

of processes and numeric range of

individual physical properties could be

bounded with reasonable certainty. The

subsequent use of the term ‘‘stable’’ will

not imply static conditions or processes.

Rather, it will describe the properties

and processes that can be bounded.

Finally, NAS found that the established

procedures of risk analysis should

enable the results of each performance

simulation of the disposal system to be

combined into a single estimate for

comparison with the standard.

We previously considered the

question of the appropriate compliance

period for land disposal of SNF, HLW,

and TRU radioactive waste in the 40

CFR part 191 standards, where we

promulgated a generic compliance

period of 10,000 years. We set the 40

CFR part 191 compliance period at

10,000 years for three reasons:

(1) After that time, there is concern

that the uncertainties in compliance

assessment become unacceptably large

(50 FR 38066, 38076, September 19,

1985);

(2) There are likely to be no

exceptionally large geologic changes

during that time (47 FR 58196, 58199,

December 29, 1982); and

(3) Using time frames of less

than10,000 years does not allow for

valid comparisons among potential

sites. For example, for 1,000 years, all of

the generic sites analyzed appeared to

contain the waste approximately equally

both because of long ground water travel

times at well-selected sites (47 FR

58196, 58199, December 29, 1982) and

because of the containment capabilities

of the engineered barrier systems (58 FR

66401, December 20, 1993).

The purpose of geologic disposal is to

provide long-term barriers to the

movement of radionuclides into the

biosphere (NAS Report p. 19). As

described earlier, DOE plans to locate

the Yucca Mountain repository in tuff

about 300 meters above the local water

table. When the waste packages release

nongaseous radionuclides, the released

radionuclides most likely will be

transported by water that moves through

Yucca Mountain from the surface

toward the underlying aquifer both

horizontally between individual tuff

layers and vertically downward,

through fractures in the tuff layers. Once

the radionuclides reach the aquifer, the

ground water will carry them away from

the repository in the direction of ground

water flow in the aquifer. The most

probable route for exposing humans to

radiation resulting from releases from

the Yucca Mountain disposal system is

via withdrawal of contaminated water

for local use. In the case of Yucca

Mountain, DOE estimates that most

radionuclides would not reach currently

populated areas within10,000 years,

because of the expected performance of

the engineered barrier system (see

Chapter 7 of the BID).

This finding alone seems to indicate

that the compliance period for Yucca

Mountain should be longer than 10,000

years to be protective; however, NAS

concluded that the need to consider the

exposures when they are calculated to

occur must be weighed against the

uncertainty associated with such

calculations (NAS Report p. 72). As

discussed below, exposures could occur

over tens-of thousands to hundreds-ofthousands of years. As the compliance

period is extended to such lengths,

however, uncertainty generally

increases and the resulting projected

doses are increasingly meaningless from

a policy perspective. The NAS stated

that there are significant uncertainties in

a performance assessment and that the

overall uncertainty increases with time.

Even so, NAS found that, ‘‘* * * there

is no scientific basis for limiting the

time period of the individual-risk

standard to 10,000 years or any other

value’’ (NAS Report p. 55). The NAS

also stated that data and analyses of

some of the factors that are uncertain

early in the assessment might become

more certain as the assessment

progresses(NAS Report p. 72), though

this would tend to apply more to

assessments covering very long periods

(i.e., longer than 10,000 years). Also,

NAS stated that many of the

uncertainties in parameter values

describing the geologic system are not

due to the length of time but rather to

the difficulty in estimating values of site

characteristics that vary across the site.

Thus, NAS concluded that the

probabilities and consequences of the

relevant features, events, and processes

that could modify the way in which

radionuclides are transported in the

vicinity of Yucca Mountain, including

climate change, seismic activity, and

volcanic eruptions, ‘‘are sufficiently

boundable so that these factors can be

included in performance assessments

that extend over periods on the order of

about one million years’’ (NAS Report p.

91). As discussed below, we believe that

such an approach is not practical for

regulatory decisionmaking, which

involves more than scientific

performance projections using computer

models.

Today’s rule requires that DOE

demonstrate compliance for a period of

10,000 years after disposal. As

discussed above, NAS concluded ‘‘there

is no scientific basis for limiting the

time period of the individual-risk

standard to 10,000 years or any other

value’’ (NAS Report p. 55). Despite

NAS’s recommendation, we conclude

that there is still considerable

uncertainty as to whether current

modeling capability allows

development of computer models that

will provide sufficiently meaningful and

reliable projections over a time frame up

to tens-of-thousands to hundreds-ofthousands of years. Simply because

such models can provide projections for

those time periods does not mean those

projections are meaningful and reliable

enough to establish a rational basis for

regulatory decisionmaking.

Furthermore, we are unaware of a policy

basis that we could use to determine the

‘‘level of proof’’ or confidence necessary

to determine compliance based upon

projections of hundreds-of-thousands of

years into the future. The NAS indicated

that analyses of the performance of the

Yucca Mountain disposal system

dealing with the far future can be

bounded; however, a large and

cumulative amount of uncertainty is

32098 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

associated with those numerical

projections. Setting a strict numerical

standard at a level of risk acceptable

today for the period of geologic stability

would ignore this cumulative

uncertainty and the extreme difficulty of

using highly uncertain assessment

results to determine compliance with

that standard. We requested comments

regarding the reasonableness of

adopting the NAS-recommended

compliance period or some other

approach in lieu of the 10,000-year

compliance period, which we favor and

describe below. We also sought

comment regarding whether it is

possible to implement the NASrecommended compliance period in a

reasonable manner and how that could

be done.

The selection of the compliance

period for the individual-protection

standard involves both technical and

policy considerations. It was our

responsibility to weigh both during this

rulemaking. In addition to the technical

guidance provided in the NAS Report,

we considered several policy and

technical factors that NAS did not fully

address, as well as the experience of

other EPA and international programs.

As a result of these considerations, we

are establishing a 10,000-year

compliance period with a quantitative

limit and a requirement to calculate the

peak dose, using performance

assessments, if the peak dose occurs

after 10,000 years. Under this approach,

DOE must make the performance

assessment results for the post-10,000-

year period part of the public record by

including them in the EIS for Yucca

Mountain.

In its discussion of the policy issues

associated with the selection of the time

period for compliance, NAS suggested

that we might choose to establish

consistent risk-management policies for

long-lived, hazardous, nonradioactive

materials and radioactive materials

(NAS Report p. 56). We previously

addressed the 10,000-year compliance

period in the regulation of hazardous

waste subject to land-disposal

restrictions. Although they are subject to

treatment standards to reduce their

toxicity, some of these wastes, such as

heavy metals, can essentially remain

hazardous forever. Land disposal, as

defined in 40 CFR 268.2(c), includes,

but is not limited to, any placement of

hazardous waste in land-based units

such as landfills, surface

impoundments, and injection wells.

Facilities may seek an exemption from

land disposal restrictions by

demonstrating that there will be no

migration of hazardous constituents

from the disposal unit for as long as the

waste remains hazardous (40 CFR

268.6). This period may include not

only the operating phase of the facility,

but also what may be an extensive

period after facility closure. With

respect to injection wells, we

specifically required a demonstration

that the injected fluid will not migrate

from the injection well within 10,000

years (40 CFR 148.20(a)). We chose the

10,000-year performance period

referenced in our guidance regarding

no-migration petitions, in part, to be

equal to time periods cited in draft or

final DOE, NRC, and EPA regulations

(10 CFR part 960, 10 CFR part 60, or 40

CFR part 191, respectively) governing

siting, licensing, and releases from HLW

disposal systems. With respect to other

land-based units regulated under the

Resource Conservation and Recovery

Act (RCRA) hazardous-waste

regulations, we concluded that the

compliance period for a no-migration

demonstration is specific to the waste

and site under consideration. For

example, for the WIPP no-migration

petition, we found that ‘‘it is not

particularly useful to extend this model

beyond 10,000 years into the future

* * * (However, t)he agency does

believe * * * that modeling over a

10,000-year period provides a useful

tool in assessing the long-term stability

of the repository and the potential for

migration of hazardous constituents’’

(55 FR 13068, 13073, April 6, 1990).

Thus, establishing a 10,000 year

compliance period for Yucca Mountain

is consistent with risk-management

policies that we have established for

other long-lived, hazardous materials.

Second, the individual-protection

requirements in 40 CFR part 191 (58 FR

66398, 66414, December 20, 1993) have

a compliance period of 10,000 years.

The 40 CFR part 191 standards apply to

the same types of waste and type of

disposal system as will be present at

Yucca Mountain. Therefore, the use of

a 10,000 year time period in this

regulation is consistent with 40 CFR

part 191. However, as we explained in

the What is the History of Today’s

Action? section earlier in this document,

by statute the 40 CFR part 191

requirements do not apply to Yucca

Mountain (WIPP LWA, section 8(b)).

Nevertheless, we deem this consistency

appropriate because both sets of

standards apply to the same types of

waste. Moreover, though the WIPP LWA

exempts Yucca Mountain from the 40

CFR part 191 standards, it does not

prohibit us from imposing standards on

Yucca Mountain that are similar to the

40 CFR part 191 standards, if, as

discussed previously, we determine in

this rulemaking that the imposition of

such standards is appropriate. The

question of uncertainties over long time

frames and the use of performance

projections over those time frames for

regulatory decisionmaking has been

examined a number of times in our

rulemaking (40 CFR parts 191 and 194)

with a consistent conclusion that 10,000

years is the appropriate choice for a

compliance period.

Although 40 CFR part 191 itself does

not directly apply to Yucca Mountain,

the necessity to identify a generic

compliance period is an important

component of the development of

radioactive waste standards, including

the Yucca Mountain standards. In a

regulatory approval process, a judgment

is necessary about the technical

reliability of repository performance

projections. This consensus would

involve the applicant, the regulatory

authority, and the technical community

in general. In the face of increasing

uncertainties in projecting repository

performance over hundreds-ofthousands of years, the potential for

technical consensus on the reliability of

these projections would decrease

sharply. This decrease would lead to a

dramatic increase in the difficulty of

making a compliance decision related to

such an extended time period. In setting

the compliance period in 40 CFR part

191 at 10,000 years, we addressed the

issue of increasing uncertainty by

having a fixed time period rather than

requiring that the time period be

determined individually for any

repository undergoing evaluation.

Third, we are concerned that there

might be large uncertainty in projecting

human exposure due to releases from

the repository over extremely long

periods. We agree with NAS’s

conclusion that it is possible to evaluate

the performance of the Yucca Mountain

disposal system and the surrounding

lithosphere within certain bounds for

relatively long periods. However, we

believe that NAS might not have fully

addressed two aspects of uncertainty.

One of the aspects of uncertainty

relates to the impact of long-term

natural changes in climate and its effect

upon choosing an appropriate RMEI.

For extremely long periods, major

changes in the global climate, for

example, a transition to a glacial

climate, could occur (see Chapter 7 of

the BID). We believe, however, that over

the next 10,000 years, the biosphere in

the Yucca Mountain area probably will

remain, in general, similar to presentday conditions due to the rain-shadow

effect of the Sierra Nevada Mountains,

which lie to the west of Yucca Mountain

(see Chapter 7 of the BID). As discussed

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32099

by NAS, however, for the longer periods

contemplated for the alternative of time

to peak dose, the global climate regime

is virtually certain to pass through

several glacial-interglacial cycles, with

the majority of time spent in the glacial

state (NAS Report p. 91). These longer

periods would require the specification

of exposure scenarios that would not be

based upon current knowledge or

cautious, but reasonable, assumptions,

but rather upon potentially arbitrary

assumptions. The NAS indicated that it

knew of no scientific basis for

identifying such scenarios (NAS Report

p. 96). It is for these reasons that such

extremely long-term calculations are

useful only as indicators, rather than

accurate predictors, of the long-term

performance of the Yucca Mountain

disposal system (IAEA TECDOC–767, p.

19, 1994, Docket No. A–95–12, Item IIA–5).

The other aspect of uncertainty

concerns the range of possible biosphere

conditions and human behavior. As

IAEA noted, beyond 10,000 years it may

be possible to make general predictions

about geological conditions; however,

the range of possible biospheric

conditions and human behavior is too

wide to allow ‘‘reliable modeling’’

(IAEA–TECDOC–767, p. 19, Docket No.

A–95–12, Item II–A–5). It is necessary to

make certain assumptions regarding the

biosphere, even for the 10,000-year

alternative, because 10,000 years

represents a very long compliance

period for current-day assessments to

project performance. For example, it is

twice as long as recorded human history

(see What Do Our Standards Assume

About the Future Biosphere?, section

III.B.1.f, earlier in this document). For

periods approaching the 1,000,000 years

that NAS contemplated under the peakdose alternative, even human

evolutionary changes become possible.

Thus, reliable modeling of human

exposure may be untenable and

regulation to the time of peak dose

within the period of geologic stability

could become arbitrary. Again, the

rational basis necessary for regulatory

decisionmaking would be difficult or

impossible to achieve because of the

speculative assumptions that would be

involved.

Fourth, many international geologic

disposal programs use a 10,000-year

period for assessing repository

performance (see, e.g., Chapter 3 of the

BID, Docket No. A–95–12, Item III–B–2

or GAO/RCED–94–172, 1994, Docket

No. A–95–12, Item V–A–7). These

disposal programs also have examined

this question and have opted to use a

fixed time rather than one based only on

a site-specific compliance period.

Finally, an additional complication

associated with the time to peak dose

within the period of geologic stability is

that it could lead to a period of

regulation that has never been

implemented in a national or

international radiation regulatory

program. Focusing upon a 10,000-year

compliance period forces more

emphasis upon those features over

which humans can exert some control,

such as repository design and

engineered barriers. Those features, the

geologic barriers, and their interactions

define the waste isolation capability of

the disposal system. By focusing upon

an analysis of the features that humans

can influence or dictate at the site, it

may be possible to influence the timing

and magnitude of the peak dose, even

over times longer than 10,000 years.

Based on the extensive public

comment, consistency with other EPA

radioactive and non-radioactive waste

disposal programs, and a consideration

of the numerous uncertainties

associated with projecting repository

performance over extended time

periods, our final rule establishes the

following requirements for the

individual-protection standard and the

human-intrusion analysis. For the

individual-protection standard, a

10,000-year performance assessment is

required for comparison against the 15

mrem standard. In addition, a post10,000-year analysis of peak dose

incurred by the RMEI is to be included

in the EIS for Yucca Mountain, but is

not to be held to a particular dose limit.

We view the post-10,000-year analysis

as an indicator of long-term

performance that provides more

complete information. For the humanintrusion analysis, DOE must determine

the earliest time at which the human

intrusion specified in the standard will

occur. Should the intrusion occur at or

before 10,000 years after disposal, DOE

must demonstrate that the RMEI

receives no more than 15 mrem/yr as a

result of the intrusion (again, analytical

results beyond 10,000 years are not

judged against a dose limit, but must be

included in the EIS). Should the

intrusion occur after 10,000 years, DOE

must include the analysis in the EIS for

Yucca Mountain as an indicator of longterm disposal system performance.

Public comment supported a

compliance period that ranged from

10,000 years to a million years and

beyond (i.e., no time limitation).

Comments supporting the 10,000-year

time period expressed concern that such

a time period was the longest time over

which it is possible to obtain

meaningful modeling results. Some

comments agreed with our position on

the reliability of dose calculations well

in excess of 10,000 years. Other

comments noted that, aside from the

unprecedented nature of compliance

periods exceeding 10,000 years, the

greater uncertainties present at such

times only serve to complicate the

licensing process with no clear cut

greater public health benefit. A few

comments agreed that, because there

likely will be radiation doses to

individuals beyond 10,000 years, DOE

should calculate peak dose, within the

time period of geologic stability, and

include these doses in the Yucca

Mountain EIS.

Numerous comments suggested that

the compliance period should extend to

times beyond 10,000 years. Foremost

among these comments, NAS suggested

a compliance period that would extend

to the time of peak dose or risk, within

the period of geologic stability for Yucca

Mountain (as long as one million years),

based on scientific considerations.

Though NAS based its recommendation

on scientific considerations, it

recognized that such a decision also has

policy aspects (NAS Report, p. 56), and

that we might select an alternative more

consistent with previous Agency policy.

We believe the unprecedented nature of

a compliance period beyond 10,000

years was very persuasive and related

strongly to developing a meaningful

standard that is reasonable to

implement. We also harbored strong

concerns related to uncertainty in

projecting human radiation exposures

over extremely long time periods, for

the reasons mentioned earlier.

Some comments suggested that the

compliance period of the standard

should be comparable to the amount of

time that the materials to be emplaced

in the Yucca Mountain repository will

remain hazardous. While the hazardous

lifetime of radioactive waste is

important, it is but one of a variety of

factors that must be considered in

projecting the potential risks from

disposal. The ability of the disposal

system to isolate such long-lived

materials relates to the retardation

characteristics of the whole

hydrogeological system within and

outside the repository, the effectiveness

of engineered barriers, the

characteristics and lifestyles associated

with the potentially affected population,

and numerous other factors in addition

to the hazardous lifetime of the

materials to be disposed.

Thus, for a variety of technical and

policy reasons, we believe that a 10,000-

year compliance period is meaningful,

protective, and practical to implement.

We also believe that its use will result

in a robust disposal system that will

32100 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

protect public health and the

environment for time periods exceeding

10,000 years. We have included a

10,000-year compliance period in

regulations for non-radioactive

hazardous waste. A 10,000-year

compliance period for Yucca Mountain,

in conjunction with the requirements of

our existing generally applicable

standard at 40 CFR part 191, ensures

that SNF, HLW, and TRU radioactive

wastes disposed anywhere in the United

States have the same compliance period.

Imposing a compliance period beyond

10,000 years would be unprecedented

both nationally and internationally.

Further, such an action would carry

significant and unmanageable

uncertainties. Moreover, provisions to

consider radiation dose impacts beyond

10,000 years as a part of the

environmental impact review process

provide more complete information on

long-term disposal system performance.

We believe this approach provides the

appropriate balance that allows for

meaningful consideration of the issues

related to 10,000-year and post-10,000-

year aspects of disposal system

performance.

2. What Are the Requirements for

Performance Assessments and

Determinations of Compliance?

(§§ 197.20, 197.25, and 197.30)

The NRC must decide whether to

license the Yucca Mountain disposal

system. It must make that decision

based upon whether DOE has

demonstrated compliance with our 40

CFR part 197 standards. We proposed

the quantitative analysis underlying that

decision will be a performance

assessment (as defined in § 197.12). The

DOE and NRC must also make some

decisions about what factors to include

in the performance assessments, and

how extensive those assessments must

be to satisfactorily demonstrate

compliance. We have addressed some of

these performance assessment aspects in

our proposal and final rule.

a. What Limits Are There on Factors

Included in the Performance

Assessments? We proposed that the

performance assessment exclude natural

features, events, and processes based on

the probability of occurrence. We based

our proposed requirements for

performance assessment on a review of

NAS’s recommendations, our

knowledge regarding the extensive

performance assessment work that DOE

and NRC have undertaken regarding the

Yucca Mountain site, and consistency

with 40 CFR part 191 and its application

in the WIPP certification. We also

require NRC to determine, taking into

consideration that performance

assessment, whether the disposal

system’s projected performance

complies with § 197.20. Projecting

repository performance is the major tool

to be used to develop information that

will be used to make compliance

decisions relative to our standards. To

provide the necessary context for these

assessments to generate results for

regulatory decisionmaking, we must

specify sufficient details to assure the

standards are implemented as we intend

through the use of performance

assessments. We have specified only

what we believe to be the minimum

detail necessary. The remainder we

believe should be left to NRC to

determine, consistent with its

implementing responsibilities and

decisionmaking authority.

For repository performance

assessments, our standards also require:

(1) That DOE exclude from

performance assessments those natural

features, events, and processes whose

likelihood of occurrence is so small that

they are very unlikely, which are those

that DOE and NRC estimate to have less

than a 1 in 10,000 (1 × 10¥4) chance of

occurring during the 10,000 years after

disposal. Probabilities below this level

are associated with events such as the

appearance of new volcanoes outside of

known areas of volcanic activity or a

cataclysmic meteor impact in the area of

the repository. We believe there is little

or no benefit to public health or the

environment from trying to regulate the

effects of such very unlikely events;

(2) Unlikely events with probabilities

higher than stated in (1) above may be

excluded from analyses for the human

intrusion and ground water protection

standards. We leave it to NRC to set the

probability limit for these unlikely

events in its implementing regulations;

and

(3) That the performance assessment

need not evaluate the releases from

features, events, processes, and

sequences of events and processes

estimated to have a likelihood of

occurrence greater than 1 x 10¥4 of

occurring during the 10,000 years

following disposal, if there is a

reasonable expectation that the results

of the performance assessment would

not be changed significantly by such

omissions. As necessary, NRC may

provide DOE with specific guidance

regarding scenario selection and

characterization to assure that DOE does

not exclude features, events, or

processes inappropriately.

We received only a few comments on

the question of including low

probability events; however, the

comments we received supported our

proposal. The comments also pointed

out some potential confusion in the

terms we used in describing unlikely

versus very unlikely features, events,

and processes. Our intent is to establish

that there is no need to include, in the

performance assessments used to

demonstrate compliance with the

individual-protection standard, features,

events, and processes, and sequences of

events and processes, with probabilities

of less than 1 x 10¥4 chance of

occurring in the next 10,000 years. We

consider it unlikely that features,

events, and processes with such low

probabilities of occurrence will occur.

We intended to establish another

demarcation for excluding unlikely

features, events, and processes with a

higher probability than stated above but

that still have a low probability of

occurrence. The DOE must include

processes and events in this second

category in the assessments for the

individual-protection standard, unless

NRC determines that excluding them

would not affect the results of the

assessments. The DOE may, however,

exclude them from consideration in

demonstrating compliance with the

human-intrusion and ground water

protection standards. We did not

establish a particular probability level

for these unlikely features, events, and

processes. Instead, we deferred this

decision to the implementing authority

in § 197.36 of our final rule.

The comments we received on this

question supported our contention that

the geologic record is the best source of

evidence for the frequency and

magnitude of natural features, events,

and processes that could affect

repository performance, and that the

geologic record is best preserved in the

relatively recent past. More specifically,

some comments suggested that the

Quaternary Period should be the time

frame over which DOE should examine

evidence for rates and magnitudes of

natural features, events, and processes.

Because the Quaternary Period includes

episodes of glaciation, it provides a

means to estimate the potential effects

of future climate variations. Further, we

believe that the Period’s duration

(approximately two million years)

provides an adequate time frame for

estimating the frequency and severity of

past seismic activity in the repository

area. The NAS in its recommendations

indicated that the repository area could

be assumed to be ‘‘geologically stable’’

over a period of one million years for

the purpose of bounding natural

features, events, and processes. We

believe that the Quaternary Period is a

sufficiently long period of the geologic

record to allow DOE to make reasonable

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32101

estimates of natural features, events, and

processes. We chose not to identify a

specific time frame in the regulatory

language. We leave this choice to the

implementing authority.

We allow the exclusion of unlikely

natural features, events, and processes

from both the ground water and humanintrusion assessments. The approach for

the ground water protection

requirements is consistent with subpart

C of 40 CFR part 191, ‘‘Environmental

Standards for Ground-Water

Protection.’’ The approach for the

human-intrusion analysis is consistent

with NAS’s recommendation (see the

What Is the Standard for Human

Intrusion? section later in this

document). We requested public

comment regarding whether this

approach is appropriate for Yucca

Mountain. See the response to Question

#10 in section IV later in this document

and the Response to Comments

document for more information.

b. What Limits Are There on DOE’s

Elicitation of Expert Opinion? We

requested public comment on whether

we should include requirements on the

use of expert opinion and, if so, what

those requirements should be. We

consider it likely, given the long time

frames involved and the significant

uncertainties in the likelihood of

features, events, processes, and

sequences of events and processes

affecting the Yucca Mountain disposal

system, that DOE will find it useful to

obtain expert opinion to help it arrive at

cautious but reasonable estimates of the

probability of future occurrence of these

features, events, processes, and

sequences of events and processes. We

also expect DOE to find expert opinion

useful in assessing available

performance assessment models, or in

evaluating the uncertainties associated

with the variation of parameter values.

In requesting public comment on this

issue, we distinguished between expert

judgment, which often is obtained

informally, and expert elicitation, in

which a more formal process is used.

We focused on expert elicitation, and

considered including one or all of the

following requirements: (1) NRC must

consider the source and use of the

information so gathered; (2) we would

have expected NRC to assure that, to the

extent possible, experts with both

expertise appropriate for the subject

matter and independence from DOE will

be on the expert elicitation panel

consulted to judge the validity and

adequacy of the model(s) or value(s) for

use in a compliance assessment; and (3)

we would have expected that, when

DOE presents information to the expert

elicitation panel, it should do so in a

public meeting, and qualified experts,

such as representatives of the States of

Nevada and California, should be given

an opportunity to present information.

The comments we received were

uniformly opposed to our setting

requirements to address expert opinion.

There was general agreement among

commenters that it would be more

appropriate for NRC to use the licensing

process to address any requirements

relating to expert elicitation. Some

commenters referred to NRC’s NUREG–

1563 (‘‘Branch Technical Position on

the Use of Expert Elicitation in the

High-Level Radioactive Waste

Program’’), and to the fact that DOE has

used it on several occasions. These

comments reinforced our opinion that

issuing requirements would be an

implementation function better left to

NRC. We do not expect to issue

guidance on this topic, although we

reserve the right to do so. We also

recognize that such guidance would not

be binding, unless it is promulgated by

notice and comment rulemaking.

One comment suggested that we

restrict the form the expert elicitation

could take. The comment stated that it

is inappropriate to estimate parameter

values using Delphi surveys or other

similar techniques that tend to ‘‘exclude

the public from vital areas of debate.’’

Given that we leave the expert

elicitation process to NRC and DOE, we

choose not to address only this one

particular aspect of that process because

we believe that it would be inconsistent

to impose any specific requirements on

how DOE and NRC should use expert

opinion. We believe that NRC and DOE

are sufficiently sensitive to public

opinion regarding the licensing of Yucca

Mountain to avoid the appearance of

secrecy or targeted polling of experts to

obtain a specific outcome. Therefore,

our rule does not address any aspects of

DOE’s ability to use expert elicitation.

c. What Level of Expectation Will

Meet Our Standards? We use the

concept of ‘‘reasonable expectation’’ in

these standards to reflect our intent

regarding the level of ‘‘proof’’ necessary

for NRC to determine whether the

projected performance of the Yucca

Mountain disposal system complies

with the standards (see §§ 197.20,

197.25, and 197.30). We intend for this

term to convey our position that

unequivocal numerical proof of

compliance is neither necessary nor

likely to be obtained for geologic

disposal systems. We believe

unequivocal proof is not possible

because of the extremely long time

periods involved and because disposal

system performance assessments require

extrapolations of conditions and the

actions of processes that govern disposal

system performance over those long

time periods. The NRC has used a

similar qualitative test, ‘‘reasonable

assurance,’’ for many years in its

regulations, and has proposed applying

this concept in its Yucca Mountain

regulations (proposed 10 CFR part 63).

However, the NRC approach was taken

from reactor licensing, which focuses on

engineered systems with relatively short

lifetimes, where performance

projections can be verified and if

necessary corrective actions are

possible. We believe that for very longterm projections where confirmation is

not possible, involving the interaction of

natural systems with engineered

systems complicated by the

uncertainties associated with the long

time periods involved, an approach that

recognizes these difficulties is

appropriate. Although NRC has adapted

the reasonable assurance approach from

the reactor framework and has applied

it successfully in regulatory situations

related to facility decommissioning and

shallow-land waste burial, it has not

been applied in a situation as complex

as the Yucca Mountain disposal system.

We believe that reasonable expectation

provides an appropriate approach to

compliance decisions; however, with

respect to the level of expectation

applicable in the licensing process, NRC

may adopt its proposed alternative

approach. We expect that any

implementation approach NRC adopts

will incorporate the elements of

reasonable expectation listed in

§ 197.14. A more thorough discussion of

our intent concerning the application of

reasonable expectation is given below

and a more exhaustive discussion of the

subject is presented in the Response to

Comments document for this regulation.

We intend that the information in

§ 197.14 of the rule and discussions of

reasonable expectation presented below

and in the Response to Comments

document will provide the necessary

context for implementation of this

concept.

The primary means for demonstrating

compliance with the standards is the

use of computer modeling to project the

performance of the disposal system

under the range of expected conditions.

These modeling calculations involve the

extrapolation of site conditions and the

interactions of important processes over

long time periods, extrapolations that

involve inherent uncertainties in the

necessarily limited amount of

information that can be collected

through field and laboratory studies and

the unavoidable uncertainties involved

in simulating the complex and timeVerDate 11<MAY>2000 14:19 Jun 12, 2001 Jkt 194001 PO 00000 Frm 00029 Fmt 4701 Sfmt 4700 E:\FR\FM\13JNR2.SGM pfrm07 PsN: 13JNR2
32102 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

variable processes and events involved

in long-term disposal system

performance. Simplifications and

assumptions are involved in these

modeling efforts out of necessity

because of the complexity and time

frames involved, and the choices made

will determine the extent to which the

modeling simulations realistically

simulate the disposal system’s

performance. If choices are made that

make the simulations very unrealistic,

the confidence that can be placed on

modeling results is very limited.

Inappropriate simplifications can mask

the effects of processes that will in

reality determine disposal system

performance, if the uncertainties

involved with these simplifications are

not recognized. Overly conservative

assumptions made in developing

performance scenarios can bias the

analyses in the direction of

unrealistically extreme situations,

which in reality may be highly

improbable, and can deflect attention

from questions critical to developing an

adequate understanding of the expected

features, events, and processes. For

example, a typical approach to

addressing areas of uncertainty is to

perform ‘‘bounding analyses’’ of

disposal system performance. If the

uncertainties in site characterization

information and the modeling of

relevant features, events, and processes

are not fully understood, results of

bounding analyses may not be bounding

at all. The reasonable expectation

approach is aimed simply at focusing

attention on understanding the

uncertainties in projecting disposal

system performance so that regulatory

decision making will be done with a full

understanding of the uncertainties

involved.

We received comments both

supporting and opposing the concept of

‘‘reasonable expectation’’ and its

application to the Yucca Mountain

standards. Comments in favor of the

approach agreed that the consideration

of uncertainty is extremely important to

a proper perspective on the degree of

confidence possible for projections of

disposal system performance over the

long time frames involved in assessing

repository performance. Comments

against the concept voiced variations on

three basic concerns: (1) That the

concept is ‘‘new,’’ ‘‘untested,’’ and of

‘‘dubious legal authority’’ in the

regulatory framework; (2) that it implies

that less rigorous, and therefore

unacceptable, science and analysis

would result from the use of reasonable

expectation; and (3) that the choice of

approach to compliance decision

making is solely an implementation

concern that we should leave to NRC.

With respect to the legal authority and

use of the reasonable expectation

concept in the regulatory process, we

believe that the reasonable expectation

concept is well established in both the

regulatory language in standards, as

well as in actual application to deep

geologic disposal of radioactive wastes,

and has been judicially tested. We

developed the ‘‘reasonable expectation’’

approach in the context of developing

40 CFR part 191, the generic standards

for land disposal of SNF, HLW, and

TRU radioactive waste, and more

importantly the concept has been

applied successfully in the EPA

certification of the Waste Isolation Pilot

Plant (WIPP), a deep geologic repository

for TRU radioactive wastes. The WIPP

repository is to date the only deep

geologic repository for radioactive

wastes in the United States that has

been carried through a regulatory

approval process. Therefore, we believe

that the reasonable expectation concept

is neither ‘‘new’’ nor ‘‘untried’’, nor of

‘‘dubious legal authority’’ in the

geologic repository regulatory

experience. In fact, the use of reasonable

expectation for the application to

geologic disposal has been upheld in

court (Natural Resources Defense

Council, Inc. versus U.S. E.P.A. (824

F.2d 1258, 1293 (1st Cir. 1987))).

In contrast, the reasonable assurance

concept was developed and applied

many times in the context of reactor

licensing—not in the context of deep

geologic disposal efforts—and has not

been used in a regulatory review and

approval process for a deep geologic

disposal system. The judicial decision

cited in one comment refers to the use

of reasonable assurance in the context of

reactor licensing, not in the context of

deep geologic disposal. While the

reasonable assurance concept has an

established record of successful

application and judicial approval in

reactor licensing, it is in fact largely

untried in the arena of geologic

disposal.

Some comments suggested our

approach would allow the use of less

rigorous science to the assessment of

disposal system performance in

licensing. This perception may have

arisen from our choice of wording in the

proposal, where we stated that NRC may

elect to use a more ‘‘stringent’’

approach. Such an interpretation was

not our intent: the full text of our

statement is that NRC may impose

requirements that are ‘‘more stringent’’

than the ‘‘minimum requirements for

implementation’’ that our rule

establishes; in addition, we clearly

stated that reasonable expectation ‘‘is

less stringent than the reasonable

assurance concept that NRC uses to

license nuclear power plants’’ (proposed

§ 197.14(b), emphasis added). However,

we will clarify our meaning here.

Performance projections for deep

geologic disposal require the

extrapolation of parameter values (site

characteristics related to performance)

and performance calculations

(projections of radionuclide releases and

transport from the repository) over very

long time frames that make these

projections fundamentally not

confirmable, in contrast to the situation

of reactor licensing where projections of

performance are only made for a period

of decades and confirmation of these

projections is possible through

continuing observation. In this sense, a

reasonable expectation approach to

repository licensing would be

necessarily ‘‘less stringent’’ than an

approach to reactor licensing. We

therefore must disagree with these

comments that reasonable expectation

requires less rigorous proof than NRC’s

reasonable assurance approach.

We do not believe that the reasonable

expectation approach either encourages

or permits the use of less than rigorous

science in developing assessments of

repository performance for use in

regulatory decision making. On the

contrary, the reasonable expectation

approach takes into account the

inherent uncertainties involved in

projecting disposal system performance,

rather than making assumptions which

reflect extreme values instead of the full

range of possible parameter values. It

requires that the uncertainties in site

characteristics over long time frames

and the long-term projections of

expected performance for the repository

are fully understood before regulatory

decisions are made. This approach has

a number of implications relative to the

data and analyses that would be used in

making regulatory decisions. Cautious

use of bounding assessments is implied

since sufficient understanding of

uncertainties must be developed to be

sure such analyses are truly bounding.

Performance scenarios should be

developed realistically without omitting

important components simply because

they may be difficult to quantify with

high accuracy, or always assuming

worst case values in the absence of

information. Elicited values for relevant

data should not be substituted for actual

field and laboratory studies when they

can be reasonably performed, simply to

conserve resources or satisfy scheduling

demands. The gathering of credible

information that would allow a better

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32103

understanding of the uncertainties in

site characterization data and

engineered barrier performance that

would bear on the long-term

performance of the repository should

not be subjugated simply for

convenience. We do not believe that

reasonable expectation in any way

encourages less than rigorous science

and analysis. In contrast, adequately

understanding the inherent

uncertainties in projecting repository

performance over the time frames

required must involve a rigorous

scientific program of site

characterization studies and laboratory

testing.

Some comments expressed the

opinion that our use of the reasonable

expectation approach intrudes

inappropriately into the area of

implementation, which is the province

of NRC. We do not believe that is the

case. We have included the concept of

reasonable expectation in the Yucca

Mountain standards to provide a

necessary context for understanding the

standards and as context for the

implementation of the licensing process

NRC will perform. Projecting disposal

system performance involves the

extrapolation of physical conditions and

the interaction of natural processes with

the wastes for unprecedented time

frames in human experience, i.e., many

thousands of years. In this sense, the

projections of the disposal system’s

long-term performance cannot be

confirmed. Not only is the projected

performance of the disposal system not

subject to confirmation, the natural

conditions in and around the repository

site will vary over time and these

changes are also not subject to

confirmation, making their use in

performance assessments equally

problematical over the long-term (see

Chapter 7 of the BID). In light of these

fundamental limitations on assessing

the disposal system’s long-term

performance, we believe that the

approach used to evaluate disposal

system performance must take into

account the fundamental limitations

involved (including the basic guidance

given in § 197.14), and not hold out the

prospect of a greater degree of ‘‘proof’’

than in reality can be obtained.

Relative to implementation, the

primary task for the regulatory authority

is to examine the performance case put

forward by DOE to determine ‘‘how

much is enough’’ in terms of the

information and analyses presented, i.e.,

implementation involves how

regulatory authority determines when

the performance case has been

demonstrated with an acceptable level

of confidence. We have proposed no

specific measures in our standards for

that judgment. We have not specified

any confidence measures for such

judgments or numerical analyses, nor

prescribed analytical methods that must

be used for performance assessments,

quality assurance measures that must be

applied, statistical measures that define

the number or complexity of analyses

that should be performed, nor have we

proposed any assurance measures in

addition to the numerical limits in the

standards. We have specified only that

the mean of the dose assessments must

meet the exposure limit, without

specifying any statistical measures for

the level of confidence necessary for

compliance. We believe that measure is

a minimal level for compliance

determination, and we selected it to be

consistent with the individual

protection requirement we applied for

the WIPP certification (40 CFR

194.55(f)). For the WIPP certification,

EPA was also the implementing agency,

and in 40 CFR part 194 we also

included implementation requirements,

including statistical confidence

measures for the assessments and

analytical approaches (§§ 194.55(b), (d),

(f)) along with quality assurance

requirements (§ 194.22), other assurance

requirements (§ 194.41), requirements

for modeling techniques and

assumptions (§§ 194.23 and 25), use of

peer review and expert judgment

(§§ 194.26 and 194.27). We have not

incorporated a similar level of detail in

the Yucca Mountain standards because

we believe we must specify only what

is necessary to provide the context for

implementation. We believe that our

reasonable expectation approach

provides a necessary context for

understanding the intent of the

standards and for its implementation.

We have provided guidance statements

in the standards (§ 197.14) relative to

the approach that we believe

appropriately address the inherent

uncertainties in projecting the

performance of the Yucca Mountain

disposal system. The implementing

agency is responsible for developing

and executing the implementation

process and, with respect to the level of

expectation applicable in the licensing

process, is free to adopt an approach it

believes is appropriate, but we believe

whatever approach is implemented

must incorporate the aspects of

reasonable expectation we have

described in the standards and

amplified upon in the Response to

Comments document.

d. Are There Qualitative

Requirements To Help Assure

Protection? In the preamble to our

proposed standards (64 FR 46998), we

requested comment upon whether it is

appropriate for us to establish assurance

requirements in this final rule and if so,

what those requirements should be. The

majority of public comments on the

issue stated that it was unnecessary for

us to include assurance requirements in

this rule. The commenters also generally

stated that the inclusion of such

requirements is an implementation

matter that is properly within NRC’s

jurisdiction. No comments suggested

what, if any, assurance requirements we

should include in this final rule.

Therefore, based upon the public

comments we received regarding this

rule, the provisions in 40 CFR part 191,

and the provisions of NRC’s proposed

10 CFR part 63, we did not include

assurance requirements in this rule,

though we believe we have the authority

to do so pursuant to the AEA and the

EnPA. For example, our generally

applicable standards for the disposal of

SNF, HLW, and TRU radioactive wastes

(40 CFR part 191, 58 FR 66402,

December 20, 1993; 50 FR 38073 and

38078, September 19, 1985) require the

consideration of assurance

requirements. The assurance

requirements in 40 CFR part 191,

however, do not apply to facilities that

NRC regulates, based upon the

understanding between EPA and NRC

that NRC would include them in its

licensing regulations in 10 CFR part 60.

The NRC is the licensing agency for

Yucca Mountain; therefore, at first

glance it appears that requiring

assurance requirements at Yucca

Mountain would be inconsistent with

our approach in 40 CFR part 191. The

EnPA, however, mandates that we set

site-specific standards for Yucca

Mountain. We believe, therefore, that

we could include assurance

requirements in this rule. Because

NRC’s proposed licensing criteria (see

10 CFR 63.102, 63.111, and 63.113; 64

FR 8640, 8674–8677, February 22, 1999)

contain requirements similar to the

assurance requirements in 40 CFR part

191 for multiple barriers, institutional

controls, monitoring, and the

retrievability of waste from Yucca

Mountain, we believe that it is

unnecessary for us to include similar

requirements in this rule. We encourage

NRC to include the assurance

requirements in the proposed 10 CFR

part 63 (64 FR 8640), or requirements

similar to those in 40 CFR part 191, in

its final licensing regulations for Yucca

Mountain.

32104 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

3. What Is the Standard for Human

Intrusion? (§ 197.25)

We adopted NAS’s suggested starting

point for a human-intrusion scenario.

As NAS recommends, our standard

requires a single-borehole intrusion

scenario based upon Yucca Mountainspecific conditions. The intended

purpose of analyzing this scenario

‘‘* * * is to examine the site-and

design-related aspects of repository

performance under an assumed

intrusion scenario to inform a

qualitative judgment’’ (NAS Report p.

111). The assessment would result in a

calculated RMEI dose arriving through

the pathway created by the assumed

borehole (with no other releases

included). Consistent with the NAS

Report, we also require ‘‘that the

conditional risk as a result of the

assumed intrusion scenario should be

no greater than the risk levels that

would be acceptable for the

undisturbed-repository case’’ (NAS

Report p. 113). We interpreted NAS’s

term ‘‘undisturbed’’ to mean that the

Yucca Mountain disposal system is not

disturbed by human intrusion but that

other processes or events that are likely

to occur could disturb the system.

We require that the human-intrusion

analysis of disposal system performance

use the same methods and RMEI

characteristics for the performance

assessment as those required for the

individual-protection standard, with

two exceptions. The first exception is

that the human-intrusion analysis

would exclude unlikely natural features,

events, and processes. The second

exception is that the analysis only

would address the releases occurring

through the borehole (see the What Are

the Requirements for Performance

Assessments and Determinations of

Compliance? section earlier in this

document).

As noted earlier, our rule uses the

same RMEI description for this analysis

and scenario as in the assessment for

compliance with the individualprotection standard. It is possible that

one could postulate that an individual

occupies a location above the repository

footprint in the future and is impacted

by radioactive material brought to the

surface during an intrusion event;

however, the level of exposure of such

an individual would be independent of

whether the repository performs

acceptably when breached by human

intrusion in the manner prescribed in

the scenario. Movement of waste to the

surface as a result of human intrusion is

an acute action. The resulting exposure

is a direct consequence of that action.

Thus, we interpret the NASrecommended test of ‘‘resilience’’ to be

a longer-term test as measured by

exposures caused by releases that occur

gradually through the borehole, not

suddenly as with direct removal. In

addition, the effects of direct removal

depend on the specific parameters

involved with the drilling, not on the

disposal system’s containment

characteristics. We also require that the

test of the disposal system’s resilience

be the dose incurred by the same RMEI

used for the individual-protection

standard. This approach is consistent

with NAS’s recommendation.

The DOE must determine when the

intrusion would occur based upon the

earliest time that current technology and

practices could lead to waste package

penetration without the drillers noticing

the canister penetration. In general, we

believe that the time frame for the

drilling intrusion should be within the

period that a small percentage of the

waste packages have failed but before

significant migration of radionuclides

from the engineered barrier system has

occurred because, based upon our

understanding of drilling practices, this

period would be about the earliest time

that a driller would not recognize an

impact with a waste package. Our

review of information about drilling and

experiences of drillers indicates that

special efforts, such as changing to a

specialized drill bit, would likely be

necessary to penetrate intact, nondegraded waste packages of the type

DOE plans to use. As stated earlier, DOE

would determine the timing as part of

the licensing process. The DOE’s wastepackage performance estimates indicate

that a waste package would be

recognizable to a driller for at least

thousands of years (see Chapter 8 of the

BID).

We requested comment regarding how

much the human-intrusion analysis will

add to protection of public health. Also,

given current drilling practice in the

vicinity of Yucca Mountain, we sought

comment regarding whether our

stylized, human-intrusion scenario is

reasonable.

Comments on our intrusion scenario

focused on a number of concerns. Some

comment expressed opinions that the

intrusion scenario was unrealistic since

actual drilling to tap ground water

would more probably be done not from

the crest of Yucca Mountain but rather

from the adjacent valley floors. Other

comments stated that multiple drilling

intrusions should be assumed rather

than only one, and offered alternative

scenarios for intrusion frequency and

purposes other than tapping ground

water. Some comments acknowledged

that the scenario was an adequate test of

repository resiliency independent of the

question of attempting to predict future

activities, and that the difficulty of

reliably predicting future activities and

human intention were unavoidable, as

NAS concluded. Some comment stated

that the probability of such an intrusion

was so remote as to make the scenario

useless for any type of repository

analysis, while some comment

expressed opinions that the entire

question of human intrusion was an

implementation issue that should be left

to the discretion of NRC. Detailed

responses to comments we received on

the human intrusion question is found

in the Response to Comments document

accompanying this rule. Our response to

some of the most common issues raised

in the comments is given below.

A number of comments criticized the

stylized definition of the scenario on the

grounds it did not address the reality of

the site location and resource potential.

A convincing case can be made that

intrusion is unlikely because of the low

resource potential of the immediate

Yucca Mountain area (see BID, Chapter

8), and that actual drilling to tap the

underlying ground water would most

probably be done in the valleys adjacent

to Yucca Mountain, as some comments

pointed out. We recognize these

conditions and the relatively low

resource potential; however, as NAS

pointed out, there is no scientifically

defensible basis to preclude intrusion

(NAS Report p. 111). For this reason, the

panel recommended that an intrusion

scenario should be assessed separately

from the expected repository

performance case (NAS Report p. 109),

and that a stylized intrusion scenario

consisting of one borehole penetration

should be considered (NAS Report p.

112) as a test of repository resilience to

modest intrusion (p. 113). We agree

with the NAS conclusions in this

regard. As we have pointed out early in

the preamble, releases and consequent

exposures can come from either the

gradual degradation of the disposal

system under expected conditions or

through disruption, most notably by

human activities. Since intrusion cannot

unequivocally be ruled out, and

exposures can result from intrusions

that release radionuclides, we believe it

is necessary to consider human

intrusion in the context of a repository

standard focused on public health

protection, even though the resource

potential at the site is low. The nature

of the intrusion, how it is analyzed and

how it should be evaluated in the

regulatory context, are the next issues to

consider after the basic need to assess a

human intrusion scenario is recognized.

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32105

The NAS was very specific in its

recommendations about assessing

human intrusion. The panel

recommended that the intrusion

scenarios be considered in the EPA’s

rulemaking process (NAS Report p. 109)

and that ‘‘EPA should specify in its

standard a typical intrusion scenario to

be analyzed’’ (p. 108). The panel

recommended that a drill hole

penetration through a waste package be

assumed, which would make a

connection from the repository to the

underlying saturated zone (pp. 12 and

111). The panel recommended that a

‘‘consequences-only analysis’’ be

performed (p. 111) and that the standard

‘‘should require such an analysis’’ (p.

111), i.e., the analysis should only deal

with the fate of releases through the

borehole and the potential doses

resulting. The NAS recommended that

‘‘the conditional risk as a result of the

assumed intrusion scenario should be

no greater than the risk levels * * *

acceptable for the undisturbed

repository case’’ (NAS Report p. 113).

We agree with these NAS

recommendations and therefore we have

constructed the stylized intrusion

scenario as described as separate from

the individual-protection standard, and

imposed a dose limit no greater than the

dose limit imposed for the individualprotection standard. We have also

followed the NAS recommendation for

the time frame for the intrusion (NAS

Report p. 112) by linking it to the

expected time when the containers first

reach a state when a drilling penetration

can occur unnoticed by the drillers.

This time frame serves as a means of

establishing the radionuclide inventory

available for release and the transport

and dose analysis required by the

standard. Comments we received

proposing alternative drilling

frequencies and intentions, such as

deliberately drilling into the repository,

did not provide a sufficient rationale to

abandon the NAS recommendations and

we therefore retained our original

framing for the scenario. Additional

discussion of the intrusion scenario is to

be found in the discussion of comments

we received on Question 10 from the

proposed rule preamble (see section IV

below).

Another line of comment we received

stated that framing the intrusion

scenario in part, or in any way

whatever, should be considered an

implementation detail that should be

left to NRC. As stated earlier in this

document (see section I.A.2, The Role of

40 CFR part 191 in the Development of

40 CFR part 197), human intrusion is a

process that can contribute to exposures

of the public, and it is therefore

appropriate to address it in a public

health protection standard. In addition,

we believe the NAS recommendations

as mentioned above were very explicit

in stating that human intrusion should

be included in the EPA standard and

that framing the intrusion scenario

should be part of the EPA rulemaking,

rather than in implementing regulations.

We have followed the NAS

recommendations closely, as noted in

its comments on our proposed rule. We

are also concerned that the

implementing authority have some

flexibility in implementing the rule and

we have framed the standard to allow

that flexibility. We have specified in the

rule only enough of the details of the

scenario to assure it is implemented as

we intend. We have in fact not specified

enough of the detail to allow an analysis

to actually be performed from our

description alone. For example, we have

not specified the mechanisms by which

radionuclides are released from the

breached container and make their way

down the borehole to the ground water

table. Without specifying release and

transport mechanisms the analysis

cannot be performed. We have left this

essential detail for the implementation

process. We believe this flexibility is

necessary so that the intrusion analyses

can consider a range of conditions for

the stylized intrusion so it can be an

actual test of the repository ‘‘resilience’’

for a limited by-passing of the

engineered barrier system. Although we

have defined the stylized drilling

intrusion scenario to closely follow the

NAS recommendations, if NRC

determines during its implementation

efforts that additional intrusion

scenarios are necessary to make a

licensing decision, NRC can require

additional analyses as part of its

implementing authority.

We offered for comment two

alternatives for the human intrusion

standard. The first alternative simply

stated that DOE must demonstrate a

reasonable expectation that the annual

dose incurred by the RMEI would not

exceed 15 mrem CEDE as a result of an

intrusion event, for 10,000 years after

disposal. This parallels the basic

individual-protection standard.

The second alternative incorporated

our concern that assessments of longerterm performance be made available, if

not explicitly used for compliance

purposes. Under this alternative, we

made a distinction based on how long

after disposal the intrusion could occur.

If the intrusion were to occur at or

earlier than 10,000 years after disposal,

DOE must demonstrate a reasonable

expectation that annual exposures to the

RMEI as a result of the intrusion event

would not exceed 15 mrem CEDE. There

would be no time limit for this analysis;

as our proposal stated, ‘‘[i]f that

intrusion can happen within 10,000

years, then DOE must do an analysis

which projects the peak dose that would

occur as a result of the intrusion within

10,000 years.’’ (64 FR 46999, August 27,

1999) However, if the intrusion

occurred after 10,000 years, DOE would

not have to compare its results against

a numerical standard, but would have to

include those results in its EIS.

We have selected the second

alternative for our final human intrusion

standard (§ 197.25). However, we are

not requiring that DOE calculate a peak

dose beyond 10,000 years for

comparison against a numerical

standard. If the intrusion event occurs

earlier than 10,000 years after disposal,

DOE need only compare the dose within

10,000 years to the numerical standard.

DOE must include post-10,000-year

results in its EIS, no matter when the

intrusion occurs. We believe this

alternative provides assurance that the

full effects of an intrusion event will be

assessed, regardless of when it occurs.

We also believe that the selected

alternative is more consistent with the

NAS recommendations that a

‘‘consequence-based’’ analysis be

performed (NAS Report p. 111).

The time frame for the intrusion has

implications on how the projected doses

are handled and evaluated. We are

distinguishing between intrusion events

that occur within 10,000 years and those

that occur later than 10,000 years after

disposal. In assessing events that occur

within 10,000 years, we further

distinguish the results based on whether

exposures are incurred by the RMEI

within the 10,000-year period. We have

established the 10,000-year compliance

period to reflect past precedents and a

realization of the inherent uncertainties

in long-term performance projections

(see section III.(B)(1)(g)). For intrusion

events that occur within 10,000 years

and exposures are incurred by the RMEI

within 10,000 years, doses are compared

against the 15 mrem/yr limit given in

the standard as part of the compliance

case for licensing. For consistency in the

treatment of post-10,000-year dose

assessments, we are specifying that,

when the dose to the RMEI from human

intrusion events occurs after the 10,000

year period, the dose assessments are to

be included in the EIS, along with the

post-10,000 year performance

assessments for the individual

protection standard. Regardless of when

the intrusion occurs, if exposures are

incurred later than 10,000 years, they

32106 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

are to be included in the EIS up to the

time of peak dose.

We formulated the selected

alternative to be responsive to the NAS

recommendations, in addition to

addressing our concern regarding the

availability of post-10,000 year analyses.

A key factor in evaluating an intrusion

scenario is predicting when such an

event might take place. However, as

NAS concluded, ‘‘there is no scientific

basis for estimating the probability of

intrusion at far-future times’ but that

‘‘we believe it is useful to assume that

the intrusion occurs during a period

when some of the canisters will have

failed * * *’’ NAS Report p. 107, 112.

Therefore, we specify that DOE must

assume the intrusion occurs at ‘‘the

earliest time after disposal that the

waste package would degrade

sufficiently that a human intrusion

could occur without recognition by the

drillers’ (proposed § 197.25). This time

would be determined through the

licensing process, presumably by

assessing the expected performance of

the engineered barrier system. This

provides DOE the flexibility to

demonstrate that its engineered barrier

system is sufficiently robust to

withstand intrusion for a predictable

time period, which then determines the

nature of the waste inventory used in

the analysis, i.e., the relative

proportions of long-and short-lived

radionuclides.

4. How Does Our Rule Protect Ground

Water? (§ 197.30)

The inclusion of separate ground

water protection standards in today’s

rule continues a longstanding Agency

policy of protecting ground water

resources and the populations who may

use such resources. This policy is

articulated in our primary ground water

protection strategy document titled

‘‘Protecting the Nation’s Ground Water:

EPA’s Strategy for the 1990’s’’ (Docket

No. A–95–12, Item V-A–13). We

designed today’s standards to protect

the ground water in the vicinity of

Yucca Mountain to benefit the current

and future residents of the area who

could use this ground water as a

resource for drinking water and other

domestic, agricultural, and commercial

purposes. The following sections

discuss the Agency’s general approach

to ground water protection, the NAS

comments regarding ground water

protection at Yucca Mountain, and some

of the legal and regulatory issues

associated with our final ground water

protection standards.

Policy and Technical Rationales for

Separate Ground Water Protection

Standards

Our General Approach to Ground Water

Protection

Ground water is one of our nation’s

most precious resources because of its

many potential uses. A significant

portion (over 50 percent in the early

1990s) of the U.S. population draws on

ground water for its potable water

supply (‘‘Protecting the Nation’s Ground

Water: EPA’s Strategy for the 1990’s,’’

Docket No. A–95–12, Item II–A–3). In

addition to serving as a source of

drinking water, people use ground water

for irrigation, stock watering, food

preparation, showering, and various

industrial processes. When that water is

radioactively contaminated, each of

these uses completes a radiation

exposure pathway for people. Ground

water contamination is also of concern

to us because of potential adverse

impacts upon ecosystems, particularly

sensitive or endangered ecosystems

(‘‘Protecting the Nation’s Ground Water:

EPA’s Strategy for the 1990’s,’’ Docket

No. A–95–12, Item II–A–3). For these

reasons, we believe it is a resource that

needs protection. Therefore, we require

protection of ground water that is a

current or potential source of drinking

water to the same level as the maximum

contaminant levels (MCLs) for

radionuclides that we established

previously under the authority of the

Safe Drinking Water Act (SDWA).

In January 1990, the Agency

completed a strategy to guide future

EPA and state activities in ground water

protection and cleanup. The Agencywide Ground Water Task Force

developed two papers, which it issued

for public review: an EPA Statement of

Ground Water Principles and an options

paper covering the issues involved in

defining the Federal/State relationship

in ground water protection. We

combined these papers and other Task

Force documents into an EPA Ground

Water Task Force Report: ‘‘Protecting

The Nation’s Ground Water: EPA’s

Strategy for the 1990’s’’ (‘‘the Strategy,’’

EPA 21Z–1020, July 1991 (Docket No.

A–95–12, Item II–A–3)). Our approach

in this rule is consistent with this

strategy.

Key elements of our ground water

protection and cleanup strategy are the

strategy’s overall goals of preventing

adverse effects on human health and the

environment and protecting the

environmental integrity of the nation’s

ground water resources. Our strategy

also recognizes, however, that our

efforts to protect ground water must

consider the use, value, and

vulnerability of the resource, as well as

social and economic values. We believe

it is important to protect ground water

to ensure the preservation of the

nation’s currently used and potential

underground sources of drinking water

(USDWs) for present and future

generations. Also, we believe it is

important to protect ground water to

ensure that where it interacts with

surface water it does not interfere with

the attainment of surface-water-quality

standards; these standards are also

necessary to protect human health and

the integrity of ecosystems. We employ

MCLs to protect ground water in

numerous regulatory programs. Our

regulations pertaining to hazardouswaste disposal (40 CFR part 264);

municipal-waste disposal (40 CFR parts

257 and 258); underground injection

control (UIC) (40 CFR parts 144, 146,

and 148); generic SNF, HLW, and TRU

radioactive waste disposal (40 CFR part

191); and uranium mill tailings disposal

(40 CFR part 192) reflect this approach.

These programs have demonstrated that

such protection is scientifically and

technically achievable, within the

constraints that each program applies

(‘‘Progress In Ground Water Protection

and Restoration,’’ EPA 440/6–90–001,

Docket No. A–95–12, Item V–A–6).

Another critical issue in ground water

protection is that ground water

generally is not directly accessible.

Thus, it is much more difficult to

monitor and/or decontaminate ground

water than is the case with other

environmental media (‘‘Ground-Water

Protection Strategy’’ p. 11, August 1984,

Docket No. A–95–12, Item V–A–13).

Because of the expenses and difficulties

associated with remediation of

contaminated ground water, it is

prudent and cost-effective to prevent the

occurrence of such contamination (Id.).

It is possible for large amounts of

contaminants to enter a body of ground

water and remain undetected until the

contaminated water reaches a water

well or surface-water body. Moreover,

ground water contaminants, unlike

contaminants in other environmental

media such as air or surface water,

generally move in plumes with limited

mixing or dispersion into

uncontaminated water surrounding the

plume. These plumes of relatively

concentrated contaminants can move

slowly through aquifers. They may

persist, and thus may make the

contaminated resource unusable, for

extended periods of time (Id.). Because

an individual plume may underlie only

a very small part of the land surface, it

can be difficult to detect by aquifer-wide

or regional monitoring. Also, monitoring

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32107

is unlikely to occur over greatly

extended time periods, during which

time an aquifer may become

dangerously contaminated (Id.). Further,

the affected area may become quite large

over long time periods. Thus, we believe

that it is prudent and responsible to

protect ground water resources from

contamination through pollution

prevention rather than to rely on cleanup of preventable pollution. The

pollution prevention approach to

protecting ground water resources we

are adopting for Yucca Mountain avoids

requiring present or future communities

to implement expensive clean-up or

treatment procedures. This approach

also protects individual ground water

users. Moreover, absent the protection

we have built into the rule, the ground

water in aquifers around the repository

itself could be subject to expensive

clean-up by future generations if

releases from the repository contaminate

the surrounding ground water to levels

that exceed legal limits. A guiding

philosophy in radioactive waste

management, as well as waste disposal

in general, has been to avoid imposing

burdens on future generations for cleanup efforts as a result of disposal

approaches that would knowingly result

in pollution in the future (see, for

example, IAEA Safety Series No. 111–F,

‘‘The Principles of Radioactive Waste

Management,’’ Docket No. A–95–12,

Item V–A–10). With respect to

radioactive waste disposal, we believe

the fundamental principle of intergenerational equity is important. We

should not knowingly impose burdens

on future generations that we ourselves

are not willing to assume. Disposal

technologies and regulatory

requirements are developed with the

aim of preventing pollution from

disposal operations, rather than

assuming that clean-up in the future is

an unavoidable cost of disposal

operations today. Designing a disposal

system, and imposing performance

requirements that avoid polluting

resources that reasonably could be used

in the future, therefore, is a more

appropriate choice than imposing cleanup burdens on future generations. The

approach to ground water protection in

today’s standards is consistent with our

overall approach to ground water

protection: it prevents the

contamination of current and potential

sources of drinking water downgradient

from Yucca Mountain.

NAS Comments on Ground Water

Protection

In its report, NAS clearly identified

the ground water pathway as the

significant pathways of to the biosphere

in the vicinity of Yucca Mountain(NAS

Report pp. 52 and 81). The NAS also

recognized that ground water modeling

for the Yucca Mountain site is complex.

Because the modeling for Yucca

Mountain involves water movement

through pore spaces (the matrix) and

fractures in the rocks, as well as the

degree of interconnectedness between

the water moving in the two pathways,

there is uncertainty regarding which

model or models to use in the analysis:

Because of the fractured nature of the tuff

aquifer below Yucca Mountain, some

uncertainty exists regarding the appropriate

mathematical and numerical models required

to simulate advective transport * * * [E]ven

with residual uncertainties, it should be

possible to generate quantitative (possibly

bounding) estimates of radionuclide travel

times and spatial distributions and

concentrations of plumes accessible to a

potential critical group. (NAS Report p. 90)

In its report, NAS did not recommend

specifically that we include a separate

ground water protection provision in

our environmental protection standards

for Yucca Mountain. Neither, however,

did NAS state that we should not

include such a provision.

However, in its comments on the

proposed rule, NAS specifically

addressed our decision to include

separate ground water protection

standards for the Yucca Mountain site:

‘‘(i)n the preamble (to the proposed rule),

EPA implies that there is a scientific basis for

inclusion of separate ground-water limits in

the standards ‘‘ for example, EPA provides a

detailed analysis of approaches to calculating

such limits * * * The (NAS) respectfully

disagrees and does not believe that there is

a basis in science for establishing such limits

for the reasons described above. The (NAS)

recognizes EPA has the authority under the

Energy Policy Act to establish separate

ground-water limits as a matter of policy, but

if it does so it should explicitly state the

policy decisions embedded in the proposed

standard and ask the public to comment on

those decisions.

‘‘If EPA wishes to establish such standards

on the basis of science, it must make more

cogent scientific arguments to justify the

need for this standard’’

(NAS Comments, p. 11, Docket No. A–95–

12, Item IV–D–31).

EPA’s Review of the Ground Water

Standards

For the reasons discussed above (see

Our General Approach to Ground Water

Protection), we believe that separate

ground water protection standards

designed to protect the ground water

resource are necessary elements of our

Yucca Mountain standards. Our

decision to include separate ground

water standards is a policy decision that

we make pursuant to our statutory

authority under the Energy Policy Act.

Regarding the protectiveness of the

standards, 40 CFR part 197 incorporates

the current MCLs. We believe that this

approach is necessary to provide

stability for NRC and DOE in the

licensing process. We based these MCLs

on the best scientific knowledge

regarding the relationship between

radiation exposure and risk that existed

in 1975 when they were developed.

Scientific understanding has evolved

since 1975. We recently concluded a

review of the existing MCLs based on a

number of factors, including the current

understanding of the risk of developing

a fatal cancer from exposure to

radiation; pertinent risk management

factors (such as information about

treatment technologies and analytical

methods); and applicable statutory

requirements. See 65 FR 76708–76753,

December 7, 2000. Our analyses indicate

that, when the risks associated with the

individual radionuclide concentrations

derived from the MCLs are calculated in

accordance with the latest dosimetry

models described in Federal Guidance

Report 13, they still generally fall within

the Agency’s current risk target range for

drinking water contaminants of 10¥4 to

10¥6 lifetime risk for fatal cancer.

Therefore, the MCLs for the

radionuclides of concern at Yucca

Mountain have not changed.

Our analyses, and those of NAS,

indicate that, of all the potential

environmental pathways for

radionuclides, travel through ground

water is the most likely pathway to lead

to human exposure to radiation from the

Yucca Mountain disposal system (see

Chapters 7 and 8 of the BID). The

ground water protection standards in

this rule protect ground water that is

being used or that might be used as

drinking water by restricting potential

future contamination. Water from the

aquifer beneath Yucca Mountain

currently serves as a source of drinking

water 20 to 30 km south of Yucca

Mountain in the communities directly

protected by the individual-protection

standard. It is also a potential source of

drinking water for more distant

communities. As noted by NAS, the

available ground water supply in the

vicinity of Yucca Mountain could

sustain a substantially larger population

than that presently in the area (NAS

Report p. 92).

Technical Approach for Protecting

Ground Water at Yucca Mountain

As noted above, NAS asserted in its

comments regarding the proposed rule,

that we implied that there was a

scientific basis for including separate

ground water limits in the regulations.

The NAS urged us to clearly state the

32108 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

policy reasons for including such limits.

We believe that we clearly articulated in

the preamble to the proposed rule that

we included a ground water protection

provision in the proposal based upon

our long-standing policy.

In keeping with the site-specific

nature of these standards, we believe

that it is appropriate to outline an

approach to determining compliance

with the ground water standards

consistent with the geologic conditions

along the anticipated ground water flow

path for releases from the repository.

The approach that we have devised

consists of several components. The first

component is to define a ground water

resource use common for the current

population making use of the ground

water along the potential path of

releases. The population living

downgradient from the repository

typically uses the ground water for

domestic consumption and for

agricultural activities. The dominant

agricultural activity is alfalfa cultivation

(see Chapter 8 of the BID). The next

component of the approach is to define

a method for assessing the extent of

potential contamination in the aquifer

that can be used for comparison against

established limits. To address the

unique setting of the repository, we are

defining a ‘‘representative volume’’ of

ground water consistent with the uses of

the resource (see § 197.31(b)). The third

component is to propose alternatives to

defining how DOE could use the

representative volume in making

assessments of potential ground water

contamination (see § 197.31). See the

Representative Volume of Ground Water

discussion later in this section for our

responses to comments on the

representative volume approach.

We proposed to use the MCLs as

appropriate standards against which to

measure compliance. Comment upon

our proposal was mixed. Some

comments claimed that we misapplied

the MCL concept in the Yucca Mountain

standards compared with how we apply

MCLs in other situations, such as the

use of MCLs to define when drinking

water from public water supplies is

acceptable. Some comments supported

the use of MCLs. Other comments

pointed out that the dosimetry system

used for the current MCLs has been

superceded by newer approaches to

assessing dose and risk from ground

water use and that we should, therefore,

not use the MCLs. A number of

comments claimed that the use of

separate ground water standards is

completely unnecessary because the

individual-protection standard includes

the drinking water exposure pathway

and, therefore, the ground water

standards are unnecessary as a health

protection measure.

Retaining separate ground water

protection standards is consistent with

both our national policy to protect

ground water resources and with

previous Agency regulations for

geologic disposal facilities. Our generic

standards in 40 CFR part 191, which

apply to the same kinds of wastes

contemplated for disposal at Yucca

Mountain, contain separate ground

water protection provisions. We believe

that there is no question that separate

ground water protection standards are

appropriate for deep geologic disposal

facilities. We believe that the use of

contaminated ground water for purposes

that could result in exposures to

individuals should be of concern, and

that avoiding contaminating useable

ground water resources is in the general

interest of the public at large. More

specifically, contamination of water

resources could result in the exposure of

individuals well removed from the

repository location. Also, if ground

water were withdrawn from the

repository sub-basin, and transported to

other locations to supply water needs, a

larger population would be exposed

than if the water were used only locally.

We commonly apply MCLs to water

treatment facilities to assure that

exposures to the subsequent users of the

water are acceptable and the users are

protected. The intent of using the MCLs

as a compliance measure for the Yucca

Mountain disposal system is to

encourage a robust containment and

isolation design that will not result in

unacceptable contamination during the

regulatory time frame, which would

require future generations to shoulder

the burden of water treatment due to

contamination from the wastes. We also

included ground water protection

requirements in our certification process

for WIPP, which is the only deep

geologic disposal facility in the country

that has actually gone through a

regulatory review and approval process.

We see no reason why we should not

apply the same approach to protection

for the Yucca Mountain disposal facility

as we afforded to the population around

WIPP. In fact, the Yucca Mountain

disposal system will be located above

aquifers that are the ground water

supply for the residents living

downgradient from the repository,

whereas the aquifers potentially subject

to contamination at the WIPP facility are

highly saline, non-potable water

sources. We recognize that the

individual-protection standard includes

a drinking water exposure pathway;

however, from a policy perspective it is

appropriate and consistent for us to

provide separate protection for ground

water resources in the Yucca Mountain

area. As illustrated by the examples

above, the protection of ground water

resources is in the general interest of the

public at large, because it is easily

conceivable that uses of the resource

could result in exposures well beyond

the immediate vicinity of the repository.

From a more practical perspective, it

would be extremely difficult to predict

with any reliability what the total range

of potential exposures (and consequent

health effects) would be for all possible

uses of the resource, because such

predictions would involve considerable

speculation. It makes more sense to

assure the resource is not contaminated

in the first place. We are taking the more

prudent course of attempting to prevent

ground water contamination above the

MCLs by imposing separate ground

water protection requirements.

The NRC’s determination of

compliance with the ground-water

protection standards will be based

largely upon DOE’s projections of

potential future contaminant

concentrations. The DOE will include

these projections in the license

application it submits to NRC. These

projections, by their very nature,

inevitably will contain uncertainty. An

important cause of uncertainty, as NAS

recognized, is the choice of conceptual

site models (NAS Report p. 75). The

conceptual models used for Yucca

Mountain can differ fundamentally. For

example, water can be presumed to flow

through either pores in the rock or

conduits through the rock (such as

discrete fractures or a network of

fractures that can act as preferential

pathways for faster ground water flow),

or a combination of the two. To further

complicate the situation, any of these

flow scenarios, with the possible

exception of flow through conduits, can

occur at Yucca Mountain whether or not

the rock is saturated completely with

water.

We believe that adequate data and the

choice of models will be critical to any

compliance calculation or

determination because such data and

models are the backbone of the

performance assessment used to show

compliance. The NAS examined the use

of ground-water flow and contaminanttransport models in regulatory

applications (‘‘Ground Water Models:

Scientific and Regulatory Applications,’’

1990, Docket No. A–95–12, Item V-A–

26). In that report, NAS concluded that

data inadequacy is an impediment to

the use of unsaturated fracture flow

models for Yucca Mountain. However,

NAS noted that data inadequacy also

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32109

was an impediment to using models that

assume the pores in the rock are either

saturated or unsaturated or that assume

flow through fractures that are filled

completely with water. However,

despite the recognition of the

importance of the choice of the site

conceptual model, we believe that the

need for sufficient quantity, types, and

quality of data to adequately analyze the

site, because of its hydrogeologic

complexity, is even more important. In

other words, the complexity of the

ground water flow system requires

adequate site characterization to justify

the choice of the conceptual flow

model.

The choice of modeling approaches to

address the ground water system in the

area of Yucca Mountain, based upon the

conceptual model of the site developed

from site characterization activities, is

important to characterize contaminant

migration, particularly the mixing of

uncontaminated water with water that

has been contaminated with

radionuclides released from breached

waste packages. The extent of the

dilution afforded by mixing

contaminated water with other ground

water moving through the rocks below

the repository but above the water table

and the dispersion of the plume of

contamination within the saturated zone

as the ground water system carries

radionuclides downgradient are critical

elements of the dose assessments.

At one end of the spectrum of

approaches to modeling the Yucca

Mountain area’s ground water system is

the assumption that it is possible to

model the system based upon flow

through pores over a large area (tens of

square kilometers). At the other extreme

is the assumption that radionuclides are

carried through fast-flow fractures in the

unsaturated zone separately from

uncontaminated ground water also

passing through the repository footprint.

Those radionuclides then are assumed

to be carried through the saturated zone

in fractures that allow little or no

dispersion within, or mixing with,

uncontaminated water in the saturated

zone. This scenario is essentially ‘‘pipe

flow’’ from the repository to the

receptor. Although the flow of ground

water at the site is influenced strongly

by fractures, which the models should

reflect, we believe that it is

unreasonable to assume that no mixing

with uncontaminated ground water

would occur along the radionuclide

travel paths because such mixing is a

natural process, and would be governed

by the degree of interconnection

between individual fractures in the

rocks. We requested comment upon this

approach, including consideration of

the practical limitations on

characterizing the flow system over

several or tens of square kilometers.

Comments varied from statements

that we should not allow DOE to

consider mixing of contaminated water

from the repository with

uncontaminated water along potential

flow paths, that such dilution is an

expected process in the natural system,

and that these decisions about the flow

system modeling are implementation

details which we should defer to NRC.

We agree that some degree of mixing

along the ground water flow paths is to

be expected and, if supported by the

hydrogeologic characterization, should

be considered in modeling approaches

used to make projections of

radionuclide migration from repository

releases. We also agree that detailed

decisions about the approach to

modeling the ground water flow system

at the site are an implementation

concern for NRC. We therefore make no

specific requirements in this regard. We

do believe that whatever specific

modeling approach and attendant

assumptions that DOE or NRC make

should attempt to model realistically the

expected behavior of the actual flow

regime downgradient from the

repository. Recalling the ‘‘pipe-flow’’

scenario described above, we believe it

would be highly unrealistic to assume

that no mixing of the contaminated

water with ground water along the flow

path occurs along the distance from the

repository to the furthest allowable

boundary of the controlled area.

Although the actual dispersion effects

for the fractured rock geohydrologic

setting are anticipated to be small (see

Chapter 7 of the BID), ignoring such

processes is still inappropriately overconservative because it would neglect a

natural process that is expected to

occur. Consistent with this perspective,

we specify two alternative methods that

DOE could use for determining

radionuclide concentrations in the

representative volume of ground water.

We believe these two alternatives

provide appropriate direction for

making the compliance determination

while allowing ample flexibility for the

implementation decisions concerning

the details of characterizing the ground

water flow and modeling approaches

that DOE ultimately must select and

defend in the licensing process.

Our intent was to develop ground

water protection standards that NRC can

reasonably implement. In this regard,

NAS indicated that quantitative

estimates of ground water

contamination should be possible (NAS

Report p. 90). We thus require DOE to

project the level of radioactive

contamination it expects to be in the

representative volume of ground water.

The representative volume could be

calculated to be in a contaminated

aquifer that contains less than 10,000

mg/L of TDS and that is downgradient

from Yucca Mountain. Through the use

of this method, we intend to avoid

requiring DOE and NRC to project the

contamination in every small, possibly

unrepresentative amount of water

because we believe that this approach is

not scientifically defensible considering

the inherent uncertainties in hydrologic

data and the limitations of modeling

calculations. For example, we do not

intend that NRC must consider whether

a few gallons of water in a single

fracture would exceed the standards.

Thus, we allow use of a larger volume

of water that must, on average, meet the

standards. See below for a discussion of

this larger volume, the ‘‘representative

volume.’’

Because the purpose of the engineered

and natural barriers of the geologic

repository at Yucca Mountain is to

contain radionuclides and minimize

their movement into the general

environment, we anticipate that

radionuclide releases from the

repository will not occur for a long

period of time. With this assumption in

mind, we believe that ground water

protection for the Yucca Mountain site

should focus upon the protection of the

ground water as a resource for future

human use. It is the general premise of

this rule that the individual-protection

standard will adequately protect those

few current residents closest to the

repository. The intent of the ground

water standards is protecting the aquifer

as both a resource for current users, and

a potential resource for larger numbers

of future users either near the repository

or farther away in communities

comprised of a substantially larger

number of people than presently exist in

the vicinity of Yucca Mountain. To

implement this conceptual approach

and develop an approach for

compliance determinations, we believe

that the ground water standards

currently used, the MCLs, should apply

to public water supplies downgradient

from the repository in aquifers at risk of

contamination from repository releases.

There is presently no public water

supply providing treatment to meet

MCLs before the water reaches

consumers downgradient of Yucca

Mountain, and there is no guarantee that

such a system will be in place to protect

future users from contamination caused

by releases from the disposal system.

Applying the MCLs in the ground water

assures that the level of protection

32110 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

currently required for public water

supplies elsewhere in the nation also is

maintained for future communities

using the water supply downgradient

from the Yucca Mountain disposal

system.

Representative Volume of Ground Water

To implement the standards in

§ 197.30, we require that DOE use the

concept of a ‘‘representative volume’’ of

ground water. Under this approach,

DOE and NRC will project the

concentration of radionuclides released

from the Yucca Mountain disposal

system, for comparison against the

MCLs, that would be present in the

representative volume in the accessible

environment over the 10,000-year

period of the standards. The

representative volume will be a volume

of water projected to supply the annual

water demands for defined resource

uses. We believe that water demand

estimates for calculation of the

representative volume should reflect the

current resource demands for the

general lifestyles and demographics of

the area, but not be rigidly constrained

by current activities, because potential

contamination would occur far into the

future. In the area south of Yucca

Mountain, people currently use ground

water for domestic purposes,

commercial agriculture (for example,

dairy cattle, feed crops, other crops, and

fish farming), residential gardening,

commercial, and municipal uses (see

Chapter 8 of the BID). The ground water

resources, as reflected by estimates of

current usage and aquifer yields,

indicate that there is theoretically

enough water to support a substantially

larger population than presently exists

at each of the four alternative locations

we proposed for the point of compliance

(Id.). The representative volume

approach sets an upper bound on the

size of the hypothetical community and

its water demand. On the other hand,

the SDWA defines the minimum size for

a public water system as a system with

15 service connections or that regularly

supplies at least 25 people. The SDWA

was designed to address, and typically

is applied to, situations where

contamination can be monitored in the

present and where monitoring is done

close to the disposal facility rather than

many kilometers away. If necessary,

corrective actions can be taken if

contamination limits are exceeded. In

contrast, the geologic disposal

application involves potential

contamination releases that are expected

to occur no sooner than far into the

future. It simply is not reasonable to

assume that monitoring for the purpose

of detecting radionuclide contamination

around the repository will be performed

continually far into the future.

Consequently, it is not prudent to

assume that corrective actions would be

taken to reduce contamination levels.

As noted by NAS, active institutional

controls (including active monitoring

and maintenance) can play an important

role in assuring acceptable repository

performance for some initial period, not

exceeding a time scale of centuries

(NAS Report p. 106). Another approach

to protecting the ground water resource

into the future is necessary. Projecting

repository performance, and

consequently assessing potential

repository releases to the surrounding

ground waters, can only be based upon

mathematical modeling of the

repository’s engineered and natural

barrier performance. A method of

assessing potential contamination must

be developed that involves ground

water modeling capabilities. The

approach we have developed to assess

ground water contamination (described

previously) is the use of a representative

volume of ground water in modeling

calculations.

We believe that, ideally, the

representative volume should be fully

consistent with the protection objectives

of the ground water protection strategy;

however, we also recognize the unusual

features of these standards. That is, the

10,000-year compliance period

introduces unresolvable uncertainties

that make this situation fundamentally

different from the situations of clean-up

or foreseeable, near-term potential

contamination to which the SDWA

ground water protection strategy

ordinarily applies. The size of the area

that must be modeled (tens of km2)

around the site and the complexity of

the site characteristics introduce

fundamental limitations on the size of

the water volume that it is possible to

model with reasonable confidence. It is

Agency policy to protect ground water

as a resource and we intend our ground

water protection standards to

accomplish that policy goal. We intend

the representative volume concept we

have incorporated into the standards to

serve as context for the application of

our ground water protection policy to

the Yucca Mountain site, which differs

from the more common application of

the SDWA as described above. The

representative volume concept

addresses two needs in this respect.

First, the size of the representative

volume (measured as an annual volume

in acre-feet) must be sufficiently large

that the uncertainties in projecting site

characteristics (such as the hydrologic

properties along the flow paths) that

control ground water flow are not so

great that performing calculations to

determine radionuclide concentrations

in that volume becomes meaningless

from an analytical perspective. That is,

we should not expect a higher level of

confidence and exactness than the

scientific tools and available data are

capable of providing. Second, the

representative volume should be an

appropriate measure of the resource to

be protected. From both perspectives,

analytical limitations and resource

characterization, the representative

volume of 1,285 acre-feet that we

proposed is the potential choice that

could satisfy those needs. As described

in the preamble to the proposed rule, we

preferred the 1,285 acre-feet alternative

because we believed it reflected both

perspectives. The major resource use for

ground water in the area downgradient

from the repository is agriculture, and

the most water intensive agricultural

activity in the area is alfalfa farming.

The 1,285 acre-feet representative

volume (including 10 acre-feet for

domestic use for the farm community) is

the water demand for an average alfalfa

farm in the Amargosa Valley area (see

Chapter 8 of the BID). From

consideration of the inherent limitations

of modeling the geohydrologic setting at

the site, we believe that approximately

a 100 acre-feet representative volume is

the smallest volume for which it is

possible to perform reasonably reliable

calculations (Memo to Docket from

Frank Marcinowski, EPA, Docket No.

A–95–12, Item II–E–10). The 1,285 acrefeet volume is sufficiently above this

limit; therefore, questions about the

scientific capabilities of performance

modeling to assess radionuclide

concentrations in the 1,285 acre-feet

volume should not be a concern. While

still feasible to model, 120 acre-feet is

much closer to the lower limit of

defensible modeling, and uncertainties

at this volume are potentially unwieldy

and overwhelming. We requested

comment regarding both our use of a

representative volume of ground water

and possible alternatives for the size of

the representative volume. We based

these alternative volumes upon

variations in possible lifestyles for

residents downgradient from the

repository and upon current and nearterm projections of population growth

and land use in the area.

We specifically requested comment

upon whether 1,285 acre-feet is the most

appropriate representative volume of

ground water, or whether other values

within the ranges discussed below are

more appropriate. We believe that there

may be significant technical, policy, or

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32111

practical obstacles with the use of either

very small or very large water volumes.

Modeling capabilities limit the volumes

of ground water for which it is possible

to make meaningful and scientifically

defensible calculations. At the other

extreme, excessively large volumes of

water allow artificially high dilution of

radionuclide releases, and do not

actually simulate the natural process

that would occur along the radionuclide

ground water travel path from the

repository to the compliance point. The

selection of the representative volume

must consider both modeling

limitations and realistic approaches to

modeling, and must be both a

reasonable representation of the

resource to be protected and be possible

to implement from a modeling

perspective.

Comments on our alternatives for the

representative volume size varied from

agreement with our preferred volume of

1,285 acre-ft to favoring larger and

smaller volumes. We believe that the

larger volume mentioned in the

proposed rule, 4,000 acre-ft, is not a

suitable choice for a number of reasons.

This number is an estimate of the

perennial yield in the sub-basin

containing Yucca Mountain. It is an

estimate of the amount of ground water

that can be removed annually without

seriously depleting the aquifer. Because

there are relatively few wells in this

sub-basin, the 4,000 acre-ft estimate is

not highly reliable and is difficult to

justify. This is one reason why we did

not select this number. Perhaps more

importantly, the perennial yield is not a

physical location in the aquifer and the

challenge of projecting repository

performance is to project the path of

potential contamination from the

repository. The perennial yield concept

is not consistent with the idea that the

modeling of potential contamination

from the repository should use an actual

volume of water, the representative

volume, to determine compliance with

the standards. Small volumes of ground

water would be difficult to model with

confidence over the long time frames

and distances appropriate for the Yucca

Mountain repository. More specifically,

we believe it is not possible to model for

the 10 acre-ft representative volume (see

the Response to Comments document

for more detail). Comment on the 120

acre-ft volume was generally that this

volume was too small for defensible

modeling, which agrees with our

assessment. As stated above, we

consider 120 acre-ft to be within the

range of feasible modeling, but very

close to the lower limit of scientifically

defensible modeling capabilities. It also

does not reflect the typical use of the

ground water resource, which is better

represented by the agricultural scenario

we have selected.

There are a number of fundamental

limitations involved in modeling the

flow of ground water over long

distances that are direct functions of the

variability of the hydrologic properties

in the aquifers along its dimensions.

Averaging assumptions are used in

modeling to greater and lesser extents to

address these limitations, as a function

of the information available regarding

the natural variability of hydrologic

properties along the flow paths. Our

approach to calculating ground water

contaminant concentrations (the well

capture zone or slice-of-the-plume

methods described in § 197.31(b))

centers the representative volume to

include the highest concentration

portion of the projected plume. If the

representative volume is too small, it

does not capture a volume large enough

to reflect the natural processes that will

occur along the flow path. Therefore,

the concentrations will be

unrealistically high and will not be a

reasonable representation of the

variations that should be expected in

the actual situation. The exact limit on

the lowest size of the representative

volume adequately reflecting modeling

limitations and the data base of

hydrologic information about the site is

a difficult expert judgment. An exact

lower limit is not possible to identify

because of the inherent limitations in

gathering site data and performing

modeling. Our opinion after extensive

discussions with qualified experts is

that a representative volume on the

order of 100 acre-ft or below is the lower

limit of modeling capability for the

Yucca Mountain ground water flow

regime (Yucca Mountain Docket, A–95–

12, Item II–E–10).

We based the 1,285 acre-ft

representative volume on a hypothetical

small farming community of 25 people

and an alfalfa farm with 255 acres under

cultivation. This approach assumes a

small community whose water needs

include domestic consumption and an

agricultural component comparable to

present water usage in the vicinity of

the repository. We based the size of the

average area of alfalfa cultivation, 255

acres, on site-specific information for

the nine existing alfalfa-growing

operations in Amargosa Valley in 1998,

which ranged in size from about 65

acres to about 800 acres (see Chapter 8

of the BID). Using a water demand for

alfalfa farming in Amargosa Valley of 5

acre-feet per acre per year, we estimate

that the annual water demand for the

average operation is 1,275 acre-ft

(Chapter 8 of the BID). An average value

of 0.4 acre-ft per person for domestic

water use is typical of the area (Chapter

8 of the BID), which for the small

community of 25 people would add 10

acre-ft for domestic uses, resulting in a

total representative volume of 1,285

acre-ft. Comments on the derivation of

the 1,285 acre-ft representative volume

supported this size as being technically

feasible for modeling and consistent

with water resource demands in the area

downgradient from the repository.

To implement the standards in

§ 197.30, we require that DOE use the

concept of a ‘‘representative volume’’ of

ground water. Under this approach,

DOE will project the concentration of

radionuclides or the resultant doses

within a ‘‘representative volume’’ of

ground water for comparison against the

standards. We have selected a value of

3,000 acre-ft/yr as the representative

volume. This value is a ‘‘cautious, but

reasonable’’ figure for protecting users

of the ground water downgradient of the

repository, as described below. Our

approach focuses on the anticipated

water use immediately downgradient of

the repository, and is closely aligned

with the alternatives offered for public

comment in our proposed rule.

The preamble to the proposed rule

noted that the representative volume

should reflect the water usage of a

hypothetical community that may exist

in the future. The preamble also noted

that the water usage should reflect the

current general lifestyles and

demographics of the area, but not be

rigidly constrained by current activities.

Using current activities and near-term

projections of planned activities in the

downgradient area leads us to three

types of water demands that can be

identified for the downgradient area:

Water demand for individual domestic

and municipal uses, water demand for

commercial/industrial uses, and water

demand for agricultural uses.

In deciding how to make this

projection, we have concluded in the

final rule that our focus in developing

an appropriate representative volume

should be to consider the spectrum of

likely downgradient uses of the ground

water resources, as well as the sitespecific hydrologic characteristics of the

disposal system itself. To avoid

speculation on all possible uses of

ground water, we have been guided by

the premise that current uses in the

immediate downgradient area, as well

as short-term projections for water uses

reflecting growth projections for the

area, should be considered in defining

an appropriate representative volume

for the ground water standard. We

believe that the most likely future uses

32112 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

will in fact take place where they are

currently located, since there is no

reason to anticipate that they will cease

occurring.

Deriving a representative volume

involves identifying water demands for

the spectrum of likely uses, and

includes an examination of projected

plume characteristics. This leads us to

focus primarily on projected uses

occurring downgradient of the

repository. As noted above, the current

and anticipated water demands

downgradient of the repository consist

of residential/municipal uses,

commercial/industrial uses and

agricultural uses.

Currently, the population at the

Lathrop Wells is small, about ten people

(BID Chapter 8), however near-term

projections for the area between Lathrop

Wells and the NTS boundary indicate

that a science museum and industrial

park are under development (Docket No.

A–95–12, Items V–A–16, V–A–19).

There are also growth projections for the

Amargosa Valley area (Docket No. A–

95–12, Items V–A–14, 15), leading us to

believe that residential/municipal water

demands as well as commercial/

industrial water demands are likely in

the near-term for the area between

Lathrop Wells and the NTS boundary.

Projected water demand for the

science museum and industrial park are

on the order of 100 acre-ft/yr (Docket

No. A–95–12, Item V–A–19). Based

upon the growth projections, we believe

that some residential population growth

should be anticipated for the area in

addition. In the preamble for the

proposed rule, we included a

representative volume of 120 acre-ft/yr

for a small residential community of

approximately 150 persons, which

included water uses for individuals and

municipal uses. We believe that these

water demands should be incorporated

into the representative volume, so that

the representative volume addresses all

potential water users. Limiting the water

demand to only one of these uses, we

believe, would not be representative of

the spectrum of potential users that

might be exposed to contaminated water

from repository releases. For example,

the water demand for the small

population at Lathrop Wells would be

on the order of less than 10 acre-ft/yr.

Our evaluations of representative

volume options in the proposed rule

(Docket No. A–95–12, Item II–E–10),

and the responses we received

concerning these options, consistently

concluded that such small volumes

would not allow credible scientifically

defensible projections to be made.

The contribution of agricultural

activities to the representative volume

can be derived from a consideration of

current farming activities in Amargosa

Valley. In the Town of Amargosa Valley,

agricultural activities consume the

largest volumes of ground water, but are

largely confined to the location

approximately 25–30 km downgradient

from the repository location. However,

the ground water used for these

activities could be contaminated if

radionuclide releases from the disposal

system were sufficiently high to exceed

the limits given in § 197.30. To protect

the agricultural resource use, we have

used alfalfa farming as a measure of

water demand. Although there is no

alfalfa farming currently at the

compliance location, and no near-term

planning for it, our approach to

protecting the resource is to include the

appropriate water demand in the

representative volume at the compliance

location. By protecting this volume

upgradient of where the actual resource

is anticipated to be tapped, we will be

protecting the larger actual volume of

water that will be used for agricultural

purposes downgradient from the

compliance location.

As described previously, alfalfa

cultivation is the largest water consumer

in the agricultural sector, and this

activity is anticipated to continue (BID

Chapter 8). We have defined an averagesized alfalfa farm based upon current

information about acreage under

cultivation in Amargosa Valley (BID

Chapter 8). We have retained this value

to avoid speculation about the future of

this particular activity for the following

reasons. The demand for alfalfa

cultivation to support the local dairy

industry in Amargosa Valley is

anticipated to be strong for the nearterm. The hydrologic basin in which

this activity takes place is fully

allocated, suggesting that dramatic

increases in alfalfa cultivation are

unlikely since the water allocations

necessary for dramatic increases are not

readily available (BID Chapter 8).

Therefore, we are using the value of

1,275 acre-feet/yr for an average-sized

farm for developing a representative

volume figure (this represents the

proposed value of 1,285 acre-feet, less

the 10 acre-feet assumed for purely

domestic use).

The anticipated behavior of the

ground-water flow system from Yucca

Mountain is important in determining

the total contribution of the agricultural

water demand to the representative

volume, since the width of potential

contamination plumes will determine

how large a volume of contaminated

ground water could be tapped for

agricultural purposes and consequently

should be protected from unacceptable

contamination. Projections of ground

water flow, from particle-tracking

analyses, have been performed by DOE

to determine the path of possible

contaminant flow from advective

transport (ground water movement)

alone (Docket No. A–95–12, Items V–A–

5, V–A–27). The particle tracks near the

compliance boundary, the

southwesternmost corner of NTS (a

distance of approximately 18 km from

the southern end of the repository),

indicate that the width of a potential

contamination plume at the compliance

location is about 1.8–2.0 kilometers.

Farther downgradient, the width of the

particle-track ground water travel path

widens slightly to a width of between 2

and 3 km. This width does not consider

dispersive effects that will occur, which

contribute to uncertainty in projecting

the actual size of a potential

contamination plume. The actual width

will be a function of a number of other

factors, including the location of failed

waste packages over time within the

repository and the particular values of

dispersion parameters chosen for

analyses. Somewhat smaller or larger

contamination plume widths could

result, but the particle track approach

results offer a satisfactory

approximation.

The average alfalfa farm we have

defined (255 acres in a square shape) is

only approximately one kilometer on an

edge. Since the exact location of a

contamination plume and the variations

in radionuclide contaminant

concentrations within it are uncertain

and cannot be projected with high

confidence, we are using two average

sized alfalfa farms across the path of the

contamination plume to increase

confidence that the highest

concentration portions of a potential

contamination plume will be included

in the representative volume, giving a

total contribution of 2,550 acre-ft/yr for

the agricultural component of the

representative volume. Again, we are

not assuming the existence of actual

farms at the compliance location, but we

are assessing the effects of radionuclide

contamination on the water volume that

they could use at more distant locations.

In total, the contributions to the

representative volume consist of the

agricultural use water demand for two

average size alfalfa farms (2,550 acre-ft/

yr), the commercial/industrial water

demand for the Lathrop Wells

development projections (100 acre-ft/

yr), and individual/municipal use water

demand for a small community

consistent with the near-term growth

projections for the area (120 acre-ft/yr).

These three components amount to

2,770 acre-ft/yr. As mentioned above,

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32113

there is significant uncertainty in the

exact location and radionuclide

concentrations in potential

contamination plumes from the

repository, and therefore we cannot be

absolutely certain that two average-sized

alfalfa farms will cover the total possible

width of a contamination plume, but we

believe including the water demand

from more than two farms would not be

entirely justified. Our intent in using the

two alfalfa farms (each 1 km in width)

is to assure that the highest

concentration portion of any

contamination plume is tapped by the

wells supplying this water demand. We

have also modified § 197.31 to allow the

use of multiple pumping wells (rather

than a single well as described in the

proposed rule) to tap the representative

volume so that technical limitations on

constructing a well withdrawal scenario

can be eliminated or minimized, should

DOE elect this alternative for calculating

radionuclide concentrations in the

representative volume.

There is, of course, uncertainty in

projecting the size and shape of

contamination plumes from the

repository as well as projecting human

activities into the future, and we have

limited this source of uncertainty by

considering only near-term projections

for growth and development in the area,

but some degree of inherent uncertainty

will always remain. To address these

residual uncertainties in this approach,

we increase the representative volume

by about 10%, to a total 3,000 acre-ft/

yr. We believe that this figure represents

a cautious, but reasonable, estimate of

the representative volume to protect the

ground water resource downgradient of

the repository.

We considered an alternative way of

evaluating the representative volume

concept for application to the ground

water protection standards. This

approach considers the larger scale

ground water flows and uses in the

larger basin (Basin 230) which receives

outflow from the basin where the

repository is located (Basin 227A). The

primary water use in this region is in

the Amargosa Desert hydrographic basin

(Basin 230, see BID Chapter 8), where

farming, mining, and other industrial

uses occur. This water comes from four

basins that have an estimated total water

budget of about 43,800 acre-feet, which

represents ground water that flows into

the Amargosa Desert basin.

The Jackass Flats basin (Basin 227A,

which includes Yucca Mountain and

the point of compliance location) is one

of four basins that flow from the north

into the Amargosa Desert basin and

provide the ground water that is used

for these activities. It is the only one of

these basins into which it is reasonable

to anticipate that water contaminated by

releases from the repository would flow.

The Jackass Flats basin contributes

about 8,100 acre-feet to the total

Amargosa Valley water budget (Table 8–

6, BID). Considering the approximate

nature of these values, it is reasonable

to approximate the contribution of the

Jackass Flats to flow into the Amargosa

Desert basin and to current water uses

at 20%.

Although the Amargosa Desert basin

has a water appropriation limit of about

41,093 acre-feet, in 1997, the reported

ground water use in the Amargosa

Desert basin was about 13,900 acre-feet

(BID Chapter 8). That is, the use was

less than appropriated. Moreover, actual

water use fluctuates significantly,

depending primarily on the level of

irrigation and mining activities in a

given year (BID Chapter 8). To estimate

the actual contribution of flow from

Jackass Flats, we again refer to the

largest water use in the area

downgradient from the repository,

which is for irrigation, particularly for

the cultivation of feed for livestock

(primarily alfalfa). There are nine alfalfa

farms in the affected area, ranging from

approximately 65 to 800 acres (BID

Chapter 8). Estimates of acreage under

cultivation for feedstock has shown a

steady increase from 1994 to 1999

(Table 8–6, BID), with an increase of

50% from 1997 to 1999. Assuming that

it also increased by 50%, the 1997

irrigation use of 9,379 acre-feet (Table

8–4, BID) could have increased by

approximately 4,700 acre-feet in 1999.

This assessment gives a range of water

use from approximately 13,900 acre-feet

in 1997 to an estimate of 18,600 acrefeet in 1999, placing the corresponding

20% contribution from Jackass Flats in

a range of approximately 2,800 to 3,700

acre-feet. From this range of possible

values, we again selected 3,000 acre-feet

as a value that is conservative (toward

the low end of the range), but also

makes an allowance for the uncertainty

inherent in these estimates.

In summary, both approaches to

deriving a ‘‘cautious, but reasonable’’

representative volume for the purpose of

ground water protection converge on a

value of 3,000 acre-ft/yr. Our approach

to developing an appropriate

representative volume considered the

size of the ground water resource and its

current and projected uses. Accordingly,

we have selected a representative

volume of 3,000 acre-feet for this rule.

This volume is within the 10 to 4,000

acre-feet range described in the

proposed rule and addressed in the

public comments and represents a

reasonable and site-specific approach to

protecting groundwater resources in the

vicinity of Yucca Mountain.

Our standards require DOE to assume

that the entire representative volume is

drawn at the compliance point, that is,

18 km south of the repository, rather

than in the Amargosa Valley itself, at 25

to 30 km south of the repository.

Therefore, it is adequate not only to

protect downgradient uses, but also to

protect all of these reasonably projected

uses, should the representative volume

be withdrawn at the compliance point.

As noted above, we believe that given

the uncertainties of projecting any

particular future and the difficulties of

modeling that using the small volumes

that would be required by relying only

on current projected uses, this is a

reasonable approach for determining

how ground water should be protected

at this particular site.

There are two basic approaches that

DOE must choose between for

calculating the concentrations of

radionuclides in the accessible

environment. The DOE may perform

this analysis by determining how much

contamination is in: (1) A ‘‘well-capture

zone;’’ or (2) a ‘‘slice of the plume’’ (see

immediately below for explanations of

these approaches). For either approach,

the volume of water used in the

calculations is equal to the

representative volume, i.e., the annual

water demand for the future group using

the ground water.

The ‘‘well-capture zone’’ is the

portion of the aquifer containing a

volume of water that one or more water

supply wells, pumping at a defined rate,

withdraw from an aquifer. The

dimensions of the well-capture zone are

determined by the pumping rate in

combination with aquifer characteristics

assumed for calculations, such as

hydraulic conductivity, gradient, and

the screened interval. If DOE uses this

approach, it must assume that the:

(1) Wells have characteristics

consistent with public water supply

wells in Amargosa Valley, for example,

well bore size and length of the

screened interval;

(2) Screened interval includes the

highest concentration in the plume of

contamination at the point of

compliance; and

(3) Pumping rate is set to produce an

annual withdrawal equal to the

representative volume.

To include an appropriate measure of

conservatism in the compliance

calculations for the well-withdrawal

approach, for the purpose of the

analysis, DOE should assume that

pumping wells that tap the highest

concentration within the projected

plume of contamination would supply

32114 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

the community water demand. This

approach achieves conservatism by

requiring that the entire water demand

is withdrawn from wells intercepting

the center of the plume of

contamination so that the highest

radionuclide concentrations in the

plume are included in the volume used

for the compliance calculations. The

well-capture zone concept is described

in more detail in Bakker and Strack,

‘‘Capture Zone Delineation in TwoDimensional Groundwater Flow

Models,’’ (1996) (Docket No. A–95–12,

Item V–A–25).

The ‘‘slice of the plume’’ is a crosssection of the plume of contamination

centered at the point of compliance with

sufficient thickness parallel to the

prevalent flow of the plume such that it

contains the representative volume. If

DOE uses this approach, it must:

(1) Propose to NRC, for its approval,

where the edge of the plume of

contamination occurs, for example,

where the concentration of

radionuclides reaches 0.1% of the level

of the highest concentration at the point

of compliance;

(2) Assume that the slice of the plume

is perpendicular to the prevalent

direction of flow of the aquifer; and

(3) Set the volume of ground water

contained within the slice of the plume

equal to the representative volume.

Both alternatives require DOE to

determine the physical dimensions and

orientation of the representative volume

during the licensing process, subject to

approval by NRC. Factors that would go

into determining the orientation of the

representative volume would include

hydrologic characteristics of the aquifer

and the well.

The DOE must demonstrate

compliance with the ground water

protection standards (§ 197.30)

assuming undisturbed performance of

the disposal system. The term

‘‘undisturbed performance’’ means that

human intrusion or the occurrence of

unlikely, disruptive, natural processes

and events do not disturb the disposal

system. The intent of the ground water

protection standards is to assess

whether the expected performance of

the repository system will lead to

contamination of the ground water

resource above the MCLs. The

assessment of resource pollution

potential is based upon the engineered

design of the repository being

sufficiently robust under expected

conditions to prevent unacceptable

degradation of the ground water

resource over time. Disruption of the

disposal system is inconsistent with that

intent. For this reason we have specified

that the ground water standards apply to

undisturbed performance. Our approach

also recognizes that human behavior is

difficult to predict and, if human

intrusion occurs, that individuals may

be exposed to radiation doses that

would be more attributable to human

actions than to the quality of repository

design (NAS Report p. 11). The

requirement that DOE project

performance for comparison with the

ground water protection standards

based on undisturbed-performance

scenarios is consistent with our

generally applicable standards for SNF,

HLW, and TRU radioactive waste in 40

CFR part 191 (58 FR 66402, December

20, 1993; 50 FR 38073 and 38078,

September 19, 1985).

We also require that DOE combine

certain estimated releases from the

Yucca Mountain disposal system with

the pre-existing naturally occurring or

man-made radionuclides to determine

the concentration in the representative

volume. This requirement means that

DOE must show a reasonable

expectation that the releases of

radionuclides from radioactive material

in the Yucca Mountain disposal system

will not cause the projected level of

radioactivity in the accessible

environment to exceed the limits in

§ 197.30.

We requested public comment

regarding these approaches to ground

water protection (i.e., the use of the

MCLs, the concept of representative

volume and the alternatives for its size

and modeling approaches, and

calculational approaches for the

representative volume application). We

also requested comments regarding

whether it is desirable and appropriate

for us to provide additional detail for

the representative volume in the final

standards.

Comments generally approved of the

idea of providing alternate approaches

for determining the concentration of

contaminants in the representative

volume. Other comments requested

additional clarification of the

approaches. We developed these

approaches to measuring the

representative volume in the plume of

contamination to provide conservative

but reasonable methods of assessing

contaminant concentrations. We intend

both methods to avoid extreme

assumptions that would involve using

only the highest potential area of

contamination in a contamination

plume for comparison against the

standards and to allow reasonable

consideration of the expected behavior

of the flow regime downgradient of the

repository. For example, the well

capture-zone approach has conservative

aspects consistent with our general

approach to regulations (a ‘‘cautious,

but reasonable’’, approach). These

aspects include locating the well in the

path of the plume and requiring it to

have characteristics similar to water

supply wells in the area, while also

allowing DOE to consider well-bore

dilution effects for the water supply

wells that realistically would be

expected in actual practice. To keep the

modeling analyses from becoming too

complicated to perform and assess with

a reasonable degree of confidence, we

specify that DOE use average hydrologic

properties to avoid the problem of

summing up possibly thousands of

individual model runs. We attempt to

specify only the most important

specifics for the two methods to provide

a necessary context to assure the

standards are understood as we intend,

but still to provide flexibility for NRC in

its implementation of the standards. For

example, we neither established

requirements nor made

recommendations regarding models to

be used for the plume modeling

methods. We left the applicant (DOE)

and the implementing authority (NRC)

the decision on defining the outer

boundary of the contamination plume

for this approach.

We received some comment asking for

additional clarification concerning the

two methods proposed for calculating

radionuclide concentrations in a

contamination plume, and in response

we have made some wording changes in

the final standards. We proposed that

the screened interval for the withdrawal

well be centered in the middle of the

contamination plume (proposed

§ 197.36 (b)(1)(ii)). The intent was to

take a conservative approach and

assume that the well taps the

contamination plume where the highest

contamination occurs, rather than being

positioned such that only a portion of

the lower concentration margin of the

plume is included in the representative

volume—such a situation would allow a

high dilution of the contamination from

pumping effects. For a physical

situation where the contamination

plume is very narrow and located at the

top of the aquifer, a physically

unrealistic situation could occur if the

well’s screened interval must be

centered on the middle of the

contamination plume, i.e., the screened

interval could extend into the

unsaturated zone above the aquifer

making calculations of well capture

zones unrealistic since a water supply

well would not be deliberately screened

in that way. To remove this unrealistic

physical situation from consideration,

we have modified the language

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32115

describing the location of the screened

interval to state that it must include the

highest concentration portion of the

plume, with the intent being that the

screened interval should cross as much

of the plume diameter as possible so

that the conservative approach is taken

to calculating radionuclide

concentrations in the ground water

(final § 197.31(b)(1)(ii)).

Another clarifying change we have

made addresses the ‘‘averaging’’ of

hydrologic properties (§ 197.31(a)(2)) in

the downgradient portions of the ground

water flow system for the purpose of

making calculations for comparison

against the ground water protection

standards. In the proposed standards,

we used the phrase ‘‘average hydrologic

characteristics’’. We did not intend to

imply that a simple arithmetic averaging

process would adequately represent the

expected variation in hydrologic

properties that results from

heterogeneity of the flow system at the

site (Chapter 7 and Appendix VI of the

BID), or that simple arithmetic averaging

would be an allowable approach. We

believe that a simple arithmetic

averaging approach would mask the

expected heterogeneity of the flow

system. The values for hydrologic

properties of the aquifers along the flow

path used in calculations should be

conservative but reasonable values,

which are representative of the expected

heterogeneity in the aquifers.

Heterogeneity can be accounted for by

using spatial statistical averaging

methods that can limit extrapolation of

data obtained from field measurements

in one locale and which are applied to

other locations represented by fewer or

poorer quality data. By using such

techniques, conservative but reasonable

data can be developed that adequately

represent the heterogeneity of the

aquifers for modeling purposes. We

have modified the proposed language to

reflect that the ‘‘averaged’’ values

should be conservative but reasonable

representations of the aquifer’s

hydrologic properties.

a. Is the Storage or Disposal of

Radioactive Material in the Yucca

Mountain Repository Underground

Injection? As we discussed in detail in

the preamble to the proposed rule, we

do not believe that the disposal of

radioactive waste in geologic

repositories is underground injection for

purposes of the SDWA (42 U.S.C. 300f

to 300j–26). We received one comment

supporting our position and one

comment disagreeing with us. See 64 FR

47004–47007 (August 27, 1999) for our

comprehensive discussion of this issue.

b. Does the Class-IV Well Ban Apply?

We previously indicated that we would

review whether the Class-IV injectionwell ban would apply to Yucca

Mountain. See 64 FR 47006–47007 for

our previous discussion of this issue.

This rulemaking does not apply the

Class-IV injection-well ban to the Yucca

Mountain repository. We believe this

approach is appropriate in light of the

statutory and regulatory provisions,

discussed above and in the preamble to

the proposed rule, relating to

‘‘underground injection,’’ and the

differences in the purposes of the

Underground Injection Control (UIC)

program and the authority delegated to

us under the EnPA to establish public

health and safety standards for Yucca

Mountain.

It is important to emphasize that our

decision not to apply the Class-IV well

ban to Yucca Mountain does not affect

other disposal systems that dispose of

hazardous or radioactive waste into or

above a formation which, within onequarter (1/4) mile of the disposal

system, contains a USDW. We based

today’s rule upon site and facilityspecific characteristics of the Yucca

Mountain disposal system. Today’s rule

is limited to the Yucca Mountain

disposal system.

c. What Ground Water Does Our Rule

Protect? Although we find that the

Yucca Mountain disposal system is not

underground injection as contemplated

by the SDWA, we nevertheless consider

the ground water protection principles

embodied in the SDWA to be important.

Therefore, although we do not apply all

aspects of the SDWA, we are

establishing separate ground water

protection standards consistent with the

levels of the radionuclide MCLs under

the SDWA.

We requested public comment upon

our approaches designed to protect

ground water resources in the vicinity of

the repository. We are concerned that

ground water resources in the vicinity of

Yucca Mountain receive adequate

protection from radioactive

contamination. The primary purpose of

our ground water standards is to prevent

contamination of drinking-water

resources. Because the compliance

period is 10,000 years after disposal,

references to levels of contamination

mean those levels projected to exist at

specific future times, unless otherwise

noted. However, these projections will

be made at the time of licensing. This

approach prevents placing the burden

upon future generations to

decontaminate that water by

implementing expensive clean-up or

treatment procedures. We believe it is

prudent to protect drinking water from

contamination through prevention

rather than to rely upon clean-up

afterwards. Absent the protection this

prevention provides, future generations

might find it necessary to intrude into

the sealed repository to remediate

radionuclides released from waste

packages inside the repository, in

addition to treating contaminated

ground water along the ground water

flow path. Thus, our ground water

protection standards stress pollution

prevention and provide protection from

contamination of sources of drinking

water containing up to 10,000 mg/L of

total dissolved solids (TDS). We

emphasize that the individualprotection standard (§ 197.20) covers all

ground water pathways, including

drinking water.

The definition of USDW received

extensive discussion in the legislative

history of the SDWA as reflected in the

report of the House Committee on

Interstate and Foreign Commerce. To

guide the Agency, the Committee Report

suggested inclusion of aquifers with

fewer than 10,000 mg/L of TDS (H.R.

Rep. No. 1185, 93d Cong., 2d Sess. 32,

1974). We have reviewed the current

information regarding the use of

aquifers for drinking water which

contain high levels of TDS. This review

found that ground water containing up

to 3,000 mg/L of TDS that is treated is

in widespread use in the U.S. In the

Yucca Mountain vicinity, with few

exceptions (one being the Franklin

Playa area), ground water contains less

than 1,000 mg/L of TDS. Our review

also found that ground water elsewhere

in the nation, containing as much as

9,000 mg/L of TDS, currently supplies

public water systems. Based upon this

review and the legislative history of the

SDWA, we are proposing that it is

reasonable to protect the aquifers

potentially affected by releases from the

Yucca Mountain disposal system.

Therefore, the provisions in § 197.30

would apply to all aquifers, or their

portions, containing less than 10,000

mg/L of TDS. We took the definitions

associated with § 197.30 directly from

our UIC regulations (40 CFR parts 144

through 146).

One comment suggested that we

change the definition of ‘‘aquifer’’ in the

final rule to exclude perched water

bodies. A perched water body is a static

area of ground water, usually above the

water table, that is unconnected to an

aquifer but that may infiltrate into an

aquifer over time. Based upon our

review of this comment, typical

definitions of ‘‘aquifer’’ in the technical

literature, and the available site-specific

information regarding the existence of

perched water bodies in the vicinity of

Yucca Mountain, we decided to make

the suggested change. This comment

32116 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

argued for this change based upon the

fact that perched water would be of

little value to future residents because

few such formations exist in the area

and because of abundant water in the

aquifer underlying Yucca Mountain.

The comment also argued that it would

be difficult to make specific predictions

regarding the location and

characteristics of perched water bodies.

Finally, the comment stated it would

not be meaningful to attempt to model

perched water bodies in any

performance assessment. There are only

a few, small perched water bodies

known to be in the vicinity of Yucca

Mountain (see Chapter 7 of the BID).

Also, traditional definitions of ‘‘aquifer’’

usually do not include perched water

bodies (see the Glossary in the BID). Our

intent also is to provide protection to

water resources of sufficient size to

supply water on a continuing basis to

targeted uses. Perched water bodies,

particularly as they have been observed

in the Yucca Mountain area, are

relatively small and would not provide

a continual source of water to wells

used for irrigation or for community

water demands. Based upon this

information, we believe that it is

unnecessary to include these bodies in

the definition of ‘‘aquifer’’ because it is

extremely unlikely that they could serve

as a consistent source of drinking water.

Therefore, we amended the definition of

‘‘aquifer’’ to exclude perched water

bodies.

d. How Far Into the Future Must DOE

Project Compliance With the Ground

Water Standards? We are establishing a

10,000-year compliance period for

ground water protection. The primary

rationale for establishing a 10,000 year

compliance period is that we are

significantly concerned about the

uncertainty associated with projecting

radiation doses over periods longer than

10,000 years. The NAS indicated that

beyond 10,000 years it is likely that

uncertainty will continue to increase

(NAS Report p. 72). As a result, it will

become increasingly difficult to discern

a difference between the radiation dose

from drinking water containing

radionuclides (limited by the MCLs) and

the total dose arriving through all

pathways (limited by the individualprotection standard). Moreover, this

approach is consistent with the 10,000-

year compliance period we are

establishing for the individualprotection standard. Therefore, it

provides internal consistency within the

standards. It is also consistent with

regulations covering long-lived

chemically hazardous wastes, which

present potential health risks similar to

those from radioactive waste, and with

the compliance period that we

established in our generally applicable

radioactive waste disposal standards at

40 CFR part 191.

We requested comment regarding our

proposal to impose the ground water

protection standards during the first

10,000 years following disposal.

Question 14 in the preamble to our

proposal specifically asked: ‘‘Is the

10,000-year compliance period for

protecting the RMEI and ground water

reasonable or should we extend the

period to the time of peak dose?’’ (64 FR

47010–47011) Comments related to the

compliance period applied to both the

RMEI and ground water. See the

discussion of issues pertaining to both

the RMEI and ground water protection

in section III.B.1.g (How Far Into the

Future Is It Reasonable to Project

Disposal System Performance?) along

with our rationale for adopting a 10,000-

year compliance period.

e. How Will DOE Identify Where to

Assess Compliance With the Ground

Water Standards? To provide a basis for

determining projected compliance with

the ground water protection standards

in § 197.30, it is necessary to establish

a geographic location where DOE must

project the concentrations of

radionuclides in the ground water over

the compliance period. This location is

the ‘‘point of compliance.’’

Our understanding, based upon

current knowledge, of the flow of

ground water passing under Yucca

Mountain is as follows (except where

noted otherwise, Chapter 7 and

Appendix VI of the BID are the sources

for the information in this paragraph).

The general direction of ground water

movement in the aquifers under Yucca

Mountain is south and southeast. The

major aquifers along the flow path are

in fractured tuff, alluvium, and,

underlying both of these, the deeper

carbonate rocks. At the edge of the

repository, the tuff aquifer is relatively

(several hundred meters) thick. The tuff

aquifer gets closer to the surface toward

its natural discharge points. Potential

releases of radionuclides from the

engineered barrier system into the

surrounding rocks would be highly

directional and would reflect the

orientation of fractures, rock unit

contacts, and ground water flow in the

area downgradient from Yucca

Mountain. Directly under the repository,

we anticipate that any waterborne

releases of radionuclides will move

through the unsaturated zone and

downward into the tuff aquifer, in an

easterly direction, between layers of

rocks that slant to the east, and

downward along generally vertical

fractures in the rock units until reaching

the saturated zone. The layer of tuff

gradually thins proceeding south

(downgradient) from Yucca Mountain.

As the tuff aquifer thins, the overlying

alluvium becomes thicker until the tuff

disappears and the water in the aquifer

moves into the alluvium to become the

‘‘alluvial aquifer.’’ Along the flow path,

there might be movement of water

between the carbonate aquifer and

either the tuff or alluvial aquifers. If

there is significant upward flow from

the carbonate aquifer, contamination in

overlying aquifers could be diluted. It is

generally believed, however, that any

such flow would not significantly affect

the concentration of radionuclides in

the overlying aquifers. Conversely,

downward movement of ground water

from the tuff aquifer could contaminate

the carbonate aquifer. Limited

information currently available

indicates that ground water from the

lower carbonate aquifer moves upward

into the overlying aquifer; however, this

interpretation may not be correct for the

entire flow path from beneath the

repository to the compliance points

southward from Yucca Mountain.

Today, most of the water for human use

is withdrawn between 20 and 30 km

away from the repository footprint (that

is, at Lathrop Wells and farther south

through the Town of Amargosa Valley)

where it is more easily and

economically accessed for agricultural

use and human consumption. It is likely

that the alluvial aquifer is the major

source of this water (see Chapter 8 and

Appendix V of the BID).

Another basis of our understanding is

the historical record of water use in the

region. The record indicates that

significant, long-term human habitation

has not occurred in the southwestern

area of NTS, or for that matter anywhere

in the vicinity of Yucca Mountain,

except where ground water is very

easily accessed (for example, in Ash

Meadows) (see Chapter 8 of the BID).

This observation coincides with current

practice whereby the number of wells

generally decreases with greater depth

to ground water (see Chapter 8 of the

BID). The difficulty in accessing ground

water in the tuff aquifer in the near

vicinity of Yucca Mountain increases

because of the rough terrain, the relative

degree of fracturing of the tuff

formations containing the aquifer, and

the great depth to ground water there.

As described earlier, the ground water

flow from under Yucca Mountain is

thought to be generally south and

southeast. In those directions, the

ground water gets progressively closer

to the Earth’s surface the farther away it

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32117

gets from Yucca Mountain until it is

thought to discharge to surface areas 30–

40 km away (the southwestern boundary

of NTS is about 18 km from Yucca

Mountain). This means that access to

the upper aquifer is easier at increasing

distance from Yucca Mountain.

Because of DOE’s ongoing site

characterization studies, it is possible

that, at the time of licensing, data not

now available will reveal important

inaccuracies in the preceding

conception of the ground water flow

under, and downgradient from, Yucca

Mountain. We intend compliance with

the ground water standards to be

assessed where DOE and NRC project

the highest concentrations of

radionuclides in the representative

volume of ground water in the

accessible environment. The DOE will

determine this location by modeling

releases into the saturated zone beneath

the repository and the subsequent

movement of radionuclides

downgradient from Yucca Mountain.

After selecting a location, however, DOE

must continue to evaluate new

information regarding ground water

flow. If this new information indicates

that the highest concentrations would

occur at a location in the accessible

environment different from the one

selected by DOE and NRC, DOE must

propose a new compliance location to

NRC. The new location is subject to

NRC’s approval. The next section

discusses the concept of accessible

environment as it relates to the

controlled area.

f. Where Will Compliance With the

Ground Water Standards be Assessed?

We presented four alternatives for

comment prior to determining the

location of the point of compliance. See

the preamble to the proposed rule (64

FR 47000–47004) for a detailed

discussion of these four alternatives. We

asked commenters to address the

effectiveness of these or other

alternatives for protecting ground water,

including consideration of site-specific

characteristics and reasonable methods

of implementing the alternatives.

After reviewing and evaluating the

public comments, various precedents,

the EnPA, and NAS’s recommendations,

we adopted the concept of a controlled

area as an essential precondition to

assessing compliance with the ground

water standards. The ground water

standards must be met in the accessible

environment where the highest

radionuclide concentrations in the

representative volume of ground water

are projected to occur during the

compliance period (10,000 years). The

highest projected concentrations will be

compared to the regulatory limits

established in today’s rule. The

accessible environment includes any

location outside the controlled area. The

controlled area may extend no more

than 5 km in any direction from the

repository footprint, except in the

direction of ground water flow. In the

direction of ground water flow, the

controlled area may extend no farther

south than latitude 36°40′13.6661′′

North, which corresponds to the

latitude of the southwest corner of the

Nevada Test Site, as it exists today

(Department of Energy submittal of

Public Land Order 2568, dated

December 19, 1961, Docket No. A–95–

12, Item V–A–29). The size of the

controlled area may not exceed 300 km2

(see below for further discussion). Such

a limitation is derived by combining the

concept of the controlled area as used in

40 CFR part 191 and the requirement for

a site-specific standard in the case of

Yucca Mountain. If fully employed by

DOE, and based on current repository

design, the controlled area could extend

approximately 18 km in the direction of

ground water flow (presently believed to

be in a southerly direction) and extend

no more than 5 km from the repository

footprint in any other direction.

Allowing for a nominal repository

footprint of a few square kilometers, this

results in a rectangle with approximate

dimensions of 12 km in an east-west

direction and 25 km in a north-south

direction, or approximately 300 km2.

The DOE may define the size and shape

of the controlled area, but the

boundaries cannot extend farther south

than latitude 36°40′13.6661′′ North in

the direction of ground water flow and

5 km in any other direction.

The alternatives for the ground water

standards’ compliance point presented

in the proposed rule correspond to

downgradient distances of

approximately 5, 18, 20, and 30 km from

the repository footprint. The first

alternative mirrored the approach used

in 40 CFR part 191. This approach

incorporates the concept of a controlled

area, not to exceed 100 km2, and not to

extend more than 5 km in any direction

from the repository footprint. The

second alternative also incorporated the

concept of a controlled area, not to

extend more than 5 km in any direction

from the footprint, except that DOE

could include any contiguous area

within the boundary of NTS. The last

two alternatives described specific

points of compliance at distances of

about 20 and 30 km, respectively, from

the repository footprint. We also

intended these controlled areas and

points of compliance to be in the

predominant direction of ground water

movement from the repository.

Consequently, they would reflect the

transport path for radionuclides

released from the repository. We

intended the controlled area options to

describe that area of land dedicated to

the sole use of serving as the natural

barrier portion of the disposal system.

Compliance with the standards within

the controlled area is not an issue in

regulatory decision making because this

area is considered part of the overall

disposal system and is dedicated to

limiting radionuclide transport by

means of the natural processes operative

within it. Rather, compliance will be

judged at the location where projected

concentrations are highest and that is no

closer to the repository than the edge of

the controlled area. The controlled area

also serves as the basis for institutional

control measures intended to limit

access around the repository site. This

use of the controlled area, to limit

access to the site, is an assurance

measure we have left to the discretion

of NRC as the implementing authority.

Our rule does not require any specific

institutional controls to be applied to

the controlled area. As part of the

licensing process, DOE will propose the

specific shape and size of the controlled

area. The NRC’s proposed rule

establishing licensing criteria for the

Yucca Mountain facility specifically

requires that DOE have permanent

control of the land. We anticipate that

Congress and the President will

authorize a legislative withdrawal of an

area within which the site is located.

The DOE will determine the extent of

land that will be requested of Congress

to legislatively withdraw from all other

public or private use. For its DEIS

(Docket No. A–95–12, Item V–A–4),

DOE analyzed a potential land

withdrawal area of 600 km2 in the

context of site characterization needs.

The legislative land withdrawal

represents the societal decision on the

area of land to be dedicated to the

characterization and operation of a

disposal system. Although the land

withdrawal may exceed 300 km2, we

limit the controlled area to 300 km2 for

the purpose of defining the maximum

geological volume which may be

included in the disposal system.

We adopted the concept of a

controlled area from the generic

standards in 40 CFR part 191. Those

standards state that the maximum size

of the controlled area is 100 km2 (40

CFR 191.12). After examining the

available information concerning the

characteristics of the Yucca Mountain

site, the current understanding of the

expected performance of the disposal

32118 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

system and the repository engineered

barrier system design, and comments

received on our proposed approach to

ground water protection, we believe that

a controlled area of up to 300 km2 will

adequately address the site-specific

conditions at Yucca Mountain.

It would be unreasonable for us to

limit DOE’s flexibility while site

characterization and disposal system

design are continuing, or to issue

standards that do not account for the

uncertainties of ground water flow in

the region. Therefore, today’s rule

provides that the size of the controlled

area may be up to 300 km2.

In reaching this decision regarding the

maximum size of the controlled area, we

must draw a contrast between the

approach used in 40 CFR part 191 and

today’s rule. As mentioned earlier,

although the WIPP LWA exempted the

Yucca Mountain site from licensing

under the provisions of 40 CFR part 191,

the radiation protection principles in 40

CFR part 191 are still applicable, and we

examined them while developing sitespecific standards for Yucca Mountain.

Throughout this preamble, we note

where and why we have carried some of

the concepts forward from 40 CFR part

191 if we believe they are necessary for

protective standards at Yucca Mountain,

and how we have applied them in ways

consistent with the site-specific

information and understanding of the

Yucca Mountain site. Part 191

established a controlled area with a

maximum distance in any direction of 5

km from the repository footprint to

provide a location for judging

compliance with the individualprotection (§ 191.15), ground water

protection (§ 191.24), and containment

requirements (§ 191.13). Thus, the

controlled-area concept in 40 CFR part

191 links a 5 km maximum distance

from the repository footprint to a limit

on the size of the controlled area (100

km2 maximum). Within this area,

compliance with the standards is not

required because the geologic media

therein comprise an essential part of the

disposal system. This combination of

controlled area and protection of

individuals and ground water is

appropriate for generic standards

because generic standards’ provisions

must account for the wide variety of

possible site conditions (e.g., releases

could move in many directions from the

repository toward the population),

engineered alternatives, and population

characteristics. Note that in the 1980s,

when 40 CFR part 191 was being

developed, DOE was considering nine

candidate HLW repository sites. It is

also important to recognize that 40 CFR

part 191 contained a mechanism for

substituting alternative provisions,

should they be deemed necessary.

By contrast, 40 CFR part 197 is sitespecific. The 1987 NWPA amendments

specified Yucca Mountain as the only

potential repository site where DOE may

conduct characterization activities.

Therefore, since passage of the 1987

amendments, the Yucca Mountain site

has been under an intense

characterization effort. Because of these

efforts, a significant amount of

information has been generated

regarding past, present, and planned

population patterns, land use,

engineered design, and the

hydrogeological characteristics of the

host rock and ground water systems at

the Yucca Mountain site. Based upon

information currently available, it

appears that contaminated ground water

will flow predominantly in a relatively

narrow path from the Yucca Mountain

repository. See the Yucca Mountain

DEIS, Chapter 3 (DOE/EIS–0250 D, July

1999, Docket No. A–95–12, Item V–A–

4, and the Viability Assessment, Docket

No. A–95–12, Item V–A–5). In addition

to the extensive data base compiled over

the years, we have the recommendations

of NAS. Significantly, NAS endorsed

the use of present knowledge using

‘‘cautious, but reasonable’’ assumptions

in defining exposure scenarios (NAS

Report p. 100).

Concerning the size of the controlled

area, though we have a general

understanding of the primary direction

of ground water flow, our present

knowledge continues to evolve through

site characterization. As a result, we

believe the ‘‘cautious, but reasonable’’

approach allows DOE the flexibility to

utilize a controlled area up to a

maximum of 300 km2. Given the

uncertainty in ground water flow paths,

and the fact that releases could occur

anywhere within the repository, we

believe it is prudent to ensure that any

potential contamination plumes from

repository releases are contained within

the controlled area, and to ensure that

access to and human activity within the

area of potential contamination is

limited, thereby minimizing the

potential for human exposure. We

recognize that 300 km2 represents an

increase in the maximum size of the

controlled area, and is larger than we

allow in 40 CFR part 191. However, for

site-specific reasons, we are increasing

the maximum extent of the controlled

area only in the direction of ground

water flow to no farther south than

latitude 36° 40′ 13.6661′′ North, while

simultaneously limiting the extent of

the controlled area in any other

direction to no greater than 5 km from

the repository footprint.

The size and shape of the controlled

area proposed by DOE in the licensing

process will depend upon two

fundamental elements: (1) The

dimensions of the repository layout for

the waste inventory and thermal

loading, as defined in the final

repository design; and (2) uncertainty in

ground water flow directions. Both of

these aspects are evolving since studies

for both site characterization and

repository design are still in progress.

However, DOE provides some

indication in its DEIS of the range of

repository-design layouts under various

assumed waste inventories and thermal

loading alternatives. Combining these

repository alternatives in the DEIS, with

projected ground water flow paths to the

southern most extension of the

controlled area at latitude 36° 40′

13.6661′′ North, gives potential

controlled area sizes from 100 km2 or

less to around 300 km2. These estimates

are based upon the uncertainties in

ground water flow directions and

repository designs that currently exist.

When characterization and design

studies are completed, a well-defined

controlled area size can be determined

during the licensing process, where the

uncertainties will be examined in closer

detail and a final controlled area size

can be determined. However,

uncertainties can only be reduced, not

eliminated completely, even when site

characterization is completed—some

residual uncertainty will remain. As

stated earlier, we believe it is important

to allow flexibility for DOE and NRC at

this time to continue the

characterization and design work, and

allow the licensing process to operate

within certain bounds while knowledge

of the site is evolving.

In addition to ground water flow path

uncertainties, the size and shape of the

controlled area also depend upon

understanding how and where (in

relation to the repository layout)

radionuclides could be introduced into

the ground water. Failed waste packages

during the regulatory time-frame supply

the releases carried into the ground

water system. While DOE has adopted a

new highly engineered waste package

anticipated to have containment

lifetimes into the tens of thousands of

years (TRW Environmental Safety

Systems Inc., ‘‘Repository Safety

Strategy: Plan to Prepare the Postclosure

Safety Case to Support Yucca Mountain

Site Recommendation and Licensing

Considerations’’, TDR–WIS–RL–000001,

January 2000, Docket No. A–95–12, Item

V–A–24), some small number of waste

packages can be anticipated to fail

within the regulatory period due to

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32119

undetected manufacturing defects.

While these failures can be minimized

through rigorous quality control efforts

during manufacturing, the potential

cannot be totally eliminated. The

location of such ‘‘premature failures’’ in

the repository is, however,

unpredictable. Other unpredictable

disruptive events and processes, such as

roof falls that damage waste packages

and accelerate corrosion processes,

could also result in releases in advance

of the anticipated containment lifetime

of the containers under expected

conditions. The location of these types

of waste package failures is also not

amenable to reliable prediction.

Therefore, releases from such failures

could originate anywhere within the

repository footprint and would

consequently enter the ground water

flow envelope at any location.

Recognizing this, the process of defining

the controlled area would focus upon

the two factors discussed above, the

repository footprint, which will reflect

the waste inventory and the repository

design choices, and the envelope of

potential ground water flow paths

around that footprint. ‘‘Cautious, but

reasonable’’ assumptions regarding

these factors can then be applied to

define a controlled area that will

include potential releases from a small

number of premature waste package

failures. A more detailed discussion of

the influence of these factors on the

potential size of the controlled area may

be found in ‘‘Considerations for

Defining a Site-Specific Controlled Area

for the Yucca Mountain Proposed

Repository Location’’ (Docket No. A–

95–12, Item V–B–7).

Regarding the alternatives we

proposed for the ground water point of

compliance, none of the information we

have reviewed suggests that it is likely

or reasonable to assume that year-round

residents will live within 5 km of the

repository footprint. As discussed in

Chapter 8 and Appendix IV of the BID,

it would be extremely difficult to farm

that close to Yucca Mountain, partly

because extracting ground water at that

location would be both technically

challenging and very expensive for an

individual or small group. In addition,

much of this area has rough terrain and

soils not conducive to farming. Our

understanding of projections of future

land use does not indicate significant

population growth much farther north

of Lathrop Wells, i.e., closer than about

18 km from the repository footprint (see

Appendix I of the BID, Docket No. A–

95–12, Items V–A–14, 15, 16). Given the

small likelihood of a year-round

resident at 5 km, we chose not to select

a distance of 5 km as the limiting

distance from the repository footprint to

the controlled area boundary.

As one goes farther away from Yucca

Mountain in the direction of ground

water flow, it is easier to drill for ground

water because the water table is closer

to the ground surface and the geologic

medium changes from tuff to alluvium.

In addition, the soil characteristics

improve such that agricultural pursuits

become more feasible, as evidenced by

the widespread agricultural activity in

Amargosa Valley some 30 km from

Yucca Mountain. There are

approximately 10 residents at about 20

km (Lathrop Wells) and hundreds of

residents at a distance of 30 km. Current

projections of population growth

indicate southern Nevada as one of the

fastest growing areas in the country (see

the Yucca Mountain DEIS, Chapter 3

(DOE/EIS–0250D, July 1999, Docket No.

A–95–12, Item V–A–4), and reports

prepared for Nye County and Amargosa

Valley (Docket No. A–95–12, Items V–

A–14, V–A–15, and V–A–16)). We

selected latitude 36° 40′ 13.6661′′ North,

which corresponds to the southwest

corner of NTS as it exists today (Docket

No. A–95–12, Item V–A–29), as the

maximum distance that the controlled

area may extend in the direction of

ground water flow (south). Given the

expected population growth in southern

Nevada, it is reasonable to project that

some population growth may occur

slightly north of Lathrop Wells,

although the boundaries of NTS are

likely to remain and restrict population

expansion in this direction, at least for

the near future. As indicated previously,

the representative volume of ground

water used to demonstrate compliance

would reflect a small community

including alfalfa cultivation and some

residential and light industrial

development. At distances progressively

closer than 18 km to the repository, it

becomes more difficult to drill for water,

soil conditions become less favorable for

agriculture, and more land is subject to

restricted access by the Federal

government. We believe, based upon the

site-specific information now available,

and using cautious, but reasonable

assumptions, the southwest corner of

NTS, or an equivalent distance in the

direction of ground water flow, would

be the closest location for a small group

to be accessing ground water.

Several comments suggested that we

should locate the point of compliance

for ground water protection purposes at

the boundary of the Yucca Mountain

repository footprint. As discussed

above, 40 CFR part 191 established the

concept that a certain amount of geology

surrounding a repository is part of the

overall disposal system. The controlledarea concept limited considerations of

radiation dose to individuals or

contamination of ground water to areas

outside of this controlled area. The

controlled area in 40 CFR part 191

applies at a distance from the

repository, to be determined by the

implementing agency, but not to exceed

5 km from the footprint. We continue to

support the concept of a compliance

point at some distance beyond the

repository footprint. In the case of

Yucca Mountain, most of the land

within the repository footprint is rugged

terrain, with extreme depths to ground

water, and land unsuitable for

agricultural pursuits (see Chapter 8 of

the BID). Therefore, we did not choose

a compliance point at the edge of the

Yucca Mountain repository footprint.

A number of comments suggested we

locate the point of compliance, or limit

the distance to the boundary of the

controlled area, at distances ranging

from 5 km to 30 km from the repository

footprint. As we indicated previously,

we adopted NAS’s recommendations to

use present knowledge and cautious,

but reasonable, assumptions in making

regulatory decisions. For the reasons

discussed earlier, we did not choose to

base compliance with the standards

upon a uniform 5 km distance from the

repository. Other comments supported

placing the compliance point at 30 km,

citing the volume of water currently

withdrawn at that distance. Indeed,

most of the agricultural activities in the

vicinity of Yucca Mountain currently

take place in this area, and it is home

to hundreds of residents. This situation

occurs because of the easy accessibility

of ground water and soil conditions

conducive to a variety of agricultural

activities. However, a distance of 30 km

would effectively ignore the existence of

populations who presently access

ground water closer to the repository.

Given the prospect of future population

growth as well, at distances of about 20

to 30 km from the repository footprint,

it would appear more reasonable to

protect ground water resources at

distances closer than 30 km. Therefore,

we did not choose the ‘‘30 km’’

alternative as the compliance point.

Distances approximating 20 km

appear more reasonable to consider to

assess compliance with the ground

water standards. As described in

Chapter 8 of the BID, no farming

currently occurs closer than about 23

km from the repository footprint. Also,

as one gets closer than about 18 km to

the repository footprint, the depth to

water begins to increase dramatically

from about 100 m at a distance of 20 km

to a few hundred meters at a distance of

32120 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

5 km. Given the expectation of future

population growth and the precious

nature of ground water resources in the

area, it is reasonable to assume that a

small group may annually extract the

representative volume of ground water

at a distance slightly closer than 20 km,

namely, latitude 36° 40′ 13.6661′′ North,

which corresponds to the southwest

corner of NTS as it exists today (Docket

No. A–95–12, Item V–A–29). This

approach is protective of the ground

water resources reasonably anticipated

to be accessed in the vicinity of Yucca

Mountain. To determine compliance

with the ground water standards, DOE

must define the controlled area and

calculate the concentrations of

radionuclides in the representative

volume of ground water at a location

outside the controlled area where the

concentrations are the highest. The

controlled area may encompass no more

than 300 km2 and may extend no farther

south, in the direction of ground water

flow, than latitude 36° 40′ 13.6661′′

North, which corresponds to the

southwest corner of NTS (Docket No. A–

95–12, Item V–A–29). In any other

direction, the controlled area may

extend no more than 5 km from the

repository footprint. We emphasize that

these dimensions describe the

maximum size of the controlled area. In

defining the actual dimensions of the

controlled area, DOE may extend the

southern boundary of the controlled

area as far as latitude 36° 40′ 13.6661′′

North, which corresponds to the

southwest corner of the NTS (Docket

No. A–95–12, Item V–A–29). The DOE

could place the boundary of the

controlled area anywhere along that

distance. Therefore, when we say we

did not base compliance with the

standard upon a distance of 5 km from

the repository footprint, we mean that

we neither selected the alternative that

would have set the maximum

dimension of the controlled area as 5

km in any direction, nor did we identify

a specific point of compliance at that

distance. The DOE is free to define the

controlled area such that it extends only

5 km, or less than 5 km, in any direction

(i.e., DOE is not required to extend the

controlled area as far as latitude 36° 40′

13.6661′′ North in the direction of

ground water flow, or as far as 5 km

from the repository footprint in any

other direction), and to assess

compliance at the location outside the

controlled area where concentrations

are highest. In the context of waste

disposal, the ground water protection

standards do not apply inside the

controlled area, consistent with the

approach in 40 CFR part 191.

IV. Responses to Specific Questions for

Public Comment

In addition to requesting comments

regarding all aspects of this rulemaking,

many of which we have highlighted in

the preceding sections of this document,

we also requested comment based upon

sixteen specific questions. These

specific questions appear below, along

with brief summaries of the comments

we received and our responses to those

comments. As with each of the

comments discussed elsewhere in this

document, we present detailed and

comprehensive responses in the

accompanying Response to Comments

document.

1. The NAS Recommended That We

Base The Individual-protection

Standard Upon Risk. Consistent With

This Recommendation and the

Statutory Language of the EnPA, We are

Proposing a Standard in Terms of

Annual CEDE Incurred by Individuals.

Is Our Rationale for This Aspect of Our

Proposal Reasonable?

Comments/Our Responses. Many of

the comments we received on this issue

supported the promulgation of a

standard stated in terms of dose.

Moreover, section 801(a)(1) of the EnPA

specifically provides that EPA shall

‘‘promulgate, by rule, public health and

safety standards for protection of the

public from releases from radioactive

materials stored or disposed of in the

repository at the Yucca Mountain site.

Such standards shall prescribe the

maximum annual effective dose

equivalent to individual members of the

public from releases from radioactive

materials stored or disposed of in the

repository.’’ Consistent with the specific

statutory language of the EnPA, and the

numerous comments supporting the use

of a standard stated in terms of dose, we

choose to use dose as the form of the

individual-protection standard. See

section III.B.1.a above for a discussion

of our rationales for making this choice.

As discussed to some extent in section

III.B.1.c, and in more detail in the

preamble to the proposed standards

(beginning on 64 FR 46984), the primary

basis of the dose limit, 150

microsieverts (15 mrem), is the risk of

fatal cancer. This level equates to an

annual risk of about 8.5 in one million

of developing a fatal cancer. This level

is within the risk range recommended

by NAS. Thus, the 15 mrem CEDE

standard is consistent with NAS’s

recommendation.

2. We Are Proposing an Annual Limit of

150 μSv (15 mrem) CEDE To Protect the

RMEI and the General Public From

Releases From Waste Disposed of in the

Yucca Mountain Disposal System. Is

Our Proposed Standard Reasonable To

Protect Both Individuals and the

General Public?

Comments/Our Responses. As noted

in section III.B.1.c above, we are

establishing an individual-protection

standard for Yucca Mountain that limits

the annual radiation dose incurred by

the RMEI to 150 μSv (15 mrem) CEDE.

See section III.B.1.c for a discussion of

the comments regarding the

appropriateness of the level of

protection. We chose not to adopt a

separate limit on radiation releases for

the purpose of protecting the general

population. There is a full description of

our reasoning in section III.B.1.e, above.

However, in summary, we based this

decision upon several factors. The first

factor is NAS’s estimate of extremely

small doses to be received by

individuals resulting from air releases

from the Yucca Mountain disposal

system. The projected level of these

doses is well below the risk level

corresponding to our individualprotection standard for Yucca

Mountain. It also is well below the level

that we have regulated in the past

through other regulations. We also

declined to establish a negligible

incremental dose (NID) level below

which doses would not have to be

calculated. The second factor is that,

based upon current, site-specific

conditions near Yucca Mountain, it is

unlikely that there will be great dilution

and wide dispersal of radionuclides

transported in ground water leading to

exposure of a large population. This

means that the individual-dose standard

will suffice to protect the general

population. There should be no

confusion between establishment of this

standard and our establishment of

ground water protection standards

intended to protect that water for future

use. The final factor is that we require

all of the pathways, including air and

ground water, to be analyzed by DOE

and considered by NRC under the

individual-protection standard.

Regarding the concepts of negligible

incremental dose or risk, though we

have recognized elsewhere in this

preamble that individual doses from

14C are below the level at which the

Agency has historically regulated

individual doses, we have declined to

establish an NID or NIR level for the

reasons enumerated in section III.B.1.e

in this preamble. As described by NCRP,

the concepts of NID and NIR relate to

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32121

individual-dose assessments, not

collective dose assessments (Docket A–

95–12, Item II–A–8). Therefore, we are

not prepared to accept the NIR concept

as discussed by NAS.

We also disagree with NAS when it

states on page 120 of its report: ‘‘On a

collective basis, the risks to future local

populations are unknowable.’’ There is

no question that there will be

uncertainty in the estimate; however,

even without our recommendation, DOE

has already published projected

collective doses for Yucca Mountain

(see Table 4–34 on p. 4–39 of the Yucca

Mountain DEIS, Docket No. A–95–12,

Item V–A–4), and is likely to refine

these estimates. These estimates could

fulfill the NCRP recommendation to use

collective dose in a non-regulatory

fashion to assess acceptability of a

facility (Docket No. A–95–12, Item II–

A–8).

Most comments on this issue

supported not establishing a collectivedose limit for Yucca Mountain. Two

other comments supported our decision

to not establish an NIR or NID level.

One comment went further by opposing

our suggestion that DOE use estimated

collective dose to examine design

alternatives on the grounds that such

action is unnecessary to protect the

general public. That comment also

stated that we have not provided

guidance on what to do with the

collective dose estimates and that we

are making policy judgments with

respect to collective dose estimation.

Upon consideration of those comments,

we are not recommending that DOE

estimate collective dose, primarily

because we believe that the individualprotection standard will adequately

protect the general population.

3. To Define Who Should Be Protected

by the Proposed Individual-protection

Standard, We Are Proposing To Use an

RMEI as the Representative of the Ruralresidential CG. Is Our Approach

Reasonable? Would it be More Useful to

Have DOE Calculate the Average Dose

Occurring Within the Rural-residential

CG Rather Than the RMEI Dose?

Comments/Our Responses. We

decided that the RMEI in the individualprotection scenario will have a ruralresidential lifestyle. A number of

comments supported the use of the CG

approach. One commenter suggested

specifically that it preferred a ruralresidential CG to the rural-residential

RMEI because it is possible to estimate

exposures with much greater

confidence. However, in general, we

decided to use the rural-residential

RMEI rather than a rural-residential CG

for the same reasons that we selected

RMEI instead of the CG (see section

III.B.1.d above, and Docket No. A–95–

12, Item V–B–3).

In summary, those reasons are that the

RMEI approach:

(1) Is consistent with widespread

practice, current and historical, of

estimating dose and risk incurred by

individuals even when it is impossible

to specify or calculate accurately the

exposure habits of future members of

the population (as in this case where it

is necessary to project doses for very

long periods);

(2) Is sufficiently conservative and

fully protective of the general

population;

(3) Provides protection similar to the

probabilistic CG approach

recommended by NAS for small

groups—it has the same goal and

purpose as does NAS’s recommended

probabilistic CG approach, i.e., to

protect the vast majority of the public

while ensuring that the acceptability of

the repository is not driven by

unreasonable and extreme cases. It

accomplishes this by employing some

maximum parameter values and some

average parameter values (similar to the

NAS’s concept of using ‘‘cautious, but

reasonable’’ assumptions) for the factors

most important to estimating the dose to

arrive at a conservative, but reasonable,

projection of future dose;

(4) Allows the desired degree of

conservatism to be built but within the

site-specific limits and the framework

which we have established.

(5) Is straightforward and relatively

simple to understand, and is more

appropriate than the probabilistic CG for

the situation at Yucca Mountain. It is

less speculative to implement than is

the probabilistic CG approach given the

unique conditions present at Yucca

Mountain (and is a cautious, but

reasonable, approach). For example,

given the known characteristics of

ground water flow at Yucca Mountain,

locating the receptor in the direct path

is more protective, and easier to

implement, than assessing an average

dose incurred by a randomly-located

group of receptors; and,

(6) Has been used by us in the past

(whereas we have not used the CG

concept).

A number of other comments

suggested other groups or individuals

that would represent more appropriately

the individual to be protected by the

individual-protection standard. The

suggestions included a fetus, the elderly

and infirm, and subsistence farmers.

Regarding the various ages and stages of

development, the risk value used for the

development of cancer is an overall

average risk value (see Chapter 6 of the

BID for more details) that includes all

exposure pathways, both genders, all

ages, and most radionuclides. However,

it does not cover the ‘‘unborn within the

womb’’ (see Chapter 6 of the BID). It is

thought that the risk per unit dose for

prenatal exposures is similar to the

average risk per unit dose for postnatal

exposures; however, the exposure

period is very short compared to the rest

of the individual’s average lifetime. (See

Chapter 6 of the BID for a discussion of

cancer risk from in utero exposure).

Therefore, the risk is proportionately

lower and would not have a significant

impact upon the overall risk incurred by

an individual over a lifetime (see

Chapter 6 of the BID). On the other end

of the age spectrum, radiation exposure

of the elderly at the levels of the

individual-protection standard would

be less than the overall risk value

because they have fewer years to live

and, therefore, fewer years for a fatal

cancer to develop (see Chapter 6 of the

BID). Finally, we did not use

subsistence farmers because we do not

believe that they are representative of

the current lifestyle in Amargosa Valley

and that, therefore, they would not

constitute a cautious, but reasonable,

assumption in relation to the guidance

from NAS to use current technology and

lifestyle.

4. Is it Reasonable To Use RMEI

Parameter Values Based Upon

Characteristics of the Population

Currently Located in Proximity to Yucca

Mountain? Should We Promulgate

Specific Parameter Values in Addition

To Specifying the Exposure Scenarios?

Comments/Our Responses. The basis

of the RMEI dose calculations will be

the current population downgradient

from Yucca Mountain. This approach is

consistent with NAS’s recommendation

to use current lifestyles to avoid the

endless speculation that could result

from trying to project future human

activities. See section III.B.1.d above for

a discussion of this issue. Most

commenters supported this approach.

However, a number of commenters

preferred using a subsistence-farmer

lifestyle. We have been unable to

identify this lifestyle in the area around

the Yucca Mountain site. Also, a few

commenters stated that we should take

future changes in population, land use,

climate, and biota into consideration.

Again, with the exception of climate

and geologic processes, these factors are

subject to the potentially endless

speculation of which NAS spoke in its

report. We do require DOE and NRC to

take climate change and probable

variations in geologic conditions into

32122 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

account because they are factors that

scientific study can reasonably bound.

5. Is it Reasonable To Consider, Select,

and Hold Constant Today’s Known and

Assumed Attributes of the Biosphere for

Use In Projecting Radiation-related

Effects Upon the Public of Releases

From the Yucca Mountain Disposal

System?

Comments/Our Responses. The

comments we received on this question

generally favored our position of

holding present biosphere conditions

constant for the purpose of making

performance projections for the disposal

system. Some comments pointed to the

unexpected dynamic population growth

in the southern Nevada area, or stated

that current conditions were not a

reliable means to predict future

conditions. Some comments also

pointed out that the target receptor for

dose assessments could not be defined

independently of assumptions about the

biosphere. The tenor of these comments

is a general agreement that unreasonably

speculative assumptions about

biosphere conditions are inappropriate

and should be avoided. We agree with

this general theme of not making

unreasonably speculative assumptions

about the future. The NAS also made

this point in its recommendations for a

reference biosphere. We made some

fundamental assumptions in this rule

about biosphere conditions to assure

that dose assessments for the RMEI are

cautious, but reasonable. For example,

we require that DOE assume that the

RMEI consumes 2 liters/day of drinking

water and that DOE base food

consumption patterns on surveys of the

current residents in the area

downgradient from Yucca Mountain.

We have left it to NRC to establish other

details of the biosphere dose assessment

calculations for Yucca Mountain, such

as details of pathway-specific dose

conversion factors and details necessary

for assessing all potential exposure

pathways. For additional discussion of

these issues, see section III.B.1.f above.

A related aspect of fixing biosphere

conditions for dose assessments is the

question of potential variations in

climate and geologic conditions because

these factors play an important part in

developing the ground water

contaminant concentrations that serve

as input for the biosphere dose

assessments. We specify that DOE

should vary climate and geologic

conditions over a reasonable range of

values based on an examination of

evidence in the geologic record for

conditions in the area. The evidence

preserved in the relatively recent

geologic record provides a means to

reasonably bound the range of possible

conditions.

6. In Determining the Location of the

RMEI, We Considered Three Geographic

Subareas and Their Associated

Characteristics. Are There Other

Reasonable Methods or Factors Which

We Could Use to Change the Conclusion

We Reached Regarding the Location of

the RMEI? For Example, Should We

Require an Assumption That for

Thousands of Years Into the Future

People Will Live Only in the Same

Locations That People do Today? Please

Include Your Rationale for Your

Suggestions

Comments/Our Responses. See

section III.B.1.d above for a further

discussion of this subject. The many

comments we received on this topic

suggested a variety of locations, some

closer and some farther than Lathrop

Wells. A few commenters thought that

the Lathrop Wells location is

appropriate. However, a number of

others stated that the location should be

at the repository footprint. One

commenter stated that the current

farming area in southern Amargosa

Valley would be a reasonable location

for the RMEI.

Based on further review of sitespecific information, we decided to

locate the RMEI in the accessible

environment above the highest

concentration of radionuclides in the

plume of contamination. The accessible

environment begins at the edge of the

controlled area, which may extend no

farther south than the southern

boundary of NTS (latitude 36° 40′

13.6661’’ North), which is

approximately 18 km south of the

repository (roughly 2 km closer than the

Lathrop Wells location we proposed).

We do not believe that an RMEI likely

would live much closer to the Yucca

Mountain repository because of the

increasing depth to ground water and

the increasing roughness of the terrain

(see Chapter 8 of the BID), although the

RMEI would still have rural-residential

characteristics described in § 197.21 if

the controlled area does not extend as

far south as the NTS boundary. In

addition, we believe that, at 18 km, a

rural resident likely will receive the

highest potential doses in the region

because, as we have defined the RMEI,

the potential dose at this location will

be from drinking water, as well as

through ingestion of food grown with

contaminated ground water. With the

RMEI eating food grown using

contaminated water, the rural resident

at 18 km will have a higher dose than

an individual would have living much

closer than 18 km because the cost of

water likely would preclude a garden

and likely would allow only drinking

the water and domestic uses (see

Chapter 8 of the BID). Likewise, we do

not think that hypothesizing that the

RMEI lives 30 km away is a cautious or

reasonable assumption because: (1) At

30 km, the RMEI likely would use water

in which contaminants would be much

more diluted; (2) the downgradient

residents closest to Yucca Mountain are

currently near Lathrop Wells; and (3)

Nye County projects short-term (20

years) growth between U.S. Route 95

and the southern boundary of NTS;

therefore, population there is not an

ephemeral phenomenon. Therefore,

placing the RMEI at about 18 km from

the repository footprint reflects the

location of existing residents, is

reasonably conservative, and provides

more protection of public health,

relative to one commenter’s suggested

location of 30 km.

There were a few other comments

related to the location of the RMEI. For

example, one comment suggested that,

in selecting the location, we should

consider the geology and hydrology of

the site rather than choosing the

location in advance. Another comment

stated that we should base the location

of the RMEI on the ability of the RMEI

to sustain itself consistent with

topography and soil conditions. This

comment also stated that depth to

ground water should not be a factor

because it is impossible to predict either

human activities or economic

imperatives.

We determined the point of

compliance for the individualprotection standard using site-specific

factors and NAS’s recommendation to

use current conditions (NAS Report p.

54). In preparing to propose a location

for the RMEI, we collected and

evaluated information on the natural

geologic and hydrologic features such as

topography, geologic structure, aquifer

depth, aquifer quality, and the quantity

of ground water, that may preclude

drilling for water at a specific location

(see Chapters 7 and 8, and Appendices

IV and VI, of the BID). We also

considered geologic conditions, for

example, we do not believe that a ruralresidential individual would occupy

areas much closer to Yucca Mountain

because of the increasing rough terrain

and the increasing depth to ground

water (see Chapter 8 of the BID). With

increasing depth to ground water come

higher costs: (1) To explore for water; (2)

to drill for water; and (3) to pump the

water to the surface (see Appendix IV of

the BID). Our final standard requires

DOE and NRC to consider other, more

appropriate locations based upon

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32123

potential, future site characterization

data. We agree that it is impossible to

predict either human activities or

economic imperatives. Therefore, we

followed NAS’s recommendation to use

current conditions. This approach

allows us to avoid forcing the use of

potentially excessive speculative

assumptions as the bases of regulatory

decisionmaking. It also leads us to

consider the depth to ground water as

a key factor in determining the location

and activities of the RMEI and the

current location of people living

downgradient from the repository as a

reflection of this key factor. We note

that some wells providing drinking

water are located less than 18 km from

the repository footprint; however, those

wells have been installed by the Federal

government to serve the needs of NTS,

and we do not consider them typical of

wells that would serve, or be installed

by, a rural-residential RMEI. See

Chapter 8 (Table 8–5) of the BID.

Finally, one comment stated that the

proposed RMEI concept forces DOE to

assume the RMEI will withdraw water

from the highest concentration within

the plume without consideration of the

likelihood. According to this comment,

forcing such an assumption neglects the

low probability that a well will intersect

the highest concentration within the

plume.

This comment’s approach, which

would utilize a probabilistic method to

determine the radionuclide

concentration withdrawn by the RMEI,

is similar to one of the example critical

group approaches that NAS provided in

its report (NAS Report, Appendix C).

The NAS’s approach would use

statistical sampling of various

parameters, i.e., considering the

likelihood (probability) of various

conditions existing, to arrive at a dose

for comparison to the standard.

However, we did not use this CG

approach for the following reasons: (1)

There is no relevant experience in

applying the probabilistic CG approach,

(2) the probabilistic CG approach is very

complex and is difficult to implement in

a manner that assures it would meet the

requirements of defining a CG (i.e., a

small group of people who are

homogeneous in regards to exposure

characteristics, including receiving the

highest doses among the general

population), and (3) we are concerned

that this approach does not appear to

identify clearly which individual

characteristics describe who is being

protected. A probabilistic approach for

CG dose assessment could include

members that would receive little or no

exposure and members that would

receive much higher exposures. An

RMEI is a more conservative approach,

based upon site-specific conditions,

because the RMEI serves to represent

those individuals in the community

who would receive the highest doses,

based on cautious, but reasonable,

assumptions. Finally, a significant

majority of the comments on the NAS

Report opposed the use of the

probabilistic CG approach. We further

believe that prudent public health

policy requires that our approach be

followed to provide reasonable

conservatism. To allow the probability

of any particular location being

contaminated is not a prudent approach

to the ultimate goal of testing acceptable

performance.

7. The NAS Suggested Using an NIR

Level to Dismiss From Consideration

Extremely Low, Incremental Levels of

Dose to Individuals When Considering

Protection of the General Public. For

Somewhat Different Reasons, We are

Proposing To Rely Upon the IndividualProtection Standard To Address

Protection of the General Population. Is

This Approach Reasonable in the Case

of Yucca Mountain? If Not, What is an

Alternative, Implementable Method To

Address Collective Dose and the

Protection of the General Population?

Comments/Our Responses. A number

of commenters agreed with us that the

general population is protected by the

individual-protection standard in the

site-specific case of Yucca Mountain.

Nearly all commenters agreed with our

position that a collective-dose limit is

unnecessary, again, in the site-specific

case of Yucca Mountain. Some

commenters stated that EPA should not

use an NIR level. One commenter stated

that we should not suggest that DOE use

a collective-dose estimate in the

consideration of design alternatives. We

decided not to include a collective-dose

limit (see section III.B.1.e), and are not

recommending that DOE estimate

collective doses.

Regarding the NIR, we decline to set

such a level. We agree with NAS’s

conclusion that ‘‘ * * * an individual

risk standard [will] protect the public

health, given the particular

characteristics of the site * * *’’ (NAS

Report p. 7). However, we do not accept

the remainder of that statement: ‘‘ ***

provided that policy makers and the

public are prepared to accept that very

low radiation doses pose a negligibly

small risk’’ (NAS Report p. 7). We do

not agree that collective doses made up

of very small individual doses are

necessarily negligible. We base our

decision on the site-specific

characteristics of Yucca Mountain and

the levels of individual risk that we

previously have used. See the preamble

to the proposed rule (64 FR 46991) for

the full discussion of our reasoning. We

summarize this discussion immediately

below.

The NAS based its recommendations

upon guidance from NCRP in which

NCRP proposed a ‘‘Negligible

Incremental Dose’’ level of 1 mrem/yr.

Dose levels below 1 mrem/yr would be

considered ‘‘negligible’’ for any source

or practice (see the NAS Report pp. 59–

61 and NCRP Report No. 116, p. 52,

Docket No. A–95–12, Item II–A–7). The

IAEA has made similar

recommendations to define an ‘‘exempt

practice’’ (see IAEA Safety Series No.

89, p. 10, Docket No. A–95–12, Item II–

A–6). However, it is not clear to us that

an exemption for whole sources or

practices, such as waste disposal in

general, should apply to such specific

situations such as gaseous releases from

a particular repository because gaseous

releases comprise only one category of

releases from a repository; other releases

are projected via the ground water

pathway. In addition, we believe that it

is inappropriate to avoid calculating a

radiation dose merely because it is small

on an individual basis (NCRP Report

No. 121, p. 62, Docket No. A–95–12,

Item II–A–8). Finally, we do not believe

that it is appropriate to apply the NIR

concept to population doses (NCRP

Report No. 121, p. 62, Docket A–95–12,

Item II–A–8). In its Report No. 121,

NCRP stated: ‘‘[a] concept such as the

NID (Negligible Incremental Dose)

* * * is not necessarily a legitimate cutoff dose level for the calculation of

collective dose. Collective dose

addresses societal risk while the NID

and related concepts address individual

risk’’ (NCRP Report No. 121, p. 62,

Docket No. A–95–12, Item II–A–8).

Despite our belief that it is

inappropriate to set an NID level, we

acknowledge that the extremely low

levels of individual risk from the doses

that NAS cited (NAS Report p. 59) (i.e.,

0.0003 millirem/yr, for airborne

releases) are well below those levels that

we have used for other regulations.

In addition, the standards in 40 CFR

part 191 provide both release limits,

which act as a form of collective dose

protection, and individual-protection

limits. The release limits act to restrict

the potential of dilution being used by

disposal system designers to meet the

individual-protection limit. However,

the potential for large-scale dispersal of

radionuclides through ground water and

into surface water does not exist at

Yucca Mountain.

Therefore, for the reasons enumerated

above, we believe that we do not need

to include a general populationVerDate 11<MAY>2000 14:19 Jun 12, 2001 Jkt 194001 PO 00000 Frm 00051 Fmt 4701 Sfmt 4700 E:\FR\FM\13JNR2.SGM pfrm07 PsN: 13JNR2
32124 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

protection provision in our Yucca

Mountain standards. See the Response

to Comments document for a fuller

discussion of our responses to

comments we received on these issues.

8. Is Our Rationale for the Period of

Compliance Reasonable in Light of the

NAS Recommendations?

Comments/Our Responses. Public

comments supported a compliance

period that ranged from 10,000 years to

a million years and beyond (i.e., no time

limitation). Most of the comments

supporting the 10,000-year period were

concerned that such a period was the

longest time over which it would be

possible to obtain meaningful modeling

results. Comments noted that just

because performance assessment models

may be set to run dose calculations to

times well in excess of 10,000 years

does not necessarily mean that at this

time the level of confidence in the

reliability of these calculations remains

the same. Other comments noted that

because of the unprecedented nature of

compliance periods exceeding 10,000

years, the greater uncertainties at such

times only serves to complicate the

licensing process without providing a

clearly identifiable increased benefit to

public health. A few commenters

suggested that because there will likely

be radiation doses incurred by

individuals beyond 10,000 years, DOE

should calculate peak dose, within the

time period of geologic stability, and

include these doses in the Yucca

Mountain Environmental Impact

Statement. These comments essentially

supported the rationale upon which we

based our final rule.

On the other hand, numerous

comments suggested that a compliance

period of 10,000 years is not reasonable.

They urged us to extend the compliance

period beyond 10,000 years for a variety

of reasons. Foremost among these

reasons is that NAS suggested a

compliance period that would extend to

the time of peak dose or risk, within the

period of geologic stability for Yucca

Mountain, which it estimated could be

as long as one million years. The NAS

based its recommendations on scientific

considerations. The NAS concluded that

it is possible to assess the performance

of the repository over times during

which the geologic system is ‘‘relatively

stable’’ or varies in a ‘‘boundable

manner’’ (NAS Report p. 9). It also

noted that policy considerations could

act to shorten this period. Other

comments suggested that the

compliance period of the standard

should be comparable to the hazardous

lifetime of the materials to be emplaced

in the Yucca Mountain repository.

It is unclear whether an assessment of

the disposal system based on NAS’s

recommendation for a standard that

would apply to time of peak dose within

the period of geologic stability (about

one million years) would be meaningful

given the expected rigor of a licensing

process. As discussed above in section

III.B.1.g, we believe that the substantial

uncertainty in projecting human

radiation exposures over extremely long

time periods, such as a million years, is

unacceptable. For example, analyzing

long-term natural changes would

require unprecedented performance

assessment modeling of numerous and

different climate regimes including

several glacial-interglacial cycles. This

situation could require the specification

of exposure scenarios based on arbitrary

assumptions rather than ‘‘cautious, but

reasonable’’ assumptions rooted in

present-day knowledge. In fact, NAS

indicated it knew of no scientific basis

for identifying such scenarios (NAS

Report p. 96). Another concern relates to

the possible biosphere conditions and

human behavior. Even for a period as

‘‘short’’ as 10,000 years, it is necessary

to make certain assumptions. For

periods on the order of one million

years, even natural human evolutionary

changes become a consideration.

Regulating to such long time periods

could become arbitrary. Moreover, NAS

based its time-frame recommendation

on scientific considerations; however, it

recognized that such a decision also has

policy aspects (NAS Report p 56). The

NAS recognized that the existence of

these policy aspects might lead us to

select an alternative more consistent

with previous Agency policy. Indeed,

we considered the longest practical

regulatory periods associated with other

Agency programs, as well as 40 CFR

part 191. We believe the unprecedented

nature of a compliance period beyond

10,000 years argues against imposing

such a long regulatory period here. Also,

numerous international disposal

programs use a 10,000-year compliance

period. Many of these same programs

have committed to consider more

qualitative evaluations beyond 10,000

years. (See GAO/RCED–94–172, 1994,

Docket No. A–95–12, Item V–A–7.

Chapter 3 of the BID also contains

information on international programs.)

Of course, as knowledge and technical

capabilities grow, this situation could

change over time.

The hazardous lifetime of radioactive

waste is important; however, it is but

one of several factors that a regulator

must consider in projecting the

potential risks from disposal. Indeed,

some of the radionuclides expected to

be in the waste inventory at Yucca

Mountain have half-lives extending to

thousands or hundreds of thousands of

years (and even a million years or more

in a few cases). The ability of the

repository to isolate such long-lived

materials relates to the retardation

characteristics of the whole

hydrogeological system within and

outside the repository, the effectiveness

of engineered barriers, the

characteristics and lifestyles associated

with the potentially affected population,

and numerous other factors in addition

to the hazardous lifetime of the

materials to be disposed.

With respect to uncertainty in the

projected peak dose, one commenter

suggested that NRC should deny the

license application if modeling results

show an uncertainty range of five orders

of magnitude above the dose limit in our

individual-protection standard.

Modeling results, and their associated

uncertainties, are but a part of the

complete record on which NRC will

determine whether the disposal system

complies with 40 CFR part 197. For the

reasons cited above, we consider a

10,000-year compliance period, and the

additional requirement that DOE

calculate the peak dose beyond 10,000

years and include this assessment in the

Yucca Mountain Environmental Impact

Statement, to be the most appropriate

approach, given the state of technology

and knowledge today. In addition, we

require DOE to provide a ‘‘reasonable

expectation’’ that disposal system

performance will meet the standard.

Calculation of doses to the RMEI

involves projecting doses that are within

a reasonably expected range rather than

projecting the most extreme case. This

approach is in concert with NAS’s

recommendations to use ‘‘cautious, but

reasonable’’ assumptions to define who

is to be protected (NAS Report pp. 5–

6). The degree of uncertainty in the dose

assessments considered acceptable in

the licensing process is, in our opinion,

an implementation decision that should

be the responsibility of NRC. We believe

that we have provided sufficient detail

in the standard to provide the context

needed to assure the standard is applied

as we intend (see, e.g., our discussions

of ‘‘reasonable expectation’’ in section

III.B.2.c and in the Response to

Comments Document that accompanies

this rule); however, the final decision

regarding the acceptable degree of

uncertainty is NRC’s responsibility.

For a variety of technical and policy

reasons, we believe that a 10,000-year

compliance period is meaningful,

protective, practical to implement, and

will result in a robust disposal system

protective for periods beyond 10,000

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32125

years. In other programs we have

regulated non-radioactive hazardous

waste for as long as 10,000 years.

Having a 10,000-year compliance period

for Yucca Mountain, in conjunction

with 40 CFR part 191, ensures that SNF,

HLW, and TRU radioactive wastes

disposed anywhere in the United States

must be regulated for a 10,000-year

compliance period.

9. Does Our Requirement That DOE and

NRC Determine Compliance with

§ 197.20 Based Upon the Mean of the

Distribution of the Highest Doses

Resulting From the Performance

Assessment Adequately Address

Uncertainties Associated With

Performance Assessments?

Comments/Our Responses. Comments

on this question ranged from advocating

that we should use the maximally

exposed individual and ‘‘worst-case’’

measures to expressing general

agreement with the proposed approach.

Some comments stated that any measure

applied to the performance assessments

should be considered an

implementation decision that we should

leave to NRC. See the Response to

Comments document for additional

discussion of comments we received

regarding performance assessments.

We specify a compliance measure we

believe is reasonable but still

conservative: the mean of the

distribution of projected doses from

DOE’s performance assessments. The

primary reason we impose this

requirement is that it provides a

necessary context for implementation of

the standard. In addition, we note that

it is also consistent with the approach

we implemented in certifying WIPP.

We consider it necessary to supply

context for understanding the intent of

the standard to constrain and direct the

otherwise unbounded range of

approaches to demonstrating

compliance that could be justified in the

absence of such context. For example, it

would be possible to use only a small

number of assessments to demonstrate

compliance if the standard specified

only an exposure limit. In such a case,

the full range of relevant site conditions

and processes might not be considered.

Further, the analyses and the regulatory

decision making might not capture the

uncertainties in projecting long-term

performance. At the other extreme,

without a defined performance measure,

endless and exhaustive site

characterization studies and analyses

could be required. The impetus for these

endless and exhaustive studies and

analyses would be a perceived need to

identify the most extreme ‘‘worst-case’’

scenarios (regardless of their actual

likelihood of occurring). We believe that

a thorough assessment of repository

performance expectations should

examine the full range of reasonably

foreseeable site conditions and relevant

processes expected during the

regulatory time frame. In making

quantitative estimates of repository

performance, we believe that unrealistic

or extreme situations or assumptions

should not dominate estimates of

expected performance (see additional

discussions about ‘‘reasonable

expectation’’ in this preamble and the

Response to Comments Document).

With these considerations in mind, we

believe that specifying a performance

measure is necessary to supply the

proper context for implementing the

standard in the regulatory process, as

well as providing the applicant (DOE) a

focus for its efforts to build the

compliance arguments and supporting

calculations.

In line with our use of the term

‘‘reasonable expectation,’’ the

fundamental compliance measure

consistent with a literal mathematical

interpretation of this term would be the

mean value of the distribution of

calculated doses. However, as the only

alternative for a compliance measure,

the mean may in some cases be

interpreted too restrictively. In actuality,

some situations may result in very high

dose estimates for situations that have

low probabilities. Simply averaging

these ‘‘outliers’’ into the distribution of

calculated dose estimates can bias the

mean levels that may be unrealistically

high. Although this is certainly a

conservative (and therefore desirable)

approach, its effects can be

unrealistically conservative (not a

desirable situation). The result of overly

conservative effects is to drive

regulatory decision making on the basis

of very low probability and potentially

unrealistic situations.

Because of these potential situations,

we also proposed using the median of

the expected range of calculated values

as another interpretation of the

‘‘expected’’ situation. The median

(reflecting a value exceeded half of the

time) may be more conservative if some

of the variables involved in the

performance calculations have skewed

distributions. However, we conclude

that, in the case of Yucca Mountain, the

mean is an appropriate measure.

By specifying the mean as the

performance measure and probability

limits for the processes and events to be

considered (§ 197.36), and in concert

with the intent of our ‘‘reasonable

expectation’’ approach in general, we

have implied that probabilistic

approaches for the disposal system

performance assessments are expected.

The probabilistic approach is well

established in DOE’s approach to

performance projections (see the DEIS

and Vol. 3 of the Viability Assessment,

Docket No. A–95–12, Items V–A–4 and

V–A–5). Based on DOE’s past actions

and stated intent, we believe that DOE

will continue to follow this approach

and that, therefore, it is unnecessary for

us to specify additional requirements in

the standard to assure that DOE

continues to follow this approach. We

also believe that specifying such

requirements could be interpreted to

exclude the use of deterministic

analyses. These analyses can be useful

for carefully focused bounding analyses

and sensitivity studies. For these

reasons we have specified only the

fundamental performance measures to

provide the context for understanding,

without additional qualifications, the

intent of the standard for

implementation efforts.

A number of comments stated that,

though they agreed with our selection of

performance measures, the choice

should be left as an implementation

detail for NRC. Relative to the

implementation question, we believe

that specifying the fundamental

compliance measure is necessary as a

means to supply the proper context for

understanding the intent of the rule and

for implementation guidance as

explained above. We feel this is

distinctly different than the

implementation responsibility of NRC,

as explained below.

We do not believe that setting the

fundamental compliance measure

intrudes into NRC’s implementation

authority because the primary task for

the regulatory authority is to examine

the performance case put forward by

DOE to determine ‘‘how much is

enough’’ in terms of the information and

analyses presented (i.e., how will the

regulatory authority determine when the

performance case has been

demonstrated with an acceptable level

of confidence). Our standard contains

no specific measures for that judgment.

We do not specify any confidence

measures for such judgments or

numerical analyses. Also, we do not

prescribe analytical methods that must

be used for performance assessments,

quality assurance measures that must be

applied, statistical measures that define

the number or complexity of analyses

that should be performed, or any

assurance measures in addition to the

numerical limits in the standard. We

specify only that the mean of the dose

assessments must meet the exposure

limit. There are many other

considerations and decisions that

32126 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

describe the extent of the assessments or

level of rigor necessary to ensure that

the mean is a meaningful measure upon

which a licensing decision can rest.

These considerations and decisions

properly belong to the implementing

authority. For example, we believe

setting a confidence level clearly is an

implementation function that should be

left to NRC; therefore, we make no

requirements in the standard to

foreclose NRC’s flexibility in setting

appropriate confidence measures. In the

development of the WIPP certification

criteria, where we had both the

standard-setting and implementing

authority, we did establish a confidence

measure (40 CFR 194.55 (d) and (f)) in

addition to the basic performance

measure. We also included

implementation requirements in the

WIPP certification criteria, including

analytical approaches (§ 194.55(b)),

quality assurance requirements

(§ 194.22), other assurance requirements

(§ 194.41), requirements for modeling

techniques and assumptions (§§ 194.23

and 194.25), and use of peer review and

expert judgment (§§ 194.26 and 194.27).

These requirements go well beyond the

simple statement of a compliance

measure. We did not incorporate a

similar level of detail in the Yucca

Mountain standards because we believe

we must specify only what is necessary

to provide the context for

implementation that NRC will execute.

We therefore agree with comments that

support our choice of the performance

measure, but disagree for the reasons

described above that this choice is an

intrusion into the implementation

responsibilities of NRC.

For the WIPP certification, the

compliance measure selected for the

individual-protection standard was the

higher of the mean or median of the

calculated distributions of doses from

releases (40 CFR 194.55(f)). The mean or

median are reasonably conservative

measures because they are influenced

by high exposure estimates found when

analyzing the full range of site

conditions and relevant processes,

without being geared to exclusively

reflect high-end results, as would be the

case if we selected as the measure a

high-end percentile of the calculated

dose distribution (such as the 95th or

99th percentile). Our final rule for

Yucca Mountain specifies only that the

mean be used, as we believe that it is

appropriately conservative in this

situation.

10. Is the Single-borehole Scenario a

Reasonable Approach To Judge the

Resilience of the Yucca Mountain

Disposal System Following Human

Intrusion? Are There Other Reasonable

Scenarios Which We Should Consider,

for Example, Using the Probability of

Drilling Through a Waste Package Based

Upon the Area of the Package Versus

the Area of the Repository Footprint or

Drilling Through an Emplacement Drift

but not Through a Waste Package? Why

Would Your Suggested Scenario(s) be a

Better Measure of the Resilience of the

Yucca Mountain Disposal System than

the Proposed Scenario?

Comments/Our Responses. Comments

upon this question varied from

agreement that the proposed intrusion

scenario is an adequate test of repository

resiliency to opinions that the analysis

of any human-intrusion scenario would

be irrelevant to the Yucca Mountain

setting. Some comments proposed

alternative intrusion scenarios, most

commonly the use of multiple drilling

intrusions. Some comments also

proposed alternative ways of treating

the intrusion scenario relative to

repository requirements. We also

received comments concerning other

aspects of the intrusion scenario as well

as in response to the specific questions

asked above. Discussion on all the

issues raised in comments about the

human-intrusion scenario appears in the

Response to Comments document.

Comments in favor of the intrusion

scenario as we framed it in the proposed

rule focused upon the difficulties in

defending any predictions about the

probability of drilling intrusions

through the repository and in reliably

predicting a hypothetical drilling

intrusion in any detail. These comments

echoed NAS’s conclusions about the

reliability of post-closure institutional

controls to prevent intrusion, and the

inability to make scientifically

supportable predictions of the

probability of human-intrusion events

over the regulatory period (NAS Report

pp. 104–109). The NAS reasoned that

because it is not possible to reliably

eliminate the potential for human

intrusion, the only reasonable approach

would be to assume an intrusion occurs

and assess the consequences on disposal

system performance. In this light, NAS

recommended that a simple stylized

drilling intrusion through the repository

to the underlying ground water table be

assessed as a test of the resiliency of the

disposal system (NAS Report Chap. 4).

Because it is impossible to scientifically

exclude the potential for an intrusion,

and because proposing the nature of an

intrusion is at best speculative, these

comments agreed that the stylized

approach that assumes an intrusion and

assesses the consequences is

appropriate. We have followed the

NAS’s recommendations closely in

framing the human intrusion standard.

Some comments on the framing of the

intrusion scenario proposed that, for

various reasons, multiple intrusions

should be considered, rather than

simply assuming one borehole

penetration through the repository.

Because of certain site-specific

considerations with respect to Yucca

Mountain, and in light of the rationale

underlying the NAS recommendations,

it is not appropriate to modify the

scenario to include multiple

penetrations through the repository. It is

impossible to accurately predict the

potential for intrusion in the distant

future. Therefore, postulating multiple

intrusions is just as speculative as

postulating a single intrusion at any

given time or specific location over the

repository. For this reason, NAS

recommended that we develop a

stylized intrusion in our rulemaking

(NAS Report p. 111). We agree with this

recommendation because disruption of

the engineered and natural barriers is a

means through which radionuclides can

escape the repository and be transported

to the accessible environment where

exposures of individuals can result.

Therefore, an evaluation of humanintrusion consequences is appropriate

for a repository standard. The NAS also

recommended that we define a typical

intrusion scenario for analysis (NAS

Report p. 108) and recommended a

stylized approach to framing the

scenario (NAS Report p. 111) and a

consequence analysis of the scenario

(NAS Report p. 111). The intent of this

approach is that the disposal system

should be resilient ‘‘to at least moderate

inadvertent intrusions’’ (NAS Report p.

113). Scenarios ranging from single

penetrations to many penetrations

through the repository over the

regulatory time period would give a

very wide range of results—none more

or less defensible than any other,

making their use in regulatory decision

making ambiguous at best. To avoid the

speculative aspects of defining intrusion

scenarios, we believe the stylized single

intrusion recommended by NAS is

sufficient and would provide a suitable

test of the Yucca Mountain disposal

system’s performance.

Related comments offered opinions

that the prospect of drilling for water

resources at the top of Yucca Mountain

is not a credible scenario because

drilling for water would be more

sensible in the adjacent valleys. These

comments, however, did not offer

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32127

alternatives for the drilling intrusion.

Rather, they stated or implied that the

intrusion scenario was unnecessary. We

agree that drilling for water, or any other

mineral resources at Yucca Mountain, is

unlikely because of the very limited

resource potential at the site (see

Chapter 8 of the BID). However, as NAS

concluded, it is impossible to totally

eliminate the possibility of intrusion

(see Chapter 4 of the NAS Report). This

question again goes back to the

difficulty in making defensible

predictions about the probability of

human activities over very long time

periods and the fact that intrusion is a

means through which releases, and

consequent exposures, can occur.

Therefore, it is necessary to consider the

consequences of inadvertent intrusions

in a health-based standard. Some

comments suggested that there is a

strong possibility for deliberate

intrusion into the repository to access

its contents as possible resources. We

believe that there is no useful purpose

to assessing the consequences of

deliberate intrusions because in that

case the intruders would be aware of the

risks and consequences and would have

decided to assume the risks. This is

consistent with NAS’s conclusion

regarding intentional intrusion (NAS

Report p. 114).

Some comments stated that defining

the stylized scenario as we did

effectively makes the human-intrusion

dose assessment results into design

constraints for the repository. We do not

believe the stylized scenario imposes

any design constraints because the

waste package penetration is assumed to

occur regardless of the particular design

chosen for the waste package. Here

again, none of these comments proposed

alternative scenarios. Rather, they

simply questioned the basic relevance of

a human intrusion standard. For the

reasons mentioned previously, however,

we reiterate our belief that an analysis

of human-intrusion is necessary, and we

also note that NAS (NAS Report p. 108)

stated that ‘‘EPA should specify in its

standard a typical intrusion scenario...’’.

We do not believe it should be regarded

as a design constraint unless the results

of the consequence analyses indicate

that the limited breaching of the natural

and engineered barriers would result in

the standard being exceeded. Even

though the probability of drilling

intrusions may be low, it is impossible

to unequivocally eliminate them.

Therefore, we agree with NAS’s

conclusion that the ‘‘repository should

be resilient to at least modest

inadvertent intrusions’’ (NAS Report p.

113).

11. Is it Reasonable To Expect That the

Risks to Future Generations Be No

Greater Than the Risks Judged

Acceptable Today?

Comments/Our Responses. Comments

we received upon this question strongly

favored the position that we should not

allow greater risks for future generations

than what is judged to be acceptable

today. Some comments speculated that

with advances in medical technology

and other areas, the risks assessed today

most likely would be less in the future

because society would be more effective

in mitigating the effects of radiation

exposures. Some comments advised that

risks from the disposal effort should be

reviewed periodically so that decisions

could be made about their acceptability

at a future date. We believe we have set

the standards conservatively, but

reasonably, and consistent with our

policies for radiation exposure from

radioactive waste disposal applications

and NAS’s recommendations. In this

regard, our standards apply over the

entire regulatory period of 10,000 years.

Our standards thus protect future

generations for a very significant time

period. In addition, we require DOE to

calculate the peak dose to the RMEI

beyond 10,000 years. Although our

standards do not apply to the results of

this calculation, this post-10,000-year

analysis will provide more complete

information regarding disposal system

performance beyond 10,000 years. This

approach to the post-10,000-year period

is consistent with our understanding of

the limits imposed by inherent

uncertainties in making such long-term

performance projections. The question

of periodic re-evaluation of repository

performance is an implementation

question that should be left to the

discretion of NRC.

12. What Approach Is Appropriate for

Modeling the Ground Water Flow

System Downgradient From Yucca

Mountain at the Scale (Many Kilometers

to Tens of Kilometers) Necessary for

Dose Assessments Given the Inherent

Limitations of Characterizing the Area?

Is it Reasonable To Assume That There

Will be Some Degree of Mixing With

Uncontaminated Ground Water Along

the Radionuclide Travel Paths From the

Repository?

Comments/Our Responses. Comments

on this question shared a general theme

that we should not be prescriptive in

indicating a preference or requirement

for any specific modeling approach that

should be used. Rather, the bulk of the

comments suggested that DOE (the

organization responsible for developing

the license application) and NRC (the

authority responsible for the approval of

the disposal facility) should make these

decisions. We agree with this general

theme; therefore, our rule does not

specify that DOE must use a particular

modeling approach to demonstrate

compliance with the standards. We

believe that DOE and NRC should avoid

extreme assumptions and approaches

and should identify and consider the

inherent uncertainties in projecting

performance in the regulatory process.

More specifically for Yucca Mountain,

we believe that it is necessary to avoid

extreme modeling approaches. One

example of an extreme modeling

approach is assuming the transportation

of releases from the repository through

the natural barriers without mixing with

other ground waters. In this regard we

retained our recommendation that

‘‘reasonable expectation’’ be the

standard used to assess repository

performance. We have provided detail

in the standards only to the extent

needed to provide the context necessary

to assure that the components of the

standards are implemented in the

manner we intended when we

developed the standards. Ultimately, it

is NRC’s task to select and apply the

appropriate measure to determine

compliance with our standards.

13. Which Approach for Protecting

Ground Water in the Vicinity of Yucca

Mountain is the Most Reasonable? Is

There Another Approach Which Would

be Preferable and Reasonably

Implementable? If so, Please Explain the

Approach, Why It Is Preferable, and

How It Could Be Implemented

Comments/Our Responses. We

received public comments advising us

of a variety of approaches towards

protecting ground water in the vicinity

of Yucca Mountain. Two primary

approaches emerged. One group of

public comments suggested that an allpathways, individual-dose standard,

with no separate or specific ground

water protection provisions, would be

fully protective of the public health. On

the other hand, a second set of public

comments suggested that we should

promulgate separate ground-water

protection standards applicable to the

Yucca Mountain disposal system. The

final rule reflects the latter approach.

We believe as a matter of prudent

policy that ground water protection

standards are neither redundant nor

unnecessary because they address

specific aspects of natural resource

protection not covered by the

individual-protection standard. Rather,

such standards are complementary to

the public health and safety standards

applicable to the Yucca Mountain

32128 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

disposal system. In particular, we

consider ground water that is, or that

could be, drinking water to be the most

valuable ground water resource. We

believe that it deserves the highest level

of protection. At Yucca Mountain, water

from the aquifer beneath the proposed

repository currently serves as a source

of drinking water in communities 20 to

30 km south of Yucca Mountain. This

aquifer has the potential to supply

drinking water to a substantially larger

population than that presently in the

area (NAS Report p. 92).

Over the years, many of our regulatory

programs have incorporated the MCLs

as an important part of our regulations

related to both radioactive and nonradioactive wastes. This approach grew

out of the development and

implementation of our ground water

protection strategy, ‘‘Protecting the

Nation’s Ground-Water: EPA’s Strategy

for the 1990s’’ (‘‘the Strategy,’’ Docket

No. A–95–12, Item II-A–3). The use of

ground water protection requirements,

including the use of MCLs, is reflected

in our regulations pertaining to

hazardous waste disposal (40 CFR part

264), municipal waste disposal (40 CFR

parts 257 and 258), underground

injection control (UIC) (40 CFR parts

144, 146, and 148), and uranium mill

tailings disposal (40 CFR part 192). We

also have incorporated the MCLs into

our generally applicable standards for

the disposal of SNF, HLW, and TRU

radioactive waste (40 CFR part 191).

These generic regulations apply to the

land disposal of these materials

everywhere in the United States except

at Yucca Mountain. Extending

comparable ground-water protection

standards to the proposed Yucca

Mountain disposal system will assure

reasonable and similar protections

wherever the disposal of SNF, HLW, or

TRU radioactive waste occurs in this

country.

In our response to Question 15, we

note our concerns related to adopting

only an all-pathways individualprotection standard with no specific

ground-water protection provisions. For

a more detailed discussion of the issues

associated with these two options (allpathways with and without separate

ground water protection), please see the

Response to Comments document.

14. Is the 10,000-year Compliance

Period for Protecting the RMEI and

Ground Water Reasonable or Should we

Extend the Period to the Time of Peak

Dose? If We Extend it, How Could NRC

Reasonably Implement the Standards

While Recognizing the Nature of the

Uncertainties Involved in Projecting the

Performance of the Disposal System

Over Potentially Extremely Long

Periods?

Comments/Our Responses. As

discussed in the response to Question 8

above, comments both supported and

questioned our compliance period for

the RMEI and ground water protection

standards. Commenters who supported

the 10,000-year compliance period

thought that this time period was

‘‘sufficient’’ and that it represented an

appropriate balance between long-term

coverage and implementability. These

commenters agreed with us that, though

it is possible to make longer-term

calculations, such calculations should

be used only for regulatory insight

because of the considerable uncertainty

involved in making the calculations.

These comments support our rationale

and choice of a 10,000-year compliance

period for protecting the RMEI and

ground water.

Numerous commenters suggested that

we should extend the compliance

period beyond 10,000 years for a variety

of reasons. Foremost is that NAS

suggested a compliance period

extending up to the time of peak dose

or risk, within the period of geologic

stability for Yucca Mountain (i.e., up to

one million years). Other commenters

suggested that the compliance period

should be comparable to the hazardous

lifetime of the materials to be emplaced

in the Yucca Mountain repository. As

indicated in our response to Question 8

above and in section III.B.1.g, we have

significant concerns relating to making

meaningful projections of repository

performance over the time periods

implied by NAS’s recommendations.

These concerns extend to modeling the

time to peak concentration to judge

compliance with the ground water

standards, which NAS did not explicitly

consider. Modeling of exposure

scenarios and climatic conditions very

different from those experienced over

the last 10,000 years, coupled with the

potential for human evolutionary

changes over such extended time

frames, introduces tremendous

uncertainties. This situation may result

in making arbitrary assumptions in

performance assessment modeling,

rather than making informed choices

based upon cautious, but reasonable,

assumptions rooted in present-day

knowledge. Regarding the hazardous

lifetime of the materials to be emplaced

in the Yucca Mountain repository, it is

true that there will be radioactive

materials remaining after the end of the

10,000-year regulatory period.

Nevertheless, the ability of a repository

to isolate such long-lived radionuclides

depends upon a variety of other factors,

including the retardation characteristics

of the whole hydrogeological system

within and outside of the repository, the

effectiveness of the engineered barriers,

the characteristics and lifestyles

associated with the potentially affected

population, as well as the hazardous

lifetime of the materials to be emplaced

in the repository.

Although we received numerous

comments suggesting that 10,000 years

was insufficient as a compliance period,

we received little in the way of

suggestions regarding on how to

reasonably implement standards

covering these potentially very extended

time periods. For example, one

commenter suggested that we put the

burden on NRC and DOE to develop

methods to estimate, with some degree

of certainty, the effects after 10,000

years without explaining how the

agencies could achieve these results.

Please note that NAS specifically

addressed this matter (NAS Report, pp.

12–13):

‘‘It might be possible that some of the

current gaps in scientific knowledge and

uncertainties that we have identified might

be reduced by future research * * *.

Conducting such an appraisal, however,

should not be seen as a reason to slow down

ongoing research and development programs,

including geologic site characterization, or

the process of establishing a standard to

protect public health.’’

We agree with NAS’s conclusion. We

expect more information will be

developed in the time between the

promulgation of this rule and the NRC

licensing decision to address some of

the remaining uncertainties.

15. As Noted by NAS, Some Countries

Have Individual-Protection Limits

Higher Than We Have Proposed. In

Addition, Other Federal Authorities

Have suggested Higher Individual-dose

Iimits With No Separate Protection of

Ground Water. Therefore, We Request

Comment Upon the Use of an Annual

CEDE of 250 μSv (25 mrem) With No

Separate Ground Water Protection,

Including the Consistency of Such a

Limit With Our Ground Water

Protection Policy

Comments/Our Responses. Our

promulgation of only an all-pathways,

individual-protection standard, such as

25 mrem/yr, with no ground-water

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32129

protection provisions, would provide no

assurance that ground water resources

will be protected adequately. The

separate ground water protection

standards in our rule will preserve the

integrity of the ground-water resources

in the vicinity of Yucca Mountain for

present and future generations.

The all-pathways, individualprotection standard is the primary

mechanism to protect public health

from releases of radioactivity from the

Yucca Mountain repository. We believe

that an all-pathways limit,

supplemented with ground water

protection standards, provides complete

public health protection and assures

that ground water resources will be safe

for use by future generations. In

addition, the ground water resources in

the vicinity of Yucca Mountain support

a diverse agricultural community and

important ecological systems (e.g., the

endangered Devil’s Hole pupfish).

We believe that separate ground water

protection standards designed to protect

the ground water resource in the

vicinity of Yucca Mountain is a

necessary element of our Yucca

Mountain standards. Our decision to

include separate ground water

protection standards is a policy

decision. As explained in section III.B.4

(How Does Our Rule Protect Ground

Water?), we developed a ground water

protection strategy to guide Agency

programs in their efforts to prevent

adverse effects on human health and the

environment and in protecting the

environmental integrity of the nation’s

ground water resources (see ‘‘The

Strategy,’’ Docket No. A–95–12, Item IIA–3). We have employed ground water

protection programs and standards in a

variety of regulatory programs for

hazardous and non-hazardous waste.

We also have incorporated ground water

protection standards in our generally

applicable disposal regulations for SNF,

HLW, and TRU radioactive wastes (see

40 CFR part 191), and implemented

them at WIPP. Incorporation of ground

water standards in our overall Yucca

Mountain standards provides

consistency with other Agency

programs and assures consistent

protection wherever SNF, HLW, and

TRU radioactive waste may be disposed

of in this country.

We believe that both ground-water

protection standards, incorporating the

MCLs to protect ground-water resources,

and an individual-protection standard,

as embodied in an all-pathways

standard, are complementary and

necessary to provide adequate public

health protection and protection of an

invaluable national natural resource.

For a more detailed discussion of the

issues associated with the options for

the individual-protection standard and

the ground-water protection standards,

please see the Response to Comments

document.

16. We Are Proposing To Require, in the

Individual-Protection Standard, That

DOE Must Project the Disposal System’s

Performance After 10,000 Years. Are the

Specified Uses of the Projections

Appropriate and Adequate?

Comments/Our Responses. Some

comments supporting our 10,000-year

compliance period also endorsed the

idea that projections of the disposal

system’s performance beyond 10,000

years would, among other things, be

fraught with greater uncertainties and

would not necessarily provide greater

public health protection. A few

comments supported our requirement

that DOE project doses beyond 10,000

years and include the results of these

projections in the Yucca Mountain EIS.

In addition, a few comments suggested

that any post-10,000-year projection

should serve only to provide ‘‘regulatory

insight.’’

Comments supporting the use of a

post-10,000-year projection for

regulatory purposes cited the long-term

hazard posed by the wastes planned for

Yucca Mountain, the need to protect

future generations, and the possibility

that the individual doses would exceed

our standard in the post-10,000-year

time frame. As indicated in our

response to Question 8 above, we

considered these and other issues in

determining that a 10,000-year

compliance period is most appropriate.

This compliance period is protective,

meaningful, and practical to implement.

By also including a post-10,000-year

dose assessment in the EIS, which

provides more complete information on

long-term performance, we believe a

robust disposal system protective for

time periods beyond 10,000 years will

result.

In considering the appropriate use of

the post-10,000-year dose assessment,

we have had to balance these very

difficult issues. It is possible to set

computer models to run for time periods

beyond 10,000 years; however, this

approach does not necessarily result in

an equal or higher level of confidence

that the exposed individuals will be

protected. As numerous comments

pointed out, it is likely that such results

will contain greater uncertainties. We

agree with these comments. Yet, despite

these greater uncertainties, such

assessments can be somewhat

informative though not necessarily

reliable dose predictions. We note, for

example, the considerations that

supported Sweden’s proposed

regulations for SNF and nuclear waste

(‘‘The Swedish Radiation Protection

Institute’s Proposed Regulations

Concerning the Final Management of

Spent Nuclear Fuel or Nuclear Waste,’’

SSI Report 97:07, May 1997, Docket No.

A–95–12, Item V–A–11). Regarding

long-term assessments (beyond 1,000

years), such studies ‘‘do not mean that

the full protective capacity of the

repository can be forecasted, e.g., on the

scale of a million years into the future.

However, studies of such (repository)

subsystems can provide valuable

information without actually being

considered as a prediction of doses to

living organisms’ (Id. at 11). We believe

that requiring DOE to include a post10,000-year dose assessment in the EIS

is an appropriate means to address the

issues associated with such long-term

impacts. We note that in our proposal,

we stated that ‘‘NRC is not to use’’ post10,000-year results in assessing

compliance with the individualprotection standard. However, in its

comments on our proposal, NRC stated

that, if DOE uses post-10,000-year

results to bolster its compliance case,

‘‘the Commission should not be

constrained from considering such

information’’ (Docket No. A–95–12, Item

II–D–92). We agree. At the very least,

more complete information on longterm disposal system performance will

be available. In addition, during this

time, the repository design will become

more clearly defined by new

information. For more extensive

discussions of this issue, please see our

response to Question 8 above and the

Response to Comments document.

VI. Severability

As discussed above at Section III.B.1,

the purpose of the Individual Protection

Standard is to protect public health and

safety. As discussed in Section III.B.4,

the Ground Water Protection Standard

serves two purposes. First, it protects

the ground water resource. Second, by

protecting that resource, the Ground

Water Protection Standard also furthers

the goal of public health and safety.

Consistent with the recommendations of

the National Academy of Sciences, the

Individual Protection Standard is

adequate in itself to protect public

health and safety. In addition, EPA is

adopting the Ground Water Protection

Standard in its discretion in order to

provide additional protection to the

vital ground water resource, and in so

doing, is also providing an extra

measure of public health and safety

protection. Thus, notwithstanding that

the Individual Protection and Ground

Water Standards have coincident

32130 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

compliance points and, as implemented

by NRC, may have other similarities,

these two provisions are wholly

severable.

VI. Regulatory Analyses

A. Executive Order 12866

Under Executive Order 12866 [58

Federal Register 51735 (October 4,

1993)], the Agency must determine

whether the regulatory action is

‘‘significant’’ and therefore subject to

review by the Office of Management and

Budget (OMB) and the requirements of

the Executive Order. Executive Order

12866 defines a ‘‘significant regulatory

action’’ as one that is likely to result in

a rule that may:

(1) Have an annual effect upon the

economy of $100 million or more or

adversely affect in a material way the

economy, a sector of the economy,

productivity, competition, jobs, the

environment, public health or safety, or state,

local, or tribal governments or communities;

(2) Create a serious inconsistency or

otherwise interfere with an action taken or

planned by another agency;

(3) Materially alter the budgetary impact of

entitlements, grants, user fees, or loan

programs or the rights and obligations of

recipients thereof; or

(4) Raise novel legal or policy issues

arising out of legal mandates, the President’s

priorities, or the principles set forth in the

Executive Order.

In accordance with the terms of

Executive Order 12866, EPA determined

that this rule is a ‘‘significant regulatory

action’’ because it raises novel legal or

policy issues arising out of the specific

legal mandate of Section 801 of the

Energy Policy Act of 1992. Thus, this

action was submitted to OMB for

review.

In accordance with the terms of

Executive Order 12866, EPA determined

that this rule is a ‘‘significant regulatory

action’’ because it raises novel legal or

policy issues arising out of the specific

legal mandate of Section 801 of the

Energy Policy Act of 1992. Thus, this

action was submitted to OMB for

review. Any changes to the rule that

were made in response to OMB

suggestions or recommendations have

been documented in the public record.

B. Executive Order 12898

Executive Order 12898, ‘‘Federal

Actions to Address Environmental

Justice in Minority Populations And

Low-income Populations

(Environmental Justice),’’ directs us to

incorporate environmental justice as

part of our overall mission by

identifying and addressing

disproportionately high and adverse

human health and environmental effects

of programs, policies, and activities

upon minority populations and lowincome populations.

We find no disproportionate impact

in the outcome of this rulemaking. No

plan has thus been devised to address

a disproportionate impact.

C. Executive Order 13045

Executive Order 13045, ‘‘Protection of

Children from Environmental Health

Risks and Safety Risks,’’ (62 FR 19885,

April 23, 1997) applies to any rule that

(1) is determined to be ‘‘economically

significant’’ as defined under Executive

Order 12866, and (2) concerns an

environmental health or safety risk that

we have reason to believe may have a

disproportionate effect upon children. If

the regulatory action meets both criteria,

we must evaluate the environmental

health or safety effects of the planned

rule upon children, and explain why the

planned regulation is preferable to other

potentially effective and reasonably

feasible alternatives that we considered.

As discussed in the preamble in

sections II.C and III.B.1.a, the primary

risk factor considered in our risk

assessment is incidence of fatal cancer.

We have derived a risk value for the

onset of fatal cancer that considers

children, since it is an overall average

risk value (see Chapter 6 of the BID for

more details) that includes all ages from

birth onward, all exposure pathways,

both genders, and most radionuclides.

We do note that the risk factor does not

include the fetus. However, we believe

that the risk of fatal cancer per unit dose

incurred by the unborn is similar to that

for those who have been born, but the

exposure period is very short compared

to the rest of the individual’s average

lifetime, so the risk of fatal cancer to the

unborn is proportionately lower and

does not have a significant impact upon

the overall risk of fatal cancer incurred

by an individual over a lifetime. (See

Chapter 6 of the BID for more discussion

of the risk of fatal cancer resulting from

in utero exposure.)

Therefore, this final rule is not subject

to Executive Order 13045 because we do

not have reason to believe the

environmental health risks or safety

risks addressed by this action present a

disproportionate risk to children.

D. Executive Order 13084

On January 1, 2001, Executive Order

13084 was superseded by Executive

Order 13175. However, this rule was

developed when Executive Order 13084

was still in force, and so tribal

considerations were addressed under

Executive Order 13084.

Under Executive Order 13084,

‘‘Consultation and Coordination with

Indian Tribal Governments,’’ we may

not issue a regulation that is not

required by statute, that significantly or

uniquely affects the communities of

Indian tribal governments, and that

imposes substantial direct compliance

costs upon those communities, unless

the Federal government provides the

funds necessary to pay the direct

compliance costs incurred by the tribal

governments, or we consult with those

governments. If we comply by

consulting, Executive Order 13084

requires us to provide to OMB, in a

separately identified section of the

preamble to the rule, a description of

the extent of our prior consultation with

representatives of affected tribal

governments, a summary of the nature

of their concerns, and a statement

supporting the need to issue the

regulation. In addition, Executive Order

13084 requires us to develop an

effective process permitting elected

officials and other representatives of

Indian tribal governments ‘‘to provide

meaningful and timely input in the

development of regulatory policies on

matters that significantly or uniquely

affect their communities.’’

The radiological protection standards

promulgated by today’s rule are

applicable solely and exclusively to the

Department of Energy’s potential storage

and disposal facility at Yucca Mountain.

Therefore, this rule does not

significantly or uniquely affect the

communities of Indian tribal

governments, nor does it impose any

direct compliance costs on such

communities. Accordingly, the

requirements of section 3(b) of

Executive Order 13084 do not apply to

this rule.

E. Executive Order 13132

Executive Order 13132, entitled

‘‘Federalism’’ (64 FR 43255, August 10,

1999), requires EPA to develop an

accountable process to ensure

‘‘meaningful and timely input by State

and local officials in the development of

regulatory policies that have federalism

implications.’’ ‘‘Policies that have

federalism implications’’ is defined in

the Executive Order to include

regulations that have ‘‘substantial direct

effects on the States, on the relationship

between the national government and

the States, or on the distribution of

power and responsibilities among the

various levels of government.’’

This final rule does not have

federalism implications. It will not have

substantial direct effects on the States,

on the relationship between the national

government and the States, or on the

distribution of power and

responsibilities among the various

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32131

levels of government, as specified in

Executive Order 13132. Thus, Executive

Order 13132 does not apply to this rule.

Nonetheless, in developing its proposed

rule EPA held public meetings in

Nevada and Washington, D.C. during

which comment was received from and

discussions were had with

representatives from the State of Nevada

and various county officials. EPA also

had informal meetings with State and

local officials to apprise them of the

status of the rulemaking.

F. National Technology Transfer and

Advancement Act

Section 12(d) of the National

Technology Transfer and Advancement

Act of 1995 (NTTAA), Public Law 104–

113, section 12(d) (15 U.S.C. 272 note)

directs us to use voluntary consensus

standards in our regulatory activities

unless to do so would be inconsistent

with applicable law or otherwise

impractical. Voluntary consensus

standards are technical standards (e.g.,

materials specifications, test methods,

sampling procedures, and business

practices) that are developed or adopted

by voluntary consensus standards

bodies. The NTTAA directs us to

provide Congress, through OMB,

explanations when we decide not to use

available and applicable voluntary

consensus standards.

In our proposal, we requested public

comment on potentially applicable

voluntary consensus standards that

would be appropriate for inclusion in

the Yucca Mountain rule. We received

no comments on this aspect of the rule.

The closest analogy to consensus

standards for radioactive waste disposal

facilities are our regulations at 40 CFR

part 191. As discussed above in this

preamble, Congress expressly prohibited

the application of the 40 CFR part 191

standards to the Yucca Mountain

disposal facility, and, therefore, the

standards promulgated today are sitespecific standards developed solely for

application to the Yucca Mountain

disposal facility.

G. Paperwork Reduction Act

We have determined that this rule

contains no information collection

requirements within the scope of the

Paperwork Reduction Act, 42 U.S.C.

3501–20.

H. Regulatory Flexibility Act (RFA), as

amended by the Small Business

Regulatory Enforcement Fairness Act of

1996 (SBREFA), 5 U.S.C. 601 et seq

The Congressional Review Act, 5

U.S.C. 801 et seq., as added by the Small

Business Regulatory Enforcement

Fairness Act of 1996, generally provides

that before a rule may take effect, the

agency promulgating the rule must

submit a rule report, which includes a

copy of the rule, to each House of the

Congress and to the Comptroller General

of the United States. Section 804,

however, exempts from section 801 the

following types of rules: rules of

particular applicability; rules relating to

agency management or personnel; and

rules of agency organization, procedure,

or practice that do not substantially

affect the right or obligations of nonagency parties. (5 U.S.C. 804(3)) The

EPA is not required to submit a rule

report regarding today’s action under

section 801 because this is a rule of

particular applicability.

I. Unfunded Mandates Reform Act

Title II of the Unfunded Mandates

Reform Act of 1995 (UMRA, Public Law

104–4) establishes requirements for

Federal agencies to assess the effects of

their regulatory actions upon state,

local, and tribal governments and the

private sector. Under section 202 of

UMRA, we generally must prepare a

written statement, including a costbenefit analysis, for proposed and final

rules with ‘‘Federal mandates’’ that may

result in expenditures by state, local,

and tribal governments, in the aggregate,

or to the private sector, of $100 million

or more in any one year. Before we

promulgate a rule for which a written

statement is needed, section 205 of

UMRA generally requires us to identify

and consider a reasonable number of

regulatory alternatives and adopt the

least costly, most cost-effective, or least

burdensome alternative that achieves

the objectives of the rule. The

provisions of section 205 do not apply

when they are inconsistent with

applicable law. Moreover, section 205

allows us to adopt an alternative other

than the least costly, most cost-effective,

or least burdensome if the

Administrator publishes with the final

rule an explanation as to why that

alternative was not adopted. Before we

establish any regulatory requirements

that significantly or uniquely affect

small governments, including tribal

governments, we must develop, under

section 203 of UMRA, a smallgovernment-agency plan. The plan must

provide for notifying potentially

affected small governments, enabling

officials of affected small governments

to have meaningful and timely input

into the development of regulatory

proposals with significant Federal

intergovernmental mandates, and

informing, educating, and advising

small governments on compliance with

the regulatory requirements.

Today’s rule contains no Federal

mandates (under the regulatory

provisions of Title II of UMRA) for

State, local, or tribal governments or the

private sector. The final rule

promulgates radiological protection

standards applicable solely and

exclusively to the Department of

Energy’s potential storage and disposal

facility at Yucca Mountain. The rule

imposes no enforceable duty on any

State, local or tribal governments or the

private sector. Thus, today’s rule is not

subject to the requirements of sections

202 and 205 of UMRA.

J. Executive Order 13211

Executive Order 13211, ‘‘Actions

Concerning Regulations That

Significantly Affect Energy Supply,

Distribution, or Use,’’ (66 FR 28355

(May 22, 2001)), provides that agencies

shall prepare and submit to the

Administrator of the Office of

Information and Regulatory Affairs,

Office of Management and Budget, a

Statement of Energy Effects for certain

actions identified as ‘‘significant energy

actions.’’ Section 4(b) of Executive

Order 13211 defines ‘‘significant energy

actions’’ as ‘‘any action by an agency

(normally published in the Federal

Register) that promulgates or is

expected to lead to the promulgation of

a final rule or regulation, including

notices of inquiry, advance notices of

proposed rulemaking, and notices of

proposed rulemaking: (1)(i) That is a

significant regulatory action under

Executive Order 12866 or any successor

order, and (ii) is likely to have a

significant adverse effect on the supply,

distribution, or use of energy; or (2) that

is designated by the Administrator of

the Office of Information and Regulatory

Affairs as a significant energy action.’’

We have not prepared a Statement of

Energy Effects because this rule is not a

significant energy action, as defined in

Executive Order 13211. While this rule

is a significant regulatory action under

Executive Order 12866, we have

determined that it is not likely to have

an adverse effect on the supply,

distribution, or use of energy.

List of Subjects in 40 CFR Part 197

Environmental protection, High-level

radioactive waste Nuclear energy,

Radiation protection, Radionuclides,

Spent nuclear fuel, Uranium, Waste

treatment and disposal.

Dated: June 5, 2001.

Christine Todd Whitman,

Administrator.

The Environmental Protection Agency

is adding a new part 197 to Subchapter

32132 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

F of Chapter I, title 40 of the Code of

Federal Regulations, as follows:

Subchapter F—Radiation Protection

Programs

PART 197—PUBLIC HEALTH AND

ENVIRONMENTAL RADIATION

PROTECTION STANDARDS FOR

YUCCA MOUNTAIN, NEVADA

Subpart A—Public Health and

Environmental Standards for Storage

Sec.

197.1 What does subpart A cover?

197.2 What definitions apply in subpart A?

197.3 How is subpart A implemented?

197.4 What standard must DOE meet?

197.5 When will this part take effect?

Subpart B—Public Health and

Environmental Standards for Disposal

197.11 What does subpart B cover?

197.12 What definitions apply in subpart B?

197.13 How is subpart B implemented?

197.14 What is a reasonable expectation?

197.15 How must DOE take into account

the changes that will occur during the

10,000 years after disposal?

Individual-Protection Standard

197.20 What standard must DOE meet?

197.21 Who is the reasonably maximally

exposed individual?

Human-Intrusion Standard 197.25 What

standard must DOE meet?

197.26 What are the circumstances of the

human intrusion?

Ground Water Protection Standards

197.30 What standards must DOE meet?

197.31 What is a representative volume?

Additional Provisions

197.35 What other projections must DOE

make?

197.36 Are there limits on what DOE must

consider in the performance

assessments?

197.37 Can EPA amend this rule?

197.38 Are The Individual Protection and

Ground Water Protection Standards

Severable?

Authority: Sec. 801, Pub. L. 102–486, 106

Stat. 2921, 42 U.S.C. 10141 n.

Subpart A—Public Health and

Environmental Standards for Storage

§ 197.1 What does subpart A cover?

This subpart covers the storage of

radioactive material by DOE in the

Yucca Mountain repository and on the

Yucca Mountain site.

§ 197.2 What definitions apply in subpart

A?

Annual committed effective dose

equivalent means the effective dose

equivalent received by an individual in

one year from radiation sources external

to the individual plus the committed

effective dose equivalent.

Committed effective dose equivalent

means the effective dose equivalent

received over a period of time (e.g., 30

years,), as determined by NRC, by an

individual from radionuclides internal

to the individual following a one-year

intake of those radionuclides.

DOE means the Department of Energy.

Effective dose equivalent means the

sum of the products of the dose

equivalent received by specified tissues

following an exposure of, or an intake

of radionuclides into, specified tissues

of the body, multiplied by appropriate

weighting factors.

EPA means the Environmental

Protection Agency.

General environment means

everywhere outside the Yucca Mountain

site, the Nellis Air Force Range, and the

Nevada Test Site.

High-level radioactive waste means:

(1) The highly radioactive material

resulting from the reprocessing of spent

nuclear fuel, including liquid waste

produced directly in reprocessing and

any solid material derived from such

liquid waste that contains fission

products in sufficient concentrations;

and

(2) Other highly radioactive material

that the Commission, consistent with

existing law, determines by rule

requires permanent isolation.

Member of the public means anyone

who is not a radiation worker for

purposes of worker protection.

NRC means the Nuclear Regulatory

Commission.

Radioactive material means matter

composed of or containing

radionuclides subject to the Atomic

Energy Act of 1954, as amended (42

U.S.C. 2014 et seq.). Radioactive

material includes, but is not limited to,

high-level radioactive waste and spent

nuclear fuel.

Spent nuclear fuel means fuel that has

been withdrawn from a nuclear reactor

following irradiation, the constituent

elements of which have not been

separated by reprocessing.

Storage means retention (and any

associated activity, operation, or process

necessary to carry out successful

retention) of radioactive material with

the intent or capability to readily access

or retrieve such material.

Yucca Mountain repository means the

excavated portion of the facility

constructed underground within the

Yucca Mountain site.

Yucca Mountain site means:

(1) The site recommended by the

Secretary of DOE to the President under

section 112(b)(1)(B) of the Nuclear

Waste Policy Act of 1982 (42 U.S.C.

10132(b)(1)(B)) on May 27, 1986; or

(2) The area under the control of DOE

for the use of Yucca Mountain activities

at the time of licensing, if the site

designated under the Nuclear Waste

Policy Act is amended by Congress prior

to the time of licensing.

§ 197.3 How is subpart A implemented?

The NRC implements this subpart A.

The DOE must demonstrate to NRC that

normal operations at the Yucca

Mountain site will and do occur in

compliance with this subpart before

NRC may grant or continue a license for

DOE to receive and possess radioactive

material within the Yucca Mountain

site.

§ 197.4 What standard must DOE meet?

The DOE must ensure that no member

of the public in the general environment

receives more than an annual

committed effective dose equivalent of

150 microsieverts (15 millirems) from

the combination of:

(a) Management and storage (as

defined in 40 CFR 191.2) of radioactive

material that:

(1) Is subject to 40 CFR 191.3(a); and

(2) Occurs outside of the Yucca

Mountain repository but within the

Yucca Mountain site; and

(b) Storage (as defined in § 197.2) of

radioactive material inside the Yucca

Mountain repository.

§ 197.5 When will this part take effect?

The standards in this part take effect

on July 13, 2001.

Subpart B—Public Health and

Environmental Standards for Disposal

§ 197.11 What does subpart B cover?

This subpart covers the disposal of

radioactive material in the Yucca

Mountain repository by DOE.

§ 197.12 What definitions apply in subpart

B?

All definitions in subpart A of this

part and the following:

Accessible environment means any

point outside of the controlled area,

including:

(1) The atmosphere (including the

atmosphere above the surface area of the

controlled area);

(2) Land surfaces;

(3) Surface waters;

(4) Oceans; and

(5) The lithosphere.

Aquifer means a water-bearing

underground geological formation,

group of formations, or part of a

formation (excluding perched water

bodies) that can yield a significant

amount of ground water to a well or

spring.

Barrier means any material, structure,

or feature that, for a period to be

determined by NRC, prevents or

substantially reduces the rate of

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32133

movement of water or radionuclides

from the Yucca Mountain repository to

the accessible environment, or prevents

the release or substantially reduces the

release rate of radionuclides from the

waste. For example, a barrier may be a

geologic feature, an engineered

structure, a canister, a waste form with

physical and chemical characteristics

that significantly decrease the mobility

of radionuclides, or a material placed

over and around the waste, provided

that the material substantially delays

movement of water or radionuclides.

Controlled area means:

(1) The surface area, identified by

passive institutional controls, that

encompasses no more than 300 square

kilometers. It must not extend farther:

(a) South than 36° 40′ 13.6661′′ north

latitude, in the predominant direction of

ground water flow; and

(b) Than five kilometers from the

repository footprint in any other

direction; and

(2) The subsurface underlying the

surface area.

Disposal means the emplacement of

radioactive material into the Yucca

Mountain disposal system with the

intent of isolating it for as long as

reasonably possible and with no intent

of recovery, whether or not the design

of the disposal system permits the ready

recovery of the material.

Disposal of radioactive material in the

Yucca Mountain disposal system begins

when all of the ramps and other

openings into the Yucca Mountain

repository are sealed.

Ground water means water that is

below the land surface and in a

saturated zone.

Human intrusion means breaching of

any portion of the Yucca Mountain

disposal system, within the repository

footprint, by any human activity.

Passive institutional controls means:

(1) Markers, as permanent as

practicable, placed on the Earth’s

surface;

(2) Public records and archives;

(3) Government ownership and

regulations regarding land or resource

use; and

(4) Other reasonable methods of

preserving knowledge about the

location, design, and contents of the

Yucca Mountain disposal system.

Peak dose means the highest annual

committed effective dose equivalent

projected to be received by the

reasonably maximally exposed

individual.

Performance assessment means an

analysis that:

(1) Identifies the features, events,

processes, (except human intrusion),

and sequences of events and processes

(except human intrusion) that might

affect the Yucca Mountain disposal

system and their probabilities of

occurring during 10,000 years after

disposal;

(2) Examines the effects of those

features, events, processes, and

sequences of events and processes upon

the performance of the Yucca Mountain

disposal system; and

(3) Estimates the annual committed

effective dose equivalent incurred by

the reasonably maximally exposed

individual, including the associated

uncertainties, as a result of releases

caused by all significant features,

events, processes, and sequences of

events and processes, weighted by their

probability of occurrence.

Period of geologic stability means the

time during which the variability of

geologic characteristics and their future

behavior in and around the Yucca

Mountain site can be bounded, that is,

they can be projected within a

reasonable range of possibilities.

Plume of contamination means that

volume of ground water in the

predominant direction of ground water

flow that contains radioactive

contamination from releases from the

Yucca Mountain repository. It does not

include releases from any other

potential sources on or near the Nevada

Test Site.

Repository footprint means the

outline of the outermost locations of

where the waste is emplaced in the

Yucca Mountain repository.

Slice of the plume means a crosssection of the plume of contamination

with sufficient thickness parallel to the

prevalent direction of flow of the plume

that it contains the representative

volume.

Total dissolved solids means the total

dissolved (filterable) solids in water as

determined by use of the method

specified in 40 CFR part 136.

Undisturbed performance means that

human intrusion or the occurrence of

unlikely natural features, events, and

processes do not disturb the disposal

system.

Undisturbed Yucca Mountain

disposal system means that the Yucca

Mountain disposal system is not

affected by human intrusion.

Waste means any radioactive material

emplaced for disposal into the Yucca

Mountain repository.

Well-capture zone means the volume

from which a well pumping at a defined

rate is withdrawing water from an

aquifer. The dimensions of the wellcapture zone are determined by the

pumping rate in combination with

aquifer characteristics assumed for

calculations, such as hydraulic

conductivity, gradient, and the screened

interval.

Yucca Mountain disposal system

means the combination of underground

engineered and natural barriers within

the controlled area that prevents or

substantially reduces releases from the

waste.

§ 197.13 How is subpart B implemented?

The NRC implements this subpart B.

The DOE must demonstrate to NRC that

there is a reasonable expectation of

compliance with this subpart before

NRC may issue a license. In the case of

the specific numerical requirements in

§ 197.20 of this subpart, and if

performance assessment is used to

demonstrate compliance with the

specific numerical requirements in

§§ 197.25 and 197.30 of this subpart,

NRC will determine compliance based

upon the mean of the distribution of

projected doses of DOE’s performance

assessments which project the

performance of the Yucca Mountain

disposal system for 10,000 years after

disposal.

§ 197.14 What is a reasonable

expectation?

Reasonable expectation means that

NRC is satisfied that compliance will be

achieved based upon the full record

before it. Characteristics of reasonable

expectation include that it:

(a) Requires less than absolute proof

because absolute proof is impossible to

attain for disposal due to the

uncertainty of projecting long-term

performance;

(b) Accounts for the inherently greater

uncertainties in making long-term

projections of the performance of the

Yucca Mountain disposal system;

(c) Does not exclude important

parameters from assessments and

analyses simply because they are

difficult to precisely quantify to a high

degree of confidence; and

(d) Focuses performance assessments

and analyses upon the full range of

defensible and reasonable parameter

distributions rather than only upon

extreme physical situations and

parameter values.

§ 197.15 How must DOE take into account

the changes that will occur during the next

10,000 years after disposal?

The DOE should not project changes

in society, the biosphere (other than

climate), human biology, or increases or

decreases of human knowledge or

technology. In all analyses done to

demonstrate compliance with this part,

DOE must assume that all of those

factors remain constant as they are at

the time of license application

submission to NRC. However, DOE must

32134 Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations

vary factors related to the geology,

hydrology, and climate based upon

cautious, but reasonable assumptions of

the changes in these factors that could

affect the Yucca Mountain disposal

system over the next 10,000 years.

Individual-Protection Standard

§ 197.20 What standard must DOE meet?

The DOE must demonstrate, using

performance assessment, that there is a

reasonable expectation that, for 10,000

years following disposal, the reasonably

maximally exposed individual receives

no more than an annual committed

effective dose equivalent of 150

microsieverts (15 millirems) from

releases from the undisturbed Yucca

Mountain disposal system. The DOE’s

analysis must include all potential

pathways of radionuclide transport and

exposure.

§ 197.21 Who is the reasonably maximally

exposed individual?

The reasonably maximally exposed

individual is a hypothetical person who

meets the following criteria:

(a) Lives in the accessible

environment above the highest

concentration of radionuclides in the

plume of contamination;

(b) Has a diet and living style

representative of the people who now

reside in the Town of Amargosa Valley,

Nevada. The DOE must use projections

based upon surveys of the people

residing in the Town of Amargosa

Valley, Nevada, to determine their

current diets and living styles and use

the mean values of these factors in the

assessments conducted for §§ 197.20

and 197.25; and

(c) Drinks 2 liters of water per day

from wells drilled into the ground water

at the location specified in paragraph (a)

of this section.

Human-Intrusion Standard

§ 197.25 What standard must DOE meet?

The DOE must determine the earliest

time after disposal that the waste

package would degrade sufficiently that

a human intrusion (see § 197.26) could

occur without recognition by the

drillers. The DOE must:

(a) If complete waste package

penetration is projected to occur at or

before 10,000 years after disposal:

(1) Demonstrate that there is a

reasonable expectation that the

reasonably maximally exposed

individual receives no more than an

annual committed effective dose

equivalent of 150 microsieverts (15

millirems) as a result of a human

intrusion, at or before 10,000 years after

disposal. The analysis must include all

potential environmental pathways of

radionuclide transport and exposure;

and

(2) If exposures to the reasonably

maximally exposed individual occur

more than 10,000 years after disposal,

include the results of the analysis and

its bases in the environmental impact

statement for Yucca Mountain as an

indicator of long-term disposal system

performance; and

(b) Include the results of the analysis

and its bases in the environmental

impact statement for Yucca Mountain as

an indicator of long-term disposal

system performance, if the intrusion is

not projected to occur before 10,000

years after disposal.

§ 197.26 What are the circumstances of

the human intrusion?

For the purposes of the analysis of

human intrusion, DOE must make the

following assumptions:

(a) There is a single human intrusion

as a result of exploratory drilling for

ground water;

(b) The intruders drill a borehole

directly through a degraded waste

package into the uppermost aquifer

underlying the Yucca Mountain

repository;

(c) The drillers use the common

techniques and practices that are

currently employed in exploratory

drilling for ground water in the region

surrounding Yucca Mountain;

(d) Careful sealing of the borehole

does not occur, instead natural

degradation processes gradually modify

the borehole;

(e) Only releases of radionuclides that

occur as a result of the intrusion and

that are transported through the

resulting borehole to the saturated zone

are projected; and

(f) No releases are included which are

caused by unlikely natural processes

and events.

Ground Water Protection Standards

§ 197.30 What standards must DOE meet?

The DOE must demonstrate that there

is a reasonable expectation that, for

10,000 years of undisturbed

performance after disposal, releases of

radionuclides from waste in the Yucca

Mountain disposal system into the

accessible environment will not cause

the level of radioactivity in the

representative volume of ground water

to exceed the limits in the following

Table 1:

TABLE 1.—LIMITS ON RADIONUCLIDES IN THE REPRESENTATIVE VOLUME

Radionuclide or type of radiation emitted Limit

Is natural background included?

Combined radium-226 and radium-228 ..................................... 5 picocuries per liter ................................................................. Yes.

Gross alpha activity (including radium-226 but excluding radon

and uranium).

15 picocuries per liter ............................................................... Yes.

Combined beta and photon emitting radionuclides ................... 40 microsieverts (4 millirem) per year to the whole body or

any organ, based on drinking 2 liters of water per day from

the representative volume.

No.

§ 197.31 What is a representative volume?

(a) It is the volume of ground water

that would be withdrawn annually from

an aquifer containing less than 10,000

milligrams of total dissolved solids per

liter of water to supply a given water

demand. The DOE must project the

concentration of radionuclides released

from the Yucca Mountain disposal

system that will be in the representative

volume. The DOE must then use the

projected concentrations to demonstrate

a reasonable expectation to NRC that the

Yucca Mountain disposal system

complies with § 197.30. The DOE must

make the following assumptions

concerning the representative volume:

(1) It includes the highest

concentration level in the plume of

contamination in the accessible

environment;

(2) Its position and dimensions in the

aquifer are determined using average

hydrologic characteristics which have

cautious, but reasonable, values

representative of the aquifers along the

radionuclide migration path from the

Yucca Mountain repository to the

Federal Register / Vol. 66, No. 114 / Wednesday, June 13, 2001 / Rules and Regulations 32135

accessible environment as determined

by site characterization; and

(3) It contains 3,000 acre-feet of water

(about 3,714,450,000 liters or

977,486,000 gallons).

(b) The DOE must use one of two

alternative methods for determining the

dimensions of the representative

volume. The DOE must propose its

chosen method, and any underlying

assumptions, to NRC for approval.

(1) The DOE may calculate the

dimensions as a well-capture zone. If

DOE uses this approach, it must assume

that the:

(i) Water supply well(s) has (have)

characteristics consistent with public

water supply wells in the Town of

Amargosa Valley, Nevada, for example,

well-bore size and length of the

screened intervals;

(ii) Screened interval(s) include(s) the

highest concentration in the plume of

contamination in the accessible

environment; and

(iii) Pumping rates and the placement

of the well(s) must be set to produce an

annual withdrawal equal to the

representative volume and to tap the

highest concentration within the plume

of contamination.

(2) The DOE may calculate the

dimensions as a slice of the plume. If

DOE uses this approach, it must:

(i) Propose to NRC, for its approval,

where the location of the edge of the

plume of contamination occurs. For

example, the place where the

concentration of radionuclides reaches

0.1% of the level of the highest

concentration in the accessible

environment;

(ii) Assume that the slice of the plume

is perpendicular to the prevalent

direction of flow of the aquifer; and

(iii) Assume that the volume of

ground water contained within the slice

of the plume equals the representative

volume.

Additional Provisions

§ 197.35 What other projections must DOE

make?

To complement the results of

§ 197.20, DOE must calculate the peak

dose of the reasonably maximally

exposed individual that would occur

after 10,000 years following disposal but

within the period of geologic stability.

No regulatory standard applies to the

results of this analysis; however, DOE

must include the results and their bases

in the environmental impact statement

for Yucca Mountain as an indicator of

long-term disposal system performance.

§ 197.36 Are there limits on what DOE

must consider in the performance

assessments?

Yes. The DOE’s performance

assessments shall not include

consideration of very unlikely features,

events, or processes, i.e., those that are

estimated to have less than one chance

in 10,000 of occurring within 10,000

years of disposal. The NRC shall

exclude unlikely features, events, and

processes, or sequences of events and

processes from the assessments for the

human intrusion and ground water

protection standards. The specific

probability of the unlikely features,

events, and processes is to be specified

by NRC. In addition, unless otherwise

specified in NRC regulations, DOE’s

performance assessments need not

evaluate, the impacts resulting from any

features, events, and processes or

sequences of events and processes with

a higher chance of occurrence if the

results of the performance assessments

would not be changed significantly.

§ 197.37 Can EPA amend this rule?

Yes. We can amend this rule by

conducting another notice-andcomment rulemaking. Such a

rulemaking must include a public

comment period. Also, we may hold one

or more public hearings, if we receive a

written request to do so.

§ 197.38 Are The Individual Protection and

Ground Water Protection Standards

Severable?

Yes. The individual protection and

ground water protection standards are

severable.

[FR Doc. 01–14626 Filed 6–8–01; 2:05 pm]

BILLING CODE 6560–50–P