Department of Energy

Washington, DC 20585 (41) APR 261991

Mr. John Linehan, Director

Repository Licensing & Quality

Assurance Project Directorate

Division of High-Level

Waste Management

Office of Nuclear Material

Safety and Safeguards

U.S. Nuclear Regulatory Commission

Washington, D.C. 20555

Dear Mr. Linehan:

Two issues of interest to the U.S. Nuclear Regulatory Commission

arose in association with the U.S. Department of Energy

(DOE)/U.S. Nuclear Regulatory Commission (NRC) Exploratory Shaft

Facility (ESF) meeting, held on January 29-31, 1991. The first

of these issues focused on the availability of the Calico Hills

Risk/Benefit Analysis (CHRBA) Record of Memorandum (RM); the

second issue was related to NRC's understanding of the value and

contribution of the Value of Information (VOI) model to the

CHRBA. Regarding the first issue, immediately prior to the ESF

meeting, DOE provided NRC with a copy of the CHRBA RM.

The NRC review of the Site Characterization Plan/Consultation

Draft (SCP/CD) contained an objection (Objection 2) which

maintained that the plans for excavation and testing in the

Calico Hills Unit were not based on adequate analysis of the

risks and benefits of alternative methods for obtaining the

needed information. Objection #2 to the SCP/CD was closed when

DOE committed to perform an analysis of the benefit, to the

testing program, of penetrating the Calico Hills unit, compared

to the possible risks to site performance. In addition to

performing the analysis, DOE committed to consult with NRC, prior

to initiation of construction. DOE, therefore, produced the

CHRBA to take into consideration NRC comments in making the

decision of how best to characterize the Calico Hills unit and,

eventually, to respond to NRC concerns.

Enclosure 1 includes NRC's CDSCP (SCP/CD) Objection No. 2 with

Action Items in Italics. Enclosure 2 is a copy of the written

commitment made by the DOE in response to the NRC objection on

the CDSCP. This response was provided to NRC on December 28,

1988 as an enclosure to the letter transmitting DOE's Site

Characterization Plan. Similarly, Enclosure 3 provides the

requested roadmap" indicating which sections of the CHRBA

respond to NRC's objection.

9105140144 910426

PDR4 WASTE PDRl

WM- ii ~~ ~ ~ ~ ~ ~ Id
2

With respect to the question regarding the contribution of the

VOI model to the CHRBA, several important general points may be

made. Considerable additional information, and the supporting

rationale, is contained in the Record of Memorandum, and in the

relevant references and transcripts. These documents explain the

results of both the VOI and the Multi-Attribute Utility Analysis

(RUA) studies in detail.

Several important results emerged from the VOI study. In

particular, the estimates of impacts to the waste isolation

capability of the site (judged to be very small) were developed

as part of the VOI portion of the study. In addition, the VOI

results demonstrated how, and by how much, the test program could

improve performance predictions. It is true that the VOI model

indicated that testing had no value, as value was narrowly

defined in the study (i.e., the likelihood of changing decisions

as a result of testing, based on revised predictions of

performance). However, the cumulative results of the study,

which captured in the MUA values associated with testing not

recognized by the VOI model, strongly support the recommendation.

The UA defined value in testing in attributes such as increased

scientific confidence, and an enhanced ability to demonstrate

reasonable assurance with respect to predictions of site

performance. DOE has, therefore, recommended that the NRC staff

not focus on the "no testing" result of the VOI model.

DOE does not believe the CHRBA VOI results are a substitute for

formal PA efforts. In fact, the CHRBA R recommends that DOE

continue conducting Performance Assessment (PA) exercises

(particularly with respect to impacts on waste isolation)

throughout design and site characterization. It is important to

note, however, that there are no currently available PA models at

the DOE, or elsewhere, that are well suited to directly

addressing the question that the CHRBA studied -- that is, what

is the appropriate testing program for the Calico Hills? Current

PA models are very useful for identifying information needs, and

assessing impacts to performance, but balancing the risks and

benefits requires judgement, particularly with respect to how

much information will be required to license the site, should it

be found suitable by the DOE.

Finally, DOE believes that the geotechnical inputs to the VOI

model are important because the multi-disciplined team used

available data to evaluate both site performance and impacts to

waste isolation from testing, considering both expected and

disturbed site conditions. These evaluations indicate that the

contribution of impacts to isolation from testing is a small

fraction of total system releases, and both are far below the

Environmental Protection Agency (EPA) limits (for aqueous

transport). The process used to develop the estimates of impacts

accounted for uncertainty and included conservatism.
3

If have any questions regarding the DOE position on these

two issues, please contact Cori Macaluso of my staff on

(202) 586-2837 or Dave Dobson of the Project Office on

(702) 794-7940.

Sincerely,

'a d d~~~~~~~C"

Dwight E. Shelor

Acting Associate Director for

Systems and Compliance

Office of Civilian Radioactive

Waste Management

Enclosures: As stated

cc w/enclosures:

R. Loux, State of Nevada

C. Gertz, DOE/YMPO/NV

M. Baughman, Lincoln County, NV

D. Bechtel, Clark County, NV

S. Bradhurst, Nye County, NV
ENCLOSURE 1

Page 1 of 3

NRC'S CDSCP OBJECTION NO. 2 WITH ACTION ITEMS IN ITALICS

OBJECTION 2

The NRC staff considers that the need for extending the

Exploratory shaft 1 (ES-1) approximately 400 ft below

the proposed repository horizon into the zeolitic zone

of the Calico Hills unit has not been established in

the CDSCP, nor has the need been established for tests

requiring drifting (horizontal excavation) through the

Calico Hills unit. It has not been demonstrated that

the proposed shaft (ES-1) penetration into the Calico

Hills unit (an important barrier between the repository

horizon and the underlying groundwater table) or the

proposed drifting through it will not have potential

adverse impacts on the waste isolation capability of

the site.

1. Establish the need for extending ES-1 approximately 400 ft below the proposed

repository horizon into the zeolitic zone of the Calico Hills unit.

2. Establish the need for tests requiring drifting through the Calico Hills unit.

3. Demonstrate that the ES-I penetration into the Calico Hills unit or the proposed

drifting through it will not have potential adverse impacts on the waste isolation capability

of the site.

BASIS

o 10 CFR 60.17(a)(2)(iv) requires that, "The SCP

shall contain plans to control any adverse impacts

from such site characterization activities that

are important to waste isolation."

4. Develop plans to control any adverse impacts from such site characterization activities

that are important to waste isolation.

o The last tentative goal on page 8.3.2.5-21

indicates that high confidence is needed that ES1 will terminate no less than 150 m above

groundwater table. It does not appear that this

goal would be reached under the present ES-1

design.
ENCLOSURE 1

Page 2 of 3

S. Will the goal stated on page 8.3.2.5-21 of the CDSCP be met? (Goal: ES-1 shaft

termination no less than 150 m above ground-water table)

o The CDSCP has not identified associated site

characterization activities whose benefits would

outweigh potential adverse impacts of penetrating

the Calico Hills unit, an important barrier below

the proposed repository horizon. The CDSCP has

not provided a detailed discussion of the need for

conducting the identified activities from within

the Calico Hills rather than obtaining the

necessary data by alternate means that meet

isolation constraints.

6. Identify associated site characterization activities whose benefits would outweigh

potential adverse impacts of penetrating the Calico Hills unit.

7. Provide a detailed discussion of the need for conducting the identified activities from

within the Calico Hills rather than obtaining the necessary data by alternate means that

meet isolation constraints.

o Sections 8.3.5.13 (Total System Performance) and

Sections 8.3.5.12 (Groundwater Travel Time)

identify the Calico Hills unit as a primary

barrier. Section 8.3.1.2.2.4.6 (Calico Hills Test

In The Exploratory Shaft Facility, page 8.3.1.2-

242) states that "it is critical to have high

confidence in the understanding of these aspects

of the unit" (Calico Hills), but "on the other

hand exterior penetration or excavation of the

unit for testing purposes may jeopardize the

integrity of the unit as a barrier." This section

also states that the preferred approach to testing

in the Calico Hills unit is to drift horizontally

from the shaft in the up-dip direction, through

the Ghost Dance fault. However, the CDSCP does

not consider the effects of drifting on the Calico

Hills unit, nor does it consider alternative means

of obtaining the necessary data that meet

isolation constraints.

8. Consider the effects of drifting on the Calico Hills unit.

9. Consider alternate means of obtaining the necessary data that meet isolation

constraints.
ENCLOSURE 1

Page 3 of 3

o The CDSCP does not consider potential connection

of flow-paths from underneath the repository waste

emplacement areas to the proposed ES-1 excavation

below the repository horizon or to the proposed

drifts in the Calico Hills unit.

10. Consider potential connection of flow-paths from underneath the repository waste

emplacement areas to the proposed ES-1 excavation below the repository horizon.

11. Consider potential connection of flow-paths from underneath the repository waste

emplacement areas to the proposed drifts in the Calico Hills unit.

RECOMMENDATION

o The SCP should consider plans for characterizing

the Calico Hills unit to the extent necessary

without having to penetrate and damage portions of

this important barrier between repository horizon

level and the groundwater table. If alternative

plans cannot be developed, it should justify the

need for destructive testing of the Calico Hills

unit and analyze the consequences of possible

pathway connections from the proposed waste

emplacement areas to both the lower portion of the

ES-1 and to the proposed drifts in the Calico

Hills unit.

12. Consider plans for characterizing the Calico Hills to the extent necessary without

having to penetrate and damage portions of this important barrier between repository

horizon level and the groundwater table.

13. Justify the need for destructive testing of the Calico Hills unit if alternative plans

cannot be developed.

14. Analyze the consequences of possible pathway connections from the proposed waste

emplacement areas to both the lower portion of the ES-1 and to the proposed drifts in the

Calico Hills unit if alternative plans cannot be developed.
ENCLOSURE 2

KI

DECEMBER 1986

RESPONSE TO NRC OBJECTION 2

OBJECTION 2

The RC staff considers that the need for extending the Exploratory shaft 1

(ES-1) approximately 400 ft below the repository horizon into the zeolitic

zone of the Calico Hills unit has not been established in the CDSCP, nor has

the need been established for tests requiring drifting (horizontal excavation) through the Calico Hills Unit. It has not been demonstrated that the

proposed shaft (ES-1) penetration into the Calico Bills unit (an important

barrier between the repository horizon and the underlying groundwater table)

or the proposed drifting through it will not have potential adverse impacts

on the waste isolation capability of the site.

DOE RESPONSE

The DOE approach to resolution of this objection is described in Section

8.4.2.1.6.1 (Characterization of Calico ills) of the SCP. Briefly, the DOE

will defer the decision on penetrating and drifting in the Calico ills unit

from exploratory shaft pending completion of analyses comparing (1) the

needed data, (2) the alternative means of obtaining the data, (3) the

benefits of obtaining the data in terms-of reducing uncertainty about site

performance, and (4) the risks to site performance by obtaining the data.

The DOE recognizes that additional information on hydrologic parameters and

processes, as well as radionuclide retardation parameters and processes, will

be needed to adequately understand the role the Calico Hills unit will play

in isolation. The various alternatives available for reducing uncertainty

include data collection from outcrops and surface-based boreholes and in situ

testing in the Topopah Spring Member or the Calico ills unit. The potential

benefits in terms of reducing uncertainty in travel-time and radionuclide

retardation predictions through testing in the Calico Hills unit will be

weighed against an assessment of the potential risks in terms of compromising

site performance associated with such testing.

The RC will be consulted before a decision is made on penetrating the Calico

Bills unit. Should a decision be made to proceed, the design and layout of

the exploratory shaft facility are sufficiently flexible so that the shaft

could be extended and additional drifting could be accommodated without a

major redesign of the facility.
K-'

ENCLOSURE 3

Page 1 of 3

ACTION ITEMS FROM NRC'S CDSCP

OBJECTION NO. 2

REFERENCES TO CHRBA1 THAT

RESPOND TO ACTION ITEMS

1. Establish the need for extending ES-I

approximately 400 ft below the proposed

repository horizon into the zeolitic zone of

the Calico Hills unit.

2. Establish the need for tests requiring

drifting through the Calico Hills unit.

3. Demonstrate that the ES-I penetration

into the Calico Hills unit or the proposed

drifting through it will not have potential

adverse impacts on the waste isolation

capability of the site.

4. Develop plans to control any adverse

impacts from such site characterization

activities that are important to waste

isolation.

The need for excavation into

the Calico Hills unit was

established by the technical

and management panels

reviewing the VOI model

results. See pp 2.6.1.8-12,

2.6.1.8-13, and Appendix C.

Also see Section 2.2.

The need for drifting through

the Calico Hills unit was

established by the results of

the RUA - a preference for

modified versions of

Strategies 2 or 5. See

Section 2.6.2.3.3, p

2.6.2.3.3-1.

Potential adverse impacts are

discussed in Section 2.6.1.6

(p 2.6.1.6-1) and are

summarized in Section

2.6.1.6.5 (p 2.6.1.6-36).

Section 2.6.1.6.2 provides an

analysis of groundwater flow

in excavated openings relative

to plans for backfilling and

sealing.
ENCLOSURE 3

Page 2 of 3

5. Wl the goal stated on page 8.3.2.5-

21 of the CDSCP be met? (Goat ES-1

shaft termination no less than 150 m

above ground-water table)

6. Identify associated site characterization

activities whose benefits would outweigh

potential adverse impacts of penetrating

the Calico Hills unit.

7. Provide a detailed discussion of the

need for conducting the identified

activities from within the Calico Hills

rather than obtaining the necessary data

by alternate means that meet isolation

constraints.

8. Consider the effects of drifting on the

Calico Hills unit.

9. Consider alternate means of obtaining

the necessary data that meet isolation

constraints.

The goal stated in the CDSCP

was changed in the SCP to:

"The thickness between the

bottom of ES-1 or any

exploratory shaft facility

(ESF) drifting and the groundwater table should be greater

than the minimum thickness of

the Calico Hills above the

water table anywhere within

the repository boundary."

This goal is incorporated in

the descriptions of preferred

strategies 2 and 5. See pp

2.4-20 and 2.4-23.

Information needed to

characterize the Calico Hills

unit are correlated to the

various testing techniques in

Section 2.3 (p 2.3-1). As

noted above, potential adverse

impacts are discussed in

Section 2.6.1.6 (p 2.6.1.6-1)

and are summarized in Section

2.6.1.6.5 (p 2.6.1.6-36).

That discussion is provided in

Section 2.7 (p 2.7-1) where

tradeoffs between the variousstrategies are discussed.

See Item 3, above.

Alternate means are considered

in Section 2.3 (see Item 6,

above) and 2.7 (see Item 7,

above).
.' . . '

ENCLOSURE 3

Page 3 of 3

10. Consider potential connection of

flow-paths from underneath the repository

waste emplacement areas to the proposed

ES-1 excavation below the repository

horizon.

11. Consider potential connection of

flow-paths from underneath the repository

waste emplacement areas to the proposed

drifts in the Calico Hills unit.

12. Consider plans for characterizing the

Calico Hills to the extent necessary

without having to penetrate and damage

portions of this important barrier between

repository horizon level and the

groundwater table.

13. Justify the need for destructive testing

of the Calico Hills unit if alternative

plans cannot be developed.

14. Analyze the consequences of possible

pathway connections from the proposed

waste emplacement areas to both the

lower portion of the ES-I and to the

proposed drifts in the Calico Hills unit if

alternative plans cannot be developed.

Potential flow paths are

discussed in general in

Section 2.6.1.6.2 (p 2.6.1.6-

4) and Section 2.6.1.6.3 (p

2.6.1.6-18) and are applied to

each strategy in Section

2.6.1.6.4 (p 2.6.1.6-24).

See Item 10, above.

Section 2.3 evaluates test

techniques other than direct

excavation. Also, see Items 7

and 9, above.

See Items 1 and 6, above.

See Item 9, above.

1. Yucca Mountain Site Characterization Project, Record

Memorandum. Risk/Benefit Analysis of Alternative Strategies

for Characterizing the Calico Hills Unit at Yucca Mountain,

Rev. 0. January 1991.