April 30, 2001

Mr. Ronald A. Milner, Chief Operating Officer

Office of Civilian Radioactive Waste Management

U. S. Department of Energy

1000 Independence Avenue, SW

Washington, DC 20585

SUBJECT: U.S. NUCLEAR REGULATORY COMMISSIONíS OBSERVATION AUDIT

REPORT NO. OAR-01-04, ìOBSERVATION AUDIT OF THE OFFICE OF

CIVILIAN RADIOACTIVE WASTE MANAGEMENT, QUALITY ASSURANCE

DIVISION, AUDIT NO. M&O-ARP-01-01"

Dear Mr. Milner:

I am transmitting the U.S. Nuclear Regulatory Commissionís (NRCís) Observation Audit Report

(No. OAR-01-04), of the U.S. Department of Energyís (DOEís), Office of Civilian Radioactive

Waste Management (OCRWM), Office of Quality Assuranceís,(OQAís), audit of activities

regarding to the ìEngineered Barrier System Process Model Reportî (EBS PMR). The EBS

PMR was prepared by, and the supporting activities performed by, the OCRWM Management

and Operating Contractor (M&O). This audit was conducted on February 20 through 23, 2001,

at the M&O facilities in Las Vegas, Nevada.

Selected Analysis Model Reports (AMRs) supporting the EBS PMR were previously audited on

February 7ñ11, 2000 (OQA Audit No. M&OñARPñ00ñ06), and at that time several of the

documents audited were still in the process of being developed. The purpose of this audit was

to evaluate the implementation of the applicable provisions contained in the OCRWM Quality

Requirements and Description, DOE/RWñ0333P, Revision 10, by evaluating two selected

AMRs supporting the EBS PMR. Also, the audit evaluated action taken as a result of the

findings and recommendations from the February 2000 EBS audit.

The NRC observers (observers) determined that this audit was effective in identifying potential

deficiencies and recommending improvements for the PMR and AMRs reviewed. During the

conduct of the audit, both the OQA audit team (audit team) and the observers independently

reviewed applicable analysis reports and supporting data, models, and software. The

observers were disappointed to note that though previous observation audits indicated effective

corrective measures had been taken with procedural compliance in the AMR development

process, some of the AMRs selected for this evaluation still indicated discrepancies similar to

what had been found during the 2000 audit. The observers submitted two audit observer

inquiries (AOIs) requesting clarification and information on audited documents. The AOIs

addressed the corrective action process and data usefulness.
R.A. Milner 2

Although the audit team identified some potential deficiencies, and two AOIs requesting

clarification and information were generated, the observers believe that the AMRs and PMR

reviewed during the audit were generally technically sound with the exception of AMR ANLEBS-MD-000033, Revision 00, ICN 1, ìPhysical and Chemical Environmental Abstraction

Modelî (E0100) which had problems in the areas of traceability/transparency, calculations, and

model validation. This is further discussed in sections 4.4 and 4.5 of this report. The

observers agreed with the audit teamís conclusions, findings, and recommendations presented

at the audit exit.

Although a written response to this letter and the enclosed report is not required, we do request

that you respond to the two AOIs. If you have any questions, please contact Ted Carter at

(301) 415-6684.

Sincerely,

/RA/

C. William Reamer, Chief

High-Level Waste Branch

Division of Waste Management

Office of Nuclear Material Safety

 and Safeguards

Enclosure: NRC Observation Audit Report

 No. OAR-01-04, ìObservation Audit

of the Office of Civilian Radioactive 

Waste Management, Quality Assurance

Division, Audit No. M&O-ARP-01-01"
R.A. Milner 3

Although the audit team identified some potential deficiencies, and two AOIs requesting

clarification and information were generated, the observers believe that the AMRs and PMR

reviewed during the audit were generally technically sound with the exception of AMR ANLEBS-MD-000033, Revision 00, ICN 1, ìPhysical and Chemical Environmental Abstraction

Modelî (E0100) which had problems in the areas of traceability/transparency, calculations, and

model validation. This is further discussed in sections 4.4 and 4.5 of this report. The

observers agreed with the audit teamís conclusions, findings, and recommendations presented

at the audit exit.

Although a written response to this letter and the enclosed report is not required, we do request

that you respond to the two AOIs. If you have any questions, please contact Ted Carter at

(301) 415-6684

Sincerely,

/RA/

C. William Reamer, Chief

High-Level Waste Branch

Division of Waste Management

Office of Nuclear Material Safety

 and Safeguards

Enclosure: NRC Observation Audit Report

 No. OAR-01-04, ìObservation Audit

of the Office of Civilian Radioactive 

Waste Management, Quality Assurance

Division, Audit No. M&O-ARP-01-01"

DISTRIBUTION:

File Center PUBLIC ACNW LSS CNWRA NMSS r/f HLWB r/f

SWastler CGlenn BMabrito WBelke RLatta CWReamer DWMr/f

LCampbell DBrooks TMatula

ADAMS Accession No. ML011200609 This document is Non-Sensitive 

DOCUMENT NAME: S/DWM/HLWB/thc1/EBS Observation Audit Report Feb 2001.wpd *See Previous concurrence

OFC HLWB *Tech Editor HLWB HLWB

NAME TCarter thc EKraus Ek NKStablein nks CWReamer cwr

DATE 04/17/01 04/05/01 04/27/01 04/27/01 

OFFICIAL COPY

ACNW: YES X NO Delete file after distribution: Yes No 

1) This document should be made available to the PUBLIC. Yes -thc1 

2) This document is related to the HLW program. It should be placed in the LSS. Yes -thc1 

Letter to R. Milner from C.W. Reamer dated: April 30, 2001
cc:

R. Loux, State of Nevada R. Massey, Lander County, NV

S. Frishman, State of Nevada J. Pitts, Lincoln County, NV

L. Barrett, DOE/Washington, DC M. Baughman, Lincoln County, NV

A. Brownstein, DOE/Washington, DC A. Funk, Mineral County, NV

S. Hanauer, DOE/Washington, DC J. Shankle, Mineral County, NV

C. Einberg, DOE/Washington, DC L. Bradshaw, Nye County, NV

J. Carlson, DOE/Washington, DC M. Murphy, Nye County, NV

N. Slater, DOE/Washington, DC J. McKnight, Nye County, NV

L. Desell, DOE/Washington, DC B. Price, Nevada Legislative Committee

E. Turner, DOE/Washington, DC D. Weigel, GAO

D. Kim, DOE/Washington, DC W. Barnard, NWTRB

S. Gomberg, DOE/Washington, DC D. Bechtel, Clark County, NV

A. Gil, YMPO E. von Tiesenhausen, Clark County, NV

R. Dyer, YMPO L. Lehman, T-Reg, Inc

S. Brocoum, YMPO R. Holden, NCAI

R. Clark, YMPO A. Collins, NIEC

S. Mellington, YMPO R. Arnold, Pahrump County, NV

C. Hanlon, YMPO J. Larson, White Pine County

T. Gunter, YMPO R. Clark, EPA

K. Hess, BSC F. Marcinowski, EPA

D. Krisha, BSC R. Anderson, NEI

S. Cereghino, BSC R. McCullum, NEI

M. Voegele, BSC/SAIC S. Kraft, NEI

S. Echols, Winston & Strawn J. Kessler, EPRI

J. Curtiss, Winston & Strawn D. Duncan, USGS

J. Meder, Nevada Legislative Counsel Bureau R. Craig, USGS

A. Kalt, Churchill County, NV W. Booth, Engineering Svcs, LTD

G. McCorkell, Esmeralda County, NV N. Rice, NV Congressional Delegation

L. Fiorenzi, Eureka County, NV T. Story, NV Congressional Delegation

A. Johnson, Eureka County, NV J. Reynoldson, NV Congressional Delegation

A. Remus, Inyo County, CA S. Joya, NV Congressional Delegation

M. Yarbro, Lander County, NV J. Pegues, City of Las Vegas, NV
U.S. NUCLEAR REGULATORY COMMISSION 

INPUT FOR THE OBSERVATION AUDIT REPORT NO. OARñ01ñ04,

OBSERVATION AUDIT OF THE OFFICE OF

CIVILIAN RADIOACTIVE WASTE MANAGEMENT

OFFICE OF QUALITY ASSURANCE

AUDIT NO. M&OñARPñ01ñ01

ENGINEERED BARRIER SYSTEM (EBS)

PROCESS MODEL REPORT

 /RA/ 04/17/01 /RA/ 04/06/01

Ted Carter Lauren Browning

Projects and Engineering Section Center for Nuclear Waste Regulatory

High-Level Waste Branch Analyses

Division of Waste Management

 /RA/ 04/06/01

Thomas Trbovich

Center for Nuclear Waste Regulatory

 Analyses 

Reviewed and Approved by:

 /RA/ 04/30/01

N. King Stablein, Chief

Projects and Engineering Section

High-Level Waste Branch

Division of Waste Management

Enclosure
1

1.0 INTRODUCTION

Staff from the U.S. Nuclear Regulatory Commission (NRC) Division of Waste Management and

contractors from the Center for Nuclear Waste Regulatory Analyses (CNWRA) observed the

U.S. Department of Energyís (DOEís), Office of Civilian Radioactive Waste Management, Office

of Quality Assurance (OQA), audit of the process and activities that support the Engineered

Barrier System (EBS) Process Model Report (PMR). This audit was conducted on February

20ñ23, 2001, at the Bechtel SAIC Company, LLC (BSC) offices in Las Vegas, Nevada. BSC

became the DOE Management and Operating ( M&O) contractor on February 12, 2001.

Selected Analysis Model Reports (AMRs) supporting the EBS PMR were previously audited on

February 7ñ11, 2000, (OQA Audit No. M&OñARPñ00ñ06), and at that time several of the

documents audited were still in the process of being developed. The purpose of this audit was

to evaluate the implementation of the applicable provisions contained in the OCRWM Quality

Requirements and Description (QARD), DOE/RWñ0333P, Revision 10, by evaluating two

selected AMRs supporting the EBS PMR. Also, the audit evaluated action taken as a result of

the findings and recommendations from the February 2000 EBS audit. The two selected AMRs

of this audit were subjected to a technical evaluation as well as an evaluation to ensure that the

applicable programmatic requirements contained in the QARD and implementing procedures

were met.

The objective of the NRC Observation Team (observers) was to assess whether the previous

and current M&O contractors had properly implementing the provisions contained in the QARD

and the requirements contained in Subpart G, ìQuality Assurance,î to Part 60 of Title 10 of the

U.S. Code of Federal Regulations (10 CFR Part 60). Because of the anticipated DOE submittal

of the Site Recommendation (SR) for a high-level waste repository, the following observation

activities were emphasized: (1) confirming that data, software, and models supporting the SR

are properly qualified; (2) evaluating the progress being made by DOE and contractors in

meeting the data and software qualification goals for the SR; and (3) ensuring the technical

adequacy of the four AMRs within the scope of the OQA audit.

This report addresses the observersí determination of how effective the OQA audit was, and

whether the M&O implemented adequate QARD controls during the AMR development

process. 

2.0 MANAGEMENT SUMMARY

The observers agreed with the audit teamís conclusions, findings and recommendations. The

observers determined that the OQA Audit M&OñARPñ01ñ01 was planned and effectively

implemented. However, the observers were disappointed to note that though previous

observation audits indicated effective corrective measures had been taken with procedural

compliance in the AMR development process, some of the AMRs selected for this evaluation

still indicated discrepancies similar to what had been found during the 2000 audit. This concern

led to the initiation of an Audit Observation Inquiry (AOI) on corrective action escalation detailed

later in this report.

The audit team members were independent of the activities they audited and were

knowledgeable of the quality assurance (QA) requirements and the technical disciplines within
2

the scope of the audit. Those members of the audit team that were formerly part of the Quality

Assurance Technical Support Services and recently had joined BSC had documentation

indicating they were not involved with any of the audited AMR development processes. The

audit team membersí qualifications were reviewed and were found to be acceptable.

3.0 AUDIT PARTICIPANTS

3.1 Observers

Ted Carter Team Leader NRC

Lauren Browning Technical Specialist CNWRA

Thomas Trbovich Quality Assurance Specialist CNWRA

3.2 OQA Audit Team

Don Harris Audit Team Leader OQA/Quality Assurance Technical

Support Services (OQA/QATSS)

Lester Wagner Auditor OQA/QATSS 

Floyd Dove Auditor OQA/QATSS 

Michael Goyda Auditor OQA/QATSS

Chet Wright Auditor OQA/QATSS

Kristi Hodges Technical Specialist OQA/QATSS

Harris Greenberg Technical Specialist Management & Technical Services

David Sassani Technical Specialist Management & Technical Services

Steve Sobkowski Technical Specialist Management & Technical Services

4.0 REVIEW OF THE AUDIT AND AUDITED ORGANIZATION

This OQA audit of the M&O was conducted in accordance with OCRWM Quality Assurance

Procedure (QAP) 18.2, ìInternal Audit Program,î and QAP 16.1Q, ìPerformance/Deficiency

Reporting.î The NRC staffís observation of this audit was based on NRC Manual Chapter

2410, ìConduct of Observation Audits,î dated July 12, 2000.

4.1 Scope of the Audit

The EBS PMR activities and selected AMRs were previously audited on February 7-11, 2000,

and at that time, several of the documents audited were in the process of being developed. 

The audit team conducted a limited-scope, performance-based audit of activities and processes

related to the development of the AMRs supporting the EBS PMR. Audit activities included

evaluation of the EBS PMR, two AMRs, selected software, and associated data. The audit also

included review of the programmatic controls governing the AMRs and technical requirements

contained in the AMRs. Further, the audit evaluated action taken as a result of the findings and

recommendations from the February 2000 EBS PMR audit. 

The preparation of the following two AMRs and the EBS PMR were evaluated by the audit team

and the observers during the audit:

! ANL-EBS-MD-000032, Revision 00, ICN1, ìWater Distribution and Removal Modelî

(E0090)
3

! ANL-EBS-MD-000033, Revision 00, ICN 1, ìPhysical and Chemical Environmental

Abstaction Modelî (E0100)

The evaluations ANL-EBS-MD-000026 and 000027 were limited to verification of the

incorporation of recommendations from audit M&O-AP-00-06.

! ANL-EBS-MD-000026: The recommendations were incorporated in the AMR, Revision

0, ICN 1, satisfactorily.

! ANL-EBS-MD-000027: The recommendations were either incorporated in the AMR

revision or will be addressed by the closure of the open items from the Repository

Design, Thermo-Mechanical Effects Key Technical Issues Resolution Status Report,

Revision 3.

4.2 Conduct and Timing of the Audit

The audit was performed effectively and the audit team demonstrated a sound knowledge of

the applicable M&O and DOE programs and procedures. Audit team members conducted

thorough interviews, they challenged responses, when appropriate, and they effectively

employed their detailed audit checklists. The observers concluded that the timing of the audit

was appropriate for the auditors to evaluate ongoing EBS PMR activities. The audit team and

the observers caucused at the end of each day. Meetings between the audit team and M&O

management (with the observers present) were also held to discuss the current audit status and

preliminary findings.

4.3 Audit Team Qualification and Independence 

The qualifications of the audit team leader and the audit team were reviewed for accuracy and

completeness in accordance with the requirements of Procedure QAP 18.1, ìAuditor

Qualification.î The observersí review included an examination of the training, education, and

experience of the audit team members. The observers concluded that the audit team

members, including the technical specialists, had the necessary expertise and were wellprepared to audit the subject matter in the AMRs.

4.4 Examination of the QA Elements

The OQA programmatic and technical audit activities were conducted simultaneously using

sub-audit teams consisting of one technical specialist and one or more QA auditors. Often

during the audit, certain programmatic aspects of the audited documents were independently

reviewed by an audit team member. The observers determined that the limited-scope audit

focused on the QA elements closely associated with the critical process steps of AMR

development. BSC had initiated a review of all existing procedures and issued a Blue Sheet

Change Notice indicating any changes required in the procedure with regard to activity

responsibility and denoting BSC acceptance of the document. The observers evaluated the

audit teamís review of the following QA elements.
4

4.4.1 APñ2.21Q, ìQuality Determinations and Planning A-+ctivities for Scientific,

Engineering, and Regulatory Compliance Activitiesî

The auditor reviewed the Technical Development Plan and Work Plan for the AMR,

ANLñEBSñMDñ000033, Rev. 01, ìPhysical and Chemical Model.î It was determined that there

was not enough detailed information. This lack of information could result in a technical product

that could not be mapped to specific requirements in either planning document. Because of the

vague requirements, the results of the technical products could not be assured. It was

recommended that APñ2.21Q be revised to establish planning guidance that will result in

sufficient detail to produce a sound technical product. The observers agreed with the

recommendations made in this area. 

4.4.2 APñ3.4Q, ìChange Controlî and APñ3.17Q, ìImpact Reviewsî

These procedures had been accepted by BSC via the Blue Sheet Change Request process. 

The auditor determined that two change requests had been initiated: TCRñT2000ñ0253, on

ANLñEBSñMDñ000032, ìWater Distribution and Removal Modelî and TCRñT2000ñ0315, on

ANLñEBSñMDñ000033, ìPhysical and Chemical Model.î A total of 18 Impact Review Action

Notices had been initiated between the two documents and had been properly completed by the

responsible individuals. No discrepancies were noted nor were recommendations for

improvement made.

4.4.3 APñ3-10Q, ìAnalysis and Modelsî

This procedure applies to activities pertaining to the development, documentation, checking,

review, approval and revision of analyses or models, and the calibration, validation or use of

models to support scientific, engineering, or performance assessment work activities. This

procedure has had significant revisions and modifications made to it during the past 2 years.

Four process-level models identified in the Physical and Chemical Model,

ANLñEBSñMDñ000033, were determined not to be in compliance with the six alternative

validation approaches identified in APñ3.10Q, section 5.3(c).The models identified included: 

a. Gas Flux and Fugacity Model

b. Invert Evaporation Model

c. Microbial Effects Model

d. EBS Colloids Model

A Discrepancy Report was to be initiated for inadequate model validation on these models. The

observers agreed with the deficiency noted in this area. 

4.5 Examination of Technical Activities

The technical specialists on the audit team performed detailed reviews of the technical

adequacy of the AMRs audited. The observers assessed the audit teamís performance of

these reviews and were given an opportunity to perform a review of the technical adequacy of

the documents. Also, the observers were given an opportunity to ask questions during the audit. 

The observers generally agreed with the audit team findings in this area. An AOI was

submitted, however, for reasons discussed in the following paragraphs.
5

4.5.1 AMR No. ANLñEBSñMDñ000033, ìEngineered Barrier System: Physical and

Chemical Environment Model,î Revision 01

The audit team technical specialist assigned to review this AMR was well-prepared to conduct

the audit. The AMR originator and cognizant PMR-development relevant support staff were

available to answer the audit teamís technical questions and provide information about

software, data, and model documentation.

This AMR documents conceptual models for the evolution of physical and chemical

environments in the EBS emplacement drifts. Modelsí output was to be used in modeling the

performance of the EBS, the waste package, and the waste form. However, the audit team

technical specialist pointed out that model output did not fulfill its intended purposes. This was

one of several inconsistencies, identified by the audit team technical specialist, between the

technical work plan (TWPñMGRñMDñ000013) for this AMR and the actual work product. In

response to these shortcomings, the audit team technical specialist recommended that the

planning of this AMR be revised to more clearly document specific work tasks. The audit

observer agrees with this recommendation.

The audit team technical specialist made several other recommendations to improve this AMR.

These included: (1) additional clarification of the model assumptions and justifications,

(2) further explanation of model inputs; (3) more detailed referencing in FEP table 6.8-1;

(4) more detailed referencing in KTI AC table 6.9-1; and (5) more quantitative treatment of

model uncertainties. The observer concurs with all the recommendations made by the audit

team technical specialist.

The audit team technical specialist identified three potential deficiencies with this AMR. The first

potential deficiency is in the area of document traceability/transparency. The audit team

technical specialist identified 40 specific problems in this area, including incorrect reference

citations and tables containing incorrect or conflicting data. The second potential deficiency

with this AMR that was identified by the audit team technical specialist is an incorrect

calculation associated with table 6.3-1. The final potential deficiency noted by the audit team

technical specialist is that four model validations are not in compliance with the requirement of

APñ3.10Q, section 5.3c, as claimed in the document. The observer concurs with the audit

team technical specialist and considers the last one as the most serious potential deficiency.

As indicated above, the audit team technical specialist determined that model output from this

AMR did not fulfill its intended purposes. More specifically, the auditors established that output

from this AMR does not provide input to total system performance assessment or other

process-level models used to support DOEís safety case for the proposed nuclear repository at

Yucca Mountain, NV. There were a number of informal discussions amongst the DOE audit

team and associated technical support staff about whether or not it would be useful to the

Yucca Mountain Project to continue the work in this AMR. During one of these discussions, the

observer noted that several agreements made at the NRC/DOE technical exchange (January

9ñ12, 2001, Pleasanton, CA) on Evolution of the Near Field Environment (ENFE) indicate that

new data and analyses will be presented in the EBS: Physical and Chemical Environment

Model AMR (ANLñEBSñMDñ000033), expected to be available in fiscal year (FY) 2002. The

observer was concerned that if the data and analyses required to fulfill NRC/DOE agreements

are not presented in a FY 2002 revision of the ANLñEBSñMDñ000033 AMR, then the NRC

reviewers would not know where to look for the data and analyses. At the suggestion of the

audit team leader, the observer wrote an AOI regarding this concern.
6

5.0 NRC STAFF FINDINGS

The observers determined that OQA Audit M&O-ARP-01-01 was effective in determining the

level of compliance of M&O activities associated with the subject AMRs. The observers agreed

with the audit teamís conclusion that the OCRWM QA program had been satisfactorily

implemented except, for the identified potential deficiencies. The following sections address the

observers findings. 

5.1 NRC AOIs

The following AOIs were generated during the audit:

a. OARñ01ñ04ñ1

Previous OQA audits of the M&O AMR/PMR development and review processes have

provided both discrepancies and recommendations involving calculations, the check

process, model validation, and software validation. During the observation of this audit,

it appears from the auditor discussions and caucus meetings that similar discrepancies

and recommendations are being made involving the same conditions as previously

noted. A quick review of a DR corrective action request summary search of these

discrepant conditions appears to indicate 16 documents involving similar conditions

were identified, during 2000 and 2001, of which 12 documents have been closed,

indicating acceptable response and verification. What is the process for identifying

ineffective corrective action, improper implementation of corrective action, or lack of

training and determining if more severe corrective action notices are warranted?

b. OARñ01ñ04ñ2

Several agreements made at the NRC/DOE Technical Exchange (January 9ñ12, 2001,

Pleasanton, CA) on ENFE indicate that new data and analyses will be presented in the

EBS: Physical and Chemical Environment Model AMR (ANLñEBSñMDñ000033),

expected to be available in FY 2002. The following NRC/DOE agreements point

specifically to the FY 02 revision of this AMR: ENFE.2.04; ENFE.2.06; ENFE.2.08;

ENFE.2.11; ENFE.2.13; and ENFE.2.18. ENFE.2.05 and ENFE.2.17 also point to this

AMR, although it states the information can be provided in other documents as

appropriate. During the M&OñARPñ01ñ01 audit of ANLñEBSñMDñ000033, Rev. 01, in

Las Vegas, NV (February 20ñ23, 2001), however, audit team members questioned the

usefulness of producing additional revisions of this AMR. If data and analyses required

to fulfill NRC/DOE agreements listed above are not presented in a FY 2002 revision of

the ANLñEBSñMDñ000033 AMR, where will this information be presented?

5.1.1 AOI Response

Subsequent to the audit, the NRC received a response to AOI OAR-01-04-1. In the response,

OQA describes the current process for identifying and managing conditions adverse to quality. 

Further, the response indicated that two Suspect Trend Investigation Reports were issued to

investigate conditions similar to those identified in the AOI in order to determine if more severe

corrective action is required. This response addresses the concern of OAR-01-04-1 and is

found to be acceptable based on reference letter from DOE to NRC, ìU. S. Nuclear Regulatory

Commission (NRC) Audit Observer Inquiry,î dated April 19, 2001.
7

5.2 Open NRC AOIs

The following AOIs were generated during the observation of DOEís Audit No. M&O-ARP-01-02

of the Unsaturated Zone Flow and Transport Model Process Model Report (NRC Observation

Report No. OAR-01-03, dated March 5, 2001):

a) AOI No. M&O-APR-01-02-1, dated February 9, 2001, was written to identify an observer

inquiry for ANL-NBS-HS-00032. The AOI states: ìArbitrary upper-bound vegetation

cover percentages and bedrock root-zone thicknesses were assigned: 20% and 2.0 m

for the modern climate; 40% and 2.5 m for the monsoon climate and 60% and 3.0 m for

the glacial transition climate. A more detailed discussion of the assumed values is

needed since the values may be excessive, thus leading to an over-prediction of ET and

under-prediction of shallow infiltration. (Refer to U.S. NRCís Observation Audit Report

No. OAR-00-04).î 

b) AOI No. M&O-APR-01-02-2, dated February 9, 2001, was written to identify an observer

inquiry for ANL-NBS-HS-00032. The AOI states: ìThe instantaneous flow routing (IFR)

method assumes that the duration of surface-water flow at Yucca Mountain is less than

24 hours and episodic in nature. This assumption is the basis for not using time-steps

smaller than 24 hours when performing surface-water flow routing and calculating daily

net infiltration. Please provide the NRC with adequate justification. (Refer to U.S.

NRCís Observation Audit Report No. OAR-00-04).î 

c) AOI No. M&O-APR-01-02-3, dated February 9, 2001, was written to identify an observer

inquiry for ANL-NBS-HS-00032. The AOI states: ìAn implicit assumption of the

distribution-parameter water-balance model is that capillarity is not an important

component of UZ flow processes for the objective of estimating annual average

infiltration rates in the semi-arid climate of Yucca Mountain. The INFIL ver. 2.0 contains

both the distribution-parameter water-balance module and the Richards module and

could readily be used to confirm the basis for this assumption for a small scale region. 

The NRC recommends that the assumptions in the distribution-parameter water-balance

model be validated by comparison against a numerical Richards equation-based code to

assure that mean annual shallow infiltration estimates are not under-predicted. (Refer

to U.S. NRCís Observation Audit Report No. OAR-00-04).î 

d) AOI No. M&O-APR-01-02-4, dated February 9, 2001, was written to identify an observer

inquiry for ANL-NBS-HS-00032. The AOI states: ìThe work upon which this model is

based (Flint et al., 1996, Conceptual and Numerical Model of Infiltration at Yucca

Mountain) is unqualified. (See OCRWM QA Audit Report M&O APR-00-04)(p. 9). Was

information used to support conclusions made in the Infiltration AMR? If yes, describe

how the Flint et al. (1996) data was qualified and assumptions verified. NRC requests

additional information and details. (Refer to U.S. NRCís Observation Audit Report No.

OAR-00-04).î