ML20214E407

NRC Generic Technical Position on Borehole & Shaft Sealing of High Level Nuclear Waste Repositories

ML20214E407
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Issue date:	02/28/1986
From:	NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
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ML20214E394	List: ML20214E391 ML20214E399 ML20214E404 ML20214E407
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, U.. S. NUCLEAR REGULATORY COMISSION 5

GENERIC TECHNICAL POSITION BOREHOLE AND SHAFT SEALING 4

0F HIGH-LEVEL NUCLEAR WASTE REPOSITORIES i

COMPILED BY

, ENGINEERING BRANCH j . DIVISION OF WASTE MAM.GEMENT

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February 1986

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8403260167 960229

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TABLE OF CONTENTS

?^92 1.0 Introduction............................................... 1 2.0 Re g u l a to ry F ramewo r k. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2.1 Design Criteria....................................... 2 2.2 Verification of Design................................ 3-4 2.3 Submission of Information on Sealing to NRC...................................... 5 2.4 Additional Regulatory Cri teria. . . . . . . . . . . . . . . . . . . . . . . . 6 3.0 Discussion of Sealing Issues............................... 6 3.1 Long-Term Stability of Sea 1s.......................... 7 3.2 Design of Shtfts and Boreholes with Considerations for Long-Term Sealing............................... 7 3.3 Installation Procedures for Sealing................... 9 3.4 Impact of Waste Induced Thermal Loading on Sealing.......................................... 9

. 3.5 Compatibility of Seals to Host Ror.k. . . . . . . . . . . . . . . . . . . 10 3.6 Achieving Low Hydraulic Conductivities in the Sealed Area......................................... 10 4.0 Information Needed to Assess Borehole and Shaft Sealing Issues....................................... 11 4.1 Rock Characteristics.................................. 11 4.2 Seal Material Characteristics......................... 12 4.3 Sealing of Rock Fractures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.4 Design. Excavation, and Cor.struction of Shafts and Boreholes....................................... 13 4.5 Installation of Borehole and Shaft Seals.............. 14 5.0 Key Design Measures for Borehole and Shaft Seals........... 15 6.0. In-Situ Testing and Performance Confirmation Program....... 16 7.0 Quality Assurance for the Repository Sealing Program.. . .. . . 16 8.0 Summary and Technical Position............................. 17 References................................................. 18-20

1. 0 Introduction-Construction authorization and the licensing of a high-level waste repository involve assessing whether the geologic setting and the engineered barrier system and the shafts, boreholes, and their seals will perform concurrently and compatibly at a particular site to assure that releases of radionuclides to the accessible environment conform to Environmental Protection Agency standards. Construction of shafts and boreholes in geologic media alters the natural setting and may create preferential pathways for groundwater flow and consequently migration of radionuclides. Since these pathways could adversely affect the isolation capabilities of the repository over the long term, the NRC has required

'in 10 CFR Part 60 that boreholes and shafts be sealed at permanent closure of the repository. This document provides general guidance for identifying what types of information should be developed, and identifies issues and points of concern about borehole and shaft seals that should be addressed prior to the submittal by DOE of a license application for construction authorization.

The sealing of boreholes and shafts is a site specific problem and will ultimately'be based on site specific information. However, there are generic concerns in sealing nuclear waste repositories as well as site specific concerns. Because of this, the staff has been mindful of the need to avoid being overly prescriptive. Therefore, this document identifies those concerns which are potentially applicable to any saturated media site that may be selected. The NRC revised 10 CFR 60 to apply to a repository in the unsaturated zone. This technical position is presently written for repositories in saturated media.

However if sealing is needed in the unsaturated zone, then the guidan e in this GTP is applicable. It is expected that the Department of Energy (00E) will use this guidance to prepare detailed plans for borehole and shaft sealing studies and will submit appropriate documentation in the Site Characterization Plan. The SCP should identify those methods to be used by DOE to explicitly address the issues and concerns raised in this technical position.

Section 2 of this GTP contains the regulatory framework. Section 3 identifies specific issues and points of concern that should be explicitly considered and addressed in developing an adequate program for borehole and shaft sealing. Sections 4, 5, 6, and 7 identify information that the staff presently considers essential in establishing the acceptability of any sealing system.

2. 0 REGULATORY FRAMEWORK This Generic Technical Position is guided by the technical criteria of the NRC rule, 10 CFR Part 60 and supplements (Regulatory Guide 4.17  ;

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entitled " Standard Format and Content of Site Characterization Plans For High Level Waste Geologic Repositories").

The NRC regulatory framework for borehole and shaf t sealing consists of the following four parts: 1) design criteria for the seals,

2) performance confirmation requirements for the seal design

3) submission of information on' sealing to the NRC, and 4)' additional regulatory criteria concerning sealing of boreholes and shafts. It should be noted that the criteria for borehole and shaft seals do not apply to. openings in the underground facility (e.g., they do not include rooms, drifts, tunnels, or waste emplacement boreholes which are part.of I the engineerea barrier system).

1 2.1 Desian Criteria The unique requirements (e.g., containment and isolation of high level waste) of a repository demand the criteria governing the design of shaft and borehole seals to be more stringent than existing criteria (e.g.,

state and local requirements) for routine plugging of boreholes.

Boreholes, in most states,- are routinely sealed as required, when they are no longer in use. Sealing technology to meet these state requirements exists in the petroleum industry. However, there are several distinct differences between the current petroleum industry sealing technolog.y and technology required for the sealing of opening.s in a geologic repository. The basic concern for a repository is to limit potential preferential pathways to the accessible environment. The technical rule 10 CFR Part 60 requires the DOE to design the seals to meet the following requirements:

$60.134 Design of seals for shafts and boreholes (a) General design criterion: Seals for shafts and boreholes shall be designed so that following permanent closure they do not become pathways that compromise the geologic repository's ability to meet the performance objectives over the period ,

following permanent closure.

(b) Selection of materials and placement methods: Materials and i placement methods for seals shall be selected to reduce, to the extent practicable. (1) the potential for creating a preferential pathway for groundwater, or (2) radioactive waste

~ . migration through existing pathways.

Theperformanceobjectivesreferencedabovereferto60.112,and60.113 ,

of 10 CFR Part 60. In particular, 60.112 states:

$60.112 Overall system performance objective for the geologic repository after permanent closure 109.4/DT/85/05/01/0 2

The geologic setting shall be selected and the engineered barrier

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system and the shafts, boreholes and their seals shall be designed to assure that releases of radioactive materials to the accessible environment folicwing permanent closure conform to such generally applicable environmerital standards for radioactivity as may have been established by the Environmental Protection Agency with respect to both anticipated processcs and events and unanticipated processes and events.

The other applicable performance objective is as follows:

560.113 Performance of Particular Barriers After Permanent Closure (b)(2) The geologic repository shall be located so that pre-waste emplacement groundwater travel time along the fastest path of likely radionuclide travel from the disturbed zone to the accessible environment shall be at least 1,000 years or such other travel time as may be approved or specified by the Commission.

(b) On a case-by-case basis, the Commission may approve or specify some other radionuclide release rate, designed containment period or pre-waste emplacement groundwater travel time, provided that the overall system performance objective, as it relates to anticipated processes and events, is satisfied.

Among the factors that the Commission may take into account 3 are:

(1) Any generally applicable environmental standard for radioactivity established by the Environmental Protection Agency; (2) The age and nature of the waste and the design of the underground facility, particularly as these factors bear upon the time during which the thermal pulse is dominated by the decay heat fr:om the fission products; (3) The geochemical characteristics of the host rock, surrounding strata and groundwater; and (4) Particular sources of uncertainty in predicting the performance of the geologic repository.

-(c) Additional requirements may be found to be necessary to satisfy theoverallsystemperformanceobjectiveasitrelatesto unanticipated processes and events.

2.2 Verification of Design 4 i

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3 The technical rule 10 CFR Part 60 requires the design of a repository to permit the following:

Performance Confirmation Requirements

$60.137 General requirements for performance confirmation The geologic repository operations area shall be designed so as to permit implementation of a performance confirmation program that meets the requirements of Subpart F of this part.

Subpart F-Performance Confirmation Program

$60.140 General Requirements

'(a) The performance confirmation program shall provide data which indicates, where practicable, whether-(1) Actual subsurface conditions encountered and changes in those conditions during construction and waste emplacer.ent operations are within the limits assumed in the licensing review; and (2) Natural and engineered systems and components required.for repository operation, or which are designed or as'sumed to operate as barriers after permanent closure, are functioning as intended and anticipated.

(b) The program shall have been started during site characterization and it will continue until permanent closure.

(c) The program shall include in situ monitoring, laboratory and q field testing, and in situ experiments' as may be appropriate toaccomplishtheobjectiveasstatedabove.

(d) The program shall be implemented so that:

(1) It does not adversely affect the ability of the natural and engineered elements of the geologic repository to meet

theperformanceobjectives.

(2) It provides baseline information and analysis of that information on those parameters and natural processes pertaining to the geologic setting that my be chang.ed by t

site characterization, construction, and operational activities.

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I (3) It monitors and analyzes changes from the baseline conditions of parameters that could affect the performance of a geologic repository.

(4) It provides an established plan for feedback and analysis of data, and implementation of appropriate action.

S60.142 Design testing (a) During the early or developmental stages of construction, a program for in situ testing of such features as borehole and shaft seals, backfill, and thermal interaction effects of the waste packages, backfill, rock, and groundwater shall be conducted.

(b) The testing shall be initiated as early as practicable.

(c) A backfill test section shall be constructed to test the effectiveness of backfill placement and compaction procedures against design requirements before permanent backfill placement is begun.

, (d) Test sections shall be established to test the effectiveness of borehole and shaft seals before full-scale operation proceeds to seal boreholes and shafts.

The foregoing requirements identify the applicable portions of 10 CFR ,

Part 60 for borehole and shaft seals for a high-level nuclear waste -

repository. ,

- 2. 3 Submission of Information on Sealing to NRC The Standard Format and Content of Site Characterization Plans for High-Level Waste Geologic Repositories (NRC Regulatory Guide 4.17) recommends that the DOE include in their Site Characterization Plans the following data on sealing shafts and boreholes.

Sealing of Shafts, Boreholes, and Underground Openings, Section 6.4

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Describe the proposed treatment of the disturbed section of rock around openings and excavated surfaces. Describe proposed design measures to control groundwater movement into the facility. Provide laboratory and field data when available and inferred site conditions on which the selection of the treatment measures was based. Describe the proposed design for the sealing of boreholes and shafts. Provide laboratory and field data and inferred site conditions on which the design was based. Provide the thermal, i

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mechanical, chemical, and hydrologic properties of proposed sealing materials.

This data and information about the planned design will be the basis from which the NRC will make findings in the license reviews on sealing requirements. By the time the DOE submits the Safety Analysis Report as part of their License Application, the DOE should have developed, an assessment of the Site as required by, 10 CFR Part 60, S60.21(c)1(ii)D. The assessment shall contain "the effectiveness of engineered and natural barriers, including barriers that may net be themselves a part of the geologic repository operations area against the release of radioactive material to the environment. The analysis shall also incl'ude a comparative evaluation of alternatives to the major design features that are important to waste isolation, with particular attention to the alternatives that would provide longer radionuclide containment and isolation." This would include the ' effectiveness of the seals' by l themselves and as part of the overall performance of the repository.

j From.this information, a licensing decision should be possible if

( the D0E has supplied the necessary information as described in this

l. technical position.

2.4 Additional Regulatory Criteria ,

7 DOE will also adhere to technical criteria concerning the siting and use of man-made openings as follows:

$60.10 Site Characterization (d) The program of site characterization shall be conducted in accordance with the following:

(1) Investigations to obtain the required information shall be conducted in such a manner as to limit adverse effects on the long-term performance of the geologic repository to the extent practical.

.(2) . Subsurface exploratory drilling, excavation, and in situ

', testing before and during construction shall be planned

^and coordinated with geologic repository operations area

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3 design and construction.

3.0 DISCUSSION OF' SEALING ISSUES

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The following are issues involving the sealing of shafts and boreholes which are currently viewed by the NRC as the most critical sealing issues related to repository performance.

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These issues are based on licensing criteria for sealing and address areas where the available technical information needs to be developed on a site specific basis or technoloqy is insufficient to have adequate confidence that the licensing criteria can be met. These areas have also been identified in current sealing studies as areas which need further investigation (D'Appolonia, 1978; D'Appolonia, 1980a; D'Appolonia, 1980b; Taylor. 1980).

3.1 Long-Term Stability of Seals The performance of the entire plug or seal system for a repository must be adequate over a time span which exceeds any reasonable testing period.

Therefore, alternative analytical methods must be utilized, based on laboratory and field data, to adequately characterize the integrity and adequacy of the seals over long time periods. Tests and analyses should be performed to show that the seal system will perform for long time periods under conditions similar to those which can reasonably be expected at a particular site. These methods should include the following:

Analytical models, based on valid field and laboratory data, that analyze the seal system's performance over long time periods; Analog studies of proposed sealing materials and their longevity in similar environments to the repository, taking into account past experience with such materials (Roy. 1982);

bentonite / clay materials in natural environments old cementitious structures, cementitious materials in nature bituminous and asphaltic deposits Accelerated laboratory testing of sealing materials in simulated repository environments; -

Prelicensing and pre-closure in situ field testing of sealing materials:

Theoretical geochemical stability analysis of materials over the expected lifetime of the seal system, based on repository environment information.

applicable standards such as ASTM E632-81 geochemical phase studies 3.2 Design of Shafts and Boreholes with Consideration for Lona-Term Sealina 109.4/DT/85/05/01/0 7

... . _ __ _ m .

The design and excavation of the shafts and borehr,les at the repository site should be accomplished while considering the effects on long-term stalability. Sealing considerations should Influence the pretreatment methods, excavation techniques, and lining of the openings (Kelsall, 1983).

Preliminary evaluations of damaged rock zone characteristics have been done by combining analytical assessments with a review of previous investigations (Kelsall, 1982). Although this work is a step in the right direction, it is entirely hypothetical and cannot, at present, be <

quantified or supported by any experimental evidence including site specific parameters. The data base for characterizing the daniage zone due to borehole drilling is also limited, but more complete based on current investigations (Mathis and Daemen, 1982 Lingle, 1982). The amount and degree of damage incurred during excavation and drilling could be an influencing factor in the effectiveness of sealing. It is understood that if the rock is very strong (relative to the in situ stress field), and if the excavation does 'not induce damage, the stress redistribution around the opening may not necessarily cause an increase in the permeability of the rock (Hoek, 8rown, 1980). If this could be demonstrated, this' question would be resolved for that particular site.

However, if the rock units become extensively fractured by either excavation damage or stress redistribution, the flow of groundwater and subsequent transport of radionuclides could occur through the fractured rock and around the emplaced seal. Therefore, it is important to understand the mechanical characteristics of the zone surrounding the ^

opening on a site specific basis. It should be determined whethdr damage to the rock units has occurred, the extent of the damage, and whether trie damage could circumvent the purpose of the seal system l The effects of liners and casings on the sealability of the openings .

should be considered. The difficulty and adequacy of sealing cased boreholes or removing the casing needs to be assessed. This is also true with shafts. If the liner is to be removed at permanent closure, the effects of removing the liner should be assessed. If the liner is left in place, the impact of liner deterioration on the performance of the seal system should be assessed.

Areas of concern regarding the affect of borehole and shaft design on long term sealing include:

Development of methodology and equipment to adequately determine extent of damaged rock zoile (Montazer,1983);

• Selection of excavation and drilling techniques that. inflict minimal _ damage (fracturing) to the rock unit's:

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Quality control of excavation and drilling procedures to assure minimal damage to the rock units; Affects of liners / casings on long-term sealability or assessment of effects of removing the liners / casings; Selection and emplacement of grout between the liner and rock units taking into account long-term sealing considerations; Protective excavation, drilling, and reinforcement measures to minimize rock relaxation; Remedial measures to be taken in case excessive excavation and drilling damage has occurred; Installation of grout curtains and cut-off collars; Effects of stress redistribution resulting from the thermal pulse and subsequent cooling.

3. 3 Installation Procedures for Sealing The seal emplacement techniques used in sealing shafts and boreholes could be a controlling factor in seal performarice (Fernandez,1976; 0'Appolonia,1979). Reliability must be obtained in the methods and equipment used for the installation of the seal materials. The.

reproducibility of results using emplacement methods and equipment should also be demonstrated. Demonstration should include field testing of emplacement methods and monitoring of performance of the emplaced seal-over time (Christensen, 1979: Statler,'1980; Rhoderick, 1981; Burkes, 1983). Areas of concern regarding seal installation procedures include:

Remedial measures for preparing the opening for sealing (e.g.,

shaft wall cleaning of residual mud, if mud is used during shaft sinking);

Development of technically feasible procedures for placement of seal materials; Adequate quality control to assure proper placement of seals; Field testing of installation procedures.

3.4 Impact of Thermal Loading on Seals The thermal loading caused by the emplaced waste on the borehole and shaft seals may damage the seal system (D'Appolonia, 1980a; D'Appolonia, 1980c). There must b'e confidence that the seal system will perform 109.4/DT/85/05/01/0 9

adequately under adverse conditions that result from the elevated temperatures which will occur in the repository. Consideration should be given to:

Chemical stability of seal materials at elevated temperatures; Changes in the stress field of sealed area caused by changes in temperature; Effects on bond interfaces due to differences in expansion caused by thermal loading of seal materials, liner, and wall rock; Affects of vertical uplift (if any) of the overlying stratigraphic units due to the thermal loading of the repository on the sealing system, coupled with potential long term settlement over excavated waste storage areas.

3.5 Compatibility of Seals to Host Rock The compatibility of the physical and chemical characteristics of the seal material and the host rock is an important consideration in seal

. design (D'Appolonia, 1980a). Although incompatibility by itself may not be detrimental to the seal system, incompatibility could result in seal deterioration by chemical attack or physical failure which could result in failure of the seal system. The site specific data of the host rock should be used to develop the seal design for each repository.

Important parameters to consider include:

Physical / mechanical characteristics - compressive strength, shear strength, creep, stress field, hydrologic data (pressures ,

and flow rates), lithology, rock fractures; Chemical characteristics - mineralogy, phase changes, pH, Eh, groundwater chemistry, rock groundwater interaction, seal grounawster interaction, seal rock interaction.

3.6 Maintaining Low Hydraulic Conductivities in the Sealed Area The borehole and shaft sealt are emplaced to reduce, to the extent practicable, the potential for creating a preferential pathway for groundwater or radioactive waste movement. This will mean designing and emplacing a seal that produces a hydraulic conductivity in the seal zone which is as low or at least approaches the hydraulic conductivity of the undisturbed host rock mass. in most, but not necessarily all rock types under consideration for repositories, this will mean emplacing a seal with a low hydraulic conductivity (O'Appolonia, 1980a). Furthermore,  ;

this will be controlled by the site specific rock type and is therefore a 109.4/DT/85/05/01/0 10

site specific issue. For example, the hydraulic conductivity requirements for seals in a salt repository may be different from those for a basalt repository. The low hydraulic conductivity area under consideratic+ would include the disturbed rock zone, the interfaces between the hast rock, liner (if any), and the seal, and the seal itself.

Areas of concern regarding this issue include:

characterizing and sealing (if necessary) the damaged rock zone surrounding the borehole or shaft; and developing seal materials and a seal oystem with low hydraulic conductiv1ty.

4.0 INFORMATION NEEDED TO ASSESS THE BOREHOLE AND SHAFT SEALING ISSUES The requirements set forth in 10 CFR Part 60.for borehole and shaft sealing were established to assure that openings from the surface into the host rock and tie repository would be sealed in such a way as to assure the isolation capabilities of the host rock. The following is a compilation of the information on borehole and shaft sealing the s'taff deems necessary to make findings in the license reviews. Tiiis compilation is a generic listirig of information needs presently considered applicable. Information needs will vary from site to site due to site specific conditions. These information needs should be discussed in the SCP.

4.1 Rock Characteristics The following are examples of host rock data needed by the NRC to adequately assess the design of the sealing system for compatibility with the rock units and long-term stability of the sealing system (Koplik, '

.Pentz, 1979):

Geological data, including 11thology, rock fractures, and competence of strata (or a stratum);

In situ or ambient stress field and stress concentration factors to assist in determining necessary plug material strength; .

Extent of fracturing (if any) around openings that must be sealed (both natural .and excavation induced fracturing);

Characteristics of discontinuities (e.g., rough versus smooth surfaces) and discontinuity fillings should be -identified; -i 109.4/DT/85/05/01/0 11

Mechanical rock properties, including compressive strengths, shear strengths, modulus of elasticif,y, creep characteristics and thermal' properties; Hydrological data that identify porosity and hydraulic conductivity (vertical and horizontal) of each strata; and Geochemical data, including groundwater chemistry and rock groundwater interaction.

4.2 Seal Material Characteristics The materials used for borehole and shaft sealing should have characteristics that will ensure compatibility with the host rock and groundwater chemistry as well as contribute to the isolation and containment of radionuclides (D' Appolonia,1sti0c). The characteristics of the seal materials needed to meet the perfornance criteria of 10 CFR Part 60 should be identified so that appropriate materials can be designed (Buck, 1982). Considerations for' seal material selection should include:

Chemical properties sorptivity alteration and/or stability of material in host rock groundwater environment Hydraulic properties

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hydraulic conductivity and porosity of seal material hydraulic conductivity and porosity of seal-host rock interface Mechanical properties clastic, and creep behavior of the seal material tensile and compressive strengths of the seal material tensile and shear strengths of the bond between seal .

mater'sl and host rock expansion (for cementitious materials) and swelling (for earthen materials) of seal material Thermal properties differential thermal expansion

differential thermal conductivity differential thermal diffusivity thermal stability of the mineral' scomprising the sealing material 4.3 Sealing of Rock Fractures 109.4/DT/85/05/01/0 12

-- . _ - - .- . _ - ~ . . _ __-

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The amount of effort needed to seal the fractures surrounding the openings will be dependent on the original state of the rock' units and the amount of damage incurred during excavation and consequent stress

- relaxation. The affected zone must be characterized and assessed to determine the amount, if any, of sealing necessary to make the fractured zone. perform in~an acc'ptable e fashion (Taylor, 1980). -Considerations for sealing of rock fractures should include:

Effectiveness of methods used to determine the nature and i extent of the damaged zone (if any) in the rock units;

, Characteristics of rock units to be sealed:

Type and suitability of sealing material to be used, and its

. expected in situ properties (strength, shrinkage and swelling, -

set-up time, etc.);

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• Effectiveness of methods for placement of sealing material, expected cperating pressures, temperatures, and depths of penetration of the sealing material; and Effectiveness of methods to determine amount of success of sealing the fractures.

4.4 Design. Excavation, and Construction of Shafts and Boreholes It is important in the design of the repository openings to consider long-term sealing capabilities. The desi f of the opening.s will. be site specific (i.gn, e.. excavation, depth. rock type, and use construction and ..

extent of linings or' casings, grouting techniques). However, the '

. information needed to adequately assess the impact of the openings on repository performance is basically generic. The following should be addressed:

Quality assurance program for excavation and construction of openings; Provisions to seal strata at specific locations to control 4 inflow of water and gas, and stabilize zones of weak rock; j

• ~

Provisions in shaft design, excavation, and construction for: $

. 1) effects of stress orientations, 2) minimizing. extent of -

- fracturing due to excavation and stress relaxation, and 3) +

effects of ground movements. including bending, buckling. 1:

compression, and shear;  ;

4 1

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Provisions for the use of liners / casings, including liner / casing design, installation procedures, long-term stability, compatibility with repository seal materials; Method and emplacement techniques for sealing of the annulus between the liner / casing and the host rock; ~

Effectiveness of methods for demonstration of the integrity of seal between liner / casing (if left inplace) and host rock; and Provisions made for installation of permanent seals.

4.5 Installation of Borehole and Shaft Seals The design and installation of borehole and shaft seals must be developed using reproducible data and test methods with adequate quality assurance.

Relisbility must be obtained in the methods, procedures'and equipment used for the installation of the seal materials. The informatioil on installation of borehole and shaft seals needed by the NRC to make findings in the license review includes:

Maxirnum water pressure and pressure gradient across or through the seal for which the seal should be designed; Quality control for the installation of the seals; Procedures to be used for determining adequacy of sealing the fractured rock; Procedures used for field testing the proposed seal, with appropriate performance monitoring; Procedures to be used for determining the in situ quality of the seal, including its strength and hydraulic conductivity; Methods for assessing seal performance; To the extent possible, location and description of all

- abandoned openings; Assessment of the effects of the damaged rock zone, and liners / casings on sealability of the openings; Procedures, when applicable, for removing loose rock and for cleaning and preparing the excavation face for sealing; 109.4/DT/85/05/01/0 14 L _

Complete records of drilling operations, including identification of areas with poor core recovery, fractured areas, drilling fluid loss:

Geological data including lithology, strata competency, rock physical properties, hydrological characteristics, location of gas flows, chemical and thermal environment for sealing; Seal design and construction procedures, including methods of seal emplacement.

5.0 KEY DESIGN MEASURES FOR BOREHOLE AND SHAFT SEALS The concept of a geologic nuclear waste repository is based on a series of barriers, engineered and natural, between the high-level nuclear waste and the accessible environment. Each barrier would' contribute to the overall performance of the repository. The performance allocated to a

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particular barrier is greatly dependent upon the design features and site characteristics. However, some key design measures can be established generally for the performance of the borehole and shaft seals so that sufficient confidence can be acquired to make a licensing decision.

. These key design measures are based on available information and studies.

If DOE through performance assessments and identification of the performance criteria for the seal system, determines that alternative key design measures should be used, these alternatives should be identified to the NRC staff. DOE has the burden of demonstrating that isolation and containment of the radionuclides will not be compromised by the alternative key design measures. The staff has determined that the key i design measures which should be attained by the seal system include: 4 As part of the overall system, the EPA Standard set for radionuclide releases from nuclear waste repositories should not be exceeded:

Achieve hydraulic conductivities in the sealed zone as low as

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or at least approaching that of the rock units mass, or as low as can be reasonably achieved and still not compromise the repository performance; or achieve a retardation of 4 radionuclides which at least approaches that of the host rock l mass; a Achieve chemical and physical compatibility and stability with the rock unit and groundwater chemistry, or, if alterations occur to the original seal characteristics, these alterations will not compromise the seal system; and 4

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b i

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Achieve ability to adequately and confidently assess seal performance for the life of the repository.

6.0 IN-SITU TESTING AND PERFORMANCE CONFIRMATION PROGRAM The in situ testing and performance confirmation program will be conducted by the DOE to confirm the parameter valves used in the design in meeting the key design measures set forth in this position paper. 'The NRC has prepared a GTP entitled "In Situ Testing During Site Characterization for High-Level Nuclear Waste Repositories,"

December 1985. The Performance Confirmation Program will start during i

Site Characterization and shall include in situ nionitoring, laboratory and field testing, and in situ experiments, as may be appropriate, (10 CFR Part 60.140(b. c). It is understood'that during this period, it is possible that some tests may give results that are below the values needed for the key design measures. This may be due to the lack of I established procedures in this area or the use of state-of-the-art

( techniques. However, prior to license application, the DOE should have

! the capability of verifying, wit.h preliminary results of in situ tests.

that the key design measures discussed in this position paper can be met.

Alternatively, DOE may decide to modify the design based on the results of the performance confirmation tests. The program should establish

1) the effectiveness of emplacement equipment arid methods, 2) the effectiveness of testing instrumentation, 3) the effectiveness of the seal system (sealed plug / formation system), including plug / hole l interface. 4) diagnosis of failures or problem areas in the integrated system. 5) reliability of seal subsystems and the overall system, and ,

6) reliability of seal system under extreme or accelerated conditions

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(Fernandez, 1976).

i 7.0 QUALITY ASSURANCE FOR THE REPOSITORY SEALING PROGRAM The NRC has set forth in 10 CFR 60 Subpart G, the requirement to implement a quality assurance (QA) program for the de' sign and characterization of barriers required to. satisfy.the performance i objectives for the period of permanent closure. Guidance for the i~ preparation and implementation of a QA program is provided by the NRC in Appendix 8 of 10 CFR 50. The NRC has prepared a Final Review Plan entitled " Quality Assurance Programs for Site Characterization of I High-Level Nuclear Waste Repositories " June 1984. DOE is therefore l required to-implement a QA program for all activities involved in the design, development,' construction, testing, and test monitoring of borehole and shaft seals. This would include laboratory research and development, performance assessment models, field testing (including

.in-situ testing), excavation and construction of the shafts and boreholes, installation of the seals, and monitoring of the seal peiformance during the performance confirmation period.

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8.0

SUMMARY

OF TECHNICAL POSITION The DOE is required by 10 CFR Part 60 to seal boreholes and shafts at permanent closure of a nuclear waste repository. Further, the DOE is required to design the seals so that following permanent closure, they do not become pathways that will compromise the ability of the geologic repository to meet the performance objectives. In addition, the DOE is required to select materials and placement methods for seals to reduce, to the extent practicab'se (i) the potential for creating a preferential pathway for groundwater; or (ii) radioactive waste migration through existing pathways.

The design of borehole and shaft seals should be based on proven technicai knowledge and capabilities, and performance assessments of the sealing system as 'part of the overall repository system. Changes in the design due to changes in either of the above may occur throughout the timeframe of sealing studies. Sensitivity analyses as well as sound engineering judgement should be utilized in the sealing program to establish the importance and amount of work necessary in resolving sealing issues at a particular site. However, other work in the sealing program such as materials studies, equipment development, placement techniques, etc. should not be delayed or eliminated based solely on these sensitivity analyses. These analyses will utilize a data base with high uncertainties and therefore may give an inaccurate indication of the importance of each component in the repository system. Such a determination as to the importance of each subsystem can be made after the Site Characterization Program has been completed when a data base with a higher level of confidence can be utilized.

An adequate program for borehole and shaft seal development should include development of design criteria, laboratory and field testing of materials, equipment, and placement techniques for seals " verification program of seal performance " quality assurance program for sealing studies, and methods for integration of the sealing program to other activities, such as excavation and construction of the underground ,

openings.

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References

1. Buck, A. D., and Mather, K. 1982, " Grout Formulations for Nuclear Waste Isolation," ONWI-413, U. S. Army Engineer Waterways Experiment

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Station, Vicksburg, Mississippi.

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2. Burkes, J. P., and Rhoderick, J. E., 1983, " Petrographic Examination of Bell Canyon Tests (BCT) 1-FF Field Grouts Over'a Three-Year Period," SAND 83-7115, U. S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi.

3. Christensen, C. L. 1979, " Test Plan, Bell Canyon Test WIPP Experimental Program, Borehole Plugging," SAND 79-0739, Sandia National Laboratories, Albuquerque,New Mexico.

4. D'Appolonia Consulting Engineers, Inc., 1978, " Development of Plan and Approach for Borehole Plugging Field Testing," ONWI-3, prepared for Office of Nuclear Waste Isolation, Columbus, Ohio.

5. D'Appolonia Consulting Engineers Inc., 1979, "The Status of Borehole Plugging and Shaft Sealing for Geolog. ic Isolation of Radioactive Waste," 0NWI-15, prepared for Office of Nuclear Waste Isolation, Columbus, Ohio.

6. D'Appolonia Consulting Engineers Inc., 1980a, " Repository Sealing Design Approach - 1979," ONWI-55, prepared for Office of Nuclear Waste Isolation, Columbus, Ohio.

7. D'Appolonia Consulting" Engineers Inc., 1980b, " Repository Sealing Field Testing Workshop proceedings," ONWI-239, prepared for Office of Nuclear of Waste Isolation Columbus, Ohio.

8. D'Appolonia Consulting Engineers, Inc., 1980c, " Repository Sealing:

Evaluations of Materials Research Objectives and Requirements,"

0NWI-108, prepared for Office of Nuclear Waste Isolation, Columbus, Ohio.

9. Fernandez, R., 1976, " Borehole Pluqqing by Compacting Process, Final.

Report," Y/0WI/Sub-7087/1, The Charles Stark Draper laboratory.

Inc.,JCambridge, Massachusetts.

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Herndon[d.,andSmith,D.K.,1976,"Pluqqingwel1sfor

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10.

abandonment: a state-of-the-art study and recommended procedures," -i Y/0WI/59b-76/99068, Hilliburton Services, Duncan, Oklahoma.

11. Hoek, E. , and Brown, E. T. ,1980, " Underground Excavations in Rock "

The Institution of Mining and Metallurgy,' London.

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12. Kelsall, P. C., Case, J. G., and Chabannes, C. R., 1982, "A Prelirr.inary Evalaution of the Rock Mass Disturbance Resulting From.

Shaft. Tunnel, or Borehole Excavation," ONWI-411, D'Appolonia Consulting Engineers, Inc., Albuquerque, New Mexico.

13. Kelsall, P. C. , Coons, W. E. , and Meyer. D. ,1983 " Repository Sealing Program Plan: Repository in Salt " ONWI-414, D'Appolonia Consulting Engineers Inc.. Albuquerque, New Mexico.

14. Koplik, Charles M. , Pentz. David L. , and Talbot, Richard,1979, "Information Base For Waste Reposf*ory Design, Volume 1. Borehole and Shaft Sealing," NUREG/CR-0495, prepared for the U. S. Nuclear Regulatory Commission, Washington.

15. Lingle. R., Stanford, K. L., Peterson, P. E. and Woodhead, S. F.,

1982, "We11 bore Damage Zone Experimental Determination," ONWI-349 Terra Tek, Inc., Salf. Lake City, Utah.

16. Mathis, S. P. and Daemen, J. J. K., 1982, " Borehole Wall Damage Induced by Drilling," Topical Report to the U. S. Nuclear Regulatory Commission, NRC Contract NRC-04-78-271, University of Arizona.

Tucson, Arizona.

17. Montazer, P. M., and Hustrulid, W. A., 1983, "An Investigation of Fracture Permeability Around an Underground Opening in Metamorphic Rocks," BMI-0CRD-4(5). Colorado School of Mines, prepared for the Office of Crystalline Repository Development. Columbus, Ohio.

18. Rhoderick, J. E. , Wong, G. S. , Buck, A. D. ,1981. " Examination of ,

Samples of Bell Canyon Test 1-FF Grout," ONWI-246. U. S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi.

19. Roy. D. M., Langton, C. A. 1982, " Longevity of Borehole and Shaft Sealing Materials: Characterization of Cement-Based Ancient Building Materials," ONWI-202. The Pennsylvania State University, University Park. Pennsylvania.

20. Statler, R. D., 1980. " Bell Canyon Test-Field Preparation and Operation." SAND 82-0458C, Sandia National Laboratories Albuquerque, .

New Mexico.

21. Taylor. C.. and O'Rourke, J. E., 1980, "Preconceptual Systems and '

Equipment for Plugging Man-made Accessed to a Repository in Basalt,"

RHO-BWI-C-67. Woodward - Clyde Consultants, prepared for Rockwell Hanford Operations. Hanford Washington.

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'22. U.S. Environmental Protection Agency, " Environmental Standards for the Management and Disposal of Spent Nuclear Fuel, High-Level and Tranuranic Radioactive' Wastes," 40 CFR 191, Draft 5.

23. U. S. Nuclear Regulatory Commission, June 21, 1983, "10 CFR Part 60

- Disposal of High-Level Radioactive Wastes in Geologic' Repositories, " Technical Criteria," Final Rule.

24. U. S. Nuclear Regulatory Commission,' 1982, " Standard Format and Content of Site Characterization Reports for High-Level Waste Geologic Repositories," Regulatory Guide 4.17.

25. U.S. Nuclear Regulatory Commission, 1985, " Final Generic Technical Position on In Situ Testing During Site Characterization for High-Level Nuclear Waste R positories."

26.' U.S. NRC Draft Review Plan: Quality Assurance for Site Characterization of High-Level Nuclear Waste Repositories, June 1984. .

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