ML23156A025

PR-060 - 49FR05934 - Disposal of High-Level Radioactive Wastes in the Unsaturated Zone

ML23156A025
Person / Time
Issue date:	02/16/1984
From:	Chilk S NRC/SECY
To:
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PR-060, 49FR05934
Download: ML23156A025 (1)

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ADAMS Template: SECY-067 02/16/1984 PR-060 - 49FR05934 - DISPOSAL OF HIGH-LEVEL RADIOACTIVE WASTES IN THE UNSATURATED ZONE PR-060 49FR05934 RULEMAKING COMMENTS Document Sensitivity: Non-sensitive - SUNSI Review Complete J

PR-

.DOCKET FILE INVENTORY Docket No. PR-60 (49 FR 5934)

Document No.

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 In the Matter of DISPOSAL OF HIGH-LEVEL RADIOACTIVE WASTES IN THE UNSATURATED ZONE Docket Date 02/13/84 03/12/84 03/19/84 03/22/84 04/12/84 04/13/84 04/16/84 04/16/84 04/16/84 04/16/84 04/16/84 04/20/84 04/20/84 04/23/84 04/27/84 05/04/84 07/12/84 Date of Document 02/13/84 03/06/84 03/14/84 03/15/84 03/30/84 04/11/84 04/13/84 04/13/84 04/13/84 04/16/84 04/13/84 04/20/84 04/20/84 04/20/84 04/23/84 04/30/84 07/11/84 VOLUME 1 Title or Description of Document Federal Register Notice - Proposed Rule (published 02/16/84)

Comments Benjamin Dover (1)

Comments Ecology/Alert (Nemethy) (2)

Comments Williams & Associates, Inc.

(Williams) (3)

Comments Argonne National Laboratory (Bates) ( 4)

Comments Wisconsin Radioactive Waste Review Board (Kleinhans) (5)

Comments State of Rhode Island and Providence Plantations (Vild) (6)

Comments Edison Electric Institute (Kearney) (7)

Comments Nevada Nuclear Waste Project Office (Loux/Johnson) (8)

Comments Department of Energy (Lawrence)

(9)

Comments Middle South Servces, Inc.

(Patterson) (10)

Comments U.S. Environmental Protections Agency (Hirsch) (11)

Comments State of Washington Department of Ecology (Moos) (12)

Comments U.S. Department of the Interior (Blanchard)( (13)

CommeRts Capital Area Groundwater Conservation Commission (Turcan) (14}

Ltr Department of the Interior (Robertson) regarding two typographical errors No. 23 Ltr Department of Energy (Rusche) enclosing material regarding Comment No.9 J

Department of Energy Washington, D.C. 20585 JUL 11 1984 "84 JUL 12 P2 :59 Mr. Samuel J. Chilk Secretary of the Commission Attention: Docketing and Service Branch U.S. Nuclear Regulatory Commission Washington, D.C.

20555

Dear Mr. Chflk:

The Department of Energy submitted comments on the proposed amendment to 10 CFR Part 60 for disposal in the unsaturated zone in a letter to you dated April 16, 1984.

In that letter, the Department indicated it would provide a suggested alternative perfonnance objective, related to the geologic setting for sites located in the unsaturated zone, by separate letter after the close of the public comment period.

This letter transmits the proposed alternative perfonnance objective and the Department's rationale for the proposed perfonnance objective.

As indicated in the Department's letter dated April 16, 1984, we are available to meet with the NRC concerning the previously transmitted connnents or the enclosed material.

Sf ncerely, Mi.e, Director Office of Civilian Radioactive Waste Management Enclosures Acl;no*uled::;ed b;.1 card. *,,**********.-,-.-.-

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RATIONALE FOR PROPOSED ALTERNATIVE PERFORMANCE OBJECTIVE As noted in the DOE comment letter to the NRC dated April 16, 1984, Dames

& Moore concluded in NUREG/CR-3130 that the flux and the frequency of wetting events were the primary factors in determining releases from wastes disposed in the unsaturated zone.

DOE stated that ground-water travel time does not represent an appropriate measure of performance for a site within the unsaturated zone and that the flux through the repository, both in the unsaturated and saturated zones, is a more appropriate and direct measure of potential cumulative releases to the accessible environment.

Accordingly, DOE has given considerable effort toward developing a proposed performance objective based on flux through a repository located in the unsaturated zone. Although this effort has reinforced the understanding that flux is the primary factor in determining releases from wastes disposed in the unsaturated zone, DOE has concluded that it is impractical to specify a minimum amount of flux or to otherwise define a performance objective for the geologic settings based on the flux through the repository. A determination of flux will be necessary, however, to demonstrate compliance with the EPA Standard.

As a result, DOE reviewed the NRC rationale for the performance objective specifying that the fastest likely path of radionuclide travel to the accessible envirol'lllent shall be at least 1000 years or such other travel time

2 as may be approved or specified by the Commission.

This perfonnance objective can be interpreted as specifying a minimum time before release of radionuclides to the accessible environment.

DOE concludes, based on this review and interactions between NNWSI Project staff and the NRC staff, that satisfying this perfonnance objective is meant to provide an independent and redundant barrier to the engineered barrier system during that period of time when the wastes are most hazardous (46 FR 130, p. 35281).

DOE notes that, for sites located in the unsaturated zone, this same effect may be derived, either in whole or to a large extent, from the creation of a drying zone around the underground facility during the period of the heat pulse. Therefore, the concept of a minimum time for release of radionuclides to the accessible environment forms a reasonable basis for a site performance objective for the unsaturated zone and is a more appropriate performance objective than ground-water travel time for the unsaturated zone.

The emplacement of radioactive waste canisters within an unsaturated zone repository leads to a situation wherein the heat generated by the wastes as they decay causes the moisture in the rock surrounding the waste canisters to migrate away from the waste canisters. Preliminary numerical modeling of this phenomenon(l) indicates that this migration creates a zone around the (l)s. Travis, H. Hudson, T. Nuttall, T. Cook, and R. Rundberg, 1984, "Preliminary Estimates of Water Flow and Radionuclide Transport in Yucca Mountain," LA-UR-84-40 (in Review), Los Alamos National Laboratory, Los Alamos, New Mexico.

3 canisters, extending for a few tens of meters in which there is no water available to either corrode the canisters, dissolve the wastes, or transport any radioactive material. The drying phase for a saturated zone repository is expected to last several hundred years before resaturation is complete (NUREG-0804).

In an unsaturated zone repository, the time required for moisture to return to the waste packages is expected to be even longer because the rock will return to initial conditions primarily through capillary effects.

A site performance objective for the unsaturated zone, based upon the minimum time for release of radionuclides to the accessible environment, must consider four separate physical events. The first event is the creation of the drying zone.

The second event, which is closely related to the creation of the drying zone, is the subsequent return of moisture to the rock surrounding the waste canisters. These two events encompass a time during which no water is available to either corrode the waste canisters, dissolve the waste material, or transport radionuclides to the accessible environment.

The third event important to the release of radionuclides to the accessible environment is the transport of radionuclides in the unsaturated zone.

Finally, the radionuclides are transported to the accessible environment by ground water movement in the saturated zone.

The minimum time for release of radionuclides to the accessible environment is the sum of times required for each of the four events because they are temporally sequential. The minimum time for release of radionuclides to the accessible environment for an unsaturated zone repository is thus the

4 sum of the time during which a drying zone exists around the waste canisters, the time it takes for the dry rock to return to initial moisture conditions, the time for ground water to travel through the unsaturated zone and the time for ground water to travel through the saturated zone to the accessible enviro1111ent.

It is not inconceivable that the time for drying added to the time for return to initial moisture conditions could encompass the total 1000 year period required for fission products to decay to insignificant levels.

When all four time components are added together, significantly higher confidence in protection of public health and safety is obtained than if only the time when radionuclides are actually moving were considered.

The NNWSI Project site characterization activities include studies of the drying phenomenon.

In addition to the previously mentioned study of radionuclide transport and the formation of the drying zone, other numerical studies which model the physical responses, in the unsaturated zone, to the emplacement of waste canisters and heat are underway.

In situ tests to obtain information about moisture migration in response to thermal loads are planned for the exploratory shaft. These tests include bulk permeability tests, canister scale heater experiments and waste package tests. The waste package tests are reduced scale but are designed to specifically investigate moisture conditions, particularly moisture movement during thermal and post thermal periods of storage. High frequency electromagnetic, ultrasonic and neutron methods are to be used to establish the moisture content in the area

5 surrounding the simulated canister before and after thermal cycling and to monitor fluid movement during the experiments. These activities should provide the necessary and sufficient information to support demonstration of compliance with the proposed alternative performance objective.

PROPOSED ALTERNATIVE PERFORMANCE OBJECTIVE DOE proposes that Section 60.113(a)(2) be revised to Section

60. 113(a)(2)(i) and a Section 60. 113 (a)(2)(ii) be added as follows:

For a geologic repository located in the unsaturated zone, the minimum 1000 year travel time to the accessible environment shall include the time of existence of the drying zone around the emplaced wastes, the time required for rewetting to initial moisture conditions, the time of travel through the unsaturated zone, and the time of travel through the saturated zone.

6

GEOLOGICAL SURVEY RESTON, VA. 22092 In Reply Refer To:

April 30, 1984 "84 HAY -4 P 2 :32 WGS-Mail Stop 410 Ms. Colleen Ostrowski, Geologist Office of Nuclear Regulatory Research Nuclear Regulatory Commission Washington, o.c.

20555

Dear Ms. Ostrowski:

Thank you for your telephone call of April 25, 1984.

There were indeed two typographical errors in the comments originating from the U.S. Geological Survey contained in the letter from Bruce Blanchard to Samuel J. Chilk of April 20, 1984, concerning review by the Department of the Interior of the proposed rule for Disposal of High-Level Radioactive Wastes in the Unsaturated Zone (10 CFR 60).

The two errors that you so perceptively found are both on page 4 of the letter and can be corrected as found on the enclosed new page 4.

Enclosure Sincerely yours,

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John B. Robertson

Chief, Office of Hazardous Waste Hydrology

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4 have an average recharge rate of 10mm. per year and an average subsurface moisture content of 10 percent (10 percent of bulk volume contains water), an average velocity would be 10/0.1 or 100mm per year (O.lm per year).

If it were 100m above the water table, the travel time in the unsaturated zone alone would be 1000 years. It becomes obvious that a nearly zero moisture content would result in a theoretically infinite velocity.

This is absurd, but does emphasize the need for prudent application of any mechanism with which to approximate conditions that defy accurate analysis.

Ground-water velocity is one important element of performance and although this method is not precise or highly accurate, the method could form the basis for approximations that could be consistently applied to a variety of sites where unsaturated porous media are part of the flow system.

Section 60.122(b)(8):

"For disposal in the unsaturated zone, hydrogeologic conditions that provide *** "

Section 60.122(b)(8)(i): "Low and nearly constant moisture flux in the host rock and in the overlaying and underlying hydrogeologic units." This is an improvement over the earlier "low and constant moisture content" in that it avoids the erroneous implication that low moisture content necessarily means low flux.

However, "nearly constant *** flux is not necessarily an advantage, as evidenced by the conflict with "free drainage," 60.122(b)(8)(iv).

A low, constant rate of flux would seem to offer better opportunity for dissolution processes than would an average low, but episodically high flux.

There is some evidence also that some materials for waste canisters may be more resistant to corrosion under episodic wetting and drying.

Basically, it seems best to address only a single concept or factor in a single statement of condition.

Also, change "overlaying" to "overlying."

Section 60.122(b)(8)(ii):

"A water table sufficiently below the underground facility such that fully saturated voids continuous with the water table do not encounter the underground facility."

This condition has also been improved over the earlier version, which depended on a rather inappropriate definition of "capillary fringe."

However, it still appears to be incumbent on the applicant to prove that there are no continuous paths of water occupying saturated pores--an impossible task.

We suggest changing the favorable condition to read as follows:

"(ii) Conditions that preclude, or limit, capillary rise from the water table to the underground facility;"

This directly addresses the concerns expressed by the NRC staff regarding siting a facility in the capillary fringe but avoids definition of the term "capillary fringe."

Section 60.122(b)(8)(iv): "A host rock that provides for free drainage; or *** "We suggest that "or" should be changed to "and."

Section 60.122 (b), (8), (v):

"A climatic regime in which the average annual historic precipitation is a small percentage of the average annual potential evapotranspiration."

The term "small percentage" is vague and inappropriate, in our opinion.

We suggest specifying an absolute value of average recharge as a maximum, perhaps on the order of 50mm. or less.

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• e4 APR 27 A10 :52 Baton Rouge, Louisiana 70896-4526 P. 0. Box 64526 Telephone (504) 924-7420 April 23, 1984 Secretary of the Commission U.S. Nuclear Regulatory Commission Washington, D. C.

20555 Attn:

Docketing and Service Branch REF:

NRC 10 CFR Part 60 Proposed rule

Dear Sir:

Unfortunately my comments are being offered after the expiration of the comment period.

However, I believe the following practical comments extracted from U.S. Geological Survey Circular 903 titled, "Disposal of high level nuclear waste above the water table in arid regions," are pertinent to the referenced CFR from the Federal Register of February 16, 1984 (v.49, no. 33).

"A major new concern would be shether future climatic changes could produce significant consequences due to possible rise of the water or increased flux of water through the repository.

If spent fuel were used as a waste form, a second new concern would be the rates of escape of gaseous iodine-129 and carbon-14 to the atmosphere."

As NRC refer to the circular in the proposed rule, NRC has obviously considered these comments.

There is a discussion of vapor transport in the rules and the need for consideration on a case by case base of the problem in the Rule~ Section, "Issued examined by the Commission."

Hopefully, the Commission's conclusion is satisfactory or is more in-depth caution required?

The requirement of a minimum depth of 300 meters may minimize to some degree the effects of climatic changes?

But there should be a required minimum predetermined interval between the top of the water table and the bottom of burial depth to prevent water entering the repository.

NRC has done an excellent job but I believe it is important to reexamine these two factors and possibly reemphasize more specific safety criteria.

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Secretary of the Commission U.S. Nuclear Regulatory Commission April 23, 1984 Page 2 Thanks for the opportunity to comment.

Very truly yours, ANT/ebo cc:

Dr. L. Hall Bohlinger Pat Norton

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United States Department of the Interior Mr. Samuel J. Chilk Secretary of the Commission OFFICE OF THE SECRETARY WASHINGTON, D.C.

2024-0 U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Dear Mr. Chilk:

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The Department of the Interior has reviewed the proposed rule for Disposal of High-Level Radioactive Wastes in the Unsaturated Zone (10 CFR 60). Our detailed comments are attached.

We appreciate the opportunity to comment on this proposal.

Sincerely, ruc~!~J Environmental Project Review Enclosure

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REVIEW OF PROPOSED RULE FOR DISPOSAL OF HIGH-LEVEL RADIOACTIVE WASTE IN THE UNSATURATED ZONE (ER 84/271)

In commenting on the proposed unsaturated-zone amendments, it is convenient to separate discussion into: (1) responses solicited by NRC (49 FR 5937); (2) comments on the proposed amendments; (3) comments regarding saturated-zone criteria that are also applicable to the unsaturated zone, and (4) comments on definitions.

NRC SOLICITATIONS (la)

"How can ground-water travel time in the unsaturated zone be determined with reasonable assurance?"

While it may not be possible to define ground-water velocities along all segments of unsaturated-zone travel paths with precision, particularly those segments through moderately to highly fractured media, the velocities and travel times in some segments are less elusive.

In the case of a relatively uniform, porous medium with low-fracture density, the medium will be capable of transmitting a flux that is approximately equivalent to its saturated hydraulic conductivity without rejecting water to fracture flow paths.

Further, it is within the state-of-the-art to determine ambient water content and degree of saturation as well as moisture-characteristic curves for such media so that effective conductivity can be predicted for a range of conditions.

In-situ monitoring techniques are undergoing development and may broaden the range of rock types and conditions for which it is feasible to estimate velocity and, hence, travel time.

On a site-specific basis, certain bounds may be placed by less direct considerations such as recharge rates based on water budgets, perturbations of thermal gradients, or in-situ monitoring of temporal changes in moisture profiles by neutron logging*.

Finally, repository investigations presently include exploratory-shaft tests on infiltration rates and sampling of intact fractured blocks for laboratory experiments.

"Reasonable assurance" may also be gained by incorporating uncertainty analysis into predictive models.

Although the uncertainty band for a given level of confidence in the calculations may be broader for unsaturated-zone cases than for some saturated-zone conditions, the opportunity to invoke conservatism still exists.

(lb)

"Should the ground-water travel time performance objective be limited to ground-water movement within the saturated zone?" Assuming that the ground-water travel time objective and favorable condition remain in the regulation, the travel time along any segment of the flow path including the unsaturated zone, should be creditable, provided that it can be demonstrated with "reasonable assurance" as discussed above.

(2)

"Does ground-water travel time represent an appropriate measure of performance for a site within the unsaturated zone, or would an alternative performance objective *** (e.g., maximum likely volumetric flow rate of ground water through the geologic repository) be more appropriate?" Travel time substantially exceeding 1,000 years, although a favorable condition, is not appropriate as a totally definitive performance objective for disposal in either the unsaturated or saturated zones.

Ground-water travel time probably is the singularly most important element for evaluating the performance of a

site; however, release criteria are ultimately the absolute measure of total performance.

The method by which travel time is calculated must account for all elements of the ground-water flow system and must result in terms that 2

can be used directly for determining transport and concentration of radio-nuclides in the ground water.

Release criteria and radionuclide transport must be concerned with many factors such as ground-water flux and velocity (travel time), convective transport, dispersion and diffusion, chemical inter-action with rocks along the flow path, and rates and concentrations at which radionuclides leached from the solidified waste enter the water. Realistic estimation of release criteria for the unsaturated zone might not be possible until observations are made in the shafts and drifts.

While it may be possible to assign a maximum allowable flux rate--e.g.,

one that would assure the failure of containment under reasonable assumptions of chemistry, corrosion, and dissolution--it would still be more consistent with the multiple-barrier concept to incorporate such considerations only as favorable or potentially adverse conditions.

PROPOSED AMENDMENTS Section 60.122, Siting Criteria, (6), (7): "Prewaste-emplacement ground-water travel time along the fastest path of likely radionuclide travel from the disturbed zone to the accessible environment that substantially exceeds 1,000 years." Add" *** considering both unsaturated and saturated segments of the flow path."

We believe that prewaste emplacement ground-water travel time is conceptually an appropriate "favorable characteristic" for sites located in the unsaturated zone.

However, it is a criterion that will be much more difficult to demonstrate in a legal sense at an unsaturated site than at a saturated site.

As currently worded, the criterion is perhaps inappropriate for unsaturated and perhaps some types of saturated sites, such as salt and dense fractured crystalline rocks.

We believe that in order for the travel-time criterion to be effectively applied, it needs to incorporate a concept of areally and temporally averaged ground-water flow velocity (rather than the fastest one-dimensional pathway) and/or a flux constraint.

Additionally, the current wording makes no provision for the quantity of water moving through the repository to the accessible environment--only the velocity. It seems inappropriate to reject a site that might have 1 cubic meter of water moving through a repository to the accessible environment in 1,000 years and to accept a site that might have 1 million cubic meters of water moving through it to the accessible environment in 1,500 years.

This example is, of course, hypothetical.

We also realize that there is an exception clause in the criterion for special considerations allowing the Commission to consider other factors when appropriate and when it can be demonstrated that a site would clearly meet EPA standards.

However, it is not clear how that exception might be applied or what difficulties would be encountered in gaining acceptance by the technical community or various public interest groups for such an exception.

Some of these difficulties might be overcome by one or more of the following options:

Clarify some typical circumstances under which the travel-time criterion might be waived, such as by demonstrating that the flux is likely to be small or nil.

3 Specify more precisely how the ground-water velocity (or travel time) should be calculated, using specific cross section area or other averaging or integrating conventions.

Use a volumetric flow rate (flux) criterion for ground water in addition to or in place of ground-water travel time.

The principal hydrologic advantage of the unsaturated zone is minimizing or eliminating contact of the waste with flowing ground water.

This advantage would most likely be more important than ground-water travel time in reducing total quantity of radionuclides which could potentially escape to the accessible environment.

The rate of release of radionuclides to the accessible environment from a repository in the unsaturated zone is directly related to the nuclide concentration in the leachate, flux of leachate, dilution of leachate in the zone of saturation, and ground-water velocity (plus geochemical retardation and dispersion effects). Minimizing leachate flux would appear to be at least as important as maximizing ground-water travel time.

It might, therefore, be appropriate to specify a dual "either/or" criterion such that ground-water travel time is greater than 1000 years or ground-water flux through the host rock at the proposed site is less than some specified average rate.

The rate could be based on nuclide solubility, leach rate criteria, and population exposure criteria (EPA concentration standards).

We believe that either a flux or travel-time criterion should be based upon an areally integrated or averaged calculation, over an area on the order of the cross-sectional area of the repository normal to the direction of expected flux, for both saturated and unsaturated sites. This would help reduce the uncertainty and controversy over how the "fastest pathway" can be determined.

The fastest pathway for saturated fractured rocks, for unsaturated media, and for other highly heterogenous media would be virtually impossible to calculate with reasonable confidence.

However, areal averaged or integrated calculations and bounded estimates can be determined with reasonable confidence, usually by two or more independent methods.

Also, qualitative evidence, such as the preservation of archeological artifacts, packrat middens, and other paleo-materials can lend further confidence to long-term estimates of leach rates and water contact in arid unsaturated materials.

If ground-water travel time is to remain a general performance objective criterion for the unsaturated zone, we believe the rule should specify a simple, straightforward, and consistent formula for site determination.

We propose the following formula for consideration.

Use of the formula is with the assumption that movement of water in the unsaturated zone is basically interstitial and that at least a continuous film of water is present.

The formula would have doubtful application in dominantly fractured rock with very little interstitial effective porosity.

The vertical ground-water velocity through the unsaturated zone could be determined as the average vertical recharge rate over the approximate area of the repository, divided by the average volumetric moisture content of the subsurface medium.

As a hypothetical example, if a site were determined to

4 have an average recharge rate of 10mm per year and an average subsurface moisture content of 10 percent (10 percent of bulk volume contains water), an average velocity would be 10/0.1 or 100mm per year (O.lm per year). If it were 100m above the water table, the travel time in the unsaturated zone alone would be 1000 years. It becomes obvious that a nearly zero moisture content would result in a theoretically infinite velocity. This is absurd, but does emphasize the need for prudent application of any mechanism with which to approximate conditions that defy accurate analysis.

Ground-water velocity is one important element of performance and although this method is not precise or highly accurate, the method could form the basis for approximations that could be consistently applied to a variety of sites where unsaturated porous media are part of the flow system.

Section 60.122(b)(8):

"For disposal in the unsaturated zone, hydrogeologic conditions that provide *** "

Section 60.122(b)(8)(i): "Low and nearly constant moisture flux in the host rock and in the overlaying and underlying hydrogeologic units." This is an improvement over the earlier "low and constant moisture content" in that it avoids the erroneous implication that low moisture content necessarily means low flux.

However, "nearly constant *** flux is not necessarily an advantage, as evidenced by the conflict with free drainage."

Section 60.122(b)(8)(iv):

A low, constant rate of flux would seem to offer better opportunity for dissolution processes than would an average low, but episodically high flux.

There is some evidence also that some materials for waste canisters may be more resistant to corrosion under episodic wetting and drying.

Basically, it seems best to address only a single concept or factor in a single statement of condition. Also, change "overlaying" to "overlying."

Section 60.122(b)(8)(ii):

"A water table sufficiently below the underground facility such that fully saturated voids continuous with the water table do not encounter the underground facility." This condition has also been improved over the earlier version, which depended on a rather inappropriate definition of "capillary fringe." However, it still appears to be incumbent on the applicant to prove that there are no continuous paths of water occupying saturated pores--an impossible task.

We suggest changing the favorable condition to read as follows:

Section 60.122(b)(8)(iv): "A host rock that provides for free drainage; or *** "We suggest that "or" should be changed to "and."

Section 60.122 (b), (8), (v):

"A climatic regime in which the average annual historic precipitation is a small percentage of the average annual potential evapotranspiration." The term "small percentage" is vague and inappropriate, in our opi nion.

We suggest specifying an absolute value of average rec arge as a maximum. perhaps on t he or er of 50mm or less.

5 Section 60.122 (c) 1 (24): We suggest adding quantitative clarification to this criterion.

As currently worded, it allows.!!.2. potential vapor-phase transport of radionuclides by molecular diffusion or perhaps by convective transport.

Although these fluxes might be miniscule, they would not be zero at any unsaturated site. Therefore, if this criterion is ever considered as a disqualifying factor it will need qualification as regards release rate of nuclides such as 1291 and 14c. Related to this question is the interpretation of t~e boundary for the accessible environment. It is not clear to us from the definition in 10 CFR 60 whether the "accessible environment" includes the airspace immediately above the ground surface directly over the repository or only the atmosphere beyond the boundary.

Differences in these two interpretations could have major impacts on how the vapor transport criterion is tested.

APPLICABLE SATURATED-ZONE CRITERIA Section 60.122(b)(2)(iii):

To l>e hydraulically correct, the phrase "low hydraulic potential between" should be "low hydraulic gradient between" or "small difference of hydraulic potential between." This concept is also applicable to the unsaturated zone and is implicit in the wording

Low *

• moisture flux in the host rock **** "

Section 60.122(b)(2)(iv):

We endorse extracting this as 60.122(b)(7),

as proposed, and adding the statement suggested above to make it clear that the travel time in the unsaturated zone should be creditable.

DEFINITIONS "Accessible environment. "

We strongly suggest that aquifers be incorporated in this definition.

• JOH SPELLMAN Governor DO ALO W. MOOS Director ST A TE OF WASHINGTON OOtKETEO U~~lR:

DEPART-MENT OF ECOLOGY Mail Stop PV-11 Olympia, Washington 98504

• (2J_.,445JjiJO P 3 :12 April 13, 1984 The Honorable Nunzio J. Palladino Chairman U.S. Nuclear Regulatory Commission 1717 H Street, N.W.

Wash i ngton, D.C. 20555

Dear Chairman Palladino:

Or SE*.,rtt1Ali 1 I C,E. TING & SE~VIC:f.

BRANCH 1}()CKf.T NUM.B£R PR-/,,/J 111 PROPOSED RULE

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Ref:

NUREG-1046, "Disp6sal of High-Level Radioactive Wastes in the Unsaturated Zone... Draft Report for Comment."

We are fully in agreement with the proposed amendments to 10 CFR 60 which accommodate candidate repository sites in the unsaturated zone.

However, it is apparent that the main body of reasoning and examples covered in the draft applies to the Nevada Test Site.

The principal technical reference, in fact, is NUREG/CR-3158, which contains in its title* the phrase, "Emphasis on the Nevada Test Site."

We have never been fully satisfied with the pre-NWPA siting decision process which led the U.S. Department of Energy to put its Hanford Reference Repository Loc ation deep in the saturated zone, stratigraphically close to aquifers of great economic importance.

As the principal water management agency for a_ state where future water quality and availability are

~ensitive, highly-charged issues, we are deeply concerned with any risk of contamination, no matter how slight.

The proposed amendments can be iiterpreted as a signal that the Nuclear Regulatory Commission, like the state of Washington,

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The Honorable Nunzio J. Palladino April 13, 1984 Page 2 wants to see all reasonable alternatives examined and, where indicated, re-examined before final commitment to a deep,

difficult site such as the Hanford location in the saturated zone.

Director DWM/kh cc:

David W. Stevens

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON. D.C. 20460 DOt l~[T['."'

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"84 APR 20 P 1 :09 OFFICE OF EXTERNAL AFFAIRS APR 2 0 l984 Dr. Colleen Ostrowski Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington, D.C.

20555

Dear Dr. Ostrowski:

In accordance with Section 309 of the Clean Air Act, as amended, the U.S. Environmental Protection Agency (EPA) is commenting on the U.S. Nuclear Regulatory Commission's (NRC) proposed amendment to 10 CFR 60, Disposal of High-level Radioactive Waste in the Unsaturated Zone.

EPA generally supports the proposed rule.

EPA is developing Environmental Standards for Management and Disposal of Spent Nuclear Fuel, High-level and Transuranic Radioactive Wastes (40 CFR 191).

Any disposal of high-level wastes will be subject to 40 CFR 191, and EPA appreciates the assistance NRC and other organi-zations has given us in the development of our rule.

Accordingly, EPA is submitting the enclosed comments to avoid differing regulatory approaches between the NRC and EPA rulemaking efforts.

EPA will work with NRC to avoid conflicting approaches on the respective rules of the two agencies.

I appreciate the opportunity to comment on this proposal. If you have any questions concerning EPA's comments, please call Dr. W. Alexander Williams (382-5909) of my staff or Mr. Daniel Egan (557-8610) of EPA's Office of Radiation Programs.

Enclosure Sincerely yours, r

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Comments of the U.S. Environmental Protection Agency on the U.S. Nuclear Regulatory Commission's Proposed Rule for Disposal of High-level Radioactive Wastes in the Unsaturated Zone

1.

10 CFR &60.2 (Definitions)

NRC proposed to redefine the term "ground water" to include all water in both the saturated and unsaturated zones. This change apparently pro-vides a simple regulatory means for applying existing criteria written several years ago for high level waste repository siting in the saturated zone to the unsaturated zone as well. While this expansion of applicabil-ity may be reasonable, EPA would prefer that the NRC retain the standard scientific meaning for the term (i.e., water within the zone of saturation).

We are concerned that confusion may eventually arise among the public, par-ticularly in their understanding of the application of methods of ground water monitoring.

"Unsaturated zone" should be defined as the zone between t~e land surface and the shallowest free water table, discounting "perched" tables.

The definition written in the proposed regulation says, 11deepest." This is confusing. The definition with "deepest" would be correct, however, if the term "water table" were also defined as the potentiometric surface beneath the land surface at atmospheric pressure.

2.

10 CFR &60.122 (siting criteria)

The Commission proposes to amend Section 60.122 by adding new para-graphs (b) (8) and (c) (23). There seems to be a conflict in the criteria outlined under portions of the two respective paragraphs.

Paragraph (b) (8)

{iii) requires that hydrogeologic conditions in the unsaturated zone pro-vide for "a laterally extensive, low permeability unit above" the reposi-tory to inhibit downward migration of water into the underground facility.

Paragraph (c) (23) presumably calls for the unsaturated zone to be free of the potential for "perched water bodies that may have the effect of saturat-ing portions of the underground facility." It seems that these are in conflict because the laterally extensive, low permeability unit encouraged to be located above the repository as outlined in paragraph (b) (8) increases the potential for the formation of perched water bodies immediately above the unit. Although the low permeability strata may serve to inhibit downward migration, it encourages the possibility of perched water bodies that may result in saturated flow conditions above and immediately surrounding the limits of the underground repository.

Conversely, paragraph (c) (23) discourages siting in areas where the potential for existing or future perched conditions exists. EPA recommends that this inconsistancy be resolved.

3.

With respect to the three questions on which the Conmission particularly seeks comment:

Question:

"How can ground water travel time in the unsaturated zone be determined with reasonable assurance?"

EPA Reply:

EPA's Office of Solid Waste will soon publish Procedures for Modeling Flow Through Clay Liners to Determine Required Liner Thickness in its series of Technical Resource Documents.

This manual presents a numerical simulation model to estimate travel time of water through unsaturated sediments.

Once copies are available from GPO, we will forward one to Dr. Colleen Ostrowski at the NRC.

Measuring natural tritium (3H) concentrations in ground water samples from a vertical profile in unsaturated geologic formations may be another technique for estimating travel time. Since the atmospheric testing of nuclear weapons, ground water recharge (i.e., precipitation) has contained levels of this radioactive isotope above the naturally low levels existing before the testing began. Consequently, tritium may serve as an indicator or tracer of 11new 11 water in a geologic profile, and thus may indicate approximate travel times from the recharge point.

Question:

"Should the ground water travel time performance objective be limited to ground water movement within the saturated zone?"

EPA Reply:

No.

To allow DOE to take credit for the delay in water reaching the water table after passing an unsaturated zone repository (when considering NRC's existing 1,000 year "ground water" travel time requirement), NRC proposes to redefine the term "ground water" to include all water below the land surface, not just water below the water table, in the saturated zone.

We do not think it is necessary to change the widely understood meaning of this term to accompish NRC's objective.

EPA agrees that DOE should be able to take credit for any such delays in the unsaturated zone.

However, it would be more appro-priate to make the existing section 60.113(a)(2) apply only to reposi-tories in the saturated zone and to add a parallel section for unsaturated zone repositories that allows the Department to add the water travel times in the saturated and unsaturated zones to compare against the 1,000-year time period.

Even if NRC redefines the term "ground water" for 10 CFR 60, EPA has no plans or need to make a corresponding change in 40 CFR 191.

Question:

"Does ground water travel time represent an appropriate measure of performance for a site within the unsaturated zone, or would an alternative performance objective for the geologic setting be more appropriate?"

EPA Reply:

No, it does not.

An alternative option should be available.

EPA does not believe that such a "water" travel time is appropriate as the only quantitative measure of performance for a site within the

unsaturated zone.

Instead, we believe that DOE should have the option of meeting a fairly stringent limit on the average annual flux of water through the repository to the accessible environment instead of the travel time requirement of section 60.ll3(a)(2). This limit should be chosen so that the corresponding total volume of water reaching the accessible environment within a thousand years would not be capable of transporting a significant amount of radioactivity, taking into account reasonable solubility limits. At a particular site, the Department should have the option of demonstrating compl iance with either the minimum travel time requirement or the maximum water flux requirement.

f MIDDLE SOUTH SERVICES, INC./BOX 6I000/NEW DRLEA~, LA19tf1~IEf>>lf'~~4) 528-5262 Secretary of the Corrnnission U.S. Nuclear Regulatory Commission Washington, D.C.

20555 Attn:

Docketing and Service Branch

Dear Sir:

April 13, 1984

Subject:

NRC's Proposed Rule Concerning the Disposal of High-Level Radioactive Wastes in the Unsaturated Zone (49 FR 5934)

Middle South Services, Inc. (MSS) is a technical support company for the Middle South Utilities (MSU) System which serves the electrical requirements of approxi-mately 1,800,000 customers in portions of Arkansas, Louisiana, Mississippi and Missouri.

MSS has reviewed the proposed amendments and draft NUREG-1046, "Disposal of High-Level Radioactive Wastes in the Unsaturated Zone : Technical Considerations" and would like to express our support of the proposed amendment which allows the disposal of high-level radioactive waste (HLW) in the unsaturated geologic zone.

The Middle South System has four nuclear reactors in operation or nearing operational status, therefore Middle South Utilities has been closely following the progress being made toward the opening of the first high-level nuclear waste reposi-tory.

The siting of these repositories must be limited to those geologic areas where the HLW can safely be disposed of without significant damage to the environment or harm to the public's health.

A review of the proposed amendments and its associated NUREG shows that the unsaturated geologic zone is a viable alternative to disposal in the saturated zone.

Each site, whether it is located in the saturated or the unsaturated zone, should be judged based on its overall ability to safely contain HLW.

Currently, there is not sufficient technical justification to favor disposal in the saturated zone over the unsaturated zone.

As mentioned in NUREG-1046, there are some factors which make disposal of HLW in the unsaturated zone preferable to disposal in the saturated zone.

Two of these factors are:

(1) wastes can be emplaced in a geologic medium with low moisture content which would minimize leach-ing of waste packages; and (2) enhanced retrievability-wastes would be more easily accessible in an unsaturated zone if this need should ever arise.

There are factors SERVING: MIDDLE SOUTH UTILITIES. INC.

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r Secretary of the Commission April 13, 1984 Page which make the saturated zone a more desirable location, however, as stated previously, each site must be reviewed based on all relevant factors, not simply on whether the site is located in a saturated or unsaturated zone.

A balancing of all factors will ensure that the most suitable sites are chosen for the disposal of HLW.

MSS regrets that we are unable to provide NRC with the technical comments which have been requested.

However, we appreciate this opportunity to comment on and express our support of this proposed amendment.

The siting and the eventual operation of HLW repositories are of vitalL~portance to the electric utility in-dustry.

MSU encourages and supports NRC in their endeavor to accomplish this goal within the time-frame established in t he Nuclear Waste Policy Act.

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Department of Energy Washington, D.C. 20585 APP l 6 1984 Mr. Samuel J. Chilk Secretary of the Commission

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Docketing and service Branch u.s. Nuclear Regulatory Commission Washington, D.C.

20555

Dear Mr. Ch ilk:

The Department of Energy is pleased to respond to the request of the Nuclear Regulatory Commission (NRC) for comments on the proposed amendments to 10 CFR 60, published on February 16, 1984 (49 Federal Register 5934).

The proposed amendments would make the regulation applicable to disposal of high-level radioactive wastes in both the saturated and unsaturated zones.

our comments are contained in two enclosures to this letter:

the first contains specific comments on the proposed amendments with recommended alternative language where appropriate; the second contains the Department's response to the questions posed by NRC in the Supplementary Information section of the Federal Register notice.

The Department believes the performance objective for a minimum 1000-year groundwater travel time should only be applied to sites located in the saturated zone.

The Department recommends an alternative performance objective, related to the geologic setting, for sites located in the unsaturated zone.

The Department will provide a suggested alternative performance objective for NRC consideration by separate letter after the close of the public comment period.

The Department will make every effort to provide this information by May 15, 1984.

The Department believes that the proposed amendments, as revised to incorporate the Department's comments, will make 10 CFR 60 effective regulation applicable to sites located in the unsaturated or saturated zones.

We are available to meet with NRC concerning the enclosed comments.

Enclosures

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ENCLOSURE 1.

Comments on Proposed Amendments to 10 CFR Part 60 for the Unsaturated Zone

§60.2, Definition of Ground Water

§60.2, Definition of Disturbed Zone

§60.2, Definition of Barrier ib0.122(b)(2)Ciii)

The NRC is to be commended on the definition of the term "ground water."

The NRC definition includes water in both the unsaturated and saturated zones.

This definition is, however, inconsistent with the EPA definition in 40 CFR Part 191, wherein the EPA defines ground water to include only that water in the saturated zone.

DOE agrees with the NRC definition.

Using the EPA definition, DOE believes the proposed amendments would have to be revisited in their entirety.

With incorporation of the unsaturated zone provisions into 10 CFR Part 60, DOE believes the definition of disturbed zone should be reconsidered.

DOE believes the disturbed zone should not include the volume of rock in which changes will occur which will improve the isolation capability of the repository.

For example, the Supplementary Information and NUREG-1046 indicate there may be the creation of a drying zone extending hundreds of meters from a repository located in the unsaturated zone.

This drying zone (and the accompanying increase in degree of saturation at some farther distance) will create a hydraulic gradient in all directions toward the repository - a favorable condition which will exist throughout the temperature pulse.

DOE recommends that the NRC revise the definition of the term "disturbed zone" to apply to that volume of rock in which changes will occur which will have a significant adverse effect on the performance of the repository.

DOE recommends revising the definition to mean any material, structure, or condition that prevents, or substantially delays, movement of water or radionuclides.

The basis for this recommendation is discussed in the comment on Section 60.122Cb)(8)(iii).

The phrase "low hydraulic potential" should be revised to either "low hydraulic gradient" or "small difference of hydraulic potential" to be hydraulically correct.

5.

§60.122(b)(5)

6.

§60.122(b)(8)(i)

7.

§60.122(b)(8)(ii)

DOE believes that, although a minimum depth of 300 meters for waste emplacement is a favorable condition, the application of this favorable condition to the unsaturated zone is non-conservative in that it ignores the greater benefit to isolation derived from maximizing the thickness of the unsaturated zone between the underground facility and the water table.

Instead, it supports the concept of *the deeper, the better* (see page 19 of NUREG-1046) without consideration of the lesser likelihood of exhumation by erosion, the lesser likelihood of intrusion by deep water well drilling in isolated arid environments, or the advantages of maximizing the thickness of the unsaturated zone between the underground facility and the water table.

To achieve a meaningful balance between favorable conditions for the unsaturated and saturated zones, DOE recommends adoption of a favorable condition for the unsaturated zone that acknowledges the favorability of a substantial distance between the underground facility and the water table.

Adoption of such favorable condition is consistent with NRC concerns in Sections 60.122(b)(8)(ii) and 60.122(c)(22).

The words *and nearly constant* should be removed so that this section reads "Low moisture flux in the host rock and in the overlying and underlying hydrogeologic units.*

DOE notes that recharge is not constant in either time or space.

Rather, recharge is sporadic, occurring in response to individual heavy rainfalls, extended periods of rainfall (wet season), or snowmelt.

Between these recharge events, water in the unsaturated zone is held in tension and flux becomes negligible - an obvious advantage of disposal in the unsaturated zone.

These findings led Dames & Moore to conclude in NUREG/CR-3130 that the flux and the frequency of wetting events were the primary factors in determining releases from wastes disposed in the unsaturated zone.

DOE is concerned with the NRC approach to the concept of capillary fringe as described in this condition and on page A-1 of Appendix A to NUREG-1046.

DOE notes that the upper surface of the zone of tension saturation (capillary fringe) is neither constant nor planar; rather, it is dynamic and at different heights in materials

8.

§60.122(b)(8)(iii) of different pore sizes owing to the higher capillary rise in smaller pores.

The NRC has addressed the DOE concern about the number or percent of fully saturated voids continuous with the water table in NUREG-1046, wherein they have suggested a definition of capillary fringe as a planar surface, at which 50 percent of the pore space is filled with water.

This suggested definition corresponds with the usage in USGS Water-Supply Paper 1988.

However, the suggested definition can be interpreted as applying to any material having a degree of saturation of 50 percent or greater.

DOE notes that, at a degree of saturation of 50 percent, no pore spaces have to be completely filled with water (and hence it would be above the capillary fringe).

DOE believes the intent of the definition is a planar surface at which 50 percent of all pore spaces are completely filled with water (50 percent of all pore spaces are not completely filled with water).

DOE does not believe that either approach can be defined by field measurements.

DOE believes the concept of avoiding waste emplacement in the capillary fringe is valid, though the definition of the capillary fringe will always elude precision.

The capillary fringe is something that everyone knows exists, but which no one can adequately define.

Even if an unambiguous, non-arbitrary definition is found, the upper limit of the zone of *fully saturated voids continuous with the water table*

can probably not be defined by field measurements, particularly under conditions of heterogeneous materials and infiltrating water.

However, in very few, if any, cases could the upper limit of the capillary fringe be more than a few tens of meters.

DOE recommends this section be revised to recognize that it is physically limited to a few tens of meters.

DOE recommends that this section be revised to read "A hydrogeologic condition above the host rock that would inhibit the downward movement of water, divert downward moving water to a location beyond the limits of the underground facility, or divert a significant portion of downward moving water, including that produced by sporadic,

9.

§60.122(c)(23)

10.

§60.133(f)

11.

§60.134(b) intense recharge events, away from the location of waste emplacement.*

This rewording addresses the DOE concern that hydrogeologic conditions other than a low permeability unit, such as a contrast in permeabilities in adjacent hydrogeologic units sufficient to create a capillary break, may result in the desired effect.

In addition, the rewording recognizes the favorable effect of vertical flow conduits, even within the boundaries of the underground facility, in diverting water away from the emplaced wastes.

The ability of a hydrogeologic condition, such as a capillary break, to inhibit water movement (or radionuclide transport) supports the previously recommended revision to the term *barrier.*

DOE recommends rewording this section to clarify its meaning as follows:

• Potential for existing or future perched water bodies that may saturate portions of an underground facility or provide a faster flow path from an underground facility to the accessible environment.*

This section, now applicable to disposal in either the unsaturated or saturated zones, on rock excavation design criteria states that the potential for creating a preferential ground-water pathway must be limited.

However, in the unsaturated zone, a preferential ground-water pathway may be preferred in order to have a freely draining host rock as contained in the proposed Section 60.122(b){8)(iv).

DOE recommends revising this section to *The design of the underground facility shall incorporate excavation methods that will limit the potential for creating pathways that could compromise the ability of the repository to meet the performance objectives,* to allow internal consistency in the technical rule for the unsaturated zone.

This recommended change is consistent with the wording contained in Section 60.133(a).

As in the preceding comment, DOE believes that in the unsaturated zone, it may be beneficial to

• seal* boreholes and shafts so as to create a preferential pathway for ground water along at least part of the length of the borehole or shaft.

For example, it may be desirable to have

12.

§60.14l(c) a preferential pathway for ground water from an overlying unit where the ground water may tend to perch naturally, to an underlying unit or completely through the repository horizon (but not in areas of emplaced wastes) to an underlying permeable zone.

DOE believes the unsaturated zone offers some interesting opportunities for innovative methods and materials for backfilling and sealing, as noted by G. Roseboom in USGS Circular 903.

DOE recommends either revising Section 60.134(b) to be applicable to only the saturated zone, or rewording it to read wMaterials and placement methods for seals shall be selected to reduce, to the extent practicable, the potential for creating pathways that compromise the ability of the repository to meet the performance objectives.ff This recommended change is consistent with the wording contained in Section 60.134(a).

Several of the minimum measurements required in this section, particularly changes in ground-water conditions and rock pore-water pressures (including those along fractures and joints) may be unnecessary, of limited use, or difficult to measure in the unsaturated zone, especially given the creation of a drying zone which may reduce moisture contents so low or create such high negative pressures as to exceed the range of measurement for available instrumentation.

DOE recommends revising Section 60.141 to replace the term *as a minimum* with the term "where practicable.*

This recommended change is consistent with the wording already contained in Section 60.140.

ENCLOSURE 2.

Responses to Specific Questions Raised in the supplementary Information Question 1.

This question, as stated in the supplementary Information Section, consisted of two questions which are addressed separately below.

A.

• How can ground-water travel time in the unsaturated zone be determined with reasonable assurance?*

Ground-water flux can be determined, using measurements of ambient water content, degree of saturation, matric potential, and hydraulic conductivity to determine moisture-characteristic curves relating these parameters to one another.

These curves can be developed so as to predict the constitutive relationships over a wide range of conditions (varying degrees of saturation and different matric potentials).

From these relationships and flux determinations, velocity and subsequently ground-water travel time can be estimated.

In situ monitoring techniques, including tracer tests, are undergoing development and may broaden the range of rock types and conditions for which it is feasible to estimate velocity and ground-water travel time.

NNWSI program investigations also presently include exploratory shaft tests on infiltration rates and sampling of intact fractured blocks for laboratory experiments.

These techniques and investigations are state-of-the-art and should provide a direct determination, with reasonable assurance, of the ground-water flux used to estimate the ground-water travel time.

In addition, DOE believes that reasonable bounds may be developed by less direct methods such as recharge rates determined from water budgets, perturbations of thermal gradients, or in situ monitoring of temporal changes in moistures profiles.

Reasonable assurance, therefore, may be gained in estimating ground-water travel time using results of laboratory testing, state-of-the-art direct determinations in the field or laboratory, and bounding estimates developed by indirect methods.

In addition, reasonable assurance may also be gained by incorporating uncertainty analysis into predictive models.

Although the uncertainty band for a given level of confidence in the calculations may be broad owing to the inability to measure ground-water velocities along all segments of the unsaturated zone travel paths or under all combinations of moisture conditions and matric potentials, the opportunity to invoke conservatism in the ground-water travel time calculations still exists.

B.

• should the ground-water travel time performance objective be limited to ground-water movement in the saturated zone?*

For a repository in the unsaturated zone, DOE does not believe the ground-water travel time objective should be limited to the saturated zone because this would not be an accurate indicator of actual radionuclide transport from the original waste location to the accessible environment (as discussed in the response to Question 2A).

DOE has proposed, in discussions with the NRC on the siting guidelines (10 CFR Part 960), that this performance

objective be limited to only sites located in the saturated zone, with a separate performance objective developed for the geologic setting for sites situated in the unsaturated zone.

(See response to Question 2b)

Question 2.

This question, as stated in the supplementary Information Section, also consisted of two questions which are addressed separately below.

A.

• noes ground-water travel time represent an appropriate measure of performance for a site within the unsaturated zone?"

DOE does not believe that ground-water travel time represents an appropriate measure of performance for a site within the unsaturated zone.

The flux through the repository, both in the unsaturated and saturated zones, is a more appropriate and direct measure of potential cumulative releases to the accessible environment.

The amount of water moving past the wastes is one of the primary factors which set a limit, independent of flow velocity, flow path, or travel time, on the maximum number of curies of a particular radionuclide that can be released from a repository and subsequently be transported by ground water to the accessible environment.

DOE notes that Dames & Moore reached essentially the same conclusion in NUREG/CR-3130 when they concluded that flux and the frequency of wetting events were the primary factors in determining releases from wastes disposed in the unsaturated zone.

Should the NRC, however, choose to keep a minimum 1000-year ground-water travel time as the performance objective for the geologic setting, DOE believes it should logically be applied to sites situated in the unsaturated zone only g_ the travel time will include the combined travel times in the unsaturated zone and the saturated zone so as to better approximate radionuclide transport.

This may necessitate a revision to the definition of the term "disturbed zone,* since the current definition is so vague as to possibly permit defining the disturbed zone as extending downward through the unsaturated zone all the way to the water table or upward through the unsaturated zone all the way to the ground surface.

DOE believes it would be inappropriate to apply the minimum ground-water travel time to only the saturated zone underlying a repository in the unsaturated zone, since such application would conflict with three highly favorable conditions resulting from a highly transmissive (and short travel time) water-table aquifer underlying the repository.

These are:

1.

A highly transmissive aquifer can be expected to transmit any increased throughflow, resulting from increased precipitation during a glacial stage, with less rise in the water table and accordingly less likelihood of saturation of the repository from below.

2.

A highly transmissive aquifer can be expected to significantly dilute any postulated releases from the repository since the characteristically low flux in the unsaturated zone would be a very small fraction of the throughflow in the aquifer.

3.

A highly transmissive aquifer can be expected to significantly disperse any postulated releases from the repository since the dispersivity of the aquifer would be quite high.

Therefore, although a highly transmissive aquifer underlying a repository situated in the unsaturated zone may not provide a 1000-year ground water travel time to the accessible environment, it does not affect the flux through the unsaturated zone (hence it does not affect the cumulative release to the accessible environment over the 10,000 year period of interest).

In addition, although the EPA standard is not based on dose, DOE notes a highly transmissive aquifer underlying a repository in the unsaturated zone provides a means of assuring the reduction of the concentration of (and hence dose received from) any postulated releases due to dilution and dispersion (thereby being applicable to both reactive and non-reactive radioisotopes without consideration of sorption and other retardation processes).

B.

• would an alternative performance objective for the geologic setting (e.g., maximum likely volumetric flow rate of ground water through the geologic repository) be more appropriate?*

DOE believes an alternative performance objective for the geologic setting for a repository located in the unsaturated zone is more appropriate.

DOE has initiated a concerted effort to develop such a performance objective for proposal to the NRC.

This activity is still in progress, and DOE will provide an alternative performance objective by separate letter after the close of the public comment period.

DOE will make every effort to provide the alternative performance objective by May 15, 1984.

DOE believes that the volumetric flow rate (flux) of ground water through a geologic repository located in the unsaturated zone is the most important factor in determining the performance of the repository.

However, DOE cannot at this time propose or endorse a numerical performance objective on maximum flux since the acceptable flux would be site-specific and design-specific.

DOE will continue, however, to consider flux and other factors in its attempt to develop an alternative performance objective for the geologic setting for a repository located in the unsaturated zone.

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u. s. Nuclear Regulatory Commission Washington, D.C.

20555 Attention:

Docketing and Service Branch

SUBJECT:

10 CFR Part 60 -

Proposed Rule on Disposal in the Unsaturated Zone

Dear Mr. Secretary:

The February 16, 1984, Federal Register Notice (Vol. 49, No. 33, FR 5934 to FR 5937) requested comment on 10 CFR Part 60 -

Proposed Rule for Disposal of High-Level Radioactive Wastes in the Unsaturated Zone.

The State of Nevada has reviewed the proposed rule and support documents identified in the subject notice.

We are satisfied with the intent of the proposed rule and feel it is in line with the State's thinking on disposal in the unsaturated zone.

However, we have some comments and suggested changes to improve the proposed rule.

60.2 DEFINITIONS Groundwater:

Redefining "groundwater" (ground water) for a regulatory purpose, particularly in view of the fact that the scientific community will make the field and laboratory determination, is not desirable.

It would be much better for NRC to define and adopt a term or phrase that does not already have a precise meaning in technical community and literature, such as "subsurface moisture."

"Groundwater" already has a widely accepted meaning which does not include vadose or unsaturated zone water.

Unsaturated Zone:

This is a questionable definition because "deepest water table" has been used.

The definition is taken from Lohman et al.

1973 1,

but is not, to our knowledge, widely accepted.

In some terrain and climates it may lead to inclusion of extensive areas of saturation.

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~ecretary of the Commission April 13, 1984 for the unsaturated zone:

Page Two "The unsaturated zone is that region of the earth materials between landsurface and regionally saturated earth materials.

There is discontinuous and incomplete saturation of the interconnected voids in the earth materials, and therefore no continuous positive hydraulic continuity with the regionally saturated zone.

Perched zones (zones with void saturation and local positive potential and hydraulic continuity) may be present within the unsaturated zone."

This follows O.E.

Meinzer's intent in definition, and incorporates local but not regionally perched water.

60.122 SITING CRITERIA The NRC stated conditions favorable for an unsaturated zone repository are based on the current level of knowledge of the various transport processes that may operate in unsaturated zones.

This level of knowledge is still quite limited.

One condition. In particular, Item 8iii (FR5937), seems more specula-tive than others.

An overlying low permeability hydrogeologic unit which prevents or impedes downward moving moisture may likewise impede upward moving water vapor.

If radionuclides are present in upward moving water vapor driven by strong thermal gradients created by the waste, such water vapor may be forced to move laterally below the hydrogeolog ic unit until it condenses.

The condensed water vapor, if concentrated in a localized zone of permeability, might have the opportunity to flow as perched water to points of discharge at land surface.

Considerable uncertainty exists in terms of radionuclide migration with water vapor, but the above scenario suggests that the low permeability hydrogeolgic unit could act to concentrate moisture with radionuclide, and permit discharge of this moisture if the hydro-geologic unit intersects land surface in the vicinity of the repository.

Therefore, it is not clear that the low permeability hydrogeologic unit would be generally favorable if radionuclides migrate with water vapor driven from the repository zone.

1 Lohman, s.w. et al.,1972, Definitions of Selected Ground-Water Forms Revisions and Conceptual Refinements, U.S. Geological Survey Water Supply Paper 1988, 21 p.

Secretary of the Commission April 13, 1984 Page Three Two additional favorable conditions are suggested for NRC's con-sideration:

1. Thermal characteristics of the hydrogeologic unit, such that exposure to high temperature gradients would not cause compaction or volume changes in the packaging or surrounding media.

If compaction should occur, it could influence the hydraulic conductivity in a negative sense, as well as influence the structural stability of the area around the cannisters. Compac-tion due to high thermal gradients is suggested in studies by Constantz. 2

2. Host rock that is capable of accelerated drying.

Due to temperatures reached in the near field, vapor transport in the unsaturated zone is initiated shortly after waste emplace-ment.

This vapor phase moves outward towards cooler regions where it condenses.

The condensed water then moves back towards the cannisters.

This sets up a circulation system which is dominated by the vapor phase; that is, the water phase is small compared to the vapor phase.

Prolonged circulation tends to reduce the total amount of water in the area surrounding the cannisters because more and more vapor is lost to the surrounding system.

Eventually there is no water left as either vapor or condensate; in short, the host medium becomes dry.

Therefore, a host rock which encourages this type of behavior to occur before the cannisters begin to deteriorate (and leak) is advantageous.

However, accelerated drying after the cannisters begin to deteriorate (and leak) may be a disadvantage to long-term isola-tion and requires further a~lysis.

This drying behavior is described in work by Pollock.

An additional comment on conditions for disposal in the unsaturated zone concerns hydrogeochemical considerations.

For the saturated zone 10 CFR Part 60 [60.122(c) (9)] identifies a non-reducing environment as an adverse condition.

It is probable that the unsaturated zone is an oxidizing environment.

An additional condition addressing hyd rogeochem ical conditions in the unsaturated zone is necessary.

2 Constantz, Jim, 1983, "Laboratory Analysis of Water Retention in Unsaturated Zone Materials at High Temperature:, in The Role of the Unsaturated Zone in Radioactive and Hazardou~Waste 15Tsposal, eds. J.W. Mercer, P.S. Rao, I. W:-Mar1ne, Ann Arbor Sciences, 1983, Ann Arbor, Michigan.

Secretary of the Commission April 13; 1984 NRC QUESTIONS FOR PUBLIC COMMENT (FR 5937)

Page Four

1.

• uow can groundwater travel time in the unsaturated zone be determined with reasonable assurance?

Should the groundwater travel time performance objective be limited to groundwater movement within the saturated zone?*

In our opinion, it is premature to answer the first part of the question due to the limited research devoted to the question presently.

Groundwater travel time in the unsaturated zone cannot now be determined with any assurance.

With time, travel time in the unsaturated zone may prove to be as predictable (with similar levels of uncertainty) as travel times in saturated media.

However, groundwater travel time is also subject to considerable uncertainty in the saturated zone, with the uncertainty generally increasing in fracturated low permeability rocks.

From our perspective, there is little confidence that determinations can be made with reasonable assurance in either media presently.

In response to the second question, there seems to be no demonstrated basis for establishing unsaturated zone travel time performance.

It is acknowledged that ground water travel time is an acceptable performance measure in the saturated zone and may be appropriate for the unsaturated zone, however, presently there is no scientific basis to support a precise number for unsaturated zone travel time performance.

The 1,000 year pre-emplacement ground water travel time performance objective now established for the unsaturated zone cannot be projected with reasonable certainty into the unsaturated zone.

We believe this uncertainty does not preclude the use of a 1,000-year travel time, but that its use should be cautioned by the lack of scientific support to base the number.

If the 1,000-year travel time is selected as a performance measure, the NRC should consider revisiting this performance standard later when a better understanding of moisture movement in the unsaturated zone is known.

2.

• ooes groundwater travel time represent an appropriate measure of performance for a site within the unsaturated zone, or would an alternative performance objective for the geologic setting, (e.g., maximum likely volumetric flow rate of groundwater through the geologic repository) be more appropriate?

3 Pollock, David Warren, 1982, "Fluid Flow and Energy Transport in a High-Level Waste Repository in Unsaturated Alluvium", Ph.D.

Thesis, University of Illinois -

Urbana, Champaign, Illinois.

Secretary of the Commission April 13~ 1984 Page Five Ground-water (unsaturated zone moisture) travel time may be appropriate in the unsaturated zone, and associated time credit to the accessible environment be considered as a measure of performance,

however, the Commission should recognize several important factors believed to be involved in a travel time consideration of performance.

1.

Travel time, and direction, may prove to be different for liquid and vapor phase moisture in the unsaturated zone.

2.

Radionuclide transport may prove more complex in unsaturated flow than in saturated flow, and not closely related to moisture flux.

Performance based upon maximum likely volumetric flow rates may be even more speculative than groundwater travel time.

Presently, recharge rates (a measure of volumetric flow rate) cannot be determined with precision, especially during variable climatic conditions.

We believe that, although not ideal, ground water travel time in the unsaturated zone may be an acceptable performance measure at the present time, if the factors described previously are considered.

Alternative to a

travel time performance standard, it is suggested the EPA standard be the performance measure by which the geologic setting is judged, or the Commission utilize the approach set forth in 60.113(b) of 10 CFR Part 60.

This section prov ides the Commission with the flex ibi 1 i ty to specify var ia-t ions in performance objectives on a case-by-case basis.

The prime reason for suggesting this approach is the current absence of detailed understanding of moisture regimens in unsaturated zone environments, and the associated radionuclide transport by both liquids and gases in this type of environment.

As more established relationships and techniques of analysis are developed for each site, an appropriate performance objective may be possible.

If you have any questions, please do not hesitate to contact me.

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Carl A. Jonson Technical Manager

EDISON ELECTRIC I N 5 TIT UTE The association of electric companies 111119th Street, N.W.

Washington, D.C. 20036 Tel: (202) 828-7400 Apr i 1 Secretary of the Commission U.S. Nuclear Regulatory Commission Washington, D.C.

20555 Attention:

Docketing and Service Branch Re:

Proposed Rule: Disposal of High-Level Radioactive Wastes in the Unsaturated Zone; 10 CFR Part 60 (49 Fed. Reg. 5934)

Dear Mr. Secretary:

JOHN J. KEARNEY, Senior Vice President C:l<E' ED USIRC

'84 APR 16 P 1 :55 These comments are being submitted by the Edison Electric Institute (EEI) and the Utility Nuclear Waste Management Group (UNWMG) in response to the above-referenced notice.

We support amendment of the Commission's regulations in 10 CFR Part 60 so that the technical criteria for geologic disposal in the saturated zone may be equally applicable to disposal within the unsaturated zoned.

In particular, we support adoption of the specific amendments presented in the Commission's notice as appropriate for providing for such disposal with one exception.

Proposed §60.122(b) (7) would apply to disposal in both the saturated and unsaturated zones.

As indicated in the rulemaking notice, however, determining groundwater travel time in the unsaturated zone may not be necessary nor always be possi ble.

Under such circumstances, inability to demonstrate a "groundwater travel time along the fastest path of likely radionuclide travel from the disturbed zone to the accessible environment that substantially exceeds 1,000 years" should not amount to the absence of a favorable condition.

This is especially so in a case where the conditions prescribed in proposed §60.122(b) (8) exist.

Accordingly, the groundwater travel time identified as a favorable condition in proposed §60.122(b) (7) should not apply to disposal in the unsaturated zone.

To further amplify our position, we offer the following answers to the two questions presented in the Commission's notice.

1.

How can groundwater travel time in the unsaturated zone be determined with reasonable assurance?

Should the groundwater travel time performance objective be limited to groundwater movement within the sat urated zone?

Po, C P A'

Secretary of the Commission April 13, 1984 Page Two EEI/UNWMG are not aware of any general, acceptable method for determining groundwater travel time in the unsaturated zone with reasonable assurance.

However, there is no reason to strictly limit the groundwater travel time performance objective to groundwater movement within the saturated zone.

We agree with the Commission ' s current thinking on this issue, as described in the rulemaking notice, that if DOE can demonstrate in a particular case with reasonable assurance that travel time for groundwater movement through the unsaturated zone can be quantified, then the Department should be allowed to include such travel time when demonstrating compliance with 10 CFR §60. 113(a) (2).

2.

Does groundwater travel time represent an appropriate measure of performance for a site within the unsaturated zone, or would an alternative performance objective for the geologic setting, (e.g., maximum likely volumetric flow rate of groundwater through the geologic repository) be more appropriate?

EEI/UNWMG believe that groundwater travel time can, in certain circumstances, represent an appropriate measure of performance for a site within the unsaturated zone.

Where it does not, however, we do not believe that an alternative performance objective, such as maximum likely volumetric flow rate, would necessarily be more appropriate.

Rather, consistent with one of the alternatives posed by the Commission in the rulemaking notice, we would favor utilization of the approach set forth in 10 CFR §60.113(b) providing the Commission with the basis to specify variations in performance objectives on a case-by-case basis, as long as the overall system performance objective is met.

In this connection, the Commission should specifically note in the statement of considerations accompanying the adoption of a final rule that the approach in section 60.113(b) may be particularly appropriate in the case of disposal in the unsatu-rated zone.

We appreciate this opportunity to comment on the proposed rule and hope that this response will be of assistance to the Commission.

JJK:rsd Respectfully submitted, earney enior Vice Preside

~OPl

-s4 APR 16 P 1 :30

~h:tte of ~liohe Jshmb zmb :J rouibence :Jlanhtftotts EXECUTIVE CHAMBER PROVIDENCE J. JOSEPH GARRAHY GOVERNOR Mr. Samuel J. Chilk Secretary of the Commission U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Mr. Chilk:

April 13, 1984 I am pleased to submit on behalf of the State of Rhode Island our comments on the Commission's proposed rule regarding disposal of high-level radioactive wastes in the unsaturated zone.

These comments were drafted with the assistance of members of the Rhode Island crystalline Rock Project Review Team, which was formed last year to respond to the Department of Energy's high-level waste repository program.

Contributors to this effort were Mr. Victor Bell, Chief of the Office of Environmental Coordination, R.I. Department of Environmental Management, and Mr. Daniel Varin, Chief of the Office of State Planning.

Any questions regarding our comments may be directed to me at (401) 277-3500.

Sincerely, Project Facilitator 72 orange St.,

GOVERNOR'S ENERGY OFFICE * ~~~~~

PROVIDENCE, RI 02903

• 401/277-3370

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COMMENTS BY THE STATE OF RHODE ISLAND ON THE PROPOSED RULE REGARDING THE DISPOSAL OF HIGH-LEVEL RADIOACTIVE WASTES IN THE UNSATURATED ZONE Most ground water in Rhode Island is drawn from relatively shallow stratified-drift aquifers.

Hydrologists in the Division of Land Resources have informed us that in many areas the water table is but a few meters below the surface.

While some wells tap water which collects in rock fractures, such water also is found rela-tively close to the surface.

According to our Water Resources Board, only a half-dozen or so water supply wells go below 500 feet (150 meters).

This suggests a thin unsaturated zone.

It is extremely unlikely, then, based on present evidence, that the Department of Energy could locate a nuclE:a:.: waste :;:-epo2itory in the unsaturated zone in Rhode Island and be able to satisfy its own minimum depth requirement of 200 meters (DOE siting guidelines, Sec. 960.4-2-S(d)).

on the other hand, as indicated in the pro-posed rule, unsaturated zones in other areas, particularly those found in arid or semi-arid regions of the country, may be of suf-ficient thickness to allow the minimum depth requirement to be met.

Regardless of whether a site is chosen within the saturated zone or the unsaturated zone, our primary concern over the long term should be the isolation of nuclear waste from the accessible en-vironment.

Disposal in the unsaturated zone has the advantage of minimizing contact between the implanted waste and ground water.

As ground water is the most likely pathway for radionuclides to the outside, Rhode Island would support considering such an option for disposal.

We have stated on a number of occasions, particularly in regard to DOE's siting guidelines, that the repository should not contaminate ground water of potential use by present or future generations.

The relative dryness of a thick unsaturated zore would help reduce the probability that contaminated ground water would reach Man.

However, ground water does flow in the unsatu~ated zone, and to demonstrate that its repository complies with stated performance objectives, the Department of Energy will have to assess ground water flow in both liquid and vapor phases.

Ground water travel time in the unsaturated zone will be difficult to calculate, as the proposed rule indicates, because of "large associated uncer-tainties."

Some quantification and generalization concerning ground water travel time will be necessary nonetheless to determine if proposed "potentially adverse conditions" (c) (22) and (c) (23) are present (49 FR 5937).

Absent another parameter upon which to evaluate performance, DOE will have to attempt a "reasonable" estimate of ground water travel time to be corroborated to the

COMMENTS Page TWO extent possible when the Department characterizes the candidate site.

As there may be much debate over which level of data is "reasonable" in the earlier stages of screening, Rhode Island would urge DOE and NRC to consult freely with the state geological contacts on this matter.

In its consideration of ground water flow (however that parameter is to be determined), we would recommend that NRC direct DOE to examine how the rate and direction of ground water flow is affected by withdrawal.

Rhode Island's experience indicates that changes do occur in shallow aquifers and in some cases these changes are sig-nificant.

This would appear to be a matter of concern in any case where ground water flow is discontinuous and heavily dependent on spatial and temporal events, as in the unsaturated zone.

STATE OF WISCONSIN RADIOACTIVE WASTE REVIEW BOARD

'84 APR 13 P 3 : 11 April 11, 1984 921 Tenney Building 110 E. Main Street Madison, WI 53702 (608) 266-0597 (608) 267-7615 Mr. Samuel J. Chilk, Secretary U.S. Nuclear Regulatory Commission Washington, D. C.

20555 Attn:

Docketing & Service Branch Re:

Comments on the Proposed Rule for Amending 10 CFR Part 60, Disposal of High-Level Radioactive Wastes in the Unsaturated Zone The Wisconsin Radioactive Waste Review Board has reviewed the proposed revisions to 10 CFR 60 for disposal of high-level radioactive wastes in the unsaturated zone.

This proposed rule appears to have considerable merit since it opens up another alternative for disposal.

It also appears the Commission has identified the pertinent technical concerns with disposal in the unsaturated zone.

Thank you for the opportunity to comment on this rule.

Sincerely, James S. Kleinhans Executive Director cc:

Radioactive Waste Review Board Members Technical Advisory Council Members Policy Advisory Council Members j\\cknowledgea by tl\\r. d/4~

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ARGONNE NATIONAL LABORATORY 9700 Sourl-l CAss AVENUE, ARGQNNE, llliNOis 604}9 March 30, 1984 Secretary of the Commission U.S. Nuclear Regulatory Commission Washington, DC 20555 Attn:

Docketing and Service Branch Sir:

This is a comment to proposed NRC amendments to 10 CFR Part 60 concerning unsaturated geologic media.

(Ref. Federal Register, Vol 49, No. 33, pg 5934.)

Proposed Amendment:

Potential for vapor transport of radionuclides from the underground facility located in the unsaturated zone to the accessible environment, as a potentially adverse condition.

This is an ambiguous, and as written, meaningless statement that could, under certain conditions, be applied to any repository site.

The detailed explanation in NUREG-1046, pg. II.b.8. is confusing and does little to address the issues.

Several points need to be clarified.

1) What is vapor transport? If it is transport of radionuclides in the vapor phase, then it is not unique to the unsaturated zone for such transport will occur at any site until resaturation occurs.

If it is transport of radio-nuclides in water vapor through rock, then it should not be identified as a separate transport mode because transport by water vapor meets the NRC definition of groundwater.

Also, according to the NRC (NUREG/CR-3206, pg. 118), no soluble contaminants will be transported away from the repository by water vapor, making the proposed amendment unclear.

2) Where is the vapor transport occurring and when it is important? Vapor phase transport might occur in the repository rock.

However, before such transport could occur, th~ contaminants have to get to the rock.

This would involve vapor phase transport of contaminants from the waste package, across potentially significant void spaces, to the rock.

Transport in these two diverse media is likely to involve different processes and should be distinguished since the technical references refer only to transport through rock.

It makes little sense to mention vapor phase transport in rock unless the terms and conditions are well defined.

It could make sense to identify vapor phase transport from the waste package to the rock as an advantage for the unsaturated zone, since it is likely far fewer radionuclides (amount and number) would be transported through the 11 vapor 11 (unsaturated repository) than would be transported through liquid (saturated repository).

This void space is an additional barrier that impedes the movement of many contaminants.

Certainly this is an area that deserves further attention by the NRC staff.

n K. Bates mical Technology Division JKB:rr U.S. DEpARTMENT of ENmqy T~E.~~~y of ?',KXPl 4.fr.1. t/

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(208) 883--0153 (208) 875-0147 P.O. Box 48. Viola. Idaho 83872 Afineral Resources Waste Jfanagement Hrdroxe(!kf K.r Geological Engineering *

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Mr. Jeff Pohle Division of Waste Management Mail Stop 623-SS March 15, 1984 Contract No. NRC 82-046 Communication No. 36 A

U. S. Nuclear Regulatory Commission W

Wash i ngton, D. C., 20555 IC

Dear Jeff:

This letter constitutes the comments of Williams.nd Associates, Inc.

on NRC NUREG 1046 entitled "Disposal of High Level Radioactive Wastes in the Unsaturated Zone:

Technical Considerations 11 As you pointed out in your note, the NUREG is a draft report for comment.

We are directing these comments to you with the anticipation that you will transfer them to Tom Nicholson.

The primary review of the report was done by Dr.

George Bloomsburg.

I have added some comments of my own and edited his.

The comments are as follows.

This report explains the differences between saturated and unsaturated zones in a clear and concise manner.

Comments are presented by page number as follows.

Page 3 -

Defining groundwater as the entire volume of water below the earthps surface is a

somewhat unusual but very appropriate approach.

Page 4 - Paragraphs 2 and 4 relate to movement due to gravity in the unsaturated zone **

However, at the high moisture tensions that occur in arid regions with a deep water table the movement may be vertically upward due to evaporation at the surface.

Soil moisture does not necessarily ultimately percolate downward in arid environments.

Page S -

Top of page In our opinion the flow into fractured granite would be considerably different than fractured tuff.

In some types of tuff, water in the ~ractures would be

" absorbed". into t he adjacent intergranular pores.

This would not occur in granite because it is less porous.

Ther efore, downward movement may not be as

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2 rapid in t~ff because the fractures would dewater due to water moving out into the pores.

These ideas should be investigated either in the laboratory or in the field as discussed at the bottom of page 6 and top of page 7.

Pages 7 and 8

These pages present a good discussion of heat f 1 ow from the reposi t _ory and the formation of a

"vapor envelope" around the repository.

Page 10 -

Paragraph 4

The authors point out that under unsaturated flow conditions the liquid flow occurs only on the surface of mineral particles wherefore the removal of radionuclides is more likely than at saturated tlow conditions.

However, according to the heat, liquid and vapor flow analysis, the flow away from the repository is in the form of vapor while the flow toward the repository is in the form of liquid on the particle surfaces.

The radionuclides therefore would have to be in the vapor phase, not in the liquid phase.

Pages 14 and 15 Vapor and gaseous transport of contaminants -

The discussion of the transport is good but it would be advisable to conduct additional research on this topic by means of a physical model that could be used to verify the mathematical model developed at Arizona.

A complete analysis of the "vapor envelope" might show that there is no movement of either liquid or vapor from the envelope to the surrounding material.

An energy balance of this phenomenon would have the heat produced at the repository constitute the energy source for the recirculating flow of vapor away from the repository and flow of liquid toward the respository.

Pages 20 We agree with the discussion on

shafts, boreholes and backfill regarding design.

Specifically the proper design may be the opposite of the proper design for such structures under saturated flow conditions.

If you have any questions regarding these comments, please call.

REW:sl cc:

appropriate NRC offices M. D. Mifflin Sincerely, l(o'i W~/~

Roy E. Wi lliams Ph.D. Hydrogeology Registered in Idaho WILLIAMS AND ASSOCIATES, INC.

Mar 14 -84 hom the pen of EMERY NEMETHY LC() {

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BOX C 1 BLO,,c:-uURG 17815 ATT: DOCKEl ING & SERVICE BRA~CH NRC - Wash, DC 20555 Re : Fed Reg Notice - ieb 16-84 HLW Disposal Gentlemen -

DOC.K[T[r, U'3NRC'.

• a4 HAR 19 A11 : 1 t The discussion in this notice limits itself to waste burial in saturated a nd unsaturated zones.

Has the Commission given any consideratmon to above-ground repositories for HL?

Over the past few years, t his approach ha s been written about, a number o i times.

Should HLW be entombed in tnis manner, and if the contaiument were in the snape of a pyramid,

• it might withstand eartnquakes,

tornadoes and concussion from bomb blasts.

• (tetrahedron)

~cknowl dg

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Secretary of the Commission U.S. Nuclear Regulatory ColIUllission Washington, DC 20555 Sir:

"84 OOtKETEn U'5 1R" HAR 12 March 6, 1984

JOC J l.J BER R-l,D (!)

POOP,J

£D RULE

(_4,q~st/$

P1 :38 RE: 10 CFR Part 60, Disposal of High-Level Radioactive Wastes in the Unsaturated zone, Proposed amendment of rul es F~ede'.ifu.ic t t 1er, V. 49, No. 33 OCKETING r

BRA CH d"

• It is extremel y important to be aware of t lie act t hat "unsaturate 1.s NOT synonymous with a low moisture content. 'the last paragraph beginning on ~5934 of the Federal Register notice referred to states that "Perhaps the most positive as* ect associated with di sposal of HLW within the unsaturated zone is that the HLW would be emplaced in a relatively dry (i.e., low moisture content) geologi c medium."

This implies that all unsaturated rocks are dry.

This is patently untrue.

Unsaturated merely means that the pore space in the rock is not filled with water.

The actual water content depends on the amount of pore space.

Thus a rock that has a porosity of 5% and which is saturated has exactly the same amount of contained water as a rock with a porosity of 10% which is 50% saturated.

In fact, many of the rocks to which the USGS refers to as unsaturated have a very high porosity and a relatively high saturation, alt hough less than 100%,

and in fact contain much more water than saturated rocks with a lower.porosity.

Many volcanic tuffs in the Great Basin, in fact, contain considerably more water than granites in the more humid regions, even though the granites are saturated and the tuffs are not.

Water content and the speed of the movement are the im-portant factors; the percentage of "saturation" is really an insignificant factor.

With regard to the question of whether or not groundwater travel time represents an appropriate measure of performance for a site within the unsaturated zone, I feel that it i s absolutel y essential that the same standar d of measure be applied to all rock types and all sites, regardless of their sett *ng with respect to the water table.

I have no idea how groundwater travel time in the unsaturated zone can be determined; neither do I have any idea how gr oundwater travel time through salt can be measured.

Maximum likely volumetric flow rate of groundwater through the repository might well be a more appropriate measure of performance, but if so, then this same measure should be applied to all rock types and all sites. It would be absolutely unacceptable to use the alternative performance measure for a rock situated in the unsaturated zone (even though containing a considerable amount of water and, in fact, possibly be "near" saturation) and apply a different measure for a site in a salt host rock, whi ch in fact contains an amount of water almost defying measurement and with a "groundwater travel time" (if that term can even be applied) that is so slow as to be beyond comprehension.

Thank you for the opportunity to comment.

Sincerely,

~JJ~

Benjamin Dover Geologist 657 Indian Mound Road Columbus, Ohio 43213 Ackno I dged by carc!'/h?l?J:. -~

Secretary of the Conunission U.S. Nuclear Regulatory Couunission Washington, DC 20555 Sir:

OOlKE Ef U5~1R" HAR 12 March 6, 1984 RE: 10 CFR Part 60, Disposal of High-Level Radioactive Wastes in the Unsaturated zone, Proposed amendment of rules

~,t 1er, v. 49, No. 33 OCKETING r

BRA CH It is extremely important to be aware of tlie act that "unsaturated" 1.s NOT synonymous with a low moisture content. ~he last paragraph beginning on 'p.'""°5934 of the Federal Register notice referred to states that "Perhaps the most positive as* ect associated with disposal of HLW within the unsaturated zone is that the HLW would be emplaced in a relatively dry (i.e., low moisture content) geologic medium."

This implies that all unsaturated rocks are dry.

This is patently untrue.

Unsaturated merely means that the pore space in the rock is not filled with water.

The actual water content depends on the amount of pore space.

Thus a rock that has a porosity of 5% and which is saturated has exactly the same amount of contained water as a rock with a porosity of 10% which is 50% saturated.

In fact, many of the rocks to which the USGS refers to as unsaturated have a very high porosity and a relatively high saturation, although less than 100%,

and in fact contain much more water than saturated rocks with a lower.porosity.

Many volcanic tuffs in the Great Basin, in fact, contain considerably more water than granites in the more humid regions, even though the granites are saturated and the tuffs are not.

Water content and the speed of the movement are the im-portant factors; the percentage of "saturation" is really an insignificant factor.

With regard to the question of whether or not groundwater travel ti.me represents an appropriate measure of performance for a site within the unsaturated zone, I feel that it is absolutely essential that the same standard of measure be applied to all rock types and all sites, regardless of their setting with respect to the water table.

I have no idea how groundwater travel time in the unsaturated zone can be determined; neither do I have any idea how groundwater travel ti.me through salt can be measured.

Maximum likely volumetric flow rate of groundwater through the repository might well be a more appropriate measure of performance, but if so, then this same measure should be applied to all rock types and all sites. It would be absolutely unacceptable to use the alternative performance measure for a rock situated in the unsaturated zone (even though containing a considerable amount of water and, in fact, possibly be "near" saturation) and apply a different measure for a site in a salt host rock, which in fact contains an amount of water almost defying measurement and with a "groundwater travel time" (if that term can even be applied) that is so slow as to be beyond comprehension.

Thank you for the opportunity to cOIIDI1ent.

Sincerely,

~j)~

Benjamin Dover Geologist 657 Indian Mound Road Columbus, Ohio 43213 Acknowl dged by carr1. l/J. 3/iJ:.,j&f..

l)_ s. N' I D

[7590-01]

DOCK TEO USh~C NUCLEAR REGULATORY COMMISSION

• a4 FEB 13 P 4 :07

_ 10 CFR PART 60' Disposal of High-Level Radioactive Wastes in the Unsaturated Zone AGENCY:

Nuclear Regulatory Commission.

ACTION:

Proposed rule.

SUMMARY

The Nuclear Regulatory Commission (NRC) is considering amending its rules on the disposal of high-level radioactive wastes (HLW) in geologic repositories so that the technical criteria for geologic disposal in the saturated zone may be equally applicable to disposal within the unsaturated zone.

The amendments are being proposed in response to public comments on the proposed technical criteria for geologic disposal in the saturated zone.

Final technical criteria adopted by the Commission for disposal of HLW in the saturated zone were published in the Federal Register on June 21, 1983.

DATES:

Comment period expires

• APR 16 1984 Comments received after this date will be considered if it is practical to do so, but assurance of consideration cannot be given except as to comments received on or b~fore this date.

.c::

ADDRESSES:

Send comments or suggestions to the Secretary of the Commission, U.S. Nuclear Regulatory Commission, Washington, DC 20555, Attention:

Docketing and Service Branch.

Copies of comments received may -be examined at the NRC Public Document Room, 1717 H Street NW., Washington, DC 20555.

1

.J

[7590-01]

FOR FURTHER INFORMATION CONTACT:

Dr. Colleen Ostrowski, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC, 20555, telephone (301)427-4343.

SUPPLEMENTARY -INFORMATION:

Background

On February 25, 1981 the Nuclear Regulatory Commission (NRC) published a rule that established procedures for licensing the disposal of HLW in geologic repositories (46 FR 13971).

NRC published proposed technical criteria to be used in the evaluation of license applications under those procedures on July 8, 1981 (46 FR 35280).

In response to solicitation for public comments on the proposed technical criteria NRC received 93 comment letters. The Commission considered all public comments in developing the final technical criteria which were published on June 21, 1983 (48 FR 28194).

Several commenters on the proposed rule, including the U.S. Department of Energy (DOE), the U.S. Department of the Interior, and separately the -

U.S. Geological Survey (USGS), took issue with a statement made by the '

Commission at 46 FR 35281 which explained that the proposed technical cri-teria were developed specifically for disposal in saturated geologic media because DOE plans at that time called for HLW disposal at sufficient depth to be situated in the hydrogeologic region termed the saturated zone.

The commenters considered disposal in the unsaturated zone1 to be a viable alternative, and noted that since the technical criteria were generally applicable without regard to the possibility of saturation, their scope and applicability should not be unduly restricted.

DOE, in its comments on this issue, suggested that since opportunities may arise for explora-tory studies in unsaturated geologic media, the Commission should reexamine the rule and make whatever changes are necessary to ensure that the rule will apply to all geologic media.

The U.S. Department of the Interior urged that the rule be modified because, under appropriate conditions, the unsaturated zone could provide one more natural barrier to the movement of radionuclides from the geologic repository to the water ta~le.

1The definition of the term "unsaturated zone" is derived from U.S. Geological Survey Water Supply Paper 1988 (Washington, DC, 1972).

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The Commission has determined that disposal of HLW within the unsatu-rated zone is a realistic alternativ~ to disposal within the saturated zone, provided that the site and the geologic repository design are carefully selected, and are capable of meeting the performance objectives of 10 CFR Part 60.:-In reaching this determination, the Commission has examined the

~

arguments presented by the public commenters as well as the analysis of the principal issues associated with unsaturated zone disposal described in the NRC staff technical support document (draft NUREG-1046) prepared in conjunction with the proposed amendments.

This document identifies the positive aspects and possible concerns associated with disposal in the unsaturated zone and explains why the Commission has developed the following proposed amendments.

Other issues which were discussed by public commenters but which did not result in proposed changes to the final rule are also addressed in the technical support document.

Upon publication, a copy of draft NUREG-1046 entitled "Disposal of High-Level Radioactive Wastes in the Unsaturated Zone:

Technical Considerations" will be placed in the Public Document Room, 1717 H Street NW.,

Washington, DC 20555.

Since this document is available to the general public2, only a summary discussion of these issues is presented below.

Issues Examined By The Commission The depth to the regional water table varies throughout the United States.

Potential geologic repository sites within unsaturated geologic media may be identified in arid to semi-arid geographic regions of the country because such regions generally are characterized by a deep regional water table and hence, a relatively thick unsaturated zone.

The unsaturated zone in certain arid regions of the United States has been documented as extending to depths of approximately 600 meters below the ground surface.

In contrast, the unsaturated zone in humid regions is often only a few meters thick, or entirely non-existent.

2Free single copies of Draft NUREG-1046 may be requested for public comment by writing to the Publication Services Section, Division of Technical Information and Document Control, U.S. Nuclear Regulatory Commission, Washington, D.C.

20555.

\\

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Perhaps the most positive aspect associated with disposal of HLW within the unsaturated zone is that the HLW would be emplaced in a relatively dry (i.e., low moisture content) geologic medium.

The Com-mission considers the relatively low moisture content of unsaturated sediment and rock as a positive aspect of HLW disposal-in the unsatu-rated zone because the lack of available moisture could reduce leaching of the waste packages and thus, significantly reduce the likelihood of radionuclide transport by groundwater3 migration.

Further, it is gen-erally recognized that vertical groundwater flux in the unsaturated zone is very small.

A credible pathway for the migration of water soluble contaminants from a geologic repository located in the unsaturated zone to the accessible environment would probably be vertically downward to the underlying regional water table, and subsequently through the saturated groundwater units to the regional discharge points.

The Commission has reviewed several other issues that are of general concern to disposal of HLW in geologic repositories, regardless of the hydrogeologic zone involved.

Such issues include the effects of climatic changes on the regional hydrologic systems, the potential for human intru-sion into the geologic repository, and the effects of geologic processes (e.g., tectonism) on the structural stability of the geologic repository.

The Commission does not believe that any of these issues would negate the generic concept of HLW disposal within the unsaturated zone.

However, since the relative importance of these issues will depend upon natural conditions existing at a particular site, each must be evaluated on a site-by-site basis.

Vapor transport of contaminants has been identified by the Commission's staff as a potential concern associated with HLW disposal in the unsaturated zone.

In unsaturated geologic media, water is transported in both liquid and vapor phases.

The relative contribution of transport via liquid and vapor phases, and their direction of movement with respect to a geologic 3The Commission recognizes that the term "groundwater" is generally applied by the technical community to water which occurs beneath the water table (i.e., phreatic water) while the term "vadose water" is more accurately applied to the soil water, gravitational water and capillary water which occur in the unsaturated zone (zone of aeration, vadose zone).

However, for the sake of simplicity, groundwater is defined in the proposed amend-ments as all water which occurs below the Earth's surface.

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repository will have a direct influence on the containment of contami-nants.

Vapor transport, particularly when a thermal gradient is imposed may provide a possible mechani.sm for radionucli de migra~ion from a geo-logic repository.

However, positive aspects associated with vapor trans-

... p~r-t i.n !:,be unsaturateq_ zone_ may a 1 so be discerned s i nee water vapor formed -=-::

near the geo~ogic repository may flow through air-filled openings and partially drained fractures, resulting in a drying of the surrounding host rock.

• This drying zone may extend hundreds of meters from the geo-logic repository, and -thus may inhibit the movement of soluble contaminants.

Therefore, the Commission views vapor transport as another issue which must be evaluated on a case-by-case basis to determine its effects (whether favorable or potentially adverse) on a particular site.

Other Comments Considered by NRC:

The Commission has reviewed the following six issues related to HLW disposal within the unsaturated zone which were addressed in the public comments on the proposed rule, as well as in a recent USGS publication, 4 and has determined that the final rule (48 FR 28194) accommodates these concerns.

More detailed discussion of these issues is presented in draft NUREG-1046.

Minimum 300-meters depth for waste emplacement One commenter on the proposed 10 CFR Part 60 technical criteria who advocated applying the rule*equally to the saturated and unsaturated zones considered it necessary to change the siting criterion which sets a minimum depth of 300 meters for waste emplacement.

However, the commenter incor-rectly identified this provision (see§ 60.122(b)) as a requirement, rather than as a favorable condition.

The Commission notes that favorable condi-tions are those which may enhance waste isolation potential.

Hence, a minimum depth of 300 meters for waste emplacement is considered a favorable condition because the deeper the HLW is emplaced, the less likely it is to 4Roseboom, E. H. Jr., 1983, Disposal of High-Level Nuclear Waste Above the Water Table in Arid Regions, U.S. Geological Survey Circular 903, Washington, DC, p. 21.

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be disturbed.

Viewed in that light this depth is a favorable condition, irrespective of hydrogeologic zone.

Since the unsaturated zone may extend to depths of up to 600 meters, the Commission considers this favorable condition to be a realistic one for both the saturated and unsaturated

.

• zones ~ Therefore,-this. provisibn of the rule has not been modified.

Requirements for sealing shafts and boreholes In USGS Circular 903 the view was expressed that, with respect to a geologic repository within the unsaturated zone, sealing shafts and boreholes tightly to inhibit water movement may be undesirable.

The reasoning behind this view is that although shafts and boreholes need to be carefully sealed in the saturated zone so that they do not become future conduits for radionuclide migration, they may have an entirely different relation to an unsaturated zone repository.

Shafts and bore-holes would increase the amount of water moving through a geologic repository located within the unsaturated zone only if they diverted a significant amount of runoff to the subsurface.

The Commission has reviewed both the arguments of the USGS and the provisions of the final rule relating to the design of seals for shafts and boreholes(§ 60.134).

The provisions of§ 60.134 appear to be gener-ally applicable to seals of shafts and boreholes in both hydrogeologic zones.

Therefore, the Commission does not consider it necessary to modify

§ 60.134 at this time.

Backfill requirements Another issue which has been identified both in public comments on the proposed technical criteria and in USGS Circular 903 pertains to the necessity of backfill in a geologic repository located within the unsatur-ated zone.

The USGS expressed the view that the role of backfill in the unsaturated zone would be the opposite of that in the saturated zone.

Backfill material that would inhibit the flow of water to, and radionuclide migration from, the waste packages may be highly desirable in the saturated zone.

In the unsaturated zone, however, the designers of a geologic repos-itory may wish to promote drainage.

The opinion has been expressed that within the unsaturated zone backfill should allow groundwater to drain 6

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readily, rather than serve as a barrier to drainage. It was suggested in US.GS Circular 903 that if backfi 11 i s necessary to preserve structural or waste package integrity, a relatively permeable materia1 (e.g., cobble--

sized rock) could be used to permit continued drainage.

---

~- T_he:. fina l:==1'ule pubj ished_ by the Commission on June 21,.1983 contained =

only the general functional statement that the engineered barrier system (including backfill) be designed to assist tne geologic setting in meeting the performance objectives for the period following permanent closure

(§ 60.133(h), 48 FR 28227).

This provision, as promulgated, should be responsive to the concerns discussed above.

Waste package design criteria As defined at§ 60.2, the term "waste package 11 means 11the waste form and any containers, shielding, packing and other absorbent materi al s imme-diately surrounding an individual waste container" (48 FR 28219).

The point has been raised t hat because of the different nature of the emplace-ment environment designs of waste package components for the saturated and unsaturated zones may be quite different.

The Commission recognizes that several characteristics of the emplacement environment (e.g., oxida~

tion conditions, lithostatic pressure, geochemistry, contact with ground-water, etc.) may vary significantly between the two hydrogeologic zones.

This variation of emplacement environment may necessitate that DOE consider alternative designs for waste packages (including waste form, canisters, overpack~ etc.) for geologic disposal in the unsaturated zone.

The Commission has reviewed the performance objectives which pertain to the waste package(§ 60.111 and§ 60.113), and believes that the provisions, as currently wri~ten, are equally applicable to waste packages emplaced within either the saturated or unsaturated zone.

Similarly, the specific design cri teria for the waste package and its components(§ 60.135, 48 FR 28227) have been determined to be generally applicable to both zones.

Therefore, no changes have been made to the provisions of§§ 60.111, 60.113, or 60.135.

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Ventilation The issue of restricting the number of ventilation shafts associated with a geologic repository was addressed in USGS Circular 903.

In the case of the saturated zone, the number of ventilation shafts may be kept 4

at-~ mi njmum si.f)ce the-:$hafts could constitute potential pathways to the

~

accessible environment.

In USGS Circular 903 it is stated that in the case of the unsaturated zone additional shafts for ventilation would not compromise the geologic repository's performance because sealing shafts in the unsaturated zone is much simpler and of less consequence than in the saturated zone.

Several potential benefits were cited by the USGS to sup-port this view--e.g., reducing the problem of thermal load in the early phases of the geologic repository, removal of any water vapor during the operational period, drawi~g large amounts of desert air through the geologic repository to promote even drier conditions and increasing worker safety by providing alternative sources of ventilation and escape routes.

The number of ventilation shafts _included in any geologic repository will be decided by the designer--DOE.

No provision of 10 CFR Part 60 expressly limits the number of ventilation shafts that a geologic reposi-tory may contain.

What is important is that the surface facility venti~ -

lation systems comply with the design criteria in§ 60.132(b) (48 FR 28226) and that the underground facility ventilation system be designed in accordance with§ 60.133(g) (48 FR 28227).

The Commission considers the design requirements for the ventilation systems set forth -in-§§ 60.132 and 60.133 to be applicable to both the saturated and unsaturated zones.

As long as the ventilation system complies with provjsions of§§ 60.lll(a),

60.132, and 60.133 and does not compromise the integrity of the site to host a geologic repository, DOE will have broad flexibility in designing the system.

Exploratory boreholes Provisions relating to site characterization are set forth in the final rule at§ 60.10 (48 FR 28219).

Section 60.10(d)(2) requires that the number of exploratory boreholes and shafts be limited to.the extent practi cal, consistent with obtaining the information needed for site charac-terization.

The view was expressed in USGS Circular 903 that in the 8

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unsaturated zone, if the host rock already has a high vertical permeability, there is no reason to limit the number of drill holes.

Thus, the USGS noted that if necessary, a proposed geologic repository _could be explored like an ore body or coal bed, with drill holes every few.hundred feet on a

_ r~c~angu] ar gd.(;f; --

The Commission's view on the importance of not compromising the integrity of a site during the site characterization program of testing and exploration has been clearly stated at 44 FR 70409.

However, if DOE should opt for a site exploration and characterization program which includes plans for drilling numerous boreholes then DOE would have the burden of showing the Commission that the ability of the site to isolate HLW has not been compromised during these activities.

Groundwater Travel Time in the Unsaturated Zone:

The concept of groundwater travel time generally is applied in evaluations of saturated flow systems, where flow is continuous and temporal fluctuations in the potential of the systems are small.

In contrast, water movement in the unsaturated zone is generally discon-tinuous and strongly dependent upon initial conditions (e.g., magnitude" -

and spatial -and temporal distribution of recharge events) and the con-ductive properties of the partially saturated geologic media, which vary with moisture content.

Reliable calculations and predictions of ground-water travel times and -velocities require knowledge of these conditions and properties.

Within the unsaturated zone the movement of a given volume of water over a given distance depends very strongly upon the nature of the recharge events.

Additionally, the material properties (e.g., motsture characteristic curves, porosity, irreducible saturation, etc.) and the initial conditions (e.g., saturation, capillary pressure, matric potential ) may be extremely-difficult to measure on a representa-tive scale for unsaturated porous and fractured geologic media.

For these reasons, calculations of pre-waste-emplacement groundwater travel time along the fastest path of likely radionuclide travel through the unsaturated zone may have large associated uncertainties, and may be of questionable value in estimating the capability of the geologic setting tQ isolate HLW from the accessible environment.

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The new definition of the term 11groundwater 11 which the Commission is proposing would have the effect of expanding the scope of the performance objectives set forth in§ 60.113 to disposal in either the saturated or unsaturated zone.

Similarly, the proposed amendment to the Sittng Criteria:- (§ -60.-122(b).(7)) would have the effect-of making pre-waste- <;;:

emplacement groundwater travel time along the fastest path of likely radionuclide travel from the disturbed zone to the accessible environment which substantially exceeds 1,000 years a favorable condition for HLW disposal within either the saturated or unsaturated zone.

The Commission's current thinking on this issue is that if DOE can demonstrate with reasonable assurance that travel time for groundwater movement through the unsaturated zone can be quantified, then DOE should be allowed to include suer travel time when demonstrating compliance with

§ 60.113(a)(2).

However, such calculations of groundwater travel times through the unsaturated zone could involve considerable uncertainty.

Further, long groundwater travel time possibly may be inconsistent with the proposed amendment which identifies a host rock that provides for free drainage as a favorable hydrogeologic condition for disposal of HLW within the unsaturated zone.

I t may be more appropriate for the Commission to specify another parameter upon *which performance may be evaluated for a geologic setting in the unsaturated zone, or to utilize the approach*

set forth in§ 60.113(b) which provides the Commission with the flexibility to specify variations in performance objectives on a case-by-case basis, as long as the overal l system performance objective is satisfied.

Therefore, to solicit input in these matters the Commission is particularly seeking public comment on the following questions:

1.

How can groundwater travel time in the unsaturated zone be determined with reasonable assurance? Should the groundwater travel time performance objective be limited to groundwater movement within the saturated zone?

2.

Does groundwater travel time represent an appropriate measure of performance for a site within the unsaturated zone, or would an alternative performance objective for the geologic setting, (.e.g.,

maximum likely volumetric flow rate of groundwater through th~ geologic repos i tory) be more appropriate?

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ENVIRONMENTAL IMPACT:

NEGATIVE DECLARATION Pursuant to Section 12l(c) of the Nuclear Waste Policy Act of 1982, the promulgation of these criteria shall not require the preparation of ao~~nvir9~menta3 ~impac~statement under Section 102(2)(C) of the National Environmenta~ Policy Act of 1969 or any environmental review under subparagraph (E) or (F) of Section 102(2) of *such Act.

PAPERWORK REDUCTION REVIEW The proposed rule contains no new or amended recordkeeping, reporting or *application requirement, or any other type of information collection requirements subject to the Paperwork Reduction Act (Pub. L.96-511).

REGULATORY FLEXIBILITY ACT CERTIFICATION In accordance with the Regulatory Flexibility Act of 1980 (5 U.S.C.

605(b)), the Commission certifies. that this rule, if adopted, will not have a significant economic impact on a substantial number of small entities.

The only entity subject to regulation under this rule is the U.S. Department of Energy.

LIST OF SUBJECTS-IN 10 CFR PART 60 High-level waste, Nuclear power plants and reactors, Nuclear materials, Penalty, Reporting requirements, Waste treatment and disposal.

ISSUANCE For the reasons set out in the preamble and under the authority of the Atomic Energy Act of 1954, as amended, the Energy Reorganization Act of 1974, as amended, the Nuclear Waste Policy Act of 1982, and 5 U.S.C.

. 553, the Nuclear Regulatory Commission is proposing the following amend-ments to 10 CFR Part 60.

11

PART 60 - DISPOSAL OF HIGH-LEVEL RADIOACTIVE WASTES IN GEOLOGIC REPOSITORIES

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Authority:

Secs. 51, 53, 62, 63, 65, 81, 161; 182, 183, 68 Stat.

- 929, -930, -932,----933, 935, 948~ 953, 954, as amended ( 42-U. S. C. 2071, 2073, i=:

2092, 2093, 2095, 2111, 2201, 2232, 2233):

secs. 202, 206, 88 Stat.

1244, 1246, (42 U.S. C. 5842, 5846); secs. 10 and 14.

Pub. L.95-601, 92 Stat. 295i (42 U.S.C. 2021a and 5851); sec. 102, Pub. L.91-190, 83 Stat. 853 (42 U.S.C. 4332); sec. 121, Pub. L.97-425, 96 Stat. 2228 (42 u.s.c. 1014).

For the purposes of sec. 223, 68 Stat. 958, as amended (42 U.S.C.

2273).

§§ 60.71 to 60.75 are issued under sec 1610, 68 Stat. 950, as amended (42 U.S.C. 2201(0)).

1.

Section 60.2 is.amended by adding two new definitions in proper alphabetical sequence:

§ 60.2 Definitions.

11Groundwater 11 means al l water which occurs below the Earth's surface.

"Unsaturated zone 11 means the zone between the land surface and the deepest water table.

Generally, water in this zone is under less than atmospheric pressure, and some of the voids may contain air or other gases at atmospheric pressure.

Beneath flooded areas or in perched water bodies the water pressure locally may be greater than atmospheric.

2.

Section 60.122 is amended by revising paragraph (b)(2)(iii),

designating paragraph (b)(2)(iv) as (b)(7), and adding new paragraphs (b)(8), (c)(22), (23) and (24) to read as follows:

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§ 60.122 Siting criteria.

(b) ***

-. -.-( 21 *** (ii n-=-

Low-vertical-penneability and low hydraulic potential between the host rock and the surrounding hydr~geologic units.

(7) Pre-waste-emplacement groundwater travel time along the fastest path of likely radionuclide travel from the disturbed zone to the acces-sible environment that substantially exceeds 1,000 years.

(8)

For disposal in the unsaturated zone, hydrogeologic conditions that provide--

(i) low and nearly constant moisture flux in the host rock and in the overlying and underlying hydrogeologic units; (ii) A water table sufficiently below the underground facility such that fully saturated voids continuous with the water table do not encounter the underground facility; (iii) A laterally extensive low-permeability hydrogeolagic unit above the host rock that would inhibit the downward movement of water or divert downward moving water to a location beyond the limits of the underground facility; (iv) A host rock that provides for free drainage; or (v) A climatic regime in which the average annual historic precipitation is a small percentage of the average annual potential evapotranspiration.

( c) ***.

(22) Potential for the water table to rise sufficiently so as to cause saturation of an underground facility located in the unsaturated zone.

(23) Potential for existing or future perched water bodies that may have the effect of saturating portions of the u.nderground facility or providing a faster flow path for radionuclide movement from an underground facility ltlcated in the unsaturated zone to the accessible environment.

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(24} Potential for vapor transport of radionuclides from the under-ground facility located in the unsaturated zone to the accessible environment.

Dated--at Washfogton-;- D.C., this /3 rr -daj, -of ha-..eu~984.

For the Nuclear Regulatory Commission.

1ssion

• 14