ML20133G465
| ML20133G465 | |
| Person / Time | |
|---|---|
| Issue date: | 08/31/1985 |
| From: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20133G447 | List: |
| References | |
| NUDOCS 8510150474 | |
| Download: ML20133G465 (17) | |
Text
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Determination of Radionuclide Sorption for Assessment of High-Level Waste Isolation Technical Position August, 1985
.l f Y{
Geochemistry Section - Geotechnical Branch -
Division of Waste Management U.S. Nuclear Regulatory Commission 8510150474 851004 PDR MISC B510150474 PDR L_
TABLE OF CONTENTS Pagg
1.0 INTRODUCTION
.......................................... I 1.1 Purpose .......................................... I 1.2 Definition of Sorption ........................... 1 1.3 Use of Sorption..................................... 2 1.4 Regulatory Framework................................ 2
2.0 BACKGROUND
.......................................... 2 2.1 Experimental Approaches for Sorption Determination... 3 l
i 4 3.0 STATEMENT OF P0SITION....................................
4.0 ~ DISCUSSION .......................................... 4 l
r 1
4.1 Matrix Development.................................. 5 4.2 Characterization of Reactants and Products.......... 6
- 4.,3 .I.sotherm Development for Closed-System Experimentation 8
4.4 Determination of Sorption Parameters by Multiple Experimental Approaches.............................. 9 l 4.5 Documentation of Uncertainties....................... 12 i
5.0 REFERENCES
.......................................... 13 i
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DETERMINATION OF RADIONUCLIDE SORPTION FOR ASSESSMENT OF HIGH-LEVEL WASTE ISOLATION
, NRC TECHNICAL POSITION 3
1.0 INTRODUCTION
1.1 Purpose
! This document presents a general approach for estimating radionuclide sorption
- on solids anticipated in a nuclear repository in suppart of high-level waste site characterization. It is not intended to prescribe specific methods for radionuclide sorption determinations. Instead, the information is provided to l
the Department of Energy (00E) to be used as guidance for preparing detailed plans for radionuclide sorption determinations and submitting appropriate documentation early in the site characterization process.
1.2 Definitions of Radionuclide Sorption.and Related Experimental Parameters-
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Sorption-kneormorephysicochemicalprocesses excluding precipitation of stoichiometric (fixed composition) solid phases, in which the
- radionuclide is removed from a liquid phase by interaction with a solid phase or phases.
i Sorption or Desorption Ratio, R, - the amount of radionuclide on the solid versus the amount in the liquid Distribution Coefficient, K d- the sorption ratio determined under equilibrium conditions l
Retardation Factor,f R - the ratio of the velocity of the liquid to that of
, the radionuclide 7
Sorption Cagacity g the maximum amount of radionuclide sorbed on a unit mass of solid)p[ (4 , j () {
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1.' 3 Use of Sorption 1
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! f(flowinf through permeahla-soli %, sorption processes act to retard the migration of the solute relative to the It fjef. TM t
} moWi cy vi730tDMacMdes-dependsrin-partr on-whother-they-are-strongly - he seebed. RadionucliesorptionexperimentE*4etrcanbeusedtoestimatethi: -
First, retardation andy quantify two aspects of repository performance.
f , radionuclides which sorption experiment's can be used to help .scrpen for "ke j
m twg Adv are defined here as those radionuclides that are both hig ly toxic and mobile, v3 j 3
. -:nd wl.ich va * :1gn fi:::t ;=ntit4es in_tha nuclear _.wasteaepesitery. ,
i (, ke d Second,sorpfionstudiescanAWo'be used to determine the relative ability f g the $ nw repositorh -engineered syste =d the ': .te?9 ~M_t* *ha g i ace um; -- ' ) to isolate radionuclides. Para ers such as sorption 10 (f /4 dr de~so'rption ratios, sor ion capaci R an retardation
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tors derived from th D tudies can be used to q tify the ability of the subsur repository -
l retard'radionuclide migration.
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1.4 Regulatory Framework
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Three Federal agencies have major roles in the national program for disposal of high-level radioactive wastes. The EPA has developed a generally applicable
! environmental standard which serves as the overall performance objective for releases from high-level waste disposal. The NRC will develop and issue 1
1
! regulations which cover all aspects of high-level waste disposal, and which 111ty4r will implement the EPA stag T G OE has the lead
- formulating natttMal policy for disposal of HLW, and has' determined that j nationalpolicyshouldfocusondisposalofHLWinminedgedio(icrepositories.
Fur Mr7-00C is n5psstMe-for constructTirg and operating a waste dispoTat facility in accordance with NRC regulations. The NRC will consider DOE license l
applications for HLW disposal to determine whether the proposals will conform l
to the regulation. J /-
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2.0 BACKGROUND
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- h p A geologic repository controls the rate of radionuclide release to the
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accessible environment by means of two pap 5Vsubsystems: (1) the geologic l
setting; and (2) the engineered syst35,Aihe3eologic_ setting (site)-1A
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j selected ^for~ its geologic, hydrologic and gehh'emiial' attributes-that-enhaase
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t eadinnucijdeisolation.)eIt is-the_respo'n[s[bdit - the-00E-to-decide and ' ,
)! how much-credit eet NRC and EPA riteria or\
/ wil ylT k g tion t i for sorp?Q Z J 91 c eo & s .dsn ' hdmW
! radionuclide release. -
b a e t_be _ con s i de red 1 beother-features-of$tee ,, .
S arption%neecr_no i repositorv ar* adeguate_to meet-the-criteria. A Ifron the other hand,-sorption ( /
is to be considered, input of radionuclide sorption parameters to perform nce _
assessment models is necessary R'adionuclide sorption parameters applicabl? to i
.i;he nuclear (waste-repositihsystem are d ficult to determine precisely k f f 7
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j because futu're geoclamical-condttf~o^ns cannot be known with coinpletb nty. )
t 6weve'rTby determining sorption parameters experimentally using site spect?~i /
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phases and conditions, and applyin safety fa'ct f necessary, it sh'ould be j ss4ble t;o_make reasonable estJma es _of sorption in the subsurface repositoryj4 h $d b) fb kb l [cc kh ~~. Approach )5 2.1 ExperDen fogorptionDetermination l
p & ' 4(MbanYs J.bdivided into two types:W f gene al, sorptioY ex 1 closed or b>
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static systems; and 2) open or dynamic systems (NEA,1983; McKinley and Hadermann,1984). Both approaches have been used to describe repository performance. For characterizing sorption phenomena, c sed-syst pergnt ,
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such as batch sorption tests, involve contacting efdionuclide-fr p r deficient) solids with a radionuclide-bearing solution for the duration of the ' e experiment followed by analytical determination of the sorption ratio, Rs. bv Batch desorption experiments, on the other hand, involve contacting ,.
) radionuclide-free (or deficient) liquid with radionuclide-bearing solids, I I followed by measurement of the quantity of radionuclide leached. Open-system ji experiments, such as flow-through column tests, involve the introduction of y j fluid at one end of a reaction vessel containing solid and the removal of the m fluid at the other end. The solid material sorbs solute and, as a result, 7R I'
r s
retards the migration of the solute relative to that of the liquid, expressed t as a retardation factor, R .
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\ There are advantages to both experimental approaches. For example, the Nb l [( advantages of the closed-system experiments are that they are relatively simple k(
to carry outfa d the sidencetimeofthesolutionincontactwiththesoQ I / in;be greater than in ,a open-system experiment. , The longer residence times. h[
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re closely simulate thos.e_.i ta nuclear waspe re g .f'On the other
, S Q vantagys f the open-system experim nts are that they may better jy7 g- g 3
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model radionuclide migration in flowing systems by revealing the presence of multiple speciation, mass action competition, colloids or particulates that the closed-system experiment (batch test)rmight miss. (Kelmers,1984).
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- 0 L V% V 3.0 STATEMENT OF POSITION h6 -
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It is the position of the NRC that sorption parameters used in performance f@
f assessment calculations should be derived experimentally , The00Esites shou dF y j g hC6A
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DevelopatentativematrixofexperimentsthatinvolvesradionuclidesandU starting materials based on the anticipated range of proportions and $14!O compositions of phases under the various physicochemical conditions expected in the subsurface repository;
- 2) Characterize solid and liquid reactants and products; o
- 3) For closed-system experiments, determine sorption isotherms by varying radionuclide concentrations up to an apparent concentration limit;
- 4) Determine the applicability of sorption parameters to repository performance by using various experimental approaches including both open and closed laboratory systems, in-situ field tests, and natural analogues; and
- 5) Document the magnitudes of experimental and conceptual uncertainties from all anticipated sources.
4.0 DISCUSSION Details on the individual points from the Statement of Position, along with a '
discussion on why the NRC staff thinks these points are important, are given below. It is the responsib ty,of the DOE.to demonstrate that when these i s ome - s t f e ty - f a q p a rame te r s--(t :urt . if nar== u cy bare used in performance assessment calculations, the adionuclide migration is not underestimated.
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[yfJ" f Failure to consider and eveWate the points in the Statement of Position could
/ . w - :. w make it difficult for the DOE to, provide-reasonable-assurance that the sorption parameters are appropriate for characterizing the site.
4.1 Mctrix Development A matrix of experiments should be developed as a planning tool for characterizing the sorption properties of a subsurfAcd repository. Variables such as solid composition and texture, liquid composition, proportion of phases, temperature, pressure, particle size, flow rate and regime (porous and fractured media), time, and ionizing radiation should be considered in the matrix.
Initially, radionuclide studies can be prioritized by comparing EPA and NRC criteria to radionuclide inventories in the repository. .Some radionuclides may occur tn low enough quantities that, if they meeti NRC release rate requirements, they will not contribute significantly to exceeding the EPA standards. These may be assigned a lower priority than those radionuclides whose cumulative releases over 10,000 years are likely to exceed the EPA standards in the absence of sorption effects.
It is recommended that the matrix include scoping experiments, performed early in the . experimental program, which involve relatively simple systems (few components). These simple system experiments might be useful in determining the effects of various physicochemical conditions on sorption. Following the scoping experiments, the matrix development should reflect combinations of the above parameters that simulate' physicochemical conditions and phase assemblages likely to release radionuclides to the accessible environment. Consequently, the size of the matrix would be greatly reduced by first considering the dependence or interrelation of phases and conditions upon each other and deleting incompatible combinations.
The NRC staff considers it important that the 00E develop a matrix for planning sorption experiments. The DOE can then effectively demonstrate its rationale for choosing some combinations of parameters for study and eliminating other combinations as inappropriate. Without a matrix, some crucial experiments that 5
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)characterizeradionuclidemigrationmaybeoverlooked. Asaresult,kheDOE ,. . . . .
might not be able to demonstrate -with_reasonaMe-assurance-that the derived ( / . r.- b o
M 1sorptionparametersareappropriate. - "4 "
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' 4.2 Characterization of Reactants and Products, Wi 'M t
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). . gg In choosing appropriate solid reactants for sorption studies, emphasis should f b) j ;
[5 be placed on the identification and characterization of solids including waste'tu f "'
dW} d form, canister, backfill, seals, packing, and host rock primary and secondary */F"*O will take as
%/,phasesoccurringalongpathstheradionuclide-bearing, _.
i1 ) ft fl6ws away from the waste. These ape ~the solids most likely to react with p'-
e groundwater and thereby affect radionuclide concentrations and release rates.C j h'
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h Characterization of the solids should include' chemical, mineralogical, .h.- O h i
textural, and particle size determinations.'c)The applicability. of-crushed / M ' O#
$e solids in sorption experiments to repository conditions'should be addressed. .
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It is'possible that the surfaces of crushed material are significantly
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4 different from the surfaces of intact material, both porous and fractured.
g gindingmayexposethesurfacesofsolidphasesdifferentfromthosewhich would contact in a repository and/or may change the reactivity of (groundwa -
the-same mineral surfaces with dissolved radionuclides.
Similarly, the range of groundwater compositions expected in a repository system should be considered in selecting liquid reactants. Generally, in the rock-dominated w pvironments of a high-level Wa waste rotgpository, groundwater compositionsja be af fected by reactions with,w14ds 4t-vartuus tempi m uressp apd-pretsures. Consideration of the rang *e M water compositions used in #~
experimentation should be based on the range of compositions of analyzed groundwaters at ambient conditions, the range of compositions calculated from solid assemblages assumed to have equilibrated with the groundwater, and the range of. groundwater compositions experimentally determined at elevated temperatures and pressures.
l The applicability of synthetic starting materials to the conceptual model employed in developing the matrix should be addressed. Failure to do so might result in experiments that do not adequately simulate repository conditions.
For example, the preparation of radionuclide-bearing groundwater commonly 6
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j involves the addition of a small amount of acidified tracer to a synthetic
- solutionsimulatingthenatural'groundwaiei.STheresultingsolutionmay neither be representative of repository conditions ncr be stable. Kelmers et al., (1985) found that in a sorption experiment in which a synthetic ;
groundwater was tagged with an acidified uranium solution, more uranium was subtracted from the control (liquid only) than from the test (liquid + solid) resulting in a negative sorption ratio. This indicates that the synthetic l
groundwater was unstable and inappropriate for modeling repository conditions.
1 In addition to characterizing the reactants, it is also important to
! characterize the experimental products. Following the experiment, analysis of the liquid products should include the determination of major, minor, and trace element concentrations, along with pH and redox conditions.
! The extent of sorption of some dissolved radionuclides on engineered barri,er I materials and host rock can be strongly dependent on the redox potential (Eh) and acidity (pH) of the groundwater. For example, Benjamin and Leckie (1981) ;
show that the sorption of Cd, Cu, Zn,'and Pb on amorphous tron oxyhydroxide is ;
j strongly dependent on pH. The percentage of cation sorbed varies from approximately zero to one hundred with a change in pH of two units. Likewise, ,
4 Kelmers et al., (1984) have shown that sorption ratios for neptunium and !
j technetium are dependent on the redox condition of the system.
1
! The characterization of solid products from sorption experiments is important ,
! because, for example, under the same physicochemical conditions, different I s
solid phases can have drastically different sorptive capacities for the same r i
- radionuclide. Characterization of the solids is important in determining which l reactions took place and how these reactions depend on experimental technique.
! In addition to determination of the composition of individual solid phases, characterization should include surface area and/or particle size measurements.
[
l Because sorption is predominantly a surface phenomenon, the surface area of the
- solid may strongly affect the experimentally determined sorption parameters.
.For example, neptunium sorption ratios increased two orders of magnitude as l
particle diameter decreased from 200 to 2 um(Kelmers et al.,1984).
i 4.3 Isotherm Development for Closed-System Experimentation 7 .
l _-
t Probable release scenarios call for radionuclide concentration gradients in the repository system. Under equilibrium conditions, the concentrations of radionuclides in the repository can range from zero to an apparent concentration limit. Under equilibrium conditions, the apparent concentration limit is the greatest radionuclide concentration the liquid can maintain when the temperature, pressure, and moles of all other components in the liquid, n),
are held constant. The apparent concentration limit is controlled by the solubility of some stoichiometric radionuclide-bearing solid phase. Figure 1, a generic sorption isotherm, illustrates the relationship between concentration on the solid versus concentration in the liquid when all other parameters are held constant. Analysis of the liquid product can assure the constancy of the other parameters. Although this figure shows a linear sorption region, many sorbed species, including radionuclides, show nonlinear relationships between the quantity sorbed and the solution concentration. Thus, sorption ratios are dependent on solute concentration (Serne and Relyea, 1982).
Because radionuclide concentrations are expected to vary in the repository and sorption parameters are concentration. dependent, the NJtC-staf f-considers-4t A "G'R
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-reasonaMe'tiREstgn experiments t6 determine the effect of concentration on sorption ratios. Sorption isotherms should be determined up to an apparent concentration limit. Experimentally, it should be possible to determine an apparent concentration limit of a radionuclide in liquid in contact with solid.
For example, at the same temperature, pressure, and nj in the liquid, two sorption experiments with different concentrations of the same radionuclide in the liquid starting material should yield the same radionuclide concentration in the liquid products at the apparent concentration limit.
4.4 Determination of Sorption Parameters by Multiple Experimental Approaches l? Q e- (-) or >Le & n v nc, 6(f a sorption experiment could'be designed that simulated all anticipated h torymconditions,-it would not be necessary to use'multipl,e.fxperimentals
{ q approaches-to letermine sorption parameters. HoweverrsimTlation of all, anticipatedrepositoryconditionsJ,sorptio'riexperimentationwouldbe
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difficult and/or impractical., -The f'a'ct-that some parameters or conditions x.
cannot be bounded requires the extrapolation of'these conditions to those expected in the repository. This extrapolation introduc'es uncertainty into th *
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\ modeling of sorption parameters. Therefore, multiple approaches can lend
, support to, and reduce the uncertainties of, experimental results from studies
( in which some parameters are not site specific. Some experimental parameters can be varied over a large enough range as to bound the conditions anticipated in the repository. These parameters include surface area / volume ratio, (SA/V),
y'yk temperature, pressure, composition, and flow rate. Other parameters that often
/ are not duplicated in the laboratory are scale, r sidence time, water / rock s ratio, and flow characteristics, which can include saturated versus un aturated fractured flow. - b'~~~C'b ) I ~
flowandporousmediavlersy
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W J% @lk Experiments he designed so that measureable effects of physicochemical
/ 4 reactions can be monitored in a reasonable time. At the relatively low temperatures anticipated in the repository, chemical reactions involving geologic materials can be extremely slow. In order to accelerate these reactions so that changes are measureable in experimental time, conditions other than those anticipated in the nuclear w'aste repository are sometimes, imposed on the experimental system. For example, experiments have employed crushed solid material, high concentrations of solutes, agitation, catalysts bC"' % 7N
- rapid g aflow (gkrates,andelevatedtemperatu$rs.#u
% c ceMm nihyy cau Mc In addition to accelerating reaction rates, laboratory experiments are designed ;
so that the amount of material can be handled reasonably. By scaling down
'() systems of interest (repository size) to laboratory size, certain physical
~
h conditions must be altered. For example, the water / rock ratio in most j repository systems is significantly less than one. Hgwever, in order to obtain i p '
enough wate /for analysis in laboratory experiments.'the W/R ratio is ordinarily increased significantly. This technique makes the bulk chemistry of j j~ the experimental system different from that in the repository. The proportions y 'z , l of phases in experiments has been shown to affect radionuclide sorption M V paratneters (Meyer,1983; Raf ferty et al . ,1981; Meier et al . ,1982). Thus, the j
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effect of this technique on sorption parameters should be considered. One can
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I y arguethatinafracturedmedia,withlittleporosity,mostoftherockwill I
yl , not be in contact with the groundwater. Consequently, water / rock ratios used I
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N in experimentation should be higher than those that take into account all the T
rock in a repository system. If this argument is used, however, it follows
[ that the solid reactants should be predominantly fracture material and not bulk l
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rock. Sorption experiments involving crushed bulk roc
, applicabilitytosirptionphenomena'infracturedjedia. mig [hthavelittle
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exper$ mentally determined sorption m: 2:->-to 1 witory system, the s4tegoMNse multiple experimental approaches.
l [This approach was a recommendation of the WRIT Program (Serne and Relyea, Q 1982).] Using this approach, sorption parameters s can be analyzed and compared.
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j c hear _. example, the ~ sorption ratis R,~,~~ obt'ain'ed from batch experiments has of ten l k /beenusedtocalculatearetardationfactokR. The 7 relationship between R, j i
! k 'Y k and R is taken to be ,
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4, @R f 1 + pR,(1 - e,)/#,
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l d( M y Nere'pis'theb'ulkdensiyoftherock,and$ Is the effective porosity. . f!
fhisrelationshipisbased n ion; exchange theory as applied tes orous media j; 1 flow. However, due to the va ety of processes that contribute t sorption,
,p te i Oh the calculated R value may not qual the measured R value determin from a
' low-through col mn experiment.
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Comparison of the sorption and desorptio'ngarameters obtained from \
closed-system and open-system experiments is recommended. Generally, the j sorption' parameters derived from closed-system experiments are equal to or greater than those derived from open-system tests using the same solid material I (NEA Workshop, 1983). As a result, closed-system tests may overestimate the
! effectiveness of a repository system to isolate radionuclides (Relyea, et al.,
1980). The difference in sorption ratios may be due to particle abrasion in 4 l stirred closed-system experiments or the relatively short residence times in
! open-system experiments (NEA Sorption Werkshop, 1983). Other factors that can I
cause a discrepancy between the sorption parameters from open and closed
! systems are the presence in the liquid of multiple radionuclide species, colloids, and particulates. Changes in physicochemical parameters such as 4 l
! temperature, fluid velocity, radionuclide concentration, and fluid composition 1
l may shed some light on the causes of the discrepancy between the two types of I
systems.
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Extrapolation of sorption parameters from laboratory experiments to a u d v~sc4 hja*
large-scale, long-term repository system can be highly uncertain. The flow characteristics of the groundwater can have a drastic effect on the applicability of laboratory-derived sorption parameter's to repository performance. Most experiments use crushed material as a solid medium because
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it is easy to handle and characterize, and accelerates solute-solid reactions.
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- media may,-tN .d.q;;;; M* _
._ t g a tu ... :[$NI t$tured-recl6 6k it al., (1984) and_
Nuttall and Ray, (1981) have calculated that rates of radionuclide migration via fracture flow can be two orders of magnitude greater than that via porous media flow. Thus, for performance assessment calculations, consideration of flow re ime can be of the utmost importance.
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g4 *a t If groundwater flux in a repository is predominantly via fracture flow, sorption tests in the laboratory may not adequately simulate repository conditions. One method of further reducing the uncertainty caused by the inadequate simulation of various flow characteristics could be to perform in
- 6 situ tests on site-soecific solid material (Serne and Relyea,1982; Abelin et
~ar~, 1984; Neretnieks et"~al., 1982). The scale of these tests can be larger than that of the experimental tests but smaller than that of the repository.
Furthermore, the in situ solid materials would probably not have suffered the effects of handling (grinding, sieving, washing) required in laboratory tests.
Time constraints. hawaw- ,,, =T8 still apply in these experiment ( Comparison between the laboratory and field results can illustrate the usefulness of th7 1 different approaches. However, the physicochemical conditions must be YW C carefully controlled in the in situ tests to ensure a parallelism in the de approaches. Therefore, DOE should re :ik performi.n,-in situ tests der c ;eri:26 with let,vretery in ig 4- "- to reduce the uncertainties fn # qNw appli m tie- te -- : reali st4crapasttery-systemst l Y M,.
r m aw., ya,., g em m . (Jpc,% h ,w ~d>z .
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Although field tests can expand spatial scale over that which is normally handled in a laboratory, the time scale is. still several orders of magnitude 5"f-' ural analo '
s mmom : f, lessthanthatofarepositor$ypossibly-cen I, s* +L .
kalu-l6;(fa,~
ondhd'W+gue .
W = = d studies ^w . ex J.t shed-seme-14 migrati n'of:
radionuclides inh /f=MaThave 7existad_ foe._lang_paciads of + 4me. The natural analogue should be demonstrably equivalent to some particular process 11
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j g esent in the repository and have well-defined boundary conditions. C;.-:w, ,
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4 fxamplesofsystemsusedasnaturalanaloguesareorebodiessuchasOklo (Brookins,1978) and the uranium deposits in the Northern Territories of Australia (Airey, 1983). Igneous intrusives have also stud ed for they ;
a simulate anticipated thermal histories and alteration ee{'rnif( tte d l 4- b ( li
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% c::: cf hcertainty stem.$from fai ure to du licate anticipated repository b W (m
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conditions and incorrect experi enta resu ts.
to The failure to duplicate 0d& Pd:
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! repository conditions can be caused by an incorrect understanding of the
! conditions, an inability to duplicate the conditions or an 4-d;;m-t-improper '
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experimental design. 'Incorgect~expeftse'niaGeiults ca_ri re[ ult boIid_ectD..- l f _ ,_ __ - , . - - -~ . . . _ , . . _ _ , , _ _ _ ,
(dataormisinterpretation'softhedata.,Theuncertaintiesofsorptionstudies .
l l can be minimized by udngliiltiplItechniques to determine repository .,
i conditions, analyses/ to bound adverse mpacts, and multiple experimental 1
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methods, b Pb 1 i
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r,phe impact of the -
The NRC staff recommends that th 00E gons; erro uncertainty o th Nui a thI ' nNNp ikoYpe g-oIance ymy) j.
l Subsequenti the should focus on the uncertainties which have the most I impact' sitory performance. -
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5.0 REFERENCES
vYf % gm or ff4f f * *- 4.c ,
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1
- Abelin, H., J. Gidlund, L. Moreno, and I. Neretnieks, " Migration in a Single Fracture in Granitic Rock" in Scientific Basis for Nuclear Waste Management, VII, Elsevier Science Publishing Co., p. 239-246, 1984.
l Airey, P. L., Radionuclide Migration Around Uranium Ore Bodies - Analogue of
- Radioactive Waste Repositories, NUREG/CR 3941 AAEC/C40, vol. 1, 1984.
1 Benjamin, M. M. and J. O. Leckie, Conceptual Model for Metal-Ligand-Surface .
l Interactions During Adsorption, Environmental Science and Technology, vol.
.i j 15, p. 1050, 1981.
Benjamin, M. M. and J. O. Leckie, Multiple-Site Adsorption of Cd, Cu, Zn, and Pb on Amorphous Iron Oxyhydroxide, Journal of Colloid and Interface Science, vol. 79, no. 1, p. 209-221, 1981a.
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13
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