• SEALIN

. ~·.SEALa

SEALING STRATEGIES

• Minimize Water Movement Around the WasteContainer

• Decrease Hydraulic Conductivity in the Vault

• Seal Hydraulically Critical points in the Vault

• Enhance Sorption of Radionuclides and ChemicallyCondition the Groundwater

Container Emplacement Alternatives

In-Floor Emplacement

In-Room Emplacement

In-Wall Emplacement Long-Hole Emplacement

SEALING SYSTEM REQUIREMENTS

Seal Engineering Objective Performance Approaches UsedRequirement in EIS Vault Model

Buffer Clay Dry Density >1.24 Mg·m-3 No convection No convection;always In transport

Hyd. Conductivity, (k) <10-11 m·s-1 pathBackfill k < 10-10 m·s-1 No/minimal In transport path,

convection for rooms below FZBulkheads,Shaft Seals

- bentonite Density >2 Mg·m-3. No convection Evaluated In

k < 10-11 m·s-1 detailed model, not,in vault or

- concrete Provide physical support to Minimal geosphere modelbackfill alteration of

buffer/backfillEDZ

- grouts Use where k > 10-7 m·s-1; EDZ should Evaluated In

reduction of k by 10 to 100 not be a flow detailed model, notpath; e.g., in vault or

- rock Optimize excavation to prevent keyed-In seals geosphere modelconnected oermeabllitv

VAULT SEALING MATERIALS

Q!!v-Based Materials

• Low Hydraulic Conductivity

• Swelling and Extrusion

• Sorption

• Neutral pH

• Emplacement Options'

• In-situ Compaction

• Precompacted Blocks

• ,--Aggregate Addition

• Availability

Cement-Based Materials

• Low Hydraulic Conductivity

• High Strength

• Engineering Material - Many Options

- 223 -

IT-- -!f~.·· ,"r:4-!*'"""

--

,----------------------

-'

FIGURE 4-15: Large Precompacted Blocks of the Reference Buffer MaterialBeing Sawn in a Band Saw (top) and Being Augered (bottom)

BUFFER AND BACKFILL PERFORMANCE

• Smectite ~ Illite

• Swelling

• Gas Generation and Transport

• Cements

• Radiation

• Microbial Activity

• Colloids

Mineralogical composition andrelated chemistry ofAvonlea bentonite

%

Montmorillonite 79Illite 10Quartz 5Feldspar 3Gypsum 2Carbonate 1Organic Matter 0.3

SSA= 630 x 103m21kg; CEC= 82 cmolJkg; exchangeablecations in cmolJkg: Na+= 47, Ca2+= 40, Mg2+= 7, K+= 0.7.

,'.-.•.

"<t"<t

100 104 ""0....0........ xx

f/)

.~ (\I'~ E E<tl ~ ~

Q.\~ f/)

~ 10 103 0

~>: -" ....

';'- (f)- >Q) -.... .....:J ·.,0 0lIJ :JlIJ

~. ,:.-- ;;.".,:, '0 .,.:Q) .c: - J....

102 0 Q)a. 1 . 0 00

Ol 0c: c::J .Q

Q) <tl f/).... :J:5: legend: '0 -C/) >. -0-1 25% clay

:x: 00 10h. 50[J. 750100

0-4 0-75 1045

Effect ive clay dry density (MgAn3)

( ,

.'..., .

.,

20

fLegend:, , ,

• 100 % I;>entonite---.. 0 75% bentonite 0c<:

50% bentonite IPo< ••~ a 40% bentonite •••'-'

jOJ A 25%· bentonite.....= 10.." I---'"OJ.....~ 11/l>Dl:l ./.....--OJ~ . .8

v.l o .. ""'"---,../"' " .

~ Canadian bentonite0 A • I

.. 0.9 1.4 1.9

Effective clay dry density (Mg/m 3)

·80

---..c<: MX·80 Wyoming bentonitePo<~'-'

.' .OJ.....=."." 40OJ.....~ ,l>Dl:l.---'"~

v.l

01.1 1.3 1.5 1.7 1.9

Effective clay dry density (Mg/m3)

Influence ofPore FluidSalinity on Swelling

Pressure

100

::i§. 10

0.01

I

Ie DOW~t :II

& -- :~I 1

-DOW".,.., ._-~--------:

II

••• BrIne"""'nt IIII

I I

--------~---------~-: xI XI DOW Perrne-.t:. .,. o.OO33e~

J( : ,. 'l x ft.G.778

I If xII :--------,----- ---~--------,---------x X I I

: • : Brtne PMneent: I .,.o.~-

: .... G.882 .I II I

o 0.5 1 1.5 2

EFFECTIVE CLAY DRY DENSITY (Mg/ml)

. :

Influence of GroundwaterSalinity on Hydraulic

Conductivity-

1~ ~-..L.,---~-~--~-~II

2.521.50.5 1

Deionized Wlltery =1&12lr'-45

p,z =0.723

1&15 -1---+--+-------t---l-------j

o

1&14

<> Deionized Wa~erg 1E-09 -!-.....:{--Plo--\--+---. Brine Solution

f3 1&10:;) Brine SolutionC 0' 1&11 -I----J.~~il¥<l~_____l.::::. y =7&12lr'-4

~ E "=0.819o - 1&12 -1---+--4­o:::i 1&13 -l-----++---+--:;)

~C>:I:

EFFECTIVE CLAY DRY DENSITY (Mglm3)

I ; II'"

11.5

, , • 0• .... ,12.0 • .... ..... 0., , 0,

,0- .. ,en ,- , 0 0E o ,0 0- 12.5~

,en e 0 •00

00 0- 0• -+- Slotted buffer plugs- log K =9.73 + 2.22 Pc 0

13.0 r =0.855

-0- Intact bentonite plugs 0-log K =8.87 + 2.85 Pcr =0.777

13.50.9 1.1 1.3 1.5

Effective clay dry density, Pc (Mg/m3)

.'

Gas BreakthroughResistance in Bentonite

lechanisms that may createathways through porous media

- Diffusion

- Capillarity

- Pathway Dilatancy

- Tensile Fracturing

)ossible gas pressure conditions

- gas pressure < pore water (PWP)

- gas pressure >PWP but < total soilpressure

- gas pressure> total soil pressure

II '

GAS FLOW MECHANISMS, -

DIFFUSIONDISSOLUTION OF GASES IN

THE WATER PHASE

2-PHASE FLOW

WATER IS PUSHED THROUGH

SOME PORES BY INVADING GAS

PORE DILATIONDEFORMATION OF SOIL FABRIC

CREATING LARGER PORES TO

ACCOMODATE GAS FLOW

FISSURING

CREATION OF NEW PORES

TO ACCOMODATE GAS FLOW

BUFFER GAS-BREAKTHROUGH

TEST RESULTS

10 ,-----,------,----.-----,------.

2.52.0

Gas-breakthrough

= 9.4 MPa

1.5

Gas inflow.... ~~. "

Gas

collection

1.00.5

Test BT3 (buffer)

8 Pdry ~ 1.67 Mg/m3

w = 11.2%

8=49%

2

oM::::===:::r:::::::===:::c:::===r:::==~-~0.0

Elapsed time (hours)

Diffusion in Buffer and Backfill

k < 10.10 mts - diffusion dominant

0, Total Intrinsic Diffusion Coefficient from

J = -0 (8 c t 8 x); 0 = Do't&

Da , Apparent Diffusion Coefficient from

r = Capacity Factor (& + p~)

o and r from - Laboratory Experiments

- Literature

- Expert Judgement

r

Diffusion Coefficients, Da, in Buffer

Diffusant Da (JJm2/s) Breakthrough

time· (years)

r 100 20

Cs+ 1 2000

Pu O.Of 200000

•Approximate time required for clco = 0.5 at the buffer/rock

interface; buffer thickness = 0.25 m

Diffusion Coefficients for Large Molecules

(MW 354 to 3000)

(Eriksen and Jacobsson, KBS TR-84-05)

Total intrinsic diffusion coefficients, OJ' for r inintact and defected bentonite plugs

110

.90

-~N 70E.;!,G):2 50't:JoC

C 30

10

o Intact plugs• slotted plugs

Io BCXplugs

~ -

--0

c-

Ol range specifIedIn vault model- for buffer andbackfill'

l-

•- 0

0 0

• 041 §

r- --

I I I I I

0.9 1.0 1.1 1.2 1.3 1.5

Effective clay dry density (Mglm3)

AK-58-01

Cement-based Materials

- For high-level waste disposal, generallyrestricted to grouting, shaft seal andconstruction applications (e.g., bulkheads,floors)

- Low pH concretes have been developed thatare more compatible with clay buffers andbackfills

page 8

CNFWMP Reference Grout

. Cement Type

Pozzolan

••

••

Canadian Type 50Reground to 600 m2/Kg (Blaine)

Silica Fume (10% of total dry mass)

Superplasticizer :

Mass ratio of :water ·to(cement+pozzolan)

Superplasticizer :content

Na-sulphonated naphthaleneformaldehyde condensate (liquid)

0.35 to 0.6

Varies' with desired viscosity.Typical values 0.75 to ~.5 percentdry mass ratio'superplasticizer to~ . -~. -- .. ---_ ........._,

UP SUPEFlIEURE "d' OSEN ~'OL,

1.61.20.4 0.8

w/cm

EFFECT OF WATE~/CEMENTITIOUS MATERIALRATIOS ON THE HYDRAUUC CONDUCTIVITY

OF GROUTS

10-16 L..-.L--'-_...J.......-'-'''--'---L-__''"'''--.a--l__a_ -o.-I

0.0

- 10-9...I

ID

S 10-10-~e 10-11

&-!t.)

bQ 10-12Z0r.,)

U 10-13::s~= 10-14,

~10-15

I./

/"/

//

I.-"

- BEFORETEST- - AFTER TEST

0.40-...IbO 0.35.!:Ill

II')

80.30-

~0.25:3

0> 0.20rz:IP::0

0.15Clt

~ 0.10

; 0.050u 0.00

1000 100 10 1 0.1 0.01 0.001

PORE DIAMETER ( p;m )

CHANGE IN PORE-SIZE DISTRIBUTION OF CEMENT-BASEDGROUT (W/CJl=O.4, TWO PARTICLE SIZES: t = 1.~~ mm AND

t = 0.30 mm) COMPACTED AT p = 1.6 Mg m .

Properties of fresh and hardened LHHPC and nonna! concrete.

Properties LHHPC Nonna!

(w/cmO.47) (w/cmO.56)

Fresh concrete

Slump(mm) 160 170

Air Content (%) 2.75 2.75

Maximum temperature rise during hydration ("C) 15 -45

Maximum temperature during hydration ("C) 37 -65

Hardened concrete

Density (kgim3) 2424 2168

Hydraulic conductivity (m1s) 10-13 to10-12 10-11 to 10-12

pH 9.65 -12.5

Total porosity - MIP technique (mlIg) 0.0580 nla

Drying shrinkage - 90 days in air (J.I£) 863 nla

Drying shrinkage - 7 days in water and 83 days in air (J.I£) 348 nla

Drying shrinkage - 21 days in water and 69 days in air (J.I£) 171 nla

Drying shrinkage - 90 days in water (J.I£) -50 nla

Compressive strength - 28 days, 23°C (MPa) 86 29

Young's modulus - 28 days, at 40% of ultimate stress (GPa) 36.26 21.89

Poisson's ratio - 28 days, at 40% of ultimate stress 0.114 0.087