Solid State Chemistry: A Contemporary Overview - American

19 Hydrothermal Stability of Simulated

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Radioactive Waste Glass GREGORY J. KOMARNENI,

McCARTHY , BARRY E. SCHEETZ, SRIDHAR DEANE K . S M I T H , and WILLIAM B . WHITE 1

Materials Research Laboratory, Pennsylvania State University, University Park, PA 16802 A study of stability

of a typical

simulated

high-level

glass in contact with pressurized

water at 300°C

system has shown that extensive

reaction

occurred

few weeks.

The water acted as a catalyst-solvent

fication

the

of

recrystallization in forming was

glass

hydrated

converted

into

masses of crystalline solved species.

dissolution,

transport,

phases. partially

and noncrystalline reaction

of minerals.

Much

glass were identified

only Cs was observed

plus

were

of the Na, Mo, in the product in

disfound

and

B

solutions.

hazardous,

in the solutions

glass

dispersed

material

of long-lived,

and reactant

Solid

products

a

devitri-

and as a

fragmented

and

within in

and hydroxylated

Of the elements or analogues nuclides,

in

The crystalline

to be analogues in the original

and

of some of its constituents,

waste

in a closed

radio-

substantial

amounts.

^ o l i d state c h e m i s t r y p l a y s a n i m p o r t a n t r o l e i n m o d e r n energy r e s e a r c h ^

(1).

M a n y energy r e s e a r c h p r o b l e m s are c h a r a c t e r i z e d b y e x c e e d i n g l y

c o m p l e x c h e m i c a l systems i n w h i c h s o l i d substances m u s t b e i n c o n t a c t w i t h l i q u i d s , gases, or plasmas u n d e r extreme c o n d i t i o n s of t e m p e r a t u r e a n d pressure. Some examples i n c l u d e M H D electrode d e g r a d a t i o n ,

first-

w a l l s t a b i l i t y i n f u s i o n reactors, c h e m i c a l reactions i n o i l shales d u r i n g r e t o r t i n g , reactions of g e o t h e r m a l w a t e r s w i t h r o c k s , p u m p s , a n d p l u m b i n g , p e r f o r m a n c e of refractories i n c o a l gasification reactors, a n d m a n y p r o b l e m s associated w i t h n u c l e a r reactors a n d n u c l e a r w a s t e d i s p o s a l . A u t h o r to w h o m c o r r e s p o n d e n c e s h o u l d b e sent. C u r r e n t address: of C h e m i s t r y , N o r t h D a k o t a State U n i v e r s i t y , F a r g o , N D 58105. 1

Department

0-8412-0472-l/80/33-186-349$10^5/l ©

1980

American Chemical

Society

Holt et al.; Solid State Chemistry: A Contemporary Overview Advances in Chemistry; American Chemical Society: Washington, DC, 1980.

350

SOLID S T A T E

CHEMISTRY: A

CONTEMPORARY OVERVIEW

S u c h c o m p l e x p r o b l e m s are m o r e often s t u d i e d b y m a n i p u l a t i o n a n d d e t a i l e d e x a m i n a t i o n of s o l i d - l i q u i d - g a s - f l u i d - p l a s m a reactions f o l l o w e d by

combined

simpler

i n d u c t i v e - d e d u c t i v e analyses b a s e d

systems

rather than

by

exact

o n experience

thermodynamic

and

with

kinetic

calculations. T h e record for chemical complexity m a y w e l l be h e l d b y problems i n v o l v i n g the s t a b i l i t y of r a d i o a c t i v e wastes.

W h e n these wastes

are

i n t r o d u c e d i n t o u n d e r g r o u n d d i s p o s a l sites ( r e p o s i t o r i e s ) , the p o t e n t i a l


w a s t e - r o c k - w a t e r interactions ( 2 )

i n v o l v e m o r e t h a n h a l f the elements

i n the p e r i o d i c t a b l e . W h a t f o l l o w s is a r e p o r t of o r i g i n a l r e s e a r c h into the reactions of a c o m p l e x , s i m u l a t e d ( n o n r a d i o a c t i v e )

nuclear waste

p r o d u c t w i t h w a t e r u n d e r one m o d e r a t e l y severe set of p r e s s u r e - t e m perature (2,3).

(F-T)

conditions postulated for a nuclear waste

T h e tools a n d m e t h o d o l o g y

repository

to b e d e s c r i b e d c o u l d just as w e l l

b e a p p l i e d to a n y of t h e p r o b l e m s i n v o l v i n g c h e m i c a l l y c o m p l e x systems t h a t w e r e c i t e d earlier. D i s p o s a l of h i g h - l e v e l r a d i o a c t i v e w a s t e n u c l e a r p o w e r p l a n t s r e q u i r e s three steps: suitable waste form; (2)

(radwaste) (1)

produced

discussed

a

t h e p a c k a g i n g of the waste f o r m for h a n d l i n g ,

transport, a n d storage; a n d ( 3 ) the final d i s p o s a l of t h e w a s t e f o r m . research

by

t h e p r e p a r a t i o n of

i n this p a p e r

concerns

borosilicate

glasses

The as

a

r e p r o c e s s i n g w a s t e f o r m a n d g e o l o g i c a l repositories as t h e d i s p o s a l sites. C l e a r l y these are o n l y t w o of m a n y options, d e p e n d i n g o n p o l i c y decisions c o n c e r n i n g w h e t h e r spent reactor f u e l w i l l b e reprocessed

to

recover

u r a n i u m a n d p l u t o n i u m or d i s p o s e d of d i r e c t l y , w h e t h e r the spent f u e l or r e p r o c e s s i n g wastes w i l l b e stored for l o n g t i m e s (10 to 100 y e a r s ) to a l l o w for d e c a y of s h o r t - l i v e d isotopes, w h e t h e r there s h o u l d be a f e w n a t i o n a l respositories ( w h i c h r e q u i r e l o n g - d i s t a n c e t r a n s p o r t ) or m a n y s m a l l repositories nearer to the sources of the wastes, w h e t h e r to p e r f o r m separations a m o n g the c o m p l e x wastes a n d b u r n the l o n g - l i v e d a c t i n i d e f r a c t i o n i n reactors or dispose of i t i n space, a n d so o n . T h e b o r o s i l i c a t e glass w a s t e f o r m is one of the m o s t i n t e n s i v e l y d e v e l o p e d concepts.

I t is p r e s u p p o s e d that t h e reactor f u e l rods

have

b e e n reprocessed a n d t h a t a h i g h - l e v e l w a s t e stream c o n t a i n i n g most of the

fission

products

p l u s some c o r r o s i o n

products

and

reprocessing

c h e m i c a l s is the source m a t e r i a l for t h e w a s t e f o r m . T h e s e m a t e r i a l s are t r a n s p o r t e d i n solutions t h a t are e v a p o r a t e d , d r i e d , a n d fired to p r o d u c e a c a l c i n e t h a t is m i x e d w i t h a frit i n a n i n - c a n m e l t e r to p r o d u c e a l o w v i s c o s i t y borosilicate glass. T h e glass is m a d e , i n the f o r m of a massive i n g o t , d i r e c t l y i n the stainless steel c a n i s t e r , w h i c h t h e n serves as t h e h a n d l i n g u n i t a n d also as a n a d d i t i o n a l b a r r i e r i n final storage (4). r a t i o of h i g h - l e v e l w a s t e c a l c i n e to f r i t c a n b e c o n t r o l l e d .

The

T h e waste

canisters p r o d u c e d i n this m a n n e r are i n i t i a l l y t h e r m a l l y hot w i t h surface


19.

MCCARTHY

E T

AL.

Simulated

Radioactive

Waste

351

Glass

t e m p e r a t u r e s r a n g i n g u p to 4 0 0 ° C d e p e n d i n g o n t h e age of the wastes, the waste l o a d i n g (waste-to-frit r a t i o ) , a n d the t h e r m a l p r o p e r t i e s of the repository (3).

T h e surface t e m p e r a t u r e d r o p s to n e a r l y a m b i e n t o v e r a

p e r i o d of several h u n d r e d years

(the thermal period)

as s h o r t - l i v e d ,

heat-emitting, radionuclide decay ( 2 , 3 ) . Geological

repositories

are c o n c e i v e d

depths i n the r a n g e of 5 0 0 - 1 0 0 0 m .

as m i n e d - o u t

chambers

at

B e d d e d salt, basalt, g r a n i t e , a n d

shale have a l l b e e n c o n s i d e r e d as c a n d i d a t e r o c k types.

T h e repository


is u s u a l l y c o n c e i v e d as r e m a i n i n g o p e n for a n u m b e r of years to p e r m i t i n s e r t i o n of

a d d i t i o n a l canisters a n d to p e r m i t r e t r i e v i n g of

canisters

s h o u l d that be desirable. U l t i m a t e l y , h o w e v e r , the r e p o s i t o r y w o u l d be b a c k - f i l l e d a n d the wastes w o u l d b e i n p e r m a n e n t storage.

The

waste

f o r m itself, the canister, a n d the g e o l o g i c a l f o r m a t i o n act as b a r r i e r s to p r e v e n t m i g r a t i o n of dangerous r a d i o a c t i v e elements to t h e b i o s p h e r e . A m a j o r f a c t o r i n the t r a n s p o r t of r a d i o n u c l i d e s f r o m the r e p o s i t o r y to t h e b i o s p h e r e is w a t e r .

S o m e w a t e r occurs i n the host r o c k , a n d i t

c o u l d b e m o b i l i z e d b y the t h e r m a l heat of t h e canisters. r e p o s i t o r y rocks are selected

Although

w i t h l o w p e r m e a b i l i t y as a n i m p o r t a n t

c r i t e r i o n , t h e r e is a l w a y s some p e r c o l a t i o n o f g r o u n d w a t e r . the p o s s i b i l i t y , remote b u t r e a l , of a c c i d e n t a l

flooding

T h e r e is also

of the r e p o s i t o r y .

P r o v i d i n g that the canister r e m a i n s i n t a c t , c i r c u l a t i o n of w a t e r is of l i t t l e i m p o r t a n c e , b u t s h o u l d the c a n i s t e r b e b r e a c h e d , t h e r e a c t i o n of w a t e r w i t h the waste f o r m b e c o m e s a k e y element i n t h e analysis of r e p o s i t o r y behavior.

T h u s the present r e s e a r c h is a d d r e s s e d to t h e p r o b l e m of the

s t a b i l i t y of the b o r o s i l i c a t e glass w a s t e f o r m if i t comes i n contact w i t h w a t e r d u r i n g the t h e r m a l p e r i o d . G l a s s has b e e n a d v o c a t e d as a w a s t e f o r m because i t is c h e m i c a l l y inert, has a l o w l e a c h rate w i t h respect to r a d i o n u c l i d e s , a n d c a n f a b r i c a t e d i n r e m o t e l y o p e r a t e d f a c i l i t i e s (4).

be

E x p e r i m e n t s o n the s t a b i l i t y

a n d i n s o l u b i l i t y of glasses, h o w e v e r , h a v e m a i n l y b e e n r e s t r i c t e d to a t e m p e r a t u r e r e g i m e of 25° to 1 0 0 ° C .

L e a c h i n g e v a l u a t i o n , for e x a m p l e ,

is m a i n l y d o n e w i t h the P a i g e test ( 5 ) , w h i c h i n v o l v e s s o a k i n g t h e glass i n f r e q u e n t l y r e p l a c e d w a t e r at 2 5 ° C , or w i t h t h e Soxhlet test ( 5 ) , w h i c h bathes t h e glass i n c o n t i n u o u s l y d i s t i l l e d w a t e r at 1 0 0 ° C . W a t e r c o m i n g i n t o contact w i t h the glass d u r i n g t h e t h e r m a l p e r i o d w i l l b e

much

hotter t h a n w a t e r u s e d i n p r e v i o u s test c o n d i t i o n s , a n d i t w a s not c l e a r that the same o p t i m i s t i c conclusions c o n c e r n i n g s t a b i l i t y a n d i n s o l u b i l i t y w o u l d o b t a i n . T h e present r e s e a r c h was i n i t i a t e d to evaluate the s t a b i l i t y of a t y p i c a l r a d w a s t e glass u n d e r c o n d i t i o n s m o r e r e p r e s e n t a t i v e of t h e repository environment. T h e e x p e r i m e n t s d e s c r i b e d h e r e w e r e c a r r i e d out at 3 0 0 ° C a n d 300 b a r t o t a l pressure. T h e pressure corresponds r o u g h l y to the l o a d pressure i n a b a c k - f i l l e d r e p o s i t o r y at a d e p t h of 1000 m .

T h e t e m p e r a t u r e is i n


352

SOLID S T A T E

CHEMISTRY: A


t h e r a n g e e x p e c t e d f r o m y o u n g w a s t e ( 1 0 years out o f the r e a c t o r ) at a l e v e l of w a s t e l o a d i n g c o r r e s p o n d i n g to 3.2 k W p e r 6-in.-diameter b y 8-ft-high canister ( 3 ) . although

conditions

U n d e r these c o n d i t i o n s w a t e r exists as a l i q u i d , are

r a t h e r close to

the c r i t i c a l p o i n t , 215

bar

and 373°C. B o r r o w i n g a concept from experimental geochemistry, w e

define

reactions i n v o l v i n g hot a q u e o u s solutions c o n f i n e d u n d e r pressure

as

" h y d r o t h e r m a r reactions, a l t h o u g h the p r e s s u r e - t e m p e r a t u r e c o n d i t i o n s


are n o t s u p e r c r i t i c a l . I n a strict sense geochemists c o n c e r n e d w i t h t h e t r a n s p o r t of ores b y a q u e o u s fluids h a v e d i v i d e d t h e t e m p e r a t u r e scale i n t o " e p i t h e r m a l , " ' ' m e s o t h e r m a l , " a n d " h y d r o t h e r m a l , " to m e a n r o u g h l y hot water, superheated water, and supercritical water, respectively. T h i s terminology

has n o t y e t

penetrated

the n u c l e a r w a s t e

management

literature. T h e experiments w e r e c l o s e d systems.

G l a s s p l u s w a t e r w a s sealed

i n t o g o l d capsules, a n d these capsules w e r e p l a c e d i n pressure vessels for r e a c t i o n . T h i s m e t h o d a l l o w s a n easy e x a m i n a t i o n of the s o l i d phases, b e c a u s e the t o t a l mass of t h e system is c o n s e r v e d .

W a t e r w a s present

i n excess so t h a t a l l phase assemblages i n c l u d e d a l i q u i d phase. A n a l y s i s of t h e final solutions p e r m i t t e d a n e v a l u a t i o n of elements e x t r a c t e d b y a q u e o u s solutions b u t , b e c a u s e the v o l u m e of f l u i d w a s l i m i t e d , c a n n o t b e u s e d to d e t e r m i n e t r a n s p o r t rates. Experimental Simulated H i g h - L e v e l Waste Glass. T h e s i m u l a t e d h i g h - l e v e l w a s t e glass u s e d i n these experiments w a s P a c i f i c N o r t h w e s t L a b o r a t o r y ( P N L ) f o r m u l a t i o n 76-68 ( 5 ) . I t w a s s u p p l i e d b y P N L . T h e glass w a s f o r m u l a t e d a c c p r d i n g to the p r o j e c t e d r e p r o c e s s i n g flow sheet of t h e N u c l e a r F u e l Services p l a n t i n W e s t V a l l e y , N . Y . , a n d is sometimes r e f e r r e d to as " N F S g l a s s / T h e c o m p o s i t i o n of P N L - 7 6 - 6 8 glass (6) is g i v e n i n T a b l e I. O n e n o t a b l e c o m p o s i t i o n a l f e a t u r e is t h a t the glass c o n t a i n s 62 w t % ( N a O + F e 0 + S i 0 ) . T h e glass w a s c o l o r e d g r e e n b l a c k i n massive pieces, b u t i n t h i n f r a g m e n t s i t h a d a n a m b e r b r o w n c o l o r a t i o n . I t c o n t a i n e d n u m e r o u s vesicles ( b u b b l e s ) , some u p to several h u n d r e d m i c r o m e t e r s i n d i a m e t e r . A l s o i n c o r p o r a t e d i n t h e glass w e r e clusters of d u l l to m e t a l l i c b l a c k c r y s t a l l i t e s . Studies at P N L ( 7 ) h a v e s h o w n t h a t these c r y s t a l l i t e s consist b o t h of c r y s t a l l i n e phases t h a t n e v e r d i s s o l v e d i n the m o l t e n glass p l u s phases that c r y s t a l l i z e o n c o o l i n g . I n w o r k specific to P N L - 7 6 - 6 8 , i t w a s s h o w n t h a t the c r y s t a l l i n e phases w e r e R u 0 a n d a f e r r i t e s p i n e l i n the a s - p r e p a r e d glass, w i t h fluorite structure p h a s e , chiefly C e 0 , f o r m e d o n h e a t t r e a t m e n t ( 7 ) . A s m a l l a m o u n t of this fluorite phase, a l o n g w i t h R u 0 , f e r r i t e s p i n e l , a n d p e r h a p s P d m e t a l , w a s i d e n t i f i e d i n diffractograms of the s l o w - c o o l e d glass r e c e i v e d f r o m P N L . T h e t o t a l a m o u n t of c r y s t a l l i n e p r o d u c t s i n t h e glass w a s r e p o r t e d to b e less t h a n 10 w t % ( 7 ) . T h e glass w a s r e c e i v e d f r o m P N L as several l a r g e f r a g m e n t s . T h e t y p i c a l specimen used i n the present study was a single shard broken a

2

3

2

2

2

2



19.

MCCARTHY

E T

AL.

Simulated

Radioactive

Waste

353

Glass

f r o m one of these fragments a n d w e i g h i n g a b o u t 30 m g . F i g u r e 1 is a p h o t o g r a p h of one of these shards. T h e o p a q u e regions are the c r y s t a l l i n e i n c l u s i o n s . It s h o u l d be n o t e d t h a t the r a t i o of these c r y s t a l l i n e phases to glass w a s not constant f r o m s p e c i m e n to s p e c i m e n . B e c a u s e of the v a r i a b i l i t y of t h e a m o u n t s of these i n c l u s i o n s , i t is e s t i m a t e d t h a t the a c t u a l c o m p o s i t i o n of a n e l e m e n t i n a p a r t i c u l a r s p e c i m e n c o u l d v a r y b y as m u c h as 1 0 - 2 0 % of the n o m i n a l c o m p o s i t i o n g i v e n i n T a b l e I . S e v e r a l of t h e specimens u s e d i n t h e e a r l y stages of this s t u d y w e r e m a d e i n t o s p h e r o i d a l shapes b y a n a b r a s i o n t e c h n i q u e . Hydrothermal Treatment. T h e i n e r t c o n t a i n e r c h o s e n for these experiments w a s f a s h i o n e d f r o m 5 - m m - d i a m e t e r g o l d t u b i n g . A l e n g t h of t u b i n g was c u t a n d sealed at one e n d b y e l e c t r i c arc w e l d i n g or c o l d w e l d i n g w i t h a c r i m p i n g t o o l . A w e i g h e d glass s p e c i m e n w a s p l a c e d i n the c a p s u l e a l o n g . w i t h e i t h e r d e i o n i z e d w a t e r or a r t i f i c i a l H a n f o r d g r o u n d w a t e r ( n o m i n a l c o n c e n t r a t i o n i n m i c r o g r a m s p e r m i l l i l i t e r : 168 N a , 0.5 C a , 0.1 M g , 90 C I , 14 ( S 0 ) , 56 ( H C 0 ) , 87 ( C 0 ) , 4 K ; p H = 10; w a t e r w a s i n c o n t a c t w i t h a m o r p h o u s S i 0 ) i n a w a t e r - t o - s o l i d r a t i o of 10:1 or 3 0 : 1 , a n d the c a p s u l e w a s w e l d e d shut. T h e s e a l e d capsules w e r e t h e n w e i g h e d , h e a t e d for s e v e r a l h o u r s i n a v a c u u m o v e n , a n d r e w e i g h e d . A n y leaks i n the w e l d s w o u l d s h o w u p as w e i g h t losses d u e to e v a p o r a t i o n of t h e w a t e r t h r o u g h t h e leak. T h e experiments w e r e p e r f o r m e d i n c o n v e n t i o n a l 0.5-in. ( 1 2 . 7 - m m ) sealed g o l d capsules. T h e vessel w a s i n s e r t e d i n t o a resistance-heated c o l d - s e a l pressure vessels ( 8 ) , u s i n g w a t e r as t h e p r e s s u r i z i n g m e d i u m . I n a t y p i c a l e x p e r i m e n t e a c h vessel c o n t a i n e d three to six i n d i v i d u a l s e a l e d g o l d capsules. T h e vessel w a s i n s e r t e d i n t o a resistance-heated t u b e f u r n a c e h a v i n g a s o l i d state c o n t r o l l e r - p o w e r s u p p l y . T e m p e r a t u r e was measured w i t h a chromel-alumel thermocouple inserted into a w e l l i n the vessel n e a r the l e v e l of the g o l d capsules a n d w a s d i s p l a y e d c o n t i n u o u s l y o n a d i g i t a l readout. T h e t e m p e r a t u r e w a s n o m i n a l l y 3 0 0 ° C ; b u t o v e r the course of the t y p i c a l e x p e r i m e n t i t v a r i e d b e t w e e n 2 9 4 ° C a n d 3 0 6 ° C . P r e s s u r e , m e a s u r e d c o n t i n u o u s l y w i t h a B o u r d o n gauge, w a s 4

3

3

2

Figure

1. Typical specimen of PNL-76-68

before hydrothermal

treatment


354

SOLID S T A T E

Table I. Oxide" (waste oxides)

CHEMISTRY: A


Composition of P N L - 7 6 - 6 8 Wt%

Glass

0

Wt%

Oxide

0.53 Pr 0u 1.67 Nd 0 0.33 Sm 0 0.07 Eu 0 0.05 Gd 0 U 0 4.58 9.77 Fe 0 0.41 Cr 0 0.20 NiO 0.48 P 0 5.02° Na 0 (glass-forming additives) 7.49' Na 0 39.80 Si0 9.47 B 0 2.00 CaO 4.97 ZnO 2.97 Ti0 6

Rb 0 SrO Y 0 Zr0 Mo0 Ru0 Rh 0 PdO Ag 0 CdO Te0 Cs 0 BaO La20 Ce0

0.13 0.38 0.21 1.77 2.28 1.07 0.17 0.53 0.03 0.03 0.26 1.03 0.56 0.53 1.19

2

2

3

2

3


2

2

3

2

2

2

3

2

2

3

2

3

2

3

2

3

3

8

2

3

2

3

2

5

2

2

2

2

3

2

After Ref. 6; waste loading 33 wt % ; fission product loading 12.8 wt Composition normalized to these oxides by P N L ; the oxide compositions do not necessarily reflect the actual cation valences in the glass. Total N a 0 = 12.51 wt %. 0

6

c

2

300 ± 10 b a r . R u n d u r a t i o n s w e r e 7, 14, 2 1 , a n d 28 days. A t least t w o runs w e r e m a d e at e a c h d u r a t i o n to e v a l u a t e r e p r o d u c i b i l i t y of t h e s o l i d and solution products. C o m b i n e d t e m p e r a t u r e - p r e s s u r e c o o l i n g i n a i r w a s u s e d at t h e e n d of e a c h r u n . T h e c o o l i n g rate w a s a p p r o x i m a t e l y 10 ° C • m i n " f r o m 3 0 0 ° C to 2 0 0 ° C , 8 ° C • m i n " f r o m 2 0 0 ° C to 1 5 0 ° C , a n d 2 ° C • m i n " to 9 0 ° C . T h e capsules w e r e r e m o v e d a n d r e w e i g h e d . A n y b r e a c h of closure w o u l d s h o w u p as a w e i g h t c h a n g e . T h e capsules w e r e also e x a m i n e d m i c r o s c o p i c a l l y f o r signs of p i n h o l e s or stains f r o m l e a k e d contents. A n y r u n that h a d leaked was repeated. T h e g o l d c a p s u l e w a s c u t o p e n at o n e e n d , a n d the l i q u i d w a s p o u r e d i n t o a p l a s t i c b e a k e r . T h e o u t s i d e of the c a p s u l e , as w e l l as the scissors, w e r e g e n t l y w a s h e d w i t h d e i o n i z e d w a t e r , u s i n g a w a s h bottle. T h e c a p s u l e w a s next o p e n e d l o n g i t u d i n a l l y a n d p l a c e d i n the b e a k e r for a b o u t 10 m i n to e q u i l i b r a t e i n a b o u t 20 m t . of w a t e r . T h e s o l u t i o n f r o m the b e a k e r w a s t h e n q u a n t i t a t i v e l y t r a n s f e r r e d to a 2 5 - m L v o l u m e t r i c flask. T h e b e a k e r , the s a m p l e , a n d the g o l d c a p s u l e w e r e r i n s e d , a n d this s o l u t i o n w a s also a d d e d to t h e v o l u m e t r i c flasks. N e x t , 186 m g of K C 1 w a s a d d e d to m a k e the s o l u t i o n 0 . 1 N i n K C 1 w h e n m a d e u p to v o l u m e . T h e use of 0.1N K C 1 serves t w o p u r p o s e s : first, i t h e l p s i n the flocculation of t h e s a m p l e , i f a n y , d u r i n g c e n t r i f u g a t i o n a n d s e c o n d , i t r e m o v e s t h e ionization interference d u r i n g atomic absorption spectrophotometric analysis f o r c e s i u m , r u b i d i u m , a n d s o d i u m . T h e s o l u t i o n w a s next c e n t r i 1

1


1

19.

MCCARTHY

E T

AL.

Simulated

Radioactive

Waste

Glass

355


f u g e d i n p o l y c a r b o n a t e tubes at 2500 r e v o l u t i o n s p e r m i n u t e ( r p m ) to s e d i m e n t a n y fine p a r t i c l e s i n t h e s o l u t i o n a n d t h e n p i p e t t e d f r o m t h e p o l y c a r b o n a t e tubes i n t o p o l y e t h y l e n e bottles w i t h o u t d i s t u r b i n g a n y s e d i m e n t at the b o t t o m . A d r o p of toluene w a s a d d e d to the s o l u t i o n to prevent bacteria from growing. Characterization of Solid Products. T h e s o l i d p r o d u c t s , s t i l l c o n t a i n e d i n the o p e n g o l d c a p s u l e , w e r e i n i t i a l l y e x a m i n e d u n d e r a b i n o c u l a r m i c r o s c o p e a t u p to 40 times m a g n i f i c a t i o n . T h e extent of h y d r o t h e r m a l a l t e r a t i o n w a s first e s t i m a t e d at this stage. B e c a u s e i n a l l cases m a t e r i a l h a d b e e n t r a n s p o r t e d f r o m t h e o r i g i n a l glass s p e c i m e n o n t o t h e i n s i d e w a l l s of t h e g o l d c a p s u l e , s o l i d p r o d u c t s c h a r a c t e r i z a t i o n w a s necessary t h r o u g h o u t t h e capsule. X - r a y d i f f r a c t i o n w a s u s e d for c r y s t a l l i n e phase i d e n t i f i c a t i o n . I n d i v i d u a l clusters of crystals or a p p a r e n t l y h o m o g e n e o u s a l t e r a t i o n zones w e r e e x a m i n e d b y the G a n d o l f i c a m e r a t e c h n i q u e ( 9 ) a n d t h e b u l k product was then ground a n d studied by conventional X - r a y diffractometry. F o r the G a n d o l f i studies i n d i v i d u a l fragments or crystals w e r e extracted b y u s i n g a s h a r p e n e d n e e d l e a n d t r a n s f e r r e d to the t i p of a h o l l o w t h i n glass fiber that h a d a l r e a d y b e e n m o u n t e d i n t h e n o r m a l c a m e r a s p e c i m e n h o l d e r . T h e y w e r e c e m e n t e d to t h e fiber b y v a r i o u s m e d i a . W h e r e a cluster of crystals or several f r a g m e n t s of the same m a t e r i a l w e r e a v a i l a b l e , the crystals w e r e c r u s h e d b e t w e e n m i c r o s c o p e slides a n d the p o w d e r c a r e f u l l y c o l l e c t e d i n t o a b a l l at the t i p of the glass fiber. It w a s i m p o r t a n t to k e e p the s a m p l e size s m a l l a n d s p h e r i c a l i n o r d e r to o b t a i n s h a r p d i f f r a c t i o n lines a n d g o o d l i n e r e s o l u t i o n . H a v i n g several i n d i v i d u a l crystals o n the fiber w a s also i m p o r t a n t so that a l l o b s e r v e d D e b y e - S c h e r r e r reflections of l o w - s y m m e t r y crystals w o u l d b e i n c l u d e d o n the film. Q u a l i t a t i v e e l e m e n t a l analysis for elements a b o v e n e o n w a s o b t a i n e d b y energy-dispersive X - r a y spectrometry ( E D X ) on a scanning electron m i c r o s c o p e ( S E M ) . T h e m i c r o s t r u c t u r e s of t h e a l t e r a t i o n z o n e or m i c r o crystalline products were observed simultaneously by S E M . Quantitative e l e m e n t a l analysis a n d e l e m e n t a l d i s t r i b u t i o n s w e r e s t u d i e d o n a c o m puter-controlled electron microprobe. X - r a y p o w d e r d a t a r e a d f r o m the G a n d o l f i films, p l u s c h e m i s t r y f r o m the S E M / E D X , a l l o w e d c r y s t a l l i n e p h a s e i d e n t i f i c a t i o n to be m a d e b y reference to the J C P D S P o w d e r D i f f r a c t i o n F i l e ( P D F ) ( J O ) . The M i n e r a l Subfile of t h e PDF w a s e s p e c i a l l y u s e f u l i n this w o r k . Chemical Analyses of Solutions. S o l u t i o n s w e r e a n a l y z e d for e i g h t een of the elements i n P N L - 7 6 - 6 8 . A l l the elements e x c e p t C s , R b , N a , Z n , a n d U were analyzed w i t h a computer-interfaced atomic emission spectrometer ( A E S ) . T h e elements C s , R b , N a a n d Z n w e r e a n a l y z e d b y atomic absorption spectrophotometry ( A A S ) . U r a n i u m was determined b y a fluorometric m e t h o d . R e s u l t s of d u p l i c a t e c h e m i c a l analyses of the same s o l u t i o n h a d a m e a n d e v i a t i o n of ± 2 % . T h e o b j e c t i v e of t h e analyses is to d e t e r m i n e w h a t p r o p o r t i o n of t h e elements f r o m the glass are present i n the p r o d u c t solutions. B e c a u s e t h e p r o d u c t solutions are a l w a y s d i l u t e d to a 2 5 - m L a n a l y t i c a l s o l u t i o n , the s e n s i t i v i t y of the analyses to glass d i s s o l u t i o n is a f u n c t i o n o n l y of s p e c i m e n w e i g h t a n d the i n s t r u m e n t a l d e t e c t i o n l i m i t s . T h e l e v e l of s e n s i t i v i t y is i l l u s t r a t e d b y t h e d a t a i n T a b l e I I . D e t e c t i o n l i m i t s are


356

SOLID S T A T E

CHEMISTRY: A


Table II. Comparison of Solution Analysis Detection Limits w i t h the M a x i m u m Solution Concentration for One Specimen


0

Ulement in Glass

Maximum Solution Concentration for a 19.5-mq Specimen (tig • mlr )

Na B Si Mo Cs Rb Sr Ba Ca Zn Ni Cr Fe La Nd Ti Zr U

73.3 23.2 146.8 12.0 7.67 0.94 2.54 3.92 11.3 31.5 1.24 2.22 48.5 3.56 11.3 14.1 10.3 29.2

1

Detection Atomic Absorption Spectrophotometry

Limits

(p.Q • mL- )

Atomic Emission Spectrometry

1

Fluorimetry

— —

0.002

—

0.08 0.03 0.05 0.005 0.01

—

—

0.002

— — — — — — — —

0.05 0.2

— — —

0.01 0.2 0.002

—

0.003 0.003 0.005 0.07 not available 0.08 0.3

—

— — — — — — — — — — — — — — —

0.001

" The concentration that would be present in the 25-mL analytical solution if the specimen had completely dissolved during hydrothermal treatment.

c o m p a r e d to the c o n c e n t r a t i o n of selected elements t h a t w o u l d b e present i n the 2 5 - m L a n a l y t i c a l s o l u t i o n of a p a r t i c u l a r glass s p e c i m e n i f i t h a d t o t a l l y d i s s o l v e d d u r i n g the h y d r o t h e r m a l r u n a n d there w e r e n o i n s o l u b l e s o l i d phases f o r m e d o n c o o l i n g . F o r e x a m p l e , the d a t a i n T a b l e I I i n d i c a t e that, for this w e i g h t o f s p e c i m e n , i t w o u l d b e p o s s i b l e to detect d i s s o l u t i o n of 0 . 0 0 3 % of t h e N a , 0 . 2 5 % of the M o , 0 . 4 % of t h e Sr, 0 . 6 % of the C s , o r 0 . 0 0 3 % of t h e U present i n the o r i g i n a l glass. T h e t y p i c a l s p e c i m e n w a s t w i c e as h e a v y , so the t y p i c a l analysis w a s t w i c e as sensitive to t h e presence of a n element f r o m the glass i n t h e solutions. Results T w e n t y i n d i v i d u a l experiments w e r e p e r f o r m e d at 3 0 0 ° C a n d 300 b a r . T h e e x p e r i m e n t a l v a r i a b l e s a n d r u n n u m b e r s are l i s t e d i n T a b l e I I I . T h e results of t h e h y d r o t h e r m a l treatments of t h e glass w i l l b e d e s c r i b e d first f o r the s o l i d p r o d u c t s a n d t h e n for t h e solutions e x t r a c t e d f r o m the r e a c t i o n capsules.


19.

MCCARTHY

E T

Simulated

AL.

Radioactive

Waste

357

Glass

Table III. Experimental Parameters and R u n Numbers of the 3 0 0 ° C , 300-Bar Hydrothermal Treatments


Run

Duration (days)

Run

Number

Water

Type"

Water-to-Solids Ratio

7

G D 59 * G D 113 GH112 G D 121 GD126

DW DW HGW DW DW

10:1 10:1 10:1 30:1 30:1

14

G D 68» G D 88 G D 124 GD127 G H 150 G D 123 G D 143

DW DW DW DW HGW DW DW

10:1 10:1 10:1 10:1 10:1 30:1 30:1

21

GD GD

DW DW

10:1 10:1

28

G D 78 G D 79 G D 89 G D 90 GH111 G D 122

DW DW DW DW HGW DW

10:1 10:1 10:1 10:1 10:1 30:1

80 81

° DW t= Deionized water; HGW = artificial Hanford groundwater. These specimens were spheroids; all others were shards. 6

The

Solid Reaction

s c r i b e d elsewhere (11)

Products.

Reconnaissance

experiments

de

h a d s h o w n that p o w d e r e d P N L - 7 6 - 6 8 glass w o u l d

b e a l t e r e d b y h y d r o t h e r m a l solutions at 2 0 0 ° - 4 0 0 ° C a n d w o u l d f o r m c r y s t a l l i n e phases.

M o r e massive specimens w e r e u s e d i n t h i s s t u d y t o

e n a b l e us to f o l l o w the a l t e r a t i o n of the glass as a f u n c t i o n of t i m e . S p h e r o i d a l specimens w e r e c h o s e n for the first f e w experiments i n the e x p e c t a t i o n t h a t the h y d r o t h e r m a l a l t e r a t i o n f r o n t m i g h t e x t e n d o n l y i n t o a s m a l l p o r t i o n of t h e glass a n d thus that measurements of w e i g h t a n d v o l u m e changes as a f u n c t i o n of t i m e c o u l d b e o b t a i n e d . H o w e v e r , u p o n o p e n i n g of the first c a p s u l e , i t b e c a m e o b v i o u s t h a t , e v e n f o r times as short as 7 days, the a l t e r a t i o n of the glass w a s too extensive, a n d i t w o u l d not b e p o s s i b l e to e m p l o y these t e c h n i q u e s . A f t e r 7 days ( r y n G D 5 9 ) the a l t e r a t i o n h a d p r o c e e d e d i n t o a p p r o x i m a t e l y o n e - t h i r d of t h e s p e c i m e n a n d m a t e r i a l h a d b e e n t r a n s p o r t e d f r o m the glass a n d o n t o t h e i n s i d e w a l l s of the g o l d r e a c t i o n c a p s u l e .

F i g u r e 2 shows

a p o r t i o n of

the

cross section of this p r o d u c t m o u n t e d i n p l a s t i c a n d p h o t o g r a p h e d i n



358

SOLID S T A T E

CHEMISTRY: A


Figure 2. Cross section of a spheroidal specimen of PNL-76-68 glass after hydrothermal treatment with deionized water at 300°C and 300 bars for 7 days (approximate dimensions: 2 mm X 4 mm)

reflected l i g h t .

T h e w h i t e a n d l i g h t g r a y zones are a l t e r e d glass; t h e

b l a c k i n t e r i o r z o n e is a p p a r e n t l y u n a l t e r e d glass. T h e o v a l - s h a p e d g r a y a n d w h i t e features n e a r the i n t e r i o r of the glass c o u l d b e t r a c e d to cracks t h a t p e r m i t t e d access b y the solutions. T h e s e cracks m i g h t h a v e

been

i n t r o d u c e d d u r i n g the m e c h a n i c a l t r e a t m e n t to f o r m t h e spheroids.

The

p r o d u c t f r o m the 14-day e x p e r i m e n t ( G D 68) h a d f r a g m e n t e d a n d w a s thus not r e c o v e r a b l e

i n its o r i g i n a l s p h e r o i d a l shape.

B e c a u s e of

the

p o s s i b i l i t y of m e c h a n i c a l d a m a g e f r o m f a b r i c a t i o n of t h e spheroids, i t w a s d e c i d e d to use the less d a m a g e d glass shards i n a l l f u r t h e r experiments. T h e t y p i c a l a p p e a r a n c e of the p r o d u c t s f r o m the other 18 e x p e r i m e n t s is i l l u s t r a t e d i n F i g u r e 3. T h i s p h o t o g r a p h w a s t a k e n after the l i q u i d h a d b e e n r e m o v e d f r o m the g o l d c a p s u l e a n d t h e c a p s u l e h a d b e e n c u t o p e n . I n a l l cases the first observations w i t h t h e b i n o c u l a r m i c r o s c o p e

showed

a b u n d a n t , y e l l o w n e e d l e l i k e crystals m e a s u r i n g 0.2-2 m m a l o n g the n e e d l e axis t h a t h a d g r o w n t h r o u g h o u t the c a p s u l e a n d i n fissures i n t h e a l t e r e d s h a r d , p l u s a l i g h t - c o l o r e d c o a t i n g c o v e r i n g the i n s i d e w a l l of the capsule.



19.

MCCARTHY

Figure 3.

E T

Simulated

AL.

Radioactive

Waste

359

Glass

Typical solid products after treatment of PNL-76-68 at 300°C and 300 bar (the background is a cut-open gold capsule)

T h e product was always fragmented.

I n some cases a r e l a t i v e l y l a r g e

r e m n a n t of the o r i g i n a l s h a r d w a s present, b u t i t w a s n e s t e d i n other fragments that h a d s p a l l e d off d u r i n g the t r e a t m e n t , c o o l i n g , or o p e n i n g steps. T h e y e l l o w crystals w e r e s t u d i e d b y S E M / E D X a n d f o u n d to c o n t a i n U , S i , N a , C s , a n d m i n o r R b . F i g u r e 4 is a p h o t o m i c r o g r a p h of clusters of

these

crystals

growing

on

the w a l l s of

t h e capsule.

They

were

r e c t a n g u l a r i n cross section a n d h a d either a p i n a c o i d o r a d o m e f o r a t e r m i n a t i o n . X - r a y e x a m i n a t i o n b y the G a n d o l f i m e t h o d y i e l d e d p o w d e r d a t a that gave a v e r y g o o d m a t c h to the d a t a of the m i n e r a l w e e k s i t e , K (U0 ) (Si 0 ) 2

2

2

2

5

• 4 H 0 , p a t t e r n 12-462 i n t h e P D F ( 1 0 ) .

3

2

Table I V

is a list of the X - r a y p o w d e r d a t a for these crystals a n d for t h e m i n e r a l w e e k s i t e . T h e c o m b i n a t i o n of e l e m e n t a l c h e m i s t r y a n d X - r a y d a t a s e r v e d to i d e n t i f y these crystals as a w e e k s i t e s t r u c t u r e phase w i t h N a , C s , a n d R b s u b s t i t u t i n g for t h e K i n the p r o t o t y p e Na (U0 ) (Si 0 ) 2

of

2

2

a weeksite

2

5

3

mineral. Sodium

weeksite,

• 4 H 0 , is k n o w n ( 1 2 ) , b u t this is t h e first r e p o r t 2

s t r u c t u r e phase w i t h the l a r g e a l k a l i ions

Cs and


Rb


360

SOLID S T A T E

Figure 4.

CHEMISTRY: A


Clusters of yellow needlelike crystals (length along needle axis is typically 1-2 mm)

s u b s t i t u t i n g for K . T h e weeksites

( h e n c e f o r t h , the N a - C s - R b - w e e k s i t e

structure p h a s e w i l l b e s i m p l y r e f e r r e d to as " w e e k s i t e " ) every

observed i n

e x p e r i m e n t , w h e t h e r f o r 7 or 28 d a y s , w i t h d e i o n i z e d w a t e r or

s i m u l a t e d H a n f o r d g r o u n d w a t e r , a n d w i t h w a t e r - t o - s o l i d s ratios of

10:1

or 3 0 : 1 . I n the l o n g e r - d u r a t i o n r u n s t h e w e e k s i t e crystals a p p e a r e d to b e c o a t e d or e t c h e d a n d w e r e often n e a r l y colorless n e a r t h e i r t i p s .

The

X - r a y p a t t e r n a n d E D X c h e m i s t r y w e r e v i r t u a l l y i d e n t i c a l f o r y e l l o w as w e l l as these l i g h t e r regions of the crystals. H o w e v e r , these observations suggest t h a t the o r i g i n a l a l t e r a t i o n p r o d u c t weeksites m a y b e metastable a n d w o u l d themselves alter i n m u c h l o n g e r d u r a t i o n experiments. T h e c r e a m - or t a n - c o l o r e d p h a s e c o v e r i n g the i n s i d e of the g o l d c a p s u l e p r o v e d to b e m a d e u p o f Z-lO-pm

b l a d e l i k e crystals. F i g u r e 5 is a n S E M

p h o t o m i c r o g r a p h o f these crystals o n t h e g o l d capsule.

Their radiating

h a b i t suggests n u c l e a t i o n a n d g r o w t h f r o m s o l u t i o n o n to flaws o n the surface of the g o l d .

T h e E D X c h e m i s t r y of these crystals c o n s i s t e d of

p r i m a r y S i , F e , a n d N a , w i t h v e r y m i n o r T i , Z n , a n d p e r h a p s s e v e r a l other elements. X - r a y p o w d e r d a t a o b t a i n e d w i t h the G a n d o l f i c a m e r a s h o w e d a q u i t e g o o d i n t e r p l a n a r s p a c i n g (d)

m a t c h a n d a f a i r i n t e n s i t y (I)

to the d a t a f o r the m i n e r a l a c m i t e , N a F e S i 0 , 2

6

PDF

18-1222.

match This

i d e n t i f i c a t i o n is f u l l y consistent w i t h t h e E D X c h e m i s t r y . T a b l e V gives


19.

MCCARTHY

E T

Table IV.


Yellow

Simulated

AL.

Radioactive

Waste

361

Glass

X - r a y Powder D a t a for the Yellow Needlelike Crystals and for the Mineral Weeksite Crystals

d"

7*

8.94 7.14 5.58 4.85 4.57

ms ms s vw m

3.84 3.57 3.32

m mw m

3.20 3.00 2.93 2.81 2.52 2.41 2.38 2.30 2.24 2.18 2.15 2.11 2.00 1.982 1.936 1.905

mw vw s W W WW W

w w w W W W W

vw vw vw vw vw

Weeksite

( T D F J12-462)

d"

I'

8.98 7.11 5.57 4.83 4.58 4.48 3.84 3.55 3.34 3.30 3.20 2.99 2.91 2.80 2.51 2.41 2.37 2.28 2.29 2.20 2.13 2.11 1.994 1.973 1.922 1.905

90 100 90 30 40 30 40 70 40B 70 50 40 60 30 30 40 50 50 40 30 40 40 40 30 30 40

° Symbols: s = strong; m = medium; w == weak; v = very; B = broad reflec tion; d = interplanar spacing; I = relative intensity.

the G a n d o l f i X - r a y d a t a a n d the PDF

d a t a for a c m i t e . It is p o s s i b l e t h a t

the v e r y s m a l l size of t h e crystals a n d the p o t e n t i a l for some o r i e n t a t i o n w i t h the m o u n t i n g fiber c o u l d a c c o u n t f o r the o n l y f a i r a g r e e m e n t

of

the I d a t a . T h e v e r y l i g h t c o l o r of the a c m i t e c r y s t a l c o a t i n g w a s

somewhat

s u r p r i s i n g . I n n a t u r e , a c m i t e is u s u a l l y green or b r o w n d u e to m i n o r s o l i d s o l u t i o n substitutions a n d the p a r t i a l r e d u c t i o n of F e

3 +

to F e . T h e l i g h t 2 +

c o l o r r e q u i r e s t h a t t h e c o m p o s i t i o n b e close to s t o i c h i o m e t r i c N a F e S i 0 2

a n d that the F e b e t r i v a l e n t . T h e p r e s e n c e of a n F e

3 +

phase

6

suggests

o x i d i z i n g c o n d i t i o n s i n s i d e t h e sealed c a p s u l e . T h e u n i v e r s a l o c c u r r e n c e of the u r a n y l phase, w e e k s i t e , also supports o x i d i z i n g c o n d i t i o n s . A p p a r ently P N L - 7 6 - 6 8 w a s a n o x i d i z e d glass. T h e c o l o r of t h e a c m i t e c r y s t a l c o a t i n g turns b r o w n after several w e e k s of exposure to a i r .



362

SOLID S T A T E C H E M I S T R Y :

Figure 5.

A CONTEMPORARY

OVERVIEW

SEM photomicrograph of the crystals coating the inside of the gold capsule

MICROSTRUCTURE

A N D MICROCHEMISTRY.

The

microstructure

and

m i c r o c h e m i s t r y o f t h e b u l k p r o d u c t s f r o m a 7-day, 14-day, a n d 2 8 - d a y hydrothermal treatment were studied b y S E M a n d electron microprobe analysis.

T h e 7- a n d 14-day specimens w e r e f r o m t h e t w o r u n s w h e r e

glass spheroids h a d b e e n u s e d . A l t h o u g h t h e y w e r e c r a c k e d , these p r o d ucts w e r e n o t as f r a g m e n t e d as t h e p r o d u c t s f r o m glass shards.

Thus

they c o u l d b e h a n d l e d , m o u n t e d i n the plastic, sectioned, a n d polished w i t h less d a m a g e to the s p e c i m e n . F i g u r e 6 is a s e c o n d a r y e l e c t r o n i m a g e ( S E I ) o f t h e cross-sectioned s p h e r o i d s h o w n i n F i g u r e 2. T h e brightness o f the S E I c a n b e c o r r e l a t e d to t h e m e a n a t o m i c n u m b e r o f a m a t e r i a l a n d t o d e n s i t y . T h u s t h e a p p a r e n t l y u n a l t e r e d glass c o r e is b r i g h t , w i t h s t i l l f u r t h e r brightness f o r t h e c r y s t a l l i n e i n c l u s i o n s i n this glass. T h e a l t e r e d p o r t i o n s of t h e p r o d u c t give

a d u l l gray S E I .

Cracks i n the product

are black.

Note the

c o r r e l a t i o n o f the g r a y w h i t e o v a l - s h a p e d a l t e r a t i o n features i n F i g u r e 2 w i t h t h e g r a y zones i n t h e b r i g h t c o r e i n F i g u r e 6. S i m i l a r l y , t h e r e s i d u a l c r y s t a l l i n e i n c l u s i o n s i n t h e a l t e r e d glass z o n e t h a t w e r e d a r k g r a y i n F i g u r e 2 are b r i g h t e r t h a n t h e i r m a t r i x i n F i g u r e 6. A t h i n s k i n o r r i n d n o t e v i d e n t i n F i g u r e 2 is o b s e r v e d i n F i g u r e 6. T h i s w a s a c h a r a c t e r i s t i c f e a t u r e i n all p r o d u c t s .

U n d e r the binocular


19.

MCCARTHY

ET

Table V .

Simulated

AL.

Radioactive

363

Glass

X - r a y Powder D a t a for the Crystalline Coating and for the Mineral Acmite Coating

Acmite I

d


Waste

18-1222) I

d

50 50 10 2 100 20 30 20 10 10 10 10 2 5 2 2 5 5 5 2 5 5 5 2 2 5 2 5

6.37 4.42 3.62 3.20 2.998 2.912 2.536 2.475 2.201 2.122 2.032 1.937 1.834 1.731 1.687 1.664 1.637 1.613 1.598 1.533 1.506 1.475 1.400 1.379 1.328 1.302 1.271 1.230

(TDF

6.369 4.416 3.614 3.188 2.983 2.900 2.5408 2.4701 2.1995 2.1200 2.0162 1.9350 1.8263 1.7293

90 80 10 50 70 100 50 60 10 30 20 10 5 60

1.6590 1.6341 1.6210 1.5920 1.5377 1.5290 1.4671 1.3975

5 5 50 50 10 10 20 60

1.3283 1.3021 1.2687 1.2289

20 40 30 20

m i c r o s c o p e this s k i n w a s seen to consist of at least t w o b a n d s , a n o u t e r b a n d of w h i t e a n d a l m o s t s p h e r i c a l m a t e r i a l c o v e r i n g a n orange b r o w n inner band.

F i g u r e 7 is a n e l e c t r o n b a c k s c a t t e r

(EBS)

image

with

a c c o m p a n y i n g N a , S i , a n d F e X - r a y m a p s f o r a near-surface p o r t i o n of a 2-week r u n , G D - 6 8 .

Two

features are n o t a b l e .

First, the skin

is

e n r i c h e d i n F e a n d s e c o n d , there is a b r i g h t a r e a to the r i g h t t h a t has N a , Fe,

a n d S i concentrations.

T h i s area is p r o b a b l y

u n a l t e r e d or

only

p a r t i a l l y a l t e r e d glass. A cross s e c t i o n of the s k i n is s h o w n u n d e r h i g h e r m a g n i f i c a t i o n i n F i g u r e 8, a l o n g w i t h Sr, F e , a n d C a X - r a y m a p s .

It is

c l e a r f r o m this figure that the outer b a n d of the s k i n is r i c h i n C a a n d S r , w h i l e t h e a d j o i n i n g b a n d is F e - r i c h .

T h e X - r a y e m i s s i o n traces

across

this b a n d e d s k i n , s h o w n i n F i g u r e 9, c o n f i r m t h e e n r i c h m e n t of C a a n d Sr i n the outer b a n d a n d i n d i c a t e t h a t S i is associated w i t h F e i n t h e adjoining band.


SOLID

STATE CHEMISTRY:

A

CONTEMPORARY

OVERVIEW


364

t5

I S o

i

8 CUD



19.

MCCARTHY

ET

AL.

Simulated

Radioactive

Waste

365

Glass

Figure 7. X-ray maps of the near-surface zone of the product from run GD 68 (160 times magnification): T o p left, Na; top right, EBS; bottom left, Fe; bottom right, S i . S a m p l e s of e a c h b a n d w e r e e x a m i n e d b y G a n d o l f i X - r a y d i f f r a c t i o n , a n d c r y s t a l s t r u c t u r e types for these phases w e r e o b t a i n e d . T h e o u t e r m o s t b a n d of

w h i t e m a t e r i a l h a d the

identification was based

apatite structure t y p e .

[This

phase

o n crystals o b t a i n e d f r o m t h e surface

of

the

p r o d u c t s f r o m l o n g e r - d u r a t i o n ( 3 to 4 w e e k s ) treatments. I t is n o t c e r t a i n that the a p a t i t e s t r u c t u r e b a n d i n the 1- a n d 2 - w e e k p r o d u c t s c r y s t a l l i n e . ] X - r a y d a t a for this phase a n d f o r h y d r o x y a p a t i t e ,

were

Ca (P0 )35

4

O H , are g i v e n i n T a b l e V I . A U X - r a y m a p of the E B S i m a g e k i F i g u r e 8 s h o w e d t h a t U w a s c r y s t a l l i z i n g i n this a p a t i t e phase.

E x a m i n a t i o n of

the m a t e r i a l i n the S E M s h o w e d these spheroids t o b e a c t u a l l y m a d e u p of aggregates of r a n d o m l y o r i e n t e d fibrous crystals. T h e i r E D X c h e m i s t r y w a s q u i t e c o m p l e x , w i t h C a , S r , B a , r a r e earths ( L n ) , S i , U , a n d P as the p r i m a r y elements.

T h u s the material should be

assigned

generalized solid solution formula ( C a , S r , B a , L n , U ) „[ ( S i , P ) 0 ] O H 4

3


to

the


366

SOLID S T A T E C H E M I S T R Y : A


Figure 8. X-ray maps of a portion of Figure 7 (800 times magnification): top left, Sr; top right, EBS; bottom right, Ca; bottom left, Fe. T h e orange b r o w n b a n d gave X - r a y d a t a t y p i c a l of a p y r o x e n e c h a i n s i l i c a t e ) near t h e a c m i t e - a u g i t e , S i ) O , composition 2

e

(see PDF

(single-

(Na,Ca) (Fe,Mn,Zn,Mg,Ti) (Al,-

18-1221 a n d 1 9 - 1 ) . I n F i g u r e s 8 a n d 9 i t

w a s d e m o n s t r a t e d that this b a n d h a d h i g h - F e c o n c e n t r a t i o n , a n d i n X - r a y e m i s s i o n traces the presence of N a , Z n , a n d T i w a s o b s e r v e d . A g e n e r a l i z e d s o l i d s o l u t i o n f o r m u l a for this p h a s e is

(Na,Ca)(Fe Ti,Zn)Si 0 ;

2

6

I n the E B S i m a g e f r o m F i g u r e 8 i t is seen that there is a t h i r d , i n n e r m o s t b a n d to the s k i n .

B o t h X - r a y m a p s a n d X - r a y traces across t h e

skin

( F i g u r e 9 ) i n d i c a t e d that this b a n d w a s e s p e c i a l l y e n r i c h e d i n U r e l a t i v e to the a d j o i n i n g a l t e r e d glass zone.

This U concentration

was

higher

t h a n t h a t i n the apatite p h a s e c o n s t i t u t i n g t h e outermost b a n d . T i t a n i u m also a p p e a r e d to be c o n c e n t r a t e d i n this h i g h - U b a n d . N o p h a s e i d e n t i f i c a t i o n has as y e t b e e n m a d e f o r this i n n e r m o s t b a n d .


J 9.

MCCARTHY

E T AL

Simulated

Radioactive

Waste

Glass

367


Location of Main Structural Feature in / i m from Surface

Distance from Surface

Figure 9. X-ray from run GD 68. the left mark the and the line near

emission profiles of the near-surface zone of the product Arrows indicate the positions of cracks. Dashed lines at approximate boundaries of the three bands of the skin, the center marks the boundary between less altered and more altered glass.


368

SOLID S T A T E

Table V I .

CHEMISTRY: A

X - r a y Powder D a t a for the White Outer Band and for Hydroxyapatite Hydroxyapatite ( " P D F 9-432)

White Band

60 10

3.45 3.18



2.814

100

2.714 2.637 2.522 2.276 2.071 2.006 1.949 1.903 1.848 1.725

20 10 5 10 10 5 10 5 10 10

3.44 3.17 2.814 2.778 2.720 2.631 2.528 2.262 2.065 2.000 1.943 1.890 1.841 1.722

40 12 100 60 60 25 6 20 8 6 30 16 40 20

E l e m e n t d i s t r i b u t i o n s a m o n g the v a r i o u s a l t e r e d a n d u n a l t e r e d glass regions

were

further characterized

by

electron

microprobe

analysis.

R e s u l t s w e r e o b t a i n e d i n the f o r m of c h a r a c t e r i s t i c X - r a y e m i s s i o n traces t h r o u g h these regions a n d q u a n t i t a t i v e e l e m e n t a l analyses at spots o n the p r o d u c t .

selected

I n F i g u r e 6 the traverse of a m i c r o p r o b e s c a n is

m a r k e d b y t h e b l a c k l i n e s t a r t i n g at the b a n d e d s k i n a n d p a s s i n g t h r o u g h a r e g i o n of g e n e r a l l y a l t e r e d glass, t h e n i n t o the u n a l t e r e d c o r e , a n d t e r m i n a t i n g i n the o v a l - s h a p e d a l t e r a t i o n feature.

X - r a y e m i s s i o n traces

f o r 19 elements m o n i t o r e d d u r i n g this scan are s h o w n i n F i g u r e s 10, 11, a n d 12. T h e e n r i c h m e n t s i n N a , C a , Sr, F e , T i , a n d U i n t h e b a n d e d s k i n h a v e a l r e a d y b e e n discussed. d i d not display further major

E x c e p t f o r M o a n d N a , the X - r a y traces fluctuations

( t h e s h a r p d i p s that o c c u r i n

a l l traces i n the same p l a c e are d u e to c r a c k s ) . T h e b r o a d m a x i m u m i n M o a n d t h e sharp

fluctuations

i n N a o c c u r r i n g b e t w e e n 500 a n d 700 /xm

c o r r e l a t e w i t h t h e traverse of the b e a m out of a n a l t e r e d z o n e ,

into

u n a l t e r e d glass, a n d t h e n b a c k i n t o t h e o v a l - s h a p e d a l t e r a t i o n feature. T h i s c o r r e l a t i o n suggested the use of M o a n d N a as m a r k e r elements f o r t h e presence of a l t e r a t i o n . T h e n u m b e r s i n F i g u r e 6 m a r k i n d i v i d u a l p o i n t analyses w i t h t h e computer-interfaced microprobe.

C a l i b r a t i o n standards w e r e those a v a i l

a b l e i n the u n i v e r s i t y ' s M i n e r a l C o n s t i t u t i o n L a b o r a t o r y f o r silicate r o c k a n d m i n e r a l analyses. T h e results p r e s e n t e d i n T a b l e V I I are for 13 of the elements i n t h e glass

( p l u s K , w h i c h w a s not r e p o r t e d to be


a


19.

MCCARTHY

ET AL.

Simulated

Radioactive

Waste

Glass

369

3x10 CPS

100 200 300 400 500 600 700 /xm FROM SURFACE Figure

10.

X-ray emission traces for Na, Cs, Ca, Sr, and Zn along the traverse shown in Figure 6

c o n s t i t u e n t of t h e g l a s s ) . N o t e t h a t t h e a v a i l a b l e c o m p u t e r c o d e c a l c u l a t e d concentrations as oxides.

T h e U analyses w e r e suspect because a U

standard w i t h a suitably h i g h U concentration i n an appropriation matrix w a s n o t a v a i l a b l e . T h e r e also a p p e a r e d to b e a p r o b l e m w i t h t h e N a analyses, p e r h a p s d u e to t h e f a m i l i a r d i f f i c u l t y w i t h N a v a p o r i z a t i o n i n the e l e c t r o n b e a m .

A n a l y s e s f o r t h e 13 elements f o r a s p e c i m e n of t h e

a s - r e c e i v e d P N L - 7 6 - 6 8 glass w e r e w i t h i n 5 % o f t h e c o m p o s i t i o n s r e p o r t e d b y P N L f o r C a , T i , N d , F e , Z n , S i , a n d M o . A n a l y s e s d i f f e r e d b y greater a m o u n t s f o r C s , C e , S r , a n d Z r , as w e l l as f o r t h e p r e v i o u s l y d i s c u s s e d U a n d N a . T h e i m p o r t a n c e of these c o m p o s i t i o n a l v a r i a t i o n s is n o t k n o w n b e c a u s e t h e glass is a n i n h e r e n t l y i n h o m o g e n e o u s p r o d u c t a n d t h e P N L c o m p o s i t i o n is n o m i n a l ( t h a t i s , b a s e d o n t h e s t a r t i n g b a t c h ) r a t h e r t h a n the result of a n a c t u a l c h e m i c a l analysis.



370

SOLID S T A T E

J

0

Figure 11.

The

I

I

CHEMISTRY: A

I

I

I


I

100 200 300 400 500 600 Mm FROM SURFACE

I

700

X-ray emission traces for Fe, Y , Z r , Ti, U, Si, and Mo the traverse shown in Figure 6

microprobe

d a t a f o r t h e v a r i o u s zones i n t h e p r o d u c t

averages of m u l t i p l e analyses.

are

T h e core of a p p a r e n t l y u n a l t e r e d glass

g a v e a n analysis a v e r a g e d f r o m eight p o i n t s t h a t c o m p a r e s w e l l to t h a t of the o r i g i n a l glass s p e c i m e n . i n M o concentrations.

along

Note their

moderately

correspondence

I n a l t e r a t i o n zones I a n d I I the M o

and N a

concentrations w e r e a p p r e c i a b l y l o w e r . T h e d a t a f o r z o n e I w e r e a v e r a g e d f r o m three analyses i n the o v a l - s h a p e d feature i n F i g u r e s 2 a n d 6. T h r e e analyses f r o m the m o r e h e a v i l y a l t e r e d outer r e g i o n o c c u r r i n g b e t w e e n the s k i n a n d the core constitute z o n e I I . H e r e s o m e w h a t l o w e r F e , S i , a n d U concentrations w e r e n o t e d i n a d d i t i o n to the h e a v y d e p l e t i o n i n M o a n d N a . O n e of t h e m o s t consistent a n d u s e f u l o b s e r v a tions f r o m t h e s t u d y of this s p e c i m e n w a s t h a t M o a n d N a a p p e a r to b e e a r l y a n d sensitive i n d i c a t o r s of h y d r o t h e r m a l a l t e r a t i o n i n t h e glass.


19.

MCCARTHY

ET

Simulated

AL.


i

LJ 0 Figure 12.

Radioactive

Waste

1

1

1

1

1

1

i

i

i

i

i

i

100 200 300 400 500 600 /xm FROM SURFACE

X-ray emission traces for the lanthanides shown in Figure 6

371

Glass

r

L_J

700

along the

traverse

T h e p a r t i a l l y a l t e r e d p r o d u c t just d e s c r i b e d for t h e 1-week t r e a t m e n t d i f f e r e d m a r k e d l y f r o m t h e p r o d u c t s f r o m l o n g e r treatments. F o r s p e c i mens t r e a t e d f o r 2 to 4 w e e k s , there a p p e a r e d to be at least p a r t i a l a l t e r a t i o n t h r o u g h o u t the s o l i d .

O n e of t h e 4-week p r o d u c t s w a s suffi

c i e n t l y i n t a c t after the t r e a t m e n t that a p a r t i a l cross s e c t i o n c o u l d p r e p a r e d for e x a m i n a t i o n b y S E M a n d t h e m i c r o p r o b e .

be

I n F i g u r e 13 i t

c a n be seen that m a j o r f r a g m e n t s of t h e p r o d u c t h a d separated a n d p a r t s of t h e surface h a d s p a l l e d off p r i o r to s p e c i m e n p r e p a r a t i o n . Y e t e n o u g h of t h e p r o d u c t w a s r e t a i n e d t h a t a l l the t y p i c a l a l t e r a t i o n features w e r e d i s p l a y e d i n one cross section. T h e a l t e r a t i o n has b e e n d i v i d e d i n t o f o u r zones a n d m i c r o p r o b e analyses (see

Table V I I I ) have been

obtained

f r o m e a c h of t h e m . T h e least a l t e r e d of t h e zones w a s t h e c o r e .

I n reflected l i g h t i t

r e t a i n e d its o r i g i n a l g r e e n b l a c k c o l o r a t i o n a n d i t a p p e a r e d to


have

372

SOLID S T A T E C H E M I S T R Y : A

Table VII.

Electron Microprobe Analyses of the Product Shown i n Figure 6 ( R u n G D 50) Weight


Oxide CaO CsoO Ti0 Ce0 Nd 0 FeO ZnO Si0 SrO Zr0 Mo0 U0 K 0 Na 0 2

2

2

2

2

3

2

2

2

3


PNL-76-68 Nominal Composition"

PNL-76-68 Microprobe Analysis

2.0 1.0 3.0 1.2 1.7 8.9 5.0 40.3 0.4 1.8 2.3 4.5 0.0' 12.7 84.8

2.0 1.3 3.2 1.6 1.8 9.3 4.8 39.0 0.2 2.3 2.4 7.2' 0.1 8.6 83.8

Percent

Alteration

laltered Glass"

Zones

r

IV

1.9

2.0

2.0

1.0

1.0

0.9

2.9

2.9

2.3

2.3

3.0 2.9 2.0

1.7

1.5

8.9

8.8 5.3

5.5

38.2

5.8 5.2 34.2

42.1

0.1

0.1

0.1

2.0

1.9

2.7

2.4 5.4'

0.2 5.8' 0.3

0.8 4.3

0.1

0.1

2.1

3.1 77.3

10.5

82.9

66.1

° M o d i f i e d f r o m T a b l e I to show F e as F e O a n d U as U0 . A v e r a g e d f r o m p o i n t s 1-8 i n F i g u r e 6. A v e r a g e d f r o m p o i n t s 9-11, the o v a l - s h a p e d a l t e r a t i o n zone, i n F i g u r e 6. A v e r a g e d f r o m p o i n t s 12-14 i n F i g u r e 6. N o K was r e p o r t e d i n the c o m p o s i t i o n o f P N L - 7 6 - 6 8 . T h e U s t a n d a r d s were designed for lower U c o n c e n t r a t i o n s , so these v a l u e s be i n e r r o r . 2

b

c

d

e

1

b e c o m e m o r e t r a n s p a r e n t as a result of t h e treatment. h a d the b r i g h t s e c o n d a r y

may

T h e core zone

e l e c t r o n i m a g e t y p i c a l of u n a l t e r e d glass i n

F i g u r e 6, b u t the m i c r o p r o b e analyses ( T a b l e V I I I ) i n d i c a t e d t h a t this z o n e w a s h e a v i l y d e p l e t e d i n M o a n d N a . A n exterior core z o n e d i f f e r e d o n l y s l i g h t l y f r o m the core i n o p t i c a l a n d S E M i m a g e characteristics, b u t m i c r o p r o b e analysis i n d i c a t e d almost t o t a l d e p l e t i o n i n M o a n d a d i s t i n c t e n r i c h m e n t i n C s c o m p a r e d to the a d j o i n i n g a l t e r a t i o n zones.

T h e outer

c o r e z o n e w a s at least p a r t i a l l y c r y s t a l l i n e because a n X - r a y d i f f r a c t i o n p a t t e r n c o n s i s t i n g of b r o a d

reflections w a s o b t a i n e d f r o m i t . T h e d a t a ,

l i s t e d i n T a b l e I X , h a v e not b e e n m a t c h e d to a n y p h a s e or m i x t u r e of phases i n the P D F . I n reflected l i g h t the r e g i o n l a b e l e d " i n t e r i o r z o n e " i n F i g u r e 13 w a s cream white, porous,

and r i c h i n opaque microcrystalline inclusions.

T h e s e i n c l u s i o n s w e r e d u l l b l a c k a n d w e r e often s u r r o u n d e d b y a p u r p l e hue.

T h e y w e r e less a b u n d a n t i n t h e c o r e a n d o u t e r zones.

o r i e n t a t i o n i n the i n t e r i o r z o n e s e e m e d

Also their

to b e r e l a t e d t o the e x t e r n a l



19.

MCCARTHY

Figure 13.

ET

AL.

Simulated

Radioactive

Waste

373

Glass

SEM photomicrograph of a section through the product of a 4-week hydrothermal treatment

m o r p h o l o g y of the o r i g i n a l glass s h a r d . T h e s e t w o observations suggest t r a n s p o r t a n d r e c r y s t a l l i z a t i o n of t h e o p a q u e phases.

X - r a y diffraction

analyses i n d i c a t e d that t h e opaques consisted of several phases, a F e - r i c h spinel, ( R u 0 ) 2

8 s

, and usually

(Pd)

(the s u b s c r i p t ss refers to s o l i d

S 8

s o l u t i o n ) . T h e s p i n e l h a d a u n i t c e l l p a r a m e t e r of 8.40 A , a n d its p o w d e r d a t a c o r r e s p o n d c l o s e l y to those of the F e - s p i n e l m a g n e t i t e F e 0 , 3

19-629.

T h e R u - r i c h phase has b e e n d e s i g n a t e d as ( R u 0 ) , 2

s s

4

PDF

a solid

s o l u t i o n phase, because its p o w d e r d a t a i n d i c a t e d a s l i g h t l y l a r g e r u n i t c e l l t h a n is f o u n d f o r p u r e R u 0 , 2

PDF

21-1172.

Similarly,**in

those

products where P d - r i c h crystalline inclusions were identified, the unit c e l l p a r a m e t e r , 3.92 A , w a s l a r g e r t h a n the 3.89-A p a r a m e t e r of p u r e P d , PDF

5-681.

N o fluorite structure C e 0 - r i c h p h a s e w a s d e t e c t e d i n a n y 2

products. T h e m i c r o p r o b e d a t a for the i n t e r i o r z o n e i n d i c a t e d a d e p l e t i o n of Cs, Zr, a n d lanthanides, and enrichment i n N a , C a , F e , T i , Z n , and S i , i n c o m p a r i s o n to a d j o i n i n g zones.

T h e e n r i c h m e n t w a s most p r o n o u n c e d


374

SOLID S T A T E

Table VIII.

CHEMISTRY: A

Electron Microprobe Analyses of the Product Shown in Figure 13 ( R u n G D 78) Weight

CaO Cs 0 TiO Ce0 Nd 0 FeO ZnO Si0 SrO Zr0 Mo0 U0 Na,0

2.0 1.3 3.2 1.6 1.8 9.3 4.8 39.0 0.2 2.3 2.4 7.2 8.6 83.6

2


a

2

2

3

3

2

3

2

° Averaged Averaged Averaged Averaged 6

e

d

from from from from

Percent Alteration

PNL-76-68 Microprobe Analysis

Oxide


points points points points

Core Zone'

Exterior Core Zone"

2.1 1.4 3.1 1.4 2.1 9.6 4.3 39.1 0.4 2.2 1.1 6.1 2.0 74.9

2.1 3.1 2.9 1.4 1.9 8.7 4.5 38.9 0.3 2.1 0.1 5.3 2.4 73.7

Zones Interior Zone'

Outer Zone*

2.5 0.4 4.3 0.9 1.2 13.2 5.3 46.3 0.4 1.5 0.0 5.5 5.2 86.8

1.6 1.5 2.6 2.0 3.2 3.7 3.8 28.0 0.4 3.1 0.1 2.0 0.7 52.7

1-11 i n F i g u r e 13. 12-14 i n F i g u r e 13. 18-20 i n F i g u r e 13. 15, 21, 22, a n d 26 i n F i g u r e 13.

i n those features i n t h e i n t e r i o r z o n e that are b r i g h t e r i n F i g u r e 13. X-ray

analysis of

these

features

gave

a pyroxenelike pattern,

with

m o d e r a t e l y b r o a d reflections c o r r e s p o n d i n g to those of the a c m i t e augites d e s c r i b e d earlier. T h e m i c r o p r o b e a n d X - r a y p o w d e r d a t a are consistent w i t h a pyroxene formula,

structure p h a s e h a v i n g a g e n e r a l i z e d s o l i d s o l u t i o n

(Na,Ca) (Fe,Ti,Zn) S i 0 . 2

6

X - r a y patterns

of

representative

samples f r o m t h e i n t e r i o r z o n e s h o w e d that t h e r e w a s a c o n s i d e r a b l e a m o u n t of a n X - r a y a m o r p h o u s p h a s e m i x e d w i t h t h e p y r o x e n e

and

o p a q u e c r y s t a l l i n e phases. T h e r e g i o n l a b e l e d " o u t e r z o n e " i n F i g u r e 13 c o n s i s t e d of

light-

c o l o r e d t r a n s l u c e n t m a t e r i a l l y i n g just b e l o w the s k i n . I n reflected l i g h t this m a t e r i a l has d i s t i n c t opalescence.

W i t h the t y p i c a l p r o d u c t m u c h

of this z o n e a n d the s k i n w e r e f o u n d to h a v e s p a l l e d off. X - r a y e x a m i n a t i o n of r a n d o m samples f r o m this z o n e i n d i c a t e d t h a t i t w a s g e n e r a l l y n o n c r y s t a l l i n e . A f e w b r o a d p y r o x e n e l i k e reflections w e r e n o t e d .

Micro

p r o b e d a t a ( T a b l e V I I I ) i n d i c a t e d m a j o r d e p l e t i o n of N a , F e , S i , a n d U . T h e s e are the k e y elements of the s k i n a n d the t w o phases c r y s t a l l i z e d after t r a n s p o r t , a c m i t e a n d w e e k s i t e . N o t e t h a t the analyses of t h e oxides l i s t e d i n t h e t a b l e s u m o n l y to a b o u t 5 6 % . T h i s fact, w h e n c o m b i n e d w i t h


19.

MCCARTHY

E T AL.

Simulated

the c h a r a c t e r i s t i c opalescence

Radioactive

Waste

375

Glass

of this zone, suggests that h y d r a t e d or

h y d r o x y l a t e d , p e r h a p s g e l l i k e , m a t e r i a l has b e e n f o r m e d i n this z o n e b y the h y d r o t h e r m a l t r e a t m e n t of t h e glass. T h e s k i n , seen as a t h i n , b r i g h t l a y e r o n some of t h e m o r e i n t a c t segments i n F i g u r e 13, w a s a g a i n m a d e u p of a w h i t e crust of

small

spheres o v e r l y i n g a n orange b a n d . X - r a y d i f f r a c t i o n c o n f i r m e d that here also the o r a n g e b a n d w a s a p y r o x e n e p h a s e a n d , w i t h one e x c e p t i o n , the w h i t e crust w a s a n a p a t i t e phase.

I n that o n e e x c e p t i o n , aggregates


l o o k i n g v e r y m u c h l i k e t h e a p a t i t e p h a s e ( t h e spheres w e r e e v e n m a d e u p of t i n y n e e d l e c r y s t a l s ) , h a d q u i t e d i s s i m i l a r X - r a y p o w d e r

data

Table I X ) .

(see

Table I X .

Outer Core Zone d 4.11 3.99 3.75 3.49 3.24 2.998 2.894 2.629 2.543 2.455 2.380

J m° m ms w w ms m vs m m m

X - r a y Powder D a t a for Additional Alteration Zones or Phases Orange Vesicle Crust'

White Spherical Aggregates"

d

/

d

J

4.13 3.68 3.47 3.18 2.978 2.940 2.84 2.515 2.259 1.961 1.684 1.637 1.480 1.388 1.182 1.130 1.088 0.9022

50 5 20 20 20 20 10 60 100 50 5 10 20 10 10 5 5 5

7.03 6.56 5.13 4.82 •4.53 4.15 3.90 3.75 3.58 3.45 3.24 3.18 3.11 2.940 2.814 2.652 2.536 2.380 2.067 1.892 1.852 1.734 1.578

80 30 50 10 5 100 5 10 5 10 50 20 50 30 30 20 20 10 10 5 5 5 5

° N o t e d o n l y i n p r o d u c t s o f 2-week t r e a t m e n t s . N o t e d o n l y i n one p r o d u c t of a 4-week t r e a t m e n t ; m o r p h o l o g i c a l l y s i m i l a r t o the apatite phase. Symbols: s = strong; m = m e d i u m ; w = weak; v = very. b

c


376


A

CONTEMPORARY

OVERVIEW

T w o other a l t e r a t i o n features w e r e n o t e d . O f t e n , fissures or veins i n the a l t e r e d glass w e r e filled w i t h a t r a n s l u c e n t p a l e y e l l o w m a t e r i a l . T h i s p h a s e h a d b o t h the e l e m e n t a l c h e m i s t r y a n d c h a r a c t e r i s t i c ( a l t h o u g h b r o a d ) X - r a y reflections of the p y r o x e n e phase. A n o t h e r f e a t u r e w a s a n orange crust l i n i n g one o f the vesicles f r o m the o r i g i n a l glass. It l o o k e d q u i t e l i k e the o r a n g e p y r o x e n e b a n d o b s e r v e d o n t h e s k i n , b u t its X - r a y d a t a , g i v e n i n T a b l e I X , w e r e d i s t i n c t l y different. T h e w h i t e s p h e r i c a l aggregates

a n d orange v e s i c l e crust features


w e r e t w o examples of the n e e d f o r u t i l i z i n g m u l t i p l e m e t h o d s of c h a r a c t e r i z a t i o n i n this w o r k .

I f v i s u a l or S E M a p p e a r a n c e h a d b e e n

used

alone, t h e n the phases w o u l d h a v e b e e n m i s i d e n t i f i e d as a p a t i t e a n d pyroxene, respectively. BULK X-RAY

DIFFRACTION.

A t least o n e

p r o d u c t t r e a t e d at

each

different set of c o n d i t i o n s ( t i m e , w a t e r t y p e , w a t e r - t o - s o l i d r a t i o ) w a s s t u d i e d i n b u l k specimens b y r o u t i n e X - r a y d i f f r a c t o m e t r y . A l l t h e solids w e r e c o l l e c t e d f r o m i n s i d e the g o l d capsules a n d w e r e g r o u n d together to m a k e u p the diffractometer s p e c i m e n . T h e r e s u l t i n g d i f f r a c t i o n patterns w e r e r e m a r k a b l y s i m i l a r to e a c h other a n d to patterns of p r o d u c t s f r o m other h y d r o t h e r m a l e x p e r i m e n t s i n v o l v i n g P N L - 7 6 - 6 8 glass. T h e diffractog r a m of the o r i g i n a l glass s p e c i m e n is c o m p a r e d to t h a t of the p r o d u c t s of a t y p i c a l a l t e r a t i o n p r o d u c t ( r u n G H 111) i n F i g u r e 14. T h e glass is X - r a y a m o r p h o u s except f o r a f e w w e a k reflections o f ( R u 0 ) , ( C e 0 ) s s , 2

and

s s

2

the F e s p i n e l ( s ) , w h i l e the a l t e r a t i o n p r o d u c t has strong reflections

f r o m c r y s t a l l i n e phases.

T h e b r o a d h a t c h e d reflections are d u e to the

v a r i o u s a c m i t e a n d a c m i t e - a u g i t e p y r o x e n e phases a n d a l l b u t a f e w of t h e r e m a i n i n g reflections are those of the w e e k s i t e l i k e phase.

One

of

these extra reflections is consistent w i t h the strongest a p a t i t e phase reflec t i o n , but,' i n g e n e r a l , the other phases t h a t w e r e so c l e a r l y d i s c e r n i b l e as t i n y crystals b y t h e G a n d o l f i t e c h n i q u e are a p p a r e n t l y b e l o w the l e v e l of detection b y b u l k X - r a y diffraction. T h e same b a s i c d i f f r a c t o g r a m w a s o b t a i n e d for six other r u n p r o d u c t s w h e r e a 10:1 w a t e r - t o - s o l i d s r a t i o h a d b e e n u s e d . T h e major

difference

b e t w e e n 1 a n d 4 w e e k s of t r e a t m e n t w a s i n the s h a r p e r a n d m o r e intense p y r o x e n e reflections o b s e r v e d f o r t h e l o n g e r treatments. I n the diffractograms of the 4-week, 3 0 : 1

water-to-solid-ratio product,

the

weeksite

reflections w e r e just as e v i d e n t , b u t those of the pyroxenes w e r e m u c h less intense.

T h e r e w a s also a l a r g e r diffuse

scattering halo, w h i c h

suggested a h i g h e r p r o p o r t i o n of X - r a y a m o r p h o u s phases i n t h i s p r o d u c t . T h e w e e k s i t e p l u s pyroxenes phase assemblage w a s also o b s e r v e d i n a n o t h e r set o f h y d r o t h e r m a l treatments d e s c r i b e d elsewhere

(11).

In

these a 2 0 0 - m e s h p o w d e r of P N L - 7 6 - 6 8 glass h a d b e e n t r e a t e d at 3 0 0 ° C and

300 b a r f o r a n e x t e n d e d p e r i o d of t i m e .

T h e water-to-solid ratio

w a s 0.5:1 r a t h e r t h a n 10:1 or 3 0 : 1 . D i f f r a c t o g r a m s of 4-, 8-, a n d 24-week p r o d u c t s w e r e v e r y s i m i l a r to t h a t of t h e a l t e r e d glass i n F i g u r e 14.



19.

MCCARTHY

8

12

ET AL.

16

Simulated

20

Radioactive

24 28 DEGREES 26 (CuKa)

377

Waste Glass

32

36

40

Figure 14. Portions of the X-ray diffractograms for PNL-76-68 before hydrothermal treatment and after treatment with artificial Hartford groundwater at 300°C and 300 bar for 28 days (run GH 111) I n another series of experiments w i t h the p o w d e r e d

glass a n d the

0.5:1 r a t i o , the w e e k s i t e - p l u s - p y r o x e n e s assemblage w a s w e l l c r y s t a l l i z e d after o n l y 2.5 days at 4 0 0 ° C a n d 300 b a r , a n d i t w a s seen to b e s t a r t i n g to c r y s t a l l i z e after the same 2.5-day t r e a t m e n t at 2 0 0 ° C a n d 300 b a r Chemical Analyses of Solutions.

(13).

T h e p r o d u c t solutions f r o m e a c h

g o l d c a p s u l e w e r e a n a l y z e d for 18 of the elements present i n P N L 76-68 b y the t e c h n i q u e s

described

above.

These

analyses c o v e r e d

elements w h o s e oxides w e r e present at greater t h a n 1 w t % (see

a l l the

except R u

T a b l e s I a n d I I ) . M o r e t h a n 96 w t % of the o x i d e c o m p o s i t i o n of

the glass w a s i n c l u d e d . T h e r e are t w o p o t e n t i a l c o n t r i b u t i o n s to these solutions. F i r s t , there are the elements that h a d b e e n e x t r a c t e d f r o m the glass d u r i n g t h e h y d r o t h e r m a l t r e a t m e n t a n d h a d r e m a i n e d i n s o l u t i o n d u r i n g the c o o l i n g of the r u n . A s e c o n d c o n t r i b u t i o n c o u l d c o m e f r o m a n y s o l i d p r o d u c t s t h a t were

sufficiently s o l u b l e to h a v e d i s s o l v e d d u r i n g e i t h e r the

10-min

e q u i l i b r a t i o n of the c a p s u l e i n 20 m L of w a t e r or the s u b s e q u e n t w a s h i n g of the s o l i d p r o d u c t s . T h i s s e c o n d c o n t r i b u t i o n m i g h t i n c l u d e s u c h salts as s o d i u m m o l y b d a t e s or borates t h a t either h a d f o r m e d

as solids at


378


A CONTEMPORARY

OVERVIEW

t e m p e r a t u r e because t h e s o l u t i o n w a s a l r e a d y s a t u r a t e d or h a d p r e c i p i t a t e d f r o m s o l u t i o n d u r i n g t h e c o o l i n g of t h e r u n . I n t h e d i s c u s s i o n t h a t follows both contributions w i l l be considered under the "solutions" por t i o n of t h e p r o d u c t s . SOLUTIONS

FROM

RUNS

USING

DEIONIZED WATER.

The

analyses

of

the solutions f r o m 12 of t h e r u n s u s i n g d e i o n i z e d w a t e r a r e g i v e n i n T a b l e X . B e c a u s e every s p e c i m e n h a d a different w e i g h t , t h e c o n c e n t r a tions h a v e b e e n n o r m a l i z e d to a s p e c i m e n w e i g h t of 0.1 g t o f a c i l i t a t e


c o m p a r i s o n s a m o n g runs.

T h e elements present i n t h e solutions i n t h e

greatest concentrations w e r e N a , B , a n d M o . R e p r o d u c i b i l i t y a m o n g r e p l i c a t e r u n s t h a t u s e d glass s h a r d specimens

(that is, a l l b u t G D 59

a n d G D 6 8 ) w a s w i t h i n 1 0 % o f t h e a m o u n t present f o r these t h r e e elements. T h i s w a s a b o u t that e x p e c t e d f r o m t h e v a r i a t i o n i n s p e c i m e n c o m p o s i t i o n d u e to v a r i a b l e c o n t e n t of c r y s t a l l i n e i n c l u s i o n s . N o t e , f o r e x a m p l e , t h e C r analyses i n t h e 2-week runs. I n G D 124 there w a s n o n e d e t e c t e d , w h i l e i n G D 127 there w e r e 42 fig • m L of C r i n s o l u t i o n . C h r o m i u m is t h o u g h t to b e p r e s e n t i n P N L - 7 6 - 6 8 i n t h e s p i n e l ( s ) ( 5 , 7 ) , so G D 124 m a y h a v e c o n t a i n e d less of this c r y s t a l l i n e i n c l u s i o n t h a n G D

127. O t h e r i m p o r t a n t constituents of t h e solutions w e r e S i a n d C s .

R e p r o d u c i b i l i t y , a m o n g r e p l i c a t e analyses f o r these elements, w a s o n l y w i t h i n a f a c t o r of t w o to three t i m e s t h e a m o u n t present.

Table X .

Solution Concentrations"

1 Week


2 Weeks

GD59"

GD 113

GD68"

GD88

1800 1300 750 1300 19 ND* 0.8 0.7 2.4 ND

4300 2500 510 1100 42 ND 2.0 7.4 7.4 0.8 1.5 66 3 4 ND ND ND 5.6

3900 3000 710 1100 110 6 ND

3900 2500 1070 1100 58 3 0.3 0.5 2.8 0.7 2.5

—

ND ND ND ND ND 2.6

ND 7.8 29.0 —

ND ND ND ND ND 4.8

—

N N N N

—

D D D D 1.1

GD

124

GD 127

3900 2500 430 1100 33 2 2.4 11.6 9.8 1.5 2.6 ND 3 4 ND ND ND 0.6

* I n micrograms per milliliter. T h e s e specimens were i n the f o r m of s p h e r o i d s . 6


4700 2800 620 1100 74 ND 2.8 13.1 10.9 0.9 3.1 42 4 ND ND ND ND 6.2

19.

MCCARTHY

E T AL.

Simulated

Radioactive

Waste

379

Glass

T h e most n o t a b l e aspect of t h e d a t a i n T a b l e X is t h a t ( w i t h t h e e x c e p t i o n of G D 59, d i s c u s s e d l a t e r ) t h e c o n c e n t r a t i o n s are r o u g h l y t h e same f o r t h e f o u r r u n d u r a t i o n s . T h i s aspect b e c o m e s e v e n m o r e e v i d e n t w h e n analyses f r o m t h e r e p l i c a t e d runs are a v e r a g e d . I n T a b l e X I these a v e r a g e d concentrations are g i v e n a l o n g w i t h t h e p e r c e n t a g e

of t h e

p a r t i c u l a r e l e m e n t f r o m t h e o r i g i n a l glass r e p r e s e n t e d b y these c o n c e n t r a tions. I t s h o u l d b e n o t e d t h a t this p e r c e n t a g e is o n l y t h e a m o u n t of a n element d e t e c t e d i n the a n a l y t i c a l s o l u t i o n a n d n o t t h e t o t a l p e r c e n t a g e


of a n element extracted o r l e a c h e d f r o m t h e glass.

T h e latter w o u l d

i n c l u d e at least t h e c o m p o n e n t s of t h e w e e k s i t e a n d a c m i t e phases t h a t w e r e d i s s o l v e d , t r a n s p o r t e d , a n d c r y s t a l l i z e d o n t h e i n s i d e w a l l s of t h e g o l d capsule.

T h e c o n c e n t r a t i o n s of N a , M o , a n d C s i n s o l u t i o n w e r e

n e a r l y constant f o r a l l f o u r d u r a t i o n s at a b o u t 4 5 % , 7 0 % , a n d 5 % of t h e a m o u n t a v a i l a b l e i n t h e glass. T h e B a n d R b c o n c e n t r a t i o n s i n c r e a s e d g r a d u a l l y w i t h t i m e of treatment. S o m e S i , a b o u t 4 % , w a s o b s e r v e d . V e r y little of t h e a v a i l a b l e a l k a l i n e earths, C a , S r , a n d B a , w a s f o u n d i n the solutions. T h e r e w a s v i r t u a l l y n o d e t e c t a b l e T i , Z n , Z r , L a , o r N d i n t h e solutions. O n l y a v e r y s m a l l p e r c e n t a g e of t h e a v a i l a b l e U w a s present i n solution a n d that percentage decreased w i t h longer treatment times. It is i n s t r u c t i v e to c o n s i d e r t h e t o t a l c o n c e n t r a t i o n of t h e elements i n s o l u t i o n as a p e r c e n t a g e of t h e a v a i l a b l e concentrations of t h e 18 elements

(10:1

Deionized W a t e r to Glass) 3 Weeks

4 Weeks

GD80

GD 81

GD78

GD79

GD89

GD90

4000 2500 1280 1100 50 5 0.6 0.4 15.4 1.0 ND 47 ND ND

4300 2800 1140 1000 40 3 0.8 0.1 2.4 1.0 2.3 53 ND ND

4300 2600 1180 1100 50 10 ND 0.8 9.0 ND 12.4

4400 2900 1290 1200 48 11 ND ND 10.0 ND 9.8

4200 2800 450

3900 2700 550

ND

ND

ND ND 1.5

ND ND 0.6

ND ND 0.9

— —

—

ND ND 0.9 c

N D =

—

—

—

—

—

—

1.2 0.6 30.5 0.8 1.3 73 1 3 ND ND ND 1.8

none detected.


0.7 0.4 20.3 0.1 f.9 80 1 3 ND ND ND 0.9

380

SOLID S T A T E

Table X I .

CHEMISTRY: A CONTEMPORARY OVERVIEW

Average Solution Concentration and Percentage 1 Week"

%

pig • mL'


1


2

4300 2500 510 1100 42 ND' 2.0 7.4 7.4 0.8 1.5 66 3 4 ND ND ND 5.6

Weeks

0

fig • mL'

%

4200 2600 700 1100 55 2 1.8 8.4 7.9 1.0 2.8 21 4 1 ND ND ND 2.6

45 87 3.7 72 5.6 1.4 0.55 1.67 0.55 0.02 1.76 8 0.06 0.24

1

46 84 2.7 72 4.3

—

0.62 1.47 0.51 0.02 0.94 23 0.05 0.88

— — —

0.15

— — —

0.07

° G l a s s s p h e r o i d r u n s G D 59 a n d G D 68 were n o t i n c l u d e d i n the average.

f r o m t h e glass that w e r e i n c l u d e d i n t h e c h e m i c a l analyses.

A f t e r first

c o n v e r t i n g e l e m e n t a l i n t o o x i d e concentrations, w e f o u n d t h a t 1 7 - 1 9 w t % of t h e glass w a s o b s e r v e d i n s o l u t i o n after a n y o n e of t h e f o u r h y d r o t h e r m a l treatments. analyses a c c o u n t e d percentage

[ N o t e t h a t t h e elements i n c l u d e d i n t h e c h e m i c a l f o r o n l y f o r o n l y 96.2 w t %

might change

b y 0.5^1 w t %

of t h e glass.

This

i f , at some later t i m e , t h e

r e m a i n i n g elements i n P N L - 7 6 - 6 8 ( R u , Y , R h , P d , A g , C d , T e , P r , S m , E u , G d , P ) w e r e i n c l u d e d i n t h e c h e m i c a l analyses.]

There was a small

increase i n p e r c e n t a g e w i t h t i m e of t r e a t m e n t : 1 2 3 4

week weeks weeks weeks

16.8% 17.2% 18.5% 18.5%

T h e results o f t h e analyses f r o m G D 59, t h e 1-week r u n t h a t u s e d a s p h e r o i d a l s p e c i m e n , a p p e a r e d to b e a n o m a l o u s w h e n c o m p a r e d , to t h e t r e n d of t h e o t h e r analyses. T h e c o n c e n t r a t i o n s of N a , B , a n d C s w e r e o n l y h a l f those f o u n d f o r t h e runs W i t h t h e glass s h a r d specimens. t h e C s analysis i n G D 68, the o t h e r

Also,

glass s p h e r o i d r u n , w a s h i g h .

A l t h o u g h t h e p o s s i b i l i t y o f a systematic a n a l y t i c a l error c a n n o t b e r u l e d


19

MCCARTHY

Simulated

ET AL.

Radioactive

Waste

381

Glass

of Element in Solution (10:1 Deionized Water to Glass) 3 Weeks

4 Weeks

p.g • mL'

%

ix.g • mL'

%

4100 2700 1210 1100 45 4 0.7 0.2 8.9 1.0 1.1 50 ND ND

44 89 6.4 72 4.6 3.4 0.22 0.04 0.62 0.02 0.69 18

4200 2800 870 1100 49 11 0.5 0.5 17.4 0.2 6.3 77 1 2 ND ND ND 1.0

45 93 4.6 72 5.0 8.7 0.15 0.1 1.20 0.005 3.96 27 0.02 0.48


1

—

— — — —

—

ND ND 1.2 6

N D=

1

0.03

— — —

0.03

none detected.

out, i t seems l i k e l y t h a t t h e r a d i c a l difference i n t h e surface c o n d i t i o n b e t w e e n t h e t w o types of specimens w a s r e s p o n s i b l e f o r different amounts of a l t e r a t i o n a n d thus t h e a p p a r e n t l y a n o m a l o u s s o l u t i o n analyses. O n e e x p l a n a t i o n f o r t h e a p p r o x i m a t e c o n s t a n c y of s o l u t i o n c o n c e n trations after o n l y one w e e k of t r e a t m e n t m i g h t b e that t h e solutions s i m p l y h a v e b e c o m e s a t u r a t e d i n v a r i o u s elements. I n o r d e r to test this e x p l a n a t i o n , five runs w e r e m a d e w h e r e t h e d e i o n i z e d water-to-glass r a t i o w a s i n c r a s e d t o 3 0 : 1 . I f t h e solutions b e c a m e s a t u r a t e d i n 1 0 : 1 w a t e r - t o s o l i d r a t i o e x p e r i m e n t s , t h e percents of elements e x t r a c t e d i n 3 0 : 1 w a t e r t o - s o l i d r a t i o experiments w h e n e q u i l i b r i u m w a s a t t a i n e d s h o u l d b e t h r e e times as m u c h as i n 1 0 : 1 w a t e r - t o - s o l i d r a t i o experiments.

Analytical

results f r o m these r u n s a r e l i s t e d i n T a b l e X I I . T h e S i content i n s o l u t i o n increased substantially w h i l e N a increased slightly, B r e m a i n e d about the same, a n d M o s h o w e d a s u b s t a n t i a l decrease.

T h e s e results i n d i c a t e t h a t

i n t h e 1 0 : 1 w a t e r - t o - s o l i d r a t i o experiments t h e s o l u t i o n m i g h t

have

b e c o m e s a t u r a t e d o n l y w i t h respect t o S i . SOLUTIONS

FROM

RUNS

USING

ARTIFICIAL

HANFORD

GROUNDWATER.

A l l t h e experiments discussed so f a r h a v e u t i l i z e d d e i o n i z e d w a t e r ( D W ) . A t first i t w o u l d a p p e a r that to m a k e t h e e x p e r i m e n t m o r e r e l e v a n t , H a n f o r d groundwater ( H G W ) should have been used. H o w e v e r , it c a n


382

SOLID S T A T E


Table X I I . Percent of Element in Solution (30:1 Deionized Water to Glass)


1 Week* Na B Si Mo Cs Rb Sr Ba Ca Zn Ni Cr Fe La Nd Ti

55 81 11.5 52 2.6 b 0.6 1.8 0.4 0.03 0.8 20 0.01

— — —

Lv U a

6

2 Weeks*

4 Weeks

55 91 8.3 59 5.1

67 91 7.8 46 3.6

0.4

—

0.13 1.6 13

0.06 0 28

— — — —

— — — —

0.20

0.22

0.11

A v e r a g e of d u p l i c a t e s . I n d i a c t e s t h a t e l e m e n t was b e l o w the l e v e l of d e t e c t i o n .

be s h o w n that g r o u n d w a t e r s t y p i c a l of those b e n e a t h t h e H a n f o r d site are so l o w i n t o t a l d i s s o l v e d solids ( T D S ) t h a t , i n these

closed-system

h y d r o t h e r m a l e x p e r i m e n t s , soon after t h e e x p e r i m e n t b e g i n s t h e solutions w o u l d c o n t a i n f a r greater concentrations of T D S released f r o m t h e glass t h a n w e r e present i n t h e o r i g i n a l H G W .

F o r e x a m p l e , w h e n a 0.1-g

s p e c i m e n of glass releases 1 7 % of its constituents i n t o 1.0 m L o f s o l u t i o n , that s o l u t i o n w o u l d c o n t a i n 17,000 fig • m L

- 1

of t o t a l d i s s o l v e d solids.

T h i s c o m p a r e s to t h e 420 fig • m L " of T D S i n t h e a r t i f i c i a l H G W 1

d e s c r i b e d i n t h e e x p e r i m e n t a l p r o c e d u r e s section. T h e H G W w o u l d m a k e a c o n t r i b u t i o n of less t h a n 3 % to t h e T D S i n s u c h a r u n . T h r e e e x p e r i ments w e r e p e r f o r m e d to test t h e v a l i d i t y of this a r g u m e n t . T h e results of c h e m i c a l analyses f o r solutions f r o m 1-, 2-, a n d 4-week treatments of t h e glass w i t h a n artificial H G W a r e g i v e n i n T a b l e X I I I . F o o t n o t e b to this table gives the results of a c o n c u r r e n t c a t i o n analysis of t h e H G W . A f t e r s u b t r a c t i n g t h e c o n t r i b u t i o n of N a f r o m t h e H G W , it is e v i d e n t t h a t t h e r a n g e of N a concentrations d u p l i c a t e s t h e results of t h e c o m p a r a b l e D W experiments.

S i m i l a r l y , w i t h t h e other

major

constituents of t h e solutions, B , M o , a n d C s , t h e c o n c e n t r a t i o n ranges w e r e i n g o o d a g r e e m e n t w i t h t h e c o r r e s p o n d i n g D W experiments. A m o n g t h e m i n o r elements, C s a n d C r concentrations w e r e s o m e w h a t and S i was lower.

higher

I n g e n e r a l , these results s u p p o r t t h e p o s i t i o n t h a t


19.

MCCARTHY

ET AL.

Simulated

Radioactive

Waste

383

Glass

Table XIII. Solution Concentrations ( 1 0 : 1 Artificial H a n f o r d G r o u n d w a t e r to Glass) 0


b

Na B Si Mo Ca Rb Sr Ba Ca Zn Ni Cr Fe La Nd Ti Zr U

1 Week GH112

2 Weeks GH150

4 Weeks GH111

4600 2600 430 1200 86 2 2.0 8.4 7.5 ND 0.9 149 ND 5 ND ND ND 4.6

4100 2800 350 1200 85 ND" ND 2.2 ND ND ND 126 ND ND ND ND ND 3.5

4400 2700 190 1200 44 ND ND 6.1 32.2 0.4 ND 132 ND ND ND ND ND ND

" I n micrograms per milliliter. A n a l y z e d c o n c e n t r a t i o n s (fig • m L ' ) : tected. N D = none detected. 6

1

170 N a , 60 S i , 6.8 K , 0.4 M g ; n o C a d e

e

d e i o n i z e d w a t e r is a q u i t e satisfactory g e n e r i c g r o u n d w a t e r s in closed-system Discussion and

stand-in for l o w - T D S

experiments.

Conclusions

T h e results p r e s e n t e d s h o w t h a t , i n t h e l a b o r a t o r y , t h e r a d w a s t e glass reacts w i t h w a t e r u n d e r t h e t e m p e r a t u r e - p r e s s u r e r e g i m e o f 3 0 0 ° C a n d 300 b a r . R e a c t i o n f o r times o n t h e o r d e r of w e e k s r e s u l t e d i n t h e c o n v e r s i o n of a s o l i d s h a r d of glass into a f r a g m e n t e d a n d p a r t i a l l y d i s p e r s e d mass of c r y s t a l l i n e a n d n o n c r y s t a l l i n e m a t e r i a l p l u s d i s s o l v e d species.

T h e m o r e massive s o l i d p r o d u c t s w e r e c o m p o s i t i o n a l l y b a n d e d

a n d z o n e d , w h i c h is a c o m m o n i n d i c a t i o n o f t h e n o n a t t a i n m e n t of e q u i l i b r i u m . Y e t t h e s o l i d c r y s t a l l i n e p r o d u c t s a n d t h e species r e t a i n e d i n t h e solutions d i d n o t v a r y greatly o v e r t h e f o u r r e a c t i o n times u s e d . I t appears t h a t there is a r a p i d i n i t i a l r e a c t i o n of t h e w a t e r w i t h t h e glass to f o r m a v a r i e t y of r e c r y s t a l l i z a t i o n p r o d u c t s , f o l l o w e d b y a m u c h l o n g e r t i m e o f n e a r l y steady state c o n d i t i o n s . A l t h o u g h final t h e r m o d y n a m i c e q u i l i b r i u m w a s n o t r e a c h e d f o r t h e system as a w h o l e , m a n y of t h e c r y s t a l l i n e phases a r e l i k e l y to b e s t a b l e u n d e r t h e P - T c o n d i t i o n s o f t h e experiments.


384

SOLID S T A T E

CHEMISTRY: A


W a t e r p l a y s three d i s t i n c t a n d i m p o r t a n t roles i n the d e g r a d a t i o n of the glass: as a solvent a n d catalyst for glass r e c r y s t a l l i z a t i o n [ l o n g k n o w n to geochemists w h o use glasses as r e a c t i v e s t a r t i n g materials for h y d r o thermal phase

e q u i l i b r i u m experiments

c a r r y i n g elements

(8)];

as a t r a n s p o r t

medium

extracted f r o m the solids to different parts of

the

c a p s u l e a n d r e d e p o s i t i n g t h e m at t e m p e r a t u r e or d u r i n g c o o l i n g as the o b s e r v e d c r y s t a l l i n e c a p s u l e - l i n i n g phases; a n d as a c o m p o n e n t f o r m a t i o n of h y d r a t e d or h y d r o x y l a t e d phases

for the

s u c h as w e e k s i t e

and


apatite. The

Occurrence of Key Elements in Solid and Solution Products.

k e y elements are those that h a v e p o t e n t i a l l y h a z a r d o u s a n d r e l a t i v e l y long-lived radionuclides.

I n h i g h - l e v e l n u c l e a r wastes f r o m l i g h t - w a t e r

reactors, these elements ( r a d i o n u c l i d e s ) w o u l d i n c l u d e C s ( Np(

2 7 3

Np),

Tc ( Tc). 9 9

Pu(

2 3 9

Pu), Am (

2 4 1

'

2 4 3

Am),

Cm (

2 4 3

-

2 4 4

Cm),

1 3 7

Cs), Sr( Sr), 90

I (

1 2 9

I ) , and

O n l y t w o of these elements, C s a n d Sr, are present i n t h e

s i m u l a t e d h i g h - l e v e l w a s t e glass u s e d i n this i n v e s t i g a t i o n . there is c o n s i d e r a b l e

However,

(though certainly not complete) analogy

between

the c r y s t a l c h e m i s t r y a n d s o l u t i o n s p e c i a t i o n of N p a n d P u w i t h U , a n d A m a n d C m w i t h the l a n t h a n i d e s ( L n ) .

T h u s U a n d t h e L n ' s w i l l be

i n c l u d e d a m o n g t h e k e y elements d i s c u s s e d b e l o w . C o n c e r n i n g t h e solutions, i t s h o u l d be n o t e d a g a i n t h a t o n l y those elements r e m a i n i n g i n s o l u t i o n or f o r m i n g i n r e a d i l y s o l u b l e s o l i d phases d u r i n g the c o o l d o w n f r o m 3 0 0 ° C w o u l d b e o b s e r v a b l e i n the p r o d u c t solutions. T h e r e w e r e c e r t a i n l y other species i n s o l u t i o n at t e m p e r a t u r e t h a t either g r e w i n t o crystals d u r i n g the course of the r u n or p r e c i p i t a t e d o n c o o l i n g to f o r m phases that w e r e not d i s s o l v e d d u r i n g the subsequent procedures

u s e d to separate

solids f r o m solutions.

T h e weeksite

and

a c m i t e phases a n d , p r o b a b l y , the m u l t i p h a s e b a n d e d s k i n are examples of s u c h s o l i d phases. T a b l e X I V is a c o m p i l a t i o n of the occurrences

of e a c h P N L - 7 6 - 6 8

element i n s o l i d a l t e r a t i o n p r o d u c t s a n d i n solutions of the 10:1 w a t e r ( D W or H G W ) t o - s o l i d - r a t i o experiments. T h e occurrences i n solids are b a s e d o n S E M / E D X observations a n d m i c r o p r o b e X - r a y m a p s a n d X - r a y e m i s s i o n traces. T h e assignment of structure types a n d g e n e r a l i z e d s o l i d solution

formulas

resulted

from

X - r a y diffraction

studies.

The

key

elements are i n i t a l i c . C e s i u m w a s o b s e r v e d i n w e e k s i t e a n d i n c e r t a i n of the n o n c r y s t a l l i n e s o l i d ( N C S ) a l t e r a t i o n zones. S o m e 4 - 9 % of the C s a v a i l a b l e i n the glass w a s f o u n d i n the p r o d u c t solutions. s o l u t i o n , a n d its occurrences

O n l y traces of Sr w e r e f o u n d i n

i n the s o l i d p r o d u c t s w e r e i n the apatite

b a n d of the s k i n a n d i n v a r i o u s N C S a l t e r a t i o n zones.

Uranium

was

f o u n d i n m a n y of the solids b u t o n l y i n trace q u a n t i t i e s i n solutions. X - r a y e m i s s i o n traces of the l a n t h a n i d e s s h o w e d t h a t t h e y w e r e r e l a t i v e l y w e l l d i s t r i b u t e d a m o n g the N C S a l t e r a t i o n zones.

T h e only crystalline


19.

MCCARTHY

Simulated

ET AL.

Table X I V .

Radioactive

Waste

385

Glass

Occurrence of Elements i n Solids and Solutions Solutions (%)

11


Element

Solids

Na Si B Ca Zn Ti Rb Sr Zr Mo Ru Pd Cs Ba Ln

a c m i t e / acmite augites/ weeksite/ N C S a c m i t e , a c m i t e augites, w e e k s i t e , a p a t i t e a c m i t e augites, a p a t i t e s , N C S a c m i t e augites, N C S a c m i t e augites, N C S weeksite apatite, N C S NCS NCS (Ru0 ) (Pd) weeksite, N C S apatite, N C S apatite, N C S

U Fe Cr P Ni Te,Rh,Ag,Cd'

weeksite, a p a t i t e , N C S a c m i t e , a c m i t e augite, s p i n e l / N C S spinel apatite spinel —

8

2

8 8

8 S

h

r

44-47 1-6 84-93 0.5-2 0.2-0.05 N D ' ND-9 0.2-0.6 N D 68-78 — 4-9 0.04-2 0.2-0.9 (La, Nd) 0.03-O.15 ND-0.06 18-54 — 0.7-4 —

° P e r c e n t a g e of t h e a m o u n t o f t h e e l e m e n t present i n P N L - 7 6 - 6 8 t h a t was d e tected i n s o l u t i o n s f r o m t h e 10:1 w a t e r - t o - s o l i d - r a t i o r u n s . Acmite = N a F e S i O . A c m i t e augite = ( N a , C a ) ( F e , Z n , T i ) S i 0 . Weeksite = (Na,Cs,Rb)2(U0 )2(Si20 )3 • 4 H 0 . N C S = n o n c r y s t a l l i n e s o l i d s ; g e n e r a l d e s i g n a t i o n of the X - r a y a m o r p h o u s a l t e r a t i o n zones. ' Apatite = (Ca,Sr3a,Ln,U) [(Si,P)0 ]3(OH). N D = none detected. L n= Y,La,Ce,Pr,Nd,Sm,Eu,Gd. * Spinel = (Zn,Ni,Fe) ( F e , C r ) 0 . N o t i n c l u d e d i n a n y o f the analyses. 6

2

e

c

2

d

2

5

6

2

6

5

4

9

h

2

4

1

host f o r t h e L n elements w a s t h e a p a t i t e s t r u c t u r e p h a s e t h a t m a d e u p the outermost b a n d o f the s k i n .

L e s s t h a n 1 % of ( L a +

N d ) was

o b s e r v e d i n a n y of the v a r i o u s s o l u t i o n analyses. T h u s of t h e k e y elements, o n l y C s occurs i n t h e p r o d u c t solutions i n s u b s t a n t i a l a m o u n t s . It is i n t e r e s t i n g t o look at t h e b e h a v i o r o f some of t h e other elements. A p p r o x i m a t e l y 62 w t % of P N L - 7 6 - 6 8 glass consisted of ( N a 0 + 2

+

Fe 0 2

3

S i 0 ) , so i t w a s n o t s u r p r i s i n g to find t h a t t h e m a j o r c r y s t a l l i n e phases 2

i n t h e 1 0 : 1 w a t e r - t o - s o l i d - r a t i o experiments w e r e N a - F e - r i c h Note that nearly half the available N a was observed

pyroxenes.

i n the product

solutions. W h e n t h e a m o u n t of w a t e r w a s t r i p l e d , t h e N a i n s o l u t i o n i n c r e a s e d to as m u c h as 6 7 % i n t h e 4-week r u n , w h i l e t h e a m o u n t of


386

SOLID S T A T E

pyroxenes

CHEMISTRY: A

i n the s o l i d p r o d u c t s

c o n s t i t u e n t of these h i g h - F e

3 +

decreased.


A p p a r e n t l y N a is a

key

pyroxenes, a n d w i t h m o r e N a g o i n g i n t o

s o l u t i o n , less w a s a v a i l a b l e to f o r m the pyroxenes.

T h i s t r e n d suggests

that w h e n w a t e r - t o - s o l i d ratios are less t h a n 1 0 : 1 , less N a w o u l d go i n t o t h e solutions a n d the f o r m a t i o n of c r y s t a l l i n e p y r o x e n e s i n t h e a l t e r e d p r o d u c t s w o u l d b e greater. B o r o n is a p p a r e n t l y extracted f r o m t h e glass as o n e or m o r e species of borate ions a n d m o l y b d e n u m as t h e m o l y b d a t e i o n . W h e n the solutions


e x t r a c t e d f r o m P N L - 7 6 - 6 8 glass are a l l o w e d to evaporate to dryness at room temperature, S E M / E D X a n d X - r a y diffraction characterization of the r e s i d u a l solids r e v e a l e d t h e p r e s e n c e of a h y d r a t e d s o d i u m m o l y b d a t e a n d the borate m i n e r a l t i n c a l c o n i t e , N a B 0 2

4

7

•5H 0

(13).

2

T h e o c c u r r e n c e of the other major constituent of t h e glass, F e , w a s almost c o m p l e t e l y confined to t h e s o l i d p r o d u c t s . p y r o x e n e , N C S , a n d s p i n e l phases.

It was found i n the

A s u b s t a n t i a l p o r t i o n of t h e o r i g i n a l

s p i n e l c r y s t a l l i n e i n c l u s i o n s i n t e r a c t e d w i t h t h e h y d r o t h e r m a l solutions. M u c h of t h e F e content of t h e glass o r i g i n a l l y present i n these i n c l u s i o n s w a s r e c r y s t a l l i z e d i n t h e p y r o x e n e phases.

This mechanism may

also

a c c o u n t for t h e l a r g e a m o u n t s of C r i n s o l u t i o n . C h r o m i u m occurs w i t h F e i n the spinels. W h e n the s p i n e l is a l t e r e d a n d F e is r e c r y s t a l l i z e d i n the pyroxenes, the C r m i g h t r e m a i n b e h i n d i n s o l u t i o n . The

preceding

discussion

illustrates t h a t w i t h

the

multiple-tool

c h a r a c t e r i z a t i o n u s e d i n this s t u d y , i t is p o s s i b l e to d e s c r i b e a l t e r a t i o n of this c o m p l e x glass i n near-mass-balance d e t a i l f o r m a n y of its elements. Glass Crystallization and Repository Design.

S o l u t i o n and r e c r y s -

t a l l i z a t i o n of the p r o t o t y p e r a d w a s t e glass takes p l a c e so r e a d i l y t h a t some c o g n i z a n c e of t h e p o t e n t i a l f o r this effect m u s t b e t a k e n d u r i n g the r e p o s i t o r y d e s i g n . B e c a u s e m a n y of the o b s e r v e d reactions r e q u i r e o n l y w a t e r as a catalyst, some of the r e c r y s t a l l i z a t i o n a n d t r a n s p o r t c o u l d b e e x p e c t e d i n the p r e s e n c e of o n l y s m a l l a m o u n t s of w a t e r . O n e c a n either v i e w the h y d r o t h e r m a l reactions as a p r o b l e m i n n e e d of a s o l u t i o n , or one c a n s i m p l y i n c o r p o r a t e the p o t e n t i a l for h y d r o t h e r m a l reactions as p a r t of the o v e r a l l w a s t e storage

concept.

T h e r e are some f a i r l y

obvious

e n g i n e e r i n g solutions to the p r o b l e m a n d also some p o t e n t i a l l y i n t e r e s t i n g w a y s o f i n c o r p o r a t i n g the reactions as a p o s i t i v e benefit, a l t h o u g h d a t a are too sparse at present to m a k e d e f i n i t i v e statements a b o u t the latter. F i r s t , a n o b v i o u s r e q u i r e m e n t for h y d r o t h e r m a l c o n d i t i o n s is a c e r t a i n a m o u n t of heat.

T h e heat o u t p u t of the canisters c a n b e a d j u s t e d

by

a d j u s t i n g the w a s t e l o a d i n g . L o a d i n g s c o u l d b e a d j u s t e d d o w n w a r d u n t i l t h e s k i n t e m p e r a t u r e of t h e canister w a s b e l o w the t e m p e r a t u r e at w h i c h the reactions w o u l d b e a p r o b l e m .

T h e cost of t h i s a p p r o a c h to

the

p r o b l e m is that m u c h l a r g e r v o l u m e s of m a t e r i a l w o u l d b e c r e a t e d f o r the d i s p o s a l of a g i v e n v o l u m e of w a s t e .


19.

MCCARTHY

ET AL.

Simulated

Radioactive

Waste

387

Glass

S e c o n d , i t m a y b e r e m e m b e r e d that h e a t comes f r o m t h e d e c a y of m o s t l y s h o r t - l i v e d isotopes. T h e t h e r m a l p e r i o d of t h e r e p o s i t o r y is short, a f e w h u n d r e d years at most. O n e e x p e d i e n t is to r e t a i n t h e canisters i n c o n t r o l l e d a n d c o o l e d surface storage f o r a f e w tens of years

before

r e m o v a l of t h e m a t e r i a l to t h e repository. T e m p e r a t u r e s f a l l r a p i d l y w i t h t i m e o u t of t h e reactor, a n d e v e n a f e w years of storage i m p r o v e s t h e t h e r m a l heat o u t p u t greatly. A l t e r n a t i v e l y , t h e canister d e s i g n c o u l d b e i m p r o v e d i n s u c h a w a y that b r e a c h i n g of t h e canister d u r i n g t h e t h e r m a l


period became unlikely. A c o m p l e t e l y different a p p r o a c h is t o e x a m i n e t h e i m p l i c a t i o n s o f w a s t e , r o c k , a n d w a t e r as a c h e m i c a l system ( 2 ) . T h e results r e p o r t e d i n this p a p e r d e a l t w i t h a glass w a s t e f o r m i n a c l o s e d system i n the p r e s e n c e of w a t e r o n l y . T h i s s i t u a t i o n w o u l d s u r e l y o b t a i n i f i n v a d i n g w a t e r s c a m e i n t o contact w i t h t h e surface o f t h e glass i n g o t o r p e n e t r a t e d i n t o cracks a n d flaws i n t h e m a t e r i a l . T h e i n i t i a l c h e m i c a l reactions w o u l d b e c o m pletely dominated b y the composition

of t h e glass.

A s t h e solutions

c a r r y i n g d i s s o l v e d species o r t h e s o l i d r e a c t i o n p r o d u c t s themselves c a m e i n t o contact w i t h t h e s u r r o u n d i n g r o c k o f t h e w a l l , t h e c h e m i s t r y w o u l d c o m e to b e d o m i n a t e d b y t h e r o c k . I f the r o c k w e r e of basalt, g r a n i t e , o r shale, n e w reactions w o u l d take p l a c e t h a t w o u l d g r e a t l y m o d i f y t h e final p h a s e assemblage.

I t is t h e final assemblage, w h e n t h e w a s t e has c o m e

i n t o steady state c o n d i t i o n s w i t h t h e r o c k , that m u s t b e r e g a r d e d as t h e source t e r m f o r f u r t h e r t r a n s p o r t a n d d i s p e r s a l of t h e w a s t e elements b y s l o w processes o v e r t h e f u n c t i o n a l l i f e of t h e r e p o s i t o r y ( 2 ) . T h e p a r a graphs b e l o w o u t l i n e some of t h e p o s s i b i l i t i e s b a s e d o n n e w b u t n o t final e x p e r i m e n t a l results f r o m c u r r e n t w a s t e r o c k i n t e r a c t i o n studies at P e n n s y l v a n i a State U n i v e r s i t y

(11,13).

STRONTIUM AND LANTHANEDES.

M u c h of t h e S r a n d L n i n t h e

glass w a s f o u n d w i t h t h e N C S a l t e r a t i o n p r o d u c t s .

original

Equilibration with

h y d r o t h e r m a l solutions c o u l d w e l l result i n c r y s t a l l i z a t i o n of apatite phases s i m i l a r to that i d e n t i f i e d as one of t h e s k i n phases. A p a t i t e s are a c o m m o n accessory m i n e r a l i n basalts a n d other igneous rocks a n d , o n c e f o r m e d , t h e y m a y r e m a i n i n , or close t o , t h e r m o d y n a m i c s t a b i l i t y w i t h t h e r o c k t h r o u g h o u t t h e t h e r m a l p e r i o d . M i x e d p h o s p h a t e - s i l i c a t e apatites of C a , Sr, L n , a n d U ( b r i t h o l i t e ) , s u c h as those f o r m e d o n t h e p r o d u c t s k i n , are k n o w n . URANIUM.

S m a l l amounts of t h e U i n P N L - 7 6 - 6 8 c r y s t a l l i z e d i n t h e

a p a t i t e phase as has a l r e a d y b e e n n o t e d . c r y s t a l l i n e host f o r U w a s w e e k s i t e .

T h e other w e l l - c h a r a c t e r i z e d

U r a n i u m i n w e e k s i t e is i n t h e

h e x a v a l e n t state. H o s t rocks c o n t a i n i n g F e , sulfides, a n d o r g a n i c m a t e + +

rials w o u l d buffer t h e o x y g e n a c t i v i t y w e l l i n t o t h e r e d u c i n g r a n g e w h e r e the U

6

+

w o u l d n o t b e stable. I n one o f a series of experiments d e s i g n e d

to e x p l o r e

this s t a b i l i t y q u e s t i o n , t h e authors h a v e t r e a t e d


weeksite

388

SOLID S T A T E


crystals g a t h e r e d f r o m glass a l t e r a t i o n p r o d u c t w i t h H G W i n contact w i t h a s i x t y f o l d excess b y w e i g h t of c r u s h e d C o l u m b i a R i v e r basalt.

The

water-to-solids r a t i o w a s 3 0 : 1 , a n d the e x p e r i m e n t a l c o n d i t i o n s

were

3 0 0 ° C , 300 b a r , a n d 4 w e e k s .

T h e r e s u l t a n t crystals h a d t u r n e d b l a c k

a n d gave a n X - r a y p o w d e r p a t t e r n of u r a n i n i t e , U 0 p a r a m e t e r t y p i c a l of a c o m p o s i t i o n near U 0 . 2

2 5

2 + a ?

, with a cubic cell

. A s l o n g as t h e c o n d i t i o n s

r e m a i n r e d u c i n g , u r a n i n i t e s h o u l d r e m a i n a stable a n d i n s o l u b l e p h a s e (14).

It is p o s s i b l e t h a t the U i n the N C S a l t e r a t i o n zones w o u l d

be


c o n v e r t e d to u r a n i n i t e t h r o u g h l o n g - t e r m e q u i l i b r a t i o n w i t h b a s a l t - s a t u r a t e d h y d r o t h e r m a l solutions. CESIUM.

T h i s element w a s o b s e r v e d i n a l t e r a t i o n p r o d u c t solutions,

i n w e e k s i t e , a n d i n v a r i o u s N C S a l t e r a t i o n zones.

( N o t e that the C s

w o u l d b e released f r o m w e e k s i t e b y the d e c o m p o s i t i o n m e c h a n i s m just d e s c r i b e d . ) T h e authors h a v e c o m p l e t e d n u m e r o u s experiments i n w h i c h solutions c o n t a i n i n g C s w e r e r e a c t e d w i t h C o l u m b i a R i v e r basalts, w i t h i n d i v i d u a l basalt phases, a n d w i t h shales a n d constituent c l a y m i n e r a l s (14).

U n d e r c o n d i t i o n s of 2 0 0 ° - 3 0 0 ° C a n d 300 b a r , v i r t u a l l y a l l the C s

w a s r e m o v e d f r o m the solutions. Intense reflections analogous to those of the m i n e r a l p o l l u c i t e , ( C s , N a ) A l S i O • n H 0 , w e r e present i n X - r a y 2

diffractograms

e

of m a n y r e a c t i o n p r o d u c t s .

2

P o l l u c i t e occurs i n h y d r o -

t h e r m a l l y f o r m e d pegmatites a n d m a y b e stable i n contact w i t h basalt a n d shale u n d e r h y d r o t h e r m a l c o n d i t i o n s .

R e s u l t s to date i n d i c a t e t h a t

C s w o u l d react w i t h a l u m i n o - s i l i c a t e m i n e r a l s a n d b e c o m e i m m o b i l i z e d as p o l l u c i t e .

Glossary of Symbols AAS =

atomic absorption

AES =

a t o m i c e m i s s i o n spectrometer

spectrophotometry

d = interplanar spacing ( i n X - r a y data) DW

deionized water

EBS =

electron backscatter

EDX = HGW = I = Ln = NCS =

energy-dispersive X - r a y spectrometry H a n f o r d groundwater intensity ( i n X - r a y data) lanthanides n o n c r y s t a l l i n e solids

P D F = Powder Diffraction File PNL =

P a c i f i c N o r t h w e s t L a b o r a t o r i e s of B a t t e l l e M e m o r i a l I n s t i t u t e

P-T =

pressure-temperature

SEI =

secondary electron image

S E M — scanning electron microscopy


19.

MCCARTHY

ET AL.

Simulated

Radioactive

Waste

Glass

389

ss = s o l i d s o l u t i o n T D S = t o t a l d i s s o l v e d solids r a d waste = radioactive waste Acknowledgments T h i s r e s e a r c h is s u p p o r t e d b y t h e U . S . D e p a r t m e n t of E n e r g y t h r o u g h R o c k w e l l H a n f o r d O p e r a t i o n s a n d t h e Office of N u c l e a r W a s t e I s o l a t i o n . J . E . M e n d e l p r o v i d e d t h e s p e c i m e n of P N L - 7 6 - 6 8 .

C . A . S m i t h assisted


w i t h the hydrothermal experimentation.

Literature Cited 1. Goodenough, J. B.; Whittingham, M . S., Eds.; In "Solid State Chemistry of Energy Conversion and Storage," Adv. Chem. Ser. 1977, 163. 2. McCarthy, G. J.; White, W . B.; Roy, R.; Scheetz, B. E . ; Komarneni, S.; Smith, D . K.; Roy, D . M. "Interactions Between Nuclear Waste and Surrounding Rock," Nature 1978, 273, 217-219. 3. Jenks, G. J. "NWTS Program Conference on Waste-Rock Interactions"; Y/OWI/SUB-77/14268; Roy, D . M . , Ed.; Pennsylvania State University: University Park, PA, July 1977; 5-17. 4. Mendel, J. E.; McElroy, J. L.; Platt, A . M . In "High-Level Radioactive Waste Management," Adv. Chem. Ser. 1976, 153, 93-107. 5. Mendel, J. E.; Ross, W . A.; Roberts, F . P. "Annual Report on the Charac teristics of High-Level Waste Glasses"; BNWL-2252; Battelle Pacific Northwest Laboratories: Richland, W A , 1977. 6. McElroy, J. L . "Quarterly Progress Report, Research and Development Activities, Waste Fixation Program"; PNL-2264; Battelle Pacific North west Laboratory: Richland, W A , 1977. 7. Ross, W . A.; Bradley, D . J.; Bunnell, L . R. "Annual Report on the Charac terization of High-Level Waste Glasses"; PNL-2625; Battelle Pacific Northwest Laboratory: Richland, W A , 1978. 8. Roy, R.; Tuttle, O. F. In "Physics and Chemistry of the Earth"; Pergamon: New York, 1956; Vol. 1, 138-180. 9. Gandolfi, G . "Discussions Upon Methods to Obtain X-Ray Powder Pat terns from a Single Crystal," Mineral. Petrogr. Acta 1967, 13, 67. 10. "Powder Diffraction File"; McClune, W . F., E d . ; JCPDS, (International Centre for Diffraction Data): Swarthmore, PA. 11. McCarthy, G. J.; Scheetz, B . E . ; Komarneni, S. "Simulated High-Level Waste-Basalt Interaction Experiments—First Interim Progress"; Rock well Hanford Operations Report; University Park, PA, March 1978. 12. Outerbridge, W . F . ; Staatz, M . H.; Meyrowitz, R. "Weeksite, a New Uranium Mineral from the Thomas Range, Juab County Utah;" Am. Mineral. 1960, 45, 39-52. 13. McCarthy, G . J.; Scheetz, B . E.; Komarneni, S.; Barnes, M . W . ; Smith, C. A . ; Smith, D . K.; Lewis, J. F . "Simulated High-Level Waste-Basalt Interaction Experiments. Second Interim Progress Report"; Rockwell Hanford Operations Report; University Park, PA, June 1978. 14. McCarthy, G. J.; Komarneni, S.; Scheetz, B. E.; White, W . B . In "Scien tific Basis for Nuclear Waste Management," McCarthy, G. J., E d . ; Plenum: 1979; Vol. 1, 329-340. RECEIVED November 6, 1978.


Solid State Chemistry: A Contemporary Overview - American

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