Environmental Engineering Reference
In-Depth Information
TABLE 6.5.6
28-day MCC-1 Leach Rates (g/m
2
/day) of Two
HCs, Four Glasses, and a Hot-Isostatically Pressed
Glass Ceramic*
Material
Na
Cs
Sr
Al
Si
EA glass*
1.4
1.6
0.20
0.57
1.1
SRL-131*
1.1
0.89
0.14
0.50
0.86
WV-39-2*
4.7
5
2.0
3.85
3.8
JSSA*
0.39
0.1
0.27
0.18
0.31
ANLW glass ceramic*
0.39
0.39
0.14
0.57
0.14
HC#1
13
0.096
0.012
1.6
0.54
HC#2
15
0.07
0.024
0.72
0.75
* Glass and glass ceramic leach data taken from Reference 15.
than does an equal-sized piece of glass. This means that a glass may out-perform
the HC in short-duration leach tests even if the former is intrinsically much more
water soluble. At the end of a 7-day PCT, the composition of the leachant exposed
to powdered HC represents steady-state (saturation). In contrast, the leach rate of
EA glass at that time is rapidly increasing (EA glass dissolution is autocatalytic
under PCT conditions). If EA glass were to be ground to a size that presents as
much BET surface to a leachant as does < 150-μm HC powder, it would totally
decompose (dissolve) within 1 hour under PCT leach conditions.
6.5.4.2.4 ANSI/ANS-16.1-2003
Table 6.5.7 gives the results of an ANSI/ANS-16.1-2003 leach test
16
performed on
one of the HC specimens (HC#1) described above. The goal of the ANSI/ANS-16.1-
2003 is to determine the mobility of individual constituents
within
the sample. A
small monolithic specimen of known composition and surface area is repeatedly
leached with a relatively large volume of fresh deionized water. The fractions of key
sample constituents in the resulting leachates are combined with the specimen's
physical size and the leach times to generate effective diffusion coefficients (D, in
TABLE 6.5.7
ANSI/ANS-16.1-2003 HC Leachability Indices
Time
(hrs)
Na
Cs
Zr
Sr
NO
3
-
Leachability Index
9.9
13.7
> 15.4
14.3
10.4
Total wt% leached
8.26
< 0.0099
< 0.0025
0.015
10.5
</> values are based upon the detection capabilities of the analytical
instrumentation: ICPAES for all metals except Cs, graphite furnace AAS
for Cs, and ion chromatography for nitrate.
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