Environmental Engineering Reference
In-Depth Information
demonstrated.high.Cs.distribution.coeficients.in.acidic,.alkaline,.and.neu-
tral.solution.despite.the.presence.of.a.high.concentration.of.completive.ions.
such.as.Na
+
.and.K
+
.(Yu.et.al..2002).
The.alpha.particle.is.the.injected.ion.in.the.simulation.(Saling.and.Fentiman.
2002)..In.the.simulation,.10,000.ions.are.injected.into.the.four.targets..The.ion.
beam.energy.is.2.MeV..For.susceptibility,.it.is.suggested.that.following.equa-
tion.be.used.(Andersson.1998):
(
)
1 1
-16
.
dpa
=
×
0
N D
d
·
ρ
.
(2.1)
c
n
where
N
d
..
=.Target.displacement.(displacement/ion/Å).
D
c
..
=.Critical.dose.(ions/cm
2
).
ρ
n
..
=.Atomic.density.of.the.target.material.(atoms/Å
3
).
This.is.used.for.the.calculation.of.
D
c
.(critical.dose,.ions/cm
2
),.which.is.related.
to.the.susceptibility.of.the.waste.form.
2.3 Results
The. critical. doses. are. the. main. results. of. the. simulation. and. are. shown. in.
Table 2.1,.which.is.obtained.using.Equation.(2.1)..The.nontronite.of.smectite.
has.the.highest.value..The.highest.deposition.is.around.300.nm..Figure 2.1.
shows.the.Z-axis.view.of.He
+2
.ion.injection.for.muscovite.and.the.simpliied.
coniguration.of.the.nuclear.waste.drum.(A.=.crystalline.silicotitanate.layer,.
B.=.concrete.layer)..For.the.ion.beam.distribution,.the.highest.point.for.the.
critical.dose.is.at.300.nm..Crystalline.silicotitanate.has.a.higher.value.for.stop-
ping.power.of.most.regions.among.the.four.forms.in.Figure 2.2..According.
to.Figure 2.3,.the.energy.loss.of.stopping.power.changes.in.204.nm.for.non-
tronite. and. crystalline. silicotitanate.. The. nontronite. has. the. lowest. energy.
loss.in.300.and.400.nm..After.calculating.the.comparisons.between.the.two.
TABLE 2.1
Critical.Dose
WasteForm
Critical
Dose
(ions/cm
2
)
:
D
c
Sheet.silicate.(mica).:.muscovite
18.4438.×.10
−4
Zeolite.:.analcim
146.9250.×.10
−4
Smectite.:.nontronite
217.5820.×.10
−4
Crystalline.:.silicotitanate
28.8761.×.10
−4
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