Neutron and β/γ radiolysis of water up to supercritical conditions. 2. SF6 as a scavenger for hydrated electron

Article abstract of DOI:10.1021/jp1025366

SF₆ has been used as a specific scavenger to investigate the β/γ radiolysis yield of hydrated electrons in pressurized high temperature sub- and supercritical water. SF₆ is thermally stable in supercritical water, and each scavenging reaction is known to produce six fluoride ions, which can be readily measured using a fluoride-selective electrode. Problems in the application of this method are described, including buildup of acid product and chain reduction of SF₆ in the presence of organic ^·H and ^·OH radical scavengers. Ultimately we find that the combination of SF₆ and phenol in neutral solution gives reliable results in supercritical water, because the protons and fluoride ions remain associated as HF molecules. The β/γ yields in supercritical water are similar to previous measurements using N₂O scavenger.

Full text of DOI:10.1021/jp1025366

J. Phys. Chem. A 2010, 114, 7479–7484
7479
Neutron and ꢀ/γ Radiolysis of Water up to Supercritical Conditions. 2. SF as a Scavenger
6
for Hydrated Electron
Kyle Haygarth and David M. Bartels*
Radiation Laboratory, UniVersity of Notre Dame, Notre Dame, Indiana 46556
ReceiVed: March 20, 2010; ReVised Manuscript ReceiVed: June 11, 2010
SF
6
has been used as a specific scavenger to investigate the ꢀ/γ radiolysis yield of hydrated electrons in
is thermally stable in supercritical water, and
pressurized high temperature sub- and supercritical water. SF
6
each scavenging reaction is known to produce six fluoride ions, which can be readily measured using a fluoride-
selective electrode. Problems in the application of this method are described, including buildup of acid product
•
•
and chain reduction of SF
the combination of SF and phenol in neutral solution gives reliable results in supercritical water, because the
protons and fluoride ions remain associated as HF molecules. The ꢀ/γ yields in supercritical water are similar
to previous measurements using N O scavenger.
6
in the presence of organic H and OH radical scavengers. Ultimately we find that
6
2
I. Introduction
possible to subtract this thermal component from the radiolytic
yield because the dwell time is quite shortson the order of 1 s.
This is not the case for the reactor flow loop, and the much
The radiation-induced breakdown of high temperature water
is an important topic in understanding corrosion of structural
components in existing nuclear power plants and in predicting
corrosion in potentially more efficient reactors operating with
8
longer dwell time poses a serious problem for the use of N
in that system at supercritical temperatures.
2
O
To overcome this problem we explored the use of SF
6
as a
1-5
6
supercritical water coolant. In part 1 of this series, measure-
specific scavenger for the hydrated electron. SF is thermally
6
•
2
ments of H , H atom, and solvated electron yields were
stable at the supercritical temperatures, and is known to react
presented for the radiolysis of pressurized high temperature
water using ꢀ/γ radiation generated with a van de Graaff
accelerator. An extensive series of measurements were made
vs temperature up to 400 °C on a 250 bar isobar, and two series
were measured vs density (pressure) for constant temperatures
of 380 and 400 °C. (The original report was corrected for a
-
with (e )aq and then hydrolyze, producing six fluoride ions for
every electron:9
-
•
-
(e ) + SF f SF + F
(4a)
aq
6
5
7
small pressure measurement error in a recent erratum. ) These
•
-
+
-
•
measurements are complementary to similar measurements made
SF + 4H O f HSO + 6H + 5F + OH
5 2 3
8
in a flow loop at the University of Wisconsin reactor facility,
(4b)
which will be described in part 3 of this series. The comple-
mentary measurements allow separation of radiolysis effects due
to ꢀ/γ radiation from those due to neutron radiation.
The fluoride can be conveniently measured with a fluoride-
selective electrode. A problem with the SF scavenger is that
the acid produced can build up and kinetically compete with
6
In part 1, hydrated electron yields were determined by the
-
reaction of hydrated electrons (e )aq with the scavenger N
2
O,
-
6
the SF , leading to an incorrect (low) yield result for (e )aq. A
2
which gives the easily measured stable product N :
simple remedy is to add a small amount of KOH to neutralize
•
the acid. Phenol is added as well to prevent H atom contribution
-
•
-
(
e ) + N O f N + OH + OH
(1)
to the result.
aq
2
2
As we describe below, this system works well in subcritical
water. In supercritical water, very strange results were recorded,
which have now been understood in terms of a chain reduction
of SF in alkaline phenol solutions. Surprisingly, good results
6
are obtained in neutral phenol solutions.
•
Phenol was added to the water to scavenge H atoms, some of
which could otherwise convert to solvated electrons (equilibrium
2
reaction 3) and contribute to the observed N yield.
•
•
II. Experimental Section
PhOH + H f HPhOH
(2)
(3)
The flow system used in these experiments is identical to
the apparatus used in part 1. Briefly, using a pair of HPLC
6
•
-
-
H + OH S (e ) + H O
aq
2
pumps, water is pumped at 6 mL/min through a preheater and
then into a titanium or Hastelloy 276 tube of ca. 2 mm i.d. in
front of a beam port of a 3 MeV van de Graaff electron
accelerator. The dwell time of the water in the irradiation zone
is approximately 0.6 s. The water then is cooled to room
temperature, and pressure is dropped through a small-diameter
capillary. The water travels approximately 15 m from the
2
It was found that N O decomposes to some extent on the hot
metal walls of the flow system at 380 and 400 °C, but it was
*
To whom correspondence should be addressed. Telephone: (574) 631-
561. Fax: (574) 631-8068. E-mail: bartels.5@nd.edu.
5
1
0.1021/jp1025366  2010 American Chemical Society
Published on Web 06/24/2010

7
480 J. Phys. Chem. A, Vol. 114, No. 28, 2010
Haygarth and Bartels
Figure 1. Fluoride production vs dose as a function of temperature in
-
4
alkaline solutions of SF
SF
multiplying by the density, 0.45 g/cm .) At room temperature slightly
6
(0.01 m phenol/0.001 m KOH/2.5 × 10
m
Figure 2. Survey of fluoride production for several KOH and phenol
-
4
). (For clarity, the 380 °C dose has not been normalized by
concentrations (2.5 × 10 m SF
6
) as a function of density at 380 °C.
6
3
-
The G value indicated is fluoride yield divided by 6, to give the (e )aq
yield. Neutral solutions of 0.01 m phenol agree reasonably well with
-
nonlinear production of F is found in neutral solution due to acid
6
,7
product buildup, but in alkaline solution the signal is linear. In alkaline
supercritical water the data appear to be linear (cf. the dashed line),
but the intercept is nonzero. The solid line fit is explained in the text.
work conducted by Janik et al.
from the accelerator. In neutral solution the dose response is
slightly nonlinear, as predicted, due to acid buildup. In 0.001
m KOH solution the fluoride generated is a linear function of
the dose (or dose rate), with zero intercept. Similar behavior is
found up to 300 °C. At 380 °C, the fluoride concentration in
irradiation vault to the control room for analysis. Rather than
collecting 12 mL of solution for gas sparging and mass
spectrometry analysis as in part 1, 50 mL of solution was
collected in a small beaker for testing with an Accumet fluoride-
sensitive electrode. A pH and ionic strength buffer tablet
supplied by the manufacturer was added to each beaker, and
0
.001 m KOH appears to be a linear function of dose in the
range examined, but the (dashed line) intercept is significantly
larger than zero. A blank run with no dose gave no fluoride
signal. Indeed, we have never observed breakdown of SF in
6
the absence of radiation. (This zero dose point is omitted from
the linear least squares fit here and in the figures discussed
the SF
6
was briefly sparged from each sample to avoid poisoning
. The electrode voltage was
of the electrode surface by the SF
6
below.)
measured to 0.05 mV precision with a differential voltmeter.
With careful measurement practice we are able to obtain ca.
A survey of (apparent) (e-)aq yield vs density in supercritical
water at 380 °C is displayed in Figure 2 for a constant dose of
2
% precision in repeated measurements of any sample greater
approximately 50 Gy/s. Contrary to expectation, in neutral
than 10 µM concentration.
-
solutions of phenol, G((e )aq) is nearly equal to the N
2
O result
The continuous electron beam at this accelerator port is poorly
focused and varies significantly from day to day. A fiber optic
is strung in front of the flow tubing to intercept a small
representative fraction of the radiation. Fluorescence and
Cerenkov light generated in the fiber is proportional to the dose
delivered to the sample. Each day the fluoride concentration
generated at room temperature (20 °C) is measured to calibrate
from part 1: hydrofluoric acid product buildup appears to be
no factor. Also contrary to expectation, in the presence of 0.002
-
m KOH, the (e )aq yield is 3-5 times larger than in neutral
solution. (According to the conductivity measurements of Ho
10
et al., KOH is still fully dissociated up to this concentration.)
•
Possibly some of this additional yield could come from H atom
-
•
conversion to (e )aq, if phenol were a poor scavenger for H
atoms at this temperature. We reduced the concentration of the
phenol scavenger from 0.01 m to 0.002 m with little effect
the light signal from the fiber. In SF
6
saturated solution
containing 0.01 m phenol and 0.001 m KOH, we take the
-
7
(
scavenged) electron yield to be 2.60 × 10 mol/J in order to
(
Figure 2). This shows that more than enough phenol is present
deduce the actual dose corresponding to a given integrated light
intensity. Typical room temperature dose rates generated in this
experiment run in the range 10-100 Gy/s. At other temperatures
and pressures we assume the absorbed dose is proportional to
the water density.
•
to scavenge the H atoms. A reduction of phenol concentration
to 0.0005 m finally led to an increase in the fluoride yield, which
-
we ascribe to this H S (e )aq conversion. By omitting phenol
•
-
entirely, all H atoms should convert to (e )aq and the yield is
-
•
in principle due to the sum of (e )aq and H atom yields. The
yields found in Figure 2 are larger than the combined G((e )aq
and G(H) yields found in part 1. However, it has since been
found that the H atom yield is underestimated in this previous
-
)
III. Results
6
•
Figure 1 compares fluoride concentrations generated vs total
dose in SF
6
saturated solutions of 0.01 m phenol, for room
work.1
temperature and for 380 °C at 250 bar pressure. The dwell time
is fixed, so total dose is changed via changing the dose rate
More careful measurement of fluoride yield vs unnormalized
dose in neutral pH phenol solution is shown in Figure 3 for

SF6 as a Scavenger for Hydrated Electron
J. Phys. Chem. A, Vol. 114, No. 28, 2010 7481
-
TABLE 1: G((e )aq) in Supercritical Water Phenol (0.01
-3
m)/SF
6
(2.5 × 10 m) Solutions
80 °C
10-7G((e-)aq
3
400 °C
10-7G((e-)aq
density
)
density
(kg/dm )
)
3
3
(
kg/dm )
(mol/J)
(mol/J)
0
0
0
0
0
0
0
0
0
0
0
0
.529
.501
.469
.451
.400
.350
.347
.300
.250
.200
.159
.150
2.36
2.10
1.76
1.19
0.80
1.22
1.01
1.26
1.29
1.23
1.62
1.61
0.318 8
0.252 7
0.212 69
0.185 81
0.163 16
0.138 14
0.106 86
-
1.62
1.34
1.42
1.49
1.65
1.80
2.06
-
-
-
-
-
-
-
-
-
Based on the scatter observed, these yields based on SF
6
are
probably uncertain by 20-30% in supercritical water. At 380
°
C, the SF
6
scavenging yields appear slightly lower on average
than the N
2
4
O result, possibly because the scavenging power of
-
-3
2
.5 × 10 m SF
6
is less than that of 2.5 × 10 m N
2
O.
Figure 3. Fluoride production vs (unnormalized) dose in neutral phenol
-
4
The success of the neutral solution scavenging in supercritical
water can be rationalized in terms of the large shift in pK that
all acids exhibit on going from room temperature water to
supercritical water. For example, the pK of HCl near room
temperature is -7, whereas in 380 °C supercritical water, the
solutions at 380 °C (0.01 m phenol/2.5 × 10 m SF
6
). A zero intercept
is visible, indicating no chain reactions are occurring.
a
a
is greater than 3.1
1,12
Similar behavior is known for all
pK
a
acids.13 The room temperature pK
of HF is already 3.5, and
14
a
it can also be expected to shift many pK units in the transition
to supercritical water. Therefore, in our supercritical water
experiment the species present in the irradiation zone is the
+
-
hydrofluoric acid molecule, not separated H and F ions. The
-
reaction of (e )aq with HF molecule is much slower than that
with hydrated proton even at room temperature. In earlier work
we found a very large rate constant decrease for the reaction of
15
-
16
(
e )aq with perchloric acid in supercritical water compared to
Figure 4. Fluoride production vs (unnormalized) dose in alkaline
-
4
phenol solutions at 380 °C (0.01 m phenol/2.5 × 10 m SF
6
/0.002 m
KOH). As opposed to the neutral case, a nonzero intercept is visible,
indicating substantial chain reactions are occurring.
several densities at 380 °C, and in Figure 4 similar data are
shown for alkaline solutions. (For clarity of display the dose
has not been normalized for density.) The neutral solutions of
Figure 3 exhibit very linear behavior with zero intercept. The
alkaline solutions all exhibit the “nonzero intercept”, which
indicates some unanticipated dose-rate-dependent process in the
chemistry. (The zero-dose blank experiment gives a zero fluoride
-
-
result.) In Table 1 we list the (e )aq yields (i.e., G(F )/6) in the
neutral solutions at 380 and 400 °C. In Figure 5 these yields
-
are compared with the (e )aq yields found for neutral N
2
O
-
Figure 5. Radiation yields of the solvated electron, (e )aq, during
6
solutions in part 1. (Small errors in the pressure measurement
of part 1 have been reported in a recent erratum, and corrected
N O yields are used in Figure 5.) The results are very similar.
2
-4
radiolysis of 0.01 m phenol/2.5 × 10 m SF
6
neutral solution compared
7
6
,7
-3
to work by Janik et al. (0.01 m phenol/2.5 × 10 m N
2
O solution)
as a function of density at 380 and 400 °C.

7
482 J. Phys. Chem. A, Vol. 114, No. 28, 2010
Haygarth and Bartels
Figure 7. Fluoride production vs (unnormalized) dose in alkaline
Figure 6. Fluoride production vs (unnormalized) dose in neutral
-4
-
4
methanol solutions at 380 °C (0.01 m methanol/2.5 × 10 m SF
.001 m KOH). A nonzero intercept is visible, indicating a chain
reaction.
6
/
methanol solutions at 380 °C (0.01 m methanol/2.5 × 10 m SF
6
). A
0
nonzero intercept is visible, indicating a chain reaction.
subcritical temperatures (e.g., the rate constant is 2 × 10 M-1
12
•
•
centered radicals formed from OH and H reaction with
-
1
11
-1 -1
•
s
at 350 °C but reduced to 2 × 10
M
s
at 380 °C, 250
methanol (reaction 5) may reduce SF
radical (reaction 6).
6
, giving initially an SF
5
bar). It was ascribed to the same phenomenon; i.e., if perchloric
acid is associated, even in the form of ion pairs, the coulomb
-
+
attraction between (e )aq and (H )aq is greatly attenuated and
the reaction rate is reduced.
Then how can we understand the results of SF scavenging
6
in alkaline supercritical water? One possibility which concerned
us is that radiation deposited in the titanium flow tubing might
•
•
•
H, OH + CH OH f CH OH + H , H O
(5)
(6)
3
2
2
2
•
•
CH OH + SF f CH O + HF + SF
5
2
6
2
2
stimulate chemistry at the (TiO ) surface, and this process might
be sensitive to the pH and the dose rate. For a given length of
tubing with inner diameter of 2r, the near surface volume scales
as 2πr times an effective surface thickness, while the total
•
Hydrolysis of this radical is known to give an OH radical in
•
reaction 4b. The OH radical can then react with methanol,
completing the chain for reduction of SF
reduction of N O by R-hydroxy radicals has been reported in
6
6
. A similar chain
2
solution volume scales as πr . If we generously assume the
2
effective thickness at the interface is as great as 1 µm, then for
17,18
the literature
and was encountered in our previous work.
-
3
1
.0 mm radius tubing the surface/volume ratio is 2.0 × 10 .
A simple qualitative model of the kinetics in our experiment
can be constructed by assuming plug flow of the solution through
a uniformly irradiated zone. In this model the irradiation of a given
volume “turns on” as the solution enters the zone, and “turns off”
as the solution exits. We postulate that the alcohol radical
The density of titanium dioxide is roughly 4 times that of water,
so we may expect roughly 4 times more energy deposition in
the interface, but even so, efficiency for production of F would
-
need to be several hundred times higher for a postulated surface
process to compete with the bulk chemistry. It should not be
possible to observe such a process in this experiment. Ultimately
we found similar behavior of alkaline solutions for both titanium
tubing and Hastelloy 276C. It seems very unlikely that both
oxide surfaces could be so active.
•
concentration quickly reaches a steady state [ R]ss, given by
•
d[ R]
•
•
2
)
0 ) δ(G( R)) - 2k [ R]
(7)
(8)
2
dt
•
It was decided to try 0.01 m methanol as the H atom
scavenger in case the phenol was causing the unexpected
chemistry. Fluoride production vs dose is plotted for several
densities at 380 °C in Figure 6 for neutral methanol solutions
and in Figure 7 for alkaline methanol solutions. With methanol
•
δ(G( R))
[•
R] )
ss
ꢀ
2k2
•
•
as scavenger of H and OH radicals, the intercept of the fluoride
production plot is nonzero both with and without the presence
of KOH.
where δ is the dose rate, 2k
2
is the second order recombination
rate of the alcohol radicals R, and G( R) corresponds to the yield
of all radicals (note that (e )aq and H atoms convert to OH and
then to alcohol radicals R via the postulated reactions 4a, 4b, and
5). The production of fluoride ions is then given by the desired
scavenging of hydrated electrons and by the additional chain
•
•
-
-
•
•
Large F yields and “nonzero intercept” in both neutral and
•
alkaline methanol solutions suggest that high pH is not
fundamentally responsible for the behavior. We are led to
conclude that a chain reaction is responsible for the unexpected
results. We postulate that at high temperature the carbon-
c
reaction (with rate constant k ):

SF6 as a Scavenger for Hydrated Electron
J. Phys. Chem. A, Vol. 114, No. 28, 2010 7483
d[F-]
dt
fast reaction of (H+)aq with either base or (e-)aq in the low
-
•
)
6δ(G(e ) ) + 6k [SF ][ R]
(9)
aq
c
6
ss
dielectric supercritical water solvent. This was already observed
in nanosecond radiolysis experiments at Argonne National
Laboratory, where the addition of 0.001 m KOH was used to
greatly extend the electron lifetime.23 Recent picosecond radi-
olysis measurements of hydrated electron in supercritical water
show that this recombination is indeed very fast in neutral water
spurs.24 Therefore, “the yield” of hydrated electrons (and H
atoms) inferred from scavenging experiments in supercritical
water is a very strong function of the pH and the scavenger
used.
Integrating over the time of flow through the irradiation zone, we
find a term proportional to the dose rate (the desired scavenging)
plus a term proportional to the square root of the dose rate (the
chain reaction). When plotted vs dose rate as in our experiment,
the fluoride production appears to be quite linear except at very
low dose, which accounts for the apparent “nonzero intercept”.
Turning now to the alkaline phenol solutions, a “linear plus
square root” function of dose is shown to fit the “nonzero
6
In our previous work, we noted the strong difference between
-
intercept” data in Figure 1 (solid line), using the G((e )aq) from
2
our N O scavenging yields and the methyl viologen scavenging
25
Table 1 for the linear term. (We have insufficient yield and rate
constant information to interpret the square root term, which
also shows 50% run-to-run variation, possibly due to the poorly
defined electron beam focus. The experiment was not designed
results from the University of Tokyo. While the two labora-
3
tories agreed at 380 °C near 0.5 g/cm , as the density decreased
the methyl viologen scavenging produced a much stronger
+
-7
increase in yield, reaching G(MV ) ) 5.1 × 10 mol/J at
•
3
-7
to investigate this phenomenon.) The scavenging of H atoms
0.2g/cm in comparison with G(N
2
) ) 1.8 × 10 mol/J from
•
and OH radicals by phenol will give the immediate free radical
2
N O. Despite careful scrutiny, we are unable to suggest any
•
•
adduct products HPhOH and HOPhOH, where we make no
distinction between ortho, meta, para, or ipso additions to the
particular flaw in the experiments at either laboratory which
might explain the discrepancy. It seems reasonable to think that
both laboratories are correct and the primary difference lies in
•
ring. The HPhOH adduct radical cannot be responsible for a
chain process because the OH radical formed from SF
hydrolysis must carry the chain. Moreover, product measure-
ments in γ radiolysis of phenol solution at high temperature
•
6 2
the chemistry. Both the SF and N O scavenging systems in
6
our work are entirely neutral. The scavenging rate constants
1
1
-1 -1
for both scavengers are approximately 2 × 10
M
s
and
1
9
23
show a large yield of benzene, which presumably comes from
depend somewhat on density as shown in previous work. The
scavenging power, or rate constant times scavenger concentra-
substitution of -H for -OH in the phenol ring and the effective
•
•
7
-1
8
-1
conversion of H radicals to OH radicals. Apparently the neutral
tion, is on the order of 10 s for SF
6 2
and 10 s for N O at
•
•
OH adduct radical HOPhOH cannot reduce SF
find no chain reaction in neutral solutions. At room temperature,
it is known that the pK
is reasonable to suggest that the weak acid can be neutralized
by KOH in supercritical water, giving HOPhO . If HOPhO
were to reduce SF , then we would have a simple explanation
6
, because we
the concentrations employed. The methyl viologen scavenger
2
+
used at the University of Tokyo is a dication, MV . Unfortu-
nately, its scavenging rate constant in supercritical water is not
•
20
a
of HOPhOH is approximately 9.6. It
1
2
reported, but the rate constant at 350 °C is greater than 10
•
-
•
-
-1 -1 25
M
s . One assumes that it is typically ion paired in the
low-dielectric supercritical water, but perhaps a large fraction
6
of the MV2 is only paired with one counterion, so that
+
6
for the effect of base in the phenol/SF scavenging system.
However, HOPhO- is known to dissociate within some
•
-
scavenging of (e )aq is very fast with the singly charged
-
16
12
-1 -1
nanoseconds at room temperature, producing OH and a neutral
scavenger. If the rate constant remains in the 10
M
s
phenoxyl radical.20 This probably happens even faster in
supercritical water. Phenoxyl radical itself is not a reducing
radical. In order for this chemistry to be responsible for the
-4
range or higher, then the scavenging power of 5 × 10
m
methyl viologen in the University of Tokyo experiment will be
greater than the scavenging power in our experiments, and
scavenging will occur at earlier time, perhaps competing
6
chain reduction of SF in alkaline solutions, it seems that a
product radical of the phenoxyl must be invoked.
Room temperature studies of the products for phenoxyl radical
recombination show that the initial product is dominated by
C-C coupling and the formation of dihydroxybiphenyls. In
relatively low-dose γ experiments, the subsequent reaction of
these products with phenoxyl radical becomes by far the most
probable recombination pathway. Thus there are many potential
polyaromatic radical products of phenoxyl recombination in
-
+
effectively with the charge recombination of (e )aq with (H )aq.
-
The University of Tokyo data may approach the (e )aq yields
at “time zero” in the spurs, whereas our experiments probe
something closer to an “escape yield”. The escape yields of all
radical species are important for applications such as modeling
2
1
1
of nuclear reactors cooled by supercritical water. Given the
-
+
fast recombination of (e )aq and (H )aq in supercritical water, it
may only be meaningful to report the sum of reducing radicals
-
•
alkaline solutions. One of them may be able to reduce SF
OH radical is actually known to be in equilibrium with the
HOPhOH adduct at supercritical temperatures. Thus an OH
6
. The
G((e )aq + H) for the escape yields in this application.
•
•
22
V. Summary
adduct to one of the product polyaromatic molecules might be
able to reduce SF . We are unable to identify a particular product
which is most likely to reduce SF , but the existence of such a
6
The use of SF as scavenger for hydrated electron is shown
6
to give reasonable “escape” yields in radiolysis of supercritical
water-phenol solutions at neutral pH. This success must be
due to the strong association of the HF acid product in the low-
dielectric supercritical fluid. Addition of base was shown to give
6
reducing radical product seems to be the only explanation for
our results in alkaline phenol solution.
anomalously high results, which is interpreted as a chain reaction
IV. Discussion
•
carried by the OH radical product of the SF
OH radical must react with phenol or a secondary radiolytic
product, to give a radical which can reduce the SF , but only in
6
decomposition.
•
The results of the present study for neutral supercritical water
solutions confirm the measurements of electron scavenging
carried out in part 1 using the N
time it becomes very clear that the scavenging results are very
sensitive to the concentration of added base, due to the very
6
6
2
O scavenger. At the same
alkaline solutions. Use of methanol scavenger in place of phenol
showed a similar chain reaction in both neutral and alkaline
supercritical water solutions.

7
484 J. Phys. Chem. A, Vol. 114, No. 28, 2010
Haygarth and Bartels
Acknowledgment. The Notre Dame Radiation Laboratory
(10) Ho, P. C.; Palmer, D. A.; Wood, R. H. J. Phys. Chem. B 2000,
04, 12084.
1
is supported by the Office of Basic Energy Sciences at the
United States Department of Energy. Additional support for this
project has been provided by US-DOE NERI Grant 02-060. This
is document number NDRL-4846 from the Notre Dame Radia-
tion Laboratory.
(
(
11) Kritzer, P. J. Supercrit. Fluids 2004, 29, 1.
12) Ho, P. C.; Palmer, D. A.; Gruszkiewicz, M. S. J. Phys. Chem. B
2001, 105, 1260.
(13) Tremaine, P.; Zhang, K.; Benezeth, P.; Xiao, C. Ionization equilibria
of acids and bases under hydrothermal conditions. In Aqueous Systems at
EleVated Temperatures and Pressures; Palmer, D. A., Fernandez-Prini, R.,
Harvey, A. H., Eds.; Elsevier Academic Press: Amsterdam, 2004; p 442.
References and Notes
(
14) Weast, R. CRC Handbook of Chemistry and Physics, 52nd ed.;
CRC Press: Boca Raton, FL, 1971.
(
1) Elliot, A. J.; Bartels, D. M. The Reaction Set, Rate Constants and
(
(
15) Anbar, M.; Neta, P. Trans. Faraday Soc. 1967, 63, 141.
16) Takahashi, K.; Bartels, D. M.; Cline, J. A.; Jonah, C. D. Chem.
g-Values for the Simulation of the Radiolysis of Light Water oVer the Range
2
1
0° to 350°C Based on Information AVailable in 2008; Report AECL 153-
Phys. Lett. 2002, 357, 358.
17) Ryan, T. G.; Sambrook, T. E. M.; Freeman, G. R. J. Phys. Chem.
978, 82, 26.
27160-450-001; Atomic Energy of Canada, Ltd., 2009.
(
(2) Takiguchi, H.; Ullberg, M.; Uchida, S. J. Nucl. Sci. Technol. 2004,
1
4
1, 601.
(
18) Ryan, T. G.; Freeman, G. R. J. Phys. Chem. 1977, 81, 1455.
(
(
(
3) Macdonald, D. D. Corrosion 1992, 48, 194.
(
19) Miyazaki, T.; Katsumura, Y.; Lin, M. Z.; Muroya, Y.; Kudo, H.;
4) Christensen, H. Nucl. Technol. 1995, 109, 373.
Taguchi, M.; Asano, M.; Yoshida, M. Radiat. Phys. Chem. 2006, 75, 408.
(20) Tripathi, G. N. R.; Su, Y. L. J. Phys. Chem. A 2004, 108, 3478.
(21) Ye, M. Y.; Schuler, R. H. J. Phys. Chem. 1989, 93, 1898.
(22) Bonin, J.; Janik, I.; Janik, D.; Bartels, D. M. J. Phys. Chem. A
2007, 111, 1869.
(23) Cline, J.; Takahashi, K.; Marin, T. W.; Jonah, C. D.; Bartels, D. M.
J. Phys. Chem. A 2002, 106, 12260.
(24) Katsumura, Y. Personal communication.
5) McCracken, D. R.; Tsang, K. T.; Laughton, P. J. Aspects of the
physics and chemistry of Water Radiolysis by Fast Neutrons and Fast
Electrons in Nuclear Reactors; Report AECL-11895; Atomic Energy of
Canada, Ltd., 1998.
(
6) Janik, D.; Janik, I.; Bartels, D. M. J. Phys. Chem. A 2007, 111,
7
777.
(
7) Haygarth, K.; Janik, D.; Janik, I.; Bartels, D. M. J. Phys. Chem. A
2
010, 114, 5034.
(
8) Edwards, E. J.; Wilson, P. P. H.; Anderson, M. H.; Mezyk, S. P.;
(
25) Lin, M. Z.; Katsumura, Y.; Muroya, Y.; He, H.; Wu, G. Z.; Han,
Pimblott, S. M.; Bartels, D. M. ReV. Sci. Instrum. 2007, 78, 124101.
9) Asmus, K. D.; Gruenbein, W.; Fendler, J. H. J. Am. Chem. Soc.
970, 92, 2625.
Z. H.; Miyazaki, T.; Kudo, H. J. Phys. Chem. A 2004, 108, 8287.
(
1
JP1025366