Radiation chemistry of normal and heavy water solutions

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Title:
Radiation chemistry of normal and heavy water solutions
Series Title:
ANL / Argonne National Laboratory ;
Alternate Title:
Radiation-induced oxidation of ferrous sulfate
Physical Description:
8 p. : ill. ; 27 cm.
Language:
English
Creator:
McDonell, William R
Argonne National Laboratory
U.S. Atomic Energy Commission
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U.S. Atomic Energy Commission
Place of Publication:
Oak Ridge, Tenn
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Subjects / Keywords:
Radiation chemistry   ( lcsh )
Physiologic salines   ( lcsh )
Ferrous sulfate -- Oxidation   ( lcsh )
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technical report   ( marcgt )
federal government publication   ( marcgt )
non-fiction   ( marcgt )

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Bibliography:
Includes bibliographical references (p. 8) and abstract.
Restriction:
"Date Declassified: December 2, 1955."
Funding:
Operated by the University of Chicago under
General Note:
"January 12, 1954."
General Note:
Originally published 1954.
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Cover title.
General Note:
At head of title: Argonne National Laboratory.
Statement of Responsibility:
by William R. McDonell.

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University of Florida
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oclc - 61661696
sobekcm - AA00005289_00001
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Full Text
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UNCLASSIFIED


UNCLASSIFIED


ANL-5206

Subject Category: CHEMISTRY



UNITED STATES ATOMIC ENERGY COMMISSION


RADIATION CHEMISTRY OF NORMAL AND
HEAVY WATER SOLUTIONS. I. RADIATION-
INDUCED OXIDATION OF FERROUS SULFATE

By
William R. McDonell


A -,. i '


January 12, 1954

Argonne National Laboratory
Lemont, Illinois


Technical Information Service, Oak Ridge, Tennessee























Date Declassified: December 2, 1955.


This report has been reproduced directly from the best
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Issuance of this document does not constitute authority
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This report was prepared asa scientific account of Govern-
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disclosed in this report.









ANL-5206


ARGONNE NATIONAL LABORATORY
P. O. Box 299
Lemont, Illinois







RADIATION CHEMISTRY OF NORMAL AND HEAVY WATER SOLUTIONS

I. RADIATION-INDUCED OXIDATION OF FERROUS SULFATE

by

William R. McDonell*


CHEMISTRY DIVISION

*E. I. duPont de Nemours Loaned Employee






January 12, 1954








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under
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Digitized by the Internet Archive
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RADIATION CHEMISTRY OF NORMAL AND HEAVY WATER SOLUTIONS

I. RADIATION-INDUCED OXIDATION OF FERROUS SULFATE

by

William R. McDonell


ABSTRACT

The Co60 gamma-ray-induced oxidation of ferrous sulfate
in 0.8 N sulfuric acid-heavy water solutions proceeds with a
specific yield, GFe+++,of 17.5, compared to 15.6 for normal
water solutions. Pile irradiation yields show a similar but
smaller enhancement of ferric ionyields in heavy water solu-
tions, the difference probably due to greater flux of capture
gamma radiation in the normal water, than in heavy water
solutions.


EXPERIMENTAL PROCEDURE

Solutions of 0.001N ferrous sulfate and 0.8N sulfuric acid were pre-
pared in normal and heavy water using recrystallized FeSO4 HzO and reagent
grade sulfuric acid. The normal water used was purified by a standard
triple-distillation procedure described previously.(1) The heavy water was
purified in a similar fashion: Successive distillations from two alkaline
potassium permanganate solutions were made, and the vapor distillate from
the second distillation was swept in a stream of oxygen through a quartz fur-
nace tube heated to 8000C and condensed into a slightly acid dichromate solu-
tion. The water was redistilled from this solution, again heated to 8000C in
an oxygen stream, and condensed into a quartz receptacle. Using exhaustive
irradiation with Co60 gamma rays as a test for purity, negligible amounts of
gaseous products were yielded by both normal and heavy water, indicating a
high degree of purity with respect to organic contaminants. The heavy water,
with an isotopic analysis of 99.6% D20, was diluted by the dissolved reagents
to a calculated purity of about 99%.

The solutions, air saturated,() were drawn into 12 ml, 2-cm diameter
irradiation cells, which were made of Pyrex for the Co60 source irradiations
and of quartz for the pile irradiations. For the pile irradiations, the cells
were placed in standard 15-in. aluminum cans, two to a can, one with normal
and the other with heavy water as solvent. These cells were situated one
above the other in such a fashion that, when irradiated, they occupied mean
vertical positions about 6 in. apart; they were thus susceptible to any flux










variation which might be encountered over this distance in the vertical
thimble. The relative positions, above and below, of the normal and heavy
water samples were alternated, however, to detect such a variation.

Irradiations of one, two, and three minutes duration were carried
out with the 400-curie Co60 source at 3 cm distance; irradiations of 0.5,
1.0, 1.5, and 2.0 minutes duration were carried out in the Argonne heavy-
water reactor, CP-3'. The pile irradiations were made in vertical thimble
#2 (VT-2). Each can was dropped into the thimble with the pile at full power
the irradiation timed by stopwatch, and the can rapidly withdrawn. The
timing precision was estimated at t 5 seconds.

The analysis of the solutions for ferric ion was made in standard
fashion(3) by ultraviolet absorption at wavelength 3020A on a Beckman
Model DU quartz spectrophotometer. The concentration of ferric ion in
jiN is given by 449dD where D is the optical density of the solution and d
is the dilution employed.


RESULTS AND DISCUSSION

Ferrous sulfate was oxidized by Co60 gamma radiation at a rate 12%
greater in heavy water than in light water (Figure 1), indicating a GFe+++ of
17.5, as compared with Hochanadel and Ghormley's value of 15.6 for light
water.(4)

Since the linear absorption efficiency for gamma radiation in the one
Mev range is essentially the same in heavy water as in light water,* the en-
hancement of the rate of oxidation in the heavy water may be ascribed to a
difference in its radiation chemical behavior. Radiation-induced oxidation
of ferrous ion comes about as a consequence of the production of free radicals
and molecular decomposition products by the reactions (1) and (2), respectively.

HO H + OH (1)

HzO 1/2 Hz + 1/2 HzOz (2)

The mechanism(2) requires that in aerated solutions, the yield of ferric ion
from (1) be four times that resulting from (2).

*The electron (unit volume) density of light and heavy water can be seen
to be approximately equal by a comparison of their respective molecular
weights and volume densities (p). Ratio electrons (per unit volume)

= ratio of moles (per unit volume) = [(PDO)/(MHzO)]/[( PDO)/(MHzO)


= 1 where pDzO = 1.1, MDzO = 20, MHzO = 18.









400



350 -



300

D20-.,

250 HO
H20

IL
200 -



150 -



100 -



50




0 60 120 180 240
TIME IRRADIATED (sec.)


FIGURE I.

Co60 GAMMA RAY INDUCED OXIDATION OF
FERROUS SULFATE IN LIGHT AND HEAVY
WATER-O.8N SULFURIC ACID SOLUTIONS.
DOSAGE RATE 3.3 x 1020 ev/liter min.











Hart(5) has determined the fraction of water molecules decomposing
by means of reaction (1) under Co60 and pile gamma radiation as 790" in
normal water solutions, while 85% of heavy water molecules decompose to
radicals under Go60 irradiation.(6) Thus the ferrous ion yield per molecule
of water decomposed is 5% higher for heavy water than for normal water,
and a 7% enhancement in the effective total yield of water molecules decom-
posed occurs in the heavy water solutions. The absolute yields of water
molecules decomposed per 100 ev calculated from the stoichiometry of the
reaction are 4.6 for the normal water solutions and 4.9 for the heavy water
solutions.

In Figure 2 are shown the rate of oxidation curves for irradiation
in VT-2 of reactor CP-3'. It is obvious from the data that the difference
in vertical position of the cells in the column during irradiation, alternately
top and bottom of the can, results in a variation in gamma flux. The normal
and heavy water oxidations are comparable only under the same flux con-
ditions, and thus the data must be considered in two parts. Curves A and B
represent the rates of oxidation in heavy and normal water respectively, the
samples irradiated being at the top of the irradiation can; these are 327 and
299 iPN Fe++/min respectively. Curves C and D are analogous rate curves
for the samples at the bottom of the can, 291 and 289 Fe++/liter min. The
cans were irradiated at the bottom of the vertical thimble. Such an arrange-
ment places the cells in the bottom of the can out of the region of maximum
flux, presumably some 6 to 18 in. up on the thimble. Thus, the higher rate
of oxidation in cells at the top of the can is in accord with what is expected
from the flux variations along the vertical thimble.

The variation in ratio of rates of oxidation in heavy and normal water
is decreased in the lower irradiation position relative to that of the upper
position. The upper position shows a ratio of rates of 1.09 while in the lower
position the ratio is about 1.01. These represent, as well, a decrease from
the ratio 1.12 observed for Co60 gamma irradiation.

The general decrease in the ratio of the rates of oxidation by the pile
radiation may be attributed to neutron effects. The relatively greater capture
cross section of hydrogen over deuterium tends to enhance the gamma flux in
the light water over that in the heavy water. In addition, the greater moder-
ating efficiency of normal water over heavy water results in a higher rate of
fast neutron energy dissipation and may give rise to an enhancement of the
chemical effect produced by knock-on protons.

It can be assumed that the upper cans irradiated toward the center
of the pile were in a region of higher neutron flux and lower moderation
(i.e., higher mean energy) than the lower cans. Thus a greater probability
for production of an extra gamma flux component by capture of thermal
neutrons in the normal water would exist in the lower cans, in the region
of the higher moderation. This would tend to decrease the difference in
ferric ion yields in normal and heavy water solutions in the lower cans, as
was observed.











700 1 I

0 H20 solutions
DgO solutions
600 -
STop of irradiation cans

50 Bottom of irradiation cans
500 -

A

+ 400
+
IL
D

I300 -



200 -



100



0 I I I I
0 0.5 1.0 1.5 2.0
TIME IRRADIATED (min.)


FIGURE 2.

OXIDATION OF FERROUS SULFATE IN NORMAL
AND HEAVY WATER-0.8N SULFURIC ACID
SOLUTION BY ARGONNE HEAVY WATER
REACTOR RADIATIONS. PILE POWER 275 kw.












ACKNOWLEDGEMENTS

I am indebted to Dr. E. J. Hart for enlightening discussions of this
research, to Miss Patricia Walsh for technical assistance, and to Dr. W. H.
McCorkle and the operating crev, of the Argonne reactors for carrying out
the pile irradiations.

















REFERENCES

1. E. J. Hart, J. Am. Chem. Soc. 73, 68 (1951).

2. E. J. Hart, J. Am. Chem. Soc. 73, 1891 (1951).

3. E. J. Hart, J. Am. Chem. Soc. 74, 4174 (1952).

4. C. J. Hochanadel and J. A. Ghormley, J. Chem. Phys. 21, 880 (1953).

5. E. J. Hart, J. Phys. Chem. 56, 594 (1952).


6. E. J. Hart, private communication.



































































































































































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