Radioisotope of iodine
Iodine-129
(
129
I) is a long-lived
radioisotope
of
iodine
that occurs naturally but is also of special interest in the monitoring and effects of man-made nuclear
fission products
, where it serves as both a tracer and a potential radiological contaminant.
Formation and decay
[
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]
129
I is one of seven
long-lived fission products
. It is primarily formed from the
fission
of
uranium
and
plutonium
in
nuclear reactors
. Significant amounts were released into the
atmosphere
by
nuclear weapons testing
in the 1950s and 1960s, by
nuclear reactor accidents
and by both military and civil reprocessing of spent nuclear fuel.
[3]
It is also naturally produced in small quantities, due to the
spontaneous fission
of
natural uranium
, by
cosmic ray spallation
of trace levels of
xenon
in the atmosphere, and by
cosmic ray
muons
striking
tellurium
-130.
[4]
[5]
129
I decays with a
half-life
of 15.7 million years, with low-energy
beta
and
gamma
emissions, to stable
xenon-129
(
129
Xe).
[6]
Long-lived fission product
[
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]
129
I is one of the seven
long-lived fission products
that are produced in significant amounts. Its yield is 0.706% per fission of
235
U
.
[7]
Larger proportions of other iodine isotopes such as
131
I
are produced, but because these all have short half-lives, iodine in cooled
spent nuclear fuel
consists of about 5/6
129
I and 1/6 the only stable iodine isotope,
127
I.
Because
129
I is long-lived and relatively mobile in the environment, it is of particular importance in long-term management of spent nuclear fuel. In a
deep geological repository
for unreprocessed used fuel,
129
I is likely to be the radionuclide of most potential impact at long times.
Since
129
I has a modest
neutron absorption
cross-section
of 30
barns
,
[8]
and is relatively undiluted by other isotopes of the same element, it is being studied for disposal by
nuclear transmutation
by re-irradiation with
neutrons
[9]
or by high-powered lasers.
[10]
Release by nuclear fuel reprocessing
[
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]
A large fraction of the
129
I contained in spent fuel is released into the gas phase, when spent fuel is first chopped and then dissolved in boiling
nitric acid
during reprocessing.
[3]
At least for civil reprocessing plants, special scrubbers are supposed to withhold 99.5% (or more) of the Iodine by adsorption,
[3]
before exhaust air is released into the environment. However, the Northeastern Radiological Health Laboratory (NERHL) found, during their measurements at the first US civil reprocessing plant, which was operated by
Nuclear Fuel Services, Inc. (NFS)
in Western New York, that "between 5 and 10% of the total
129
I available from the dissolved fuel" was released into the exhaust stack.
[3]
They further wrote that "these values are greater than predicted output (Table 1). This was expected since the iodine scrubbers were not operating during the dissolution cycles monitored."
[3]
The Northeastern Radiological Health Laboratory further states that, due to limitations of their measuring systems, the actual release of
129
I may have even been higher, "since [
129
I] losses [by adsorption] probably occurred in the piping and ductwork between the stack and the sampler".
[3]
Furthermore, the sample taking system used by the NERHL had a bubbler trap for measuring the
tritium
content of the gas samples before the iodine trap. The NERHL found out only after taking the samples that "the bubbler trap retained 60 to 90% of the
129
I sampled".
[3]
They concluded: "The bubblers located upstream of the ion exchangers removed a major portion of the gaseous
129
I before it reached the ion exchange sampler. The iodine removal ability of the bubbler was anticipated, but not in the magnitude that it occurred." The documented release of "between 5 and 10% of the total
129
I available from the dissolved fuel"
[3]
is not corrected for those two measurement deficiencies.
Military isolation of plutonium from spent fuel has also released
129
I to the atmosphere: "More than 685,000 curies of iodine 131 spewed from the stacks of Hanford's separation plants in the first three years of operation."
[11]
As
129
I and
131
I have very similar physical and chemical properties, and no isotope separation was performed at Hanford,
129
I must have also been released there in large quantities during the Manhattan project. As Hanford reprocessed "hot" fuel, that had been irradiated in a reactor only a few months earlier, the activity of the released short-lived
131
I, with a half-life time of just 8 days, was much higher than that of the long-lived
129
I. However, while all of the
131
I released during the times of the Manhattan project has decayed by now, over 99.999% of the
129
I is still in the environment.
Ice borehole data obtained from the university of Bern at the Fiescherhorn glacier in the Alpian mountains at a height of 3950 m show a somewhat steady increase in the
129
I deposit rate (shown in the image as a solid line) with time. In particular, the highest values obtained in 1983 and 1984 are about six times as high as the maximum that was measured during the period of the atmospheric bomb testing in 1961. This strong increase following the conclusion of the atmospheric bomb testing indicates that nuclear fuel reprocessing has been the primary source of atmospheric iodine-129 since then. These measurements lasted until 1986.
[12]
Applications
[
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]
Groundwater age dating
[
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]
129
I is not deliberately produced for any practical purposes. However, its long half-life and its relative mobility in the environment have made it useful for a variety of dating applications. These include identifying older groundwaters based on the amount of natural
129
I (or its
129
Xe decay product) present, as well as identifying younger groundwaters by the increased anthropogenic
129
I levels since the 1960s.
[13]
[14]
[15]
Meteorite age dating
[
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]
In 1960, physicist
John H. Reynolds
discovered that certain
meteorites
contained an isotopic anomaly in the form of an overabundance of
129
Xe. He inferred that this must be a
decay product
of long-decayed radioactive
129
I. This isotope is produced in quantity in nature only in
supernova
explosions. As the half-life of
129
I is comparatively short in astronomical terms, this demonstrated that only a short time had passed between the supernova and the time the meteorites had solidified and trapped the
129
I. These two events (supernova and solidification of gas cloud) were inferred to have happened during the early history of the
Solar System
, as the
129
I isotope was likely generated before the Solar System was formed, but not long before, and seeded the solar gas cloud isotopes with isotopes from a second source. This supernova source may also have caused collapse of the solar gas cloud.
[16]
[17]
See also
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]
References
[
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]
- ^
Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017).
"The NUBASE2016 evaluation of nuclear properties"
(PDF)
.
Chinese Physics C
.
41
(3): 030001.
Bibcode
:
2017ChPhC..41c0001A
.
doi
:
10.1088/1674-1137/41/3/030001
.
- ^
Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017).
"The AME2016 atomic mass evaluation (II). Tables, graphs, and references"
(PDF)
.
Chinese Physics C
.
41
(3): 030003-1?030003-442.
doi
:
10.1088/1674-1137/41/3/030003
.
- ^
a
b
c
d
e
f
g
h
"An INVESTIGATION of AIRBORNE RADIOACTIVE EFFLUENT from an OPERATING NUCLEAR FUEL REPROCESSING PLANT"
.
- ^
Edwards, R. R. (1962). "Iodine-129: Its Occurrenice in Nature and Its Utility as a Tracer".
Science
.
137
(3533): 851?853.
Bibcode
:
1962Sci...137..851E
.
doi
:
10.1126/science.137.3533.851
.
PMID
13889314
.
S2CID
38276819
.
- ^
"Radioactives Missing From The Earth"
.
- ^
https://www.nndc.bnl.gov/nudat3/decaysearchdirect.jsp?nuc=129I&unc=nds
, NNDC Chart of Nuclides, I-129 Decay Radiation, accessed 7 May 2021.
- ^
a
b
http://www-nds.iaea.org/sgnucdat/c3.htm
Cumulative Fission Yields,
IAEA
- ^
http://www.nndc.bnl.gov/chart/reColor.jsp?newColor=sigg
Archived
2017-01-24 at the
Wayback Machine
, NNDC Chart of Nuclides, I-129 Thermal neutron capture cross-section, accessed 16-Dec-2012.
- ^
Rawlins, J. A.; et al. (1992).
"Partitioning and transmutation of long-lived fission products"
.
Proceedings International High-Level Radioactive Waste Management Conference
. Las Vegas, USA.
OSTI
5788189
.
- ^
Magill, J.; Schwoerer, H.; Ewald, F.; Galy, J.; Schenkel, R.; Sauerbrey, R. (2003). "Laser transmutation of iodine-129".
Applied Physics B
.
77
(4): 387?390.
Bibcode
:
2003ApPhB..77..387M
.
doi
:
10.1007/s00340-003-1306-4
.
S2CID
121743855
.
- ^
Grossman, Daniel (1 January 1994). "Hanford and Its Early Radioactive Atmospheric Releases".
The Pacific Northwest Quarterly
.
85
(1): 6?14.
doi
:
10.2307/3571805
.
JSTOR
40491426
.
PMID
4157487
.
- ^
F. Stampfli:
Ionenchromatographische Analysen an Eisproben aus einem hochgelegenen Alpengletscher.
Lizentiatsarbeit, Inst. anorg. anal. und phys. Chemie, Universitat Bern, 1989.
- ^
Watson, J. Throck; Roe, David K.; Selenkow, Herbert A. (1 January 1965). "Iodine-129 as a "Nonradioactive" Tracer".
Radiation Research
.
26
(1): 159?163.
Bibcode
:
1965RadR...26..159W
.
doi
:
10.2307/3571805
.
JSTOR
3571805
.
PMID
4157487
.
- ^
Santschi, P.; et al. (1998).
"
129
Iodine: A new tracer for surface water/groundwater interaction"
(PDF)
.
Lawrence Livermore National Laboratory
.
OSTI
7280
.
- ^
Snyder, G.; Fabryka-Martin, J. (2007). "I-129 and Cl-36 in dilute hydrocarbon waters: Marine-cosmogenic,in situ, and anthropogenic sources".
Applied Geochemistry
.
22
(3): 692?714.
Bibcode
:
2007ApGC...22..692S
.
doi
:
10.1016/j.apgeochem.2006.12.011
.
- ^
Clayton, Donald D. (1983).
Principles of Stellar Evolution and Nucleosynthesis
(2nd ed.). University of Chicago Press. pp.
75
.
ISBN
978-0226109534
.
- ^
Bolt, B. A.; Packard, R. E.; Price, P. B. (2007).
"John H. Reynolds, Physics: Berkeley"
. The University of California, Berkeley
. Retrieved
2007-10-01
.
Further reading
[
edit
]
- Snyder, G. T.; Fabryka-Martin, J. T. (2007). "129I and 36Cl in dilute hydrocarbon waters: Marine-cosmogenic, in situ, and anthropogenic sources".
Applied Geochemistry
.
22
(3): 692.
Bibcode
:
2007ApGC...22..692S
.
doi
:
10.1016/j.apgeochem.2006.12.011
.
- Snyder, G.; Fehn, U. (2004). "Global distribution of 129I in rivers and lakes: Implications for iodine cycling in surface reservoirs".
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
. 223?224: 579?586.
Bibcode
:
2004NIMPB.223..579S
.
doi
:
10.1016/j.nimb.2004.04.107
.
External links
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]