Download - Nuclear Chem Intro
Special Focus on Nuclear Chemistry
Nuclear chemistry : An introduction
NUCLEAR chemistry is the study of the chemical and
physical properties of elements as influenced by changes
in the structure of the atomic nucleus. Modern nuclear
chemistry, sometimes referred to as radiochemistry, has
become very interdisciplinary in its applications, ranging
from the study of the formation of the elements in the
universe to the design of radioactive drugs for diagnostic
medicine. In fact, the chemical techniques pioneered by
nuclear chemists have become so important that biolo-
gists, geologists, and physicists use nuclear chemistry as
ordinary tools of their disciplines. While the common
perception is that nuclear chemistry involves only the
study of radioactive nuclei, advances in modern mass
spectrometry instrumentation has made chemical studies
using stable, nonradioactive isotopes increasingly impor-
tant.
There are essentially three sources of radioactive ele-
ments. Primordial nuclides are radioactive elements whose
half-lives are comparable to the age of our solar system and
were present at the formation of Earth. These nuclides are
generally referred to as naturally occurring radioactivity and
are derived from the radioactive decay of thorium and
uranium. Cosmogenic nuclides are atoms that are con-
stantly being synthesized from the bombardment of plan-
etary surfaces by cosmic particles (primarily protons
ejected from the Sun), and are also considered natural in
their origin. The third source of radioactive nuclides is
termed anthropogenic and results from human activity in
the production of nuclear power, nuclear weapons, or
through the use of particle accelerators.
Lasers focus on a small pellet of fuel in attempt to create
a nuclear fusion reaction (the combination of two nuclei to
produce another nucleus) for the purpose of producing
energy.
Marie Curie was the founder of the field of nuclear
chemistry. She was fascinated by Antoine-Henri Becquerel's
discovery that uranium minerals can emit rays that are
able to expose photographic film, even if the mineral
is wrapped in black paper. Using an electrometer
invented by her husband Pierre and his brother Jacques
that measured the electrical conductivity of air (a
precursor to the Geiger counter), she was able to
show that thorium also produced these rays—a pro-
cess that she called radioactivity. Through tedious
chemical separation procedures involving precipita-
tion of different chemical fractions, Marie was able to
show that a separated fraction that had the chemical
properties of bismuth and another fraction that had the
chemical properties of barium were much more radio-
active per unit mass than the original uranium ore.
She had separated and discovered the elements polo-
nium and radium, respectively. Further purification of
radium from barium produced approximately 100 mil-
32 CHEMICAL BUSINESS <> DECEMBER 2012
ligrams of radium from an initial sample of nearly
2,000 kilograms of uranium ore.
In 1911 Ernest Rutherford asked a student, George de
Hevesy, to separate a lead impurity from a decay product
of uranium, radium-D. De Hevesy did not succeed in this
task (we now know that radium-D is the radioactive isotope
210 Pb), but this failure gave rise to the idea of using
radioactive isotopes as tracers of chemical processes.
With Friedrich Paneth in Vienna in 1913, de Hevesy used
210 Pb to measure the solubility of lead salts—the first
application of an isotopic tracer technique. De Hevesy
went on to pioneer the application of isotopic tracers to
study biological processes and is generally considered to
be the founder of a very important area in which nuclear
chemists work today, the field of nuclear medicine. De
Hevesy also is credited with discovering the technique of
neutron activation analysis, in which samples are bom-
barded by neutrons in a nuclear reactor or from a neutron
generator, and the resulting radioactive isotopes are mea-
sured, allowing the analysis of the elemental composition
of the sample.
In Germany in 1938, Otto Hahn and Fritz Strassmann,
skeptical of claims by Enrico Fermi and Irène Joliot-Curie
that bombardment of uranium by neutrons produced new
so-called transuranic elements (elements beyond ura-
nium), repeated these experiments and chemically iso-
lated a radioactive isotope of barium. Unable to interpret
these findings, Hahn asked Lise Meitner, a physicist and
former colleague, to propose an explanation for his obser-
vafions. Meitner and her nephew. Otto Frisch, showed that
it was possible for fhe uranium nucleus to be split into two
smaller nuclei by the neutrons, a process that they termed
" fission ." The discovery of nuclear fission eventually led
to the development of nuclear weapons and, after World
War II, the advent of nuclear power to generate electricity.
Nuclear chemists were involved in the chemical purifica-
tion of plutonium obtained from uranium targets that had
been irradiated in reactors. They also developed chemical
separation techniques to isolate radioactive isotopes for
industrial and medical uses from fhe fission products
wastes associated with plutonium production for weapons.
Today, many of these same chemical separation tech-
niques are being used by nuclear chemists to clean up
radioactive wastes resulting from the fifty-year production
of nuclear weapons and to treat wastes derived from fhe
production of nuclear power.
In 1940, at the University of California in Berkeley,
Edwin McMillan and Philip Abelson produced fhe first
manmade element, neptunium (Np), by the bombardment
of uranium with low energy neutrons from a nuclear accel-
erator. Shortly thereafter, Glenn Seaborg, Joseph Kennedy,
Arthur Wahl, and McMillan made the element plutonium by
bombarding uranium targets with deuterons, particles de-
rived from the heavy isotope of hydrogen, deuterium ( 2 H).
Both McMillan and Seaborg recognized that the chemical
properties of neptunium and plutonium did not resemble
those of rhenium and osmium, as many had predicted, but
more closely resembled the chemistry of uranium, a fact
that led Seaborg in 1944 to propose that the transuranic
elements were part of a new group of elements called the
actinide series that should be placed below the lanthanide
series on the periodic chart. Seaborg and coworkers went
on to discover many more new elements and radioactive
isotopes and to study their chemical and physical proper-
ties. At the present, nuclear chemists are involved in trying
to discover new elements beyond the 112 that are presently
confirmed and to study the chemical properties of these
new elements, even though they may exist for only a few
fhousandths of a second.
Nobel laureate Glenn T. Seaborg was among those who
discovered many radioactive elements and isotopes.
As early as 1907
Bertram Boltwood had
used the discovery of ra-
dioactive decay laws by
Ernest Rutherford and
Frederick Soddy to ascribe
an age of over two billion
years to a uranium min-
eral. In 1947 Willard Libby
at the University of Chi-
cago used the decay of '̂̂
C to measure the age of
dead organic matter. The
cosmogenic radionuclide,
•̂̂ C, becomes part of all living matter through photosynthe-
sis and the consumption of plant mafter. Once the living
organism dies, the ^̂ C decays at a known rate, enabling a
date for the carbon-containing relic to be calculated.
Today, scientists ranging from astrophysicists to marine
biologists use the principles of radiometric dating to study
problems as diverse as determining the age of the universe
to defining food chains in the oceans. In addition, newly
developed analytical techniques such as accelerator mass
spectrometry (AMS) have allowed nuclear chemists to
extend the principles of radiometric dating to nonradioac-
tive isotopes in order to study modern and ancient pro-
CHEMICAL BUSINESS •> DECEMBER 2012 33
cesses that are affected by isotopic frac-tionation. This isotopic fractionation re-sults from temperature differences in theenvironment in which the material wasformed (at a given temperature, the lighterisotope will be very slightly more reactivethan the heavier isotope), or from differentchemical reaction sequences.
The newest area in which nuclear chem-ists play an important role is the field ofnuclear medicine. Nuclear medicine is arapidly expanding branch of health carethat uses short-lived radioactive isotopesto diagnose illnesses and to treat specificdiseases. Nuclear chemists synthesize drugs from radio-nuclides produced in nuclear reactors or accelerators thatare injected into the patient and will then seek out specificorgans or cancerous tumors. Diagnosis involves use of theradiopharmaceutical to generate an image of the tumor ororgan to identify problems that may be missed by x rays orphysical examinations. Treatment involves using radioac-tive compounds at carefully controlled doses to destroytumors. These nuclear medicine techniques hold muchpromise for the future because they use biological chem-istry to specify target cells much more precisely thantraditional radiation therapy, which uses radiation fromexternal sources to kill tumor cells, killing nontarget cellsas well. Additionally, the use of nuclear Pharmaceuticals
containing the short-lived isotope ^̂ C has allowed nuclearchemists and physicians to probe brain activity to betterunderstand the biochemical basis of illnesses ranging fromParkinson's disease to drug abuse.
Bibliography
• Hoffman, D.C.; Ghiorso, A.; and Seaborg, Glenn T., eds. (2000).The Transuranium People: An Intimate Glimpse. London: ImperialCollege Press.
• Morrissey, D.; Loveland, W.T.; and Seaborg, Glenn T. (2001).Introductory Nuclear Chemistry. New York: John Wiley & Sons.
• Rydberg, J.; Liljenzin, J,-0 and Choppin, Gregory R. (2001).Radiochemistry and Nuclear Chemistry, 3rd edition. Woburn,MA; Butterwoth-Heinemann •
Nuclear chemistry(Contd. from page 31)
References
[1] ( h t t p : / / w w w . o s t i . g o v / e n e r g y c i t a t i o n s /product.biblio.jsp?osti_id=6050016)
[2] http://nobelprize.org/nobel_prizes/chemistry/laureates/1935/joliot-fred-bio.html
[3] A.G.Chmielewski, Chemistry for the nuclear energy of the future,Nukleonika, 56(3), 241 - 249, 2011.
[4] Meitner L, Frisch OR (1939) Disintegration of uranium byneutrons: a new type of nuclear reaction Nature 143:239-240 [2]
[5] J.H. Burns, "Solvent-extraction complexes of the uranyl ion. 2.Crystal and molecular structures of catena-bis(.mu.-di-n-butylphosphato-O,O')dioxouranium(VI) and bis(.mu.-di-n-butylp h o s p h a t o - O , O ' ) b i s [ ( n i t r a t o ) ( t r i - n - b u t y l p h o s p h i n eoxide)dioxouranium(VI)]", Inorganic Chemistry, 1983, 22, 1174-1178
[6] Decontamination of surfaces, George H. Goodalland Barry.E.Gillespie, United States Patent 4839100
[7] Glänneskog H (2004) Interactions of 12 and CH3I with reactivemetals under BWR severe-accident conditions Nuclear Engi-neering and Design 227:323-9Glänneskog H (2005) Iodine chemistry under severe accidentconditions in a nuclear power reactor, PhD thesis, Chalmersuniversity of Technology, SwedenFor other work on the iodine chemistry which would occur duringa bad accident, see [3][4][5]
[8] Peter Atkins and Julio de Paula, Atkins' Physical Chemistry, 8thedn (W.H. Freeman 2006), p.816-8
[9] Miller PW et al. (2006) Chemical Communications 546-548
34 CHEMICAL BUSINESS <• DECEMBER 2012
Copyright of Chemical Business is the property of Colour Publications Pvt, Ltd. and its content may not be
copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written
permission. However, users may print, download, or email articles for individual use.