56
UNIT ONE
2.2
FROM SCIENCE TO TECHNOLOGY
Ionizing Radiation: From the Cold War to Yucca Mountain
A
lpha, beta, and gamma radiation are
called ionizing radiation because their
energy removes electrons from atoms
(F
g. 2C). Electrons dislodged by ionizing radiation
can a±
ect nearby atoms, disrupting physiology at
the chemical level in a variety of ways—causing
cancer, clouding the lens of the eye, and interfer-
ing with normal growth and development.
In the United States, some people are
exposed to very low levels of ionizing radia-
tion, mostly from background radiation, which
originates from natural environmental sources
(table 2A). ²or people who live near sites of
atomic weapons manufacture, exposure is
greater. Epidemiologists are investigating medi-
cal records that document illnesses linked to
long-term exposure to ionizing radiation in a
1,200-square kilometer area in Germany.
The lake near Oberrothenback, Germany,
which appears inviting, harbors enough toxins to
kill thousands of people. It is polluted with heavy
metals, low-level radioactive chemical waste,
and 22,500 tons of arsenic. Radon, a radioactive
by-product of uranium, permeates the soil. Many
farm animals and pets that have drunk from the
lake have died. Cancer rates and respiratory disor-
ders among the human residents nearby are well
above normal.
The lake in Oberrothenback was once a dump
for a factory that produced “yellow cake,” a term
for processed uranium ore, used to build atomic
bombs for the former Soviet Union. In the early
1950s, nearly half a million workers labored here
and in surrounding areas in factories and mines.
Records released in 1989, after the reunification
of Germany, reveal that workers were given perks,
such as alcoholic beverages and better wages, to
work in the more dangerous areas. The workers
paid a heavy price: many died of lung ailments.
Today, concern over the health effects of
exposure to ionizing radiation centers on the
U.S. government’s plan to transport tens of
thousands of metric tons of high-level nuclear
waste from 109 reactors around the country
for burial beneath Yucca Mountain, Nevada, by
2021. The waste, currently stored near the reac-
tors, will be buried in impenetrable containers
under the mountain by robots. In the reactors,
nuclear fuel rods contain uranium oxide, which
produces electricity as it decays to plutonium,
which gives o±
gamma rays. Periodically the fuel
rods must be replaced, and the spent ones bur-
ied. Environmental groups are concerned that
the waste could be exposed during transport
and that the facility in the mountain may not ade-
quately contain it.
Atoms may also bond by sharing electrons rather than
by gaining or losing them. A hydrogen atom, for example,
has one electron in its ±
rst shell but requires two electrons
to achieve a stable structure. It may ± ll this shell by combin-
ing with another hydrogen atom in such a way that the two
atoms share a pair of electrons. As
f
gure 2.5
shows, the two
electrons then encircle the nuclei of both atoms, ± lling the
outermost shell, and each atom becomes stable. A chemical
bond between atoms that share electrons is called a
covalent
bond
(ko
va-lent bond).
Usually atoms of each element form a speci±
c number of
covalent bonds. Hydrogen atoms form single bonds, oxygen
may lose their single electrons and become hydrogen ions
(H
+
). Hydrogen ions can form ionic bonds with chloride ions
(Cl
) to form hydrogen chloride (HCl, which reacts in water
to form hydrochloric acid).
Cations and anions attract each other in all directions,
forming a three-dimensional structure. Ionically bound com-
pounds do not form speci±
c particles, so they do not exist
as molecules. Rather, they form arrays, such as crystals of
sodium chloride (± g. 2.4
c
). The molecular formulas for com-
pounds such as sodium chloride (NaCl) give the relative
amounts of each element.
TABLE
2A
|
Sources of Ionizing Radiation
Background
(Natural environmental)
Cosmic rays from space
Radioactive elements in earth’s crust
Rocks and clay in building materials
Radioactive elements naturally in the body (potassium-40, carbon-14)
Medical and dental
X rays
Radioactive substances
Other
Atomic and nuclear weapons
Mining and processing radioactive minerals
Radioactive fuels in nuclear power plants
Radioactive elements in consumer products (luminescent dials, smoke
detectors, color TV components)
FIGURE 2C
Ionizing radiation removes
elecrons from atoms. (
a
) Ionizing radiation
may dislodge an electron from an electrically
neutral hydrogen atom. (
b
) Without its
electron, the hydrogen atom becomes a
positively-charged hydrogen ion (H
+
).
+
+
(b)
Hydrogen ion
(H
+
)
Dislodged
electron
Ionizing
radiation
(a)
Hydrogen atom
(H)
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