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5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL
the disposal of HLW. An alternative to burial of spent fuel is to store it for future use as fuel for nuclear
reactors. The uranium and plutonium could be extracted from spent fuel to be used as fuel in nuclear
power plants.
Transuranic wastes (TRUs) contain significant amounts of plutonium or other transuranic elements. As
of 2006, the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico was the only operating
geological disposal facility in the world; TRU has been disposed of in the WIPP since 1999 (Murray and
Fentiman 2006).
In 2002, Yucca Mountain was approved by the Congress and the President as the site for the nation’s first
permanent spent nuclear fuel and high-level radioactive waste geologic repository (DOE 2007b). Most of
the waste that may be disposed at Yucca Mountain will be spent nuclear fuel and high-level radioactive
waste. About 90% of this waste is from commercial nuclear power plants and the rest comes from
defense programs. Currently, this waste is stored at facilities in 43 states. By Department of Energy
(DOE) projections, the earliest the proposed repository at Yucca Mountain could open and begin
accepting waste is 2017; however, various steps must first be met before this can occur (EPA 2009).
Spent fuels must be stored in water pools or in dry storage casks at nuclear plant sites until a repository is
completed (Murray 2005).
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6. POTENTIAL FOR HUMAN EXPOSURE
6.1 OVERVIEW
Plutonium has been identified in at least 16 of the 1,689 hazardous waste sites that have been proposed
for inclusion on the EPA National Priorities List (NPL) (HazDat 2007). However, the number of sites
evaluated for plutonium is not known. The frequency of these sites can be seen in Figure 6-1. Of these
sites, all are located within the United States.
Trace amounts of plutonium are found worldwide, mostly due to fallout from atmospheric nuclear testing,
which ended in 1980, and released several isotopes of plutonium, including
238
Pu,
239
Pu,
240
Pu, and
241
Pu
(Clark et al. 2006; DOE 2005a; Eisenbud and Gesell 1997). Plutonium is not naturally occurring;
however, trace amounts of
239
Pu are found in naturally occurring uranium ores, but the amounts are in
such small amounts that extraction is not practical (Clark et al. 2006; Lide 2005). Small amounts of
244
Pu
exist in nature from remnants of primordial stellar nucleosynthesis (Clark et al. 2006). Small amounts of
plutonium were produced in natural reactors, such as the Oklo natural reactor in the African nation of
Gabon, which existed about 2 billion years ago (DOE 2005a). The most common form of plutonium
found in the environment is
239
Pu, followed by
240
Pu (DOE 1999a).
Large quantities of plutonium were first produced during the 1940s as part of the Manhattan Project in
order to produce the atomic bomb. Production continued throughout the years of the Cold War (DOE
2005a). The United States built and operated 14 plutonium-production reactors at the Hanford,
Washington and Savannah River, South Carolina sites starting in 1944 and ending in 1988 with the
shutdown of the last reactor. A total of approximately 100 metric tons of plutonium was produced during
this time (DOE 1996b).
The principal plutonium isotopes used in military and nonmilitary applications are
238
Pu and
239
Pu. These
two isotopes are used because of their ease of production and their relatively long half-lives.
238
Pu is used
as a heat source in nuclear batteries to produce electricity in devices such as unmanned spacecraft, and
interplanetary probes (DOE 2005a; Koch 2005).
239
Pu and
240
Pu are produced in nuclear power plants as
a product of nuclear fission as well as in production facilities for use in nuclear weapons.
Possible sources of plutonium to the environment include: past atmospheric weapons testing, accidents
involving weapons transport, accidents involving failed space launches of satellites, operating nuclear
reactors and radioisotope generators, fuel processing and reprocessing activities, and fuel transport
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6. POTENTIAL FOR HUMAN EXPOSURE
Figure 6-1. Frequency of NPL Sites with Plutonium and Selected Isotopes
Contamination
PLUTONIUM
159
6. POTENTIAL FOR HUMAN EXPOSURE
(NEA/OECD 1981). Plutonium is a byproduct of nuclear energy generation. It is produced in uranium-
fueled reactors through neutron capture by uranium-238 (
238
U) (Clark et al. 2006; Koch 2005).
Approximately 1,855 metric tons of plutonium were estimated to exist worldwide at the end of 2003, with
1,370 metric tons found within used fuel from nuclear power plants. A plutonium production rate of 70–
75 metric tons/year was estimated for reactors worldwide at the end of 2003 (Albright and Kramer 2004;
Clark et al. 2006).
The main sources of plutonium in the environment are releases from research facilities, past atmospheric
nuclear weapons testing, waste disposal, nuclear weapons production facilities, and accidents (DOE
1999a). Atmospheric testing of nuclear weapons, which ended in 1980, is the source of most of the
plutonium in the environment worldwide, which released approximately 10,000 kg of plutonium (DOE
2005a). Nuclear reactor accidents (e.g., the Chernobyl reactor in 1986) and other accidents involving
non-U.S. nuclear-powered submarines or nuclear weapons have also released plutonium into the
environment. The total amount of plutonium released during these accidents is small on a global scale as
compared to the amount of plutonium released during atmospheric nuclear weapons testing. Plutonium
released to the atmosphere reaches the earth's surface through wet and dry deposition to the soil and
surface water. Once in these media, plutonium can sorb to soil and sediment particles or bioaccumulate
in terrestrial and aquatic food chains.
6.2 RELEASES TO THE ENVIRONMENT
Concentrations of plutonium are generally expressed in terms of activity, either in the curie (Ci) or the SI
unit, the becquerel (Bq), where 1 Ci=3.7x10
10
Bq=0.037 TBq or 1 Bq=2.7x10
-11
Ci=27 pCi. Activities
may be converted into mass units using the specific activities for each plutonium isotope. Specific
activities for various plutonium isotopes are provided in Table 4-3. Throughout this chapter, the units
used to express concentration or intake of plutonium are generally the same units reported by the authors,
which are followed by converted units in parenthesis. However, in some cases, the units originally
reported by the authors may be converted (e.g., from Bq to mBq or from nCi to pCi) for ease of
comparison of concentrations within a section. Common metric prefixes are provided in Table 6-1.
Possible sources of plutonium to the environment include: atmospheric weapons testing, accidents
involving weapons transport, operating nuclear reactors and radioisotope generators, fuel processing and
reprocessing activities, and fuel transport (NEA/OECD 1981). However, plutonium or plutonium
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