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161
6. POTENTIAL FOR HUMAN EXPOSURE
compounds are listed on the Superfund Amendments and Reauthorization Act (SARA) Section 313 toxic
chemical list and, therefore, are not included in the Toxics Release Inventory (TRI).
6.2.1
Air
The main sources of plutonium in the environment are releases from research
facilities, nuclear weapons
testing, waste disposal, nuclear weapons production facilities, and accidents (DOE 1999a). Areas
contaminated with plutonium, such as the Nevada Test Site or other national facilities, could release
plutonium if the contaminated soils are re-suspended during windy or fire conditions (e.g., Cerro Grande
fire in New Mexico), surface cleanup, construction, vehicular travel,
or other disturbances to the
contaminated soil (DOE 2005b).
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).
Approximately 320 kCi (1.2x10
4
TBq) of
239,240
Pu and 9 kCi (300 TBq) of
238
Pu have been released to the
atmosphere by nuclear tests and distributed worldwide (Eisenbud and Gesell 1997). Concentrations of
transuranics introduced into the environment through underground test venting, accidents involving U.S.
nuclear weapons, and releases during weapon production operations have been negligible in comparison
with those released during atmospheric testing of nuclear explosives in the 1960s (DOE 1980g).
In April, 1964, a Transit Navigational Satellite was launched in California with a payload
that included a
Satellite for a Nuclear Auxiliary Power Generator (SNAP-9A) containing 17 kCi (630 TBq) of
238
Pu. The
rocket system failed and the satellite reentered the atmosphere in the Southern Hemisphere and burned
over the Indian Ocean at an altitude of about 50 km (Harley 1980). The destruction of the SNAP-9A
resulted in the largest single release of
238
Pu to the atmosphere, primarily in the form of very small oxide
particles (Harley 1980). An estimated 37 TBq (1 kCi) of
239,240
Pu was released
during the Chernobyl
accident, April 26, 1986 (Clark et al. 2006). The only area around Chernobyl after the April 1986
accident with plutonium levels exceeding 4 kBq/m
2
was located within the 30-km zone.
239,240
Pu
deposition densities ranged from 0.07 to 0.7 kBq/m
2
in the Gomel-Mogilev-Bryansk area, 200 km north-
northeast of the reactor, and from 0.07 to 0.3 kBq m
2
in the Kaluga-Tula-Orel area, 500 km northeast of
the reactor. At Korosten, located about 115 km southwest of the Chernobyl power plant, the
239,240
Pu
deposition density due to the Chernobyl accident was about 0.06 kBq/m
2
, 4–8 times lower than the
239,240
Pu deposition density from global fallout (UNSCEAR 2000b). Garger et al. (2006) reported that the
PLUTONIUM
162
6. POTENTIAL FOR HUMAN EXPOSURE
total flow of activity through the gaps of the shelter of the Chernobyl reactor measured during 1996–1999
was 8.64x10
9
Bq/year (0.234 Ci/year); 0.4% of this was due to
239,240
Pu.
Research facilities and plants have also released plutonium to the atmosphere. For example, the
Department of Energy (DOE) Mound
Plant in Miamisburg, Ohio, released about 30 Ci (1x10
12
Bq) to the
atmosphere from the beginning of its operation through 1976 (NEA/OECD 1981). The vast majority of
these releases occurred in the 1960s. By 1972, total
238
Pu air releases were about 0.1% of the quantity
released in 1967, and they have been much lower than that in the years since 1972 (Agency for Toxic
Substances and Disease Registry 1998). A commercially operated reprocessing plant in West Valley,
New York, has reportedly released 5x10
-3
Ci (2x10
-8
Bq) of plutonium to the atmosphere over the course
of 6 years (NEA/OECD 1981). The Savannah River Site, which produced plutonium and tritium as well
as
other nuclear materials, released 1.4x10
11
Bq (3.8 Ci) of plutonium to air during the period of 1954–
1989 (Carlton et al. 1996). An estimated total air emissions from the Nevada Test Site (NTS) of 0.29 Ci
(1.1x10
10
Bq)
239,240
Pu was reported for calendar year 2004 (DOE 2005b). Air samplers in two areas of
the NTS showed that
239,240
Pu is routinely detected due to blowing contaminated soil; however,
concentrations are only slightly above minimum detectable concentrations. Air sampling in the past has
shown that
238
Pu is not detected in air at the NTS (DOE 2005b).
Small amounts of various long-lived radionuclides, including
238
Pu,
239,240
Pu, and
241
Pu, are still released
to the environment through state and federally permitted release points at the Hanford Site. Generally, the
radionuclide emissions in these releases are near concentrations that are indistinguishable from
background radionuclide concentrations that occur naturally or are from fallout (DOE 2005c). From 1994
to 2004,
releases of
239,240
Pu to air from the Hanford Site ranged from 6x10
-4
Ci (2x10
7
Bq) in 1998 to
1x10
-4
Ci (4x10
6
Bq) during 2002–2004. During 2004, releases of
238
Pu to air ranged from 1.1x10
-8
to
2.7x10
-6
Ci (407–1.0x10
5
Bq) in three areas at the Hanford Site. Releases of
241
Pu to air were
1.5x10
-4
and 5.3x10
-4
Ci (5.6x10
6
and 2.0x10
7
Bq) at two areas, and not detected at two other areas.
Releases of
239,240
Pu, which included gross alpha data, ranged from 1.4x10
-7
to 6.7x10
-5
Ci (5.2x10
3
–
2.5x10
6
Bq) at five areas at the Hanford Site during 2004 (DOE 2005c).
Plutonium has been identified in 9 air sample collected from 1,689 current or former NPL hazardous
waste sites where it was detected in some environmental media (HazDat 2007).