Depleted Uranium
Technical Brief
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Depleted Uranium
Technical Brief
EPA402-R-06-011
December 2006
Project Officer
Brian Littleton
U.S. Environmental Protection Agency
Office of Radiation and Indoor Air
Radiation Protection Division
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Ill
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FOREWARD
The Depleted Uranium Technical Brief is designed to convey available information
and knowledge about depleted uranium to EPA Remedial Project Managers, On-Scene
Coordinators, contractors, and other Agency managers involved with the remediation of
sites contaminated with this material. It addresses relative questions regarding the
chemical and radiological health concerns involved with depleted uranium in the
environment.
This technical brief was developed to address the common misconception that
depleted uranium represents only a radiological health hazard. It provides accepted data
and references to additional sources for both the radiological and chemical
characteristics, health risk as well as references for both the monitoring and measurement
and applicable treatment techniques for depleted uranium.
IV
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Acknowledgments
This technical bulletin is based, in part, on an engineering bulletin that was prepared by the U.S.
Environmental Protection Agency, Office of Radiation and Indoor Air (ORIA), with the assistance of
Trinity Engineering Associates, Inc. (TEA) under Contract No.68-D-00-210, and EnDyna, Inc. under
Contract No. 06-H-00-1057.
Thanks go to Ron Wilhelm, Madeleine Nawar and Schatzi Fitz-James of ORIA, and Charles
Sands, Stuart Walker, Robin Anderson, and Kenneth Lovelace of OSWER for their comments and
suggestions and to the following EPA regional staff: R2: Angela Carpenter; R3: Randy Sturgeon; R4:
David Dorian; R6: Camille Hueni, Raji Josiam and George Brozowski, RIO: Rick Poeton.
This document has been changed from the original publication dated December 2006. This version
corrects references in Appendix 1 that improperly identified the content of Appendix 3 and Appendix 4.
The document also clarifies the content of Appendix 4.
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TABLE OF CONTENTS
1. PURPOSE 1
2. INTRODUCTION 1
2.1 Characteristics of Uranium and Depleted Uranium 1
2.2 Health Concerns 2
2.2.1 Exposure Pathways 2
2.2.2 Chemical Risk 3
2.2.3 Radiological Risk 3
3. URANIUM IN THE ENVIRONMENT 4
3.1 Occurrence 4
3.2 Geochemistry 4
3.3 Mobility 4
3.4 Enhanced Mobility 4
4. FATE AND TRANSPORT OF DEPLETED URANIUM 5
4.1 Fate in Soil 5
4.2 Fate in Water 6
4.3 Fate in Air 6
4.4 Fate in Biota 7
4.5 Partition Coefficients 7
4.6 Fate and Transport Modeling 7
5. SITE SCREENING FOR DEPLETED URANIUM CONTAMINATION 8
6. MEASUREMENT TOOLS AND MONITORING TECHNIQUES 9
7. REMEDIATION TECHNOLOGIES 9
7.1 Soil Technologies 9
7.1.1 Physical Separation 9
7.1.2 Chemical Extraction 10
7.2 Groundwater Technologies 10
7.2.1 Pump and Treat 10
7.2.2 Permeable Reactive Barriers 10
7.2.3 Commercial Test Studies 10
7.3 Technologies for Soil and Water. 11
7.3.1 In-Situ Stabilization/Treatment 11
7.3.2 Phytoremediation 11
7.3.3 Monitored Natural Attenuation 11
8. EPA STANDARDS APPLICABLE TO DEPLETED URANIUM SITES 12
8.1 For Soil 12
8.2 For Air 12
8.3 For Water 12
8.4 Storage of Depleted Uranium 12
8.5 For Disposal 13
Acronyms 14
Glossary 15
Additional Sources of Information 17
Appendix 1: Technical Background on Uranium and Depleted Uranium 19
Appendix 2: Measurement Tools and Monitoring Techniques 23
Appendix 3: National Priorities List (NPL) Sites that have or may have DU Contamination 28
Appendix 4: Depleted Uranium Manufacturing and Testing Facilities 30
Appendix 5: Case Study - Nuclear Metals, Inc. (NMI) site, Concord, Massachusetts 32
Appendix 6: Case Study - Maxey Flats Nuclear Disposal Site, Hillsboro, Kentucky 35
Appendix 7: Treatment Defined by NCP 37
References 38
VI
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1. PURPOSE
Technical Briefs are d esigned to convey
available information and knowledge about a
particular c ontaminant of interest, such as
depleted uranium (D U), to the Environm ental
Protection Agency (EPA) Remedial Project
Managers (RPM), On-Scene Coordinators
(OSC), contractors, and other site cleanup
managers involved with the remediation of sites
contaminated with radioactive material.
This Technical Brief i s intended to help the user
understand t he characteristics, behavior in the
environment, and potential human health risks of
DU as a contaminant in soils and grou ndwater.
The document also identifies a vailable
monitoring and measurement tools and various
treatment technolo gies for rem ediation of sites
contaminated with DU. Supplem entary
discussions and additional information are
provided in the appendices.
This Technic al Brief spe cifically addresses D U
in an environmental contam ination setting and
specifically does not consider airborne DU
micro-particulates of the type associat ed with
DU munitions. Further, it considers onl y
contamination scenarios in the United States,
though it has used international scientific data,
where appropriate, for its technical basis. In
these environmental contamination sett ings, the
major risk from DU is toxicological rather than
radiological, and chem ical toxicity is the major
driver for site cleanup.
Further, since most available literature
concerning chemical properties of uranium focus
on natural uranium , this docum ent will make
frequent reference to t hese studies in full
knowledge that the chem ical properties
addressed fo r natural uranium ar e ide ntical to
those of DU. Adden da will be issued
periodically to update th e original Technical
Brief, whenever deemed necessary.
2. INTRODUCTION
Depleted uranium (DU) is a by product of the
process used to enrich natural uranium for use in
nuclear reactors and in nuclear weapons. Natural
uranium is c omposed of three isotopes; 234U,
235U, and 238U (see Table 1) [1]. The enrichment
process concentrates both the 235Uandthe 234U
isotopes in the product material, resulting i n a
waste product or byproduct depleted in both 235U
and 234U. The resultant DU retains a smaller
percentage of 235U and 234U, and a slightl y
greater percentage of 238U (99.8% by mass
instead of 99.3%). Because of the shorter half-
life of 234Uand 235U compared to 238U,the
radioactivity associate d with DU i s
approximately 40% less than that o f natural
uranium.
Table 1: Typical Isotopic Abundances in Natural
and Depleted Uranium
Isotope
Abundance (by weight)
234U
235U
238U
Natural Uranium
0.0058%
0.72%
99.28%
Depleted Uranium
0.001%
0.2%
99.8%
In the Unite d States, DU is available mainly
from the U.S. Department of Energy (DOE) and
other govern ment sources. DU occurs in a
number of different co mpounds with different
characteristics, which may have a si gnificant
impact on the management and dispo sition of
this material.
Because DU metal is 1.7 times more dense than
lead, it is va luable for industrial uses. It has
been used f or civil and military purposes for
many years. Detailed information on uranium ,
its che mical form s, manufacturing/enrichment
processes, and uses of DU are further d iscussed
in Appendix 1.
2.1 Characteristics of Uranium and
Depleted Uranium
Uranium is a naturally occurring radioactive
metal in all rocks and soils in low concentrations
(1 to several hundred picocuries per gram
(pCi/g)). All three isotopes are radioa ctive and
produce decay product s upon radioactive
disintegration. After purification (processing) of
uranium, the decay products of all of the
uranium i sotopes will beg in to accu mulate very
slowly, and traces of thes e decay products can
be detected.
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Other trace i sotopes that have been observed in
depleted uranium , an d are likely of
anthropogenic origin, in elude pluton ium-238
(238Pu), plu tonium-239 ( 239Pu), plu tonium-240
(240Pu), americium-241 (241Am), neptunium-237
(237Np) and technetium-99 (99Tc).
Table 2: Radiological Properties of Uranium
Isotopes
Isotope
Half-life (years)
234U
235U
238U
2.455
7.038
4.468
105
108
109
Table 2 above lists the hal f-life of each isotope.
Approximately 48.9% of the radioactivit y of
natural uranium is associated with 234U, 2.2% is
associated w ith 235U, and 48.9% is a ssociated
with 238U. All three isotopes behave the same
chemically but have different radiolog ical
properties. As may be calculated from the tables,
the radioactivit y of natural uranium is
approximately 0.7 0 uCi/g, whereas the
radioactivity of DU is approximately 0.40 uG/g.
The weight percentages in Table 1 and
radioactivity percentages given previ ously are
different bee ause each i sotope has a different
physical half-life - the shorter half-life makes
234U the most radioactive and the longer half-life
makes 238U the least radioactive. Each isotope
decays by emitting an alpha particle.
For natural uranium present in soils and rocks,
the activities of 234U and 238U are identical; they
are said to be in secular eq uilibrium. In natural
waters, how ever, the 234U can appear to be
slightly more soluble and the radioactivity ratio
of 234U to 238U varies from 1:1 to m ore than
20:1. This is believed to be due to the fact that as
238U decay s to 234U, it passes through t horium-
234 ( 234Th) ( first decay product) and then
protoactinium-234 ( 234Pa) ( second decay
product) which are slightly m ore soluble than
the uranium isotopes. The 234U thus appears to
move while the 238U remains sparingly soluble.
When converting from activity to m ass or vice
versa, knowledge of the concentration of each
the three uranium isotopes is required.
2.2 Health Concerns
A common misconception is that radiation is the
primary hazard DU poses to hum an health. This
is not the case under most exposure scenarios.
Though irradiation from DU can occur, chemical
toxicity is usually the major hazard from soluble
forms of uranium, while the radiological hazard
dominates inhalation of sparingly soluble forms.
Since all for ms of urani um posses s the sa me
inherent chemical properties, they also displa y
the same behaviors of chemical toxicit y, and if
internalized, will all le ad to adverse health
effects si milar to those of other heavy m etals
such as 1 ead and cad mium. The Age ncy for
Toxic Substances and Diseas es Registry
(ATSDR) To xicological Profile on uranium [1]
summarizes the existing a nimal and human data
on the toxicology of natural uranium.
Natural and depleted uranium differ only in their
relative concentrations of uranium isotopes.
Depleted uranium is roughly 60% as radioactive
as natural uranium because the more radioactive
isotopes have been removed. All three naturally
occurring uranium isotopes emit alpha particles
as their primary radiation. Because alpha
particles cannot penetrate the skin, ur anium is
usually considered an internal radiological
hazard rather than an exte rnal radiation hazard.
Awareness should be m aintained regarding the
external hazard since DU can contain trace
amounts of 236U and other substances (such as
plutonium, am ericium, and technetium);
however, the risk posed by these trace
contaminants is usually regarded as
insignificant.
2.2.1 Exposure Pathways
Uranium occurs widely in the environment, and
asaconseq uence small am ounts of natural
uranium in air, water, and soil are ingested and
inhaled every day. This normal intake results in
a natural level of uranium in the body of
approximately 90 ug [1]. Excess loading occurs
through thre e exposure p athways - i nhalation,
ingestion, and dermal contact - thoug h the latter
(dermal) i s usually considered to be an
insignificant exposure scenario.
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Inhalation is the m ost likely route of i ntake of
DU. In the case of sites c ontaminated with DU,
this may occur through resuspensio n in the
atmosphere t hrough wind or dust disturbances
due to site operations. Accidental inhalation may
alsooccurasa consequence of fire in a DU
storage facility, an aircraft crash, manufacture of
armor-piercing weapons, or the decontamination
of contaminated objects. [34]
Ingestion can occur in a large s ection of a
community o r populatio n if drinkin g water or
food supplies become contaminated with DU. In
addition, in gestion of soil b y chi Idren is
considered a potentiall y significant pathway
[34].
Dermal con tact is considered a r elatively
unimportant type of expos ure since little of the
DU will pass across the skin int o t he blood.
However, D U could ente r sy stemic ci rculation
through ope n wounds or from embedded
fragments of DU [34].
2.2.2 Chemical Risk
When incorporated into the body , the highest
concentrations of uranium occur in the kidne ys,
the m ost sen sitive organ, as well as liver tissue
and skeletal structure. The am ount of DU
subsequently absorbed into the b lood and
deposited in the kidne ys or other organs is
dependent u pon several factors (e.g., exposure
pathway, particle size, solubility) [ 1]. DU
particles and oxides retained in the body have
different solubilities. The three uranium oxides
of prim ary c oncern (UO 2, UO 3, and U 3O8) are
relatively insoluble [35]. Insoluble and sparingly
soluble uranium compounds are believed to have
little potential to cause renal toxicit y but could
cause pulm onary toxicit y throu gh i nhalation
exposure [1].
The ingestion exposure pathway currently has a
number of established risk levels and standards
for chem ical toxicit y. ATSDR has a "minimal
risk" level for intermediate-duration ingestion
set at an oral uptake of 2 (ig of uranium per kg
of bod y weight per day , though the World
Health Organization (W HO) has established a
tolerable daily intake (TDI) for uranium of 0.6
(ig/kg bod y weight per day . WH O has a
provisional guideline for drinking water quality
of 15 (i g/L - a value considered to be protective
for sub-clinical renal effects repo rted in
epidemiological studies. EPA's Rule on
Radionuclides in Drink ing Water sets a
maximum contam inant level for naturally
occurring uranium at 30 (i g/L, and its
preliminary remediation goal (PRG) for
Superfund is 2.2 2 (i g/L for 238U in tap water.
The Nucle ar Regulat ory Commission' s
occupational annual lim it on i ntake ( ALI) for
oral ingestion is 14.8 mg.
2.2.3 Radiological Risk
The general populati on is exposed to uranium
primarily th rough fo od and water with an
average annual intake from all dietary sources
being abo ut350 pCi [31]. On average,
approximately 90 |o,g (m icrograms) of uranium
exists in the human body from natural intake of
water, food, and air. About 66% is found in the
skeleton, 16% in the liver, 8% in the kidne ys,
and 10% i n other tissue s [ 32]. Inth e United
States, the typical concentration of uranium in
the skeletal structure (wet weight) is about 0.2
pCi/kg [31]. The lungs , kidne ys, a nd bo ne
receive the highest annual doses of radiation
from uranium, estimated at 1.1, 0. 92, and 0.6 4
mrem, respectively, for U.S. residents.
As they decay, DU and its decay products e mit
alpha, beta, and gamma radiation that can result
in external and internal exposure to those who
handle or encounter DU-contaminated materials.
Based on the zero-threshold linear dose response
model, any absorbed dose of uranium is
assumed to result in an in creased risk of cancer.
Since uranium tends to c oncentrate in specifi c
locations in the body , the risk of cancer of th e
bone, liver, and bloo d (such as leukemia) may
be increased.
Inhaled DU particles that reside in the lungs for
long periods of time may damage lung cells and
increase the possibility of lung cancer after
many years. D U is co nsidered primarily an
internal hazard, although there is some external
radiation hazard associ ated with DU since it s
progeny emit gamma rays.
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The amount of uranium in the air is usually very
small and effectively insignificant for re medial
operations. People who live near federal
government facilities that produced or tested
nuclear weapons in the p ast, or facilities that
mine or proc ess uranium ore or enrich uranium
for reactor fuel, may have increased exposure to
uranium. For exam pie, d ata fro m the United
States and Canada have shown elevated uranium
levels in and around m illing and processing
facilities, and esti mated airborne releases of
uranium at one DOE facility am ounted to
310,000kg between 195 1 and 1988, which
produced an estim ated offsite inven tory of
2,130-6,140 kg of excess uranium in the top 5
cm of soil in the vicinity of the facility [34].
3. URANIUM IN THE ENVIRONMENT
Due to its natural abund ance, uranium can be
found an ywhere in water, in food, and air.
Because DU and naturally occurring uranium
are chem ically the same, knowledg e about
transformation, transport, fate and effect on
natural uranium in the environment is applicable
to the study of DU.
3.1 Occurrence
As an environm ental conta minant, DU m ost
frequently occurs as the metal, and as a num ber
of solid oxides, which may include those arising
from oxidation of the metal, those fro m
hydrolysis of uranium hexafluoride accidentally
released to the environm ent, and those fro m
neutralization of acidic industrial wastes that
contain dissolved DU. 11 can also o ccur a s
soluble aqueous species (primarily the urany I
ion) or as a number of in soluble and sparingl y
soluble species, including mineral for ms that
have aris en as are suit of uranium 's complex
environmental chemistry.
3.2 Geochemistry
Oxidation-reduction processes play a major role
in the occurrence and behavior of uranium in the
aqueous envi ronment. The dom inant uranium
valence st ates that ar e st able in the geologic
environment are the uran ous (U 4+), and uran yl
(U6+, UO22+ ion) states; the former is m uch less
soluble [ 2] while the latter can form many
complexes and is regarded as a dominant feature
of uranium chem istry. For the metal, the
oxidation rat e is likel y to be contr oiled by
variables sue h as te mperature, metal size and
shape, prese nee or absence of coatings, soil
matrix, and presenc e of water a nd other
contaminants.
3.3 Mobility
Uranium transport generally occurs in oxidizing
surface water and groundwater as the urany I ion,
UO22+, or as urany I fl uoride or c arbonate
complexes. UO 22+ and uran yl fluori de
complexes dom inate in acidic oxidizing acidic
waters, whereas the carbonate com plexes
dominate in near-neutral and alkaline oxidizing
waters, respectively . In contrast, the uranous
ion, U4+, is essentially ins oluble. An im portant
point in cons idering urani um migration in soils
is that when UO 22+ is reduced to U 4+ by humus,
peat, or other organic matter or anaerobic
conditions, it is essentially imm obilized. It
should also be noted that phosp hates and
sulfides usually precipitat e uranium and hence
stop migration, a behavior that can be exploited
in remedial operations.
Hydroxyl, silicate, organic, and sulfate
complexes might also be i mportant, sulfat e
especially in mining and milling operations that
use sulfuric acid as a leaching agent. Maxi mum
sorption of uranyl ions on natural materials (e.g.,
organic matter; iron, m anganese and titaniu m
oxyhydroxides, zeolites, and clay s) occurs at a
pHofS .0-8.5. The sorption of uranyl ions by
such natural media appears to be rever sible. For
uranium to be "fixed" and therefore ace umulate,
it requires reduction to U4+ by the substrate or by
a mobile phase, such as hydrogen sulfide (H2S).
3.4 Enhanced Mobility
A further complication in predicting the mobility
of DU is the existence of facilitated transport.
Facilitated transport is the accelerated movement
of contaminants in an aqu eous system at a rate
greater than would be pr edicted by e ither the
simple solubility of the contaminant, the form al
flow-rate of the aqueous phase, or by the
interaction of a contam inant with the solid
phases present. Facilitated transport is usually
attributed to the contam inant being b ound to
particles such as colloids , or havi ng enhanced
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solubility due to the presence of co mplexants,
ligands, and/ or chelators. While the aqueous
phase in gen eral may be able to explore a very
tortuous path through the geologic m edia when
contaminant attached to a particle that is too
large to travel through the smaller pathways, it is
effectively restricted to wider cr acks and
crevices, thus giving it an enhanced m obility.
Colloids are ty pically ti ny (spanning the size
range from 1 arge molecules to s mall biological
entities such as bact eria) particles of mineral
and/or organic matter that can remain suspended
in the aqueous phase without settling. They may
be hydrol y sis products of uranium , organic
chelates (natural and anthropogenic lig ands), or
mineral/oxide/humic colloids.
4. FATE AND TRANSPORT OF
DEPLETED URANIUM
Environmental contam ination b y DU can occur
in soil, water, biota, and as airborne particles.
Although the radiological properties of uranium
isotopes differ considera bly, their c hemical
behavior is essentially identical. Hence,
knowledge about the transform ation, transport,
fate, and effect of natural uranium in the
environment is applicable to DU.
Under some conditions, such as the reducing
conditions characteristic of swamps and
wetlands, the stable chemical form of uranium is
the +4 state i n which it will not readil y dissolve
in water, and will thus beco me relatively
immobile. Under oxidizing conditions, such as
on the surface of the ground or in shallow water,
DU oxidizes to a st ate in which it c an dissolve
and become m obile in water. Metall ic form s
will oxidize faster as small particl es than as
large pieces [37].
Aside fro m pH, a num ber of ot her pa rameters
affect uranium fate and transport . Other
parameters that influence movement are the
presence (or absence) of organic com pounds,
redox status, ligand concentrations (i.e.,
carbonate, fluoride, sulf ate, phosph ate, and
dissolved carbon), alum inum- and iron-oxi de
mineral concentrations, and uranium
concentrations.
Given the long half-life of uranium (see Table
2), decay is not particularly relevant to uranium
fate and transport in th e environm ent. The
following sections discuss DU fate/transport by
medium.
4.1 Fate in Soil
Upon weathering, n on-oxidized sm all particles
maybeadso rbedto clay minerals and hum us.
The surfaces of remaining DU fragments in soil
exposed to the atmosphere will slowly oxidize to
uranium oxides.
Uranium can exist in the +3, +4, +5, and +6
oxidation states. The +4 and +6 stat es are the
most common in the environm ent. These oxides
are onl y sparingl y sol uble, but will gradually
form hy drated uranium oxides in moist
conditions. The hy drated uranium oxi des will
then slowly dissolve and be transported into the
surrounding soil, pore water, and ev entually
groundwater, although adsorption of uranium to
organic co mpounds in th e soil may inhibit the
rate of migration. It should be noted that the +6
form (uranyl ion) can be adsorbed on clay s and
organic compoun ds and later be "eluted" or
displaced by other cations. However, many
organic mate rials reduce t he urany I ions to the
+4 form s w hich are not likely to be eluted,
though t hey might be su bsequently r eoxidized
and made soluble.)
In the case of metallic p articles, the oxidation
rate depends on fragment size, pH, humidity,
soil m oisture content, soil chem istry, soil
oxygen content, and the presence of other metals
in the soil. The sy stem's pH and dissolved
carbonate concentrations are the two m ost
important factors influen cing the ad sorption
behavior of U6+ in soil [38].
Iron and manganese oxides, smectite cl ays, and
naturally occurring organi c matter can act as
somewhat irreversible sinks for uranium pres ent
in soils. As a result, so rption ont o iron and
manganese oxides can be an effective extraction
process, alth ough the pr esence of d issolved
carbonate can inhibit thi s process. Uranium
transfer between these bound phases and the
dissolved phase is subject to very slow reaction
rates [38].
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Aqueous pH influences the sorption of U6+ to
solids. The poorer-adsorbing uranium species
are most likely to exist at pH values between 6.5
and 10. Additionally , lowering the pH reduces
the num ber of available exchange sites on
variably charged surfaces, such as iron oxides
and natural organic matter.
Microbial activity might speed up the corrosion
of metallic DU, but it should be noted that the
titanium present in DU of m ilitary origi n
(typically 3.5%) would tend to cou nteract and
slow down the process [39]. On the other hand,
in soil with high concentrations of organic
materials, naturally occurring soil bacteria can
reduce soluble U 6+ to sparingl y sol uble U 4+,
thereby lim iting uranium mobility as well.
Oxygen content, presence of water, si ze of the
metal particles, presence of protective coatings,
and the salinity of the water present al 1 impact
the rate of microbial action. Althou gh it is
known that o rganic matter is a sink for uranium
in soils and sedi ments, the actual mechanism of
the process is still unclear [38].
4.2 Fate in Water
U4+ solid phases have relatively low solubilities,
so the total concentration of U 4+ in water is
usually low (3-30 m g/L) [ 38]. In general,
aqueous U4+ forms precipitates that are sparingly
soluble, adso rbs strongl y to m ineral surfaces,
and partitions into organic matter. All of these
properties lead to its reduced mobility in water.
Under reducing condi tions, U4+ is the dom inant
oxidation state in aqueous solutions. Reducing
conditions are found in deep aquifers, marsh
areas, and e ngineered barriers. U 4+ is not
strongly co mplexed by co mmon inorganic
ligands and is present predominantly as the
U(OH)4 ion under pH conditions typical of most
natural waters. U 4+ precipitates t o form
relatively insoluble solids, such as uraninite
(UO2) and coffmite (USiO4) [40].
As previously m entioned, the U 6+ ions can b e
removed from solution by sorpti on on ir on
hydroxides and organic soil matter. Sorbed
uranyl ions can be reduced to U 4+ by reductants
such as hydrogen sulfide (H2S), methane (CH4),
or ferrous iron (Fe 2+). If urany 1 ions are sorbed
by or ganic matter, the organic m after may
reduce the urany 1 i ons [ 40]. Urany 1 ions may
also be rem oved from solution by precipitation
as U 6+ solid phases such as schoepite ( 3-
UO3«2H2O), which is relativel y solubl e, or by
precipitation of the less so luble phases carnotite
(K2(UO2)2(VO4)2) or tyuyamunite
(Ca(U02)2(V04)2) [40].
Uranyl ions form stro ng com plexes with
carbonate ion in solution. T hese carbonate
complexes i ncrease the solubility of uranium
solids, facilitate U 4+ oxi dation, and increase
uranium mobility by lim iting uranium sorption
in oxid ized waters [40]. Fluoride, p hosphate,
and sulfate ligands can also sig nificantly
complex uranyl ions [40].
6+ •
IS
At low ionic strengths with low concentrations
of U 6+, the concentration of dissolve d U
mostly cont rolled bye ation exchange and
adsorption processes. As the ionic strength of a
solution increase s, other cations (e. g., Ca 2+,
Mg2+, K +) displace any uranyl ions on soil
exchange sites and force them b ack into
solution.
4.3 Fate in Air
Atmospheric release s of DU are aim ost
exclusively in particulate form, as the vapor and
gas forms of DU are not commonly encountered.
The high density of DU in m ost particulate
forms limits the air transport of DU to relatively
small particles. Airrel eases of DU can occur
via em ission from stacks, re-suspension from
soil, or through em issions of fugitive dust fro m
piles or industrial process areas containing DU.
Source estimates for stack releases are generally
derived from stack monitors. The revis ed wind
erosion equation [ 41] may be used to estimate
releases via suspension from soil. So urces of
fugitive dust releases to ai r are often esti mated
using the E PA AP-42 guidance [ 42]. Air
transport of long-term ( Bone y ear) release s o f
DU in the form of aerosols or other respirable
particle si zes is ty pically analy zed using codes
based on the G aussian plume model. Thes e
models estimate air concentrations as a function
of direction and distance from the so urce, and
also will usually provide esti mates o f ground
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concentrations resulting from deposition of the
airborne DU. It is reported that m ost of the DU
dust will be deposited within a distance of 100
meters from the source [43].
Following airborne transp ort, the m igration of
DU will ultimately become subject to water,
soil, and bi ological transport mechanism s. In
general, DU deposited by airborne transport will
be present on or near the s oil surface and shows
minimal uptake b y p lant roots. D U is not
effectively tr ansported thr ough the fo od chain,
as low-level organism s tend to exc rete the
soluble uranium species quickly.
4.4 Fate in Biota
Some plant materi al, such as lichens, can serve
as an indicator of airborn e DU contamination.
Lichens consist of fungi and algae living
together sy mbiotically, in a mutually beneficial
way. As lich en morphology does not vary with
the seasons, their accumulation of pollutants can
occur throughout the year, and the y usually live
for very long periods.
Some lichens growing on the surface of another
plant have a high capacity to accu mulate
uranium. Because they lack roots, lichens do not
have access to soil nutrient po ols and
accumulate substances mainly via trapping
atmospheric particulates. Ura nium is
accumulated in lichen thallus under moist and
dry conditions from airborne particles and d ust.
Even tin y fr agments of lichens may contain
concentrations that are readily detectable [43].
4.5 Partition Coefficients
Partition coefficient (K d) is a parameter used
when esti mating t he m igration potential of
contaminants present in aqueous solutions in
contact with surface, subsurface, and s uspended
solids. K d is defined as the ratio of the
contaminant concentration associ ated with the
solid to the contain inant concentration in the
surrounding aqueous solution when the sy stem
is at equilibr ium. Gene ric or default partition
coefficient values found i n literature can result
in significant errors when used to pre diet the
absolute im pacts of conta minant migration or
site-specific remediation options. Partition
coefficient values m easured at site-specific
conditions are essential for sit e-specific
calculations [44].
With respect to uranium movement in the
environment, however, the EPA guidance on K d
suggests that the best way to m odel the
concentration of precipitated uranium is through
the solubility constants of the different uranium
compounds i nvolved, rat her than thr ough K d
[44].
As with other uranium properties, uranium K d
values are strongly influenced by pH because of
the pH-dependent surface charge properties of
soil m inerals and the com plex aqueous
speciation behavior of dissolved U6+. In general,
at pH less than 3, the adsorption of ur anium by
soils and single-m ineral phases in carbonate-
containing aqueous solutions is low, reaching a
maximum in adsorption between pH 5-8, then
decreasing at pH values greater than 8 [44].
Table 3 provides minimum and maximum K d
values for u ranium as a functio n of pH and
shows the wide variation that occurs in Kd.
4.6 Fate and Transport Modeling
Obviously, the best method for determ ining the
concentration of a contaminant at a location in a
contaminated site i s by direct, sit e specific
measurement using the appropriate analy tical
method and protocol. The contain inant
concentration is then us ually used t o determine
Kd for further modeling purposes. The use,
advantages, and lim itations of the K d approach
have been well discussed in the literature [43 ],
and we recommend that whenever possible Kd
should be measured. It is im portant to n ote that
soil scientists and geochemists knowledgeable of
sorption processes in natural environm ents have
long known that generic or default partition
coefficient v alues found in the literature can
result in significant errors when used t o predict
the absolute impacts of c ontaminant migration
or site-remediation options. Accordingly, one of
the major reco mmendations is that for site-
specific calculations, partition coefficient values
measured at site-speci fie conditions are
absolutely essential [43 ]. However, due to the
complexities of both geological media and
chemical behavior withi n this media, the
necessary measurements of conta minant
concentration may not be possible. For example,
at a given point in a geological matrix, a
contaminant will be partitioned bet ween th e
-------
groundwater and the host geological matrix, and
a "true" measurement at that point requires
removal of a sam pie containing b oth the solid
and aqueous phase; this may not always be easy
to achieve. Ifsuchproble ms are the c ase, or if
the contam inant has not y et reached exposure
points, environmental fate and transport models
must be used to predict conta minant
concentrations.
Table 3: Kd Values for Uranium as a Function of
PH
PH
o
J
4
5
6
7
8
9
10
Kd (mL/g)
Minimum
<1
0.4
25
100
63
0.4
<1
<1
Maximum
32
5,000
160,000
1,000,000
630,000
250,000
7,900
5
Source: [44- Table 5.15]. (See also reference 43, Table 5.18
and pages 5.79-5.81)
While m any fate and transport m odels are
available for various media, this t ype of
modeling is an area of active research with much
debate on the problem s associated with existing
models and little consensus on how chem ical
reactions an d reaction parameters sh ould be
determined for field a pplications. The Federal
Interagency Steering Committee on Multimedia
Environmental Models (ISCMEM) exists to
coordinate efforts am ong agencies that actively
use or supp ort the deve lopment of coupled
hydrologic and geochem ical models to si mulate
the transport of chem ical contam inants in the
subsurface environment.
Fate and transport modeling is of great
importance i n radiation risk asse ssments and
conceptual site models required for remediation,
and considerable i mportance is attach ed to the
availability of expertise in their use.
5. SITE SCREENING FOR DEPLETED
URANIUM CONTAMINATION
EPA has published several guidance do cuments
on the approach for re mediation of sites
contaminated with hazardous materials,
including radionucli des. Because of the
complexity and com prehensiveness of the
subject matter, the reader is advised to consult
the relevant details in the f ollowing
documents/websites:
1. "Distribution of OSWER Radionuclide
Preliminary Remediation Goals (PRGs) for
Superfund Electronic Calculator", February 7,
2002.
httD://eDa.aov/suDerfund/resources/radiation/i
df/rad.pdf
2. Soil Screening Guidance, User's Guide,
2nd Edition 9355.4-23, 1996. This Guide [3]
provides a methodology to calculate risk-
based, site-specific soil screening levels
(SSL).
3. Soil Screening Guidance for Radionuclides:
Technical Background Document, EPA/540-R-
95/128, 1996 [4], and Soil Screening
Guidance for Radionuclides: User's Guide,
EPA/540-R-00-007, 2000 [5].
4. EPA website,
http://www.epa.gov/radiation/radionuclides/ura
nium.htm
5. Inventory of Radiological Methodologies
for Sites Contaminated with Radioactive
Materials, EPA/402-R-06-007, 2006 (See
Table 10, page 42, for analytical
methodologies applicable to each
radionuclide, and Section 3.2.1 for discussion
of water sample preservation and transport
issues).
It should be noted that information on the
chemical toxicity of urani um is av ailable in the
ATSDR Toxicological Profile for Uranium [ 1 ].
It should also be noted that since uranium,
including DU, is both a chemical and
radiological hazard, SSLs for DU should
consider both types of hazards. SSLs for
uranium should be calculated using both the Soil
Screening Guidance for non-carcinogenic
chemicals and the Soil Screening Guidance for
Radionuclides. Since the SSL is a numerical
concentration, it should be based on t he most
protective health quantity, whether that is kidney
toxicity or radiological risk.
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6. MEASUREMENT TOOLS AND
MONITORING TECHNIQUES
Uranium and DU can be detected by measuring
the different types of radi ation (i.e., al pha, beta
and/or gamma radiation) em itted. Presently , a
vast choice of equipm ent for monitoring such
radiation is available. Refer to Table 6,
Appendix 2, for a description of selected
specific measurement tools and monitoring
techniques.
Measurements made with field equipment are
typically less sensitive than laboratory
measurements and m ay be im paired b y
environmental characteristics such as natural soil
composition. If these fi eld measurements ar e
not, or are only partly , successful, field sa mples
must be collected and analyzed in a laboratory in
order to obtain a com prehensive asse ssment of
the contamination.
EPA's Office of Radiation and Ind oor Air
completed a draft compendium on the Inventory
of Radiological Methodologies, focusing on the
radionuclides likely to be found in soil and water
at contaminated sites. While it is not a com plete
catalog of analy tical methodologies, it is
intended to assist pr oject managers to
understand the concepts, requirements, practices,
and limitations of laboratory analyses unique to
radioactive environm ental samples. Detailed
guidance o n reco mmended radioa nalytical
practices may be found in current editions of the
Multi-Agency Radiol ogical Laborator y
Analytical P rotocols Manual (MARLAP) [ 6]
and the Multi-Agency Radiation Survey and Site
Investigation Manual (MARSSIM) [7].
7. REMEDIATION TECHNOLOGIES
Technologies for the remediation of DU
contamination may involve one or more of the
following process es: ex cavation and earth
moving, ph ysical separation, chem ical
separation, in-situ stabilization, or a combination
of these tech nologies. Re mediation of surface
and grou ndwater contain inated with DU may
include conv entional pum p and treat methods
and/or permeable reactive barriers . These
technologies are described in t he f olio wing
subsections [8]. However, no technologies exist
that are c apable of significantly reducing the
chemical an dradiolog icaltoxicit y ofDU,
characteristics also fundam ental to natural
uranium. Case studies of the rem ediation efforts
of two sites with DU contain ination, Nuclea r
Metals, Inc. in Concord, Massa chusetts, and
Maxey Flat s in Hillsb oro, Kentucky , are
provided in Appendix 5 and 6. It should be
noted that the following descri ptions of
remediation technologies are brief and serve
only as a guide for furt her investigation and
analysis. The evaluation and sel ection of a
remediation technolog y can be a co mplex
matter; critical issues incl ude the phy sical and
chemical fo rms of the depleted uranium
contaminant, phy sical an d che mical properties
of the contaminated media, and the presence of
other contaminants. The technolog ies below
broadly cove r DU contaminated sites, storage
sites, sites associated with UF6, and address DU-
contaminated soil and groundwater. In such
remedial situ ations, consideration must also be
given to related media, such as dust with the
potential to beco me airborne as a result of
remediation operations. The scope presented
here does not include air pollution such as
particulates from munitions and projectiles, and
in this regard it is worthy to note that EPA is
unaware of any National Priorit y List sites
associated with DU conta mination arising from
projectiles.
7.1 Soil Technologies
Several tech nologies hav e been developed for
use on DU-c ontaminated soils [8]. E xamples
include:
• Excavation, followed by disposal of soi Is in
a low-level waste repository; and
• Excavation of contaminated soil followed by
treatment (i.e., phy sical separation and
chemical extraction).
7.1.1 Physical Separation
Remediation of soils contaminated with metallic
DU ty pically begins with ph ysical rem oval of
large fragments, either by hand sorting or by size
classification using a s creening device [8 ].
Excavation and phy sical separ ation with
-------
screening devices may be used as the principal
means of remediation of contaminated soil if the
contamination is associated with a particular soil
size fir action. Phy sical s eparation of
contaminated and uncontaminated soils may also
be acco mplished using magnetic separation
technology; or gravim etric separation . Other
proprietary devices includ e the Seg mented Gate
System (SGS), produce d b y the Eberline
Instrument Corporation, which monitors
radiation in soil as th e soil m oves along
conveyor belts and then diverts the contaminated
material [8] [9 ]. A fter separation of the
contaminated and uncontaminated soil fractions,
the uncontaminated soils are used as cl ean fill,
and contam inated soils are treated or processed
for disposal . The volume redu ction of
contaminated soil that requires disposal or
treatment ca n result in significant cost savings
[10].
7.1.2 Chemical Extraction
Chemical extraction methods (also referred to as
soil washing or heap leaching) use water with
various chemical additives to dissolve DU fro m
contaminated soils. Th e chemical additives
include oxidants to convert relatively insoluble
U+4 to the more soluble U +4 form, co mplexing
agents such as carbonate that increase uranium
solubility, and strong acids or bases [8] [9] [10]
[11]. The cl eaned soil is then generally used as
fill material, and leachate containing the
uranium and other contaminants is often treated
to rem ove co ntaminants in a concentrat ed form
for disposal [8].
7.2 Groundwater Technologies
Technologies for the treatment of DU in
groundwater include:
• Treatment of groundwater contamination by
conventional pump and treat methods;
• Treatment of groundwater contamination by
permeable reactive barriers; and
• Emerging/Pilot Studies treatments.
7.2.1 Pump and Treat
Pump and treat methods rem ove contam inated
groundwater from the aquifer and can be used to
contain and manage migration of con taminant
plumes. Pum p and treat methods involve
pumping contaminated water from the groun d,
treating it, and either injecting it back into the
aquifer or di scharging it to a suitable surface
system.
7.2.2 Permeable Reactive Barriers
Permeable reactive barriers are passive systems
consisting of reactive materials placed in the
subsurface. As groundwater flows through t he
system, the r eactive materials in the pe rmeable
barrier remove and immobilize the contaminants
[12] [13 ] [14 ]. Reactive m aterials used to
remove uran ium fro m g roundwater in these
systems ty pically include different f orms of
metallic (zero-valent) iron [ 13], but other
materials (e.g., am orphous ferric oxyh ydroxide)
have also been used to rem ove uranium fro m
groundwater ( www.gjo.doe.gov). A
disadvantage of using metallic iron is that the
uranium is rem oved by a precipitation reaction
and the precipitate prod uct has a tendency to
clog the bar rier, thus reducing its 1 ong-term
effectiveness. In contrast, the use of a material
such as apatite, a calciu m phosphate mineral,
leads not o nly to the f ormation of s paringly
soluble uranium phosphate minerals but also to
adsorption of uranyl carbonate complexes on the
apatite surface with little clogging.
Examples of the eff ective use of pe rmeable
reactive bar riers to rem ove urani um fro m
groundwater include installations at Fry Canyon,
Utah, and Durango, Colorado
(www.gjo.doe.gov). A per meable reactiv e
barrier sy stem has also been used to re move
uranium from contaminated grou ndwater in an
area known as the mound site plu me at DOE's
Rocky Flats Enviro nmental Technol ogy S ite
(RFETS) in Colorado [ 15]. Itisi mportantto
note that th e mode of action of perm cable
barriers 1 eaves the contaminant in place unles s
the barrier is excavated (usually at great cost), so
barrier longevity and long-term performance are
important engineering issues.
7.2.3 Commercial Test Studies
Several research and developm ent (emerging)
processes have been te sted on a pilot scale by
Water Rem ediation Technolog y, LLC , (WRT)
10
-------
of Arvada, Colorado, using an adsorptive media
Z-92™, for treat ment of well waters
contaminated with uranium in exces s of the
maximum contam inant level (MCL). WRT
conducted t hree studies at Brazos Mutual
Domestic Water in New Mexico [ 16]; the
Mountain Water & Sanitation District in
Conifer, Colorado [17]; and the Fox R un Water
Company at Chesdin Manor in Dinwiddie
County, Virginia [ 18]. In each of these studies,
municipal water suppliers had wells that
contained water with concentrations of uranium
in excess of the MCLs. WRT provided pilot
scale (approximately one gallon per minute) and
larger seal e (80 gallons per minute) sy stems
using the Z -92™ media to dem onstrate the
effectiveness of the tre atment process, establish
design para meters for the full-scale systems or
document the effectiveness of the WRT system,
and meet regulator y compliance requirem ents.
In each case, the pilot unit or larger scale system
successfully met gross alpha and uranium
compliance at all times.
7.3 Technologies for Soil and Water
Several technologies can be used to treat either
soil or groundwater. Examples include:
• In-situ stabilization, through the use of
amendments, grouting, or capping of
contaminated soil; and
• Phytoremediation, in which plants are used
to extract contaminants from soil or
groundwater.
7.3.1 In-Situ Stabilization/Treatment
In-situ stabilization, treat ment, and a mendment
methods are available for immobilizing uranium
contamination in soils and gro undwater [10].
The addition of am endments (e.g., apatite or
phosphate solutions) stabilizes uraniu m in soils
and gro undwater through the for mation of
relatively in soluble uran ium-phosphate solids
[10] [19] [20]. Grouting or capping of
contaminated soils and s ediments may also be
used to stabilize uranium contamination in place
[10]. As with perm cable reactive barriers,
stabilization leaves the conta mination in place.
Precipitation of uranium to the phosph ate form
leaves uranium highly insoluble and essentially
inert chem ically. Even ingestion would not
result in m uch uranium retention in t he body.
Nevertheless, most methods for scree ning for
uranium would show that the uranium was still
present, and it may be difficult to be sure that the
uranium found b y screening is effectively
stabilized as the phosphate.)
7.3.2 Phytoremediation
Phytoremediation refers t o the utilization of
green plants' natural absorption of specific
components of their host growing medium; it is
an emerging, rather than established, technology
for remediation. Uptake of uranium by plants is
typically small [21] [22 ]. However,
phytoremediation of urani um using sunflowers
(genus Helianthus) has been de monstrated with
uranium waste at Ashtab ula, Ohio, a nd at a
small pond contam inated with uranium near the
Chernobyl nuclear power plant site in Pripy at,
Ukraine [ 23]. Ph ytoremediation usin g Indian
mustard (Brassica junced) of DU contamination
at a firing range at the Aberdeen Proving
Ground in Maryland has also been demonstrated
[24]. Ph ytoremediation of uran ium is
accomplished through the process of
rhizofiltration in which plant root s sorb,
concentrate, and precipitate metal conta minants
from surface or groundwater [23]. The
concentration of uranium contamination
removed from the soil by the plants can reduce
the volum e of material that otherwise would
need be removed for disposal.
A requirem ent of ph ytoremediation is that a
proper disp osal approach m ust be adopted for
the contaminant-bearing plants to prevent cross
media transfe r of contam inants and subsequent
exposure. F or inorgan ic contam inants such as
uranium, simply burning the plants will not
destroy the contaminant.
7.3.3 Monitored Natural Attenuation
In additi on to t he remediation technologies
described ab ove, the use of monitored natural
attenuation ( MNA) may be applied as an
optional pr ocess, which should be evaluated
with other applicable remedies (including
innovative technologies) for restoring
contaminated groundwater, preventing migration
11
-------
ofcontam inantplum es, and protecting
groundwater and other environmental resources.
MNA refers to the reliance on natural
attenuation process es (inc luding a variety of
physical, chemical, or biological processes) to
achieve site -specific re mediation objectives
within a re asonable timefra me co mpared to
other more active methods. In order for natural
attenuation to be selected as a rem edy,
determining the existence and demonstrating the
stability and irreversibility of these mechanisms
is im portant to show that a MNA rem edy is
sufficiently protective. Additionally, site-
specific determinations will alway s have to be
made to ensure that sorption capacity of the
subsurface is sufficient to be fully protective of
human health and the environment. [25]
8. EPA STANDARDS APPLI CABLE
TO DEPLETED URANIUM SITES
When contaminated site s to be released for
public use ar e to be re mediated to meet EPA's
media specifi c risk-based standards or criteria,
several pote ntial drivers for the re mediation
need to be considered. Various statutes apply to
different asp ects of the remediation process.
Table 4 lists the major statutes that apply to
various media that may come into consideration
during remediation. The following sections also
provide further details of the drivers. I t should
be noted that the discussion presented here is not
intended to be comprehensive, but is provided as
a starting point for further investigation.
Table 4: Main Statutes Applying to Various Media
in the Remediation Process.
Media Statute
Air
Water
Soil
Waste
CAA
SDWA
CERCLA, RCRA
NRC regulations, DOE
Orders
8.1 For Soil
Under CERCLA/RCRA, EPA's site cleanup
standards limit a person's incr eased chance of
developing cancer to between 1 in 10,000 and 1
in 1,00 0,000 fro m resid ual uranium on the
ground [26]. Site-specific factors are weighed in
establishing the actual clean up value.
8.2 For Air
Under the CAA, EPA established the amount of
uranium in t he air as the maximum d ose to an
individual not to exceed 10m illirems (mrem)
per year [27].
8.3 For Water
Pursuant to the SDWA, EPA establ ished an
MCLofSO micrograms per liter ( :g/L) for
uranium in drinking water [28].
8.4 Storage of Depleted Uranium
DU is not stored widely around the country; the
majority of the inventor yofDUis stored at
United States Enrichm ent Corporation (USEC)
sites or at DOE sites. DU stored by the military
is only a fraction of the to tal. It should be noted
that under the Ato mic Energy Act (AEA), the
storage of depleted uranium hexafluoride
(DUF6) is self-regulated by the DOE. DUi s
mainly stor edinthe form of uranium
hexafluoride (UF 6), whic h is a colorl ess high
molecular weight (352) solid, at a mbient
temperature. It is readily transformed into a gas
at at mospheric pres sure by raising its
temperature above 56.5°C, and into a 1 iquid by
increasing the pressure and tern perature above
1.5 atm ospheres and 64 °C. All thre e phases,
solid, liquid and gas, coexist at 64°C
A2001joi nt report b y the Organization for
Economic Cooperation and Developm ent
(OECD) Nuclear Energ y Agenc y and the
International Atom ic Energy Agency on
Management of Depleted Uraniu m noted that
DU arising from the operations of enr ichment
plants can be safely stored in different form s,
including uranium tetrafluoride (UF 4), or
uranium oxides (U3O8, UO2, and UO3) in coated
steel contain ers in extern al y ards, provided that
contact with standing water is prevented and that
containers are routinely inspected and localized
defects leading to corrosion are treated. [29]
12
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8.5 For Disposal
For purposes of disposal, DU is cons idered a
low-level waste (LLW) and its di sposal is
subject to U.S. Nuclear R egulatory Commission
(NRC) regulations and appropriate DOE Orders.
Disposal of DU mixed waste having both a
radioactive com ponent and a RCRA hazardous
waste co mponent m ust be performed in
compliance with NRC LLW requirements and
RCRA hazardous waste requirements.
The Executive Summary of the DOE, Oak Ridge
National Laboratory's Assessment of Preferred
DU Disposal Forms pub lished in Ju ne 200 0
noted t hat ". . .the four p otential form s of DU
(DU metal, DUF 4, DUO 2, and DU 3O8) in this
study should be accepta ble for near-surface
disposal at si tes such as t he Nevada T est Site
(NTS) and Envirocare." [30]. It further added
that, "The DU products are considered to be
low-level waste under bo th DOE ord ers and
NRC r egulations." It indicated the pr eference
for disposal at "...the NTS because of its unique
geohydrologic and institu tional settings." The
study also noted that, "Each DU fo rm has a
degree of un certainty reg arding DUF 4, DUO 2,
and DU3O8 acceptability [for disposal at NTS ],
with the unce rtainty decreasing in the following
order: DU metal, DUF4, DUO2, and DU3O8 [30]
EPA has issued guidance entitled
"Establishment of Cleanup Levels for C ERCLA
Sites with Radioacti ve Contamination"
(OSWERNo. 920 0.4-18, August 22 ,1997)
which provi ded clarification for establishing
protective cleanup levels for radioactive
contamination at CERCLA sites. The guidance
reiterated that cleanups of radionuclides are
governed b y the risk range for all carcinogens
established i n the National Oil and Hazardous
Substances Pollution Cont ingency Plan (NCP)
when applicable or re levant and appropriate
requirements (ARARs) are not available or are
not sufficient! y protecti ve. Cleanup should
generally achieve a level of risk within the 10 "4
to 10 "6 carci nogenic risk range based on t he
reasonable maximum exposure for an individual.
In calculating cleanup levels, one shoul d include
exposures from all potential pathway s, and
through all media (e.g., soil, groundwater,
surface water, sediment, air, structures, etc.) To
assist with calculating risk, EPA has developed a
Superfund radionuclide preliminary remediation
goal (PRG) calculator. PRGs for the Superfund
programs are risk-based concentrations, derived
from standardized equations co mbining
exposure information assum ptions with EPA
toxicity data. They are considere d to be
protective for hum ans, thou gh n ot alway s
applicable to a particular site and they d o not
address non-hum an healt h endpoi nts such as
ecological im pacts. PR Gs ar e used for site
"screening" and as initial cleanup goals if
applicable. PRGs are not actuall y cleanup
standards and should not be applied as such.
Their role in site "screening" is to help identify
areas, contaminants, and conditions t hat do not
require further federal art ention at a particular
site. Additionally, the y could be used to
establish final cleanup levels for a site after a
proper evaluation takes place. In the S uperfund
program, this evaluation is carried out as part of
the nine criteria for remed y selection outlined i n
the National Oil and Hazardous Su bstances
Pollution Contingenc y PI an (NCP). Once the
nine criteria analysis is completed, the PRG may
be retained as is, or modified (based on site-
specific inf ormation) prior to beco ming
established as a cleanup standard.
13
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Acronyms
AEA Ato mic Energy Act
ALI Annual Limits on Intake
ARAR Applicable or Relevant and Appropriate Requirements
ATSDR Agency for Toxic Substances and Diseases Registry
CAA Clean Air Act
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
DOE Department of Energy
DU Depleted Uranium
EPA U.S. Environmental Protection Agency
ISCMEM Interagency Steering Committee on Multimedia Environmental Models
LLW Low-Level waste
MARLAP Multi-Agency Radiological Laboratory Analytical Protocols
MARS SIM Multi-Agency Radiation Survey and Site Investigation Manual
MCL Maxim um Contaminant Level
MNA Monitored Natural Attenuation
NCP National Oil and Hazardous Substances Pollution Contingency Plan
NRC Nuclear Regulatory Commission
NTS Nevada Test Site
OECD Organization for Economic Cooperation and Development
OSC On-Scene Coordinators
OSWER Office of Solid Waste and Emergency Response
PRG Preli minary Remediation Goal
RCRA Resource Conservation and Recovery Act
RFETS Rocky Flats Environmental Technology Site
RPM Remedial Project Managers
SDWA Safe Drinking Water Act
SGS Seg mented Gate System
SSL Soil screening Levels
TDI Tolerable Daily Intake
USEC United States Enrichment Corporation
WHO World Health Organization
WRT Water Remediation Technology, LLC
14
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Glossary
Alpha particle - A positively charged particle made up of two neutrons and two protons emitted by
certain radioactive nuclei. Alpha particles can be stopped by thin layers of light materials, such as a sheet
of paper, and pose no direct or external radiation threat; however, they can pose a serious health threat if
ingested or inhaled.
Becquerel (Bq) - The international, or SI, unit used to measure radioactivity, equal to one transformation
(or disintegration) per second. Often radioactivity is expressed in larger units like: thousands (kBq), or
millions (MBq) of Becquerels. One Curie (the traditional activity unit) is equal to 3.7 x 1010 (37 billion)
Bq.
Beta particle - An electron or positron emitted by certain radioactive nuclei. Beta particles can be
stopped by aluminum. They can pose a serious direct or external radiation threat. They also pose a
serious internal radiation threat if inhaled or ingested.
Curie (Ci) - A traditional unit used to measure radioactivity. One Curie equals that quantity of
radioactive material in which there are 3.7xl010 nuclear transformations per second. The activity of 1
gram of radium-226 is approximately 1 Ci.
Depleted uranium - Uranium containing less than 0.7% uranium-235, the amount found in natural
uranium. (See also enriched uranium)
Enriched uranium - Uranium in which the proportion of the isotope uranium-235 has been increased.
(See also depleted uranium.)
Gamma rays - High-energy electromagnetic radiation emitted by certain radionuclides when their nuclei
transition from a higher to a lower energy state. These rays have high energy and a short wavelength.
Gamma rays are very similar to X-rays.
Half-life - The time in which one-half of the atoms of a radioactive isotope disintegrate into another
nuclear form. Half-lives vary from billionths of a billionth of a second to billions of years. Also called
physical or radiological half-life.
Ion - An atom or molecule that has too many or too few electrons, causing it to have an electrical charge,
and therefore, be chemically active.
Isotope - A nuclide of an element having the same number of protons but a different number of neutrons.
Maximum contaminant level (MCL) - The amount of a contaminant that may be present in drinking
water under the Safe Drinking Water Act. MCLs are the standards that drinking water treatment systems
must meet.
Microcurie (\iCi) - One-millionth of a Curie. (3.7xl04 disintegrations per second.)
Molecule - A combination of two or more atoms that are chemically bonded. A molecule is the smallest
unit of a compound that can exist by itself and retain all of its chemical properties.
Monitoring - The use of sampling and detection equipment to determine the levels of radiation or other
toxic materials in land, air, or water.
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Millirem (mrem) - One-thousandth of a rem.
Neutron - A small particle possessing no electrical charge typically found within an atom's nucleus. A
neutron has about the same mass as a proton.
Nuelide - A general term applicable to all atomic forms of an element. Nuclides are characterized by the
number of protons and neutrons in the nucleus, as well as by the amount of energy contained within the
atom.
Oxide - A compound formed by the reaction of oxygen with another element. For example, rust - ferrous
oxide - is iron that has combined with oxygen.
Picocurie (pCi) - One one-millionth of a microcurie (3.7xlO~2 disintegrations per second).
Proton - A small particle, typically found within an atom's nucleus, that possesses a positive electrical
charge. The number of protons is unique for each chemical element.
Rad - (See Radiation Absorbed Dose)
Radioactive decay - The process in which an unstable (radioactive) nucleus emits radiation and changes
to a more stable nucleus. A number of different particles can be emitted by decay. The most typical are
alpha, beta and gamma particles.
Radioactivity - The process of undergoing spontaneous transformation of the nucleus, generally with the
emission of alpha or beta particles, often accompanied by gamma rays.
Radioisotope - An isotope of an element that has an unstable nucleus. Radioactive isotopes are
commonly used in science, industry, and medicine. The nucleus eventually reaches a more stable number
of protons and neutrons through one or more radioactive decays. Approximately 3,700 natural and
artificial radioisotopes have been identified.
Radionuclide - An unstable form of a nuclide.
Rem - (See Roentgen Equivalent Man)
Roentgen Absorbed Dose (rad) - A basic unit of absorbed radiation dose. It is being replaced by the
"gray," which is equivalent to 100 rad. One rad equals the dose delivered to an object by 100 ergs of
energy, per gram of material.
Radiation Equivalent Man (rem) - A unit of equivalent dose. Rem relates the absorbed dose in human
tissue to the effective biological damage of the radiation. Not all radiation has the same biological effect,
even for the same amount of absorbed dose.
Specific activity - The activity of radioisotope per unit mass of a material, either (a) in which the
radioisotope occurs, or (b) consisting of only that isotope.
Treatment - A 'treatment' technology means any unit operation or series of unit operations that alters the
composition of a hazardous substance, pollutant, or contaminant through chemical, biological, or physical
means so as to reduce toxicity, mobility, or volume of the contaminated material being treated. See
Appendix 7 for complete definition.
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Uranium - A naturally occurring radioactive element whose principal isotopes are uranium-238 and
uranium-235. Natural uranium is a hard silvery-white shiny metallic ore that contains a minute amount of
uranium-234.
X-rays - High-energy electromagnetic radiation emitted by atoms when electrons fall from a higher
energy shell to a lower energy shell. These rays have high energy and a short wave length. X-rays are
very similar to gamma rays.
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Additional Sources of Information
The following reports, documents, and websites offer additional information about DU:
Argonne National Laboratory. Depleted Uranium, Human Health Fact Sheet. October 2001.
Argonne National Laboratory. Depleted UF6 Management Information Network.
http: //web. ead. anl.gov/uranium/
International Ato mic En ergy Agenc y. Depleted Uranium Fact Sheet. International Atom ic Energy
Agency Information Series, Division of Public Information, 01-01198 / FS Series 3/02/E.
North Atlantic Treaty Organization. NATO Information: Depleted Uranium.
http: //www .nato. int/du/home .htm
The Royal Society. The Health Hazards of Depleted Uranium in Munitions. Policy Document 7/01. May
2001. Available at http://www.royalsoc.ac.uk/
U.S. Department of Defense. Deployment Health Support, http://www.deploymentlink.osd.mil/
U.S. Department of Energ y, Office of Envir onmental Managem ent, Depleted Uranium Hexafluorid e
Management Program. Depleted Uranium Hexafluoride Fact Sheet. Washington, DC. Fall 2001.
U.S. Department of Energy , Office of Enviro nmental Man agement and Office of Technology
Development. Depleted Uranium: A DOE Management Challenge. Washington, DC. October 1995.
U.S. Department of Energy, Office of Nuclear Energy, Science, and Technology. Final Programmatic
Environmental Impact Statement for Alternative Strategies for the Long-Term Management and Use of
Depleted Uranium Hexafluoride. April 1999.
http: //web. ead. anl. gov/uranium/documents/nepacomp/peis/index.cfm
U.S. Environmental Protection Agency. EPA Facts About Uranium. July 2002.
http: //www .epa. gov/superfund/re sources/radiation/pdf/uranium .pdf
U.S. Environmental Protection Agency. Soil Screening Guidance for Radionuclides: Technical
Background Document. Office of Radiation and Indoor Air, EPA/540-R-00-006. OSWER Directive
9355.4-16. October 2000. http://www.epa.gov/superfund/resources/radiation/radssg.htm
U.S. Environmental Protection Agency. Soil Screening Guidance: A User's Guide. OSWER 9355.4-16A.
October 2000.
U.S. Environmental Protection Agency. Common Radionuclides Found at Superfund Sites. OSWER
9200.1-34. July 2000. http://www.epa.gov/superfund/resources/radiation/pdf/nuclides.pdf
U.S. Environmental Protection Agency. Field Demonstration of Permeable Reactive Barriers to Remove
Dissolved Uranium from Groundwater: Fry Canyon, Utah, September 1997 through September 1998
Interim Report. Air and Radiation Emergency Response. EPA 402-C-00-001. November 2001
World Health Organization, Departm ent of Protection of the Human Environment. Depleted Uranium:
Source, Exposure, and Health Effects. Geneva, April 2001.
Nuclear Energ y Agenc y, Organization for Econ omic Cooperation and Development; Environm ental
Remediation of Uraniu m Production Facilities, A joint report by the OECD-NEA and the International
Atomic Energy Agency (IAEA).
National Research Council. Evaluation of Guidelines for Exposure to TENORM. 1999. Pgs. 33, 34, & 76.
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Appendix 1: Technical Background on Uranium and Depleted Uranium
Origin and History
After the discovery of fission, it was realized that to produce a practical military weapon, the much rarer
isotope of 235U would have to be separated from the much more common 238U isotope. In the United
States, massive efforts were undertaken, as part of the Manhattan Project, to produce uranium enriched in
235U.
Enrichment is a process t hat increases the amount of one isotope relative to another. Regardless of the
enrichment method utilized for uranium, large quantities of uranium depleted in 235U, are generated as a
waste product. This waste became known as depleted uranium, or DU.
Production of highly enriched uranium (HEU) ended in 1992 due to the decreased needs of U.S. defense
programs. In 1993, the United States Enrichment Corporation assumed responsibility for the production
of low-enriched uranium (LEU) for commer cial nuclear reactor fuel. As a re suit of past enrich ment
activities, DOE currently maintains a large inventory of DU, most of it stor ed in the for m of uraniu m
hexafluoride. Smaller quantities of DU are stored in the form of uranium metal, uranium metal alloys,
and uranium oxides.
Uses of Depleted Uranium
The most well known use for DU is in the manufactu re of armor-piercing projectiles due to its high
density and pyrophoric properties. It is also used for other military purposes to reduce the effect of other
conventional munitions. Civil applications are also prevalent, including use in counterweights in aircraft,
missiles, racing sailboat keels, and as a material used in hospitals for shielding X-rays or gamma radiation
from equipment used for radiation therapy. Below are further discussions of some of these applications.
Further Enrichment
DU was once proposed as a feedstock for further ur anium en richment. T his application has been
postponed indefinitely because of the present low co stof uranium ore. It should be noted t hat, like the
initial enrichment process, any further enrichment of DU would result in sm all quantities of "enriched "
uranium and about the same amount of DU. The DU would contain an even sm aller proportion of 235U
than the original DU.
Nuclear Reactor Fuel
While DU cannot be used directly in nuclear reactor fuel, it can be used as a fer tile material in a breeder
reactor to pr oduce plutonium -239 (239Pu). The plutonium , once extracte d, can be blended with DU to
make mixed oxide (MOX) reactor fuel (typically 6% Pu and 94% DU).
Down-blending Highly Enriched Uranium
DU could be blended with weapons grade highly enriched uranium (HEU) to make co mmercial reactor
fuel. This o ption is one method to reduce the qua ntity of HEU, as part of a reduction in the nuclear
weapons stockpile.
Munitions
DU metal has been used in conventional military applications, most notably in tank armor and arm or-
piercing projectiles. Conventional weapons using DU were used in the 1991 and 2003 Gulf Wars and in
NATO operations in Kosovo and Bosnia.
Shielding
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The high atomic number (Z=92) and hi gh density (19.5 g/cm3) make DU an excellent potential material
for shielding persons or equipment from X-rays and gamma rays.
Counterweights
The high density that, in part, makes uranium such an attractive shielding material also makes it suitable
as a small but heavy counterweight in aircraft and other similar applications.
It should be noted t hat Military S pecification MIL-U-70457 s tipulates that DU used by the U.S
Department of Defense (DoD) must have a 235U concentration of less than 0.3% by weight. Most DU has
a 235U concentration of a pproximately 0.2% by weight. In ad ditionto 234U, 235U, and 238U, DU may
contain trace amounts of 236U. The detection of 236U indicates that part of the depleted uranium originated
from reprocessed uranium.
To date, the above uses of DU have consumed only a small portion of the DU in storage. A number of
other uses for DU have b een proposed, so me of wh ich might result in the consu mption of a significant
amount of the stored DU. Additional proposed uses include the following.
High-Density DU Shielding
DU metal has been used in som e shielding applications, but the high cost of converting UF6 to metal has
prevented more widespread use. One proposal being considered is to incor porate DU into concrete for
applications in self-shielded storage boxes for radio active waste and dry spent fuel storage shields for
onsite storage of civilian reactor fuel.
Cask Fill Material, Repository Inert Material, or Back Fill Material
Depleted UO2 has been proposed for use as a fill material in spent fuel nuclear waste cont ainers. The
concept is in tended to provide add itional shielding, reduce the 1 ikelihood of criticality accidents, and
reduce the lo ng-term release of radionuclides. Fo r sim ilar reasons, DU has also been proposed as a
repository inert or backfill material.
Counterweights for Forklift Trucks
Use of DU metal, clad in protective steel shielding, in fork lifts as counterweights would result in th e
design of forklifts that co uld lift heavier loads, whi le at the same time reduce the turning radius of the
forklift. This would allow the forklift t o work i n narrower aisles, increasing the usable warehouse floor
space.
Depleted Uranium and its Chemical Forms
DU can exist in any chemical form in which uraniu m occurs. Since all isot opes of an element undergo
the sam e reactions in nat ure and have aim ost identi cal phy sical characteri sties, natural, enriched and
depleted uranium are essentially chemically identical. Each isotope has the sa me chemical reactions in
the environment, and the sam e biochemical and biol ogical effects on the hu man body. Any differences
exist because of small mass differences between various isotopes.
Chemically, DU is identical to "norm al" uranium. Uranium is the heaviest existing natural element and
can react with most elements except rare gases. In the air, it forms oxides such as uranium oxide (U O2)
and triuranium octaoxide (U3O8). At room temperature, humidity can promote the oxidation of uranium.
When uranium is fragmented in chips, powder, and turnings, the metal beco mes py rophoric,
spontaneously ignites in a ir. Uranium is produced i n a num ber of chemical forms, including uranium
oxides, uranium h exafluoride, uranium tetrafluorid e, and uranium metal. T hese for ms a re explaine d
below in greater detail. T he physical properties of s ome of the m ost important uranium compounds are
given in Table 5.
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Uranium Oxides
Uranium oxides include U3O8, UO2, and uranium trioxide (UO3). Both U3O8 and UO2 are solids that are
relatively stable over a wi de range of environm ental conditions, with a low so lubility in water. In these
forms, the DU is chemically more stable and suitable for long-term storage or disposal. U3O8 is the most
stable form of uranium and is the form most commonly found in nature. The most common form of U3O8
is "yellow cake," a solid produced duri ng mining and milling operations, and named for its characteristic
yellow color. UO 2 is a solid cera mic material, and the form of uranium most commonly used in nuclear
reactor fuel. At ambient temperatures, UO2 gradually converts to U3O8.
Uranium Hexafluoride
Uranium hexafluoride is t he chemical form of uranium used during enrichme nt. UF 6 can be a solid,
liquid, or gas within a reasonable range of temperatures and pre ssures. SolidUF6isa white, dense,
crystalline material, resem bling rock salt. While UF 6 does not react with ox ygen, nitrogen, carbon
dioxide, or dry air, it does react with water or water vapor to form corrosive hydrogen fluoride (HF) and
uranyl fluori de (UO 2F2). Becaus e UF 6 reacts with water, inclu ding hum idity i n the air, it is alway s
handled in leak-tight containers or processing units. Although very convenient for processing, UF6 is not
favored as a chemical form for long-term storage or disposal because of its relative instability.
In uranium conversion and enrichment processes, a major hazard is the handling of uranium hexafluoride
(UF6), which is che mically toxic. Uranium in thes e situations can also react with moisture to release
highly toxic hydrofluoric acid.
Uranium Tetrafluoride
Uranium tetrafluoride (UF 4), sometimes called green salt bee ause of its char acteristic green color, is a
solid com posed of aggl omerating particles with a te xture sim ilar to baki ng soda. It is nonvolatile,
nonhydroscopic, and slightl y soluble in water. When exposed to water, UF 4 slowly dissolves a nd
undergoes hydrolysis, forming several possible uran ium compounds and hydrogen fluoride (HF). UF4 is
generally an intermediate in the conversion of UF6 to uranium oxide (UO2 or U3O8) or uranium metal.
Uranium Metal
Uranium metal is among the densest materials known, with a den sity of 19 gr ams per cubi c centimeter
(g/cm3). The silvery white, malleable, and ductile metal is not as stable as uranium oxide and will
undergo surface oxidation. It tarnishes in air, with the oxide film preventing oxi dation of the bulk
material at room temperature. Uranium metal powder or chips will ignite spontaneously in air at ambient
temperature.
Manufacturing/Enrichment Processes
To produce uranium for commercial reactor fuel or military applications, the uranium must first be mined,
milled, enriched, and converted to a usable form . Uranium ore contains about 0.1% uranium by weight.
This ore is processed at mills using mechanical and chemical measures to separate the uranium fro m the
remainder of the ore. The uranium mills produce "yellow cake," a powder containing mostly U3O8.
Since isotopes of the same element have the same chemical properties, enrichment must be accomplished
by using processes that are based on the phy sical differences between isotopes, such as mass. A number
of methods have been developed to enrich uranium , including gaseous diff usion, gas centrifuge, and
electromagnetic separation . In gaseous diffusion, enrichment is acco mplished by first converting the
yellow cake (U3O8) into uranium hexafluoride (UF 6), a highly corrosive gas. This gas is allowed to pass
through a porous barrier, where the lig hter 235U molecules are slightly m ore li kely to pass through the
barrier than t he heavier 238U molecules. Be cause 235UF6 and 238UF6 molecular w eights ar e nearly the
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same, the gas is only slightly enriched in a single stage. The gas is passed through m any stages, until the
235U fraction in the gaseous UF 6 is increased to the required enrich ment. In addition to t he enriched
uranium produced, a large quantity of DU, containing about 0.2% 235U, is also generated as a byproduct.
Some of this DU has be en used to manufacture armor-piercing penetrators and armor. Army contractors
manufacture penetrators from DU metal at contractor-owned, contractor-operated facilities. The U.S .
Nuclear Regulatory Commission (NR C) and Agre ement States license these contractors to possess an d
store DU and to manufacture munitions components from it. A typical license would allow a contracto r
to receive depleted UF6, transport it to a manufacturing facility, convert it into UF4 and/or metal, and sell
the DU components to an authorized buyer. Most of the depleted uranium hexafluoride (DUF6) is stored
in cylinders at the gaseous diffusion plants where it was generated.
USEC was created as a government corporation to shift some of the enrichment capacity from military to
civilian use. In the early 1990s, USEC was created as a government co rporation that became USEC, Inc.
when it was privatized in 1998. Today, USEC, Inc. is the world's leading supp Her of enriched uranium
fuel for co mmercial nucle ar plants. T hey currently manage enri chment proce sses out of the Paducah,
Kentucky, plant and perform research and laboratory functions out of the Portsmouth, Ohio plant.
DUF6 can be stored in three for ms-liquid, gaseous , or solid. At a mbient tern peratures and pressures
DUF6 is a solid; therefore, it is not easily released from the storage container. When DUF6 mixes with the
water vapor in the air and the iron oft he cylinders, a plug of soli d uranium and iron com pounds and a
small amount of HF gas is created, limiting the amount of material released from a breached cylinder.
Most of DOE's DU inventor y contains between 0.1 to 0.4 weight-percent uranium -235, in the form of
uranium hex afluoride (UF 6) or uraniu m tetra-fluoride (UF 4), well below levels neces sary to create a
nuclear chain reaction. A large stockpile has been contained pri marily in the form of UF 6 i n metal
cylinders stored at DOE's enrichment facilities. DU manufacturing and testing facilities in the United
States are provided in App endix 4, while Appendix 3 contains a listing of sites on the NPL that have or
may have DU contamination.
Table 5: Physical Properties of Uranium Compounds
Compound
Melting Point (°C)
Density (g/cm )
Crystal
Particle
Bulk
Solubility in Water at Ambient
Temperature
Uranium Hexafluoride
(UF6) 64.1
Uranium Tetrafluoride
(UF4) 960 ± 5
Decomposes to UO2F2
4.68
6.7
4.6
2.0- Very Slightly Soluble
4.5
Uranyl Fluoride (UO2F2) Decomposes to U3O8 at
300 6.37
Triuranium Octaoxide Decomposes to UO2 at
(U3O8) 1,300 8.30
Soluble
-2.6
Uranium Dioxide (UO2)
Uranium Metal (U)
2,878 ± 20
1,132
10.96
19.05
1.5- Sparingly Soluble
4.0
2.0- Sparingly Soluble
5.0
19 Sparingly Soluble
Source: http://web.ead.anl.gov/uranium/guide/ucompound/propertiesu/tablephysprop.cfm
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Appendix 2: Measurement Tools and Monitoring Techniques
Monitoring uranium in the environment includes both field measurements and analysis of environmental
samples in the laborator y. Since there is consid erable natural uranium around in all soi Is and the
concentration of natural uranium varies greatly, analyses for uranium alone may not tell anyone if DU is
present, and so isotopic analyses are generally needed. This is also important since, although there is little
difference between the hazard from natural uranium and that from DU, there could be serious legal issues
when a site could be responsible for the DU, but not for the natural uranium. DOE has had c ases where
the total uranium present could have been either background or from leaks or emissions.
The following sections provide some introductor y i nformation o n measurement tools and m onitoring
techniques used for uranium . It should also be noted that EPA has recently published an inventor y of
radiological methodologies for sites contaminated with radioactive materials (see reference 4 on page 9)
and the interested reader is referred to this document for further information.
Field Measurements
Field m easurements are typically perfor med using ha nd-held survey m eters, capable of detecting alpha
particles while discriminating against be ta particles. These instruments ty pically provide an esti mate of
the surface contam ination due to all alpha em itting radionuclides present. Alpha scintillation (ZnS)
detectors have been commonly used in the past, but large-area gas-flow proportional counters have often
been found to be more suitable for remediation efforts where lower detection limits are required [1].
The Measurements Applications and Development Group at Oak Ridge National Laborator y (ORNL)
compared th e perfor mance of sever al hand-held de tectors co mmonly used to detect DU in soil [45 ].
Detectors rev iewed included a Fi eld Instru ment fo r Detection of Low Energy Radiation (FIDLER), a
1.25"x 1.5" sodium iodide (Nal) detector, and o pen and closed window pancake-type detectors. The
open-window pancake detector showed the best dete ction sensitivity, although the Nal detector s ystems
provided more consistent results.
Field measur ements using survey m eters are best suited for ide ntifying surface conta mination. The
detection of DU below the surface usi ng hand-held proportional counters, ioni zation chambers, and GM
counters is inhibited by the absorption of alpha and beta particles in the soil. Hand-held gamma ray
spectrometers can detect DU below the surface, but the lack of a high-energy , high-yield gamma-ray
emission b y 238U significantly reduces the effective ness of th is technique for field identification and
survey [46].
Laboratory Analysis of Environmental Samples
A num ber of analy tical methods have been develop ed to quantif y uranium in environm ental sam pies.
Environmental media that have been analyzed include air filters, swipes, bi ota, water, and soil [ 1].
Analytical methods inclu de both chemical methods that usuall y determ ine onl y t he total quantit y of
uranium, and radiological methods that can determ ine the quantit yofind ividual urani um isotopes.
Chemical methods include kinetic phosphorescence analysis, X-ray fluorometry, and mass spectrometry.
Among the most common radiological methods are alpha spectrometry, gamma ray spectrometry, delayed
neutron counting, and i nstrumental neutron activa tion anal ysis. These methods are briefly described
below.
Kinetic Phosphorescence Analysis (KPA)
KPA is a method that us es a laser to excite uran ium in an aq ueous solutio n and then measures the
emission luminescence intensity overtime. The intensity of the luminescence is proportional to the total
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quantity of uranium in the sam pie. The technique provides no information about the relative isotopic
abundances of uranium and, therefore, cannot distinguish DU from natural uranium in the sample.
X-Ray Fluorometry (XRF)
XRF is si milar to KP A, but uses X-ra ys to excite secondar y X-ray fluorescence in the sam pie material.
The secondary X-rays have wavelengths characteristic of the element that produced them. The X-rays are
separated by wavelength by Bragg diffraction in a crystal with the appr opriate lattice sp acing. The
measurement of the intensity oft he X-ray s at the characteri stic wavelen gth provi des quantitative
information about trace elem ents in th e sample material, including uranium . XRF does not provide
information about the isotopic composition of the uranium in the sample.
Mass Spectrometry (MS)
MS is a technique that separates and analyzes ions based on the ratio of the mass to the charge. Unlike
most chemical methods, this method provides quant itative information about both the tot al quantity o f
uranium in the sam pie and the isotopic co mposition. The two most common MS techniques for
quantification of uranium in environmental samples are thermal ionization mass spectrometry (TIMS) and
inductively coupled plasma-mass spectrometry (ICP-MS). Until r ecently, TIMS had been t he preferred
method for the determination of uranium isotopic ratios in environmental samples because of its superior
sensitivity, a ccuracy, and precision, but ICP-MS has been sh own to provide si milar accuracy and
precision, with higher sample throughput and ease of use [46].
Alpha Spectrometry
Alpha spectrometry is a method that relates the q uantity of a given alpha-emitting radionuclide to the
number of alpha particles detected . Since radionuclides emit alpha particles at one or more discrete
energies, it is possible to relate the area of a peak in the alpha spectrum to the quantity of a radionuclide in
the sample. Alpha particles continuously lose energy to the electrons in the medium they are traveling in,
and will travel only a short distance before they lose all their energy. For this reason, samples should be
kept thin and placed near the detector.
Gamma Spectrometry
Gamma spectrometry involves the det ection of ga mma ray s emitted by radionuclides. Radionuclides
typically em it gamma ray s at one or more discret e energies. The area s of peaks in the ga mma ray
spectrum can be related t othe quantity of the app ropriate radionuclide. Si nee different isotopes of
uranium emit gamma ray s of different energies, gamma spectrometry can be used to quantify the relative
abundance of uranium iso topes in addi tion to the t otal quantity of uranium . Unlike alp ha particles,
gamma rays can penetrate soil and water, and can be detected some distance from the source.
Instrumental Neutron Activation Analysis (INAA)
INAA involves the irradiation of a sample with neutrons to produce an activation product that decays by
emission of gamma rays characteristic of the radionuclide. After irradiation, the sample is counted using
a high resolution gamma ray spectrometer. For DU, the radionuclide of interest is 238U, which absorbs a
neutron to become 239U. 239U emits gamma radiation when it decays to ne ptunium-239 (239Np). As
mentioned in the previous section, INAA can be used with delayed neutron counting to m easure both the
isotopic composition and the total quantity of uranium in the sample.
Delayed Neutron Counting (DNC)
DNC is a method for determ ining the quantit y of 235U and other fissile radionuclides in a sample by
irradiating the sample with neutrons an d counting the delayed neutrons from fission. Delay ed neutrons
result from a small fraction of fission products that emit neutrons as part of their decay chain. DNC can
be used with instrumental neutron activation analy sis, described previously, to deter mine the isotopic
composition of uranium, which is necessary to distinguish DU from natural uranium.
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Analytical Methods for Air Samples
Air samples are typically collected on so me type of air filter and then analy zed by one oft he methods
described previously, including ICP-MS, alpha spectrometry, or INAA.
In a method used b y EPA's National Air and Radi ation Enviro nmental Lab oratory (NAREL), the air
filters are ashed, silica content is volatilized wi th hy drogen fluoride, uranium is extracted with
triisooctylamine, purified by anion exc hange chroma tography, and co-precipi tated with lanthanum as
fluoride. The uranium is then collected by filtration and dried. The activities of 234U, 235U, and 238U are
measured by alpha spect rometry. T his method is u sed to measure urani um in air as part of the
Environmental Radiation Ambient Monitoring System [47].
In another method, described by Singh and Wrenn, air filters are ashed, re-dissolved, and co-precipitated
with iron hydroxide and calciu m oxalate. The uranium is further purified by solvent ext raction and
electrodeposition. A det ection level of 0.0 2dpm/Lfor 238U in solutio n was reported using alpha
spectrometry [48].
Analytical Methods for Water Samples
EPA's Env ironmental and S upport Laborator y pub lished standardized procedures in 1980 for
measurement of radioactivity in drinking water that included uranium analysis by both radiochemical and
fluorometric methods [49], and more recently, developed an ICP-MS method.
In the radiochemical method, the uranium is co-precipitated with ferric hydroxide, purified through anion
exchange chromatography, and converted to a nitrate salt. The re sidue is transferred to a stainless ste el
planchet, dried, and flamed. T he gross alpha activit y is m easured using either a gas flow proportional
counter or a scintillation detection system following the chemical separation [49].
For the fluor ometric method, uranium is concentrat ed by co- precipitation with alum inum phosphate,
dissolved in diluted nitric acid containing magnesium nitrate as a salting agent, with the co-precipitated
uranium extracted into ethyl acetate, and dried. The uranium is dissolved in nitric acid, sodium fluoride
flux is added, and the samples fused over a heat source [50].
The ICP-MS method was developed f or measuring tota 1 uranium in water and waste. The sample
preparation is minimal - filtration for dis solved uranium, followed by acid digestion for total recoverable
uranium. Recovery is quantitative (near 100%) for a variety of aqueous and solid matrices and detection
limits are low, 0.1 :g/L for aqueous samples and 0.05 mg/kg for solid samples [51].
Analytical Methods for Soil Samples
EPA's Office of Radiation and Indoor Air has developed two methods for the radiochem ical analysis of
uranium in various environmental media including soil: a fusion method and a non-fusion method [47]. In
the fusion method, the sa mple is ashed, the silica volatilized, the sample fused with potassiu m fluoride
and pyrosulphate, a 236U tracer added, and the uranium extracted with triisoocty lamine, purified on an
anion exchange colum n, co-precipitated with lantha num, filtered, and prepared in a planchet. Alpha
spectrometry is used to quantify the individual ur anium i sotopes, and the sa mple concentration is
calculated using the 236U yield.
In the non-fusion method, the sample is ashed, the silica volatilized, a 236U tracer added, and the uranium
extracted with triisooctylamine, stripped with nitric acid, co-precipitated with lanthanum, and transferred
to a planchet. Further analysis by alpha spectrometry is the same as that for the fusion method.
25
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Table 6: Selected Analytical Methods for Determining Uranium in Environmental Samples
(see Table 6-2 of the Toxicological Profile for Uranium [1] for additional methods and details)
Sample Matrix
Water
Water
Water
Water
Groundwater
Groundwater
Soil
Soil
Soil,
sediment,
and biota
Soil,
sediment,
and biota
Sample Preparation
Sample fusion with sodium fluoride (NaF)
and lithium fluoride (LiF)
Pre-concentration by ion exchange
chromatography; purification by ion-
exchange and solvent extraction
Extraction by ion-exchange; dissolution in
low oxygen solvent; irradiation
Wet-ashed; reaction with complexant
Separation on resin; automated
Separation and concentration on two High
Performance Liquid Chromatography
(HPLC) columns; complexation with
Arsenazo III
Dissolution in HC1-HNO3 -HF; purification
by co-precipitation, solvent extraction and
electrodeposition
Soil leached with HCl-HclO4 -HF;
purification by ion exchange, and solvent
extraction and electrodeposition
Ashing; fusion with potassium fluoride (KF)
and potassium pyrosulfate (K2S2O7);
purification by extraction with
triisooctylamine; anion exchange
chromatography and co-precipitation
Ashing; extraction into triisooctylamine,
strip from triisooctylamine with nitric acid
(HNO3), and coprecipitation with
lanthanum.
Analytical Method Sample
Detection
Limit
Fluorometry 5 mg/L
(total uranium)
Neutron No data
Activation
Analysis (NAA)
(235Uand238U)
Delayed neutron 0.4 mg/L
analysis (total
uranium)
Pulsed-laser 0.05 ppb
phosphorimetry
Flow Injection- 0.3 mg/L
Inductively for238U
Coupled Plasma
-Mass
Spectrometry
(FI-ICP-MS)
(isotope
quantification)
Spectrophoto- 1-2 mg/L
metry (total
uranium)
Alpha 0.03
Spectrometry mg/sample
(isotope
quantification)
Alpha No data
Spectrometry
(isotope
quantification)
Alpha No data
Spectrometry
Gross Alpha No data
Spectrometry or
Alpha
Spectrometry
Accuracy
117.5% at
6.3 mg/L
No data
No data
103
(average)
±0.3 ng/L
No data
67%
No data
No data
No data
26
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Sample Matrix Sample Preparation
Field Survey None
Analytical Method
Scintillation
Detector and
Count Rate
Meter
Sample
Detection
Limit
Accuracy
No data
Air
Air
Air
Air
Air paniculate collection on glass fiber
filter, digestion in nitric acid (HNO3)
Spiked air paniculate dry and wet ashed;
dissolution; coprecipitation with iron
hydroxide and Ca oxalate, purification by
solvent extraction and electrodeposition onto
platinum
Sample collection on cellulose filters;
ashing; extraction with triisooctylamine;
purification by anion exchange
chromatography and co-precipitation
Collection on cellulose filters
Inductively
Coupled Plasma
-Mass
Spectrometry
(ICP-MS) (total
uranium)
Alpha
Spectrometry
Alpha
Spectrometry
Instrumental
Neutron
Activation
Analysis
(INAA)
0.1 mg/L in No data
final
solution
0.02 dpm/L No data
for238Uin
solution
0.015 pCi No data
0.03 mg per No data
filter
Source: lexicological Report for Uranium [1], Table 6-2
27
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Appendix 3: National Priorities List (NPL) Sites that have or may have DU
Contamination
NPL Site
EPA
Region
Description
Maxey Flats Nuclear Region
Disposal, Hillsboro, 4
Kentucky (NPL-1986)
Malta Rocket Fuel Area, Region
Malta, New York (NPL- 2
1987)
Savannah River Site,
Aiken, South Carolina
(NPL-1989)
Region
4
Rocky Flats
Environmental
Technology Site, Golden,
Colorado (NPL-1989)
Oak Ridge Reservation
(DOE), Oak Ridge,
Tennessee (NPL-1989)
Region
Region
4
The Maxey Flats Nuclear Disposal Site is located in eastern Kentucky near
Hillsboro in Fleming County and was a disposal facility for low-level
radioactive waste. Approximately 533,000 pounds of source material
(consisting of uranium and thorium or ores containing them), 2.5 megacuries
(MCi) of byproduct materials, and 950 pounds of special nuclear material
(i.e., plutonium and enriched uranium) were buried in an area known as the
Restricted Area. Radioactive leachate was discovered to be leaching out of
this area and into surrounding fractured bedrock, soil, and possibly
groundwater. The remediation approach was to capture and evaporate the
leachate, producing solid concentrates that were then buried in onsite
disposal trenches, which were ultimately capped. Other liquid waste was
solidified and buried in another onsite disposal trench, which was also
capped.
This site is located in the towns of Malta and Stillwater, New York,
approximately 1 mile south of Saratoga Lake and 2 miles northeast of
Round Lake. All or part of the Test Station on the site has been leased and
used for a wide range of rocket and weapons testing programs and for space
and other research. In 1979, approximately 8 grams of uranium
hexafluoride gas were released in a portion of the former GE/Exxon nuclear
building. The area was cleaned and the contaminated material was sent to
licensed disposal facilities.
Savannah River has produced nuclear materials for national defense since
1951. This site is surrounded by woods and ranges from dry hilltops to
swampland. The Department of Energy (DOE) reports that a small quantity
of DU was released in January 1984 into Upper Three Runs Creek, which
eventually flows into the Savannah River. The site remedy has included
groundwater pump and treat, capping/solidification of various disposal
basins and solid waste disposal sites, removal and treatment and/or disposal
of hazardous substances, and shipping process waste to the Waste Isolation
Pilot Project in New Mexico.
This former plant manufactured plutonium components for nuclear weapons
and shut down operations in 1989 in response to alleged violations of
environmental statutes. In 1992, the United States decided not to resume
production at this site. During the summer of 1998, DOE excavated 171
drums of uranium and contaminated soil from Trench T-l. Most of this
waste was shipped to the Nevada Test Site for disposal.
Two facilities at this site produced enriched uranium: the Y-12 plant by an
electromagnetic process, and the K-25 plant by gaseous diffusion. DU is a
byproduct of both of these processes. There has been leakage from this site
into the surrounding environment. At the Y-12 plant, the Abandoned Nitric
Acid Pipeline was used to carry waste effluent, which included DU.
Iowa Army Ammunition
Plant, Des Moines
County, Iowa (NPL-
1990)
Region The Iowa Army Ammunition Plant site's primary activity has been to load,
7 assemble, and pack a variety of conventional ammunition and fusing
systems. In the fall of 2000, chunks of DU were reported at the Firing Site.
This has prompted increased focus on the site.
28
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NPLSite
EPA
Region
Description
Naval Surface Warfare Region
Center, Dahlgren, 3
Virginia (NPL-1992)
Materials Technology Region
Laboratory (U.S. Army), 1
Watertown,
Massachusetts (NPL-
1994)
Gaseous Diffusion Plant Region
(USEC), Paducah, 4
Kentucky (NPL-1994)
Nuclear Metals, Region
Concord, Massachusetts 1
(NPL-2001)
NSWC is approximately 4,300 acres and located 40 miles south of
Washington, D. C., along the Potomac River. This site conducts research,
development, testing, and evaluation of surface ship weaponry. Six sites are
related to the former use of munitions, some of which included DU.
Located on 48 acres of land on the north bank of the Charles River, this
arsenal has been in operation since 1816. In addition to storage, this facility
has expanded into weapons development and production. Specifically, DU
machining, milling, forging, and casting took place on this site.
Radiological contamination present at the site has been remediated and
removed. At the time of this writing, the site's remediation focus is on
decontaminating the soil.
This site, which is 3 miles south of the Ohio River and 10 miles west of
Paducah, KY, performed the first step in the uranium-enrichment process.
Separating the uranium by diffusing it through a barrier results in several
end products, one of which is DU. Radiological and volatile organic
compound (VOC) contamination has been found in on- and offsite wells,
and poly chlorinated biphenyl (PCBs) in offsite surface water bodies.
The Nuclear Metals, Inc., also known as Starmet Corporation, site is located
in Concord, Massachusetts. In 1958, NMI began operating a manufacturing
facility that produced DU products, primarily as penetrators for armor
piercing ammunition. Soil, sediment, and surface water samples taken
historically and recently indicate that the holding basin, sphagnum bog, and
cooling recharge pond all have elevated levels of DU.
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Appendix 4: Facilities Involved with the Manufacturing or Testing of Products
Containing DU and/or Components of Products Containing DIT*
Facility/Site/Company Name Location EPA Region
Sierra Army Weapons Depot
Aerojet Ordinance Company
NI Industries
Hughes Helicopter
Armtec Defense Products
China Lake Naval Weapons Center
Elgin Air Force Base Munition Test Facility
Chamberlain
Mason & Hangar
Specific Manufacturing Capability, INEEL
U.S. Army Armament Munitions & Chemical Compound
Olin Corporation
Jefferson Proving Ground, U.S. Army
U.S. Army
Paducah Gaseous Diffusion Plant, U.S. DOE
Nuclear Metal, Inc.
U.S. Army Laboratory Command
Chamberlain
U.S. Army Aberdeen Proving Ground
General Dynamics
U.S. Army Camp Grayling
Honeywell
Honeywell Corporation
U.S. Army Twin Cities Army Ammunition Plant
Kisco
Remington Arms Company Lake City Army Ammunition Plant
Target Research, Inc.
Los Alamos National Laboratory
Los Alamos, New Mexico
Kirkland Air Force Base
Terminal Effects Research and Analysis
Aerojet General Corporation
U.S. Ecology
U.S. Army Ballistics Research Laboratory, Nevada Test Site
Nellis Air Force Base
National Lead Industries
Watervliet Arsenal
Bulova Systems
Lima Army Tank Plant, General Dynamics
Feed Materials Plant, U.S. DOE
Portsmouth Uranium Enrichment Plant, U.S. DOE
Ashtabula Extrusion Plant
Sequoyah Fuel Corporation
General Defense
Carolina Metals
Savannah River Site, DOE
Defense Consolidation Facility
Aerojet Heavy Metals
Martin Marietta Energy Systems K-25 Site*
Day and Zimmerman
Pantex Plant, U.S. DOE
General Dynamics
U.S. Naval Surface Weapons Center
Susanville, California Region 9
Downy, California Region 9
Los Angeles, California Region 9
Los Angeles, California Region 9
Coachella, California Region 3
China Lake, California Region 3
Valpariso, Florida Region 4
Waterloo, Iowa Region 7
Middletown, Iowa Region 7
Idaho Falls, Idaho Region 10
Rock Island, Illinois Region 5
East Alton, Illinois Region 5
Madison, Indiana Region 5
Fort Riley, Kansas Region 7
Paducah, Kentucky Region 4
Concord, Massachusetts Region 1
Watertown, Massachusetts Region 1
New Bedford, Massachusetts Region 1
Aberdeen, Maryland Region 3
Detroit, Michigan Region 5
Grayling, Michigan Region 5
Minnetonka, Minnesota Region 5
Hopkins, Minnesota Region 5
New Brighton, Minnesota Region 5
St. Louis, Missouri Region 7
Independence, Missouri Region 7
Dover, New Jersey Region 2
Los Alamos, New Mexico Region 6
Albuquerque, New Mexico Region 6
Albuquerque, New Mexico Region 6
Socorro, New Mexico Region 6
Lockwood, Nevada Region 9
Beatty, Nevada Region 9
Mercury, Nevada Region 9
Las Vegas, Nevada Region 9
Colonie, New York Region 2
Albany, New York Region 2
Valley Stream, New York Region 2
Lima, Ohio Region 5
Fernald, Ohio Region 5
Portsmouth, Ohio Region 5
Ashtabula, Ohio Region 5
Gore, Oklahoma Region 6
Red Lion, Pennsylvania Region 3
Barnwell, South Carolina Region 4
Aiken, South Carolina Region 4
Snelling, South Carolina Region 4
Jonesboro, Tennessee Region 4
Oak Ridge, Tennessee Region 4
Texarkana, Texas Region 6
Amarillo, Texas Region 6
Falls Church, Virginia Region 3
Dahlgren, Virginia Region 3
30
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Facility/Site/Company Name Location EPA Region
Hercules Radford, Virginia Region 3
Ethan Allen Firing Range General Electric Burlington, Vermont Region 1
Hanford Nuclear Reservation, U.S. DOE Hanford, Washington Region 10
U.S. Army Yakima Firing Range Yakima, Washington Region 10
Stresau Labs Spooner, Wisconsin Region 5
* The Martin Marietta Energy Systems K-25 facility is now known as the East Tennessee Technology Park; it was originally known
as the Oak Ridge Gaseous Diffusion Plant.
** This list includes the locations and names of facilities involved in the manufacturing and/or testing of components that were eventually
incorporated into a product containing Depleted Uranium (DU). Inclusion on this list does not imply that DU was undeniably present at
the facility, but only denotes that the listed facility was part of the manufacturing or testing process of some aspect of a product containing
DU. In a few cases, the components produced at the listed facility did not contain DU at that point of the process.
31
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Appendix 5: Case Study - Nuclear Metals, Inc. (NMI) site, Concord, Massachusetts
Background
The Nuclear Metals, Inc. (NMI) site, also known as the Starmet Corporation site, is located on a 46.4-acre
parcel located at 2229 Main Street in Concord, Mi ddlesex County, Massachusetts. The facili ty includes
five interconnected buildings, a paved parking area, a sphagnum bog, a cooling water recharge pond, and
a holding basin.
In 1958, NMI began operating a manufacturing facility on previously undeveloped land. Nuclear Metals,
Inc. prod uced DU prod ucts, primarily as penetrat ors for armor piercing ammunition. NMI also
manufactured metal powders for medical applicati ons, ph otocopiers, and specialty metal products
Disposal was executed via waste stream discharge . From 1958 to 1985 , NMI discharged wastes to an
unlined hoi ding basin. Extrusion operations o n depl eted uranium prod uced ro ds with a th in layer of
copper coating that was rem ovedin a nitric acid pickling operation during which "small quantities" o f
copper and uranium were dissolved in the nitric acid. The sp ent nitric acid solution w as collected ,
neutralized with a lim e slurry, and discharged to the unlined, in- ground holding basin along with other
wastes. Discharge to the holdi ng bas in ceased in 1985 when NMI began using an acid closed-loop
recycling process.
NMI was ren amed Starmet Corporation in 1 997. In March 1997, the company's NRC license to handle
source material (includin g depleted u ranium, thorium , and tho rium oxide) was transferred to the
Massachusetts Department of Public Health, Radiation Control Program. The state collected groundwater
samples and detected volatile organic co mpounds (VOC s) in NMI' s supply well, previously used for
drinking water. Further analy tical results indicated that the g roundwater beneath the propert y wa s
contaminated with radionuclides (i.e., uranium and thorium), and other materials. In addition, a sphagnum
bog on the property was also been sampled and has shown evidence of radionuclides. Soil, sediment, and
surface water samples taken historically and recently indicated that the holding basin, sphagnum bog, and
the cooling water recharge pond all have exhibited elevated levels of depleted uranium.
Cleanup Approach
In 1998, Starmet conducted a voluntar y partial cleanup of contaminated soils under the Massachusetts
Department of Enviro nmental Protection (MADEP) oversight. The partia 1 cleanup consisted of
excavation and transporta tion off-site of approxim ately 8, 000 cubic y ards of soil contaminated with
depleted uranium and copper. The cleanup halted i n late 1998 when Starmet determined that the cleanup
level set by MADEP could not be m et without excavation of a significantl y greater quantity of material.
The site has since been listed on the National Priorities List; furthe r evaluation of remaining
contamination at the site will be addressed under EPA authority.
Response Action
A time-critical removal assessment was conducted to determine if buried drums on site contain hazardous
material. Two areas containing buried drums and othe r laboratory equipm ent were located during the
removal assessment: one in a fen ced-in area adjacent to the hoi ding basin and cooling water pond, and
contains approxim ately 70 drum s; the other, calle d the "old landfill" cont ains an unknown num ber of
drums and laborator y equipm ent. A tim e-critical removal actio n was conducte d which included: 1)
installation of fencing around t he "old landfill" area where buried drum s are located; 2) re-grading and
capping of the "old landfil 1" area; and 3) installation of a liner in the holding basin to eli minate fugitive
dust and reduce the leaching of contaminated soils into the groundwater. Sampling and analysis of soils in
the holding basin was conducted in September 2001 to fill data gaps in previous sampling efforts and to
determine if data from past sampling efforts performed by Starmet were comparable to EPA data. In June
2002, EPA assumed the groundwater m onitoring program previously performed by Starmet. During the
32
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June 2002 sam pling event, EPA also sam pled sedi ment and surface water o n-site and in the Assabet
River. EPA sampled the groundwater m onitoring wells again in July 2003 before turning site work over
to Potentially Responsible Parties.
Progress and Current Status
Removal of 8,000 cubic y ards of soil from the hoi ding basin b y Starmet under MADEP oversight has
reduced the threat of potential exposure at the site. A time-critical removal action has been conducted to
prevent the direct contact threat with the contaminated surface soils located in the "old landfill" area, and
to reduce the infiltration of precipitation into the holding basin soils. EPA has installed a fence and
warning signs around the perimeter of contaminated soils in the " old landfill" area, has capped the "old
landfill" area; and, has installed a liner over the hold ing basin. I n June 2003, EPA also negotiated an
agreement with five potentially responsible pa rties including: U.S. Arm y, U.S. DOE, Whittaker
Corporation, MONY Life Insurance Co., and Textron, Incorporated, for the pe rformance of a R emedial
Investigation/Feasibility Study (RI/FS), which incl udes the perfor mance of an Engineering Evaluation
and Cost Analy sis (EE/CA). An EE/CA Approva 1 Mem orandum was signed on September 27, 20 02,
which authorizes the performance of an EE/CA in support of aNon Time-Critical Removal Action for the
holding basin and buried drum areas. A lien has been recorded on the Star met property at 2229 Main
Street in Concord.
In May 20 01, Starm et transported 1, 700 drum s c ontaining depleted uranium from its So uth Carolina
facility to the site, to facilitate its planned sale of that facility. Starmet also has approximately 2000 drums
and other containers of depleted uranium wastes and approximately 100 drums of beryllium wastes stored
at the site. Starm et is currently in violation of its MADPH radio active materials license be cause it has
failed to remove the stored drums of depleted uranium materials from the site and is therefore not allowed
to process any radioactive material at the facilit y under their li cense. After Starmet indicated that it
planned to c ease operatic ns or file for bankruptc y, the Comm onwealth of Massa chusetts obtained a
preliminary injunction in state court i n January 20 02, requirin g Starm et to continue to provide site
security and necessary utilities. On March 15, 2002, th e state court placed Star met i nto tern porary
receivership. On or about March 18, 2002, Starmet abandoned the site property. The tern porary receiver
provided security and necessary utilities, with th e assi stance of MADPH, until March 25, 2002.
Thereafter, MADPH beg an providing security at the site. Starmet filed fo r Chapter 11 bankruptcy
protection on April 3, 2002, returned to the site, and continues to operate and provi de site security .
MADPH currently has funding available to provide security and necessary utilities if needed, through the
financial assurance mechanism provided under Star met's radioactive materials license. If MADPH's
funding is exhausted and no other funding source is available, resulting in a bandonment of the facility,
then EPA may be required to address the security and utilities issues.
In April 2004, the state r cached an ag reement with the Army to rem ove the more than 3,000 dr urns of
depleted uranium and other materials from within th e facility. The stat e has procured a co ntractor for
performance of the work, and shipments of dru ms and other material to the E nvirocare waste disposal
facility in Cl ive, Utah, began in Septem ber 2005.11 is expected that the state rem oval work will be
completed in spring 2006. In Se ptember 2004, E PA conditionally a pproved the RI/FS Work Pla n
submitted by de maxi mis, inc., the pr oject coordinator for the private PRPs. Field work associated with
the rem edial investigatio n began i n October 200 4. In Octobe r2004, under the supervi sionofU.S.
Environmental Protection Agency , de maximis, inc., started an investigation of the Su perfund Site t o
locate all contain inants and prepare a feasibility study of the Site cleanup. So far over 1300 sam pies of
soil, sediment and water have been collected and analyzed. Since each sample is analyzed for a number of
different contaminants, the data base contains over 300,000 records. Soil contamination has been found at
several locati ons on the site. Conta mination has also been located in the groundwater. The m ajor
contaminant is uranium. Pol ychlorinated biphenyls (PCBs) and volatile organic co mpounds are also
33
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present. A num her of other die micals have been detect ed at low er concentrations. Analysis of data i s
being conducted to determine the extent of, and the risk from, the contamination.
Under a contract with MA DEP, Envirocare Inc. i s removing all identifiable ra dioactive and other waste
material from the Starmet Plant. Th e material shipped so fart o Clive, Utah, includes 1 ,315 drums of
uranium tetrafluoride, 1,097 drums of a concrete and uranium mixture (conjoint) and 447 drums of other
uranium waste. Approximately 250 drums of uranium tetrafluoride, 200 tons of uranium metal, and other
miscellaneous waste re main to be shipped. The m aterial is rem oved every working day in two or t hree
Landstar Co. tractor trailers. The work was scheduled for completion by March 31, 2006. Removal of the
radioactive material is required prior to starting the EPA investigation of the buildings and soil and water
beneath them. The funding for the contract was provided by the U.S. Army.
In December 2004, de maximis, inc., under supervision of the EP A, removed from the ground between
the Holding Basin and Cooling Water Recharge Pond a n umber of drums containing some uranium and
beryllium waste, production tools and production materials, buried in 1967.
In April 2003 Weston Solutions Inc., under a contract
with EPA, rem oved fro m the ground i n the area of
the Old Landfill (sout h of Bog) drums containing
uranium and bery Ilium, more production tools an d
materials, th en filled, graded and covered the area.
Another pha se of the plant cleanup, which will
include the removal of all contaminated equipment, is
anticipated after Starmet leaves the premises.
Further Information
• httD://vosemite.eoa.aov/r1/nDl oad.nsf/f52fa5c31faf
5c885256adc0050b631/7B6349F1A22FFDF385259
E5006CA840?OoenDocument
httD://www.crewconcord.ora/oaaes/whats new.html
34
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Appendix 6: Case Study - Maxey Flats Nuclear Disposal Site, Hillsboro, Kentucky
Background
The Maxey Flats Nuclear Disposal S ite is locat ed in eastern Kentucky, near Hillsboro, in Flem ing
County. The site was a disposal facility for low-level radioactive wastes. The site is located o n a spur of
Maxey Flats, a ridge 300 feet above the surrounding stream valleys. The area surrounding the site is rural
and agricultural. More than 300 people live within a five mile radius of the restricted area; the closest
residence is within % mile. More than 120 wells and 25 springs are situated within five miles; however,
nearby residents receive household water from a municipal water system.
From 1963 to 1977, the Commonwealth of Kentucky, under authorities granted by the U.S. Government,
licensed private operators including the Nuclear Engi neering Company (NECO) to dispose of low-level
radioactive wastes fro m m ilitary ships and facilities, hospitals, universiti es, corporations, etc.; an
estimated five million cubic feet of material were disposed. Most was solid waste; however, other waste
types were disposed and some were highly radioactive. Approximately 533,000 pounds of source material
(consisting o f uranium and thorium ororescontai ning them ), 2.5 m egacuries (MCi) of b yproduct
materials, and 950 pounds of special nuclear material (plutonium and enriched uranium) were buried in an
area known as the Restricted Area.
Between 1973 and 1986 a large evaporator facility was operated on site to handle contaminated liquids.
During the operation of the facility , workers capped each disposal trench with a layer of soil after it was
filled, but the earth even tually co llapsed into the ditches. Water co llected in the trenches, leachin g
radionuclides into the surroundi ng environment. A restri cted area of approximately 40 acres is situated
entirely on top of the flats. The fenced and patrolled restricted ar ea encompasses the disposal trenches,
"hot wells" (sealed concre te pipes containing plutoni um and uranium), waste storage buildings, and an
evaporator facility. Including the acquired buffer zone properties, the site occupies 900 acres.
Operations closed in 19 73 and b y 1985, the U.S. EPA had developed a list o f potentially responsible
parties (PRPs) fro m the disposal records toward whom to point financial responsibility. In 1986 Maxe y
Flats was placed on the National Priorities List, becoming, at 300 acres, one of the largest Superfund sites
in the hist ory of t he program, and from 1987 to 1991 extensive studies on rem ediation options were
carried out.
Response Action
To assure proper management and closure, the Commonwealth of Kentucky has maintained the site since
the ti me that co mmercial operations ended. The Remedial Investigation and Feasibility Study was
conducted from March, 1 987 until Se ptember, 1991 unde r an adm inistrative Order by Consent. The
Record of Decision was issued in September, 1991. Meanwhile, between December, 1988 and November,
1989, U.S. EPA Emergency Response solidified 286,000 gallons of tanked leachate because of significant
leakage fro m the m etal le achate (radi oactively contaminated tre nch water) tanks. Subseq uently, from
March, 1991 to Septem ber, 1992, U.S. EPA E mergency Response disposed of the solidif ied leachate
blocks in an undergr ound on-site tre nch and i nstalled 30 acres of tern porary ab ove-ground plastic,
impermeable liner to prevent infiltration of rain into the waste trenches.
After negotiations lasting from June, 1 992 until June , 1995, two Consent Decrees (one fo r the 50 de
maximis parties and one for the 306 de minimis parties) arranged for cost allocation and for the
performance of the Reme dial Design (RD) and Re medial Actio n. After the required pub lie co mment
periods, the U.S. District Court activated the decrees in April 1996; the RD for the first o f two major
cleanup phases ( 1. Leachate Removal and Disposal; 2. Building Demolition, On-Site Disposal, and Other
Items) began immediately thereafter. Construction of Phase I and Phase II of the reinforced concrete
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bunkers (for disposal of
completed.
solidified rad ioactive leachate and oth er contam inated materials) have been
Approximately 900,000 gallons of leachate and have been rem oved from within the landfill s ince current
dewatering operations began in September, 1998. However, the median total daily volumes of water
removed declined from more than 5, 050 gallons in 1998 to 1 ess than 600 gallons during the 2000
pumping season. Landfill dewatering operations we re discontinued duri ng the early fall of 2000.
Construction of an interim cap to prevent water infiltration with a perimeter drainage system that includes
the groundw ater interceptor channel has been completed. To verify the dr ainage sy stem does not
negatively i mpact erosio n rates, erosion m onuments have been installed f or m onitoring the rate o f
erosion.
The completion of the Initial Remedial Phase was declared in October 2003 by U.S. EPA. Remedial work
completed at the Maxey Flats Waste Disposal Site has been under the guidance of the U.S. EPA, Atlanta,
Georgia, and in accordance with the Consent Decree signed in 1996. International Technology
Corporation and Shaw Environmental Group performed the remedial construction.
Progress and Current Status
A five year review was co mpleted in 2 002; other fi ve year reviews are planned for 2 007 and 2012, the
latter of which, if successf ul, will render the Co mmonwealth of Kentucky fully responsible for the site.
Corrective steps co mpleted in 20 03 have broug ht m ost problems at the site under control. The steps
include installation of the geomembrane liner, which directs rainwater into a detention basin to be tested
for radioactivity before it is rele ased into a nearby creek. Contaminated water was pumped out of the
storage trenches, solidified with concrete, and bur ied on site. Autom atic monitoring equipment samples
surface water at multiple locations around the site ev ery six hours for testing. A 550-acre "buffer zone"
has been added around the perimeter of the site to separate it from the surrounding farms and homes.
Flats' restricted area, with the excep tion of two
No contaminated water has been found outside Maxey
springs in th e buffer zone where low levels
have been detected. If work contin ues on
schedule, a per manent "cap" consisting of
multiple lay ers of liner a nd soil, with grass
sown on the surface, is planned to cover the
site sometime around 2 012. The to tal cost of
cleanup and m onitoring is expected to exceed
$60 m illion. In addition t o the depleted uranium co ntamination, Maxey Flats is also noted for tritium,
strontium-90, and radium-226 contamination.
Further Information
• htto://www. waste.kv.aov/Droarams/sf/Maxev+Flats. htm
httD://www.eDa.aov/Reaion4/waste/nDl/nDlkv/maxfltkv.htm
httD://nucnews.net/nucnews/2006nn/0604nn/060423nn.txt
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Appendix 7: Treatment Defined by NCR
The concept of treatment is discussed in the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP) under Section 300.5, as follows:
"Treatment technology" means any unit operation or series of unit operations that alters the
composition of a hazardous substance, pollutant, or contaminant through chemical, biological, or
physical means so as to reduce toxicity, mobility, or volume of the contaminated materials being
treated. Treatment technologies are an alternative to land disposal of hazardous wastes without
treatment.
The NCP further states that
"EPA expects to use treatment to address the principal threats posed by a site, wherever
practicable. Principal threats for which treatment is most likely to be appropriate include liquids,
areas contaminated with high concentrations of toxic compounds, and highly mobile materials."
(See Section 300.430 (a)(iii)(A))
The preamble to the NCP provides further clarification of treatment:
"This goal [treatment expectation] reflects CERCLA's preference for achieving protection through
the use of treatment technologies that destroy or reduce the inherent hazards posed by wastes and
result in remedies that are highly reliable over time. The purpose of treatment in the Superfund
program is to significantly reduce the toxicity and/or mobility of the contaminants posing a
significant threat (i.e., "contaminants of concern") wherever practicable to reduce the need for long-
term management of hazardous material. EPA will seek to reduce hazards (i.e., toxicity and/or
mobility) to levels that ensure that contaminated material remaining on-site can be reliably
controlled over time through engineering and/or institutional controls.
Further, the Superfund program also uses as a guideline for effective treatment the range of 90 to 99
percent reduction in the concentration or mobility of contaminants of concern (see preamble
discussion below on "reduction of toxicity, mobility or volume" under Section 300.430 (e)(9)).
Although it is most important that treatment technologies achieve the remediation goals developed
specifically for each site (which may be greater or less than the treatment guidelines), EPA believes
that, in general, treatment technologies or treatment trains that cannot achieve this level of
performance on a consistent basis are not sufficiently effective and generally will not be
appropriate. [See 55 FR 8701]
For further information on this definition please contact EPA's Office of Superfund Remediation &
Technology Innovation.
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U.S. Environmental Protection Agency
Office of Radiation and Indoor Air
Radiation Protection Division
1200 Pennsylvania Avenue, NW
Washington, DC 20460
EPA 402-R-06-011
December 2006
www. epa. gov/rad iation
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