Depleted Uranium Technical Brief ------- ------- 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 ------- Ill ------- 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 ------- 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. ------- 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 ------- 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. ------- 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. ------- 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. ------- 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 ------- 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]. ------- 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 ------- 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. ------- 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 ------- 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 ------- 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 ------- 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. 15 ------- 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. 16 ------- 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. 17 ------- 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. 18 ------- 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 19 ------- 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. 20 ------- 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 21 ------- 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 22 ------- 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 23 ------- 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. 24 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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. 29 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 36 ------- 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. 37 ------- References 1. U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Diseases Registry. Toxicological Profile for Uranium. September 1999. 2. U.S EPA, Office of Air and Radiation. Environmental Characteristics of EPA, NRC, and DOE Sites Contaminated with Radioactive Substances, EPA 402-R-93-005 Washington, DC, March 1993. 3. U.S. EPA, Office of Solid Waste and Emergency Response. Soil Screening Guidance: User's Guide, 2nd Edition Publication 9355.4-23. Washington, DC, July 1996. 4. U.S. EPA, Office of Solid Waste and Emergency Response. Soil Screening Guidance: Technical Background Document, EPA/540-R-95/128. Washington, DC, May 1996. 5. U.S. EPA, Office of Radiation and Indoor Air & Office of Solid Waste and Emergency Response. 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