Department Of Energy Complex Research Articles

Design of Experiments to Support VTR Core Design

To support the development of the U.S. Department of Energy (DOE) Versatile Test Reactor (VTR), a new set of experiments has been established at Argonne National Laboratory (ANL). Driven in part by the validation needs for code calculations and simulations of the reference VTR core design, three unique test facilities have been designed, or are in the process of being designed, to allow measurement of the phenomena and behavior prototypic to the full-scale VTR core. The Pressure drop Experimental Loop for Investigations of Core Assemblies in Nuclear reactors (PELICAN) facility, recently constructed and currently operational, is capable of producing full-scale flow rates for measurement of the pressure drop across a prototypic fuel assembly, including axial reflectors, fuel, and plenum components. The REDuced Scale Hydraulic Inlet Plenum (REDSHIP) experiment, beginning construction, will provide measurements of phenomena within the inlet plenum, including flow distributions through the core assembly ducts, pressure losses across the assembly receptacles, and localized velocity flow fields. A separate-effects-test experiment, called Parallel HEated ASsemblies for Advanced Nuclear Tests (PHEASANT), which is in the early stages of design, is being developed to examine the mixing of exiting core assembly jet streams within the upper plenum. As each of the test facilities becomes operational, they will begin generating timely, reliable, and qualified empirical data suitable for verification and validation of computational tools. In collaboration with other efforts across the DOE complex, the ANL experimental programs are well poised to provide continuous support for the advancement of the VTR design.

A New Era of Nuclear Criticality Experiments: The First 10 Years of Planet Operations at NCERC

Planet is a vertical-lift assembly machine currently located at the National Criticality Experiments Research Center (NCERC) at the Nevada National Security Site. In the past, Planet resided at Technical Area-18 in Los Alamos, New Mexico, as part of the Los Alamos Critical Experiments Facility (LACEF). Following the de-inventorying of LACEF, the Planet assembly was relocated to NCERC in 2008 and became fully operational in June of 2011. The Class Foils experiment, which involves stacking highly enriched uranium foils to obtain a critical configuration, was the first critical experiment performed on Planet. As a major component of the Nuclear Criticality Safety Class taught for the U.S. Department of Energy (DOE) Nuclear Criticality Safety Program, the Class Foils experiment allows personnel from all over the DOE complex to handle nuclear material and to complete the approach to critical safely and successfully. This paper describes the Planet vertical assembly and recent engineering upgrade and a selection of the experiments that have been performed on Planet since its transition to NCERC 10 years ago.

Risk to ecological resources following remediation can be due mainly to increased resource value of successful restoration: A case study from the Department of Energy's Hanford Site

Many nations are faced with the need to remediate large contaminated sites following World War II, the Cold War, and abandoned industrial sites, and to return them to productive land uses. In the United States, the Department of Energy (DOE) has the largest cleanup challenge, and its Hanford Site in the state of Washington has the most extensive and most expensive cleanup task. Ideally, the risk to ecological resources on remediation sites is evaluated before, during, and after remediation, and the risk from, or damage to, ecological resources from contaminants should be lower following remediation. In this paper, we report the risk to ecological resources before, during, and as a consequence of remediation on contaminated units requiring cleanup, and then examine the causes for changes in risk by evaluating 56 cleanup evaluation units (EUs) at the Hanford Site. In this case, remediation includes a restoration phase. In general, the risk to ecological and eco-cultural resources is currently not discernible or low at most contaminated units, increases during remediation, and decreases thereafter. Remediation often causes physical disruption to ecosystems as it reduces the risk from exposure to contaminants. Most new remediation projects at the Hanford Site include ecological restoration. Ecological restoration results in the potential for the presence of higher quality resources after remediation than currently exists on these contaminated lands and facilities. Although counter-intuitive, our evaluation of the risk to ecological resources following remediation indicated that a significant percentage of units (61%) will be at increased risk in the post-remediation period. This increased risk is due to DOE's successful remediation and restoration that results in a higher percent of native vegetation and higher ecological value on the sites in the post-remediation period than before. These newly-created resources can then be at risk from post-remediation activities. Risks to these new higher quality resources include the potential for spread of invasive species and of noxious grasses used in previous cleanup actions, disruption of ecosystems (including those with state or federally listed species and unique ecosystems), compaction of soil, use of pesticides to control invasive species, and the eventual need for continued monitoring activities. Thus, by greatly improving the existing habitat and health of eco-receptors, and maintaining habitat corridors between high quality habitats, the ecological resources in the post-remediated units are at risk unless care is taken to protect them. Many of the negative effects of both remediation and future monitoring (or other future land uses) can be avoided by planning and management early in the remediation process. We suggest DOE and other agencies convene a panel of managers, remediation scientists, regulators, environmental and ecological scientists, Native Americans, economists, and the public to develop a generic list of performance metrics for the restoration phase of remediation, including evaluation of success, which could be applied across the DOE complex.

Biotic dissolution of autunite under anaerobic conditions: effect of bicarbonates and Shewanella oneidensis MR1 microbial activity.

Uranium is a contaminant of major concern across the US Department of Energy complex that served a leading role in nuclear weapon fabrication for half a century. In an effort to decrease the concentration of soluble uranium, tripolyphosphate injections were identified as a feasible remediation strategy for sequestering uranium in situ in contaminated groundwater at the Hanford Site. The introduction of sodium tripolyphosphate into uranium-bearing porous media results in the formation of uranyl phosphate minerals (autunite) of general formula {X1-2[(UO2)(PO4)]2-1·nH2O}, where X is a monovalent or divalent cation. The stability of the uranyl phosphate minerals is a critical factor that determines the long-term effectiveness of this remediation strategy that can be affected by biogeochemical factors such as the presence of bicarbonates and bacterial activity. The objective of this research was to investigate the effect of bicarbonate ions present in the aqueous phase on Ca-autunite dissolution under anaerobic conditions, as well as the role of metal-reducing facultative bacterium Shewanella oneidensis MR1. The concentration of total uranium determined in the aqueous phase was in direct correlation to the concentration of bicarbonate present in the solution, and the release of Ca, U and P into the aqueous phase was non-stoichiometric. Experiments revealed the absence of an extensive biofilm on autunite surface, while thermodynamic modeling predicted the presence of secondary minerals, which were identified through microscopy. In conclusion, the dissolution of autunite under the conditions studied is susceptible to bicarbonate concentration, as well as microbial presence.

Design Studies for the Optimization of 238Pu Production in NpO2 Targets Irradiated at the High Flux Isotope Reactor

Efforts to reestablish a domestic 238Pu production capability in support of National Aeronautics and Space Administration mission objectives are ongoing throughout the U.S. Department of Energy complex. The Plutonium-238 Supply Project (PSP) was initiated in response to a report published by the National Research Council in 2011 stating that “without a restart of 238Pu production, it will be impossible for the United States, or any other country, to conduct certain important types of planetary missions after this decade.” The PSP is targeting a sustained, constant production rate of 1.5 kg/year of heat source PuO2 for several years. Design and optimization studies of 237Np-bearing targets are underway at Oak Ridge National Laboratory (ORNL). It is anticipated that targets will be irradiated in ORNL’s High Flux Isotope Reactor (HFIR) and in the Advanced Test Reactor (ATR) at Idaho National Laboratory. A variety of target materials, containments, arrangements, and irradiation histories have been analyzed, and the results indicate that a sufficient quantity of 238Pu can be produced in HFIR and ATR to fulfill the PSP’s constant production rate target. This paper focuses on the design and optimization of new target configurations containing pellets that are (1) ~93% of the theoretical density of NpO2, (2) loaded into pins of cladding materials that can be handled as solid waste following postirradiation 238Pu recovery operations, (3) irradiated in various vertical experiment facility (VXF) locations in the HFIR permanent beryllium reflector, and (4) rotated within and/or moved to another VXF location following each HFIR operational cycle to maximize 238Pu production and minimize peak heat generation rates.

An Investigation of Plume Response to Soil Vapor Extraction and Hypothetical Drum Failure

Core Ideas Soil vapor extraction (SVE) wells are an effective interim remediation technique. Flow and transport modeling assists in evaluation of vapor plume behavior. Plume simulations assuming drum failure and SVE provide a framework for remediation planning. A small borehole subset could be monitored for detection of VOC releases due to drum failure. Soil vapor extraction (SVE) has been used at sites across the Department of Energy complex, including sites where legacy subsurface wastes represent a potential source of groundwater contamination. At Los Alamos National Laboratory (LANL), leakage from waste drums buried at an inactive chemical waste site has created a subsurface vapor plume of volatile organic compounds (VOCs). Soil vapor extraction operation in 2015 and rebound testing through 2017 were successful in reducing the plume's mass and mitigating VOC migration toward the water table. However, the possibility that waste drums could fail and release VOCs could pose a challenge in the future. To explore the impacts of drum failure, as well as the capabilities of SVE remediation, we simulated hypothetical contaminant release scenarios and subsequent SVE remediation. Three‐dimensional subsurface VOC behavior, including advection, diffusion, and plume interactions with topography, were simulated using the porous flow simulator Finite Element Heat and Mass Transfer. Simulations of future site conditions have allowed identification of “sentry” boreholes that can be monitored for early detection in case of drum failure. Sentry boreholes can also be used to set concentration thresholds above which SVE should be initiated. For the LANL site, simulations show that SVE can be started 3 yr following drum failure and remain a viable remediation tool. More broadly, the principles outlined in this work can be used to support remediation planning at other subsurface waste sites. Predictive models of future releases can be analyzed to set concentration threshold values, guide selection of sentry boreholes, and increase operational efficiency.

Evaluation of ecological resources at operating facilities at contaminated sites: The Department of Energy's Hanford Site as a case study

The U.S. and other developed nations are faced with many contaminated sites remaining from World War II, the Cold War, and abandoned industries, that require remediation and restoration to allow future land uses with minimum acceptable risk to humans and ecological resources. For large Department of Energy (DOE) sites with massive remediation tasks remaining, it is important for managers to be able to assure regulators, Tribal Nations, and the public that human and ecological health are protected. Hanford Site has the largest and most expensive cleanup task within the DOE complex; cleanup will continue beyond 2090. Cleanup involves the use of operating facilities, which also may present a risk to humans or ecological resources. We present a brief description of a methodology to evaluate risks to ecological receptors at the Hanford Site from remaining remediation tasks, and evaluate the risk to ecological resources that operating facilities present currently, during active cleanup of these facilities, and during the post cleanup period. Operating facilities include current, active operations that are located on the site and aid in site cleanup, including both storage and treatment operations. At the Hanford Site, they include waste treatment plants, sludge basins, waste trenches, Central Waste Complex, storage facilities, and disposal facilities, among others. Risk ratings for ecological resources are highest during the remediation phase. Risk ratings for the operating facilities at the Hanford Site range from not discernible to medium currently, from not discernible (ND) to high during active cleanup, and from not discernible to medium following cleanup. The highest ratings are for the Waste Treatment and Immobilization Plant that is being constructed to stabilize radioactive and chemical wastes, and the Liquid Effluent Retention and Treatment Facility that removes and deactivates hazardous contaminants from waste water. Higher ratings in the post-cleanup period are largely due to restoration of ecological resources during cleanup, which increases the potential for injury (if these resources are harmed) because a site will then have higher quality resources after cleanup than it did before. Assessing the value of ecological resources, and determining potential consequences during active remediation and after remediation is essential for compliance with state and federal laws. Understanding the risks to ecological resources from now until clean-up is completed at these facilities is important because of the potential for ecological resources of high value to be degraded, and because cleanup completion is not expected until 2090 or later. The methodology can be applied to any contaminated site requiring a rapid method of assessing potential damages to ecological resources from proposed management actions.

Measuring the Psychosocial Effects of Beryllium Sensitization and Chronic Beryllium Disease in Current and Retired Workers

Current and former workers from the U.S. Department of Energy complex were surveyed to measure the psychosocial effects of beryllium sensitization (BeS) and chronic beryllium disease (CBD). Questionnaires were administered to measure uncertainty in illness, psychosocial adjustment to illness, and health quality of life. Hypotheses were tested and relationships between variables determined. There were 126 participants; 52 with CBD and 74 with BeS. The health quality of life survey indicated participants with CBD had significantly different physical component summary scores than those with BeS. Mental component summary scores were similar. Psychosocial adjustment scores were also significantly different. Uncertainty scores were approximately equal. Moderate to strong correlations were found between the three variables. As uncertainty increased, health quality of life decreased unless the effects were mediated by psychosocial adjustments to the illness. It was concluded that BeS may have as much impact on mental health as CBD. If true, this adds an important new component to the spectrum of CBD that has implications for treatment and workers compensation.

Lesson Learned from the February 2014 Fire and Radiation Release Events at the Waste Isolation Pilot Plant in New Mexico, USA

The recently reopened Waste Isolation Pilot Plant (WIPP) is expected to resume accepting new shipments of nuclear waste from across the DOE (Department of Energy) complex by April, 2017. There was no road map for cleaning up the nation’s only deep geologic repository for defense nuclear waste when it was contaminated three years ago after two accidents in February 2014 shutdown the facility and contaminated 22 workers with very low level of radiation as some radioactive material escaped above ground. The dominant radionuclides released were americium and plutonium, in a ratio that matches the content of the breached drum. According to the source term estimation, the actual amount of radioactivity released from the WIPP site was less than 1.5 millicurie. From the modeling, monitoring, and air filter analyses, DOE calculated public doses from this radiation release event to be less than 0.01 mSv (<1 mrem/year), which is well below the 0.1mSv/year (10mrem/year ) regulatory limit. The cumulative effect of inadequacies in ventilation system design and operability, compounded by a slow erosion of safety culture and an atmosphere of complacency, resulted in the release of radioactive material from the WIPP underground. The clean-up is expected to cost DOE almost a billion, and with radiological contamination and reduced air flow underground, the regular work of running WIPP is going to be slow and costly. Nevertheless, the lesson learned as a result of these two accidents at the WIPP is worth documenting as it brought renewed focus on risk, oversight, and emergency planning surrounding the nuclear facility. At some point in the future, the changes made in response to these two events will be seen as a valuable lesson learned on behalf of future repository program.

Traveling to the Future: Human Factors and Ergonomics Integration, Simulation, Field Testing and Strategic Partners in Support of Heavy Vehicle Research

The proliferation of inexpensive sensors and devices capable of inter-device communication is hastening the implementation of smart technology for current and future generations of vehicles nationwide. The introduction of this technology promises to enhance safety, reduce accidents, increase fuel efficiency, and perhaps enhance traveler experience. The challenge associated with transitioning to and implementing various smart technologies is to ensure that driver, passenger, and pedestrian safety are not compromised. At Idaho National Laboratory (INL), human factors engineering (HFE) staff participates in the evaluation of technology for fleet operations, including review of fuel efficiency, enhancement and driver performance, and assists in the testing of prototype buses with advanced systems. One of the potential applications of smart technology lies in the development of an interoperable wireless communications network among vehicles. INL uses HFE expertise in conjunction with fleet operations and Mission Support Services expertise to guide the introduction and implementation of vehicle to vehicle and vehicle to infrastructure communications and to support interactions with stakeholders including Cooperative Research and Development Agreement partners. To our knowledge, our approach integrating HFE and fleet operations is unique within the Department of Energy complex. The Heavy Vehicle Simulator, located at the Center for Advanced Energy Studies, is used for design evaluation, and HFE supports the conduct of field tests involving bus drivers and supervisors. INL's HFE group and fleet operations are partners involved in a number of collaborative initiatives to segue the Department of Energy's largest motor coach fleet to the next generation of smart vehicles. This presentation reviews our approach, findings, and successes from two of the focus areas (predictive driver efficiency display prompting and vehicle prototype testing); discusses how HFE has been integrated in the planning and design review process for INL fleet operations; and highlights progress on connected vehicle research initiatives.

Package plutonium metal and oxide in flowformed canisters

Plutonium metal and oxide are typically handled and processed in isolated enclosures (gloveboxes) and then transferred to storage packing systems. The United States Department of Energy (DOE) outlines general requirements relevant to the planned DOE activities to stabilise and package plutonium materials in containers, and place them in long term storage. Inner and outer containers have been qualified as the primary barrier to the environment during storage of the plutonium materials. The design and fabrication of the containers are consistent across the DOE complex. The flowform manufacturing process has been used for over 20 years to fabricate the weld free, precise containers for several DOE sites meeting ASME section III code, subsection NCA-3851.2 (a)(1).

Perspective on Department of Energy Geospatial Science

ABSTRACT For many decades, the Department of Energy (DOE) has been an international leader in basic scientific and engineering research that utilizes geospatial science to advance the state of knowledge in disciplines impacting national security, energy sustainability, environmental stewardship, and associated basic research. However, the realized benefits from cross-cutting geospatial science contributions have fallen short of what they could have been with greater collaboration across the DOE complex, stronger emphasis on core geographic information science (GIScience) research and development to support advanced applications, increased strategic institutional support (e.g., for management of legacy data), and additional education and outreach concerning how geospatial science can benefit DOE programs and operations. We propose a vision for DOE's geospatial science based on expanded collaboration to address major national problems, additional advanced GIScience research and development, and a long-term strategy to better manage DOE's geospatial science resources (personnel, facilities, shared data, etc.).

Perspectives on chemical hazard characterization and analysis process at DOE

The United States (U.S.) Department of Energy (DOE) has a policy of Integrated Safety Management System (ISMS) that requires a hazard analysis and implementation of controls to protect the workers and public in an authorized hazard facility. The ISMS applies to all DOE facilities through DOE P 450.4, Safety Management System Policy , and DOE Acquisition Regulation (DEAR) clause 48 CFR 970.5223-1, Integration of Environment, Safety, and Health into Work Planning and Execution . However, no DOE-order or standard currently exists that provides specific guidance for the development of safety basis (SB) documentation for non-nuclear facilities. Various DOE sites over the years have adopted individual site-specific chemical SB processes and documentation resulting in wide variations across the DOE complex. The CSTC Phase 1 report, Current Chemical Hazard Characterization Practices in the DOE Complex summarizes the variations in the DOE complex (CSTC 2003-C). 1 In order to provide a common understanding of non-nuclear SB for chemical facilities, this report identifies various steps involved in developing a safety document that includes essential features of the five core steps of the ISMS. The SB development is an iterative process, but in general order of process completion, the listed steps for chemical, non-nuclear facility safety document are: • Facility and work description; • Hazard identification; • Facility hazard classification – industry Process Safety Management (PSM) based versus DOE traditional based high/moderate/low classification; • Hazard analysis – qualitative and/or semi quantitative; • Identification of controls; • Commitments to safety management programs (SMP); • Document and approval process. The non-nuclear SB process – (a) looks at different methodologies including hazard analysis from the chemical industry and DOE-STD-3009 nuclear facility-like approaches that can be used to implement each step, and (b) describes the advantages and disadvantages of various implementing methodologies that are either already in use or could be used by non-nuclear facilities. To note, this report is not a proposed standard or guidance for chemical, non-nuclear safety document. This report outlines various steps and methodologies together with advantages and disadvantages associated with them. Each DOE/NNSA facility or site can determine the appropriate course of action based on the merits and demerits of each approach. Adoption of any step of the safety document is voluntary. While intended for chemical, non-nuclear SB applications, the report may be useful in other related areas such as the emergency management program as required by DOE O 151.1C and explosive operations as required by 29 CFR 1910.109.

Improving Sample Analysis Throughput and Quality with a .NETTM-based, Real-Time QC Decision Support System

This report describes an integrated, software-based quality control system designed to significantly improve the sample analysis throughput and quality of beryllium analysis laboratories throughout the U.S. Department of Energy complex. Originally, this system was developed to minimize the downtimes of expensive instrumentation (here: Perkin Elmer® 4300™ DV Inductively Coupled Plasma Optical Emission Spectrometers) and to automate the sample analysis quality control process. This automated software system was also expected to eliminate time-consuming and error-prone result data interpretation, which previously was done manually. To achieve these goals, Los Alamos National Laboratory recently implemented a rule-based decision support system in the C#.NET™ that continuously extracts and analyzes data from the instrument's result database as the data is being generated. Using a customer-specific expert rule base, the system is capable of detecting abnormal operating situations fully autonomously in real time. This also enables the system to perform on-the-fly quality control and automatic, electronic event notification of lab personnel via e-mail and pager.

Improving Sample Analysis Throughput and Quality with a .NET™-based, Real-Time QC Decision Support System

This report describes an integrated, software-based quality control system designed to significantly improve the sample analysis throughput and quality of beryllium analysis laboratories throughout the U.S. Department of Energy complex. Originally, this system was developed to minimize the downtimes of expensive instrumentation (here: Perkin Elmer® 4300™ DV Inductively Coupled Plasma Optical Emission Spectrometers) and to automate the sample analysis quality control process. This automated software system was also expected to eliminate time-consuming and error-prone result data interpretation, which previously was done manually. To achieve these goals, Los Alamos National Laboratory recently implemented a rule-based decision support system in the C#.NET™ that continuously extracts and analyzes data from the instrument's result database as the data is being generated. Using a customer-specific expert rule base, the system is capable of detecting abnormal operating situations fully autonomously in real time. This also enables the system to perform on-the-fly quality control and automatic, electronic event notification of lab personnel via e-mail and pager. (JALA 2003;8:107–12)

Dose rate prediction methodology for remote handled transuranic waste workers at the waste isolation pilot plant.

An approach is described for estimating future dose rates to Waste Isolation Pilot Plant workers processing remote handled transuranic waste. The waste streams will come from the entire U.S. Department of Energy complex and can take on virtually any form found from the processing sequences for defense-related production, radiochemistry, activation and related work. For this reason, the average waste matrix from all generator sites is used to estimate the average radiation fields over the facility lifetime. Innovative new techniques were applied to estimate expected radiation fields. Non-linear curve fitting techniques were used to predict exposure rate profiles from cylindrical sources using closed form equations for lines and disks. This information becomes the basis for Safety Analysis Report dose rate estimates and for present and future ALARA design reviews when attempts are made to reduce worker doses.

Sulfur Polymer Solidification/Stabilization of elemental mercury waste

Elemental mercury, contaminated with radionuclides, presents a waste disposal problem throughout the Department of Energy complex. In this paper we describe a new process to immobilize elemental mercury wastes, including those contaminated with radionuclides, in a form that is non-dispersible, will meet EPA leaching criteria, and has low mercury vapor pressure. In this stabilization and solidification process, elemental mercury is combined with an excess of powdered sulfur polymer cement (SPC) and sulfide additives in a mixing vessel and heated to ∼ 40 °C for several hours, until all of the mercury is converted into mercuric sulfide (HgS). Additional SPC is then added and the temperature of the mixture raised to 135 °C, resulting in a molten liquid which is poured into a mold where it cools and solidifies. The final treated waste was characterized by powder X-ray diffraction and found to be a mixture of the hexagonal and orthorhombic forms of mercuric sulfide. The Toxicity Characteristic Leaching Procedure was used to assess mercury releases, which for the optimized process averaged 25.8 μg/l, with some samples being well below the new EPA Universal Treatment Standard of 25 μg/l. Longer term leach tests were also conducted, indicating that the leaching process was dominated by diffusion. Values for the effective diffusion coefficient averaged 7.6×10 −18 cm 2/s. Concentrations of mercury vapor from treated waste in equilibrium static headspace tests averaged 0.6 mg/m 3.

Process Modeling of Plutonium Conversion and Mixed-Oxide Fuel Fabrication for Plutonium Disposition

In an effort to reduce the global stockpile of nuclear explosive devices, ~50 tonnes of weapons-grade plutonium have been declared surplus to national security needs by the United States. This surplus, located at six sites within the U.S. Department of Energy complex (the Hanford Site, Idaho National Engineering and Environmental Laboratory, Los Alamos National Laboratory, the Pantex Plant, the Rocky Flats Environmental Technology Site, and the Savannah River Site) must now be rendered unattractive for use in nuclear weapons. The goal is that this drive will be concurrent with similar activities in Russia. One method currently under investigation is the conversion of the plutonium metal into mixed-oxide (MOX) reactor fuel. Approximately 35 tonnes of the surplus plutonium is in a form suitable for fabrication into MOX fuel. This fuel would be used in currently operating reactors for power production.Two processes are currently under consideration for the disposition of the 35 tonnes of surplus plutonium through its conversion into fuel for power production. These processes are the Advanced Recovery and Integrated Extraction System (ARIES) process, by which plutonium metal is converted into a powdered oxide form, and MOX fuel fabrication, where the oxide powder is combined with uranium oxide powder to form ceramic fuel. Because it is envisioned that plutonium disposition will occur concurrently in the United States and Russia, the timely disposition of the plutonium is deemed important to national security. However, the need for quick disposition must be tempered by cost considerations and constraints on the reactors that will ultimately use the fuel. This study was undertaken to determine the optimal size for both the pit conversion and MOX fabrication facilities, whereby the 35 tonnes of plutonium metal will be converted into fuel and burned for power. Proper sizing of the facilities will help avoid unnecessary delays and excessive costs and thus is important in the success of the disposition mission.The bounding conditions used were a plutonium concentration of 3 to 7%, a burnup of 20,000 to 40,000 MWd/tonnes HM, a core fraction of 0.1 to 0.4, and the number of reactors ranging from 2 to 6. Using these boundary conditions, the optimal plutonium concentration was found to be 7%. This resulted in an optimal throughput ranging from 2000 to 5000 kg/yr of plutonium. The data showed minimal costs (based solely on facility size and required manpower) resulting from throughputs in this range, at 3840, 2779, and 3497 kg/yr of plutonium, which resulted in a facility lifetime of 9.1, 12.6, and 10.0 yr, respectively.

Ecological Risk Assessment at the Department of Energy: An Evolving Process

The United States Department of Energy (DOE) has facilities in 34 states, and many of these have chemical or radiological contami-nation that provides a potential risk to human or ecological health. Over the next few decades many of these sites will be cleaned up, and ecological risk assessment will be one tool used to make decisions about remediation and future land use. The DOE has developed an overall strategy for making remediation decisions that involves using risk assessment, with stakeholder input, although the final decisions are the Departments. The key elements of its ecological risk assessments involve valuing the severity and likelihood of occurrence of adverse ecological effects. It is currently using a process that incorporates descriptions of the environmental risk, and valuations of the severity and likelihood of an adverse outcome before, during, and after any remedial activity. The primary difficulty with the current DOE approach to risk has been a failure to use existing information to identify either species of concern or unique habitats at risk, and a lack of uniformity across the DOE complex. Nonetheless, the inclusion of ecological risk assessment in the decision-making process will help achieve one of the new missions of DOE: the protection and maintenance of biodiversity and healthy ecosystems at sites under its control.

Recommended default methodology for analysis of airborne exposures to mixtures of chemicals in emergencies.

Emergency planning and hazard assessment of Department of Energy (DOE) facilities require consideration of potential exposures to mixtures of chemicals released to the atmosphere. Exposure to chemical mixtures may lead to additive, synergistic, or antagonistic health effects. In the past, the consequences of exposures to each chemical have been analyzed separately. This approach may not adequately protect the health of persons exposed to mixtures. This article presents default recommendations for use in emergency management and safety analysis within the DOE complex where potential exists for releases of mixtures of chemicals. These recommendations were developed by the DOE Subcommittee on Consequence Assessment and Protective Actions (SCAPA). It is recommended that hazard indices (e.g., HIi = Ci/Limiti, where Ci is the concentration of chemical "i") be calculated for each chemical, and unless sufficient toxicological knowledge is available to indicate otherwise, that they be summed, that is, sigma i(n) = 1HIi = HI1 + HI2 + ... + HIn. A sum of 1.0 or less means the limits have not been exceeded. To facilitate application of these recommendations for analysis of exposures to specific mixtures, chemicals are classified according to their toxic consequences. This is done using health code numbers describing toxic effects by target organ for each chemical. This methodology has been applied to several potential releases of chemicals to compare the resulting hazard indices of a chemical mixture with those obtained when each chemical is treated independently. The methodology used and results obtained from analysis of one mixture are presented in this article. This article also demonstrates how health code numbers can be used to sum hazard indices only for those chemicals that have the same toxic consequence.