Pantex Plant Research Articles

Application of a multiple lines of evidence approach to document natural attenuation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in groundwater

This study utilized innovative analyses to develop multiple lines of evidence for natural attenuation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in groundwater at the U.S. Department of Energy’s Pantex Plant. RDX, as well as the degradation product 4-nitro-2,4-diazabutanal (NDAB; produced by aerobic biodegradation or alkaline hydrolysis) were detected in a large portion of the plume, with lower concentrations of the nitroso-containing metabolites produced during anaerobic biodegradation. 16S metagenomic sequencing detected the presence of bacteria known to aerobically degrade RDX (e.g., Gordonia, Rhodococcus) and NDAB (Methylobacterium), as well as the known anoxic RDX degrader Pseudomonas fluorescens I–C. Proteomic analysis detected both the aerobic RDX degradative enzyme XplA, and the anoxic RDX degradative enzyme XenB. Groundwater enrichment cultures supplied with low concentrations of labile carbon confirmed the potential of the extant groundwater community to aerobically degrade RDX and produce NDAB. Compound-specific isotope analysis (CSIA) of RDX collected at the site showed fractionation of nitrogen isotopes with δ15N values ranging from approximately −5‰ to +9‰, providing additional evidence of RDX degradation. Taken together, these results provide evidence of in situ RDX degradation in the Pantex Plant groundwater. Furthermore, they demonstrate the benefit of multiple lines of evidence in supporting natural attenuation assessments, especially with the application of innovative isotopic and –omic technologies.

Hypothyroidism among former workers of a nuclear weapons facility (Pantex), Amarillo, Texas

ObjectivesIonising radiation can alter thyroid function, and workers at a nuclear weapons facility may be exposed to elevated levels of radiation. The Pantex Plant, located in Amarillo, Texas, is the...

The Pit Requalification and Surveillance Programs at the U.S. DOE Pantex Plant

The Pit Requalification and Surveillance Programs are managed and operated by the Special Nuclear Material (SNM) Division at the U.S. Department of Energy Pantex Plant in Amarillo, Texas, and are vital to maintaining the safety, security, and reliability of the nation's nuclear weapons stockpile, thereby, providing an essential deterrent arsenal on behalf of the U.S. and its allies.

Data Warehouse Integrates Toxic Inhalation Hazards and Hazardous Materials Information, GIS, and the Intranet

ABSTRACT A data warehouse, developed for United States Department of Energy/National Nuclear Security Administration (USDOE/NNSA) Pantex Plant in a multi-department collaboration, brings data from disparate datasets and spatial information about the site together into a single database accessible through an intranet web page or ArcGIS software. The web page directs queries of buildings, facilities, and areas through a Geographic Information System (GIS) viewer that displays spatial site information and chemical hazards data. The Spatial Database Engine (ArcSDE) provides the vehicle for linking mainframe datasets, downloaded daily, to current spatial information about buildings and facilities that store chemicals of potential concern to firefighters and other emergency responders. The system is available to the plant's shift supervisors and individual GIS users throughout the department.

8.3.3 Enterprise Domain Modelling Process Using SysML for the Tooling Enterprise at the U.S. NNSA's Pantex Plant

AbstractThis paper describes the process and methods applied in modelling an enabling enterprise within the NNSA Pantex Plant within the U.S. Nuclear Weapons Complex. The process used is based on the Enterprise Domain Modelling and systems analysis methods enabled by Systems Modelling Language (SysML). SysML consists of four types of views to describe a system: structure, requirements, parametrics, and behavior (INCOSE, 2006). The model illustrated behavioural viewpoints of the tooling enterprise.

Evaluating Ozone as a Remedial Treatment for Removing RDX from Unsaturated Soils

Years of wastewater discharge at the Department of Energy’s Pantex Plant have contaminated the vadose zone and underlying perched aquifer with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Because the vadose zone is acting as a continual source of groundwater contamination, removing RDX from the unsaturated zone is paramount to prevent further contamination. We determined the efficacy of ozone to degrade and mineralize RDX. Solution experiments showed that ozone (27mgL−1; 150mLmin−1) was effective in mineralizing 80% of the RDX (30mgRDXL−1) provided that some Pantex soil was present to buffer the solution pH. Soil columns treated with ozone produced 50% RDX mineralization within 1 day and >80% within 7 day. Experiments designed to evaluate aerobic biodegradation following partial ozonation of a RDX solution showed that ozone-generated RDX products were much more biodegradable than untreated controls in aerobic microcosms (35 versus <0.3% cumulative mineralization). These results support the use of ozone as a remedial treatment for the contaminated vadose zone at the Pantex facility.

Evaluating Biodegradation as a Primary and Secondary Treatment for Removing RDX (Hexahydro-1,3,5-trinitro-1,3,5-triazine) from a Perched Aquifer

ABSTRACT Ground water beneath the U.S. Department of Energy (USDOE) Pantex Plant is contaminated with the high explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine). The authors evaluated biodegradation as a remedial option by measuring RDX mineralization in Pantex aquifer microcosms spiked with 14C-labeled RDX (75 g soil, 15 ml of 5 mg RDX/L). Under anaerobic conditions and constant temperature (16°C), cumulative 14CO2 production ranged between 52% and 70% after 49 days, with nutrient-amended (C, N, P) microcosms yielding the greatest mineralization (70%). The authors also evaluated biodegradation as a secondary treatment for removing RDX degradates following oxidation by permanganate (KMnO4) or reduction by dithionite-reduced aquifer solids (i.e., redox barriers). Under this coupled abiotic/biotic scenario, we found that although unconsumed permanganate initially inhibited biodegradation, > 48% of the initial 14C-RDX was recovered as 14CO2 within 77 days. Following exposure to dithionite-reduced solids, RDX transformation products were also readily mineralized (> 47% in 98 days). When we seeded Pantex aquifer material into Ottawa Sand that had no prior exposure to RDX, mineralization increased 100%, indicating that the Pantex aquifer may have an adapted microbial community that could be exploited for remediation purposes. These results indicate that biodegradation effectively transformed and mineralized RDX in Pantex aquifer microcosms. Additionally, biodegradation may be an excellent secondary treatment for RDX degradates produced from in situ treatment with permanganate or redox barriers.

Nuclear Pit Facility’s Merits, Snags, and Timelines

In the June 2004 issue of Physics Today, (page 34), Jim Dawson reports on the American Physical Society (APS) discussion paper, published in April 2004, about a modern pit facility. That paper evaluates an MPF based on an overly optimistic combination of assumptions that obviate the need for planning such a facility. A parametric evaluation of the stockpile plan recently delivered to Congress and the current estimates of pit lifetimes by the National Nuclear Security Administration weapon laboratories show that continuous planning for an MPF is prudent risk management to meet national security needs. 1 1. US Department of Energy, National Nuclear Security Administration, Report to Congressional Defense Committees on “An Enhanced Schedule for the Modern Pit Facility, February 2004. Available at http://www.fcnl.org/pdfs/nuc_mpfreport.pdf. The NNSA advocates managing the risks to national security by uninterrupted planning for an MPF while obtaining further information for acquisition decisions. For example, initial results from accelerated pit-aging experiments and from the inevitable aging effects of plutonium on weapon performance are expected in 2007. The APS position paper advocates a high-risk approach of deferring or curtailing the MPF project until such information is available. The NNSA plan for an MPF includes a series of major system-acquisition critical decisions in 2007, in 2009, and at the start of construction in 2012. Based on the current plan, the Secretary of Energy will not be making irreversible decisions on constructing an MPF until early in the next decade. That is well beyond the 2006 minimum date suggested by the APS position paper for making such decisions.The APS paper is replete with examples of unrealistic optimism and factual errors. Some examples include discounting the challenges of upgrading production capacity to 80 pits per year at the Los Alamos National Laboratory TA-55 facility or rapidly enhancing production outputs in a future facility. Although a small capacity of 125 pits per year is the most likely path forward, the MPF environmental impact statement provides analyses for capacities of 125 to 450 pits per year, not because of a desire to maintain large stocks of undeployed warheads as suggested by the APS paper, but to ensure that the maximum potential environmental impacts of an MPF have been considered for National Environmental Policy Act compliance purposes. APS asserts that pits in storage at the Pantex plant in Amarillo, Texas, could be used as replacements and thus obviate the need for a new facility. However, that assertion lacks technical foundation because pits stored at Pantex will age similarly to pits that are stockpiled.Deferral of MPF planning, which was suggested in the APS paper, would negatively affect plans for a responsive pit manufacturing infrastructure that may be pivotal to further reducing the number of stockpile warheads—a cost-saving move for the nation. Similarly, the capability to manufacture replacement pits eliminates weapon-performance uncertainties that result from plutonium aging and is consistent with maintaining the moratorium on nuclear testing. Current plans afford numerous review opportunities until early in the next decade. National security for the US should be based on a prudent assessment of risks and not the overly optimistic and unrealistic evaluation contained in the APS position paper. Early planning and development are essential to avoid cost overruns and delays.REFERENCESection:ChooseTop of pageREFERENCE <<1. US Department of Energy, National Nuclear Security Administration, Report to Congressional Defense Committees on “An Enhanced Schedule for the Modern Pit Facility, February 2004. Available at http://www.fcnl.org/pdfs/nuc_mpfreport.pdf. Google Scholar© 2005 American Institute of Physics.

Remediating RDX‐Contaminated Ground Water with Permanganate

Ground water beneath the U.S. Department of Energy Pantex Plant is contaminated with the high explosive RDX (hexahydro-1,3,5-trinitro-1,3,5 triazine). The USDOE Innovative Treatment and Remediation Demonstration (ITRD) program identified in situ oxidation by permanganate as a technology fit for further investigation. We evaluated the efficacy of KMnO(4) to transform and mineralize RDX by determining degradation kinetics and carbon mass balances using (14)C-RDX. Aqueous RDX solutions (2-5 mg L(-1)) and RDX-contaminated slurries (50% solids, w/v) were treated with KMnO(4) at 1000, 2000, 4000, and 20000 mg L(-1). Treating an aqueous RDX solution of 2.8 mg L(-1) with 20000 mg KMnO(4) L(-1) decreased RDX to 0.1 mg L(-1) within 11 d while cumulative mineralization proceeded for 14 d until 87% of the labeled carbon was trapped as (14)CO(2). Similar cumulative mineralization was obtained when Pantex aquifer material was included in the solution matrix. Other experiments using 4000 mg KMnO(4) L(-1) showed that initial RDX concentrations (1.3-10.4 mg L(-1)) or initial pH (4-11) had little effect on reaction rates. Attempts to identify RDX degradates and reaction products showed that N(2)O was a product of permanganate oxidation and constituted 20 to 30% of the N balance. Time-course measurements of a (14)C-RDX solution treated with KMnO(4) revealed few (14)C-labeled degradates but through liquid chromatography-mass spectrometry (LC-MS) analysis, we present evidence that 4-nitro-2,4-diaza-butanol is formed. Aquifer microcosm studies confirmed that the transformation products not mineralized by KMnO(4) were much more biodegradable than parent RDX. These results indicate permanganate can effectively transform and mineralize RDX in the presence of aquifer material and support its use as an in situ chemical oxidation treatment for the Pantex perched aquifer.

Using Multimedia Modeling to Expedite Site Characterization

This paper uses two case studies of U.S. Department of Energy nuclear weapons complex installations to illustrate the integration of expedited site characterization (ESC) and multimedia modeling in the remedial action decision making process. CONCEPTUAL SITE MODELS, MULTIMEDIA MODELS, AND EXPEDITED SITE CHARACTERIZATION: Conceptual site models outline assumptions about contaminates and the spatial/temporal distribution of potential receptors. Multimedia models simulate contaminant transport and fate through multiple environmental media, estimate potential human exposure via specific exposure pathways, and estimate the risk of cancer and non-cancer health outcomes. ESC relies on using monitoring data to quantify the key components of an initial conceptual site model that is modified iteratively using the multimedia model. Two case studies are presented that used the ESC approach: Los Alamos National Laboratory (LANL) and Pantex. LANL released radionuclides, metals, and organic compounds, into canyons surrounding the facility. The Pantex Plant has past waste management operations which included burning chemical wastes in unlined pits, burying wastes in unlined landfills, and discharging plant wastewaters into on-site surface waters. The case studies indicate that using multimedia models with the ESC approach can inform assessors about what, where, and how much site characterization data needs to be collected to reduce the uncertainty associated with risk assessment. Lowering the degree of uncertainty reduces the time and cost associated with assessing potential risk and increases the confidence that decision makers have in the assessments performed.

Laboratory Investigation into the Contribution of Contaminants to Ground Water from Equipment Materials Used in Sampling

AbstractBenzene contamination was detected in well water samples from the Ogallala Aquifer beneath and adjacent to the Department of Energy's Pantex Plant near Amarillo, Texas. This study assessed whether or not the materials used in multilevel sampling equipment at this site could have contributed to the contaminants found in well water samples. As part of this investigation, laboratory testing of the sample equipment material was conducted.Results from the laboratory tests indicated three different materials from two types of multilevel samplers did, in fact, contribute volatile and semivolatile organic compounds to the ground water samples from static leach tests that were conducted during an eight week period. The nylon‐11 tubing contributed trace concentrations of benzene (1.37 μg/L) and relatively high concentrations of the plasticizer N‐butylbenzenesulfonamide (NBSA) (764 mg/L) to the water; a urethane‐coated nylon well liner contributed relatively high concentrations of toluene (278 μg/L) and trace amounts of NBSA; and a sampling port spacer material made of nylon/polypropylene/polyester‐composite contributed trace amounts of toluene and NBSA.While the concentrations of benzene and toluene measured in the laboratory tests were below the concentrations measured in actual ground water samples, the concentrations of organics from these equipment materials were sufficient to render the results reported for the ground water samples suspect.

In Situ Biodegradation of High Explosives in Soils: Field Demonstration

The first field pilot-scale demonstration of a technology for in situ remediation of vadose zone soils contaminated with high explosives (HEs) has been performed at the Department of Energy's Pantex Plant. The HEs of concern at the demonstration site were hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and the 2,4,6-trinitrotoluene (TNT) metabolite 1,3,5-trinitrobenzene (TNB). Concentrations ranged from 70 ppm, above the (prior to 1999) risk reduction clean-up criteria of 2.6 and 0.51 ppm, respectively. The shallow (<10 m depth) soils at the site could not be excavated due to the presence of buried utilities. Based on previous laboratory studies, it was found that the contaminated soils had indigenous microbial populations that could be stimulated to degrade the RDX and TNB anaerobically. A 5-spot well pattern with injection at the central well and extraction at the four outer wells (each 4.6 m from the injection well) was used to flood the target vadose zone soils with nitrogen gas with the intent of stimulating the activity of the HE degraders. The system was monitored periodically for gas composition as well as HE concentrations and microbial activity in retrievable soil samples. After 295 days of in situ treatment, the average target HE concentrations were approximately one-third lower than the initial site averages. Operation of the pilot-scale treatment system continues.

A new approach to a site radiological control manual.

The Pantex Plant significantly revised its Radiological Control Manual to improve its usability, streamline plant procedures, and clarify conflicting guidance. This article overviews the process used to develop the new Radiological Control Manual.

Production planning for a project job shop, with application to disassembly, evaluation and maintenance of nuclear weapons

Production planning in some make-to-order operations bears considerable resemblance to resource-constrained project scheduling. This type of operation is referred to as a 'project job shop.' The practical problem that provides motivation for the methodology developed in this paper is such a production environment - the Department of Energy Pantex plant in Amarillo, Texas, where nuclear weapons are maintained and dismantled. In order to be useful in practice at Pantex, a production planning model must be able to handle a few hundred tasks (at least), with about 30 different types of facility resources, and 80-90 technicians who hold different combinations of 90-100 different certifications (qualifications to perform specific tasks). An approach has been developed to this production planning problem that is also transferable to project scheduling environments. The formulation uses continuous variables rather than the discrete variables commonly used in project scheduling formulations. This formulation allows time periods of variable lengths, and accepts arbitrary time boundaries (daily, weekly, monthly, etc.) within which resource availability is measured. The solution approach for this formulation is described, and two example problems are used to illustrate application of the model.

Biodegradation of RDX in Unsaturated Soil

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a military explosive that is a common soil and groundwater contaminant at facilities that manufacture, handle, and dispose of munitions. One such facility is the U.S. Department of Energy Pantex Plant, the focus of this research in which the feasibility of in situ bioremediation of contaminated soil in the vadose zone was assessed. A batch technique using 14C-RDX was developed to investigate the degradation of RDX under aerobic, microaerobic, and anaerobic conditions. In addition, the effect of nutrients (organic carbon and phosphorus) on biodegradation rates was studied. The extent of mineralization was quantified by monitoring the production of 14CO2, and RDX biodegradation rates were estimated for each environmental condition. The results showed that RDX degraders were indigenous to the contaminated soil and degraded RDX to a significant extent under anaerobic conditions. Little biotransformation was observed under aerobic conditions. The addition of a biodegradable organic carbon source significantly increased the RDX biodegradation rate. Under appropriate environmental conditions, significant mineralization of RDX also was observed. The half-lives for the degradation of RDX under anaerobic conditions were approximately 60 days and decreased to approximately 40 days with nutrient addition. In contrast, the half-life for aerobic degradation was on the order of 1000 days, with an upper 95% confidence interval approaching infinity.

The Quality Evaluation Program for Plutonium Pits at the U.S. DOE Pantex Plant

The United States Department of Energy Pantex Plant quality evaluation program for plutonium pits is an extensive program that includes 1) weigh and leak check system; 2) radiography; and 3) dye penetrant testing. Successful completion of these diagnostics qualifies a pit to remain in the active status stockpile program. The use of lead aprons and a robot when handling the plutonium pits minimizes personnel exposures to ionizing radiation. All personnel exposures to ionizing radiation at Pantex Plant are As Low As Reasonably Achievable.

Pantex: safety in nuclear weapons processing.

The Pantex Plant, located in the Texas panhandle near Amarillo, is a major Department of Energy (DOE) participant in maintaining the safety of the nation's nuclear weapons resources and protecting the employees, public, and environment. With more than 168,000 person-years of operations involving nuclear materials, explosives, and hazardous chemicals, Pantex has maintained a notable safety record. This article overviews the nuclear weapon activities at Pantex and describes their safety culture.

The dissolution vessel for plutonium pits at the U.S. DOE Pantex Plant.

The U.S. DOE Pantex Plant has been given the mission to recertify and requalify plutonium pits for reuse in existing War Reserve nuclear weapons. The first process common to both recertification and requalification is cleaning the plutonium pit. The pit will be cleaned in a dissolution vessel using N-methyl pyrrolidone (NMP) solvent. The recertification and requalification programs are both in the design concept phase at Pantex Plant The U.S. DOE Pantex Plant secures the national security of the United States by using safe vessels for cleaning plutonium pits in a manner that protects the health and safety of employees, the public and the environment.

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.

Swords into Plowshares: Nuclear Weapon Dismantlement, Evaluation, and Maintenance at Pantex

The end of the Cold War changed the missions of facilities in the US nuclear weapons complex. They ceased production of new weapons and focused on dismantling old weapons and maintaining the safety, security, and reliability of those remaining. The Pantex Plant, operated for the US Department of Energy (DOE) by the Mason and Hanger Corporation, is the sole assembly and disassembly facility for dismantlement, evaluation, and maintenance activities for the US nuclear stockpile. We developed a decision support tool, the Pantex Process Model (PPM), to help Pantex plan capacity and deploy resources to meet its new requirements. Using the PPM, Pantex has provided critical input to help the US form and defend positions during arms-control-treaty negotiations. It has changed the way Pantex and the DOE evaluate resource requirements in planning future workloads. It has also led to an innovative cooperative agreement among Pantex, the Transportation Safeguards Division of DOE, and the Department of Defense (DOD) that resulted in Pantex exceeding weapon-dismantlement goals.