Portsmouth Gaseous Diffusion Plant Research Articles

The Nuclear Legacy in Appalachia.

Nestled in the rolling hills of Appalachia Ohio is a reminder of the role that the region played in winning the Cold War. For more than 40 years in rural Pike County, the 3,700-acre Portsmouth Gaseous Diffusion Plant (PORTS), or the “A-Plant” as the locals refer to it, enriched uranium for use in nuclear weapons. While the facility produced nuclear fuel for national security, it simultaneously exposed plant workers to chemicals and radiation and discharged pollution into the surrounding community. The A-Plant is now being demolished and the site repurposed. However, the site continues to affect the community as, for example, a middle school near it was closed in late spring of 2019 due to alarming levels of radiation detected in the building.

Application of the 226Ra–230Th–234U and 227Ac–231Pa–235U radiochronometers to UF6 cylinders

Uranium-series radiometric dating was performed on two well-pedigreed UF6 cylinder samples containing highly enriched uranium that were in use at the Portsmouth Gaseous Diffusion Plant between the mid-1970s and mid-1980s. Daughter–parent (i.e. 231Pa–235U, 230Th–234U) radiometric ages determined on solid heel materials (e.g. UO2F2, UF4) recovered from the emptied cylinders are unrealistically old due to the preferential sequestration of progeny isotopes relative to uranium within the solid heels. However, limited elemental fractionation amongst the progeny isotopes themselves in the heel material allowed for realistic age constraints on the fill dates of the UF6 cylinders to be extracted from the granddaughter–daughter systems (i.e. 226Ra–230Th, 227Ac–231Pa).

Traceable Determination of the Absolute <newline/>Neutron Emission Yields of <formula formulatype="inline"><tex Notation="TeX">${{\rm UO}_2}{{\rm F}_2}$</tex></formula> <newline/>Working Reference Materials

The nuclear material contained in the process equipment of a uranium enrichment plant (referred to as holdup) is an important component of the overall nuclear material inventory for the plant. Accurate quantification and verification of holdup is needed to improve international safeguards and nuclear material accountancy. This is also needed for criticality safety and waste disposition. Passive neutron and gamma-ray nondestructive assay (NDA) methods are used to measure the holdup in process equipment. A key advantage of neutron measurements is that neutrons are highly penetrating and can be measured through thick walled equipment. The dominant source of neutrons in the UO2F2 holdup is from the 19F(α,n)22Na reaction resulting from 234U alpha decay when uranium is enriched. There is a considerable spread between different historic determinations of the 19F(α,n) yield from uranium which limits the accuracy of modeling and the calibration of NDA instruments. Furthermore, the compound form and presence of water also significantly affects the neutron emission rate from the holdup. This paper describes a series of experimental measurements performed at Los Alamos National Laboratory (LANL) to determine the absolute neutron emission yield from 10 different UO2F2 working reference materials (WRMs) fabricated at the Portsmouth Gaseous Diffusion Plant (PGDP). The Mini Epithermal Neutron Multiplicity Counter (Mini ENMC) and a NIST certified 252Cf neutron source were used for these measurements. The high efficiency and short die-away time of the Mini ENMC provides the high measurement precision needed to certify the neutron emission yield. The experiment was designed to achieve sub 1% accuracy in the net counting rate on each item and to provide assurance that important factors such as instrument stability, item placement and background were well understood. The traceable neutron yields measured from the WRMs were used to determine a more accurate neutron yield for the UO2F2 material. The results were compared to historical neutron emission rates. The F(α,n) data obtained from these measurements directly supports nuclear safeguards for NDA of uranium holdup and provides a more accurate calibration for new and existing NDA detector systems.

Characterization and fate of polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in soils and sediments at the Portsmouth Gaseous Diffusion Plant, Ohio

The U.S. Department of Energy Portsmouth Gaseous Diffusion Plant is in the early stages of decommissioning and decontamination. During operations, the site drew a large amount of electric power and had multiple large switchyards on site. These are a source of polychlorinated biphenyls (PCB) contamination to both on-site and off-site streams. Some soil remediation has been completed in the main switchyard. During 2011 and 2012, fifteen sites were sampled at the surface (<10cm) and subsurface (20–30cm) to characterize the extent of PCB contamination, to identify weathering and migration of PCB contamination and to explore potential polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) contamination due to transformer fires and explosions in the 1950s and 1960s. Stagnant sites tended to exhibit more migration of contamination to deeper sediments than sites with fast-moving waters, and the highest concentrations were found at the bottom of a settling pond. A signature set of five dioxin-like PCBs were consistently found across the site with higher concentrations in carbon rich surface sediments. PCB concentrations had a significant inverse correlation with clay content, suggesting that PCBs did not bind to clays at this site. Remediation has reduced PCB concentrations throughout the site compared to levels found in previous studies and long-term upkeep of sediment lagoons is necessary to retain PCB and dioxin-rich sediments. The flow regimen, organic carbon and clay content play a very important role in the fate of PCBs in the environment at the surface as well as downward migration.

Monitoring large enrichment plants using thermal imagery from commercial satellites: A case study

Thermal imagery from currently operating commercial satellites is an interesting candidate technology for monitoring certain types of fissile material production sites. Potential applications include the Fissile Material Cutoff Treaty (FMCT) or a Fissile Material Production Moratorium. To help determine the capabilities and limitations of such imagery as a monitoring tool, I have examined archived LANDSAT‐5 images of the Portsmouth Gaseous Diffusion Plant, a large U.S. uranium‐enrichment facility in Ohio. My analysis indicates that large‐scale gaseous diffusion plants (GDPs) can very likely be recognized as operational with thermal imagery throughout most of the year in clear weather conditions. It may also be possible to identify certain other large‐scale changes in operations, such as the shut‐down of a single process building in a plant, by comparing rooftop temperatures of neighboring operational process buildings. However, uncertainties in the current data set prevent a definitive conclusion regarding the latter capability. This study identifies intrinsic weaknesses, including vulnerability to countermeasures, that prevent thermal imagery from satellites (at current resolutions) from being a robust stand‐alone verification tool, even for very large plants. Nonetheless, the imagery may be useful to trigger an on‐site inspection, to alert and train inspectors prior to an inspection, and to reduce the frequency of on‐site inspections required at a given site. It could have immediate utility for monitoring the two large GDPS in the United States and the French plant at Tricastin, and possibly for determining the operational status of two GDPS in China as well ‐ a total of five plants worldwide. The ease of acquisition and modest cost of thermal commercial imagery further increase its attractiveness as a verification tool.

DC Resistivity Monitoring of Potassium Permanganate Injected to Oxidize TCE In Situ

The U.S. Department of Energy's Office of Science and Technology selected the X‐701B Site at the Portsmouth Gaseous Diffusion Plant, Piketon, Ohio, for a demonstration of in situ chemical oxidation. The goal was to oxidize trichloroethylene (TCE), present in both the soil and groundwater of the local Gallia aquifer, by circulating a solution of potassium permanganate (KMnO4) between two horizontal wells.Potassium permanganate is a salt. Laboratory measurements showed that the addition of 1.0% of potassium permanganate increased the fluid conductivity of a Portsmouth groundwater sample from 339 to 7,250 mS/m, or equivalently, decreased the electrical resistivity from 2.9 ohm‐m to 0.14 ohm‐m. Although the contaminated Gallia aquifer is only about 1.5 m thick at this site and is overlain by nearly 8 m of Minford clay, geophysical modeling showed that if the injection flooded a sufficient portion of the aquifer then the change in resistivity would be detectable from the surface using DC resistivity. Field mea...

A Methodology for Establishing Cleanup Objectives in the Unsaturated Soil Zone Using Sensitivity and Uncertainty Analysis for Chemical Fate and Transport

To support the Corrective-Measures and Cleanup-Alternatives Studies (CMS) prepared by Science Applications International Corporation (SAIC) at the Portsmouth Gaseous Diffusion Plant (PORTS) in Portsmouth, Ohio, a soil-leaching numerical analysis was conducted to help establish cleanup objectives for deep-soil contamination. For approximately 60 pollutants that exist at the PORTS site, the study defined those deep-soil concentrations that would most likely not cause groundwater contamination in excess of U.S. Environmental Protection Agency (USEPA) guidelines. These values were then used as the technical basis for defining soil-cleanup goals. Numerical modeling of environmental systems provides project managers with unique information that is not available from other sources. With its ability to quantify the important aspects of problem physics, modeling allows one to rapidly accumulate the physical insight needed to solve a problem in a systematic and focused manner. This increased understanding acquired early in the planning stages of a project permits managers to make decisions that are typically more thorough, cost effective, and defensible. This article describes one such numerical study conducted jointly by the Oak Ridge National Laboratory (ORNL) and SAIC for the PORTS.

Technetium-99 Removal from Process Solutions and Contaminated Groundwater

Abstract The predominant form of technetium under oxic conditions is the pertechnetate anion (TcO4 −), which is highly soluble in water and readily mobile in the environment. Technetium-99 is of particular concern because of its persistence and mobility. Various equipment decontamination and uranium recovery operations at the Portsmouth Gaseous Diffusion Plant generate a “raffinate” waste stream characterized by toxic heavy metals, high concentration of nitric acid, and low levels of radionuclides (235u and 99Tc). Dilution and adjustment of solution pH to a value of 8.2 to 8.5 precipitates a heavy-metals-sludge and a filtrate. The removal of 99Tc from these waste streams and from contaminated groundwater can be accomplished using anionic ion-exchange resins. Batch equilibrium and packed column breakthrough and regeneration studies were performed using inorganic sorbenta and organic ion-exchange resins (Dowex SRB-OH and Reillex resins). These studies were performed on actual and surrogate raw raffinates, f...

Solidification/stabilization of technetium in cement-based grouts

Mixed low-level radioactive and chemically hazardous process treatment wastes from the Portsmouth Gaseous Diffusion Plant are stabilized by solidification in cement-based grouts. Conventional portland cement and fly-ash grouts have been shown to be effective for retention of hydrolyzable metals (e.g., lead, cadmium, uranium, and nickel) but are marginally acceptable for retention of radioactive 99Tc, which is present in the waste as the highly mobile pertechnetate anion. Addition of ground blast furnace slag to the grout is shown to reduce the leachability of technetium by several orders of magnitude. The selective effect of slag is believed to be due to its ability to reduce Tc (VII) to the less soluble Tc (IV) species.

On-Line Measurement of the Isotopic Composition of Uranium in UF6

An in-line monitor used initially to continuously measure the 235U enrichment in liquid UF6 at the Portsmouth Gaseous Diffusion Plant has recently been recalibrated to provide continuous measurements of both 234U and 235U. The instrument using both a gamma-ray detector for 235U and a neutron detector for 234U has produced data that is in good agreement with precision mass spectrometric measuremic measurements made on related samples of UF6. Studies now in process suggest that the use of such minor isotope data will provide. the safeguards inspector with a useful additional tool in his efforts to independently verify the operations and nuclear material accountancy records of an isotope separation plant. The preliminary results indicate that an instrument originally developed to meet the operational problems of the plant can also make a significant contribution to the difficult problems of providing effective safeguards for an enrichment plant.