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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Contaminant Migration Modeling to Support the In Situ Decommissioning of Hardened Nuclear Facilities - 20215

The decommissioning of hardened nuclear facilities provides a unique challenge in balancing current worker dose with exposure to future receptors and media. In situ decommissioning (ISD) is a cost-effective and safe option for the closure of such facilities but requires a detailed understanding of the threat that radioactive and hazardous constituents remaining in the facilities pose to groundwater and surrounding surface water. The Savannah River Site (SRS) extensively employs contaminant migration models within the decommissioning process to develop site-specific removal, grouting, and monitoring strategies in support of safe and effective final end states of nuclear facilities. This work discusses the use of contaminant migration modeling in the ISD process at SRS, including specific examples from the closure of P-Reactor and R-Reactor, Building 235-F, F-Canyon and F/H Laboratory Complex. Migration models developed during the closure of P-Reactor and R-Reactor were divided into four source areas: the reactor vessel, the process area, the disassembly basin, and the purification wing. Each source area was assigned a specific inventory and migration pathway and was then subject to varying hypothetical removal, capping, and grouting schemes. Modeling indicated that groundwater Maximum Concentration Limits (MCLs) might be exceeded if no action was taken for eleven and ten constituents of concern (COCs) at P-Reactor and R-Reactor, respectively. These exceedances could occur in as few as 200 to 500 years. Alternatively, the migration modeling demonstrated that the selected ISD actions reduced contaminant mobility which allowed for significant radioactive decay and resulted in fewer predicted exceedances of groundwater MCLs (five COCs for P-Reactor; eight COCs for R-Reactor). In response to the modeling results for P-Reactor and R-Reactor, effectiveness monitoring programs were developed to target contaminants, specific to each reactor, that may migrate to groundwater. Contaminant migration modeling also revealed that roof collapse was a large factor in the release of COCs to the environment, giving rise to roof improvements, and an inspection and vegetation control program to ensure roof stability over time. Contaminant migration modeling is also aiding in the closure planning for hardened facilities in F Area. Building 235-F housed the Actinide Billet Line, which produced Np-237 billets for irradiation in SRS reactors, and the Plutonium Fuel Form (PuFF) facility that produced Pu-238 heat sources for the space program. As a result of these missions, areas within Building 235-F contain considerable residual amounts of both Pu-238 and Np-237. Contaminant migration modeling of Building 235-F was originally performed in 2012 to identify the feasibility of ISD and the amount of radioactive material removal required to prevent the exceedance of groundwater MCLs. The original model indicated that a 60% reduction in the PuFF facility Pu-238 inventory could keep groundwater concentrations below standards, while Np-237 did not pose a threat to groundwater. However, updates to the model with an emphasis on source impact pathways revealed that, due to the orientation of the source areas relative to groundwater flow, no amount of reasonable removal of Pu-238 would keep groundwater concentrations below MCLs and that Np-237 could be a large contributor to localized MCL exceedances. With this insight, the refined 2019 model is being used to assist in the development of grouting plans specific to each facility source area, where bentonite may be utilized to slow the migration of Pu-238 and its daughter products from the PuFF facility and a reducing grout may decrease Np-237 transport by ensuring the nuclide remains in the less mobile +IV oxidation state. The beginning phases of contaminant migration modeling are underway for F-Canyon and associated facilities using lessons learned from the Reactors and Building 235-F. A contaminant migration pathway, similar to the pathway used for the reactor vessels, is being developed for the hot and warm canyons. The F-Canyon inventories are being spatially refined to identify specific and localized source zones, comparable to Building 235-F, that may impact groundwater. Contaminant migration modeling provides vital input within the ISD process, from facility investigation to post closure effectiveness monitoring, making it a valuable tool in the development of safe and effective end states for hardened nuclear facilities at SRS. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Custom Equipment Development for Processing of Surplus Plutonium

The Strategic Laboratory Assessment (SLA), a collaborative team of SRNL and ORNL personnel, has been established to advance the objectives of the Surplus Plutonium Disposition (SPD) Project, by identifying and developing technologies to accelerate disposition, reduce life cycle costs, minimize worker radiation exposure, improve worker safety, and minimize Surplus Plutonium Disposition Program risks. [1] The SLA team has identified can cutting and plutonium (Pu) oxide size reduction as two glovebox processes where technology enhancements would be valuable. The DOESTD-3013 package currently in use for Pu downblending requires cutting two nested cans before the inner convenience can that holds the Pu oxide may be accessed for further processing. A rotary tubing-style cutter is used for opening the 3013 packages within the glovebox. Collet changeouts are required between cutting of the outer and inner cans. The SLA team is currently developing and testing an adjustable-clamp can cutter design that eliminates collet changeouts and allows cutting of the outer and inner can at the same time, resulting in significant reduction of radiological dose and process time, as well as improved ergonomics. To meet the Pu oxide particle size requirement, size reduction of Pu oxide agglomerations must be performed within the process gloveboxes. The SLA team has identified jaw crushing technology as an alternative to the currently employed rotary mill. Jaw crusher advantages include reduced dust within the glovebox, increased batch sizes, and easier integration with other glovebox processes due to the flow-through nature of jaw crushing. Commercially manufactured jaw crushers are either too large and/or too heavy for implementation in the SPD gloveboxes, so the SLA team is developing and testing a custom jaw crusher to meet the needs of the SPD Project.

Krementz, Daniel [Savannah River National Laborato↗
DOE OSTI2025

Control Selection for the Neutralization Tank in the Aqueous Recovery System at the Savannah River Plutonium Processing Facility

The Aqueous Recovery System (ARS) at the Savannah River Plutonium Processing Facility (SRPPF) recovers and purifies plutonium (Pu) using aqueous chemistry techniques. The neutralization tanks in the ARS collect waste streams with various impurities and greatly reduced concentrations of Pu than are produced during aqueous processing. Criticality safety is primarily achieved in the ARS by using geometrically favorable process vessels. However, due to the geometry of neutralization tanks, each tank is administratively limited to no more than 450 g Pu, thus representing the transition from geometry to mass control. To ensure that this mass limit is not exceeded, an administrative control requires taking two samples of any solution to be sent to a neutralization tank. Normal operations are expected to result in less than 50 g Pu in a neutralization tank filled to its capacity of 250 L. Process upsets may cause an inadvertent transfer of up to 1000 g Pu to a neutralization tank, producing a system that is potentially not subcritical for all possible configurations of the tank. To ensure that a neutralization tank remains safety subcritical, passive engineered controls (e.g. changing tank geometry or adding fixed poisons), active engineered controls (e.g. interlocks), and administrative controls (e.g. soluble poisons and valve isolation) were considered and their viability evaluated. Ultimately, the team chose an administrative, dual-valve isolation strategy. This paper will thoroughly discuss the various control strategy options and why many of the options were not feasible for maintaining criticality safety.

Dressman, Phillip M. [Savannah River Nuclear Solut↗
DOE OSTI2025

Control Selection for the Neutralization Tank in the Aqueous Recovery System at the Savannah River Plutonium Processing Facility

The Aqueous Recovery System (ARS) at the Savannah River Plutonium Processing Facility (SRPPF) recovers and purifies plutonium (Pu) using aqueous chemistry techniques. The neutralization tanks in the ARS collect the waste streams, containing various impurities and greatly reduced concentrations of Pu, that are produced during aqueous processing. Criticality safety is primarily achieved in the ARS by using geometrically favorable process vessels. However, due to the geometry of neutralization tanks, each tank is administratively limited to no more than 450 g Pu, thus representing the transition from geometry to mass control. To ensure that this mass limit is not exceeded, an administrative control requires taking two samples of any solution to be sent to a neutralization tank. Normal operations are expected to result in less than 50 g Pu in a neutralization tank filled to its capacity of 250 L. Process upsets may cause an inadvertent transfer of up to 1000 g Pu to a neutralization tank, producing a system that is potentially not subcritical for all possible configurations of the tank. To ensure that a neutralization tank remains safety subcritical, passive engineered controls (e.g.changing tank geometry or adding fixed poisons), active engineered controls (e.g. interlocks), and administrative controls (e.g. soluble poisons and valve isolation) were considered and their viability evaluated. Ultimately, the team chose an administrative, dual-valve isolation strategy. This paper will thoroughly discuss the various control strategy options and why many of the options were not feasible for maintaining criticality safety.

Dressman, Phillip M. [Savannah River Nuclear Solut↗
DOE OSTI2025

Use of Captured CO2 for Production of Sustainable Polyurethane Foams in Automotive Applications

Captured CO2 has been investigated as a feedstock for the production of polyurethane (PU) foams for automotive applications. Previous work has shown successful incorporation of CO2 into polyols via three distinct reaction pathways. These CO2-derived polyols, as well as several commercially available polyols with varying CO2 content, were used to produce PU foams for automotive seating and NVH (noise, vibration, and harshness) applications. Foam formulations were optimized to maximize sustainable content while maintaining manufacturability constraints and performance requirements for each end use application. PU foams were first formulated at lab scale to confirm free rise and molded foam properties, then scaled up to pilot and industrial scales to evaluate production manufacturing feasibility. Finally, CO2-derived foams were used to produce molded components for end use product validation. Life cycle assessment (LCA) was used to quantify the environmental impact of using captured CO2 and bio-renewable content into polyols and PU foams through the metrics of global warming potential and embodied energy. Tradeoffs among environmental impacts, energy usage, manufacturability, and PU foam performance from the incorporation of CO2 and bio-renewable content will be discussed.

Lee, Ellen [Ford Motor Company]↗
DOE OSTI2020

Materials Data on Pu2Si4Tc3 by Materials Project

Pu2Tc3Si4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Pu+4.50+ is bonded in a 1-coordinate geometry to four Tc3- atoms. There are a spread of Pu–Tc bond distances ranging from 2.84–3.20 Å. There are two inequivalent Tc3- sites. In the first Tc3- site, Tc3- is bonded in a 12-coordinate geometry to four equivalent Pu+4.50+ and six Si atoms. There are a spread of Tc–Si bond distances ranging from 2.50–2.52 Å. In the second Tc3- site, Tc3- is bonded in a 7-coordinate geometry to two equivalent Pu+4.50+ and five Si atoms. There are a spread of Tc–Si bond distances ranging from 2.42–2.50 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 6-coordinate geometry to four Tc3- atoms. In the second Si site, Si is bonded in a 4-coordinate geometry to four Tc3- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuNi5 by Materials Project

PuNi5 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Pu is bonded in a 6-coordinate geometry to eighteen Ni atoms. There are six shorter (2.83 Å) and twelve longer (3.15 Å) Pu–Ni bond lengths. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 12-coordinate geometry to three equivalent Pu and six equivalent Ni atoms. All Ni–Ni bond lengths are 2.43 Å. In the second Ni site, Ni is bonded to four equivalent Pu and eight Ni atoms to form a mixture of edge, face, and corner-sharing NiPu4Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.45 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuH18C3S3(O2F)9 by Materials Project

Pu(H2O)9(CF3)3(SO3)3 crystallizes in the hexagonal P6_3/m space group. The structure is zero-dimensional and consists of six fluoroform molecules, six sulfur trioxide molecules, and two Pu(H2O)9 clusters. In each Pu(H2O)9 cluster, Pu5+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are six shorter (2.50 Å) and three longer (2.58 Å) Pu–O bond lengths. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to one Pu5+ and two equivalent H1+ atoms. In the second O2- site, O2- is bonded in a water-like geometry to one Pu5+ and two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuGa6 by Materials Project

PuGa6 crystallizes in the tetragonal P4/nbm space group. The structure is three-dimensional. Pu is bonded to twelve Ga atoms to form a mixture of edge and face-sharing PuGa12 cuboctahedra. There are four shorter (3.10 Å) and eight longer (3.18 Å) Pu–Ga bond lengths. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 4-coordinate geometry to one Pu and three Ga atoms. There are one shorter (2.56 Å) and two longer (2.62 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 9-coordinate geometry to four equivalent Pu and five Ga atoms. The Ga–Ga bond length is 2.41 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2O3 by Materials Project

Pu2O3 is Spinel-derived structured and crystallizes in the trigonal R-3 space group. The structure is three-dimensional. there are four inequivalent Pu3+ sites. In the first Pu3+ site, Pu3+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing PuO6 octahedra. The corner-sharing octahedra tilt angles range from 57–58°. There are a spread of Pu–O bond distances ranging from 2.29–2.41 Å. In the second Pu3+ site, Pu3+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing PuO6 octahedra. The corner-sharing octahedra tilt angles range from 57–58°. There are a spread of Pu–O bond distances ranging from 2.30–2.40 Å. In the third Pu3+ site, Pu3+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing PuO6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are four shorter (2.34 Å) and two longer (2.35 Å) Pu–O bond lengths. In the fourth Pu3+ site, Pu3+ is bonded to six equivalent O2- atoms to form a mixture of distorted edge and corner-sharing PuO6 octahedra. The corner-sharing octahedral tilt angles are 57°. All Pu–O bond lengths are 2.32 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four Pu3+ atoms to form a mixture of edge and corner-sharing OPu4 tetrahedra. In the second O2- site, O2- is bonded to four Pu3+ atoms to form a mixture of edge and corner-sharing OPu4 tetrahedra. In the third O2- site, O2- is bonded to four Pu3+ atoms to form a mixture of edge and corner-sharing OPu4 tetrahedra. In the fourth O2- site, O2- is bonded to four Pu3+ atoms to form a mixture of edge and corner-sharing OPu4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuPd3 by Materials Project

PuPd3 is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pu is bonded to twelve Pd atoms to form a mixture of corner, edge, and face-sharing PuPd12 cuboctahedra. All Pu–Pd bond lengths are 2.93 Å. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded to four equivalent Pu atoms to form a mixture of distorted corner and edge-sharing PdPu4 cuboctahedra. In the second Pd site, Pd is bonded in a distorted square co-planar geometry to four equivalent Pu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuBi3 by Materials Project

PuBi3 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pu is bonded to twelve Bi atoms to form PuBi12 cuboctahedra that share corners with four equivalent PuBi12 cuboctahedra, edges with eight equivalent PuBi12 cuboctahedra, edges with sixteen equivalent BiPu4Bi8 cuboctahedra, faces with four equivalent PuBi12 cuboctahedra, and faces with eight equivalent BiPu4Bi8 cuboctahedra. There are four shorter (3.26 Å) and eight longer (3.59 Å) Pu–Bi bond lengths. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded to four equivalent Pu and eight Bi atoms to form distorted BiPu4Bi8 cuboctahedra that share corners with twelve equivalent BiPu4Bi8 cuboctahedra, edges with eight equivalent PuBi12 cuboctahedra, edges with eight equivalent BiPu4Bi8 cuboctahedra, faces with four equivalent PuBi12 cuboctahedra, and faces with ten equivalent BiPu4Bi8 cuboctahedra. There are four shorter (3.26 Å) and four longer (3.59 Å) Bi–Bi bond lengths. In the second Bi site, Bi is bonded in a square co-planar geometry to four equivalent Pu and eight equivalent Bi atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuHg3 by Materials Project

PuHg3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pu is bonded in a distorted body-centered cubic geometry to fourteen Hg atoms. There are eight shorter (3.19 Å) and six longer (3.68 Å) Pu–Hg bond lengths. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded in a distorted body-centered cubic geometry to four equivalent Pu and four equivalent Hg atoms. All Hg–Hg bond lengths are 3.19 Å. In the second Hg site, Hg is bonded in a 8-coordinate geometry to six equivalent Pu and eight equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuSn2 by Materials Project

PuSn2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Pu is bonded in a 10-coordinate geometry to ten Sn atoms. There are a spread of Pu–Sn bond distances ranging from 3.19–3.40 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a distorted square co-planar geometry to four equivalent Pu atoms. In the second Sn site, Sn is bonded in a 12-coordinate geometry to six equivalent Pu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuAg3 by Materials Project

PuAg3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pu is bonded in a distorted body-centered cubic geometry to fourteen Ag atoms. There are eight shorter (3.07 Å) and six longer (3.54 Å) Pu–Ag bond lengths. There are two inequivalent Ag sites. In the first Ag site, Ag is bonded to four equivalent Pu and four equivalent Ag atoms to form a mixture of distorted edge, face, and corner-sharing AgPu4Ag4 tetrahedra. All Ag–Ag bond lengths are 3.07 Å. In the second Ag site, Ag is bonded in a 8-coordinate geometry to six equivalent Pu and eight equivalent Ag atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuIn7Pt2 by Materials Project

PuPt2In7 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pu is bonded to twelve In atoms to form a mixture of corner and face-sharing PuIn12 cuboctahedra. There are four shorter (3.20 Å) and eight longer (3.32 Å) Pu–In bond lengths. Pt is bonded in a body-centered cubic geometry to eight In atoms. There are four shorter (2.76 Å) and four longer (2.82 Å) Pt–In bond lengths. There are three inequivalent In sites. In the first In site, In is bonded in a distorted square co-planar geometry to four equivalent Pu atoms. In the second In site, In is bonded to four equivalent Pt atoms to form a mixture of corner and edge-sharing InPt4 tetrahedra. In the third In site, In is bonded in a 2-coordinate geometry to two equivalent Pu and two equivalent Pt atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuAl2Pd5 by Materials Project

PuPd5Al2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pu is bonded to twelve Pd atoms to form a mixture of corner and face-sharing PuPd12 cuboctahedra. There are four shorter (2.95 Å) and eight longer (3.03 Å) Pu–Pd bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a distorted square co-planar geometry to four equivalent Pu atoms. In the second Pd site, Pd is bonded in a 6-coordinate geometry to two equivalent Pu and four equivalent Al atoms. There are two shorter (2.59 Å) and two longer (2.63 Å) Pd–Al bond lengths. Al is bonded in a body-centered cubic geometry to eight equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuPb2 by Materials Project

PuPb2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Pu is bonded in a 10-coordinate geometry to ten Pb atoms. There are a spread of Pu–Pb bond distances ranging from 3.37–3.48 Å. There are two inequivalent Pb sites. In the first Pb site, Pb is bonded in a distorted rectangular see-saw-like geometry to four equivalent Pu atoms. In the second Pb site, Pb is bonded in a 12-coordinate geometry to six equivalent Pu atoms.

36 MATERIALS SCIENCE↗