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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Plutonium and Cerium Perrhenate/Pertechnetate Coordination Polymers and Frameworks

Spent nuclear fuel (SNF) contains transuranic and lanthanide species, which are sometimes recovered and repurposed. One particularly problematic fission product, 99 TcO 4 – , hampers this recovery via coextraction with high valence metals, perhaps by complexation during aqueous reprocessing of SNF. There is limited molecular-level knowledge concerning the coordination chemistry between TcO 4 – or its well-known surrogate ReO 4 – and transuranic/lanthanide species. In the current study, we investigated the coordination of ReO 4 – /TcO 4 – with plutonium and cerium cations by structural and chemical characterization of a series of isolated extended solids. In this study, Ce represents both trivalent lanthanides and is considered a surrogate for Pu, respectively, in its common trivalent and tetravalent oxidation states. The structural elucidation of the seven isolated crystalline solids revealed that ReO 4 – /TcO 4 – directly connects to Pu IV , Pu VI O 2 2 + , Ce III , and Ce IV in the terminal and bridging coordination modes, leading to 1-, 2-, and 3-dimensional frameworks. For example, ReO 4 – coordination to Pu(IV) formed a 1D chain or 2D framework, isostructural with previously isolated Th(IV) compounds. However, Pu VI O 2 2 + alternating with ReO 4 – led to a unique 1D chain, different from the prior-reported U(VI)/Np(VI)-ReO 4 – /TcO 4 – structures. Coordination of ReO 4 – /TcO 4 – with Ce(III) promotes the assembly of 3D frameworks. Finally, attempted synthesis of a Ce(IV)-ReO 4 – compound resulted in a 2D framework with a mixed-valence Ce III/IV . The highly acidic reaction conditions supported the reduction of both Ce IV and Tc VII , challenging isolation of compounds featuring these species. Only one TcO 4 -containing structure was obtained in this study (Ce III –TcO 4 3D framework), vs the six total Ce/Pu-ReO 4 compounds. Furthermore, our three Pu-ReO 4 crystal structures are the first reported and translated to atomic-level information about Pu-TcO 4 coordination in nuclear fuel reprocessing scenarios, in addition to broadening our knowledge of bonding trends in the early, high-valence actinides.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Green Catalysts for Reprocessing Thermoset Polyurethanes

Polyurethane (PU) thermosets are usually landfilled at the end of their service lifetimes and cannot be recycled through conventional means. Although dibutyltin dilaurate (DBTDL) is an effective catalyst for reprocessing PU thermosets, organotins are immunotoxic and teratogenic, which is concerning for catalysts embedded within covalent adaptable networks (CANs). Here, we identify Zr(acac) 4 and Zr(tmhd) 4 as catalysts to reprocess PU CANs more sustainably. Thermoset PU foams containing Zr-based catalysts exhibit characteristic stress relaxation times between 6 and 200 s, similar or faster than DBTDL. These catalysts are capable of reprocessing a PU foam for four or five cycles. Dynamic mechanical thermal analysis indicates that zirconium-based catalysts preserve glass transition temperature and crosslink density between cycles and are promising catalysts for bulk reprocessing of thermoset PUs. Here, a solvent-free reprocessing method was developed by co-milling the PU foam and the Zr catalyst. Ultimately, these reprocessing methods using Zr-based catalysts will impart greater sustainability and circularity to PU plastics.

Catalysts↗
DOE OSTI2021

The preparation and properties of polyurethane foams reinforced with bamboo fiber sources in China

Abstract Polyurethane (PU) foams reinforced with bamboo fiber sources in China, i.e. , bamboo fiber, bamboo α -cellulose fiber, and bamboo nanocellulose fiber, were prepared and their physico-mechanical properties were analyzed in this work. The bamboo fiber sources and PU foams were characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), Thermal gravimetric analysis (TGA) and universal compression testing. The results indicated that the hydroxyl groups on the fiber surfaces were enhanced by removing non-celluloses in the preparation of α -cellulose and nanocellulose. With the addition of small particle size α -cellulose and nanocellulose, the cell sizes of PU foams were reduced due to more nucleating agents being introduced. The FTIR spectra confirmed that the bamboo fiber sources were involved in the foaming reaction. The PU foams with bamboo fiber sources had a higher thermal stability than neat foam, and they were satisfactory enough to be used as insulation. PU foams reinforced with 5% bamboo fiber, 3% α -cellulose fiber and 3% nanocellulose fiber had better physico-mechanical performance than other foams. The reinforcement performance of 3% bamboo α -cellulose fiber on PU foam was comparable with that of high-cost nanocellulose. Accordingly, bamboo α -cellulose fiber was demonstrated to be a promising candidate to reinforce PU foam, which could be used in the reinforcement of foam insulation.

Qiu, Chongpeng↗
DOE OSTI2022

A Novel Process for Converting Coal to High-Value Polyurethane Products

Battelle has demonstrated a patented process for making high-value, polyurethane (PU) foam from coal, based on preparing liquefied coal via direct liquefaction, converting it to polyols as an intermediate via ozonation, and then making PU foams from these polyols. This process represents a breakthrough in innovative utilization of U.S. coals, and is applicable to bituminous as well as sub-bituminous coals. The resulting PU foam products are projected to have an extremely high value (i.e., over $\$5,000$ /ton), with nearly 100% of carbon utilization from coalderived liquid feedstock, and 31.5% to 43.5% of the carbon in the PU foam polyol product being bio-based. The targeted products represent an extremely large (i.e., over $80 billion/year), existing PU foam market, which could expand into making coatings and adhesives. The process can further help reduce petroleum imports, while improving the economics of PU foam production. This work was completed with funding from the National Energy Technology Laboratory (NETL), with cost share from the State of Ohio’s Ohio Development Services Agency (ODSA) and others, and has advanced the process to 10 kg/day continuous scale and thus to Technology Readiness Level (TRL) 5. A total of 48 coal-based polyols were prepared and evaluated. The initial 28 polyols focused on range finding for ideal conditions. The later 20 polyols were produced as part of process optimizations. These optimizations were targeted around a continuous ozonolysis process to evaluate extended time reactions and to create the necessary intermediate for production of 1-gallon samples of polyol. The most unique attribute of Battelle’s polyol is in the utilization of coal’s aromaticity to gain final foam rigidity. Typically, polyols depend on the isocyanate fraction and cross-linking to gain rigidity. By utilizing coal, we were able to maintain rigidity while reducing the overall hydroxyl value of the polyol. This is important as lower hydroxyl value leads to greater percent weight of the coal-based polyol because less isocyanate is required for foaming. This leads to greater foam cost savings. This report provides the details, process, and process cost models of the conversion of coal to polyols and further to PU foams. Battelle’s process begins with coal liquids. These liquids can be obtained by two processes: coal coking or pyrolysis to produce coal tar, and Battelle’s biobased coal-to-liquids (CTL) process to produce heavy syncrude after liquifying >85% coal. After liquification, Battelle utilizes ozonolysis to create functionalization on the polyaromatic coal structure. The functionalization is then converted to the final polyester polyol through transesterification, or to hydroxyamide polyol through amidification. Equivalent or better standard properties have been obtained for 2 lb/ft 3 density rigid, water and freon-alternative blown foams, including compressive strength, density, R-value, and dimensional stability. Target applications for these foams are insulation, packaging, and energy-absorbing foams. Some exploratory testing also showed promise for adhesives applications. A detailed economic analysis showed that Battelle’s polyol process is economical, at a 140 metric tons per day (MTD) polyol production scale. An attractive return on investment (ROI) at competitive pricing validates the process is ready for a pilot-plant demonstration. A scale-up plan is provided.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2024

Sum-of-Fractions Methodology for Actinides in Water- and Polyethylene-Moderated and -Reflected Systems

Sum-of-fractions is a method intended to make sure a subcritical margin for aqueous solutions and slurries of fissionable isotopes exists. The method indicates that a system is subcritical if the sum of the ratios of the mass of each isotope (in a mixture) to its individual minimum subcritical mass limit is less than or equal to one. Historically, the basis of the sum-of-fractions has been derived from allowances given in the American National Standards Institute (ANSI)/ American Nuclear Society (ANS)-8.15-1981. However, the allowance was removed in ANSI/ANS-8.15-2014 due to a lack of technical basis. A methodology was developed to assess the validity of using the sum-of-fractions for water- or polyethylene-moderated systems for the following nuclides: 232 U, 233 U, 234 U, 235 U, 237 Np, 236 Pu, 238 Pu, 239 Pu, 240 Pu, 241 Pu, 242 Pu, 241 Am, 242 m Am, 243 Am, 242 Cm, 243 Cm, 244 Cm, 245 Cm, 246 Cm, 247 Cm, 249 Cf, and 251 Cf. The methodology uses available benchmark data for mixtures of 233 U, 235 U, and 239 Pu to establish the calculational margin, and a mass limit reduction to establish the margin of subcriticality. Water- or polyethylene-moderated and -reflected mixtures containing the nuclides are evaluated with the code system, SCALE 6.2.4. Including the calculational margin, subcritical mass limits for each nuclide were computed for optimally water- or polyethylene-moderated and fully reflected systems. These masses were used to create nuclide mixtures in which the sum of the mass to subcritical mass limit ratios is one. The various nuclide mixtures were modeled over a range of moderation and demonstrate the keff does not exceed the calculational margin. For additional assurance of subcriticality, a significant mass reduction is applied to each computed minimum critical mass of the nuclides without adequate benchmark data consistent with the method in ANSI/ANS-8.15-2014.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2022

Origin of Plutonium-244 in the Early Solar System

We investigate the origin in the early Solar System of the short-lived radionuclide 244 Pu (with a half life of 80 Myr) produced by the rapid (r) neutron-capture process. We consider two large sets of r-process nucleosynthesis models and analyse if the origin of 244 Pu in the ESS is consistent with that of the other r and slow (s) neutron-capture process radioactive nuclei. Uncertainties on the r-process models come from both the nuclear physics input and the astrophysical site. The former strongly affects the ratios of isotopes of close mass ( 129 I/ 127 I, 244 Pu/ 238 U, and 247 Pu/ 235 U). The 129 I/ 247 Cm ratio, instead, which involves isotopes of a very different mass, is much more variable than those listed above and is more affected by the physics of the astrophysical site. We consider possible scenarios for the evolution of the abundances of these radioactive nuclei in the galactic interstellar medium and verify under which scenarios and conditions solutions can be found for the origin of 244 Pu that are consistent with the origin of the other isotopes. Solutions are generally found for all the possible different regimes controlled by the interval (δ) between additions from the source to the parcel of interstellar medium gas that ended up in the Solar System, relative to decay timescales. If r-process ejecta in interstellar medium are mixed within a relatively small area (leading to a long δ), we derive that the last event that explains the 129 I and 247 Cm abundances in the early Solar System can also account for the abundance of 244 Pu. Due to its longer half life, however, 244 Pu may have originated from a few events instead of one only. If r-process ejecta in interstellar medium are mixed within a relatively large area (leading to a short δ), we derive that the time elapsed from the formation of the molecular cloud to the formation of the Sun was 9-16 Myr.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Evaluation of the Sum-of-Fractions Methodology for Water and Polyethylene Moderated Systems

Sum-of-Fractions is a method intended to assure a subcritical margin for aqueous solutions and slurries of fissionable isotopes. The method indicates that a system is subcritical if the sum of the ratios of the mass of each isotope in a mixture to its individual minimum subcritical mass limit is less than or equal to one. The basis of the Sum-of Fractions has historically been derived from allowances given in ANSI/ANS-8.15-1981. However, the allowance was removed in ANSI/ANS-8.15-2014 due to a lack of technical basis. A methodology was developed to assess the validity of using the Sum-of-Fractions for water or polyethylene moderated systems for the following nuclides: 232 U, 233 U, 234 U, 235 U, 237 Np, 236 Pu, 238 Pu, 239 Pu, 240 Pu, 241 Pu, 242 Pu, 241 Am, 242 mAm, 243 Am, 242 Cm, 243 Cm, 244 Cm, 245 Cm, 246 Cm, 247 Cm, 249 Cf, and 251 Cf. The methodology uses available benchmark data for mixtures of 233 U, 235 U, and 239 Pu to establish the calculational margin, and a mass limit reduction to establish the margin of subcriticality. Water or polyethylene moderated and reflected mixtures containing the nuclides are evaluated with SCALE 6.2.4. Including the calculational margin, subcritical mass limits for each nuclide were computed for optimally water or polyethylene moderated and fully reflected systems. These masses were used to create nuclide mixtures in which the sum of the mass to subcritical mass limit ratios is one. The various nuclide mixtures were modeled over a range of moderation and demonstrate the k eff does not exceed the calculational margin. For additional assurance of subcriticality, a significant mass reduction is applied to each computed minimum critical mass of the nuclides without adequate benchmark data consistent with the method in ANSI/ANS-8.15-2014.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2024

Predicting Radiation-Induced Plutonium Redox Chemistry using Multi-scale Modeling Methods

Over the the last 70 years plutonium (Pu) has been integral in the development of several technologies that have changed the world, yet our fundamental understanding of its chemistry is still far from complete. This is a testament to this element’s unique and complex properties, such as its ability to coexist as multiple oxidation states in aqueous solution. Careful manipulation of plutonium oxidation states is essential in the study and utilization of its rich chemistry. To achieve this level of control, a comprehensive mechanistic understanding of radiation-induced plutonium redox chemistry is critical due to the unavoidable exposure of plutonium to ionizing radiation fields, both inherent and from in-process applications. For this reason, we have developed an experimentally evaluated multi-scale computer model for the prediction of gamma radiation-induced Pu(IV) redox chemistry in concentrated nitric acid solutions (1.0, 3.0, and 6.0 M). Under these acidic, aqueous solution conditions, cobalt-60 gamma irradiation afforded negligible net change in the steady-state oxidation state distribution of Pu(IV). Multi-scale calculations, which are in excellent agreement with experimental data, indicate that this observation is due to radiation-induced redox cycling between Pu(IV) and Pu(III), as achieved by the reduction of Pu(IV) by radiolytic nitrous acid and hydrogen peroxide, and the oxidation of Pu(III) by nitrate and hydroxyl radicals. These radiation-induced redox processes are augmented by plutonium’s inherent disproportionation reactions.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Materials Data on PuMn2 by Materials Project

PuMn2 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Pu is bonded in a 12-coordinate geometry to four equivalent Pu and twelve equivalent Mn atoms. All Pu–Pu bond lengths are 2.98 Å. All Pu–Mn bond lengths are 2.85 Å. Mn is bonded to six equivalent Pu and six equivalent Mn atoms to form a mixture of edge, face, and corner-sharing MnPu6Mn6 cuboctahedra. All Mn–Mn bond lengths are 2.43 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu3Ga by Materials Project

Pu3Ga is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Pu is bonded to eight equivalent Pu and four equivalent Ga atoms to form distorted PuPu8Ga4 cuboctahedra that share corners with twelve equivalent PuPu8Ga4 cuboctahedra, edges with eight equivalent GaPu12 cuboctahedra, edges with sixteen equivalent PuPu8Ga4 cuboctahedra, faces with four equivalent GaPu12 cuboctahedra, and faces with fourteen equivalent PuPu8Ga4 cuboctahedra. All Pu–Pu bond lengths are 2.92 Å. All Pu–Ga bond lengths are 2.92 Å. Ga is bonded to twelve equivalent Pu atoms to form GaPu12 cuboctahedra that share corners with twelve equivalent GaPu12 cuboctahedra, edges with twenty-four equivalent PuPu8Ga4 cuboctahedra, faces with six equivalent GaPu12 cuboctahedra, and faces with twelve equivalent PuPu8Ga4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuAl2 by Materials Project

PuAl2 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Pu is bonded in a 12-coordinate geometry to four equivalent Pu and twelve equivalent Al atoms. All Pu–Pu bond lengths are 3.26 Å. All Pu–Al bond lengths are 3.13 Å. Al is bonded to six equivalent Pu and six equivalent Al atoms to form a mixture of edge, face, and corner-sharing AlPu6Al6 cuboctahedra. All Al–Al bond lengths are 2.67 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuIn by Materials Project

PuIn is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Pu is bonded to four equivalent Pu and eight equivalent In atoms to form PuPu4In8 cuboctahedra that share corners with twelve equivalent PuPu4In8 cuboctahedra, edges with eight equivalent PuPu4In8 cuboctahedra, edges with sixteen equivalent InPu8In4 cuboctahedra, faces with eight equivalent InPu8In4 cuboctahedra, and faces with ten equivalent PuPu4In8 cuboctahedra. All Pu–Pu bond lengths are 3.22 Å. All Pu–In bond lengths are 3.36 Å. In is bonded to eight equivalent Pu and four equivalent In atoms to form InPu8In4 cuboctahedra that share corners with twelve equivalent InPu8In4 cuboctahedra, edges with eight equivalent InPu8In4 cuboctahedra, edges with sixteen equivalent PuPu4In8 cuboctahedra, faces with eight equivalent PuPu4In8 cuboctahedra, and faces with ten equivalent InPu8In4 cuboctahedra. All In–In bond lengths are 3.22 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuZn2 by Materials Project

PuZn2 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Pu is bonded in a 12-coordinate geometry to four equivalent Pu and twelve equivalent Zn atoms. All Pu–Pu bond lengths are 3.34 Å. All Pu–Zn bond lengths are 3.20 Å. Zn is bonded to six equivalent Pu and six equivalent Zn atoms to form a mixture of corner, edge, and face-sharing ZnPu6Zn6 cuboctahedra. All Zn–Zn bond lengths are 2.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu3Sn by Materials Project

Pu3Sn is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Pu is bonded to eight equivalent Pu and four equivalent Sn atoms to form distorted PuPu8Sn4 cuboctahedra that share corners with twelve equivalent PuPu8Sn4 cuboctahedra, edges with eight equivalent SnPu12 cuboctahedra, edges with sixteen equivalent PuPu8Sn4 cuboctahedra, faces with four equivalent SnPu12 cuboctahedra, and faces with fourteen equivalent PuPu8Sn4 cuboctahedra. All Pu–Pu bond lengths are 3.35 Å. All Pu–Sn bond lengths are 3.35 Å. Sn is bonded to twelve equivalent Pu atoms to form SnPu12 cuboctahedra that share corners with twelve equivalent SnPu12 cuboctahedra, edges with twenty-four equivalent PuPu8Sn4 cuboctahedra, faces with six equivalent SnPu12 cuboctahedra, and faces with twelve equivalent PuPu8Sn4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu3Ge by Materials Project

Pu3Ge is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Pu is bonded to eight equivalent Pu and four equivalent Ge atoms to form distorted PuPu8Ge4 cuboctahedra that share corners with twelve equivalent PuPu8Ge4 cuboctahedra, edges with eight equivalent GePu12 cuboctahedra, edges with sixteen equivalent PuPu8Ge4 cuboctahedra, faces with four equivalent GePu12 cuboctahedra, and faces with fourteen equivalent PuPu8Ge4 cuboctahedra. All Pu–Pu bond lengths are 3.25 Å. All Pu–Ge bond lengths are 3.25 Å. Ge is bonded to twelve equivalent Pu atoms to form GePu12 cuboctahedra that share corners with twelve equivalent GePu12 cuboctahedra, edges with twenty-four equivalent PuPu8Ge4 cuboctahedra, faces with six equivalent GePu12 cuboctahedra, and faces with twelve equivalent PuPu8Ge4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuCd11 by Materials Project

PuCd11 crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Pu is bonded in a 12-coordinate geometry to twenty Cd atoms. There are a spread of Pu–Cd bond distances ranging from 3.59–3.89 Å. There are five inequivalent Cd sites. In the first Cd site, Cd is bonded in a cuboctahedral geometry to twelve Cd atoms. All Cd–Cd bond lengths are 3.15 Å. In the second Cd site, Cd is bonded in a 6-coordinate geometry to three equivalent Pu and six Cd atoms. All Cd–Cd bond lengths are 2.95 Å. In the third Cd site, Cd is bonded in a distorted q6 geometry to two equivalent Pu and eight Cd atoms. There are two shorter (2.95 Å) and four longer (3.03 Å) Cd–Cd bond lengths. In the fourth Cd site, Cd is bonded in a 10-coordinate geometry to one Pu and nine Cd atoms. All Cd–Cd bond lengths are 3.15 Å. In the fifth Cd site, Cd is bonded in a 10-coordinate geometry to one Pu and nine Cd atoms. There are four shorter (3.03 Å) and four longer (3.15 Å) Cd–Cd bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2Zn17 by Materials Project

Pu2Zn17 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Pu is bonded in a 10-coordinate geometry to nineteen Zn atoms. There are a spread of Pu–Zn bond distances ranging from 3.09–3.47 Å. There are four inequivalent Zn sites. In the first Zn site, Zn is bonded to two equivalent Pu and ten Zn atoms to form a mixture of distorted edge, corner, and face-sharing ZnPu2Zn10 cuboctahedra. There are a spread of Zn–Zn bond distances ranging from 2.60–2.74 Å. In the second Zn site, Zn is bonded to two equivalent Pu and ten Zn atoms to form a mixture of distorted edge, corner, and face-sharing ZnPu2Zn10 cuboctahedra. There are a spread of Zn–Zn bond distances ranging from 2.71–3.03 Å. In the third Zn site, Zn is bonded to three equivalent Pu and nine Zn atoms to form a mixture of distorted edge, corner, and face-sharing ZnPu3Zn9 cuboctahedra. There are two shorter (2.55 Å) and one longer (2.87 Å) Zn–Zn bond lengths. In the fourth Zn site, Zn is bonded in a 2-coordinate geometry to one Pu and thirteen Zn atoms. The Zn–Zn bond length is 2.69 Å.

36 MATERIALS SCIENCE↗