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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

MELCOR Deposition Models Applied to Noble Metals

Noble metals are chemically inert elements that form particles that can circulate around the fuel loop of a liquid-fueled molten salt reactor (LF-MSR). Due to their health-hazardous abilities, it is important to track these elements and to understand their contributions to source term during a reaction, particularly for Te as it decays into iodine. This report describes three solid deposition models that were implemented into the MELCOR reactor modeling code. The models that were implemented were Dittus-Boelter for turbulent fluid deposition, Talbot thermophoretic transport equation and Richardson-Zaki gravitational deposition. These closures were used to calculate the mass transfer coefficient and was compared to those reported for the Molten Salt Reactor Experiment (MSRE). The impacts of salt, operation and particle parameters on how they affect solid deposition are described, and found that solid deposition is strongly dependent on salt flow and viscosity, as well as particle diffusion rate and size. The conclusions form the basis for activities to be carried out in FY26 and for pursuit of future activities.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2020

Epsilon Metal: A Waste Form for Noble Metals from Used Nuclear Fuel

Epsilon metal (e-metal) is the metallic phase that forms as inclusions at the grain boundaries in the UO2 fuel during reactor operation. This metal is composed of Pd, Mo, Rh, Ru, and Tc. These metallic inclusions are insoluble in strong acid and remnants of these metallic inclusions have been found in the UO2 matrix that remains from the natural reactors in Gabon that were active 1.8 billion years ago, therefore e-metal should be an excellent waste form for the immobilization of the long-lived isotopes 107Pd (6.5 ? 106 a) and 99Tc (2.13 ? 105 a), with 99Tc being the isotope of interest for repository performance. Therefore, the chemical durability of this potential waste form is assessed in this study. Typically, corrosion rates for metallic materials are measured electrochemically because they are quick, inexpensive, and can reveal the mechanism by which a metal corrodes, at least initially. However, in a repository the waste form would be subjected to slowly flowing water without an applied electrical potential over long time periods. Therefore, the corrosion rates of e-metal specimens were measured with both electrochemical tests and the single-pass flow-through test (SPFT). Potentiodynamic and potentiostatic polarization results suggest that a thin passive film exists on the alloy surface, which seems to be responsible for its high corrosion resistance. Additionally, X-Ray photoelectron spectroscopic results suggest that Pd oxides are significantly enriched in the passive film Results from the SPFT show that the dissolution rates were weakly dependent on pH. Only Mo and Re were found in solution and were used for the calculation of the dissolution rates. In general, the electrochemically determined corrosion rates agree reasonably well with the initial dissolution rate measured with the SPFT test, but they are about one or two orders of magnitude higher than the steady state rates. The causes for this discrepancy are discussed.

epsilon-metal, nuclear waste form, corrosion, sing↗
DOE OSTI2019

NOBLE METAL MASS TRANSPORT MODEL FOR MOLTEN SALT REACTOR ANALYSIS IN VERA-CS

Molten Salt Reactor designs require robust multiphysics modelling capabilities to further the development of this next generation technology. Due to the unique liquid fuel design, traditional reactor physics analysis codes do not capture all of the important physics of these reactors. This work builds upon a general species transport model implemented into the multiphysics core simulator suite VERA-CS, by adding source and sink models for non-soluble fission products, specifically the noble metals. Noble metal fission products are born in the fuel-salt, but do not form stable fluorides, and instead plate out on various surfaces in the reactor fuel loop. A concentration gradient diffusion-convection based mass transfer model is implemented into the general species transport model within CTF-the subchannel thermal hydraulics code in VERA-CS-and verified. Two noble metal decay chains are analyzed, and their steady state bulk and surface concentrations are calculated for a simple flow loop in CTF that is representative of the Oak Ridge National Laboratory Molten Salt Reactor Experiment (MSRE). Non-soluble species 99Mo to 99Tc captures wall plate out of decaying species, and non-soluble 135Te to soluble 135I and gaseous 135Xe captures wall loss of decaying species. Results are compared with MSRE data and the possible multiphysics effects of this phenomena are identified. Future work to enhance the robustness of the physical model and couple it with neutronics to evaluate these effects of Noble Metal mass transport is discussed.

Walker, Samuel↗
NASA NTRS1993

Experimental partitioning of Zr, Ti, and Nb between silicate liquid and a complex noble metal alloy and the partitioning of Ti between perovskite and platinum metal

El Goresy et al.'s observation of Nb, Zr, and Ta in refractory platinum metal nuggets (RPMN's) from Ca-Al-rich inclusions (CAI's) in the Allende meteorite led them to propose that these lithophile elements alloyed in the metallic state with noble metals in the early solar nebula. However, Grossman pointed out that the thermodynamic stability of Zr in the oxide phase is vastly greater than metallic Zr at estimated solar nebula conditions. Jones and Burnett suggested this discrepancy may be explained by the very non-ideal behavior of some lithophile transition elements in noble metal solutions and/or intermetallic compounds. Subsequently, Fegley and Kornacki used thermodynamic data taken from the literature to predict the stability of several of these intermetallic compounds at estimated solar nebula conditions. Palme and Schmitt and Treiman et al. conducted experiments to quantify the partitioning behavior of certain lithophile elements between silicate liquid and Pt-metal. Although their results were somewhat variable, they did suggest that Zr partition coefficients were too small to explain the observed 'percent' levels in some RPMN's. Palme and Schmitt also observed large partition coefficients for Nb and Ta. No intermetallic phases were identified. Following the work of Treiman et al., Jurewicz and Jones performed experiments to examine Zr, Nb, and Ti partitioning near solar nebula conditions. Their results showed that Zr, Nb, and Ti all have an affinity for the platinum metal, with Nb and Ti having a very strong preference for the metal. The intermetallic phases (Zr,Fe)Pt3, (Nb,Fe)Pt3, and (Ti,Fe)Pt3 were identified. Curiously, although both experiments and calculations indicate that Ti should partition strongly into Pt-metal (possibly as TiPt3), no Ti has ever been observed in any RPMN's. Fegley and Kornacki also noticed this discrepancy and hypothesized that the Ti was stabilized in perovskite which is a common phase in Allende CAI's.

Jurewicz, Stephen R.↗
DOE OSTI2026

Influence of Surfactants on Noble Metal Liquid-Gas Interface Mass Transfer in Molten Salt Reactors

Noble metals, a group of insoluble fission products (FPs), can accumulate in molten salt reactors (MSRs) and influence system performance and safety through deposition. Upon generation in fission, noble metals are transported by circulating salt and may either deposit on structural surfaces or enter the circulating gas bubble interfaces. While sparging was primarily designed for xenon and krypton removal, the mass transfer of noble metals into bubble interfaces highlights a potential pathway for their transport and partial extraction. The properties of the liquid-gas interface therefore play an important role in noble metal deposition and removal behaviors. Observations from earlier studies suggest that noble metals accumulated at the bubble interface can act as surfactants, making the bubble interface partially immobile. This behavior reduces the mass transfer capacity of circulating bubbles and affects both the overall distribution of noble metals in the loop and their removal efficiency. To investigate the influence of surfactants on noble metal transport, deposition, and extraction behaviors in MSRs, a previously developed and validated species transport model incorporating noble metal interphase mass transfer was used to simulate these behaviors. Two designed cases were studied to predict the distribution of 132Te along the Molten Salt Reactor Experiment (MSRE) loop under different bubble interface conditions. The results show that the mass transfer coefficients at the liquid-gas interface, determined by bubble interface characteristics, significantly influence noble metal distribution within the reactor loop. These findings emphasize the importance of continuously introducing fresh circulating bubbles into the molten salt to improve the removal efficiency of insoluble FPs from the MSR primary loop.

MSR↗
DOE OSTI2018

Photoacoustic Generation with Surface Noble Metal Nanostructures

Thin layers of noble metal (Ag, Au) nanoparticles on the surface of optical fiber edge are studied from the viewpoint of photoacoustic fiber-optic generation. In this paper we present theoretical investigation of laser radiation absorbtion by the monolayer of noble metal nanoparticles deposited on the surface of the optical fiber edge. Different nanostructures on the edge of the optical fiber are proposed for effective photoacoustic generation based on lasers with wavelength of 405, 445, 450, 510–530 nm.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Modeling the Behavior of Noble Metals During HLW Vitrification in the DM1200 Melter

The noble metals ruthenium (Ru), rhodium (Rh), and palladium (Pd) are present to various extents in defense and commercial high-level nuclear waste streams. Usually, their concentrations are higher in commercial waste. Ru, Rh, and Pd are sparingly soluble in silicate glass melts and they therefore form separate metal, oxide, or other phases. These phases are generally denser than the glass melt and tend to sediment to the bottom of the melter, where they form a "sludge" layer. Since the sludge layer has a higher electrical conductivity than the molten glass, accumulation of sludge can ultimately lead to electrical disruption of the operation of the melter. In addition, the sludge reduces the melt volume, which also changes the operational characteristics of the melter. The noble metals sludge is a highly viscous mixture of melt and noble metal phases. The concentration of noble metals in the sludge may be 10 to 100 times higher than that in the drained glass.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Chemical and Isotopic Characterization of Noble Metal Phase from Commercial UO 2 Fuel

We report elemental and isotopic analysis for the noble metal fission product phase found in irradiated nuclear fuel. The noble metal phase was isolated from three commercial irradiated UO 2 fuels by chemically dissolving the UO 2 fuel matrix, leaving the noble metal phase as the undissolved residue. Macro amounts of this residue were dissolved using a KOH+KNO 3 fusion and then chemically separated into individual elements for analysis by mass spectrometry. Though the composition of this phase has been previously reported, this work is the most comprehensive chemical analysis of the isolated noble metal phase to date. We report both elemental and isotopic abundances of the five major components of the noble metal phase (Mo, Tc, Ru, Rh, Pd). Additionally, we report a sixth element present in high quantities in this phase, tellurium. Tellurium appears to be an integral component of noble metal particles.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Modulation of the Effective Metal-Support Interactions for the Selectivity of Ceria Supported Noble Metal Nanoclusters in Atmospheric CO 2 Hydrogenation

Ever-increasing attention is given to the sustainable utilization of CO 2 in the atmosphere out of environmental and economic considerations. The deep-going clarification of the effective and ineffective metal-support interactions (MSI) in the supported catalysts for the catalytic performance of CO 2 hydrogenation is particularly needed to design highly active nanocatalysts. How to tune the MSI to be effective for the selectivity of goal hydrogenation products is a significant but rather challenging subject. In this work, we demonstrate that the selectivity in CO 2 hydrogenation can be regulated from preferential CH 4 production to preferential CO production by varying the nature of the electronic MSI for ceria supported noble metal nanoclusters, and the effective MSI play a pivotal role for the catalytic systems with opposite hydrogenation selectivity. The modulation of the effective MSI for the selectivity in CO 2 hydrogenation sheds new light on the comprehensive understanding of the MSI and interfacial effects in terms of tailoring and controlling the performance of supported heterogeneous catalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Self-regenerative noble metal catalysts supported on high-entropy oxides

Discovery of anti-sintering noble metal catalysts is challenging, as supported noble metal species tend to aggregate at high temperatures, leading to severely deteriorated catalytic performances. Here we show that 1 wt% of noble metal species including Au, Pd and Ru can be incorporated into high-entropy oxides (HEOs) through entropy stabilization at 900 °C in air. A reversible temperature-dependent dissolution–exsolution process is observed for Au-HEO. Further correlation with distinct CO oxidation capabilities demonstrates the potential to utilize the entropy effect to access self-regenerative catalysts for catalytic reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1992

Noble metal abundances in an early Archean impact deposit

Detailed analyses are reported on the concentrations of the noble metals Pd, Os, Ir, Pt, and Au in an early Archean spherule bed (S4) of probably impact origin from the lower Fig Tree Group, Barberton Greenstone Belt, South Africa. Compared to other sedimentary deposits of known or suspected impact origin, some noble metals are present in exceptionally high concentrations. Noble metal abundances are fractionated relative to abundances in chondrites with ratios of Os/Ir, Pt/Ir, Pd/Ir, and Au/Ir at only 80, 80, 41, and 2 percent of these values on CI chondrites. Although an extraterrestrial source is favored for the noble metal enrichment, the most plausible cause of the fractionation is by regional hydrothermal/metasomatic alteration.

Kyte, Frank T.↗