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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Tc3Ge by Materials Project

Tc3Ge is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Tc+1.33- sites. In the first Tc+1.33- site, Tc+1.33- is bonded in a distorted body-centered cubic geometry to four equivalent Tc+1.33- and four equivalent Ge4+ atoms. All Tc–Tc bond lengths are 2.67 Å. All Tc–Ge bond lengths are 2.67 Å. In the second Tc+1.33- site, Tc+1.33- is bonded in a 8-coordinate geometry to eight equivalent Tc+1.33- and six equivalent Ge4+ atoms. All Tc–Ge bond lengths are 3.08 Å. Ge4+ is bonded in a distorted body-centered cubic geometry to fourteen Tc+1.33- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3Sn by Materials Project

Tc3Sn is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Tc+1.33- sites. In the first Tc+1.33- site, Tc+1.33- is bonded in a distorted body-centered cubic geometry to four equivalent Tc+1.33- and four equivalent Sn4+ atoms. All Tc–Tc bond lengths are 2.75 Å. All Tc–Sn bond lengths are 2.75 Å. In the second Tc+1.33- site, Tc+1.33- is bonded in a distorted body-centered cubic geometry to eight equivalent Tc+1.33- and six equivalent Sn4+ atoms. All Tc–Sn bond lengths are 3.17 Å. Sn4+ is bonded in a distorted body-centered cubic geometry to fourteen Tc+1.33- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Impact of Cr and Co on 99Tc retention in magnetite: A combined study of ab initio molecular dynamics and experiments

This work explores the effect of co-mingled dopants, Co(II) and Cr(III), on Tc(IV) incorporation and retention in magnetite when heat treated to 625 or 700 °C. Key trends in Tc retention in the high temperature regime were identified using a combination of density-functional-theory based ab initio molecular dynamics (AIMD) simulations, and batch experiments including solid phase characterization techniques, e.g. X-ray absorption spectroscopy. A stabilizing effect on Tc(IV) was observed when the number of Tc and Cr atoms are equal or when the magnetite surface is oversaturated with Tc and Cr inclusions. Here, oversaturation is hypothesized to force Cr from the magnetite surface to form a Cr2O3 phase, which may act as a protective layer that prevents Tc release. With the addition of Co, Tc(IV) is stabilized via redox processes. The presence of Cr in low concentrations interferes with this redox stabilization and Cr is preferentially stabilized as opposed to Tc. As a result, using Co as a stabilizing dopant for Tc may be compromised in the presence of Cr. When the relative concentration of Tc, Cr and Co is the same, or more Co atoms are added to high Cr incorporated systems, the formation of the Cr2O3 phase may be suppressed. Although waste streams with co-mingled Tc and Cr potentially may benefit from a Co dopant, since the formation of a Cr2O3 passivation layer may protect incorporated Tc from being released, the relative concentration of the three elements will be a critical parameter for maximizing effectiveness of this strategy.

Lee, Mal Soon↗
DOE OSTI2021

Tropical Cyclone Precipitation Response to Surface Warming in Aquaplanet Simulations With Uniform Thermal Forcing

While many modeling studies have attempted to estimate how tropical cyclone (TC) precipitation is impacted by climate change, the multitude of analysis techniques and methodologies have resulted in varying conclusions. Simplified models may be able to help overcome this problem. Radiative-convective equilibrium (RCE) model simulations have been used in various configurations to study fundamental aspects of Earth's climate. While many RCE modeling studies have focused on TC genesis, intensification, and size, limited work has been done using RCE to study TC precipitation. Here, in this study, the response of TC precipitation to sea surface temperature (SST) change is analyzed in global Community Atmosphere Model (CAM) aquaplanet simulations run with Radiative-Convective Equilibrium Model Intercomparison Project protocols, with the addition of planetary rotation. We expect that the insight gained about how TC precipitation responds to SST warming will help predict how TCs in the real world respond to climate change. In the CAM RCE simulations, the warmer SST simulations have less TCs on average, but the TCs tend to be larger in outer size and more intense. As simulation SST increases, more extreme precipitation rates occur within TCs, and more of the TC precipitation comes from these extreme rates. For extreme (99th percentile) TC precipitation, SST, and TC intensity increases dominate the 8.6% per K increase, while TC outer size changes have little impact. For accumulated TC precipitation, SST, and TC intensity contributions are still the majority, but TC outer size changes also contribute to the 6.6% per K increase.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Stronger Tropical Cyclone–Induced Ocean Cooling in Near-Coastal Regions Compared to the Open Ocean

Abstract Tropical cyclones (TC) often induce strong mixing in the upper ocean that generates a trail of cooler sea surface temperature (Twake) in their wakes. The Twake can affect TC intensity, so its prediction is important, especially in coastal regions where TCs can make landfall. Coastal Twakes are often more complex than those in the open ocean due to the influences of coastline geometry, highly variable water depth, continental runoff, and shelf processes. Using observational data since 2002, here we show a significantly stronger global mean Twake in coastal regions compared to offshore regions. Temperature stratification is the main driver of stronger coastal Twakes in the North Atlantic and east Pacific. In the northwest Pacific and north Indian Ocean, the differences between coastal and offshore Twakes are smaller due to compensation between TC forcings and ocean stratification. The north Indian Ocean is unique in the Northern Hemisphere because salinity stratification plays a major role on the spatial distribution of Twake. In the South Pacific Ocean, TC intensity and translation speed are crucial for explaining coastal–offshore Twake differences, while ocean stratification and mixed layer depth are more important for the coastal–offshore Twake differences in the south Indian Ocean. These findings suggest that coastal–offshore differences in ocean stratification need to be properly represented in models in order to capture changes in TC-induced ocean cooling as storms approach landfall. Significance Statement Landfalling tropical cyclones (TCs) often cause considerable damage in coastal regions with dense human populations. Understanding TC–ocean interaction and how it differs between coastal and offshore regions can help predict TC intensity prior to landfall. Sea surface cooling after TC passage is an important proxy for TC–ocean interaction. A global evaluation of coastal TC-induced cooling has not been conducted. Using data covering two decades, we show significantly stronger TC-induced surface cooling in coastal regions compared to offshore regions at the global scale and in all basins except the northwest Pacific and north Indian Ocean. The difference is driven mainly by upper-ocean conditions in the North Atlantic, east Pacific, and south Indian Ocean, and by TC characteristics in the South Pacific.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRSDate not supplied

A New ML-Based Adaptive Thinning Methodology to Improve the Impact of AIRS and CrIS Assimilation on Global Tropical Cyclone Forecasts

This work builds on previous research performed by this team to improve the forecast of Tropical Cyclones (TCs) by assimilating AIRS and CrIS radiances into the NASA Global Earth Observing System (GEOS). Past published work demonstrated that the assimilation of radiances with variable density was beneficial to TC forecasting in the GEOS. In the previous setup, a fixed-size moving square named 'TC domain' was activated by the so-called TC-vitals, an international real-time message accessible to all NWP forecasting centers, that documents the existence of a TC, its estimated position, and its size. The information from TC-vitals activated a switch in the GEOS, which allowed to reduce the distance used for thinning AIRS and CrIS data inside a 15 degrees by 15 degrees moving TC domain centered on the storm, so that more data were assimilated in the vicinity of the TC during its lifetime. The methodology produced improved TC analyses and led to better forecasts, particularly related to intensity, without damaging the global forecast skill. In the new version, the adaptive thinning methodology is based on a machine-learning technique. The technique searches for TCs and creates TC masks by using cloud-top temperatures from all geostationary satellites without the need for additional information. It is being trained against the International Best Track Archive for Climate Stewardship (IBTrACS) data base. Once a TC mask is created, a switch identical to the one used in the previous adaptive thinning method is activated, allowing the GEOS to ingest more data in the TC-shaped size-changing domain that follows the storm. As of today, the team has been able to successfully assimilate data inside the ML-detected TC domains. Future work includes an improved capability of reducing false alarm rates (i.e., cloud systems that are erroneously labeled as TCs).

Oreste Reale↗
DOE OSTI2021

AGR 5/6/7 Data Qualification Report for ATR Cycles 162B through 168A

This report provides the qualification status of experimental data for the Advanced Gas Reactor (AGR) 5/6/7 fuel irradiation. AGR-5/6/7 was conducted in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) in support of development and qualification of tri-structural isotropic (TRISO) low-enriched fuel for use in high temperature gas-cooled reactors. The objectives of the AGR-5/6/7 experiments are to: (i) irradiate reference-design fuel particles to support fuel qualification, (ii) establish operating margins for the fuel beyond normal operating conditions, and (iii) provide irradiated-fuel performance data and irradiated-fuel samples for post-irradiation examination (PIE) and safety testing. The test train contains five separate capsules that were independently controlled and monitored. Each capsule contains multiple 12.51-mm-long compacts filled with low enriched uranium carbide/oxide (UCO) TRISO fuel particles. The primary objective of the AGR-5/6 test (Capsules 1, 2, 4, and 5) is to verify successful performance of the reference-design fuel under normal operating conditions. The AGR-7 test (Capsule 3) was designed to explore fuel performance at higher temperatures to demonstrate the capability of the fuel to withstand conditions beyond normal operating conditions in support of plant design and licensing. AGR 5/6/7 will also provide irradiated-fuel performance data on fission-gas release from failed particles during irradiation. The AGR-5/6/7 capsules were irradiated in the ATR northeast flux trap location. The experiment began on February 16, 2018 and ended on July 22, 2020, spanning nine ATR cycles over two and a half years. Thus, the AGR-5/6/7 fuel compacts were irradiated for a total of 360.9 effective full power days. The AGR 5/6/7 experiment was able to remain in the reactor core during all three Powered Axial Locator Mechanism (PALM) cycles (163A, 165A, and 167A) without overheating its fuel compacts. This report includes irradiation monitoring data from nine ATR Cycles: 162B, 163A, 164A, 164B, 165A, 166A, 166B, 167A, and 168A, as stored in the Nuclear Data Management and Analysis System (NDMAS). During irradiation, data records consisted of instantaneous measurements recorded every minute and provided by text files automatically every 2 hours. The AGR 5/6/7 data streams addressed in this report include thermocouple (TC) temperatures, sweep gas data (flow rates [capsule inlet, outlet, and downstream at detector], pressure, and moisture content), and Fission Product Monitoring System (FPMS) data (release rates and release to birth rate ratios [R/Bs]) for each of the five capsules. A total of 94,989,908 TC temperature and sweep gas data records were received and processed by NDMAS for AGR 5/6/7 irradiation. Of these records, 41,593,387 (or 43.7% of the total) met data collection and accuracy requirements and are labeled as Qualified. A total of 57,746,693 TC temperature readings were captured from 54 installed TCs. Among them, 10,034,676 TC temperature records (only 17.4%) were Qualified and 47,701,371 TC temperatures (or 82.6%) are Failed due to 48 TC failures (63.5%) and due to missing values (19.1%). To assess performance of the operational TCs, analysis of daily correlations between TCs found no evidence of virtual junction failure for any TCs. Analyses on control charts of TC temperature differences revealed trending in TC readings for TC2, 4, 5, and 13 in Capsule 3, but there is no conclusive indication of TC drift failure that caused those trends. Therefore, TC control charts are not used to disqualify TC data, but only for users’ consideration. For sweep gas flow rates, a total of 31,519,747 gas flow records (84.4%) are Qualified for use for AGR-5/6/7 experiment; 5,723,468 gas flow records (15.4%) are Failed due mostly to missing values; and 74,641 high sweep gas flow rates (0.2 %) are Trend. A large number of Failed missing TC temperature and gas flow values were caused by an error in the data output script that outputted a ‘NULL’ value when values were unchanged. This problem was fixed during the outage of Cycle 166B, which led to a substantially decreased number of missing values during the last three cycles. Nonetheless, a large amount of non-missing data remained because of the high data acquisition frequency (1-minute) and still provided sufficient data to effectively monitor the experiment as designed. For FPMS data, NDMAS received and processed fission product release and R/B data for nine ATR cycles, when ATR core reached full power during AGR 5/6/7 irradiation. These data consist of 110,388 release rate records and 110,388 R/B records for the twelve radionuclides (Kr 85m, Kr 87, Kr 88, Kr 89, Kr 90, Xe 131m, Xe 133, Xe 135, Xe 135m, Xe 137, Xe 138, and Xe 139) for each of the five capsules. Equivalent numbers of uncertainty records associated the release rates and R/B values were provided. To date, qualification status of the FPMS data stored in the NDMAS dat

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Materials Data on Tc3P by Materials Project

Tc3P crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. there are three inequivalent Tc+1.67- sites. In the first Tc+1.67- site, Tc+1.67- is bonded in a 4-coordinate geometry to four equivalent P5+ atoms. There are three shorter (2.47 Å) and one longer (2.51 Å) Tc–P bond lengths. In the second Tc+1.67- site, Tc+1.67- is bonded in a distorted water-like geometry to two equivalent P5+ atoms. There are one shorter (2.53 Å) and one longer (2.56 Å) Tc–P bond lengths. In the third Tc+1.67- site, Tc+1.67- is bonded in a distorted bent 120 degrees geometry to two equivalent P5+ atoms. There are one shorter (2.34 Å) and one longer (2.35 Å) Tc–P bond lengths. P5+ is bonded in a 8-coordinate geometry to eight Tc+1.67- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np2Si4Tc3 by Materials Project

Np2Tc3Si4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Np+3.50+ is bonded in a 2-coordinate geometry to two equivalent Tc+2.33- and two equivalent Si atoms. There are one shorter (2.93 Å) and one longer (2.96 Å) Np–Tc bond lengths. There are one shorter (2.92 Å) and one longer (2.94 Å) Np–Si bond lengths. There are two inequivalent Tc+2.33- sites. In the first Tc+2.33- site, Tc+2.33- is bonded in a 7-coordinate geometry to two equivalent Np+3.50+ and five Si atoms. There are a spread of Tc–Si bond distances ranging from 2.44–2.50 Å. In the second Tc+2.33- site, Tc+2.33- is bonded in a 12-coordinate geometry to six Si atoms. There are four shorter (2.51 Å) and two longer (2.56 Å) Tc–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 6-coordinate geometry to two equivalent Np+3.50+ and four Tc+2.33- atoms. In the second Si site, Si is bonded in a 4-coordinate geometry to four Tc+2.33- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3H by Materials Project

Tc3H is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Tc+0.33- sites. In the first Tc+0.33- site, Tc+0.33- is bonded in a 8-coordinate geometry to four equivalent Tc+0.33- and four equivalent H1+ atoms. All Tc–Tc bond lengths are 2.56 Å. All Tc–H bond lengths are 2.56 Å. In the second Tc+0.33- site, Tc+0.33- is bonded in a body-centered cubic geometry to eight equivalent Tc+0.33- atoms. H1+ is bonded in a distorted body-centered cubic geometry to eight equivalent Tc+0.33- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaTc3 by Materials Project

NaTc3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Na1+ is bonded in a distorted body-centered cubic geometry to fourteen Tc+0.33- atoms. There are eight shorter (2.70 Å) and six longer (3.11 Å) Na–Tc bond lengths. There are two inequivalent Tc+0.33- sites. In the first Tc+0.33- site, Tc+0.33- is bonded to four equivalent Na1+ and four equivalent Tc+0.33- atoms to form a mixture of distorted face, edge, and corner-sharing TcNa4Tc4 tetrahedra. All Tc–Tc bond lengths are 2.70 Å. In the second Tc+0.33- site, Tc+0.33- is bonded in a 8-coordinate geometry to six equivalent Na1+ and eight equivalent Tc+0.33- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc7B3 by Materials Project

Tc7B3 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. there are three inequivalent Tc+1.29- sites. In the first Tc+1.29- site, Tc+1.29- is bonded in a distorted L-shaped geometry to two equivalent B3+ atoms. Both Tc–B bond lengths are 2.25 Å. In the second Tc+1.29- site, Tc+1.29- is bonded in a 3-coordinate geometry to three equivalent B3+ atoms. All Tc–B bond lengths are 2.22 Å. In the third Tc+1.29- site, Tc+1.29- is bonded in a 3-coordinate geometry to three equivalent B3+ atoms. There are one shorter (2.19 Å) and two longer (2.21 Å) Tc–B bond lengths. B3+ is bonded in a 6-coordinate geometry to six Tc+1.29- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3Mo by Materials Project

MoTc3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Mo5+ is bonded to twelve Tc+1.67- atoms to form MoTc12 cuboctahedra that share corners with four equivalent MoTc12 cuboctahedra, corners with eight equivalent TcTc8Mo4 cuboctahedra, edges with eight equivalent MoTc12 cuboctahedra, edges with sixteen equivalent TcTc8Mo4 cuboctahedra, faces with four equivalent MoTc12 cuboctahedra, and faces with fourteen TcTc8Mo4 cuboctahedra. All Mo–Tc bond lengths are 2.77 Å. There are two inequivalent Tc+1.67- sites. In the first Tc+1.67- site, Tc+1.67- is bonded to four equivalent Mo5+ and eight Tc+1.67- atoms to form TcTc8Mo4 cuboctahedra that share corners with twelve equivalent TcTc8Mo4 cuboctahedra, edges with eight equivalent MoTc12 cuboctahedra, edges with sixteen TcTc8Mo4 cuboctahedra, faces with four equivalent MoTc12 cuboctahedra, and faces with fourteen TcTc8Mo4 cuboctahedra. All Tc–Tc bond lengths are 2.77 Å. In the second Tc+1.67- site, Tc+1.67- is bonded to four equivalent Mo5+ and eight equivalent Tc+1.67- atoms to form TcTc8Mo4 cuboctahedra that share corners with four equivalent TcTc8Mo4 cuboctahedra, corners with eight equivalent MoTc12 cuboctahedra, edges with twenty-four TcTc8Mo4 cuboctahedra, faces with six equivalent MoTc12 cuboctahedra, and faces with twelve TcTc8Mo4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np2Tc3Ge4 by Materials Project

Np2Tc3Ge4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Np is bonded in a 10-coordinate geometry to two equivalent Tc and eight Ge atoms. There are one shorter (2.89 Å) and one longer (2.98 Å) Np–Tc bond lengths. There are a spread of Np–Ge bond distances ranging from 2.94–3.10 Å. There are two inequivalent Tc sites. In the first Tc site, Tc is bonded in a 7-coordinate geometry to two equivalent Np and five Ge atoms. There are a spread of Tc–Ge bond distances ranging from 2.49–2.60 Å. In the second Tc site, Tc is bonded to six Ge atoms to form distorted corner-sharing TcGe6 octahedra. The corner-sharing octahedral tilt angles are 22°. All Tc–Ge bond lengths are 2.55 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 8-coordinate geometry to four equivalent Np and four Tc atoms. In the second Ge site, Ge is bonded in a 10-coordinate geometry to four equivalent Np, four Tc, and two equivalent Ge atoms. Both Ge–Ge bond lengths are 2.86 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The Influence of African Easterly Waves on Atlantic Tropical Cyclone Tracks and Landfall in Large Ensembles

African easterly waves (AEWs) are an important precursor or “seed” for Atlantic tropical cyclones (TCs), with 60%–80% of major hurricanes observed to originate from AEWs. However, climate model simulations indicate that AEWs are not necessary to maintain annual Atlantic TC frequency. Furthermore, small ensembles suggest that AEWs may impact the spatial distribution and landfall of Atlantic TCs. Here, we investigated the influence of AEWs on the spatial distribution of Atlantic TC tracks and landfall using 50-member ensembles of TC-permitting regional model simulations for five hurricane seasons characterized by different levels of TC activity. The control simulations are seasonal hindcasts in which AEWs were prescribed through the eastern lateral boundary condition using reanalysis. In the experiments, we suppressed AEWs by applying a 2–10 day filter to the eastern lateral boundary condition. In response to AEW suppression, we discovered statistically significant increases in Atlantic TC frequency (10%–26%) and landfall (16%–44%), a westward shift in TC genesis location and tracks with increased landfall over the Caribbean Islands, southwestern Gulf Coast, and southeastern US coast, and increases in mid-tropospheric relative humidity in the main development region. In addition, we evaluated TC genesis mechanisms in the absence of AEWs and found evidence that the intertropical convergence zone (ITCZ) intensified and extended northward, resulting in ITCZ wave-breaking that shed vortices which served as TC seeds. By uncovering the connections between TC seed types and the likelihood of TC landfall, this research can provide Atlantic coastal and island communities with useful information to prepare for TC impacts.

African easterly waves↗
DOE OSTI2023

Analyzing Relationships between Tropical Cyclone Intensity and Rain Rate over the Ocean Using Numerical Simulations

In this study, the relationship between tropical cyclone (TC) intensity and rain rate over the ocean is investigated using a full-physics numerical model (WRF) and a physics-based TC rainfall model (TCR). TC intensity is found to be nearly linearly correlated with the average rain rate in the inner core [~0.97 (mm h –1 m –2 )/(m s –1 )], while the correlation is weak at outer radii. This difference is induced because TC intensity is significantly correlated with both the vertical velocity and specific humidity in the inner core but is not significantly correlated with the vertical velocity in the outer radii. Further investigation shows that the intensity–rain-rate relationship at the outer radii is influenced by the TC evolution stage. The rain rate for the outer radii is positively correlated with TC intensity for nondecaying TCs, while this correlation is reduced for decaying TCs due to systematic downdrafts in the outer radii. In the context of climate change, the sensitivity of the TC rain rate to sea surface temperature (SST) is found to be +9% per 1 K increase of SST, roughly the product of the sensitivity of TC intensity to SST (+3%) and the Clausius-Clapeyron scaling (+7%). Coupled with synthetic storms, evolution of the TC rain rate over the twenty-first century under the SSP5-8.5 scenario is projected by the TCR (calibrated with the WRF simulations). The annual increase rates of averaged TC rain rate are 0.17% and 0.20% for the inner core and outer radii, respectively, larger than the annual increase rate of TC intensity (0.046%) but comparable to that of cube of intensity (0.18%).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1997

Attachment of Free Filament Thermocouples for Temperature Measurements on CMC

Ceramic Matrix Composites (CMC) are being developed for use as enabling materials for advanced aeropropulsion engine and high speed civil transport applications. The characterization and testing of these advanced materials in hostile, high-temperature environments require accurate measurement of the material temperatures. Commonly used wire Thermo-Couples (TC) can not be attached to this ceramic based material via conventional spot-welding techniques. Attachment of wire TC's with commercially available ceramic cements fail to provide sufficient adhesion at high temperatures. While advanced thin film TC technology provides minimally intrusive surface temperature measurement and has good adhesion on the CMC, its fabrication requires sophisticated and expensive facilities and is very time consuming. In addition, the durability of lead wire attachments to both thin film TC's and the substrate materials requires further improvement. This paper presents a newly developed attachment technique for installation of free filament wire TC's with a unique convoluted design on ceramic based materials such as CMC's. Three CMC's (SiC/SiC CMC and alumina/alumina CMC) instrumented with type IC, R or S wire TC's were tested in a Mach 0.3 burner rig. The CMC temperatures measured from these wire TC's were compared to that from the facility pyrometer and thin film TC's. There was no sign of TC delamination even after several hours exposure to 1200 C. The test results proved that this new technique can successfully attach wire TC's on CMC's and provide temperature data in hostile environments. The sensor fabrication process is less expensive and requires very little time compared to that of the thin film TC's. The same installation technique/process can also be applied to attach lead wires for thin film sensor systems.

Lei, Jih-Fen↗
DOE OSTI2020

Zero Valent Iron for Reductive Removal of Technetium-99 from Aqueous Sulfate Solutions - 20347

This research investigates the reductive removal of technetium-99 ({sup 99}Tc) by zero valent iron (ZVI) from low activity waste (LAW) off-gas condensate simulant as a secondary treatment after recovery from vitrification planned at the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Due to its high volatility, only a fraction of Tc{sup (VII)} will be incorporated into glass waste forms. Volatilized Tc will be captured by an off-gas treatment system with current plans to recycle off-gas condensate back to the vitrification facility. The scheme with off-gas recycling will increase Tc loading in the glass waste, but will also increase the concentrations of sulfate, halides, and other problematic constituents impeding overall LAW processing and increasing volume of the glass product. This study focuses on Tc{sup (VII)} removal by ZVI as a feasible pathway to minimize off-gas condensate recycling, which may result in a reduction in the volumes of LAW waste to be immobilized and subsequent cost savings. ZVI is an established treatment agent for redox-active contaminants such as trichloroethylene, nitrate, arsenic, chromium, phenol, and others. It is a commercially available and cost-effective material. Our previous experiments showed that ZVI is very efficient for the reductive removal of {sup 99}Tc. In this work we studied ZVI oxidation under aerobic conditions at pH 7 with 0.1 M Na{sub 2}SO{sub 4} solution (ionic strength, IS, 0.3 M) in the presence and absence of {sup 99}Tc. The concentration of {sup 99}Tc and the changes in pH, dissolved oxygen (DO), and oxidation-reduction potential (ORP) of the simulated solutions were monitored over 8 days. The formation of iron oxide phases was probed by X-ray diffraction (XRD). Obtained results suggest that ZVI contact time with {sup 99}Tc containing solutions for 6 hours resulted in nearly complete removal of {sup 99}Tc from the aqueous phase. XRD analysis showed that the oxidation of ZVI is rapid with formation of magnetite (Fe{sub 3}O{sub 4}) with minor percentage of goethite and maghemite. This work is a part of a larger set of studies investigating the feasibility of {sup 99}Tc reductive removal from the LAW off-gas condensate. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗