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At least 163 records · Page 9
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Cloud Uniformity Measurements from NASA's 2nd Fundamental Ice Crystal Icing Test Part 1 (Water Content & PSD)

This paper presents water content and particle measurements from the second Fundamental Ice Crystal Icing Physics test conducted in the NASA Propulsion Systems Laboratory. The water content measurements came from the Science Engineering Associates Multi-Element Probe and the Isokinetic Probe whereas the Artium Technologies, Inc. Phase Doppler Interferometer and High Speed Imaging instruments measured the particle size distribution. Ice particle accretion due to the ingestion of ice-crystals is attributed to numerous jet engine powerloss events. The NASA PSL is an altitude jet-engine test facility which has recently added a capability to inject ice particles into the flow. This work focuses on characterizing the icing cloud by traversing the instruments across the test section at four different conditions where velocity and water content were varied. For this test, the nozzle patterns were selected to make a uniform cloud in the center 6-inch diameter of the test section. Radial trends for the ice and water content measurements are presented and the melt ratio is calculated at the measurement locations. Particle size distributions are also presented. The measured water content, melt ratio, and particle size decreased moving out radially. Measured water content trends show uniformity to within 19.2% for the center 6 inches of the cloud, as intended. In addition, the total water content increased at centerline with velocity, whereas the melt ratio decreased.

Ice-Crystal Icing↗
DOE OSTI2020

Designing Flexibility into the Authorized Radioactive Contents of the 9982 Shipping Package

The 9982 radioactive material shipping package, or the 9982, differs from the others by allowing a multitude of radionuclides instead of a single defined set. While allowing flexibility, this requires more justification on why these contents would be worthwhile and why they would not cause various safety hazards when shipped together. The latter was covered through mass limit calculations, and the potential uses for the package are shown through comparison with historical shipments. Here, the mass limits were already calculated[1] and used to show three example shipments are suitable for the 9982 as well. Plutonium stored in 3013 containers[2], training sources shipped in 9977 packages[3], and americium standards shipped in 9978 packages[4] were all analyzed. The mass of each radionuclide and the corresponding mass limit were used to first determine if the listed content could be shipped. If so, the maximum allowed mass of such contents is also calculated in order to see if the 200-gram fissile limit for the 9982 would be violated if additional material was packed. The sum-of-the-fractions method produces contents that do not violate the mass limits or exceed the 200-gram fissile limit. These sets also serve as realistic examples of what may be shipped in the 9982. Well-founded example contents will help the approval of the package by showing its compatibility with previously shipped material. Unfounded hypothetical contents would not show the usefulness of having a wide variety of allowed radionuclides. More contents may be developed in order to incorporate other radionuclides that were not present in these three examples. The light elements will also need to be evaluated due to their exclusion currently preventing some materials from being allowed in the 9982.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Data Acquisition System Selection and Calibration of Resistive Moisture Content Measurements for Large-Scale Field Studies in Cold Climate Residential Building Envelope Performance

The residential building stock built before the energy codes were enforced has several significant inefficiency problems in terms of insulation and air leakage. To decrease these inefficiencies, building retrofits are necessary. However, if the envelope is not appropriately designed, excessive accumulation of moisture content and thus mold formation and decay inside the envelope layers can be a vital problem. This risk becomes higher, especially in extreme climate conditions such as cold winters and hot and humid summers as in some northern regions of the U.S. Field studies are essential to test the long-term hygrothermal performance of building envelopes. Although in-situ temperature, RH, and heat flux measurements are straightforward, moisture content measurements are cumbersome. Mainly, because of the heterogeneous nature of the wood materials, deviations and nonuniformities within the materials are unavoidable. Resistance measurements are one of the oldest methods used to measure the moisture content of wood and other building materials. In large-scale studies, it is commonly preferred to use multi-purpose data acquisition systems (DAQ) and custom-made or prefabricated moisture pins to measure the electrical resistance (and thus moisture content) of critical building materials. These multi-purpose DAQ systems generally provide lower costs and offer more flexibility. However, these systems require calibration and fine-tuning to achieve accurate moisture content measurements. A large-scale, two-year-long field study was conducted in northern Minnesota to monitor the hygrothermal performance of residential retrofit wall systems in cold climates. Two base case walls and sixteen different wall treatments were tested. Moisture contents were measured at various layers in each wall treatment using 85 sets of moisture pins. This paper focuses on the overall approach, fabrication, and calibration methodology for the combination of custom-made moisture pins and a multi-purpose DAQ. The aim is to directly use the low-excitation multi-purpose DAQ without any extra voltage regulator. A half-bridge circuit is used to measure wood resistance with 4V excitation voltage and 100 kΩ and 500 kΩ reference resistors. The system is calibrated for four different materials: Douglas fir, lodgepole pine, western red cedar, and oriented strand board (OSB). Calibration experiments were done under controlled conditions in 50% and 65% RH test chambers. Resistance-based moisture content calibration curves are obtained for each species. Results show that higher reference resistors provided better calibration curves for lower excitation voltages.

Desjarlais, Andre Omer↗
DOE OSTI2024

Effects of uranium metal carbon content on hydriding kinetics and corrosion blister number/area at sub-ambient pressures

Carbon is a common impurity in uranium metal, resulting in a number of uranium–carbon inclusion phases that contribute to an increase in metal defect density as carbon content increases. It is widely held that uranium hydride corrosion preferentially nucleates at these defect sites, and that an increase in carbon content will therefore represents an increase in uranium hydride corrosion sites on the metal surface. We hydrided six uranium sources with differing carbon contents to explore whether this assumption holds in a sub-ambient (~ 0.1 atm hydrogen), sealed environment, and report the resulting reaction kinetics and uranium hydride blister benchmarking data. We find that carbon content is not strongly correlated with reaction kinetics terms or the resulting hydride blister number and area, but that there is a tight relationship between corrosion blister number/area and kinetics as is expected. Further, we find that there is a strong trend of decreasing variance in the blister number, blister area, and induction time as carbon content increases (higher carbon content results in more reproducible blister populations). Additionally, we find a narrow band of uranium metal consumption at the end of the parabolic phase of reaction progress (beginning of linear growth phase) of 0.098 ± 0.011 w/w%, a fact that may be useful in assaying hydrogen corrosion of uranium metal within sealed environments generally.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Water content of carbon dioxide at hydrate forming conditions

There is an interest to ensure sub-saturated water content in lines containing carbon dioxide in applications such as enhanced oil recovery and carbon sequestration, to reduce risks of hydrate blockage and corrosion. The water content of carbon dioxide at various temperatures and pressures has been measured in the past, but there is no consistent set of measurements that could be used for carbon dioxide storage and transportation design work. The solubility of water in a carbon dioxide rich gas phase at hydrate forming conditions was measured in this work. Pressures ranged from 12.06 to 29.30 bar along two isotherms, 1 °C and -7 °C, all within the gaseous carbon dioxide and hydrate stability zone. For the first time in these types of measurements, the solid phase was also characterized and confirmed to be carbon dioxide hydrate via X-ray computed tomography, simultaneous with water content measurements of the gas phase. Once carbon dioxide hydrate conversion had reached a maximum value (65% estimated by X-ray computed tomography), the equilibrium water content was measured. Prior to reaching this maximum carbon dioxide hydrate conversion, the water content in carbon dioxide was observed to decrease as liquid water converted to carbon dioxide hydrate. Furthermore, this slow conversion to hydrate, metastability of the hydrate phase, or unexpected phases may be responsible for the large discrepancy between prior data sets for similar carbon dioxide water content measurements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Effect of sulfur content in a sulfur-activated carbon composite on the electrochemical properties of a lithium/sulfur battery

Highlights: • The content of sulfur in activated carbon was controlled by solution process. • The sulfur electrode with low sulfur content shows the best performance. • The Li/S battery has capacity of 1360 mAh/g at 1 C and 702 mAh/g at 10 C. - Abstract: The content of sulfur in sulfur/activated carbon composite is controlled from 32.37 wt.% to 55.33 wt.% by a one-step solution-based process. When the sulfur content is limited to 41.21 wt.%, it can be loaded into the pores of an activated carbon matrix in a highly dispersed state. On the contrary, when the sulfur content is 55.33 wt.%, crystalline sulfur can be detected on the surface of the activated carbon matrix. The best electrochemical performance can be obtained for a sulfur electrode with the lowest sulfur content. The sulfur/activated carbon composite with 32.37 wt.% sulfur afforded the highest first discharge capacity of 1360 mAh g{sup −1} at 1 C rate and a large reversible capacity of 702 mAh g{sup −1} at 10 C (16.75 A/g)

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effects of error, chimera, bias, and GC content on the accuracy of amplicon sequencing

ABSTRACT Targeted amplicon sequencing is widely used in microbial ecology studies. However, sequencing artifacts and amplification biases are of great concern. To identify sources of these artifacts, a systematic analysis was performed using mock communities comprised of 16S rRNA genes from 33 bacterial strains. Our results indicated that while sequencing errors were generally isolated to low-abundance operational taxonomic units, chimeric sequences were a major source of artifacts. Singleton and doubleton sequences were primarily chimeras. Formation of chimeric sequences was significantly correlated with the GC content of the targeted sequences. Low-GC-content mock community members exhibited lower rates of chimeric sequence formation. GC content also had a large impact on sequence recovery. The quantitative capacity was notably limited, with substantial recovery variations and weak correlation between anticipated and observed strain abundances. The mock community strains with higher GC content had higher recovery rates than strains with lower GC content. Amplification bias was also observed due to the differences in primer affinity. A two-step PCR strategy reduced the number of chimeric sequences by half. In addition, comparative analyses based on the mock communities showed that several widely used sequence processing pipelines/methods, including DADA2, Deblur, UCLUST, UNOISE, and UPARSE, had different advantages and disadvantages in artifact removal and rare species detection. These results are important for improving sequencing quality and reliability and developing new algorithms to process targeted amplicon sequences. IMPORTANCE Amplicon sequencing of targeted genes is the predominant approach to estimate the membership and structure of microbial communities. However, accurate reconstruction of community composition is difficult due to sequencing errors, and other methodological biases and effective approaches to overcome these challenges are essential. Using a mock community of 33 phylogenetically diverse strains, this study evaluated the effect of GC content on sequencing results and tested different approaches to improve overall sequencing accuracy while characterizing the pros and cons of popular amplicon sequence data processing approaches. The sequencing results from this study can serve as a benchmarking data set for future algorithmic improvements. Furthermore, the new insights on sequencing error, chimera formation, and GC bias from this study will help enhance the quality of amplicon sequencing studies and support the development of new data analysis approaches.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Effect of Oxygen Content on Wear and Cutting Performance of AlCrON Coatings

In this work, AlCrON coatings with various oxygen contents were deposited by multi-arc-ion plating technology. The effects of oxygen content on the microstructure, mechanical properties, wear and cutting performance of AlCrON coatings were investigated. The result showed that the O contents in the AlCrON coatings increased from 0 to 8.8 wt.% by changing the O{sub 2}/N{sub 2} flow ratios during the deposition process. The AlCrON coatings mainly included fcc-CrN and fcc-AlN phases, and the Al{sub 2}O{sub 3} and Cr{sub 2}O{sub 3} were also confirmed by the XPS results. Addition of oxygen improved the adhesion strength of AlCrON coatings. The AlCrON coating with 4.0 wt.% oxygen content showed the low surface roughness, low friction coefficient and the minimum wear rate. Cutting results also showed that addition of oxygen improved the service life of AlCrON coatings under various cutting conditions. The service life of AlCrON coatings increased firstly and then decreased with increasing oxygen contents, and the AlCrON coating with 4.0 wt.% oxygen content had the maximum cutting length under various cutting conditions, which might be due to the decrease of surface roughness, increase of adhesion strength and hardness. The wear mechanism involved in cutting process included abrasive wear, adhesive wear and oxidation wear.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Effect of Ni content in Cu 1-x Ni x coating on microstructure evolution and mechanical properties of W/Mo joint via low-temperature diffusion bonding

The 93W and Mo1 refractory metals were bonded with different Cu 1- x Ni x coating interlayers of various Ni content using plasma-activated sintering at 700 °C. The effects of the Ni content in the Cu 1- x Ni x coating interlayer on the interfacial microstructure evolution and mechanical properties of the W/Mo joints were studied. The maximum average shear strength of the W/Mo joint was 316.5 MPa when the Ni content of the Cu 1- x Ni x coating interlayer was 25 %. When the Ni content of the Cu 1- x Ni x coating interlayer was below 50 %, the atomic diffusion at the W/Mo joint interface was adequate without the formation of intermetallic compounds, as demonstrated by the High Resolution Transmission Electron Microscope analyses of the joints. The presence of Ni in Cu 1- x Ni x promoted diffusion bonding at the interface, which contributed to the high mechanical properties of the W/Mo joint. With an increase in the Ni content of the Cu 1- x Ni x coating interlayer, the MoNi intermetallic compound (IMC) nucleated and grew at the Cu 1- x Ni x coating/Mo1 interface. When the Ni content of the Cu 1- x Ni x coating interlayer was above 50 %, the generation of a brittle MoNi IMC weakened the shear strength of the W/Mo joint dramatically.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Ni content on the microstructure and mechanical properties of weld metal with both-side submerged arc welding technique

Highlights: • This manuscript primarily studied the effects of Ni content on the K65 weld metals; • Increase Ni content could significantly improve the strength and low temperature impact toughness of the weld metal. • The beneficial effect of Ni is attributed to its positive effect on phase transformation. • GBF keeps K-S or N-W relations only with one austenite and the variants belong to the same bain group are two reasons. • The M/A islands are considered to be another reason for the reduced toughness. - Abstract: The effects of nickel (Ni) content on the mechanical properties and microstructure evolution in the weld metals of commercial K65 oil and gas pipeline steel were studied. Increase Ni content could significantly improve the strength and low temperature impact toughness (−40 °C and −60 °C) of the weld metal. The above influences of Ni were attributed to the formation of predominant acicular ferrite (AF), at the expense of grain boundary ferrite (GBF), ferrite side plates (FSP) and martensite/austenite (M/A) constituent in weld metal. EBSD results indicated that GBF keeps K-S or N-W relations only with the prior austensite grain that belongs to one side of the grain boundary and the variants belong to the same bain group which always forms low angle boundary. Moreover, the retained austenite as one part of M/A constituent was mainly found in the weld metal with lower Ni content. It indicated that the transformation process could be promoted more completely by the increase of Ni content. The mechanism of the toughness improvement brought by Ni increasing was ascribed to the relatively uniform transformation to final microstructure, which reduces the appearance of GBF and M/A constituents.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructure and texture evolution of duplex stainless steels with different molybdenum contents

Highlights: • The 3.05Mo steel has higher resistance to strain-induced transformation than the 0.28Mo steel. • The increased Mo content affects the grain growth of austenite and ferrite due to the effects of segregation and anchoring. • At high annealing temperatures, this Mo retarding effect is weakened. • The suppression of γ-fiber development in the ferrite texture is associated with the increased Mo content. • High amounts of Mo generate unfavorable conditions for the formation of CSL boundaries. - Abstract: The microstructure and texture evolution of duplex stainless steels with different molybdenum contents were studied. For this purpose, hot-rolled 2205 and 2304 samples were solution-annealed at 1100 °C for 1800 s and then cold-rolled to a 75% thickness reduction. This was followed by an isothermal annealing at 900 and 1100 °C for 180 s. The EBSD technique was used to determine the phase ratio, crystallographic texture, and microstructural characteristics. The hot-rolled steel had a work hardened microstructure and the samples submitted to intermediate annealing presented mainly deformation-free grains. Cold rolling resulted in a substantial reduction in the phase spacing with the formation of the strain-induced α′-martensite (SIM) from the metastable austenite. After annealing at 900 °C, the ferrite grains retained the elongated shape of the cold-rolled condition and the primary recrystallization progressed in the austenite phase. Increasing the Mo content increased the resistance to strain-induced martensitic transformation and inhibited the grain growth of austenite phase during annealing at 900 °C. Increasing annealing temperature to 1100 °C promoted the coarsening of both bcc and fcc structures with the formation of annealing twins in the austenitic grains. The recrystallization kinetics and subsequent grain growth occur earlier in ferrite than in austenite phase. Differences in Mo content did not significantly alter the evolution of austenite texture, whereas in the ferrite phase the increase in Mo content suppressed the γ-fiber development. Oriented nucleation was the predominant mechanism observed during the recrystallization of ferritic grains in the 2205 samples. The development of ∑19a boundaries was associated with the selected growth of {554}<225>{sub α} grains in the annealed 2304 samples. Annealing twins were associated with the formation of Σ3 boundaries after the heat treatments. Grain coarsening resulted in a larger fraction of the special boundaries in ferrite phase but inhibited the CSL formation in the austenite phase.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effects of Co contents on the microstructures and properties of the electrodeposited NiCo–Zr composite coatings

Highlights: • The novel NiCo–Zr coatings were prepared by electro-deposition. • Surface morphology, crystal structure, grain size and microstrain were examined. • Texture, residual stress and corrosion resistance were investigated. • Addition of Co increased the hardness and corrosion resistance of the coatings. - Abstract: In this study, the NiCo–Zr composite coatings were prepared from the electrolytes with different Co{sup 2+} concentrations by electrodeposition method. The effects of Co contents on the crystal structure, surface morphology, grain size, microstrain and residual stress were examined by X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDX) and atomic force microscope (AFM). The corrosion resistance of the composite coatings was also examined by the potentiodynamic polarization and electrochemical impedance (EIS) measurements. The results revealed that the crystal structures of the coatings were dependent on the Co contents and addition of Co content of 58 wt% resulted in the formation of hexagonal (hcp) Co. The increasing Co contents in the NiCo–Zr composite coatings resulted in the smoother and more compact surface, decreased the grain size and increased the microstrain. The micro-hardness and residual stress also increased with increasing Co contents. The addition of Co increased the corrosion resistance of the NiCo–Zr composite coatings compared with the Ni–Zr coating while the corrosion resistance of the NiCo–Zr composite coatings decreased as the Co contents increased.

36 MATERIALS SCIENCE↗
DOE OSTI2013

The composition, heating value and renewable share of the energy content of mixed municipal solid waste in Finland

Highlights: • New experimental data of mixed MSW properties in a Finnish case region. • The share of renewable energy of mixed MSW. • The results were compared with earlier international studies. • The average share of renewable energy was 30% and the average LHVar 19 MJ/kg. • Well operating source separation decreases the renewable energy content of MSW. - Abstract: For the estimation of greenhouse gas emissions from waste incineration it is essential to know the share of the renewable energy content of the combusted waste. The composition and heating value information is generally available, but the renewable energy share or heating values of different fractions of waste have rarely been determined. In this study, data from Finnish studies concerning the composition and energy content of mixed MSW were collected, new experimental data on the compositions, heating values and renewable share of energy were presented and the results were compared to the estimations concluded from earlier international studies. In the town of Lappeenranta in south-eastern Finland, the share of renewable energy ranged between 25% and 34% in the energy content tests implemented for two sample trucks. The heating values of the waste and fractions of plastic waste were high in the samples compared to the earlier studies in Finland. These high values were caused by good source separation and led to a low share of renewable energy content in the waste. The results showed that in mixed municipal solid waste the renewable share of the energy content can be significantly lower than the general assumptions (50–60%) when the source separation of organic waste, paper and cardboard is carried out successfully. The number of samples was however small for making extensive conclusions on the results concerning the heating values and renewable share of energy and additional research is needed for this purpose.

09 BIOMASS FUELS↗
DOE OSTI2014

Comparative experimental investigation on the actuation mechanisms of ionic polymer–metal composites with different backbones and water contents

Water-based ionic polymer–metal composites (IPMCs) exhibit complex deformation properties, especially when the water content changes. To explore the general actuation mechanisms, both Nafion and Flemion membranes are used as the polymer backbones. IPMC deformation includes three stages: fast anode deformation, relaxation deformation, and slow anode deformation, which is mainly dependent on the water content and the backbone. When the water content decreases from 21 to 14 wt. %, Nafion–IPMC exhibits a large negative relaxation deformation, zero deformation, a positive relaxation deformation, and a positive steady deformation without relaxation in sequence. Despite the slow anode deformation, Flemion–IPMC also shows a slight relaxation deformation, which disappears when the water content is less than 13 wt. %. The different water states are investigated at different water contents using nuclear magnetic resonance spectroscopy. The free water, which decreases rapidly at the beginning through evaporation, is proven to be critical for relaxation deformation. For the backbone, indirect evidence from the steady current response is correlated with the slow anode deformation of Flemion-IPMC. The latter is explained by the secondary dissociation of the weak acid group –COOH. Finally, we thoroughly explain not only the three deformations by swelling but also their evolvement with decreasing water content. A fitting model is also presented based on a multi-diffusion equation to reveal the deformation processes more clearly, the results from which are in good agreement with the experimental results.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Defects, strain relaxation, and compositional grading in high indium content InGaN epilayers grown by molecular beam epitaxy

We investigate the structural properties of a series of high alloy content InGaN epilayers grown by plasma-assisted molecular beam epitaxy, employing the deposition temperature as variable under invariant element fluxes. Using transmission electron microscopy methods, distinct strain relaxation modes were observed, depending on the indium content attained through temperature adjustment. At lower indium contents, strain relaxation by V-pit formation dominated, with concurrent formation of an indium-rich interfacial zone. With increasing indium content, this mechanism was gradually substituted by the introduction of a self-formed strained interfacial InGaN layer of lower indium content, as well as multiple intrinsic basal stacking faults and threading dislocations in the rest of the film. We show that this interfacial layer is not chemically abrupt and that major plastic strain relaxation through defect introduction commences upon reaching a critical indium concentration as a result of compositional pulling. Upon further increase of the indium content, this relaxation mode was again gradually succeeded by the increase in the density of misfit dislocations at the InGaN/GaN interface, leading eventually to the suppression of the strained InGaN layer and basal stacking faults.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Modeling the Moisture Content and Dry Matter Loss in Dynamic Woody Biomass Storage Piles with Variable Extraction

The urgent need to mitigate climate change has spurred significant interest in renewable energy sources. This paper explores the storage and processing of woody biomass for biofuel production, considering the dynamic nature of biomass piles in real-world scenarios. A model has been developed to analyze moisture content changes and dry matter loss in woody biomass stored in piles prior to processing, taking into account varying extraction methods and environmental conditions. Case studies that examine the effects of different unpiling methods (FIFO, LIFO, and homogeneous) on moisture content and dry matter loss under various feedstock arrival rates and weather conditions are presented. Results indicate that unpiling methods significantly impact moisture content, with LIFO typically resulting in higher moisture content due to the utilization of fresher feedstock. Dry matter loss increases with pile size and time, emphasizing the importance of accurate modeling for assessing carbon emissions and feedstock quality. Furthermore, the model highlights the importance of process loading order and extraction methods in biomass storage, suggesting potential cost benefits associated with decreased moisture content. The difference between different extraction methods could vary the moisture content in the feedstock reaching the biofuel process by as much as 37.6%, however dry matter loss varies minimally for realistic pile changes. Overall, this research contributes to a better understanding of biomass storage dynamics and informs sustainable biofuel production practices.

Niska, Janel↗
DOE OSTI2016

Scholarly Context Adrift: Three out of Four URI References Lead to Changed Content

Increasingly, scholarly articles contain URI references to “web at large” resources including project web sites, scholarly wikis, ontologies, online debates, presentations, blogs, and videos. Authors reference such resources to provide essential context for the research they report on. A reader who visits a web at large resource by following a URI reference in an article, some time after its publication, is led to believe that the resource’s content is representative of what the author originally referenced. However, due to the dynamic nature of the web, that may very well not be the case. We reuse a dataset from a previous study in which several authors of this paper were involved, and investigate to what extent the textual content of web at large resources referenced in a vast collection of Science, Technology, and Medicine (STM) articles published between 1997 and 2012 has remained stable since the publication of the referencing article. We do so in a two-step approach that relies on various well-established similarity measures to compare textual content. In a first step, we use 19 web archives to find snapshots of referenced web at large resources that have textual content that is representative of the state of the resource around the time of publication of the referencing paper. We find that representative snapshots exist for about 30% of all URI references. In a second step, we compare the textual content of representative snapshots with that of their live web counterparts. We find that for over 75% of references the content has drifted away from what it was when referenced. These results raise significant concerns regarding the long term integrity of the web-based scholarly record and call for the deployment of techniques to combat these problems.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗
DOE OSTI2013

Functional Bounding Content Envelope for Gamma and Neutron Emitting Isotopes in the Model 9977 Packaging

The contents approved for shipment in a Type B radioactive material transportation package have historically been descriptions of discrete items, or groupings of well-defined similar items, in the package safety basis documentation. The need for a comprehensive functional content envelope of both gamma and neutron emitting nuclides compliant with regulatory limits has become necessary as the DOE complex requires shipments of unique mixtures of radionuclides and impurities. Recent publications have presented a calculational model and a corresponding content envelope intended to be compliant with federal regulatory external radiation limits as well as design decay heat limits based on the Model 9977 Packaging. The methodology used to develop this content envelope consisted of determining the external radiation dose rates based on one gram of a given isotope combined, in the case of actinides, with various levels of light element impurities and determining the allowable mass to the regulatory limits based on these dose rates. The method of ratioing from these calculations to the masses that meet the regulatory limits fails in the case of some combinations of actinides and light element impurities because of the effect of subcritical multiplication, resulting in non-conservative and non-compliant dose rates in some cases. This is particularly true for many actinides combined with beryllium, boron, fluorine, lithium, and sodium. In this study, the source was modeled as a sphere with the appropriate dimensions based on the actinide or gamma source density and placed at the bottom of the containment vessel for maximum conservatism. The results presented in this report rectify the above-noted deficiencies by adjusting the previously determined mass limits so that the resulting dose rates are compliant with regulatory limits. Some amount of iteration was required in some instances to adjust the masses for dose compliance. In some instances the masses were increased since they were too conservative. In addition, the method of ratioing the masses when applied to several gamma emitting isotopes also resulted in either non-conservative or overly conservative data. The mass imits presented here are for bare sources and are complaint with the design decay heat limit of 19W. The masses are based on package surface dose rates (the limiting dose rate) that fall in the range 185-195 mrem/h, thus giving an additional margin of between 7.5% and 2.5% to the regulatory limit of 200 mrem/h. This report presents a revised set of mass limits (i.e., content envelope) for several neutron emitting actinides with varying levels of light element impurities compliant with both external radiation and design decay heat limits. In addition, revised limits for gamma sources are also presented. The neutron emitter mass limits are in Tables 1 through 9 and the gamma emitter mass limits are in Table 10. The revised content envelope covering a wide range of materials present in the DOE complex, was developed for the Model 9977 Packaging, providing conservative limits for other commonly-used Type B Packagings such as the Models 9975 and 9978. It should be noted that for the Model 9977 package, shipment is also possible with three shielded containers – lead or tungsten for gamma sources and polyethylene for neutron emitters. The design decay heat limits for these are as follows: 19W for tungsten, 6W for lead and 3W for polyethylene. The limits presented in this report would need to be checked against the lower decay heat limits for the lead and polyethylene and adjusted as required for compliance. Criticality safety is not factored into these limits and should be evaluated on a case by case basis.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗