Solubility Evaluation for Yucca Mountain TSPA-SR

A systematic evaluation of radionuclide solubility has been conducted for the Yucca Mountain Project. The conventional thermodynamic approach was employed and geochemical model calculations were used to estimate radionuclide solubilities for the base case. The study uses the computer code EQ3/6 as the major geochemical modeling tool. The water composition and environmental conditions are based on the results of in-package chemistry and in-drift chemistry studies. Field observations, laboratory measurements, and thermodynamic and kinetic considerations are utilized to ensure the resulting solubilities are conservative. Fourteen radioelements have been studied (U, Np, Pu, Th, Am, Ac, Tc, I, C, Cs, Sr, Ra, Pa, and Pb) and their solubilities are presented as either functions of environmental conditions or statistical distributions. Alternative solubility models for Np and Pu were also developed. These alternative models are based on measurements of spent fuel dissolution experiments rather than conventional thermodynamic considerations. Comparison of the Np and Pu base case models with their alternative models suggests that they are needed in order to advance our understanding about the behaviors of Np and Pu during the process of spent fuel corrosion

Current status of the multinational Arabidopsis community

The multinational Arabidopsis research community is highly collaborative and over the past thirty years these activities have been documented by the Multinational Arabidopsis Steering Committee (MASC). Here, we (a) highlight recent research advances made with the reference plant Arabidopsis thaliana; (b) provide summaries from recent reports submitted by MASC subcommittees, projects and resources associated with MASC and from MASC country representatives; and (c) initiate a call for ideas and foci for the “fourth decadal roadmap,” which will advise and coordinate the global activities of the Arabidopsis research community

PV-Li-ion-micropump membrane systems for portable personal desalination

This research presents a technical simulation of theoretically portable desalination systems utilising low-energy and lightweight components that are either commercially available or currently in development. The commercially available components are small-scale flexible and portable photovoltaic (PV) modules, Li-ion battery-converter units, and high pressure low voltage brushless DC motor-powered micropumps. The theoretical and conventional small-scale desalination membranes are compared against each other: low-pressure reverse osmosis (RO), nanofilters, graphene, graphene oxide, and graphyne technology. The systems were designed with the identical PV-Li-ion specifications and simulation data to quantify the energy available to power the theoretical energy demand for desalinating a saline water at 30,000–40,000 ppm total dissolved solid (TDS) to reliably supply the minimum target of 3.5 L d−1 of freshwater for one theoretical year. The results demonstrate that modern portable commercially available PV-battery systems and new generations of energy-efficient membranes under development have the potential to enable users to sustainably procure daily drinking water needs from saline/contaminated water resources, with the system exhibiting a net reduction in weight than carrying water itself

Metal Sorption on Dolomite Surfaces

Potential human intrusion into the Waste Isolation Pilot Plant (WIPP) might release actinides into the Culebra Dolomite where sorption reactions will affect of radiotoxicity from the repository. Using a limited residence time reactor the authors have measured Ca, Mg, Nd adsorption/exchange as a function of ionic strength, P{sub CO{sub 2}}, and pH at 25 C. By the same approach, but using as input radioactive tracers, adsorption/exchange of Am, Pu, U, and Np on dolomite were measured as a function of ionic strength, P{sub CO{sub 2}}, and pH at 25 C. Metal adsorption is typically favored at high pH. Calcium and Mg adsorb in near-stoichiometric proportions except at high pH. Adsorption of Ca and Mg is diminished at high ionic strengths (e.g., 0.5M NaCl) pointing to association of Na{sup +} with the dolomite surface, and the possibility that Ca and Mg sorb as hydrated, outer-sphere complexes. Sulfate amplifies sorption of Ca and Mg, and possibly Nd as well. Exchange of Nd for surface Ca is favored at high pH, and when Ca levels are low. Exchange for Ca appears to control attachment of actinides to dolomite as well, and high levels of Ca{sup 2+} in solution will decrease Kds. At the same time, to the extent that high P{sub CO{sub 2}} increase Ca{sup 2+} levels, JK{sub d}s will decrease with CO{sub 2} levels as well, but only if sorbing actinide-carbonate complexes are not observed to form (Am-carbonate complexes appear to sorb; Pu-complexes might sorb as well; U-carbonate complexation leads to desorption). This indirect CO{sub 2} effect is observed primarily at, and above, neutral pH. High NaCl levels do not appear to affect to actinide K{sub d}s

Iodide retention by cinnabar (HgS) and chalcocite (Cu{sub 2}S)

Sorption of iodide (I{sup {minus}}) on cinnabar (HgS) and chalcocite (Cu{sub 2}S) was examined as a function of pH at 25{degrees}C in a series of batch experiments. Calculated distribution ratios (K{sub d}) far exceed those reported for other minerals; maximal K{sub d}`s of 1375 cc/g (Cu{sub 2}S) and 3080 c/g (HgS) were observed between pH 4-5, but wre substantial at all pH`s measured (4 < pH < 10). Iodide sorption apparently occurs by the formation of an insoluble surface solid solution with exposed Hg and Cu sites. Surface solid solution formation is favored at low pH due to the lessened electrostatic repulsion of the iodide ion by the sulfide surfaces

Phase chemistry of tank sludge residual components. 1998 annual progress report

'The proposed research will provide a scientific basis for predicting the long-term fate of radionuclides remaining with the sludge in decommissioned waste tanks. Nuclear activities in the United States and elsewhere produce substantial volumes of highly radioactive semi-liquid slurries that traditionally are stored in large underground tanks while final waste disposal strategies are established. Although most of this waste will eventually be reprocessed a contaminated structure will remain which must either be removed or decommissioned in place. To accrue the substantial savings associated with in-place disposal will require a performance assessment which, in turn, means predicting the leach behavior of the radionuclides associated with the residual sludges. The phase chemistry of these materials is poorly known so a credible source term cannot presently be formulated. Further, handling of actual radioactive sludges is exceedingly cumbersome and expensive. This proposal is directed at: (1) developing synthetic nonradioactive sludges that match wastes produced by the various fuel processing steps, (2) monitoring the changes in phase chemistry of these sludges as they age, and (3) relating the mobility of trace amounts of radionuclides (or surrogates) in the sludge to the phase changes in the aging wastes. This report summarizes work carried out during the first year of a three year project. A prerequisite to performing a meaningful study was to learn in considerable detail about the chemistry of waste streams produced by fuel reprocessing. At Hanford this is not a simple task since over the last five decades four different reprocessing schemes were used: the early BiPO{sup 4} separation for just Pu, the U recovery activity to further treat wastes left by the BiPO{sup 4} activities, the REDOX process and most recently, the PUREX processes. Savannah River fuel reprocessing started later and only PUREX wastes were generated. It is the working premise of this proposal that most of the phase chemistry in the wastes was defined when the acidic process fluids were first neutralized prior to storage. The only notable exception being that some silicates obviously formed later under highly caustic conditions. Waste stream chemistries for each process have been established and surrogate sludges prepared. Aging of these different recipes have begun at 25, 60, and 90 C and the phase chemistry of the different mixes is being monitored.

{sup 129}I{sup -} and {sup 99}TcO{sub 4}-scavengers for low level radioactive waste backfills

Minimization of {sup 129}I{sup -} and {sup 99}TcO{sub 4}{sup -} transport to the biosphere is critical to the success of low level radioactive waste (LLRW) storage facilities. Here we experimentally identify and classify optimal sorbent materials for inclusion in LLRW backfills. For low pH conditions (pH 4-5), Cu-sulfides and possibly imogolite-rich soils provide K{sub d}`s (surface-solution partition coefficients) of roughly 10{sup 3} ml g{sup -1} for iodide, and 10{sup 2} ml g{sup -1} for technetium. At near neutral pH, hydrotalcites, Cu-oxides, Cu-sulfides and lignite coal possess K{sub d}`s on the order of 10{sup 2} ml g{sup -1} for both iodine and technetium. At high pH (pH > 10), such as might occur in a cementitious LLRW facility, calcium monosulfate aluminate K{sub d}`s are calculated to be roughly 10{sup 2} ml g{sup -1} for both iodine and technetium

Industrial-scale microalgae pond primary dewatering chemistry for Energy-efficient autoflocculation

Industrial-scale microalgae production will likely require large energy-intensive technologies for both culture and biomass recovery; energy-efficient and cost-effective microalgae dewatering and water management are major challenges. Primary dewatering is typically achieved through flocculation followed by separation via settling or flotation. Flocculants are relatively expensive, and their presence can limit the reuse of de-oiled flocculated microalgae. Natural flocculation of microalgae—autoflocculation—occurs in response to changes in pH and water hardness and, if controlled, might lead to less-expensive “flocculant-free” dewatering. A better understanding of autoflocculation should also prompt higher yields by preventing unwanted autoflocculation. Autoflocculation is driven by double-layer coordination between microalgae, Ca+2 and Mg+2, and/or mineral surface precipitates of calcite, Mg(OH)2, and hydroxyapatite that form primarily at pH > 8. Combining surface complexation models that describe the interface of microalgae:water, calcite:water, Mg(OH)2:water, and hydroxyapatite:water allows optimal autoflocculation conditions—for example pH, Mg, Ca, and P levels—to be identified for a given culture medium

Factors associated with the severity of COVID-19 outcomes in people with neuromuscular diseases: Data from the International Neuromuscular COVID-19 Registry

BACKGROUND AND PURPOSE: Clinical outcome information on patients with neuromuscular diseases (NMDs) who have been infected with SARS-CoV-2 is limited. The aim of this study was to determine factors associated with the severity of COVID-19 outcomes in people with NMDs. METHODS: Cases of NMD, of any age, and confirmed/presumptive COVID-19, submitted to the International Neuromuscular COVID-19 Registry up to 31 December 2021, were included. A mutually exclusive ordinal COVID-19 severity scale was defined as follows: (1) no hospitalization; (2) hospitalization without oxygenation; (3) hospitalization with ventilation/oxygenation; and (4) death. Multivariable ordinal logistic regression analyses were used to estimate odds ratios (ORs) for severe outcome, adjusting for age, sex, race/ethnicity, NMD, comorbidities, baseline functional status (modified Rankin scale [mRS]), use of immunosuppressive/immunomodulatory medication, and pandemic calendar period. RESULTS: Of 315 patients from 13 countries (mean age 50.3 [±17.7] years, 154 [48.9%] female), 175 (55.5%) were not hospitalized, 27 (8.6%) were hospitalized without supplemental oxygen, 91 (28.9%) were hospitalized with ventilation/supplemental oxygen, and 22 (7%) died. Higher odds of severe COVID-19 outcomes were observed for: age ≥50 years (50-64 years: OR 2.4, 95% confidence interval [CI] 1.33-4.31; >64 years: OR 4.16, 95% CI 2.12-8.15; both vs. <50 years); non-White race/ethnicity (OR 1.81, 95% CI 1.07-3.06; vs. White); mRS moderately severe/severe disability (OR 3.02, 95% CI 1.6-5.69; vs. no/slight/moderate disability); history of respiratory dysfunction (OR 3.16, 95% CI 1.79-5.58); obesity (OR 2.24, 95% CI 1.18-4.25); ≥3 comorbidities (OR 3.2, 95% CI 1.76-5.83; vs. ≤2; if comorbidity count used instead of specific comorbidities); glucocorticoid treatment (OR 2.33, 95% CI 1.14-4.78); and Guillain-Barré syndrome (OR 3.1, 95% CI 1.35-7.13; vs. mitochondrial disease). CONCLUSIONS: Among people with NMDs, there is a differential risk of COVID-19 outcomes according to demographic and clinical characteristics. These findings could be used to develop tailored management strategies and evidence-based recommendations for NMD patients