Argonne National Laboratory Reports

The reliability of stainless steel type 304L canisters for the containment of solidified high-level radioactive wastes in the glass and calcine forms was studied. A reference system, drawn largely from information furnished by Battelle Northwest Laboratories and Atlantic Richfield Hanford Company is described. Operations include filling the canister with the appropriate waste form, interim storage at a reprocessing plant, shipment in water to a Retrievable Surface Storage Facility (RSSF), interim storage at the RSSF, and shipment to a final disposal facility

Chemical Engineering Division waste management programs. Quarterly report, January--March 1975

Development work on the study of consolidation techniques for Zircaloy fuel-cladding hulls included scouting tests on volatility schemes for separating the zirconium as the volatile tetrachloride and ignition tests on several Zircaloy materials to further characterize the pyrophoric behavior of Zircaloy. All tests were with nonirradiated metal pending acquisition of irradiated samples. Installation is nearly complete of a glovebox facility for studies on the salvage of alpha-contaminated metals by pyrochemical methods. Disposal of a major portion of fission product tritium formed in light water reactor fuels by deep- well injection of the low-level aqueous waste from plants reprocessing such fuels is being evaluated. The question of siting is a very important factor in determining the feasibility of this particular disposal option. A review is given of the status of information for U. S. sedimentary basins, the areas most likely to be generally suitable for siting of waste wells. Work on the reliability of high-level-waste canisters included an examination of creep, shot- peening, and subcooling of the filler canister below storage temperatures, as methods of relieving stresses induced in canisters due to differential contraction of canister and glass during cooling. A method was investigated for relieving stresses in calcine-filled canisters. Properties of fission product oxides were examined to elucidate possible adverse corrosive effects at the canister-waste interface. (LK

Sequential and Differential Interaction of Assembly Factors During Nitrogenase MoFe Protein Maturation

Nitrogenases reduce atmospheric nitrogen, yielding the basic inorganic molecule ammonia. The nitrogenase MoFe protein contains two cofactors, a [7Fe-9S-Mo-C-homocitrate] active-site species, designated FeMo-cofactor, and a [8Fe-7S] electron-transfer mediator called P-cluster. Both cofactors are essential for molybdenum-dependent nitrogenase catalysis in the nitrogen-fixing bacterium Azotobacter vinelandii. We show here that three proteins, NafH, NifW, and NifZ, copurify with MoFe protein produced by an A. vinelandii strain deficient in both FeMo-cofactor formation and P-cluster maturation. In contrast, two different proteins, NifY and NafY, copurified with MoFe protein deficient only in FeMo-cofactor formation. We refer to proteins associated with immature MoFe protein in the following as “assembly factors.” Copurifications of such assembly factors with MoFe protein produced in different genetic backgrounds revealed their sequential and differential interactions with MoFe protein during the maturation process. We found that these interactions occur in the order NafH, NifW, NifZ, and NafY/NifY. Interactions of NafH, NifW, and NifZ with immature forms of MoFe protein preceded completion of P-cluster maturation, whereas interaction of NafY/NifY preceded FeMo-cofactor insertion. Because each assembly factor could independently bind an immature form of MoFe protein, we propose that subpopulations of MoFe protein–assembly factor complexes represent MoFe protein captured at different stages of a sequential maturation process. This suggestion was supported by separate isolation of three such complexes, MoFe protein–NafY, MoFe protein–NifY, and MoFe protein–NifW. We conclude that factors involved in MoFe protein maturation sequentially bind and dissociate in a dynamic process involving several MoFe protein conformational states

Defining Electron Bifurcation in the Electron-Transferring Flavoprotein Family

Electron bifurcation is the coupling of exergonic and endergonic redox reactions to simultaneously generate (or utilize) low- and high-potential electrons. It is the third recognized form of energy conservation in biology and was recently described for select electron-transferring flavoproteins (Etfs). Etfs are flavin-containing heterodimers best known for donating electrons derived from fatty acid and amino acid oxidation to an electron transfer respiratory chain via Etf-quinone oxidoreductase. Canonical examples contain a flavin adenine dinucleotide (FAD) that is involved in electron transfer, as well as a non-redox-active AMP. However, Etfs demonstrated to bifurcate electrons contain a second FAD in place of the AMP. To expand our understanding of the functional variety and metabolic significance of Etfs and to identify amino acid sequence motifs that potentially enable electron bifurcation, we compiled 1,314 Etf protein sequences from genome sequence databases and subjected them to informatic and structural analyses. Etfs were identified in diverse archaea and bacteria, and they clustered into five distinct well-supported groups, based on their amino acid sequences. Gene neighborhood analyses indicated that these Etf group designations largely correspond to putative differences in functionality. Etfs with the demonstrated ability to bifurcate were found to form one group, suggesting that distinct conserved amino acid sequence motifs enable this capability. Indeed, structural modeling and sequence alignments revealed that identifying residues occur in the NADH- and FAD-binding regions of bifurcating Etfs. Collectively, a new classification scheme for Etf proteins that delineates putative bifurcating versus nonbifurcating members is presented and suggests that Etf-mediated bifurcation is associated with surprisingly diverse enzymes

Causes and evolution of winter polynyas north of Greenland

During the 42-year period (1979–2020) of satellite measurements, four major winter (December–March) polynyas have been observed north of Greenland: one in December 1986 and three in the last decade, i.e., February of 2011, 2017, and 2018. The 2018 polynya was unparalleled in its magnitude and duration compared to the three previous events. Given the apparent recent increase in the occurrence of these extreme events, this study aims to examine their evolution and causality, in terms of forced versus natural variability. The limited weather station and remotely sensed sea ice data are analyzed combining with output from the fully coupled Regional Arctic System Model (RASM), including one hindcast and two ensemble simulations. We found that neither the accompanying anomalous warm surface air intrusion nor the ocean below had an impact (i.e., no significant ice melting) on the evolution of the observed winter open-water episodes in the region. Instead, the extreme atmospheric wind forcing resulted in greater sea ice deformation and transport offshore, accounting for the majority of sea ice loss in all four polynyas. Our analysis suggests that strong southerly winds (i.e., northward wind with speeds greater than 10 m s−1) blowing persistently over the study region for at least 2 d or more were required over the study region to mechanically redistribute some of the thickest Arctic sea ice out of the region and thus to create open-water areas (i.e., a latent heat polynya). To assess the role of internal variability versus external forcing of such events, we carried out and examined results from the two RASM ensembles dynamically downscaled with output from the Community Earth System Model (CESM) Decadal Prediction Large Ensemble (DPLE) simulations. Out of 100 winters in each of the two ensembles (initialized 30 years apart: one in December 1985 and another in December 2015), 17 and 16 winter polynyas were produced north of Greenland, respectively. The frequency of polynya occurrence had no apparent sensitivity to the initial sea ice thickness in the study area pointing to internal variability of atmospheric forcing as a dominant cause of winter polynyas north of Greenland. We assert that dynamical downscaling using a high-resolution regional climate model offers a robust tool for process-level examination in space and time, synthesis with limited observations, and probabilistic forecasts of Arctic events, such as the ones being investigated here and elsewhere.</p

Structural Characterization of the P1+ Intermediate State of the P-Cluster of Nitrogenase

Nitrogenase is the enzyme that reduces atmospheric dinitrogen (N2) to ammonia (NH3) in biological systems. It catalyzes a series of single-electron transfers from the donor iron protein (Fe protein) to the molybdenum–iron protein (MoFe protein) that contains the iron–molybdenum cofactor (FeMo-co) sites where N2 is reduced to NH3. The P-cluster in the MoFe protein functions in nitrogenase catalysis as an intermediate electron carrier between the external electron donor, the Fe protein, and the FeMo-co sites of the MoFe protein. Previous work has revealed that the P-cluster undergoes redox-dependent structural changes and that the transition from the all-ferrous resting (PN) state to the two-electron oxidized P2+ state is accompanied by protein serine hydroxyl and backbone amide ligation to iron. In this work, the MoFe protein was poised at defined potentials with redox mediators in an electrochemical cell, and the three distinct structural states of the P-cluster (P2+, P1+, and PN) were characterized by X-ray crystallography and confirmed by computational analysis. These analyses revealed that the three oxidation states differ in coordination, implicating that the P1+ state retains the serine hydroxyl coordination but lacks the backbone amide coordination observed in the P2+ states. These results provide a complete picture of the redox-dependent ligand rearrangements of the three P-cluster redox states

Argonne National Laboratory Reports

Report of the Argonne National Laboratory Chemical Engineering Division on fuel-cycle studies including pyro-chemical separation of plutonium and americium oxides from contaminated materials of construction such as steel, advanced solvent extraction techniques in the development of centrifugal contactors for use in Purex processes, and a review and evaluation of the encapsulation of high-level waste in a metal matrix

Frontiers, Opportunities, and Challenges in Biochemical and Chemical Catalysis of CO_2 Fixation

Two major energy-related problems confront the world in the next 50 years. First, increased worldwide competition for gradually depleting fossil fuel reserves (derived from past photosynthesis) will lead to higher costs, both monetarily and politically. Second, atmospheric CO_2 levels are at their highest recorded level since records began. Further increases are predicted to produce large and uncontrollable impacts on the world climate. These projected impacts extend beyond climate to ocean acidification, because the ocean is a major sink for atmospheric CO2.1 Providing a future energy supply that is secure and CO_2-neutral will require switching to nonfossil energy sources such as wind, solar, nuclear, and geothermal energy and developing methods for transforming the energy produced by these new sources into forms that can be stored, transported, and used upon demand

Digital Signal Processing Research Program

Contains table of contents for Section 2, an introduction, reports on twenty-one research projects and a list of publications.U.S. Navy - Office of Naval Research Grant N00014-93-1-0686Lockheed Sanders, Inc. Contract P.O. BY5561U.S. Air Force - Office of Scientific Research Grant AFOSR 91-0034National Science Foundation Grant MIP 95-02885U.S. Navy - Office of Naval Research Grant N00014-95-1-0834MIT-WHOI Joint Graduate Program in Oceanographic EngineeringAT&T Laboratories Doctoral Support ProgramDefense Advanced Research Projects Agency/U.S. Navy - Office of Naval Research Grant N00014-89-J-1489Lockheed Sanders/U.S. Navy - Office of Naval Research Grant N00014-91-C-0125U.S. Navy - Office of Naval Research Grant N00014-89-J-1489National Science Foundation Grant MIP 95-02885Defense Advanced Research Projects Agency/U.S. Navy Contract DAAH04-95-1-0473U.S. Navy - Office of Naval Research Grant N00014-91-J-1628University of California/Scripps Institute of Oceanography Contract 1003-73-5