PUREX PROCESS PERFORMANCE WITH SHORT-RESIDENCE CONTACTORS

Recovery and purification were satisfactory in miniatarepilot-plant tests of the Purex first cycle with the solvent residing four seconds in each extraction stage. Decontamination factors for both zirconium-- niobium and ruthenium were greater than 10,000 with negligible crosscontamination of uranium and plutonium. The effects of the following on decontamination and plutonium partitioning were determined: irradiation level of the fuel, operating temperature, solvent saturation, accumulated exposure of the solvent, nitrous acid, and ferrous sulfamate versus U(IV) as a reductant for Pu(IV). (auth

Neptunium behavior in solvent extraction of uranium at Savannah River Plant

The solvent extraction behavior of neptunium in the processing of irradiated natural uranium (Purex process) and irradiated enriched uranium (HM process) at Savannah River was studied in the laboratory. Conditions were demonstrated for extracting neptunium in the first solvent extraction contactor of each process, and two methods were developed for partitioning neptunium from uranium in the HM process. (auth

URANIUM(IV) NITRATE AS A REDUCING AGENT FOR PLUTONIUM(IV) IN THE PUREX PROCESS

Practical procedures were demonstrated for partitioning plutonium from uranium in the Purex process with hydrazine-stabilized uranium(IV) nitrate as the reducing reagent for plutonium. Typical partitioning results were 0.04--0.2% loss of plutonium to the uranium product and less than 1 wt% uranium in the plutonium product. With uranium(IV) nitrate as a replacement for ferrous sulfamate, most solids in wastes from the Parex process can be eliminated. No undue hazard is expected from the use of hydrazine as the stabilizing agent. (auth

Out-Life Characteristics of IM7/977-3 Composites

The capability to manufacture large structures leads to weight savings and reduced risk relative to joining smaller components. However, manufacture of increasingly large composite components is pushing the out-time limits of epoxy/ carbon fiber prepreg. IM7/977-3 is an autoclave processable prepreg material, commonly used in aerospace structures. The out-time limit is reported as 30 days by the manufacturer. The purpose of this work was to evaluate the material processability and composite properties of 977-3 resin and IM7/977-3 prepreg that had been aged at room temperature for up to 60 days. The effects of room temperature aging on the thermal and visco-elastic properties of the materials were investigated. Neat resin was evaluated by differential scanning calorimetry to characterize thermal properties and change in activation energy of cure. Neat resin was also evaluated by rheometry to characterize its processability in composite fabrication. IM7/977-3 prepreg was evaluated by dynamic mechanical analysis to characterize the curing behavior. Prepreg tack was also evaluated over 60 days. The overall test results suggested that IM7/977-3 was a robust material that offered quality laminates throughout this aging process when processed by autoclave

Nano-Particle Enhanced Polymer Materials for Space Flight Applications

Recent advances in materials technology both in polymer chemistry and nano-materials warrant development of enhanced structures for space flight applications. This work aims to develop spacecraft structures based on polymer matrix composites (PMCs) that utilize these advancements.. Multi-wall carbon nano-tubes (MWCNTs) are expected to increase mechanical performance, lower coefficient of thermal expansion (CTE), increase electrical conductivity (mitigate electrostatic charge), increase thermal conductivity, and reduce moisture absorption of the resultant space structures. In this work, blends of MWCNTs with PETI-330 were prepared and characterized. The nano-reinforced resins were then resin transfer molded (RTM) into composite panels using M55J carbon fabric and compared to baseline panels fabricated from a cyanate ester (RS-3) or a polyimide (PETI-330) resin containing no MWCNTs. In addition, methods of pre-loading the fabric with the MWCNTs were also investigated. The effects of the MWCNTs on the resin processing properties and on the composite end-use properties were also determined

Processing and characterization of high performance polyimide nanocomposites

The goal of this work was to achieve a homogeneous morphology of carbon nanotubes in a polyimide matrix, characterize the resulting nanocomposite properties, and understand structure-property relationships. Melt-mixing was used as an effective method for dispersing multiwall nanotubes and carbon nanofibers in a phenylethynyl terminated imide resin where aggregation occurred only in particle-saturated systems. Particle network formation within the nanocomposites was studied using rheology and impedance spectroscopy; results showed that the electrical percolation threshold occurred at a lower particle loading than the rheological percolation threshold, consistent with the oligomer size in comparison to the distance for electrical conductivity (~5 nm). Thermomechanical analysis showed that the addition of nanoparticles enhanced the polyimide storage modulus and thermal behavior indicated that the nanoparticles restricted polymer motion to higher temperatures. A study of the cure mechanism of the oligomer with and without nanoparticles showed that the nanoparticles reduced the activation energy required for cure initiation while increasing the obtainable extent of cure at various isothermal temperatures. The work presented in this dissertation shows that an easy, time effective processing method can be used to homogeneously disperse nanoparticles in an imide oligomer, and the resulting nanocomposites exhibit enhanced properties. A business plan is also presented that reflects the market potential of this technology.Ph.D.Committee Chair: Shofner, Meisha; Committee Member: Gerhardt, Rosario; Committee Member: Jayaraman, Sundaresan; Committee Member: Mintz, Eric; Committee Member: Thio, Yonatha

Characterization of Natural Gas Fired and Alternative Steel Reheat Technologies

A current market profile is developed for the following natural gas-fired and alternative steel reheat technologies: walking beam, pusher, batch, and induction. The entire natural gas reheat market currently is approximately 135 x 1012 Btu per year out of a total potential reheat market of 187 x 1012 Btu per year. Future steel industry structural and technological trends are examined for potential impacts on the natural gas reheat market. The most important impacts will result from future implementation of hot charging, direct rolling, and thin strip casting. R&D opportunities for improving the competitiveness of gas-fired reheat technologies are discussed, including research in combustion fundamentals and furnace design, development of improved sensors and controls, and distribution of information to industry users

Ferrous Metal Heat Treating a Comparison of Natural Gas and Alternative Technologies

Ferrous metal heat treating technologies are identified for the following categories: through heat treating and selective heat treating. Current market profiles are developed for the various ferrous metal heat treating technologies segmented by furnace type and process type. Preliminary findings show an estimated population of over 52,000 heat treating furnaces. Of these, approximately 55 percent are fossil fuel-fired batch technologies (mainly natural gas), 15 percent are fossil fuel-fired continuous technologies, and 30 percent are electric induction technologies. Significant R&D opportunities for improving the competitiveness of natural gas in the ferrous metal heat treating market are explored

URANIUM(IV) NITRATE AS A REDUCING AGENT FOR PLUTONIUM(IV) IN THE PUREX PROCESS

Practical procedures were demonstrated for partitioning plutonium from uranium in the Purex process with hydrazine-stabilized uranium(IV) nitrate as the reducing reagent for plutonium. Typical partitioning results were 0.04--0.2% loss of plutonium to the uranium product and less than 1 wt% uranium in the plutonium product. With uranium(IV) nitrate as a replacement for ferrous sulfamate, most solids in wastes from the Parex process can be eliminated. No undue hazard is expected from the use of hydrazine as the stabilizing agent. (auth