[en] Highlights: • A duplex brass (Cu_6_0Zn_4_0) was developed by additions of Si. • Phase fractions in the microstructure were changed and β phase was increased. • Microstructural changes were discussed by electron to atom ratio. • Dilatometric showed that Si increased the ordering temperature of β to β′. • The developed lead-free brass alloy can find application in machining. - Abstract: Effects of small additions of Si to Cu_6_0Zn_4_0 on the properties, microstructure and phase transformation were investigated. It was found that Si promotes the formation of β′ phase and the microstructure of the alloys was changed from duplex α + β′ to single phase β′ brass. Electron to atom ratio was calculated and it was concluded that increment in this ratio led to a decrease in stacking fault energy which had an important role in reduction of the grain size as well microstructural variations in this study. The dilatomeric analysis showed that Si increased the ordering temperature of Cu_6_0Zn_4_0 alloy. Finally, based on the properties, the Cu–Zn_4_0–Si alloys are predicted to have the potential of being an alternative for free cutting leaded brass

[en] A NO_x minimization strategy for coal-burning wall-fired and cyclone boilers was developed that included deep air staging, innovative oxygen use, reburning, and advanced combustion control enhancements. Computational fluid dynamics modeling was applied to refine and select the best arrangements. Pilot-scale tests were conducted by firing an eastern high-volatile bituminous Pittsburgh No.8 coal at 5 million Btu/hr in a facility that was set up with two-level overfire air (OFA) ports. In the wall-fired mode, pulverized coal was burned in a geometrically scaled down version of the B and W DRB-4Z(reg sign) low-NO_x burner. At a fixed overall excess air level of 17%, NO_x emissions with single-level OFA ports were around 0.32 lb/million Btu at 0.80 burner stoichiometry. Two-level OFA operation lowered the NO_x levels to 0.25 lb/million Btu. Oxygen enrichment in the staged burner reduced the NO_x values to 0.21 lb/million Btu. Oxygen enrichment plus reburning and 2-level OFA operation further curbed the NO_x emissions to 0.19 lb/million Btu or by 41% from conventional air-staged operation with single-level OFA ports. In the cyclone firing arrangement, oxygen enrichment of the cyclone combustor enabled high-temperature and deeply staged operation while maintaining good slag tapping. Firing the Pittsburgh No.8 coal in the optimum arrangement generated 112 ppmv NO_x (0.15 lb/million Btu) and 59 ppmv CO. The optimum emissions results represent 88% NO_x reduction from the uncontrolled operation. Levelized costs for additional NO_x removal by various in-furnace control methods in reference wall-fired or cyclone-fired units already equipped with single-level OFA ports were estimated and compared with figures for SCR systems achieving 0.1 lb NO_x/10⁶ Btu. Two-level OFA ports could offer the most economical approach for moderate NO_x control, especially for smaller units. O₂ enrichment in combination with 2-level OFA was not cost effective for wall-firing. For cyclone units, NO_x removal by two-level OFA plus O₂ enrichment but without coal reburning was economically attractive.

[en] This work studies the behavior of the internal structures of a pressurized water reactor and analyzes the three-dimensional phenomena of fluid-structure interaction during the first phase of a depressurization accident. The calculation gives the displacements and pressures at each point of the vessel, as well as the reaction forces on the core shroud. This calculation is carried out by the Plexus code, which uses the finite element method to solve a system of thermal-hydraulic equations, taking account of thermodynamic imbalance. HDR (superheated steam reactor) test results were used to validate the Plexus code. (author)

[en] Coal-fired electric utilities are facing a serious challenge with regards to curbing their NO(sub x) emissions. At issue are the NO(sub x) contributions to the acid rain, ground level ozone, and particulate matter formation. Substantial NO(sub x) control requirements could be imposed under the proposed Ozone Transport Rule, National Ambient Air Quality Standards, and New Source Performance Standards. McDermott Technology, Inc. (MTI), Babcock and Wilcox (B and W), and Fuel Tech are teaming to provide an integrated solution for NO(sub x) control. The system will be comprised of an ultra low-NO(sub x) pulverized coal (PC) burner technology plus a urea-based, selective non-catalytic reduction (SNCR) system. This system will be capable of meeting a target emission limit of 0.15 lb NO(sub x)/10(sup 6) Btu and target ammonia (NH3) slip level targeted below 5 ppmV for commercial units. Our approach combines the best available combustion and post-combustion NO(sub x) control technologies. More specifically, B and W's DRB-4Z TM ultra low-NO(sub x) PC burner technology will be combined with Fuel Tech's NO(sub x)OUT (SNCR) and NO(sub x)OUT Cascade (SNCR/SCR hybrid) systems and jointly evaluated and optimized in a state-of-the-art test facility at MTI. Although the NO(sub x)OUT Cascade (SNCR/SCR hybrid) system will not be tested directly in this program, its potential application for situations that require greater NO(sub x) reductions will be inferred from other measurements (i.e., SNCR NO(sub x) removal efficiency plus projected NO(sub x) reduction by the catalyst based on controlled ammonia slip). Our analysis shows that the integrated ultra low-NO(sub x) burner and SNCR system has the lowest cost when the burner emissions are 0.25 lb NO(sub x)/10(sup 6) Btu or less. At burner NO(sub x) emission level of 0.20 lb NO(sub x)/10(sup 6) Btu, the levelized cost per ton of NO(sub x) removed is 52% lower than the SCR cost

[en] The objective of this project is to develop an environmentally acceptable and cost-effective NO(sub x) control system that can achieve less than 0.15 lb NO(sub x)/10(sup 6) Btu for a wide range of coal-burning commercial boilers. The system will be comprised of an ultra low-NO(sub x) PC burner technology plus a urea-based, selective non-catalytic reduction (SNCR) system. In addition to the above stated NO(sub x) limit of 0.15 lb NO(sub x)/10(sup 6) Btu, ammonia (NH(sub 3)) slip levels will be targeted below 5 ppmV for commercial units. Testing will be performed in the 100 million Btu/hr Clean Environment Development Facility (CEDF) in Alliance, Ohio. Finally, by amendment action, a limited mercury measurement campaign was conducted to determine if the partitioning and speciation of mercury in the flue gas from a Powder River Basin coal is affected by the addition of Chlorides to the combustion zone

[en] This paper proposes a core design of fast reactor using mixed nitride fuel [(U,Pu)N], having small loss of reactivity and reaching a maximum thermal burn-up rate from 150 GWd/t, while being managed in single batch (renewal of the fuel in only one time for all the subassemblies of the core). This work was completed with aid of the studies of sensibilities of the fast reactors cores to principal parameters: general design of the core, volumetric percentages of the various mixture of materials composing the core, initial enrichments of the fuel. A detailed optimization study on the selected core was conducted complying with safety criteria taking into consideration of consequences of nitride material presence on fuel assembly design rules. (author)

[en] This thesis reports on a study of the Ising spin glass in two dimensions. Since the critical temperature for this system in known to be zero, only ground-state calculations are considered. Ground states for the Ising spin glass in two dimensions can be determined in polynomial time by a recently proposed mapping to an auxiliary graph decorated with Kasteleyn cities, as long as periodic boundary conditions are applied at most in one direction. Using this method, ground states for systems with open-periodic boundary conditions for lattices of linear sizes up to L = 10000 have been determined, and defect energies as well as domain-wall lengths have been calculated. A new algorithm based on a combination of the matching approach and a windowing technique is proposed, and quasi-exact ground-states for lattices with periodic-periodic boundary conditions up to L = 3000 are determined. The run-time of this windowing algorithm is also polynomial. By using these techniques, high-precision estimates of the spin-stiffness exponent and the domain-wall fractal dimension for Gaussian couplings have been achieved. The 2D Ising spin glass with bimodal couplings has a multitude of degenerate ground states, with the number of degenerate states growing exponentially with increasing system size. It is hence necessary to develop techniques for sampling the ground-state manifold uniformly. A new efficient algorithm serving this purpose is presented. The algorithm is based on an exact analysis of clusters of free spins in a disorder configuration and a subsequent sampling step based on parallel tempering Monte Carlo. Using this algorithm together with the mapping approach, high-precision estimates of the spin-stiffness exponent and the domain-wall fractal dimension for bimodal couplings are obtained. The estimates of the spin-stiffness exponent and the domain-wall fractal dimension for both Gaussian and bimodal couplings are the most accurate estimates which have been reported to date. The geometry of the domain walls of both Gaussian and bimodal couplings is compared to the detailed predictions given for random curves in the plane in the framework of Schramm-Loewner Evolution (SLE). Different boundary conditions are considered, and for each case the fractal dimension and the SLE diffusion constant of the corresponding Brownian motion are calculated. Correlations between different domain-wall segments are explicitly checked by testing for independence of the increments of the Loewner driving function.

[en] The sustainability of groundwater resources for drinking water supplies, agriculture, and industry is a prime concern in countries dominated by arid and semi-arid climates such as Morocco. The growing demand for groundwater coupled with impacts from land use and climate change make sustainability an even more important water management goal. In order to make sound decisions about water use and protection of water quality, water managers and policy makers must have a sound understanding of such factors as the location and amount of groundwater recharge and groundwater ages. Isotope methods have the added values of providing critical and rapid cost-effective ways to make sound decisions that standard hydrological or geochemical methods cannot provide. For many years, the National Water Authority and the National Centre for Nuclear Energy, Sciences and Technology (CNESTEN), with IAEA assistance, have worked together to characterize the groundwater of Morocco’s main aquifers using isotope and nuclear methods. The results of this endeavor have been published in a book entitled “Isotope hydrology Atlas of Morocco”. This Atlas demonstrates how isotope compilations can be used as a national and international resource for sustainable groundwater management, and should help promote increased utilization of isotope methods in other countries. The accumulated knowledge in isotope hydrology and the infrastructure established by CNESTEN and IAEA assistance are now made available to the countries of the region through the selected AFRA Regional Designated Centre and IAEA Collaborating Centre in terms of human capacity building and provision of advisory assistance and mentorship as well as analytical services. Accordingly, CNESTEN provided, over the last decade, analytical services, training, mentorship and advisory assistance to several countries from Africa, Asia and Europe. (author)

[en] ICALEPCS2001 covered the fields of control and operation of particle accelerators, detectors, telescopes, fusion devices, nuclear reactors and other large experimental facilities. Both hardware and software aspects of control systems were addressed

[en] Under DOE sponsorship, McDermott Technology, Inc. (MTI), Babcock and Wilcox Company (B and W), and Minergy Corporation developed and evaluated a sludge derived fuel (SDF) made from sewage sludge. Our approach is to dry and agglomerate the sludge, combine it with a fluxing agent, if necessary, and co-fire the resulting fuel with coal in a cyclone boiler to recover the energy and to vitrify mineral matter into a non-leachable product. This product can then be used in the construction industry. A literature search showed that there is significant variability of the sludge fuel properties from a given wastewater plant (seasonal and/or day-to-day changes) or from different wastewater plants. A large sewage sludge sample (30 tons) from a municipal wastewater treatment facility was collected, dried, pelletized and successfully co-fired with coal in a cyclone-equipped pilot. Several sludge particle size distributions were tested. Finer sludge particle size distributions, similar to the standard B and W size distribution for sub-bituminous coal, showed the best combustion and slagging performance. Up to 74.6% and 78.9% sludge was successfully co-fired with pulverized coal and with natural gas, respectively. An economic evaluation on a 25-MW power plant showed the viability of co-firing the optimum SDF in a power generation application. The return on equity was 22 to 31%, adequate to attract investors and allow a full-scale project to proceed. Additional market research and engineering will be required to verify the economic assumptions. Areas to focus on are: plant detail design and detail capital cost estimates, market research into possible project locations, sludge availability at the proposed project locations, market research into electric energy sales and renewable energy sales opportunities at the proposed project location. As a result of this program, wastes that are currently not being used and considered an environmental problem will be processed into a renewable fuel. These fuels will be converted to energy while reducing CO(sub 2) emissions from power generating boilers and mitigating global warming concerns. This report describes the sludge analysis, solid fuel preparation and production, combustion performance, environmental emissions and required equipment