Flux targets

Figure 2. Advanced Catalyzed Membranes Approach Commercial Flux Target...

Sub-scale thin film membranes were also tested at atmospheric pressure for periods of over 1200 hours. Tests of advanced catalyzed membranes demonstrated oxygen fluxes that approach the commercial flux target range, as shown in Figure 2. 

For a PdAu membrane (GTC-31), no flux reduction was observed for the WGS mixture compared to a pure H2 feed gas at the same 25 psig partial pressure difference and 400°C. A typical pure H2 flux was 245 SCFH/ft = 0.93 mol/m s for a 100 psig H2 feed gas pressure at 400°C. This flux exceeds the 2010 IX)E Fossil Energy pure hydrogen flux target. The H2/N2 pure gas selectivity of membrane GTC-31 was about 1,000 at a partial pressure difference of 100 mi. 

Both on-line time and throughput have benefited from improved accretion control in the furnace. Reduction in accretions in the reaction shaft area has led to better operation of the coke checker. Accretion management has been affected mainly by the throughput in the furnace, proper control of the oxygen potential in the reactirni shaft, and proper fluxing targets. 

The benefit of the residue blending was observed inunediately as illustrated in Figure 4. The variation in both iron and lead assays was much less after the project was cormnissioned, and as a result, the fiequent assays shown in the figure, used to aid in the setting of the fluxing targets, were actually discontinued. 

Because H2 flux does not go to zero, the surface scale must be active for H2 dissociation. The dissociation activity of the Pd4S surface has been studied by both first-principle calculations and experiments. First-principle calculations reveal that the barrier to H2 dissociative adsorption on Pd4S is 0.8 eV, compared to 0 eV for clean Pd [22]. This increase is enough to slow dissociation rates, but not enough (in the absence of site blocking) to make the membrane miss the flux targets established by the DOE [22]. 

When a material is placed in a reactor core s neutron flux, target atoms in the material absorb neutrons and become activated atoms, At the same time, the activated atoms decay. A balance is reached in the material when the rate of activation equals the rate of decay that determines the equilibrium or steady state activity in the material,... 

Figure Bl.23.2. (a) Shadow cone of a stationary Pt atom in a 4 keV Ne ion beam, appearing with the overlapping of ion trajectories as a fiinction of the impact parameter. The initial position of the target atom that recoils in the collision is indicated by a solid circle, (b) Plot of the nonnalized ion flux distribution density across the shadow cone in (a). The flux density changes from 0 inside the shadow cone, to much greater than l in the focusing region, converging to 1 away from the shadow cone edge, (c) Blocking cones...

This relation is a direct consequence of the conservation of flux. The target casts a shadow in the forward direction where the intensity of the incident beam becomes reduced by just that amount which appears in the scattered wave. This decrease in intensity or shadow results from interference between the incident wave and the scattered wave in the forward direction. Figure B2.2.2 for the density P (r) of section B2.2.6 illustrates... 

A partial acknowledgment of the influence of higher discrete and continuum states, not included within the wavefunction expansion, is to add, to the tmncated set of basis states, functions of the fomi T p(r)<6p(r) where dip is not an eigenfiinction of the internal Flamiltonian but is chosen so as to represent some appropriate average of bound and continuum states. These pseudostates can provide fiill polarization distortion to die target by incident electrons and allows flux to be transferred from the the open channels included in the tmncated set. 

The analysis of steady-state and transient reactor behavior requires the calculation of reaction rates of neutrons with various materials. If the number density of neutrons at a point is n and their characteristic speed is v, a flux effective area of a nucleus as a cross section O, and a target atom number density N, a macroscopic cross section E = Na can be defined, and the reaction rate per unit volume is R = 0S. This relation may be appHed to the processes of neutron scattering, absorption, and fission in balance equations lea ding to predictions of or to the determination of flux distribution. The consumption of nuclear fuels is governed by time-dependent differential equations analogous to those of Bateman for radioactive decay chains. The rate of change in number of atoms N owing to absorption is as follows ... 

In the sputtering process, each surface atomic layer is removed consecutively. If there is no diffusion in the target, the composition of the vapor flux leaving the surface is the same as the composition of the bulk of the material being sputtered, even though the composition of the surface may be different from the bulk. This allows the sputter deposition of alloy compositions, which can not be thermally vaporized as the alloy because of the greatly differing vapor pressures of the alloy constituents. 

This simulation can be achieved in terms of a source—sink relationship. Rather than use the gas concentration around the test object as a target parameter, the test object can be surrounded by a sink of ca 2-7T soHd angle. The solar panel is then maintained at its maximum operating temperature and irradiated by appropriate fluxes, such as those of photons. Molecules leaving the solar panel strike the sink and are not likely to come back to the panel. If some molecules return to the panel, proper instmmentation can determine this return as well as their departure rates from the panel as a function of location. The system may be considered in terms of sets of probabiUties associated with rates of change on surfaces and in bulk materials. 

Production in Target Elements. Tritium is produced on a large scale by neutron irradiation of Li. The principal U.S. site of production is the Savaimah River plant near Aiken, South Carolina where tritium is produced in large heavy-water moderated, uranium-fueled reactors. The tritium may be produced either as a primary product by placing target elements of Li—A1 alloy in the reactor, or as a secondary product by using Li—A1 elements as an absorber for control of the neutron flux. 

This paper presents calculation and experimental studies of a moderator with a thermal neutron extraction channel, based on an NG-400 pumped neutron generator produced by the All-Russia Automation Research Institute. The neutron generator provides a maximum 14-MeV neutron flux density of 5T0 n/cm -s on the outer surface of the target chamber. 

The thermal radiation received from the fireball on a target is given by equation 9.1-31, where Q is the radiation received by a black body target (kW/m ) r is the atmospheric transmissivity (dimensionless), E = surface emitted flux in kW/m", and f is a dimensionless view factor. 

The heat flux, E, from BLEVEs is in the range 200 to 350 kW/m is much higher than in pool fires because the flame is not smoky. Roberts (1981) and Hymes (1983) estimate the surface heat flux as the radiative fraction of the total heat of combustion according to equation 9.1-32, where E is the surface emitted flux (kW/m ), M is the mass of LPG in the BLEVE (kg) h, is the heat of combustion (kJ/kg), is the maximum fireball diameter (m) f is the radiation fraction, (typically 0.25-0.4). t is the fireball duration (s). The view factor is approximated by equation 9.1-34. where D is the fireball diameter (m), and x is the distance from the sphere center to the target (m). At this point the radiation flux may be calculated (equation 9.1-30). 

It is assumed that the target surface faces toward the radiation source so that it receives the maximum incident flux. The rate of combustion depends on the release. For a pool fire of a fuel with a boiling point above the ambient temperature (Tg), the combustion rate can be estimated by the empirical relation ... 

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