Particle fuel

Particle Size Reduction. Changes in the physical characteristics of a biomass feedstock often are requited before it can be used as a fuel. Particle size reduction (qv) is performed to prepare the material for direct fuel use, for fabrication into fuel pellets, or for a conversion process. Particle size of the biomass also is reduced to reduce its storage volume, to transport the material as a slurry or pneumatically, or to faciHtate separation of the components. 

Once a fusion reaction has begun in a confined plasma, it is planned to sustain it by using the hot, charged-particle reaction products, eg, alpha particles in the case of D—T fusion, to heat other, colder fuel particles to the reaction temperature. If no additional external heat input is required to sustain the reaction, the plasma is said to have reached the ignition condition. Achieving ignition is another primary goal of fusion research. 

HVOF = high velocity oxy fuel, particle velocity 700 800 m/s... 

Pyrolytic graphite was first produced in the late 1800s for lamp filaments. Today, it is produced in massive shapes, used for missile components, rocket nozzles, and aircraft brakes for advanced high performance aircraft. Pyrolytic graphite coated on surfaces or infiltrated into porous materials is also used in other appHcations, such as nuclear fuel particles, prosthetic devices, and high temperature thermal insulators. 

If a fuel is in the liquid state, such as fuel oil, most of it must be vaporized to the gaseous state before combustion occurs. This vaporization can be accomplished by supplying heat from an outside source, but usually the liquid fuel is first atomized and then the finely divided fuel particles are sprayed into a hot combustion chamber to accomplish the gasification. 

The reactor core was made up of stacks of hexagonal graphite blocks. Each fuel element block had 210 axial fuel holes and 108 axial coolant holes (Section 5, Fig. 14). The fuel particles were formed into a fuel compact (Section 5.3) and sealed into the fuel channels. 

Piccinini, N., Coated nuclear fuel particles. In Advances in Nuclear Science and Technology, Vol. 8, ed. E.J. Henly and J. Lewins, Academic Press, New York, 1975, pp. 255 341. 

Lackey, W.J., Stinton, D.P. and Seasc, J.D., Improved gas distribution for coating high-temperature gas-ceioled reactor fuel particles. Nuclear Technology, 1977, 35, 227 237. 

Lefevre, R.L.R. and Price, M.S.T., Coated nuclear fuel particles the coating process and its models, Nuclear Technology, 1977, 35, 263 278. 

Vei y small solid fuel particles such as sawdust, agricultural grains, or coal dust can sustain flames when they are suspended in air. In fact, very serious fires have occurred in grain storage towers and coal mines because of the flammability of suspended dusts. The combustion of the individual particles follows the usual pattern of solid particle burning— devolatization and char burning. The combustion of the whole cloud of particles is similar to spray combustion and its characteristics depend on the nature of the fuel, size of the particles, and the number of particles in a given volume. 

The advantages of fluid bed combustion over the more traditional technology arise from the increased turbulence provided by the bed particle action. This fluidization increases the interaction of the fuel particles with the combustion air and creates a veiy accelerated combustion environment for the incoming fuel. Additionally, the sand, initially heated to an ignition temperature for the incoming fuel, provides a... 

PsychrorneLry sec humidity determination Pugh. F. J, 205,228 PumiM. 1. 209, 228 Pulverised fuel particles 47 ... 

Fluidized-bed CVD was developed in the late 1950s for a specific application the coating of nuclear-fuel particles for high temperature gas-cooled reactors. PI The particles are uranium-thorium carbide coated with pyrolytic carbon and silicon carbide for the purpose of containing the products of nuclear fission. The carbon is obtained from the decomposition of propane (C3H8) or propylene... 

Zirconium carbide is a highly refractory compound with excellent properties but, unlike titanium carbide, it has found only limited industrial importance except as coating for atomic-fuel particles (thoria and urania) for nuclear-fission power plants.l " ] This lack of applications may be due to its high price and difficulty in obtaining it free of impurities. 

Ogawa, T., and Ikawa, K., High Temperature Heating Experiments on Unirradiated ZrC-Coated Fuel Particles, J. Nucl. Mater., 99(l) 85-93 (July 1981)... 

The protection of components against nuclear radiation is a critical factor in the design of nuclear-fission components.P CVD is used extensively in this area, particularly in the coating of nuclear fuel particles such as fissile U-235, U-233, and fertile Th-232 with pyrolytic carbon. The carbon is deposited in a fluidized-bed reactor (see Ch. 4). The coated particles are then processed into fuel rods which are assembled to form the fuel elements. 

The reactor accident at Chernobyl in April 1986 released radionuclides into the atmosphere, mostly between April 26 and May 6. Estimates of quantities released are based on observations of deposition within 30 km of the reactor. Releases in this area were predominantly highly irradiated fuel particles. It is estimated that the discharge of 241Pu through May 6, 1986 was 5,200 TBq (140 kCi), which amounted to 3% of the reactor content of this radionuclide (Askbrant et al. 1996 Pattenden and McKay 1994). The material was released mainly in the lower troposphere. 

Dissolution procedures are described for gram samples of graphite or pyrolytic carbon, milligram samples of irradiated fuel particles, and for more readily oxidised forms of carbon, such as charcoal. The first two methods involve heating the samples with mixtures of 70% perchloric and 90% nitric acids (10 1), and must only be used for graphite or pyrolytic carbon. Other forms of carbon must not be oxidised in this way (to avoid explosions), but by a preliminary treatment with nitric acid alone and in portions. 

Fuel Coated fuel particles in prismatic block... 

Sawa, K. et al., Investigation of irradiation behavior of SiC-coated fuel particle at extended burnup, /. Nucl. Tech., 142, 250, 2002. 

Gulden, T.D. and Nickel, H., Preface, Coated Fuel Particles, Nuclear Technology, 1977,35,206 213. 

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