Graphitic spheres

In gray iron, most of the contained carbon is in the form of graphite flakes, dispersed throughout the iron. In ductile iron, the major form of contained carbon is graphite spheres, which are visible as dots on a ground surface. In white iron, practically all contained carbon is combined with iron as iron carbide (cementite). a very hard material. In malleable iron, the carbon is present as graphite nodules. High-alloy irons usually contain an alloy content in excess of 3%. 

As an example of intrinsic safety features, consider the HYLIFE design. The HYLIFE reactor room has no external walls or roof it is surrounded by other rooms and covered with a crane loft. The reactor room contains an inert gas (no air). The entire Li inventory can be drained in minutes in case of an air leak into the room such a leak would require hours before lithium combustion is possible. There are no water or steam components in the reactor room, and all concrete is steel lined. The lithium loop is everywhere sub-atmospheric pressure (1 Pa to 80 kPa or 10 to 620 Torr) hence, small leaks will be inward. Large leaks will fall on a sloped floor that drains to tall narrow tanks containing hollow graphite spheres that would float above spilled lithium. Additional inert gas injection capability will be available in these areas. 

Coeuret and Paulin [9] studied the recovery of copper in a pulsed granular fixed-bed cathode using copper-plated graphite spheres as the cathode bed. The spheres... 

Delanghe et al. studied the removal of mercury(II) from contaminated brines using graphite felt cathodes [25]. A 100% current efficiency for mercury removal was obtained at a potential of - 400 mV vs. SCE on a graphite felt 1 cm thick at a flowrate of 1 cm/s. This current efficiency was higher than that obtained on RVC, nickel foam platinum grids, or graphite sphere cathodes. 

In case of vertical variety, there is a packing of activated graphite spheres or lumps of 8-25 mm in diameter. The amalgam is fed in via an overhead distributor and trickles down in droplets through the bed of graphite and the... 

A two-zone core design is adopted, with one central movable column of graphite spheres surrounded by pebble fuel elements. Tlie purpose of using the two-zone core design is to increase the power output of a single reactor module while maintaining the passive decay heat removal capability. 

Particulates in diesel exhaust gas, often called soot , are agglomerates of spherical particles, 10 to 30 nm in size, and composed around graphitic spheres. In and on these spheres, hydrocarbons, water, and sulfate are condensed. In the hydrocarbon firaction among others polynudear aromatics (PAH) are present and these are thought to have carcinogenic properties. 

Electrolysers with packed bed cathodes, so-called Enviro-cells (Deutsche Carbon AG/ENVIROCELL Umwelttechnik GmbH, Germany) with graphite spheres in the cathodic compartment and an inert or ion-exchange membrane (Pig. 14), are used in indust-... 

Figure 14. Scheme of a packed bed electrolyser. 1 Anode compartment, 2 cathode compartment filled with graphite spheres and separated by a diaphragm. 

Vertical decomposers are towers packed with graphite spheres or particles 8-20 mm in diameter. A typical cross section is 0.35 m per l(X)kA of cell load. The amalgam flows from the top and water is fed into the bottom of the tower. Since the volume of the decomposer is small, it is necessary to cool the hydrogen generated during the course of the amalgam decomposition reaction. The mercury inventory is small with the vertical decomposer. However, the caustic contains more mercury. 

The typical HTGR fuels are the pebble-bed type, which is a graphite sphere, and the block type fuel i.e., a graphite block into which coated particles are inserted (Saito et al. 1994). The former is generally suitable for high temperature operation because the fuel spheres circulate slowly in the reactor and each fuel sphere is exposed to high temperature in the reactor for... 

In order to initiate a reactor scram, the power supply to the drive is interrupted, thus causing the rod to drop freely into its lowest position in the bore holes of the side reflector due to gravity. Eighteen small sphere shutdown units serve to compensate the reactivity increase due to a cold, unpoisoned core. Graphite spheres with a 10% B4C content and a diameter of approx. 10 mm are used as shutdown elements. The spheres, which are stored in storage containers located above the top thermal shield and over the side reflector, drop freely into the reflector bore holes on demand. 

A second type of GCR used the pebble bed concept with helium as a coolant. The uranium and thorium fuel was imbedded in graphite spheres and cooled with helium. The high temperature thorium fueled reactor (THTR) operated between 1985 and 1989 in Germany. It produced 760 MWt and 307 MWe. The thorium in the fuel pellets was used to breed Two GCR power plants have been operated in the United States. The first was Peach Bottom Unit 1, which provided 40 MWe. The second was the Fort St. Vrain reactor, which provided 330 MWe. 

Core Cylindrical fixed bed of spherical fuel elements, spherical absorber elements and graphite spheres the effective diameter is 3.0 m the height is 3.0 m. Reflectors - molten salt coolant... 

Corrosion rates differ only sligthly in the various cast iron types. Grey cast iron (GC) is eroded somewhat more than cast iron with lamellar graphite (GGL) and ductile cast iron with graphite spheres (GCG). Table 29 lists the free corrosion potentials and corrosion rates for uniform surface corrosion in the cast iron types acc. to DIN EN 1561 [87], DIN EN 1563 [88] and DIN 1694 [89]. 

In a few geological occurrences, graphite forms compact spherical aggregates with radial internal textnres, similar to those observed in graphite spheres in cast iron. One prominent natural... 

Fuel cycle option, basic Once-through fuel cycle U dioxide fuel in TRISO coated particles within graphite spheres on-line refuelling Once-through fuel cycle U dioxide fuel in TRISO coated particles within graphite fuel compacts... 

Fuel TRISO ceramic coated U-235 in graphite spheres... 

It is also known as ductile iron in USA and is produced by treating a high carbon equivalent liquid iron with manganese or cerium to prevent the formation of graphite flakes. The structure at room temperature comprises a graphite spheres in a matrix of ferrite. Ductility is increased by heating to 900°C followed by a slow quench. Typical properties of cast irons are given in Table 9.12. 

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