Top and bottom plugs

The top plug (see Fig. 2.F) serves not only as the upper tank closure but also as the primary support for the control rods and their drive mechanisms. Like the bottom plug, it is a hollow stainless steel shell partially filled with lead shot to fulfill shielding requirements. On this plug is mounted a platform which supports the control motors, limit switches, etc. for the control rpds. Underneath the top plug on four supports hangs the spider which holds the bearings for the 12 control rods (see Section 2.2). 

Since the top plug must be taken off in order to replace fuel elements or control rods, it is designed to be easily lifted by the overhead crane and lowered to a dry dock on the first floor. 

The fuel for the reactor will be enriched, uranium alloyed with aluminum and made up Into aluminum-clad plates 0.060 in. thick. Because of the picture-frame type of construction used, no uranium is exposed to 

Referring to Fig. 2.2.B, the bottom end.of the fuel assembly is seen near the lower right-hand side of the picture. Both end boxes are, of course, open to allow water to pass freely-through the assembly from top to bottom. 

Each of the fuel assemblies contains approximately 140 g of and it is expected that the MTR will contain about 23 of these units when in full operation. The arrangement of these- units into.a lattice and their supporting structure can best be seen by referring to Figs..2.D and E. 

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The FMC In-Line Extractor is widely used in the domestic industry, most particularly in Florida, because it can effect simultaneous recovery of both juice and oil. A five-headed extractor can process from 325 to 500 fruit/minute. The extractor consists of a bottom cup, into which the fruit is fed, and an upper cup that meshes with the bottom as circular plugs are cut from the top and bottom of the fruit. The fruit in the bottom cup is compressed as the upper cup descends and juice and other fruit components are forced through the bottom plug into a strainer tube. The contents of the strainer tube, rag, seeds, and cell sacs, are squeezed between the top and bottom plugs resulting in almost complete extraction of juice and, in essence, a first-finishing operation since the plug (seeds, pulp, and peel) is separated from the juice. As the fruit is squeezed in the cup, peel oil expressed from the flavedo and small pieces of peel are washed into a conveyer by a water spray that surrounds the extractor cup. The valuable oil is recovered from the oil/water slurry. 

In this early phase of the extraction cycle, the upper cup moves downward to cause pressure on the citrus so that the top and bottom plugs begin to be cut. 

Figure I. Cross sectional view of the high pressure autoclave with top and bottom plug, sample tube, macor plug and sample coil.

Upon consideration of these facts by the parties concerned (Steering Committee, IDO, ORNL, and Blaw-Knox), it was suggested that ORNL assume the responsibility for design and procurement of the reactor tank sections B, C, and D,.the internal components, and the top and bottom plugs. Tank sections A and E, being fixed permanently in the concre.te structure, were considered as part of that structure and consequently remained with Blaw-Knox for detailed engineering. 

Top end Bottoa plugs. The. top and bottom plugs, complete the watertight shell, around- the active lattice, and form part of the support system for the control, rods,. i... 

Lane, J. A., Shielding Requirements, Top and Bottom Plugs. ORNLCF-SO-7-7 July 5, 1950. 

In one extractor (FMC Inc.), the fmit is located between two cups having sharp-edged metal tubes at their base. The upper cup descends and the many fingers on each cup mesh to express the juice as the tubes cut holes in the top and bottom of the fmit. On further compression, the rag, seeds, and juice sacs are compressed into the bottom tube between the two plugs of peel. A piston moves up inside the bottom tube forcing the juice through perforations in the tube wall. A simultaneous water spray washes the peel oil expressed during extraction away from the peel as an oil—water emulsion the peel oil is recovered separately from the emulsion. 

FIG. 11-44 Typical construction of a tube bundle with plug headers (1) tube sheet (2) plug sheet (3) top and bottom plates (4) end plate (5) tube (6) pass partition (7) stiffener (8) plug (9) nozzle (10) side frame (11) tube spacer (12) tube-support cross member (13) tube keeper (14) vent (15) drain (16) instrument connection. (API Standard 661.)... 

For services where solids are present or evaporation of droplets on the mesh might leave a solid crust, it is usual practice to install sprays above or below the mesh to cover the unit with W ater (or suitable solvent) on scheduled (or necessary) operating times, as the plugging builds up. This is checked by a manometer or other differential pressure meter placed with taps on the top and bottom side of the mesh installation. 

For liquids, there are several ways to apply the principle of correct sampling across the vertical dimension. A tool that uses the same idea as the thief is the coliwasa (Composite Liquid WAste SAmpler), shown in Figure 3.9. They come in various lengths and diameters, depending on the depth and size of the container lot. This hollow column is lowered slowly through the liquid until the desired depth is reached. Then the top and bottom are plugged to retain a core. 

Figure 4-14. High-pressure falling-sinker viscometer. Pressure is transmitted to the test liquid through the side arm and acts on the bellows-like reservoir of the viscometer chamber. The instrument is oriented vertically. Time of fall of the sinker is monitored by electrical contact at the top and bottom pins, a Viscometer tube, b Sinker, c Reservoir. d Insulated lead, e Insulated pin. f End plugs, g Terminal plug. After Bradbury, Mark and Kleinschmidt [20].

The most common applications of this technique in distillation and absorption columns is for liquid level and liquid level interface detection, especially when normal level-measuring techniques suffer from plugging. Neutron backscatter techniques have also been used for froth height measurements on trays and downcomers, and for measuring the top and bottom of packed beds. One case history has been described (71) where downcomer froth height measurements using the neutron backscatter technique led to a detection of downcomer deposits which caused premature flooding of the column. The author is familiar with one case where this technique successfully detected overflow of a packed tower distributor. 

Fig. 1.6. Roller hearth furnace, top- and bottom-fired, multizone. Roller hearth furnaces fit In well with assembly lines, but a Y In the roller line at exit and entrance Is advised for flexibility, and to accommodate parking the loads outside the furnace In case of a production line delay. For lower temperature heat treating processes, and with Indirect (radiant tube) heating, plug fans through the furnace celling can provide added circulation for faster, more even heat transfer. Courtesy of Hal Roach Construction, Inc.

The HG-9. liner is the, most critical of these holes with regard to cooling. The aluffiinuR) liner for this facility is perforat.ed top and bottom to match the graphite cooling holes in the plug. 

A general (diagrammatic) cross-sectional view of the mould is presented in Fig. 2, from which it may be seen that the mould consists of three essential parts, viz., (1) an aluminium alloy split female mould, (2) an intermediate silicone rubber male core, and (3) a tapered central aluminium alloy plug. Important features to note are the spacer inserted between the split halves of the outer mould, the available space below the central plug, and the channels moulded into the silicone rubber (top and bottom) to form a reservoir for the resin. Prior to use with epoxide resins, the mould surfaces are treated with a silicone release agent (Tego 290 -Ambersil Ltd.) and cured for 3 hours at 230 C. 

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