Blanket chemical processing

Oxide fibers are manufactured by thermal or chemical processes into a loose wool mat, which can then be fabricated into a flexible blanket combined with binders and formed into boards, felts, and rigid shapes or fabricated into ropes, textiles and papers. The excellent thermal properties of these products make them invaluable for high temperature industrial appHcations. 

About two-thirds of the N2 produced industrially is supplied as a gas, mainly in pipes but also in cylinders under pressure. The remaining one-third is supplied as liquid N2 since this is also a very convenient source of the dry gas. The main use is as an inert atmosphere in the iron and steel industry and in many other metallurgical and chemical processes where the presence of air would involve fire or explosion hazards or unacceptable oxidation of products. Thus, it is extensively used as a purge in petrochemical reactors and other chemical equipment, as an inert diluent for chemicals, and in the float glass process to prevent oxidation of the molten tin (p. 370). It is also used as a blanketing gas in the electronics industry, in the packaging of processed foods and pharmaceuticals, and to pressurize electric cables, telephone wires, and inflatable rubber tyres, etc. 

The stress of CVD-W films can vary, depending on the deposition conditions [Joshi et al.51, Clark et al.52, Blumenthal et al.148, Sivaram et al.149), by one order of magnitude (ie. from 3xl09 to 13xl09 dyne/cm2) and is mostly tensile. Experience has shown that for a plug process the stress is seldom a problem since the majority of the film is removed during the etch back process. Loss of adhesion is usually not observed in the blanket-plug process. When the interfaces between the different films are clean the adhesion will be formed by chemical bonds (1-2 eV) instead of (weak) physical forces (ca. 0.2 eV).To remove a film with an adhesion of 1 Ev per... 

Fuel composition may change from uranium to plutonium, and cladding from aluminum to zirconium to stainless steel. In some cases blankets, moderators, and coolants must be processed, and these will introduce thorium, beryllium, NaK, and bismuth to the chemical process. These changes in materials will present new chemical and corrosion problems in waste treatment processes and waste storage procedures. 

A dissolver solution of irradiated fast neutron reactor mixed oxide (MOX) fuel in JAEA contains a number of TRU elements and FPs than in KfK Since U is used as blanket fuel and TRU elements are sup>posed to recover by other chemical process, it is need to remove TRU elements and FPs from UNH crystals in the U crystallization process. It would be also bring about reduction in the cost for the recovered U storage and the blanket fuel fabrication due to decreased radiation shielding. Therefore, the behavior of TRU elements and FPs in the U crystallization process must be confirmed experimentally. 

Gaseous carbon dioxide is used to carbonate soft drinks, for pH control in water treatment, in chemical processing, as a food preservative, as an inert blanket in chemical and food processing and metal welding, as a growth stimulant for plant life, for hardening molds and cores in foundries, and in pneumatic devices. 

Also identified in Figure 1.3 are utility streams. Utilities are needed services that are available at the plant. Chemical plants are provided with a range of central utilities that include electricity, conpressed air, cooling water, refrigerated water, steam, condensate return, inert gas for blanketing, chemical sewer, waste water treatment, and flares. A list of the common services is given in Table 1.3. which also provides a guide for the identification of process streams. 

While chemical processing sharply discontinues the growth of in the blanket, the power level in the blanket may markedly overshoot the equilibrium level, as shown in P ig. 2-15(b). An overshoot is obtained when the blankeUU concentration reaches its maximum value before core processing starts. Table 2-14 shows the peak values of blanket power computed for the reactors studied, along with the equilibrium values. 

Results similar to tho.se given above have also been obtained [33] for two-region breeders having various concentrations of thorium in the core. The core diameter was set at 4 ft, the pressure-vessel diameter at 9 ft, and the blanket thorium concentration at 1000 g Th/liter. The core thorium concentrations studied were 100, 150, and 200 g Th/liter. As before, the moderator was heavy water in both core and blanket volumes, and both regions operated at a mean temperature of 280°C the Zircaloy-2 core tank was 0.33 in. thick. Calculations were performed at a constant total power of 60 thermal Mw. The same chemical processing conditions were assumed... 

A third sampling station for the HIlE-2, identical to the fuel and blanket facilities except for larger passages and a modified isolation chamber, is employed for sampling a fuel stream in the chemical processing facility. This stream has the order of 50 times the solids concentration of the other streams being sampled. 

Since this fluid has practically the same physical properties as th it of the con, it would be possible to balance pre.ssures acro.ss the graphite wall separating the blanket from the core and, in the ( vent of mixing the core and blanket fluids, no violent reactions would en.sue. Furthermore, from a chemical processing point of k w, an all-metallic I)lanket system offers consideralde advantage when p3 -rometallurgical proc( ssing techniques are used. 

As is pointed out in Chapter 20, the easiest blanket to handle in the LMFR would be a 10 w/o thorium-bismuthide slurry in bismuth. Chemical processing of this blanket would be very similar to the core processes already described. The major problem consists in transferring the bred uranium and protactinium from the solid thorium bismuthide to the liquid bismuth phase, so that they can then be chemically processed. Two examples of proposed processes are shown in Fig. 22-11, which shows a process that can be used with the fused chloride salt FPS removal process, and in Fig. 24-19, which shows a flowsheet for a process to be used with the fluoride volatility process. 

As yet neither of these processes has been tried in the laboratory. As work progresses on the bismuthide blanket system, further work on the chemical processing will be carried out. 

An economic amxlysis of the effects of changing the blanket power fraction was performed to determine the optimum core-blanket power split under e( uilil)rium operating conditions. The parameters affecting this choice are (1) fission-product poison levels in the blanket, (2) fission-product poison levels in the core, and (3) chemical processing costs. 

Fission-product poisons in the blanket. The chemical processing of the blanket slurry accomplishes two things ... 

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