Sealing, high-temperature

Some licensees have a switch to bypass RCIC high steam tunnel temperature trips. Some licensees are evaluating improvements to prevent seal LOCAs from loss of seal cooling which are most important for W plants, but B W licensees identified improvements related to alternate seal flow capability under loss of power conditions. The use of high temperature seals is noted for some W plants. Many PWR IPEs identify AFWS improvements. These include additional backup water supplies such as the firewater system and redundant pump cooling capability. Other reliability... 

As is obvious, many potential hurdles discussed in the previous sections do not apply to appHcation of zeolite membranes at the micro- and particle levels. Issues Hke scale-up and high-temperature sealing do not play a role here. Additionally, coated catalyst particles do not require a change of reactor, but only replacement of the catalyst. Application of zeoHte membranes at these levels is therefore considered to be easier and their implementation will probably occur earlier. 

TYPES OF HIGH-TEMPERATURE SEALS 5.2.1 Glass Seals... 

A high-temperature seal for a solid oxide cell needs to be hermetic and be able to withstand thermal cycles. However, there is sparse literature available regarding seal... 

R.N. Singh, High Temperature Seals for Solid Oxide Fuel Cells, 28th International Conference on Advanced Ceramics and Composites, eds., E. Lara-Curzio and M.J. Readey, Cocoa Beach, FL, 25 (3), pp. 299-307 (2004). 

SOFCs can have a planar geometry similar to PEFCs, but the leading technology is tubular, as shown in Fig. 24-54. The advantage of the tubular arrangement is the absence of high-temperature seals. 

However, these advantages may be offset by the use of high temperature seals and the fact that the components will be subject to more stress. Besides mechanical stress due to seals, thermal stresses may appear because of temperature gradients and cycling. Few results related to the performance of this type of SOFCs have been published. An area power density of 0.12 W/cm2 has been reported without any specification of oxidant and fuel composition and utilization [117]. 

This design is still under preliminary modeling and testing. Research is focused on the further improvement of the power density, avoiding the use of high temperature seals. 

By improving high temperature sealing procedures, a few permeance and permselectivity measurements of the membranes at temperatures as high as 600°C were possible (chapter 6). 

Alkyltellurium iodides form in yields higher than those obtained by conventional high temperature sealed-tube reactions with Te powder and alkyl halidesT Also, the (Te) -solvent slurries can be stored. 

In most cases, the cells are either in the form of tubes (open or closed-ended) or flat plates. Although the cells based on flat plates are more compact, the stacks require high-temperature seals, they are more sensitive to thermal stress and thermal cycling, and they are more difficult to pressurize. The tubular designs are more robust, allow the use of room-temperature seals, and exhibit a good thermal cycling capability. 

The main advantages ofthe tubular design are good thermal cycles resistance and no requirement for high-temperature seals. In contrast, the planar geometry provides a higher volumetric power density. 

R.E. Tressler, D.M. Taylor, "Compliant High Temperature Seals for Dissimilar Materials," Oetober 2001. 

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