Very-high-temperature gas-cooled reactors

VHTR Very high temperature gas-cooled reactor... 

Yoo, J.S., Tak, N.I., Lim, H.S., 2010. Development of Tritium Behavior Analysis Code for Very High Temperature Gas-Cooled Reactor. KAERiyTR-4096/2010. 

Figure 3.1 An artist s representation of a very-high-temperature gas-cooled reactor and associated hydrogen production plants.

Very-high-temperature gas-cooled reactor (VHTR) technology can provide not only electricity but also the high-temperature heat needed for industrial processes and hydrogen production. As shown in Table 12.1 and Fig. 12.1, the major issue in VHTR is the higher outlet temperature rather than the irradiation dose among the... 

This is a relatively special technique which combines the principles of fluidized - bed heating and CVD. It is primarily used to coat powders of very fine size with suitable films for special applications. The most prominent application of this technique is in the coating of nuclear fuel particles used in high-temperature gas-cooled reactors (HTGR). A typical fluidized-bed CVD reactor is shown schematically in figure 13.4. 

Silicon carbide, widely employed as an abrasive (carborundum), is finding increasing use as a refractory. It has a better thermal conductivity at high temperatures than any other ceramic and is very resistant to abrasion and corrosion especially when bonded with silicon nitride. Hot-pressed, self-bonded SiC may be suitable as a container for the fuel elements in high-temperature gas-cooled reactors and also for the structural parts of the reactors. Boron carbide, which is even harder than silicon carbide, is now readily available commercially because of its value as a radiation shield, and is being increasingly used as an abrasive. 

As for the module type high temperature gas-cooled reactor (HTGR), the range of application as the thermal energy source is very wide because the primary coolant temperature at the reactor outlet is much higher compared with other types of reactors. Therefore, utilization plans in various fields have been examined. 

As it can be seen from both Fig. 1 and Table 1, water cooled SMRs are the most suitable candidates for a near-term deployment. The high temperature gas cooled reactors with thermal neutron spectrum follow them closely. Small PWR designs from Russia are based on the experience of the marine reactors and are said to be deployable within a very short term, once the financing for a necessary limited amount of the Research, Design Demonstration (RD D) becomes available. 

Because of the small reactivity margin available for breeding in a thermal reactor, the use of the thorium cycle has mainly been associated with reactors with very good neutron economy based on low parasitic absorption, such as the high-temperature gas-cooled reactor, where graphite is used in place of metal for the fuel cladding, or heavy water reactors, with very low moderator absorption. A special case is the molten salt breeder reactor, where circulation of the fissile and fertile materials allows continuous removal not only of Pa but also of fission products. 

Of the twenty-six concepts and designs addressed, 13 (50%) are water cooled SMRs, 6 (23%) are gas cooled SMRs-high temperature gas cooled reactors (HTGRs), 6 are sodium or lead-bismuth cooled fast reactors, and 1 is a non-conventional very high temperature reactor concept, a liquid salt cooled reactor with HTGR type prismatic fuel. 

---