Molten salt-cooled reactors

Furthermore, HEEP will consider several reactor concepts including water reactors such as PWR and PHWR for the lower temperature range, the very high temperature reactors (VHTR), fast breeder reactors (FBR) and molten-salt cooled reactors for the high temperature range, and super-critical water reactor (SCWR) capable of output temperatures up to around 625°C for the medium range of temperature. 

Molten salt-cooled reactor (MSR), with a fluid fuel and an indirect power cycle. 

Higher output temperatures. The maximum exit eoolant temperature for a molten-salt-cooled reactor can be higher than that for a gas-cooled reactor— assuming the same maximum fuel... 

Heat conduction to earth. Heat is conducted to the earth surroimding the silo and ultimately to the environment. The 600-MW(t) MHTR uses the same approach for ultimate heat rejection in a beyond-design-basis accident. However, significant differences are noted between gas-cooled and molten-salt-cooled reactors in their ability to reject heat to the ground. 

About thirty concepts of small reactors without on-site refuelling are being analyzed or developed in the Russian Federation, Japan, India, the U.S.A., Brazil, and Indonesia. They cover different reactor lines water cooled, sodium cooled, lead or lead bismuth cooled and molten salt cooled reactors. 

TABLE 6. HIGH TEMPERATURE GAS COOLED, LEAD COOLED, AND MOLTEN SALT COOLED REACTORS... 

Table 3 lists technical specifications for small autonomous reactors Table 4 contains specifications for water cooled reactors Table 5 gives data for liquid metal cooled reactors and Table 6 presents the characteristics for high temperature lead, gas, or molten salt cooled reactors. 

High temperature designs including hydrogen production 15-25 years Pb and molten salt cooled reactors at 700°C to 1000°C core outlet temperature using nitride or TRISO type fuel... 

RRC KI develops a concept of a high temperature autonomous micro-particle fuelled molten salt cooled reactor — the MARS. It is currently designed with a capacity of 16 MW(th) and a 15 to 60-year refuelling interval (ANNEX XXVm). The concept incorporates a fixed bed of HTGR type spherical fuel elements with TRISO fuel and a molten salt coolant. The secondary circuit makes use of an open air-turbine cycle. 

MICRO-PARTICLE FUEL AUTONOMOUS MOLTEN SALT COOLED REACTOR (MARS)... 

No operations with fuel are performed during the entire reactor lifetime therefore, there is no storage capacity for fresh or spent fuel elements on the site. Different from pebble bed high temperature gas cooled reactors (HTGRs) and previous high temperature molten salt cooled reactors with HTGR type fuel (abbreviated as VTRS in Russian), the MARS concept incorporates no pebble transport. 

About 50 concepts and designs of the innovative SMRs are under development in more than 15 IAEA Member States representing both industrialized and developing countries. SMRs are under development for all principle reactor lines, i.e., water cooled, liquid metal cooled, gas cooled, and molten salt cooled reactors, as well as for some non-conventional combinations... 

Innovative SMR designs are under development for water cooled, gas cooled, liquid metal cooled and molten salt cooled reactor lines, as well as some non-conventional combinations thereof The targeted timelines of readiness for deployment vary between 2010 and 2030 the major concerns addressed by the innovation cover a broader spectrum of subject areas as compared to the operating and near term evolutionary NPPs, see Table 1. Such extended consideration is apparently due to the anticipated growth and geographical expansion of nuclear power. 

A Molten-Salt-Cooled Reactor Reduces Reactor Temperatures Compared to Gas-Cooled Reactors... 

Figure 2.7 MSR Molten salt-cooled reactor with outlet temperatures within 700—800°C (shown with indirect Brayton power cycle).

An IHTR is a pebble-bed molten salt-cooled reactor. Pebbles consist of TRISO-coated particle fuel, and the coolant is driven through natural circulation. The reactor core is a long right circular cylinder with an annular core that consists of fuel pebbles and molten salt coolant. Fig. 15.13 shows a schematic of a 600-MWth IHTR. There are graphite neutron reflectors in the center and on the top, bottom, and outside of this fuel annulus. Vertical bores in the central and outer reflectors are provided for the reactivity control elements. R D activities being pursued include a molten salt natural circulation loop, as shown in Fig. 15.14, which has been set up to perform thermal... 

Emergency dump tanks Figure 1.5 Diagram of a molten salt-cooled reactor. 

SFR, sodium-cooled fast reactor GFR, gas-cooled fast reactor LFR, lead-alloy-cooled fast reactor VHTR, very-high-temperature reactor iSCW / , supercritical water reactor MSR, molten salt-cooled reactor. 

The supercritical water-cooled reactor (SCWR) and molten salt-cooled reactor (MSR) are promising prospects, but need extensive developments to achieve the same level of maturity as the previous ones. 

In 2002, the Generation IV International Forum selected six systems as Generation IV technologies very-high-temperature reactors (VHTRs), supercritical water-cooled reactors (SCWRs), gas-cooled fast reactors (GFRs), lead-cooled fast reactors (LFRs), sodium-cooled fast reactors (SFRs), and molten salt-cooled reactors (MSRs). As shown in Table 12.1, the spectra of the operating conditions for the six selected types of reactors are versatile [1]. 

It has also been proposed that heat exchangers be manufactured with C/C materials, both for VHTR and, more recently, for molten salt-cooled reactors (MSRs). For this last type of reactor, other components can also be envisaged, such as control rods, internal drivers, core barrels, and internal pieces. 

Specific issues related molten salt-cooled reactors. 

Finally the molten salt-cooled reactor (MSR) and supercritical water-cooled reactor (SCWR) are promising prospects, but need extensive material developments. They offer challenging operating conditions, mostly due to compatibility with the process fluids, as will be shortly described further. Limited data are available to allow for an optimized selection of construction materials. Austenitic stainless steels do not clearly appear to be the best choice for these applications, due to strong interactions with the aggressive environments. 

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