Main heat transport system

During normal operation, the main circulator transports hot helium at 1266°F (686°C) from the bottom of the core to the steam generator which, in turn, produces superheated steam at I005°F (541 °C) and 2500 psia. The cold helium at 496°F (258°C) is returned to the top of the reactor core. During normal shutdown and refueling, the non-safety auxiliary shutdown heat removal system removes core afterheat if the main heat transport system is not operational. 

Main heat transport system, with specification of heat removal path in normal operation and in accidents... 

The scheme of the UNITHERM main heat transport system is shown in Fig. 11-13. All trains shown in the diagram (except for LOCA trains) are redundant and in continuous operation. 

The function of the main heat transport system is to remove nuclear heat from the reactor core in forced circulation mode under normal operation and in natural convection mode under shutdown conditions. 

A schematic of the 4S main heat transport system with specification of heat removal path in normal operation and in accidents is given in Fig. XIV-12 a brief explanation of this scheme... 

A scheme of the 4S-LMR main heat transport system with the indication of heat removal path in normal operation and in accidents is given in Fig. XV-11. The reactor incorporates redundant passive decay heat removal systems. Specifically, a reactor vessel auxiliary cooling system (RVACS) is adopted in which the natural convection airflow removes the decay heat radiated through the guard vessel. The heat removal capability depends on the thermal radiation area. A specific (per thermal power) heat radiation area of small reactors is larger than that of medium sized or large reactors. It is expected that about 1% of the nominal power could be removed with the RVACS. 

FIG. XXII-8. Burn-up swing of a 25 MW(th) SSTAR and a 45 MW(th) SSTAR design. Main heat transport system... 

FIG.XXni- 9. Main heat transport system of STAR-LM coupled to S-CO2 Brayton cycle. 

Apart from thorium utilization and establishing a slightly negative void coefficient of reactivity, the AHWR incorporates several passive safety features, which include core heat removal through natural circulation of the coolant in the main heat transport system. 

A schematic of the main heat transport system is given in Fig.9.48. 

The scheme of the main heat transport system specif5nng the path of heat removal in normal operation and in accidents is presented in Fig. 1-8. 

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