Auxiliary cooling system

Another feature of the large HTGRs was the core auxiliary cooling system which provided an independent means of core afterheat removal in the event that the main coolant loops (i.e., steam generators and... 

Figure 2. Schematic diagram of the reactor cooling systems consisting the main cooling system, auxiliary cooling system and vessel cooling system of the HTTR...

Auxiliary cooling system Main cooling system... 

Thermal loads upon the process heat exchanger do not allow rapid temperature change rates. Therefore in case of the demand for a decay heat removal system after a fast shutdown of the reactor, an auxiliary cooling system should be used rather than the main cooling system. In addition, much of the decay heat would be removed via the core surfaces to the liner cooling system [10]. 

The safety concept considers two nuclear shutdown systems, a set of six reflector rods for reactor scram and power control and a KLAK system of small absorber balls for cold and long-term shutdown. Decay heat removal is made via the heat exchanger, an auxiliary cooling system, and the panel cooling system inside the concrete cavern, or, in case of a failure of these systems, passively by heat transfer via the surface of the reactor vessel. 

The state inside the piping room (C) was checked again and an increase in white fume was observed. Accordingly, the reactor was manually tripped at 21 20. After the trip, the reactor was cooled down by the auxiliary cooling system (ACS) and was maintained in the low-temperature shutdown state. To minimize leakage, sodium in the secondary circuit (loop C) was drained at 22 55 and drain operations were complete at 00 15, the following day. 

Six-control rod subassemblies made of 90% enriched B4C were used in JOYO MK-II and were located symmetrically in the third row. In 1994, one control rod was moved to the fifth row to provide a position for irradiation test assemblies with on-line instrumentation. Since then, the control rod subassemblies have been loaded asymmetrically. The JOYO cooling system has two primary sodium loops, two secondary loops and an auxiliary cooling system. The cooling system uses approximately 200 tons of sodium. In the MK-II core, sodium enters the core at 370°C at a flow rate of 1 100 tons/h/loop and exits the reactor vessel at 500°C. The maximum outlet temperature of a fuel subassembly is about 570 C. An intermediate heat exchanger (IHX) separates radioactive sodium in the primary system from non-radioactive... 

Fig. 2.1. Schematic of the LS-VHTR. (DRAGS = direct reactor auxiliary cooling system PRACS = pool reactor auxiliary cooling system.)...

To meet the passive safety requirements of the NGNP, the AHTR uses a reactor vessel auxiliary cooling system (RVACS) similar to that of S-PRISM. It may also use a direct reactor auxiliary cooling system (DRAGS) similar to what was used in the Experimental Breeder Reactor II to supplement the RVACS and reduce the reactor vessel temperature. 

It is also possible to supplement the RVACS heat removal capacity using a direct reactor auxiliary cooling system (DRAGS) based on natural circulation of an intermediate coolant from bayonet heat exchangers in the reactor vessel to air-cooled heat exchangers. This type of DRAGS system was used in the Experimental Breeder Reactor II (EBR-II) with sodium-potasium as the intermediate coolant. There are a variety of potential intermediate coolants, several of which have been used extensively in industry for similar heat transfer applications. 

Primary Reactor Auxiliary Cooling System (PRACS)... 

Four primary reactor auxiliary cooling systems (PRACS) are used A cooling coil is installed in the inlet plenum of each IHX and a heat transfer coil is installed in the mr cooler of ultimate heat sink Coolant is circulated by EM pumps supported by emergency AC power The air cooler consists of a blower, a stack, vanes and dampers The blower is supported by the emergency AC power The vanes and the dampers are operated by the emergency DC power Decay heat removal by natural circulation is possible to mitigate a total blackout event (loss of all AC power)... 

Decay heat removal Primary reactor auxiliary cooling system (PRACS) Steam/water system Active Active N/C operation available Non-safety grade... 

The natural air cooling system in the reactor vessel is designed so that it is capable of removing decay heat without operation of the Primary Reactor Auxiliary Cooling System (PRACS). 

LOF Primary Reactor Auxiliary Cooling System (PRACS) Reactor Vessel Auxiliary Cooling System (RVACS) TOP Mechanical stop of hydraulic drive system of reflector... 

PRACS) Reactor Vessel Auxiliary Cooling System (RVACS) Passive 1 system... 

AT.MR primary sodium and reactor vessel auxiliary cooling system (RVACS) air flow circuit using for heat removal. 

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