PRACS cooling system

PRACS pool reactor auxiliary cooling system... 

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

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... 

Figure XIV-3 shows a general view of the 4S reactor for a 50 MW(e) plant although the size and dimensions differ from those of the reactor for a lOMW(e) plant, nearly all basic concepts are the same, except that the primary reactor cooling system (PRACS) is used in the 50 MW(e) design instead of the IRACS in the 10 MW(e) design.

RVACS - Reactor vessel auxiliary cooling system DHX - Direct heat exchanger PRACS - Primary reactor auxiliary cooling system RV -Reactor vessel... 

Reactor vessel auxiliary cooling system (RVACS) and primary reactor auxiliary cooling system (PRACS), see Fig. XV-3. 

Twelve sections of the passive reactor auxiliary cooling system (PRACS) are installed in the reactor module around the circumference of 07.0 m. The diameter and height of the PRACS vessel is 0.47 m and about 6 m, respectively. The nominal Pb-Bi coolant flow rate through 12 PRACSs makes 15% of the whole reactor flow rate. The PRACS working fluid is naturally circulated environmental air. About 1.4% of the generated power in nominal conditions is transferred to the environmental air. 

The DHRS consists of a combination of one loop of DRAGS and two loops of the primary reactor auxiliary cooling system (PRACS). The heat exchanger of DRAGS is dipped in the upper plenum within the RV. The heat exchanger of each PRAGS is located in the primary-side upper plenum of an IHX. AU of these systems can be operated based on a fiiUy passive feature with natural circulation, which requires no active components such as pumps (Yamano, 2010). 

LORL, loss of reactor level LOHS, loss of heat sink RV, reactor vessel GV, guard vessel D/2AC5, direct reactor auxiliary cooling system DHRS, decay heat removal system PRACS, primary reactor auxiliary cooling system AM, accident management. 

In the 4S, the decay heat is removed by two systems consisting of the decay heat removal coil installed in the reactor (PRACS) and the natural air ventilation from outside the guard vessel (RVACS). The analysis considers the destruction of PRACS and the RVACS cooling stack by a large falling aircraft. In addition to this extreme severe condition, 50% of the cross sectional area of the RVACS stack is assumed to be blocked. 

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