Reactor auxiliary

All systems and components which must fulfill, with a high level of confidence, their lOCFRlOO-related radionuclide control functions under design basis conditions are located inside buildings or structures which are designed to withstand the impact from tornado-generated missiles. The major portions of the Reactor Buildings, Reactor Auxiliary Buildings, and Reactor... 

Loss of reactor auxiliary cooling water system... 

DRAGS direct reactor auxiliary cooling system... 

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. 

The reactor auxiliary systems are similar to those found on other PWRs and typically include a primary water volume control and inventory system, a primary water purification system, radioactive liquid and gaseous effluent treatment systems, and a ventilation system. At low power levels, many of these systems may be required only on an intermittent basis and would be valved out during periods of autonomous operation. 

The NSSS comprises of various nuclear systems and auxiliaries located in Reactor Building (RD), Reactor Auxiliary Building (RAB), Station Auxiliary Building (SAB), Service... 

Two auxiliary feed pumps (one of them is standby) located in the annex to reactor auxiliary building take suction from condensate storage tanks and supply feed water to the steam generators if the main feed water system is unavailable, say, on failure of class IV power supply. 

Reactor auxiliary building is located very near to the RB to avoid long piping lengths. A separate control building has been provided as a common facility. However, the control room and control equipment rooms in this building are so laid out as to cater... 

The second block includes the reactor auxiliary and waste management building, housing the reactor water cleanup system and the liquid and solid radwaste systems, the radioactive maintenance shops, housing the active workshop, and storage rooms for potentially radioactive waste. 

Key reactor auxiliary and ancillary systems required for the GT-MHR, in addition to those described above, are as follows ... 

The reactor auxiliary building directly adjoins the reactor building. It accommodates the facilities for helium purification and for the treatment and storage of radioactive waste, the ventilation systems, the store for new fuel elements, the sanitary rooms and other rooms such as laboratories. The central, monitored entrance to the reactor building is through the reactor auxiliary building. 

In the reactor building and reactor auxiliary building of the modular HTR power plant, all rooms are accessible during normal operation, with the exception of the primary cavity. Treated outside air is fed into the rooms to remove the dissipated heat and to retain the necessary quality of air in the rooms. The desired subpressure is maintained by regulating the supply of air flow while keeping constant the exhaust air quantity for each module and the service area. During normal operation the vented air is released unfiltered to the environment via the vent stack. 

If, as the result of leakages in components containing primary coolant, gas-bome radioactivity is released into the reactor building or the reactor auxiliary building, the facility is automatically switched over to the subpressure maintenance system with its activated carbon and aerosol filters. It has to be noted that these action are not necessary in order to meet allowable dose limits, but they are carried out as a matter of precaution due to the principle of minimization. 

The design of the reactor auxiliary facilities, machines and electric systems has at least reached the status of system and process engineering. As the final design step, the remaining structural and mechanical engineering is to be done. 

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... 

The SSWS cools the Component Cooling Water System (CCWS) through the Component Cooling Water Heat Exchangers and rejects the heat to the ultimate heat sink during normal, transient, and accident conditions. The CCWS in turn provides cooling water to those safety-related components necessary to achieve a safe reactor shutdown, as well as to various non-safety reactor auxiliary components. 

Because the reactor is basically a water boiler, process systems are required which clean and control the chemistry of the water in the reactor vessel as well as protect the reactor core. Called the reactor auxiliary systems, these systems may be divided into two general... 

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