Containment Recirculation Cooling System

The containment recirculation cooling system controls building air temperature and humidity to provide a suitable environment for equipment operability during normal operation and shutdown. 

The containment recirculation cooling system is comprised of two 100 percent capacity skid mounted fen coil unit assemblies with a total of four 50 percent capacity fan coil units which connect to a common duct ring header and distribution system. 

The containment recirculation cooling system has no design requirements associated with safety. 

In open recirculating systems evaporation is the major factor in heat disposal. In these evaporative systems circulating water is continuously scrubbed with air, therefore saturated with dissolved oxygen. In contrast, water in closed recirculating cooling systems usually will contain minimum dissolved oxygen, even though the systems may include vented expansion tanks. 

Foulants enter a cooling system with makeup water, airborne contamination, process leaks, and corrosion. Most potential foulants enter with makeup water as particulate matter, such as clay, sdt, and iron oxides. Insoluble aluminum and iron hydroxides enter a system from makeup water pretreatment operations. Some well waters contain high levels of soluble ferrous iron that is later oxidized to ferric iron by dissolved oxygen in the recirculating cooling water. Because it is insoluble, the ferric iron precipitates. The steel corrosion process is also a source of ferrous iron and, consequendy, contributes to fouling. 

The reactor core, the source of nuclear heat, consists of fuel assemblies and control rods contained within the reactor vessel and cooled by the recirculating water system. A 1,220-MWe BWR/6 core consists of 732 fuel assemblies and 177 control rods, forming a core array 16 feet (4.8 meters) in diameter and 14 feet (4.2 meters) high. The power level is maintained or adjusted by positioning control rods up and down within the core. The BW R core power level is further adjustable by changing the recirculation flow rate without changing control rod position, a feature that contributes to excellent load-following capability. 

It is difficult to say precisely what the upper limit of tolerance to chloride ion is, as so much depends on the particular circumstances. Conservative operators will often only permit, typically, about 200 to 250 ppm Cl in the recirculating water, where the cooling system contains a particularly high percentage of stainless steels, or where there is concern over the vulnerability of the stainless steel (SS) components in the system. 

Some ozone suppliers recommend that the bypass loop be taken from and returned to the pressure side of the main recirculating pumps. A contact/degassing vessel is recommended to prevent air bubbles from entering the cooling system pipework. All sidestream pipework containing ozonated water should be of uPVC or stainless steel construction. 

Calibration of the GC should be carefully performed within the appropriate range of concentrations and pressures for each gas component. In the case of the flow reactor, the gas flow rates should be carefully calibrated before calibrating the GC itself. In the case of the recirculating reactor in vacuum, the volume of the system should be calibrated by using a vessel or a container with a known exact volume. To be strict, the temperature of the system should also be kept constant during and between each measurement. It is thus usefiil to utilize water baths or cooling systems to maintain constant temperatures during the PEC measurements, which are typically carried out at room temperature. 

Emergency core cooling system consists of two trains. Each train meets the single failure principle. System includes high and low pressure sub-system. High-pressxue subsystem includes passive (hydro-accumulators) and active pumps and water storage tanks) features for water injection in reactor. Low-pressure sub-system ensures returning a condense accumulated in containment, into the reactor by recirculation pumps. 

The vessel (1) contains the reactor core (2) in which the control rods can be inserted from above (3). The cooling system is formed by two circuits (in the figure only one is represented), each one provided with two recirculation pumps (4) and with one steam generator (5). The steam produced in the secondary side of the generator is routed to the turbine (6) and converted to water again in the condenser. The condensate returns to the steam generators through... 

Heat is deposited in the heavy water moderator contained within the calandria during normal operation, from direct gamma and neutron interaction and through thermal conduction from the fiiel channels. This heat is removed by the moderator cooling system, which circulates and cools the heavy water in an external circuit connected to the calandria the heat is rejected to the recirculated coolant water system. 

The Emergency Core Cooling System uses high pressure gas to inject ordinary water into the fuel channels, followed by pumped recirculation and cooling of water within the reactor building. The containment system includes the reactor building and the containment isolation system. 

The CSS is physically separated from the shutdown cooling system in that a dedicated containment spray pump and heat exchanger are provided in each CSS train. This feature and the IRWST eliminate the need to automatically realign the CSS as recommended by SRP Section 6.5.2 to accomplish long-term cooling, since the CSS short-term injection and long-term recirculation are accomplished with the same CSS line-up. 

Hydraulic Institute standards are used for the start up feed water and Passive Containment Cooling System (PCS) recirculation pumps... 

Additionally, a passive containment cooling ancillary water storage tank and two recirculation pumps are provided for onsite storage of additional passive containment cooling system cooling water, to transfer the inventory to the passive containment cooling water storage tank, and to provide a back-up supply to the fire protection system seismic standpipe system. 

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