Pressurized water reactors auxiliary flows

In this work, a Motor-Operated Valve (MOV) of the Auxiliary Feed Water System (AFWS) has been selected based on several arguments. First, the basic event representing MOV fails to remain open is one of the most important contributors to the CDF based on the standard PSA available. Second, equipment aging, preventive maintenance and surveillance requirements are meaningful for this MOV. This basic event is modelled as a standby-related failure. This valve is normally open and its function is to control the flow from AFWS until Steam Generators on the secondary of a typical Pressurized Water Reactor (PWR) NPP. 

In the process, 99.8 percent ethylene, 99.5 percent oxygen, and recycle gas are directed to a vertical reactor and are contacted with the catalyst solution under slight pressure. The water evaporated during the reaction absorbs the exothermic heat evolved, and make-up water is fed as necessary to maintain the catalytic solution concentration. The reacted gases are water-scrubbed and the resulting acetaldehyde solution is fed to a distillation column. The tail gas from the scrubber is recycled to the reactor. Inerts are eliminated from the recycle gas in a bleed stream which flows to an auxiliary reactor for additional ethylene conversion. 

The HPCS system can operate independently of normal auxiliary AC power, plant service air, or the emergency cooling water system. Operation of the system is automatically initiated from independent redundant signals indicating low reactor vessel water level or high pressure in the primary containment. The system also provides for remote-manual startup, operation, and shutdown. A testable check valve in the discharge line prevents backflow from the reactor pressure vessel when the reactor vessel pressure exceeds the HPCS system pressure such as may occur during initial activation of the system. A low flow bypass system is placed into operation until pump head exceeds the nuclear system pressure and permits flow into the reactor vessel. 

Flow proceeds from the lower plenum, through the core. The steam and water are separated the steam is then dried and passed to the turbine. Other flow (see above) returns to the recirculation system. Feedwater is introduced to the annulus between the core shroud and reactor vessel (Fig. 4). The recirculation system piping is a primary pressure boundary for the high-pressure, high-temperature reactor coolant. Type 304 stainless steel was selected for recirculation system piping and numerous other auxiliary systems (such as the reactor water cleanup system, residual heat removal system, core spray, and other emergency core cooling systems) for its corrosion resistance and adequate mechanical properties. Failures of weld heat affected zones... 

During reactor operation, the secondary system is operated as a steam condensate system to transfer heat removed from the primary loop to the circulating raw water system. Heat transfer from the primary loop results in boiling on the secondary side of the ten main heat exchangers. This steam then flows to the main 46 steam header atop the 109 Building. Sufficient steam to drive the six drive turbines and to supply auxiliary areas uses flows to the turbine supply header the remainder is condensed in the dump condensers, completing the heat transfer to the circulating raw water system. Secondary coolant pressures, flow rates and Inventory are directly controlled coolant temperatures are dependent variables. 

---