Refueling water storage tank

LESF (Figure 3.4.5-5), exemplified for the large LOCA, is compared with SELF. Event tree headings are the refueling water storage tank (RWST) a passive component, an engineered safety system (SA-1) and four elements of the containment system. Other examples of the LESF method show human error in the event tree while the criteria for system success is usually in the tan It tree analysis. 

Thermal-Hydraulic Analysis must be extended to at least 24 hours into the accident. This study used calculations for feed-and-bleed operation with a charging pump, and with gravity teed from the refueling water storage tank (RWST),... 

The Westi te 4 1 oop group includes nine plants housed within ici ndenser containments. Ma lese plants havi refueling water storage tanks such that switchover to either is not needed du assumed n time or is significantly delayed. The RCPs are a We.slinghouse design. 

IRWST - In-containment refueling water storage tank. 

Equipment Hatches (2) 17. Refueling Water Storage Tank 27. Accumulators (2)... 

The in-conlainmeni refueling water storage tank provides 500,000 gallons (about 1900 cubic meters) of water with a gravity head above the core. This water inventory is sufficient to flood the containment above the level of the reactor core and provide decay heat removal by natural circulation. 

Fig. 37. Schematic representation of the in-containment passive safety injection system (PS1S). 1RWST = in-containment refueling water storage tank. PRHR-HX = passive residual heat removal heat exchanger. ADS = automatic depressurization system (four stages). (Westinghouse)...

The removal of core decay heat assuming the steam generated in the in-containment refuelling water storage tank (IRWST) is condensed on the containment vessel and returned by gravity into the IRWST. The PDHR should provide decay heat removal for at least 72 hours if no condensate is recovered. 

Refueling water storage tank allowed outage time change... 

The allowed outage time for the RefUeling Water Storage Tank (RWST) in a 2 loop nuclear power plant with pressurized water reactor is currently defined... 

Overpressure protection for the reactor coolant pressure boundary is provided by four spring-loaded ASME Code safety valves connected to the top of the pressurizer. These valves discharge to the in-containment refueling water storage tank, where the steam is released under water to be condensed and cooled. If the steam discharge exceeds the capacity of the in-containment refueling water storage tank, it is vented to the containment atmosphere. 

Each primary safety valve discharge line is designed to pass a maximum steam flow of 630,000 Ibm/hr from the safety valve to one of the main header lines in the Steam Relief System (Section 6.8.2.2.2). The safety valve discharge flow analysis includes the effects of steam flow and Rapid Depressurization Function flow which result in two-phase flow inthe Steam Relief System. The safety valve discharge lines collect into two headers which are routed from the pressurizer cubicle to the In-containment Refueling Water Storage Tank (IRWST). See Section 6.8 for a description of the IRWST. Each Steam Relief System discharge line will pass the maximum steam flow from two safety valves, 1,260,000 Ibm/hr (2 valves time 630,000 Ibm/hr). 

The location of the pressurizer safety valves is shown in Figure 5.1.2-3, They discharge to the In-Containment Refueling Water Storage Tank (IRWST). Figure 10.1-2 shows the location of the main steam safety valves. 

The In-containment Refueling Water Storage Tank (IRWST) is used e as the pressurizer relief tank. The design and description of this tank are given in Section 6.8. 

Alternatively, primary water may be diverted to an auxiliary heat exchanger. An example of this arrangement is in AP600 where there is a natural circulation loop to a heat exchanger in the in-containment refuelling water storage tank which is brought into operation automatically. The tank has capacity for 72 hours of residual heat removal. 

Relocating the refueling water storage tank into the containment thus restricting access and reducing the likelihood of sabotage. 

Two principal systems used to mitigate the effects of a 1/3CA are the safety injection system (SIS) [see CESSAR-DC, Section 6.3], and the containment spray system (CSS) [see CESSAR-DC, Section 6.5]. These systems utilize an In-containment Refueling Water Storage Tank (IRWST) as their source of water, which is the equivalent of the refueling water storage tank (RWST) and containment sump of a pre-ALWR plant. 

The System 80+ Standard Design has an in-containment refueling water storage tank (IRWST), as described in CESSAR-DC Section 6.8. The CSS draws water from the IRWST. When spray is initiated during a LOCA, spray water from the upper elevations drains through major openings such as hatches and stairwells to the holdup volume of the IRWST, where it is mixed with water spilled from the break. From the holdup volume, water overflows... 

The System 80+ Standard Design Incorporates four primary safety valves (see CESSAR-DC, Section 5.4.1.3). Valve discharge is headered and routed to the In-Containment Refueling Water Storage Tank. These valves are monitored by three methods which are described in CESSAR-DC, Sections 5.2.5.1.2.1 ... 

Low-level signals from the VCT initiate reactor makeup control or flow from the refueling water storage tank (RWST) as a backup. Makeup to the RCS can come from the sources listed below ... 

During the injection phase the two systems take suction from the refueling water storage tank (RWST) for the recirculation phase these two systems are realigned to take suction from the containment sumps. 

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