Shutdown cooling system

Prevent containment ova-pressure Residual heat removal system Shutdown cooling system Containment spray system... 

Safety Perhaps superior, i) PCU and process heat loop have no role in heat removal safety systems. Safety system heat removal provided by shutdown cooling system and reactor cavity cooling system, ii) Rate of transport of tritium to chemical plant is reduced. 

When the reactor is shut down for maintenance or refueling, decay heat can be removed from the core by the normal Heat Transport System (HTS) described above, or alternatively by an independent Shutdown Cooling System (SCS). The SCS consists of a motor-driven circulator coupled with a water-cooled heat exchanger mounted beneath the reactor core within the reactor vessel. The SCS is provided for investment protection and flexibility of operation. The SCS and HTS are not "safety-related". 

SHUTDOWN COOLING SYSTEM Shutdown Cooling Circulator Compressor/Motor Assembly Ducting and Shutoff Valve Assembly Service Module Motor Power Supply Shutdown Cooling Heat Exchanger Tube Bundle Assembly... 

In the shutdown mode, the reactor vessel is fully pressurized or, at different times, in various stages of depressurization. Afterheat from fission product decay is generated at rates of up to about 7 percent of the core power level prior to shutdown, depending on the time interval since shutdown. The core decay heat is removed by the HTS. When the HTS is not available, the heat is removed by the Shutdown Cooling System (SCS). The outer control rods are normally fully Inserted during shutdown, and meet the required shutdown margin, with due allowances for uncertainties, even if the maximvim reactivity worth rod remains fully withdrawn. For cold shutdown, the control rods in the inner reflector are also Inserted and for this case, the maximum reactivity worth control rod is in the inner reflector. The neutron flux level is continuously monitored by the source range detectors. 

DBE-2 is a Heat Transport System (HTS) transient without control rod trip, requiring reactor shutdown with the reserve shutdown control equipment (RSCE), and core cooling with the Shutdown Cooling System (SCS). During the first 5 minutes of the event the core temperatures rise by a maximum of about 80 C (150°F) above the normal operating levels. After this initial phase, the core gradually cools down. 

Accompany with the RVCS, a shutdown cooling system(SCS) is proposed in the paper to provide a simple and reliable decay heat removal during normal shutdown period. The system is shown in Fig 3. It consists of an auxiliary blower, a cooler as well as a recuperator. Because the cooler and recuperator are also the parts of the RPV cooling system(RVCS), SCS is simple and its equipments have multi-function. The decay heat removal under the accidental conditions is depends on the passive reactor cavity cooling system. The SCS proposed in this paper therefore is not safety concerned. 

Shutdown Cooling System Failure Modes and Effects Analysis... 

Shutdown Cooling System Flow Diagram, Shutdown Cooling Mode... 

Other reactor coolant system penetrations are the pressurizer surge line in one hot leg the four direct vessel injection nozzles for the safety injection system two return nozzles to the shutdown cooling system, one in each hot leg two pressurizer spray nozzles vent and drain connections and sample and instrument connections. 

The Shutdown Cooling System (SCS) is a closed system without an accumulator (tank). Leakage from the RCS to SCS under normal operation, when the system is isolated from the RCS, would be detected by SCS pressure, and alarmed at a pressure less than the design pressure. If design pressure is reached the safety valves will open and the water will flow to the Equipment Drain Tank (EDT), where the change in level will be utilized to quantify the leak. 

The Shutdown Cooling System (SCS) is used in conjunction with the Main Steam and Main or Emergency Feedwater Systems (see Sections... 

H. The components of the shutdown cooling system are designed in accordance with the applicable codes and classifications discussed in Section 5.4.7.2.4. 

SHUTDOWN COOLING SYSTEM FAILURE MODES AND EFFECTS ANALYSIS... 

SHUTDOWN COOLING SYSTEM FLOW DIAGRAM SHUTDOWN COOLING MODE... 

Electrical building - houses the two non-safety-related standby diesel generators and their associated auxiliary equipment, and the solid-state adjustable speed drive units powering the feedwater pump motors and others powering the Reactor Water Cleanup/Shutdown Cooling System pumps. 

The CANDU 3 nuclear steam supply system includes the reactor, the heat transport system, the moderator system, the shutdown cooling system, the fuel handling system and associated control and service systems located within the reactor building (Figure 5.8.1 A) and the emergency core cooling system. The followng sections provide detail on specific NSSS system. 

The shutdown cooling system utilizing pumps and heat exchangers, can remove decay heat should the steam generator sink be lost. This system can be brought into service at fuel heat transport system temperature and pressure. 

Decay heat removal 1 Shutdown cooling system System 1 is used on a primary loop without a break... 

Water recirculation and heat removal Without LOCA Shutdown Cooling System or thermosyphoning through the steam generators. With LOCA ECC... 

In the case of small breaks in the PHT system (small LOCA), the ECCS system serves to recover the spilled water and transfer it back to the PHT system after cooling it to ambient temperature. A separate heavy water inventory is also provided for making up losses from Ae PHT system. In this situation where PHT system inventory of heavy water is maintained, the core cooling ftmction is carried out by the shutdown cooling system. 

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