Ultimate heat sink

Associated systems are systems that are essential for the RCS and connected systems, which are primarily those for transferring heat to the ultimate heat sink, such as  

The ultimate heat sink is normally a body of water, the groundwater or the atmosphere, to which medium some part of or aU residual heat is transferred in normal operation, anticipated operational occurrences or accident conditions. When water is the medium selected as the ultimate heat sink, the following attributes should be considered  

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Drought Excluded by assuming that there are multipie sources of the ultimate heat sink or that the ultimate heat sink is not affected by drought (e.g., cooling tower with adequately sized basin) Low lake Internal or river water Ultimate heat. sink is designed for at ii.-av. 30 days of operation... 

High summer temperature Ultimate heat sink is designed for at least 30 Jays of operation Toxic gas Site specific requires detaiU l llJdy... 

Most heat pipes are cylindrical in shape. However, they can be manufactured in a variety of shapes involving 90° bends, S-tum.s, or spirals. Iliey can also be made as a flat layer with a thickness of about 0.3 cm. Flat heat pipes are very suitable for cooling high-power-output (say, 50 W or greater) PCBs. In this case, flat heat pipes are attached directly to the back surface of the PCB, and they absorb and transfer the heat to the edge.s. Cooling fins are usually attached to (he condenser end of the heat pipe to improve its effectiveness and to eliminate a bottleneck in the path of heat flow from the components to the environment when the ultimate heat sink is the ambient air. 

Decay heat in fuel elements is assumed to be dissipated by means of heat conduction and radiation to the outside of the reactor pressure vessel, and then taken away to the ultimate heat sink by water cooling panels on the surface of the primary concrete cell. Therefore, no coolant flow through the reactor core would be necessary for the decay heat removal in loss of coolant flow or loss of pressure accidents. The maximum temperature of fuel in accidents shall be limited to 1 bOO C. 

When the main heat transfer system can not work normally, the ERHRS will automatically put into operation in ten minutes to remove reactor residual heat to ultimate heat sink (atmosphere). 

Heat Removal Systems and Ultimate Heat Sink. 

A system to provide heat removal capability for all safety class structures, systems, and components. This system should have the capability to remove the total heat-load during all normal conditions and AOEs and transfer this heat to the ultimate heat sink (described be Iow). 

AR318 1.27 Ultimate heat sink for nuclear power plants (for comment) (Rev.2, ML003739969) March... 

The safety function fuel cooling during transients and accidents)) is ensured by provision of sufficient coolant inventory, by coolant injection, sufficient heat transfer, by circulation of the coolant, and by provision of an ultimate heat sink. Depending on the type of transient/accident, a subset of these function or all of them may be required. Various passive systems and components are proposed in V-392 design to fulfill these functions. 

ATWS Loss of ultimate heat sink BDBA... 

Tables 7-10 present excess pressure values that are limits for the assured integrity of building structures. However, the ALS may lose its function of a safety barrier at a lower excess pressure due to opening of safety valves in the leaktight compartments, whereupon a radioactive release may occur at upper elevations of the reactor budding. The leaktight compartments and the air space of the PSP may suffer overpressure during a LOCA with failure of the PSP cooling system (loss of ultimate heat sink), when steam condensation in the pool water is less effective at water temperatures exceeding about 85°C. Therefore, either the maximum permissible water temperature (for example <85°C) or the operating pressure difference of the safety valves may be adopted as an acceptance criterion for the PSP.

The main factor determining the required response time for operator intervention is the thermal capacity of the ultimate heat sink, i.e., the volumetric water inventory of the pool. 

A key feature of LEADIR-PS, shared with the Modular High Temperature Gas-Cooled Reactor (MHTGR) under development by General Atomics, is that radionuclide releases are prevented by retention of the radionuclides within the fuel particles under all design basis events without operator action or the use of active systems. Thus, the control of radionuclide releases is achieved primarily by reliance on the inherent characteristics of the coolant, core materials, and fuel. Specifically, the geometry and size of the reactor core, its power density, coolant, and reactor vessel have been selected to allow for decay heat removal from the core to the ultimate heat sink through the natural processes of radiation, conduction and convection, while the negative temperature coefficients of the fuel and moderator assure reactor shutdown. 

The atmosphere is the ultimate heat sink for the AP600 reactor system. Computer calculations have shown that under design basis accident scenarios the containment steel structure would provide sufficient cooling to prevent exceeding the containment design pressure. In performing this function, the heat is transferred through the containment vessel to the... 

Passive Containment Cooling System X Safety related ultimate heat sink... 

Passive Containment Cooling System (PCCS) Passive Ultimate heat sink (atmosphere)... 

Intermediate circuit, tow pressine diflerence between pnm and sec circuits lunits consequences R Pmnary transient - moeased design margins R Secondary transients - increased design margms R Loss of electric sources - 3 channels, 2 independent off-site power. sources total loss oftlie cold source (Water) - Passive ultimate heat sink (air) i otal loss of the SO feedwater Not relevant... 

Self suffici uty (h) to complete coolmg Safety graded Yes Water recirculation and heat removal a Ultimate heat sink (cold source) b Mode of operation (active/passive) Passive... 

SERVICE WATER SYSTEMS CSA Class 6 These systems remov c heat from equipment including saictv related equipment and transfer this heat to the ultimate heat sink The sy stems are compnsed of a recirculated cooling water system (closed loq>) and a raw service water system (once-ihrough) connected to the ultimate heat sink... 

This is one of the engineered safety features provided to mitigate the consequences of Loss of Coolant Accident (LOCA) in the event of a break in Primary Heat Transport (PHT) system boundary. The ECCS is designed to provide enough coolant to the PHT system and to transport heat from the core to the ultimate heat sink in such a way as to ensure adequate core cooling during all phases of LOCA. 

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