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The pressurizer vessel itself may be maintained much hotter than the rest of the reactor plant to ensure pressure control, because in the liquid throughout the reactor plant, pressure applied at any point has an effect on the entire system, whereas the heat transfer is limited by ambient and other losses.
A reactor vessel head for a pressurized water reactor. This structure is attached to the top of the reactor vessel body. It contains penetrations to allow the control rod driving mechanism to attach to the control rods in the fuel assembly. The coolant level measurement probe also enters the vessel through the reactor vessel head.
The time required for the molten metal of the core to breach the primary pressure boundary (in light water reactors this is the pressure vessel; in CANDU and RBMK reactors this is the array of pressurized fuel channels; in PHWR reactors like Atucha I, it will be a double barrier of channels and the pressure vessel) will depend on temperatures ...
In the most severe of such scenarios, if the fuel remains insufficiently cooled for prolonged periods of time, the integrity of the primary system (second barrier) can be threatened as well, for example if a substantial mass of molten fuel reaches the bottom of the reactor pressure vessel and melts through it.
The High Pressure Coolant Injection (HPCI) System consists of a pump or pumps that have sufficient pressure to inject coolant into the reactor vessel while it is pressurized. It is designed to monitor the level of coolant in the reactor vessel and automatically inject coolant when the level drops below a threshold.
The force impinged on the lid of the reactor vessel, causing water and steam to spray from the top of the vessel. This extreme form of water hammer propelled top head shielding, remnants of fuel plates, five loose shield plugs, a nozzle flange, and the entire reactor vessel upwards. A later investigation concluded that the 26,000-pound (12,000 ...
Control rods are usually used in control rod assemblies (typically 20 rods for a commercial PWR assembly) and inserted into guide tubes within the fuel elements. Control rods often stand vertically within the core. In PWRs they are inserted from above, with the control rod drive mechanisms mounted on the reactor pressure vessel head. In BWRs ...
The GE Mark III Containment-system is a single barrier pressure containment and multi-barrier fission containment system, consisting of the containment vessel plus associated dry- and wetwell (pressure and fission barriers), the external shield building of it, the auxiliary building and the fuel building, all of which are normally kept at ...