Category Archives: Passive Safety Systems and Natural Circulation in Water Cooled Nuclear Power Plants

Thermo-fluid dynamics and pressure drops in various geometrical configurations

Pressure drop is the difference in pressure between two points of interest in a fluid system. In general, pressure drop can be caused by resistance to flow, changes in elevation, density, flow area and flow direction. Pressure drops in natural circulation systems play a vital role in their steady state, transient and stability performance.

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Sump natural circulation

Some designs utilize the reactor cavity and other lower containment compartments as a reservoir of coolant for core cooling in the event of a break in the primary system. As such, water lost from the reactor system is collected in the containment sump. Eventually the reactor is completely immersed in water and the isolation valves are opened. Decay heat removal […]

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Natural circulation in heat transport system

The HTS is laid out with the heat transport pumps and steam generators above the core to promote natural circulation of the primary coolant for accidents when the heat transport pumps are not operating (see Fig. II-4). This natural circulation flow allows the plant to recover from any trip without relying on the heat transport pumps. Commissioning tests have been […]

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Steam-liquid interactions

Large pools may have a very wide spectrum of geometric configurations. Heat transfer in one very limited zone in terms of volume (e. g. by condensing injected steam or by heat transfer from a passive containment cooler) does not imply homogeneous or nearly homogeneous temperature in the pool. Many containment phenomena require steam-liquid interface. Steam discharge into a suppression pool […]

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Natural circulation in Calandria vessel

In a CANDU reactor the fuel is contained within pressure tubes that run through a vessel called the Calandria. Low pressure and temperature heavy water contained in a Calandria vessel moderates nuclear fission. The pressure tubes are contained within another set of tubes called calandria tubes, separated from the pressure tubes by an annulus gap filled with carbon dioxide. This […]

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Containment passive heat removal/pressure suppression systems

This type of passive safety system uses an elevated pool as a heat sink. Steam vented in the containment will condense on the containment condenser tube surfaces to provide pressure suppression and containment cooling. Three variations of the concept are presented in Figures 10 to12. In the first variation of the concept, Figure 10, an air heat exchanger (HEX) is […]

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Gravity driven cooling and accumulator behaviour

Gravity driven cooling provides emergency core cooling water by gravity draining, in events with loss of coolant. This system requires a large volume of water above the core, plus additional depressurization capacity, so that the primary coolant system can be depressurized to allow for gravity flow from the elevated suppression pool. Since there are no large reactor vessel pipes at […]

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