A steam separation system includes a standpipe configured to receive a gas-liquid two-phase flow stream and a diffuser configured to receive the gas-liquid two-phase flow stream from the standpipe. The diffuser includes a swirler configured to separate the gas-liquid two-phase flow stream. The swirler includes a plurality of swirler vanes and a straightener structure. The straightener structure includes a hub. The plurality of swirler vanes is mounted radially around the hub, and a straightener extends in an upward direction from the hub. The system also includes a separation barrel configured to receive the gas-liquid two-phase flow stream from the swirler. The separation barrel includes a rifled channel having orifices along an inner surface thereof. The plurality of swirler vanes is tuned with the rifled channel, such that an angle of each of the plurality of vanes corresponds to an angle of the rifled channel.

A passive natural circulation cooling system according to the present invention can comprise: a passive condensation tank formed to accommodate cooling water; and a condensate water recirculation device provided at the inner part or upper part of the passive condensation tank, and condensing the cooling water such that the cooling water circulates inside the passive condensation tank. The condense water recirculation device can include: a duct extending upwards from the upper part of the passive condensation tank; and a plurality of partition plates provided inside the passive condensation tank or the duct.

A passive natural circulation cooling system according to the present invention can comprise: a passive condensation tank formed to accommodate cooling water; and a condensate water recirculation device provided at the inner part or upper part of the passive condensation tank, and condensing the cooling water such that the cooling water circulates inside the passive condensation tank. The condense water recirculation device can include: a duct extending upwards from the upper part of the passive condensation tank; and a plurality of partition plates provided inside the passive condensation tank or the duct.

Nozzles mix coolant from different sources together in an outlet to prevent differences in coolant output. Different flow path configurations are useable in the nozzle, including a multiple-path configuration with flows from different sources jacketed or concentrically arranged around flows from other sources. Swirl vanes may be installed in the nozzle to impart mixing or filtering the fluid flow. Diffusers may be used to passively suction or accelerate flow and mixing the same like a jet pump. Nozzles can be combined with filtration systems like trap filters that capture debris based on a momentum difference between the denser debris and fluid. Filters can use magnetic, adhesive, or porous materials to capture debris without blocking a flow path. Filters can be disengaged, such as when clogged, such that coolant flows around the system. Nozzles can be installed on feedwater sparger assemblies in varying manner to distribute coolant from multiple nozzles.

Nozzles mix coolant from different sources together in an outlet to prevent differences in coolant output. Different flow path configurations are useable in the nozzle, including a multiple-path configuration with flows from different sources jacketed or concentrically arranged around flows from other sources. Swirl vanes may be installed in the nozzle to impart mixing or filtering the fluid flow. Diffusers may be used to passively suction or accelerate flow and mixing the same like a jet pump. Nozzles can be combined with filtration systems like trap filters that capture debris based on a momentum difference between the denser debris and fluid. Filters can use magnetic, adhesive, or porous materials to capture debris without blocking a flow path. Filters can be disengaged, such as when clogged, such that coolant flows around the system. Nozzles can be installed on feedwater sparger assemblies in varying manner to distribute coolant from multiple nozzles.

A coolant recirculation system of a nuclear power plant is provided that may include: a reactor vessel configured to accommodate a reactor core and a reactor coolant therein; a steam generator configured to transfer a gas, converted from a liquid phase to a gaseous phase by exchanging heat with the reactor coolant, to a turbine system; a pressurizer configured to control pressure of the reactor coolant in the reactor vessel; a primary system pressure reducing valve located above the pressurizer and configured to open at a predetermined pressure to discharge the reactor coolant into a containment building for rapid depressurization; and a moisture separator connected to the primary system pressure reducing valve to separate moisture. The moisture separator may separate the reactor coolant into a gaseous phase and a liquid phase. Then, the liquid phase reactor coolant may be returned to the reactor vessel to be recirculated.

A coolant recirculation system of a nuclear power plant is provided that may include: a reactor vessel configured to accommodate a reactor core and a reactor coolant therein; a steam generator configured to transfer a gas, converted from a liquid phase to a gaseous phase by exchanging heat with the reactor coolant, to a turbine system; a pressurizer configured to control pressure of the reactor coolant in the reactor vessel; a primary system pressure reducing valve located above the pressurizer and configured to open at a predetermined pressure to discharge the reactor coolant into a containment building for rapid depressurization; and a moisture separator connected to the primary system pressure reducing valve to separate moisture. The moisture separator may separate the reactor coolant into a gaseous phase and a liquid phase. Then, the liquid phase reactor coolant may be returned to the reactor vessel to be recirculated.

A depressurisation valve for a coolant system; comprising a main chamber having a main valve, a pilot line, and a blowdown line having a secondary valve; the main valve being located to seal a coolant line of the coolant system. The main chamber being located downstream of the cooling system, the main chamber being filled with fluid from the coolant system via a pilot line, the pressure of fluid in the main chamber acts upon a piston head of the main valve and causes the main valve to open or close dependent upon the fluid pressure in the main chamber. Fluid can escape from the main chamber via the blowdown line, which has a variable fluid pressure depending upon an operating state of the secondary valve, and wherein the secondary valve is opened automatically dependent upon the conditions within the coolant system.

A depressurisation valve for a coolant system; comprising a main chamber having a main valve, a pilot line, and a blowdown line having a secondary valve; the main valve being located to seal a coolant line of the coolant system. The main chamber being located downstream of the cooling system, the main chamber being filled with fluid from the coolant system via a pilot line, the pressure of fluid in the main chamber acts upon a piston head of the main valve and causes the main valve to open or close dependent upon the fluid pressure in the main chamber. Fluid can escape from the main chamber via the blowdown line, which has a variable fluid pressure depending upon an operating state of the secondary valve, and wherein the secondary valve is opened automatically dependent upon the conditions within the coolant system.

According to at least some example embodiments, a dome collector separation stage includes an inner side wall that defines an inner channel; and an outer side wall that, together with the inner side wall, defines an outer channel, the inner channel being configured to receive a two-phase flow stream (FS) of water and steam, and pass the two-phase FS to the outer channel via inlets included in the inner side wall, the outer channel being configured to separate at least some water from the two-phase FS, and pass moisture-reduced steam out of the steam separator stage via outlets included in the outer side wall.