The method of launching natural circulation of the liquid metal coolant in the heat sink circuit of the fast neutron nuclear reactor without connection to the main heat source (first circuit heat sink) and without using pumping equipment, but only as a result of electric heating of the downing and lifting sections of the heat sink circuit to the specified temperatures and, as a consequence, the occurring difference in the densities of the coolant on the lifting and downing sections of the heat sink circuit.

Pressure vessels have full penetrations that can be opened and closed with no separate valve piping or external valve. A projected volume from the vessel wall may house valve structures and flow path, and these structures may move with an external actuator. The flow path may extend both along and into the projected volume. Vessel walls may remain a minimum thickness even at the penetration, and any type of gates may be used with any degree of duplication. Penetrations may be formed by installing valve gates directly into the channel in the wall. The wall may be built outward into the projected volume by forging or welding additional pieces integrally machining the channel through the same volume and wall. Additional passages for gates and actuators may be machined into the projections as well. Pressure vessels may not require flanges at join points or material seams for penetration flow paths.

The invention relates to a flow calming assembly for a nuclear reactor comprising a vessel (2), an enclosure (5) located in the vessel (2), a fluid being circulated between the vessel (2) and the enclosure (5) in order to then circulate in the enclosure (5) after a reversal of its direction of circulation, a diffusion element (9) being configured to limit the formation of swirling flows in the enclosure (5) and make the distribution of the flow rates uniform over the cross-section of the enclosure (5), a diffusion element (9) and a flow calming method in such a reactor.

The invention relates to a flow calming assembly for a nuclear reactor comprising a vessel (2), an enclosure (5) located in the vessel (2), a fluid being circulated between the vessel (2) and the enclosure (5) in order to then circulate in the enclosure (5) after a reversal of its direction of circulation, a diffusion element (9) being configured to limit the formation of swirling flows in the enclosure (5) and make the distribution of the flow rates uniform over the cross-section of the enclosure (5), a diffusion element (9) and a flow calming method in such a reactor.

The invention relates to the field of nuclear engineering and can be used to organize the natural circulation of liquid metal coolant in the heat sink of a fast neutron nuclear reactor.

In order to create a driving pressure of circulation without using pumping equipment and to provide the required direction of natural circulation of the liquid metal coolant in the heat sink circuit of the fast neutron nuclear reactor in the absence of heat transfer from the reactor before filling the pipelines and equipment of the lifting and downing sections of the circuit, they are pre-heated by electric heating to temperatures T.sub.1 and T.sub.2, respectively, which are selected from the condition of inequality: .sub.1(T.sub.1).Math.g.Math.H.sub.1>.sub.2(T.sub.2).Math.g.Math.H.sub.2+P, where: .sub.1(T.sub.1) is the density of the liquid metal coolant at temperature Ti of pipelines and equipment in the lifting section;

.sub.2(T.sub.2) is the density of the liquid metal coolant at temperature T.sub.2 of pipelines and equipment at the downing section;
H.sub.1 is the height difference between the inlet and outlet of the lifting section;
H.sub.2 is the height difference between the inlet and outlet of the downing section;
.sub.P is the hydraulic resistance of the circuit; g is the acceleration of gravity. The circulation of the coolant in the circuit and the transition to natural circulation mode are carried out simultaneously until the nuclear reactor reaches its rated operating parameters by creating a moving pressure of the circulation due to the difference in densities .sub.1(T.sub.1) and .sub.2(T.sub.2) of the liquid metal coolant on the lifting and downing sections of the circuit, respectively.

The invention relates to the field of nuclear engineering and can be used to organize the natural circulation of liquid metal coolant in the heat sink of a fast neutron nuclear reactor.

In order to create a driving pressure of circulation without using pumping equipment and to provide the required direction of natural circulation of the liquid metal coolant in the heat sink circuit of the fast neutron nuclear reactor in the absence of heat transfer from the reactor before filling the pipelines and equipment of the lifting and downing sections of the circuit, they are pre-heated by electric heating to temperatures T.sub.1 and T.sub.2, respectively, which are selected from the condition of inequality: .sub.1(T.sub.1).Math.g.Math.H.sub.1>.sub.2(T.sub.2).Math.g.Math.H.sub.2+P, where: .sub.1(T.sub.1) is the density of the liquid metal coolant at temperature Ti of pipelines and equipment in the lifting section;

.sub.2(T.sub.2) is the density of the liquid metal coolant at temperature T.sub.2 of pipelines and equipment at the downing section;
H.sub.1 is the height difference between the inlet and outlet of the lifting section;
H.sub.2 is the height difference between the inlet and outlet of the downing section;
.sub.P is the hydraulic resistance of the circuit; g is the acceleration of gravity. The circulation of the coolant in the circuit and the transition to natural circulation mode are carried out simultaneously until the nuclear reactor reaches its rated operating parameters by creating a moving pressure of the circulation due to the difference in densities .sub.1(T.sub.1) and .sub.2(T.sub.2) of the liquid metal coolant on the lifting and downing sections of the circuit, respectively.

The present invention relates to a centering pin for a nuclear plant core, in a reactor vessel characterised in that it has a hydrodynamic profile (120, 130) on at least one of the front or downstream faces of the pin (110), so as to reduce instability when coolant fluid is circulating around the pin (110).

A flow distribution device (3) for a reactor, a lower internals (100) of a reactor and a reactor are provided. The lower internals (100) includes: a lower core support plate (2) defining a coolant hole therethrough; a flow distribution device (3) mounted on the lower core support plate (2) and including a distribution annular plate (8) and a distribution bottom plate (9); a vortex suppression plate (7) disposed below the distribution bottom plate (9); a support column (4) defining an upper end connected with the lower core support plate (2) and a lower end passing through the distribution bottom plate (9) to connect with the vortex suppression plate (7); an energy absorption device (5) defining an upper end connected with the vortex suppression plate (7); and an anti-break bottom plate (6) disposed on the lower end of the energy absorption device (5).

A riser cone has a lower end sized to engage a cylindrical lower riser section of a nuclear reactor and an upper end sized to engage a cylindrical upper riser section of the nuclear reactor. The riser cone defines a compression sealing ring that is compressed between the lower riser section and the upper riser section in the assembled nuclear reactor. In some embodiments the riser cone comprises: a lower element defining the lower end of the riser cone; an upper element defining the upper end of the riser cone; and a compliance spring compressed between the lower element and the upper element. In some embodiments the riser cone comprises a frustoconical compression sealing ring accommodating a reduced diameter of the upper riser section as compared with the diameter of the lower riser section.

A riser cone has a lower end sized to engage a cylindrical lower riser section of a nuclear reactor and an upper end sized to engage a cylindrical upper riser section of the nuclear reactor. The riser cone defines a compression sealing ring that is compressed between the lower riser section and the upper riser section in the assembled nuclear reactor. In some embodiments the riser cone comprises: a lower element defining the lower end of the riser cone; an upper element defining the upper end of the riser cone; and a compliance spring compressed between the lower element and the upper element. In some embodiments the riser cone comprises a frustoconical compression sealing ring accommodating a reduced diameter of the upper riser section as compared with the diameter of the lower riser section.