Flow calming assembly for nuclear reactor, and associated reactor and method

A nuclear reactor comprising:

• a vessel;
• an enclosure situated in the vessel wherein a fluid circulates from the vessel to the enclosure at a bottom part of the vessel;
• and
• a flow calming assembly comprising an outer calming device, the outer calming device having openings for fluid passage, the outer calming device comprising an upper part and a lower part, the upper part comprising a flared or conical collar extending between an upper end and a lower end, the lower part having a shape presenting a symmetry along a main axis, the lower part extending from the lower end of the upper part.

A method for installing an outer calming device in a nuclear reactor comprising a vessel and an enclosure situated in the vessel, the nuclear reactor comprising a nuclear core located in the enclosure, a fluid circulating from the vessel to the enclosure at a bottom part of the vessel, the method comprising the following steps:

• emptying the vessel of internal structures and nuclear fuel assemblies;
• providing an outer calming device, the outer calming device having openings for fluid passage, the outer calming device comprising an upper part and a lower part, the upper part comprising a flared or conical collar extending between an upper end and a lower end, the lower part having a shape presenting a symmetry along a main axis, the lower part extending from the lower end of the upper part;
• lowering the outer calming device in the vessel;
• fastening the outer calming device inside the vessel;
• and
• reinstalling the internal structures and the nuclear fuel assemblies in the vessel.