Patent ID: 7929657
Filing Date: 2011-04-19
Classification: G21C,Y02E

Abstract:
1. A pressurised water nuclear reactor vessel comprising: an outer casing which comprises at least one cylindrical shell having a circular cross-section, with a vertical centre axis, and a dished bottom head which closes a lower end of the shell, a primary cooling fluid, in the casing, a core comprising a plurality of nuclear fuel assemblies, arranged inside the casing, a core support plate which is substantially perpendicular relative to the centre axis and which is arranged inside the casing beneath the core, a vessel bottom head space being delimited between the support plate and the dished bottom head, the support plate being perforated with holes for circulation of the primary cooling fluid which place the vessel bottom head space in communication with the core, means for channelling the primary cooling fluid from the inlet(s) as far as the vessel bottom head space, a calming device which is arranged beneath the support plate in the vessel bottom head space and which is capable of calming at least a portion of the primary cooling fluid conveyed by the channelling means before this fluid passes through the support plate, the calming device having, in directions perpendicular relative to the centre axis, dimensions of between 30% and 60% of the inner diameter of the shell, wherein the calming device comprises at least one calming plate which is substantially perpendicular relative to the centre axis, and a plurality of calming holes, the calming holes being provided in the calming plate and being capable of calming the primary cooling fluid by passing it through the calming holes and the calming plate and the calming holes have, along the centre axis, a height of between 15% and 40% of the maximum height of the vessel bottom head space, taken along this axis.