Patent Number: 051125692
Section: claims

1. Intrinsic-safety nuclear reactor of the pressurized-water type comprising: a reactor vessel having a core and containing a hot column of a primary fluid,  a pressurized non-thermally insulated container surrounding the reactor vessel and defining therein a tank having a column of cold first neutron absorbing liquid,  pipes providing communication between said pressurized container and said vessel, and  means defining an enclosed pool, containing a second neutron absorbing liquid kept at atmospheric pressure,  said pressurized container being positioned in said pool and being completely submerged in said second neutron absorbing liquid contained therein.  a reactor vessel having a core and containing a hot column of a primary fluid,  a pressurized non-thermally insulated container surrounding the reactor vessel and defining therein a tank having a column of cold first neutron absorbing liquid,  a grid for supporting the core,  vertically extending channels passing through the grid,  each channel being provided with a lower converging portion, an upper diverging portion and a neck therebetween, to produce a Venturi-type effect on primary fluid passing through the channel,  a pipe extending from said neck of each channel and opening into said tank, and  means defining an enclosed pool containing a second neutron absorbing liquid kept at atmospheric pressure,  said pressurized container being positioned in said pool and being completely submerged in said second neutron absorbing liquid contained therein. 2. Intrinsic-safety nuclear reactor according to claim 1, further comprising a pressurizer, connection means for hydraulic connection of said pressurizer with said tank, said pressurizer and said connection means being completely submerged in said second neutron absorbing liquid of said pool. 3. Intrinsic-safety nuclear reactor according to claim 2, wherein said connection means comprises two non-thermally insulated conduits, both submerged in said second neutron absorbing liquid of said pool and extending between said pressurizer and said tank at vertically separated levels capable of allowing natural circulation of said first neutron absorbing liquid contained in said tank to and from the pressurizer. 4. Intrinsic-safety nuclear reactor according to claim 2, wherein said pressurizer has a vertically elongated shape defining a hot upper area and a cold lower area, a funnel-shaped wall for separating said hot upper area from said cold lower area, said funnel-shaped wall having a lower part extending downwards towards said cold lower area to allow mixing and cooling of a hot portion of said first neutron absorbing liquid present in the upper area with a cold portion of said first neutron absorbing liquid present in the lower area in the event of a drop in the level of an interface between the hot and cold portions of said first neutron absorbing liquid inside the pressurizer. 5. Intrinsic-safety nuclear reactor according to claim 1, wherein said reactor vessel has an elongated cup-shaped structure removably connected to a top edge of the reactor vessel and axially extending inside the vessel towards the core; whereby the volume for primary fluid inside the vessel is reduced. 6. Intrinsic-safety nuclear reactor of the pressurized type comprising: 7. Intrinsic-safety nuclear reactor according to claim 6, further comprising a pressurizer, connection means for hydraulic connection of said pressurizer with said tank, said pressurizer and said connection means being completely submerged in said second neutron absorbing liquid of said pool. 8. Intrinsic-safety nuclear reactor according to claim 7, wherein said connection means comprises two non-thermally insulated conduits, both submerged in said second neutron absorbing liquid of said pool and extending between said pressurizer and said tank at vertically separated levels capable of allowing natural circulation of said first neutron absorbing liquid contained in said tank to and from the pressurizer. 9. Intrinsic-safety nuclear reactor according to claim 7, wherein said pressurizer has a vertically elongated shape defining a hot upper area and a cold lower area, a funnel-shaped wall for separating said hot upper area from said cold lower area, said funnel-shaped wall having a lower part extending downwards towards said cold lower area, so as to allow mixing and cooling of a hot portion of said first neutron absorbing liquid present in the upper area with a cold portion of said first neutron absorbing liquid present in the lower area in the event of a drop in level of an interface between the hot and cold portions of said first neutron absorbing liquids inside the pressurizer. 10. Intrinsic-safety nuclear reactor according to claim 6, wherein said reactor vessel is provided with an elongated cup-shaped structure removably connected to a top edge of said reactor vessel and axially extending inside the vessel towards the core, whereby the volume for primary fluid inside the vessel is reduced.