Patent Number: 
Section: claims

1. A fuel element for a nuclear reactor, formed from coated fissile particles embedded in a matrix, comprising: a monolithic member formed of a single piece including:  plural parallel plates separated by spaces; and  junction parts configured to connect said parallel plates,  wherein the matrix is inert to heavy nuclei, fissile and fertile, and neutral to a coolant fluid that circulates in the spaces. 2. The fuel element according to  claim 1 , wherein the fuel element has a parallelepiped-like shape. claim 1 3. The fuel element according to  claim 1 , wherein the plates are approximately plane. claim 1 4. The fuel element according to  claim 1 , wherein the plates are approximately vertical and one of the spaces is configured to contain a control device. claim 1 5. The fuel element according to  claim 4 , wherein the junction parts and the parallel plates are perforated at predetermined levels to form windows through which the coolant fluid can circulate. claim 4 6. The fuel element according to  claim 4 , wherein the space in which the control device is configured to be contained has a horizontal cross-section in a shape of a cross, and the space divides the fuel element in four sub-assemblies each comprising plural plates connected to each other by some of the junction parts, others of the junction parts connecting the sub-assemblies to each other. claim 4 7. The fuel element according to  claim 6 , wherein the plates of contiguous sub-assemblies are perpendicular to each other. claim 6 8. The fuel element according to  claim 6 , wherein the plates of the four sub-assemblies are parallel to each other. claim 6 9. The fuel element according to  claim 1 , wherein the plates and spaces have thicknesses and widths with a ratio suitable for defining a fast spectrum for the coolant fluid. claim 1 10. The fuel element according to  claim 9 , wherein the ratio is approximately equal to 1 when water is used as the coolant fluid. claim 9 11. The fuel element according to  claim 1 , wherein the fuel element is protected by a metal duct. claim 1 12. The fuel element according to  claim 1 , wherein the fuel material particles comprise fissile particles chosen from the group comprising uranium and plutonium. claim 1 13. The fuel element according to  claim 1 , wherein the inert matrix is made from a material chosen from the group comprising silicon carbide SiC, a metal, and a combination of the two. claim 1