Fuel assembly for nuclear reactor, without casing, comprising a bundle of needles held laterally by grids and longitudinally by stiffening rods, passing through the grids.

Abstract

Fuel assembly for a nuclear reactor, of the Na-NFR type, without a casing, comprising a bundle of fuel needles held laterally by perforated grids and longitudinally by stiffening rods passing through the grids. The invention essentially consists of a fuel assembly (1) of hexagonal or parallelepiped cross-section without a hexagonal tube casing, preferably intended for low-power-volume liquid sodium-cooled fast reactors (Na-NFRs). Figure for the abstract: Fig. 5

Claims

3. Combustible assembly (1) according to claim 1 or 2, the head incorporating a longitudinal retaining plate perforated to allow the heat transfer fluid to pass through.

4. Combustible assembly (1) according to any one of the preceding claims, the stiffening rods being threaded at at least one of its longitudinal ends and being fixed by a plurality of screws or nuts, each forming a mechanical tie rod.

5. Fuel assembly (1) according to any one of the preceding claims, the retaining grids being arranged apart from each other by a distance d between 100 and 600mm.

6. Combustible assembly (1) according to any one of the preceding claims, the height h of a retaining grid along the longitudinal axis being between 50 and 100mm.

7. Combustible assembly (1) according to any one of the preceding claims, the cells (20) of the retaining grids incorporating on at least one of their inner walls, at least one flexible tab (21) forming a retaining spring for a needle against which it rests.

8. Combustible assembly (1) according to claim 6, each inner wall of a cell incorporating at least one flexible tab.

9. Combustible assembly according to claim 6 or 7, the flexible tab being shaped with its two ends formed integrally with the inner wall and forming a space with the latter.

10. Fuel assembly (1) according to any one of the preceding claims, the foot of the assembly comprising an outgrowth (134) forming an angular positioning key in the core of a nuclear reactor.

11. Use of a fuel assembly (1) according to any one of the preceding claims, in a liquid metal cooled nuclear reactor, in particular a liquid sodium cooled SFR-Na reactor, advantageously of low power volume, typically less than 200W / cm3. [Fig. 1] 110 [Fig. 2] [Fig. 2A] 11 1? 14 IH î J ';'w ................X [Fig. 5] 110 Z 100 [Fig. 10] 132 Fig. 10 [Fig. 11] -133 Fig. 13A [Fig. 14] 21 Fig. 14