FUEL ASSEMBLY AND CORE OF WATER-COOLED NUCLEAR REACTOR Russian patent published in 2003 - IPC

FIELD: nuclear power engineering and technology. SUBSTANCE: fuel assembly of water-cooled power reactor, primarily of type VVER-1000, has hexagonal-section fuel element bundle in framework incorporating cellular spacer grids, cells and rims, support grid, bottom nozzle, detachable top nozzle, central tube, and guide channels in the form of tubes accommodating control and protection rods and provided with tips on bottom end through which they are attached to carrier grid secured on bottom nozzle. Novelty is that ridges in the form of shaped and symmetrically rounded-off heat-transfer augmenting ribs are made on edges of spacer-grid rims between top and bottom nozzles of fuel assemblies which are tilted through certain angle in direction of fuel assembly axis. Ridges provide for coolant flow swirling and their projections onto horizontal plane do not overlap. Another novelty is that shaped ridge with symmetrically rounded-off rib is tilted to fuel assembly axis through angle smaller than 90 deg but greater than 0 deg. Ridges are disposed between top and bottom nozzles on each edge of spacer-grid rim at corners of conventional isosceles triangle with vortex facing bottom nozzle and at points of intersection of triangle sides with transversal axes of spacer grids. Reactor core has bottom support grid with supporting members that carries vertically mounted fuel assemblies spaced apart on top by means of top bank of protective tubes with perforated ring; fuel assemblies have top and bottom nozzles as well as fuel bundle with fuel elements installed in spacer grids whose hexagonal rim has key-turn size smaller than space between supporting members by location clearance value. Still another novelty is that fuel assemblies are relatively locked within core in pointwise manner through their height with negative allowance by aligning mentioned shaped ridges on rim edges of one fuel assembly with those of opposing adjacent fuel assembly in the course of core assembling. Total height of aligned ridges equals location clearance value. Projection of aligned shaped ridges onto vertical plane is in the form of X and distance between top pairs of ridges on edges of fuel assembly rim is sufficient to easily pass bottom paired and single ridges on edges of adjacent abutting fuel assembly rims for movement of this assembly up or down. One more novelty is that projection of all aligned ridges through height of abutting fuel assemblies is represented as conventional isosceles triangle with its vortex facing fuel assembly bottom nozzle and ridges at its corners and at points of intersection of triangle sides with transversal axes of spacer grids. Such tight packing of fuel assemblies prevents their deformation. EFFECT: enhanced reliability and safety of reactor, augmented heat transfer, reduced variations in energy release within core. 5 cl, 9 dwg