Fuel for RMBK-1000 and RBMK-1500 reactor being one of the highest power reactors in the world is manufactured and delivered in the form of fuel assemblies. Fuel assemblies are designed for thermal energy production and transfer to the coolant flow in the core.
The RBMK-1000 core is made up of 1693 channel tubes loaded with fuel assemblies, the core of RBMK-1500 contains 1661 channel tubes. Fuel assemblies remain fixed during in-reactor operation. Nuclear reaction, power level, transition from one power level to another one as well as reactor shutdown are controlled via vertical movement of reactor controls in the core.
Two types of FA are used in RBMK-1000 and –1500 core, viz. working FA and FA for gamma-chamber insertion. These types are characterized by a few design differences.
The design of RBMK-1000 and –1500 fuel assemblies with integrated burnable absorber and spacer grids made of zirconium alloys provide for geometrical stability at burn-up of 30-35 MW day/kgU and assures safety and high performance indicators of RBMK reactor cores. As a rule, RMBK-1000 fuel assemblies contain recycled fuel.
An RBMK-1000 FA contains two fuel rod bundles, two nozzles, a central bar with a mast (working FA) or a hollow support tube (FA for gamma-chamber insertion) to be used for placing the sensors; fastening and supporting components.
Upper and lower fuel rod bundles are interconnected by means of a central bar with a mast (working FA) or via support tube and fastening components. Overall length of RBMK FA is 10 meters with fuel length coming to 7 meters, cross-section profile is a circle with the diameter of 79 mm. FA weight is 185 kg. RBMK fuel assemblies have no shrouds.
Fuel rod bundle is made up of 18 fuel rods, skeleton with spacer grids and 18 ferrules to be used for fuel rod fastening in the lower FA lattice.
Fuel rods are tubes made of zirconium alloy and filled with sintered uranium dioxide pellets with the addition of erbium oxide, sealed by end-plugs through welding. The lower end of the rod is fastened to the lower lattice, the upper rod end remains unfixed. Application of fuel rods with integrated burnable absorber has resulted in the improvement of power density distribution in the reactor and enhancement of safety and performance indicators of RBMK reactor cores.
The design of RMBK-1500 FA is similar to the one of RMBK-1000. The difference of RMBK-1500 FA consists in the presence of 18 heat exchange intensifiers positioned in the upper bundle with the purpose of optimizing heat removal from fuel rods and turbulizing coolant flow.
Key technical characteristics
Number of fuel channels, pcs.
Steam characteristics before the turbine:
- pressure, MPa
- Temperature ,°С
- at the core inlet
- at the core outlet
Water flow through the reactor, t/h
Max. power of the fuel channel with fuel assembly, MW
Service time, years
- length, mm
- diameter, mm
FA weight, kg
U-235 enrichment depending on design modification,%
Average fuel burn-up depending on enrichment, MW d/kg U
Max. fuel burn-up depending on enrichment, MW d/kg U