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 Water-moderated water-cooled VVER-1000 power reactor has been the results of the further evolution of pressurized water reactor design.
Nuclear fuel for VVER-1000 reactors is manufactured and delivered in the form of fuel assemblies designed for generation and transfer of thermal energy to the coolant flow (water) in VVER-1000 reactor core. The core of VVER-1000 reactor is loaded with 163 fuel assemblies, which remain fixed during in-pile operation. Nuclear reaction, reactor power maintenance and transition from one power level to another one are controlled via vertical movement of rod control cluster assemblies in the reactor core.
A Rod Control Cluster Assembly (RCCA) consists of 18 absorber rods.
In 1997 OAO MSZ commenced on the work related to the development and implementation of alternative VVER-1000 fuel assembly design, the fabrication of those assemblies started in 1998.
Compared to the standard VVER-1000 fuel assembly, the alternative VVER-1000 fuel assembly is characterized by an improved bundle design implemented via the application of stiffening angles. This fuel assembly offers the intermediate option between shroud-less fuel assemblies and those with shroud tubes.
An alternative VVER-1000 fuel assembly is composed of three main interconnected components, namely: top nozzle, central piece and bottom nozzle.
 Top nozzle is designed for coupling the fuel assembly with refueling mechanisms during FA loading and unloading. Bottom nozzle provides for the FA placement in the reactor as well as for the coolant circulation to cool down fuel rods.
The fuel bundle contained between top and bottom nozzles consists of fuel rods (U-Gd rods) and guide thimbles interconnected by means of spacer grids and support lattices. To enhance design rigidity and reduce fuel assembly bow during operation spacer grids and top nozzle with the support plate are interconnected through angle sections making a single whole skeleton.
Alternative VVER-1000 fuel assemblies are characterized by geometric stability at high fuel burn-ups and assure nuclear safety and high performance indicators of VVER-1000 cores with high burn-up level and fuel cycles of 4x1, 5x1, 3x1,5 years.
Fuel rods are cladding tubes made of zirconium alloy and filled with sintered uranium dioxide pellets (U-rods) or UO2 +Gd2O3 pellets (U-Gd rods) sealed with end-plugs by means of welding. Application of U-Gd rods allows to improve power density distribution along the fuel assembly and enhance core safety.
Fuel rods are manufactured in automated lines equipped with state-of-the art control and inspection devices guaranteeing high quality and safety of the manufactured product.
- Key technical characteristics
Characteristics of the core and alternative VVER-1000 fuel assembly |
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Fuel cycle (number of cycles, cycle length in years)
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4x1 |
5x1
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Reactor thermal power, MW
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3200
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3200
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Number of fuel assemblies in the core, pcs.
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163
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163
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Total uranium weight in the core, t
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71
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71
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Number of annually replaced fuel assemblies, pcs.
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42
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33
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Average enrichment of make-up fuel, %
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4,4
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4.8
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Average discharge fuel burn-up, MW d/rgU |
47
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58
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Water temperature at reactor inlet, "С
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290
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290
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Water temperature at reactor outlet, °С
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320
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320
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Water pressure in the reactor, MPa (kgf/cm2)
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15,7(159)
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15,7(159)
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Overall assembly length, mm
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4570
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4570
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Overall fuel assembly width
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234
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234
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Total fuel assembly weight, kg
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710
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710
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Nominal uranium weight in the fuel assembly, kg
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435
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435
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Number of fuel rods in the FA, pcs.
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306
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303
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Number of gadolinium fuel rods in the FA, pcs.
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6 |
9
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Uranium enrichment depending on design modification, %
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3,3-4.4
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3,3-5,0
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