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The fuelcompany develops and manufactures fuel for the entire RosatomVVER fleet including the VVER440, VVER1000 and VVER1200reactors. Each fuel assembly must be tailored to the dimensions ofthe respective reactor model and the operational need. Modern fuelassemblies have increased technical and economical characteristicsin accordance with new reactor designs and fuel cycles such as fuelcycle length, power output of the reactor, operational modes andanticipated fuel burnup.VVERs utilize enriched sintered UO2 fuel pellets fitted into fuelrods made from zirconium-alloy cladding.

These fuel rods arebundled together into hexagonal-shaped fuel assemblies havingan enrichment of up to 4.95 wt% U235. Burnable neutron poisons(gadolinium oxide) can be used to control the excess reactivity offresh fuel loaded into the reactor. Spacer grids, anti-vibration gridsand anti-debris filters are all used in the recent design to facilitatefunctions key to the stability and safety of the fuel, including optimalfluid flow, sufficient heat removal and mechanical stability duringoperation. Slight modifications are introduced into the design ofPWR fuel assemblies to facilitate 3, 4, or 5 years of fuel life.Hexagonal VVER fuel assemblies.

[4] [5]VVER1000VVER1200VVER1500Fuel cycle length (mos)1812-1812-24Avg. reload enrichment(wt%)4.45%4.79%4.92%Avg. BU (GWd/t)536057.2Avg. core height (m)3.533.754.2Core diameter (m)3.163.163.85Avg. core powerdensity (MW/m3)108108.5-Avg. fuel powerdensity (KW/kgU)35.836.8-OperationA total of 67 VVER reactors have been constructed in variouscountries since the 1960s starting with Russia during the Sovietera.

Their cumulative operation time exceeds 1200 reactor years.The experience gained from operating VVERS over the yearshas benefited Rosatom to improve their designs and increasingoperational efficiency. The design lifetime of older VVER modelswere 30 years, but through continuous improvements in materialand operational practices, the new generation of advanced reactormodels (VVER1000-, VVER1200- and VVER1500-series) arepredicted to serve for 50 or 60 years.A number of VVER units have surpassed their intended design lifeof 30 years and are still under operation.

Through implementingof plant life management programmes, operating licences havebeen renewed/extended in various countries. Several units havegone through safety upgrade processes, fitting the plants with thelatest set of requirements mandated by regulators.VVER Control RoomNovovoronezh NPP, Russia [6]17.

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