KudamKuklam Nuclear Power Reactor is a VVER-1000 type of Reactor imported from Russia. It is water-cooled and moderated pressure vessel type reactor. VVER-100 uses enriched uranium-di-oxide (Enrichment ranging from 1.6% to 4.1%) as nuclear fuel.The Reactor core Composition:
No of Fuel assemblies :163 hexagonally arranged.
The weight of a Fuel assembly: 705 kg.Mass of fuel in an Assembly: 490 kg
The incore residence of fuel assembly :5 years.
The Fuel Assembly:
The fuel rod in an assembly consisting of an upper plug, a spring clamp and a stack of fuel pellets inside a clad and a lower plug. The clad and end pieces of fuel rod are made of zirconium and 1% neobium alloy. The clad is a free standing one with a thickness of 0.685 mm. The fuel pellets are made of sintered uranium dioxide powder with a central hole of diameter 1.5 mm . The edges of the pellets are chamfered to reduce pellet clad interaction and chipping in the course of operation. The fuel rod has a plenum for collecting fission product gases. The plenum is pressurised with helium up to 2 MPa to prevent cladding collapse during operation. The fuel assembly has a cap and a tailpiece.
Fuel Assembly consists of 331 tubes following is the breakup:
Fuel Rods per Fuel Assembly : 311 fuel pins.
Absorber rods: 18 / assembly( for control and protection / for flux flattening)
In incore instrumentation detectors (ICID): 1 position/assembly
Slotted central tube : 1.
These are held by a framework of 15 hexagonal spacing grids and a supporting tail grid.
The fuel assembly design has been modified from V320 serial design of earlier VVERs. The advanced fuel assembly for KK VVER has the following improvements introduced:
• Usage of zirconium and 1% niobium alloy for guiding channel and spacing grid instead of stainless steel.
• Damping the absorber rods drop by 16 springs in the fuel assembly cap.
• Increase of outside diameter and thickness of the guiding channel wall.
• Optimisation of the diameters of the input holes in the guiding channel tip in order to improve the hydrodynamics of the absorbers drop.
• Usage of thrust sleeves that limit the spacing grid displacement along the central tube and guiding channel.
• Possibility of installation of the uranium-gadolinium fuel rods without changing the fuel assembly design.
• Additional clearance provided between absorber rods and guide tubes in fuel assembly. Increase in the weight of absorbing element (15% increase) and reduction of spring stiffness of the fuel assembly cap. These measures have helped in stabilizing the absorber rods drop time to 2 sec.
• Further advancements are being investigated for load following capabilities of fuel.
The KK VVER is a modernised version of the early V320 version reactors. It has the following modifications:
• The number of control and protection rods has been increased from 61 to 103 and a possibility of increasing to 121 rods if gadolinium can be used as burnable absorber.
• Increased efficiency of reactor shutdown capability and maintaining the reactor in sub-critical state without addition of boron in coolant even up to 200 C for an equilibrium core.
KK VVER fuel cycle has been developed making use of fuel assemblies of varying enrichment of U-235.
The first fuel loading consists of fuel assemblies of enrichments 1.6%, 2.4% and 3.6%. The average U-235 enrichment in the first loading is 2.45%. The nominal fuel loading in the reactor is about 80 tonnes. The general pattern for fuel arrangement is as follows:
• Fuel of higher enrichment is loaded in the core periphery and fuel of lower and intermediate enrichment are loaded in the central zones. Such arrangement ensures complete utilization of fuel and flattening of power distribution.
• Burnable poison rods serve for flattening the power distribution within core and for reducing the boric acid concentration at the beginning of fuel loading.
• Usage of zirconium and 1% niobium alloy for guiding channel and spacing grid instead of stainless steel.
• Damping the absorber rods drop by 16 springs in the fuel assembly cap.
• Increase of outside diameter and thickness of the guiding channel wall.
• Optimisation of the diameters of the input holes in the guiding channel tip in order to improve the hydrodynamics of the absorbers drop.
• Usage of thrust sleeves that limit the spacing grid displacement along the central tube and guiding channel.
• Possibility of installation of the uranium-gadolinium fuel rods without changing the fuel assembly design.
• Additional clearance provided between absorber rods and guide tubes in fuel assembly. Increase in the weight of absorbing element (15% increase) and reduction of spring stiffness of the fuel assembly cap. These measures have helped in stabilizing the absorber rods drop time to 2 sec.
• Further advancements are being investigated for load following capabilities of fuel.
The KK VVER is a modernised version of the early V320 version reactors. It has the following modifications:
• The number of control and protection rods has been increased from 61 to 103 and a possibility of increasing to 121 rods if gadolinium can be used as burnable absorber.
• Increased efficiency of reactor shutdown capability and maintaining the reactor in sub-critical state without addition of boron in coolant even up to 200 C for an equilibrium core.
KK VVER fuel cycle has been developed making use of fuel assemblies of varying enrichment of U-235.
The first fuel loading consists of fuel assemblies of enrichments 1.6%, 2.4% and 3.6%. The average U-235 enrichment in the first loading is 2.45%. The nominal fuel loading in the reactor is about 80 tonnes. The general pattern for fuel arrangement is as follows:
• Fuel of higher enrichment is loaded in the core periphery and fuel of lower and intermediate enrichment are loaded in the central zones. Such arrangement ensures complete utilization of fuel and flattening of power distribution.
• Burnable poison rods serve for flattening the power distribution within core and for reducing the boric acid concentration at the beginning of fuel loading.
Opeartional Features:
Nominal operation of reactor between 2 refuellings, called a cycle, is 297 full power days. It takes five cycles to reach equilibrium phase of the reactor at which the average incore enrichment, incore burn-up, reactivity coefficients and discharge burnup reach stable value. In the equilibrium phase of the reactor the following is the refuelling scheme:
• 48 or 49 no. of fresh fuel bundles are refuelled in every cycle.
• The annual fuel consumption is 35 tonnes of uranium.
• The enrichment of fuel assembly loaded are 3.62%, 12 or 13 in number, and 4.02%, 36 in number.
• The average discharge burnup of fuel unloaded during equilibrium condition is 43000 MWd/TeU.
• After irradiation in reactor for 3 to 4 years the burnt fuel are discharged to spent fuel pool and cooled there for a minimum period of 5 years.
• 18 burnt fuel assemblies during their 4th year of operation are reshuffled to the core periphery. Such mode of irradiation helps in reducing the fast neutron influence to the reactor vessel and increase the effectiveness of shutdown system.
• The fuel consumption cost is about 10% of unit energy cost.
The average discharge burn-up of fuel unloaded during equilibrium condition is 43000 MWd/TeU. After irradiation in reactor for 3 to 4 years the burnt fuel are discharged to spent fuel pool and cooled there for a minimum period of 5 years. The fuel consumption cost is about 10% of unit energy cost.
Nominal operation of reactor between 2 refuellings, called a cycle, is 297 full power days. It takes five cycles to reach equilibrium phase of the reactor at which the average incore enrichment, incore burn-up, reactivity coefficients and discharge burnup reach stable value. In the equilibrium phase of the reactor the following is the refuelling scheme:
• 48 or 49 no. of fresh fuel bundles are refuelled in every cycle.
• The annual fuel consumption is 35 tonnes of uranium.
• The enrichment of fuel assembly loaded are 3.62%, 12 or 13 in number, and 4.02%, 36 in number.
• The average discharge burnup of fuel unloaded during equilibrium condition is 43000 MWd/TeU.
• After irradiation in reactor for 3 to 4 years the burnt fuel are discharged to spent fuel pool and cooled there for a minimum period of 5 years.
• 18 burnt fuel assemblies during their 4th year of operation are reshuffled to the core periphery. Such mode of irradiation helps in reducing the fast neutron influence to the reactor vessel and increase the effectiveness of shutdown system.
• The fuel consumption cost is about 10% of unit energy cost.
The average discharge burn-up of fuel unloaded during equilibrium condition is 43000 MWd/TeU. After irradiation in reactor for 3 to 4 years the burnt fuel are discharged to spent fuel pool and cooled there for a minimum period of 5 years. The fuel consumption cost is about 10% of unit energy cost.
