Summary Report for Conduct of Kozloduy NPP Stress Tests

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“Kozloduy NPP” PLC SUMMARY REPORT for Conduct of Kozloduy NPP Stress Tests supply system through a pair of channels. Water from Danube River is delivered to the cold channel by pumps, located in bank pump stations. Redundancy to connection to the Danube River is provided by Emergency pump station, which ensure independent water supply in emergency reserve of the cold channel through two independent pressure steel water lines. Water for cooling of turbine condensers and for cooling of consumers in nuclear facilities is delivered by circulation pumping stations with intake chambers and pumps, pressure steel pipelines and filtering premises with filtering units. Facilities for removal of heated water are the removal steel pipelines, siphon spillways shafts, low pressure removal channels, outlet shaft with the intake chamber and overflow, inlet and inspection shafts. For the needs of Kozloduy NPP totally 4 circulation pumping stations (CPS) were constructed: one per two shutdown pairs of units 1-2 and 3-4 (VVER-440) and one per each of two nuclear power units 5 and 6 (VVER-1000). CPS 3 and CPS 4 service the operating units, correspondingly unit 5 and unit 6. Two pumping station are identical. Each pump station has the following: · Motor-driven pumps for cooling of turbine condensers with water intake at elevation of 29 m; · Motor-driven pumps for service water supply to normal operation system consumers in the turbine hall, reactor compartment, auxiliary building and chemically demineralised water system with water intake at elevation of 28 m; · Motor-driven pumps for water supply to the spray pools with water intake at elevation of 28 m; · Diesel-pumps for water supply to the spray pools with water intake at elevation of 26.3 m, virtually from the bottom of the cold channel; · Fire-protection pumps with water intake at elevation of 26.3 m, virtually from the bottom of the cold channel. Series of the design measures have been implemented to prevent loss of connection to the Danube River – measures to prevent loss of the pumping stations, tools to prevent blocking of the main cooling water inlet, alternative ways of water supply, etc. Redundancy for removal of spent service water from NPP site (units 5 and 6) to the Danube River is provided with the second warm channel. For water supply to the spray pools of units 5 and 6, independent water supply is provided from the terrace of the Danube river, 6 shaft wells and 6 shaft pumping stations. Water amount which can be delivered from the shaft pumping stations to the spray pools is sufficient to replenish for losses from the six spray pools due to steaming and entrainment at quiet weather (wind speed of 2 m/s). Water from the shaft pumping station is delivered to the spray pools via separate steel pipeline. Cooling of the consumers of units 5 and 6 is provided from: 147/202
“Kozloduy NPP” PLC SUMMARY REPORT for Conduct of Kozloduy NPP Stress Tests · System for service water supply, intended for cooling of consumers of normal operation systems – ultimate heat sink is Danube river. · System for service water supply, intended to remove heat from equipment of the safety systems during all operational modes and emergency conditions. Each of the three trains of the system operate via the self-contained circuit, at this water cooling is provided in the spray pools. Ultimate heat sink is ambient air. During power operations of the nuclear power units the main ways to remove heat to the ultimate sink are as follows: · Through circulation water system – from the turbine condensers to the warm channel and via it – to the Danube river; · Through system for service water supply to consumers of normal operation systems – to the warm channel and via it – to the Danube river; · Through system for service water supply to consumers of the safety systems – to the spray pools and then – to ambient air. After the reactor is shut down, fuel decay heat in the core is removed in two stages: (1) through the secondary circuit, in steam water mode from the hot state to state at which it is possible to transfer to cooldown via emergency and planned cooldown system. circuit. (2) through the primary circuit via emergency and planned cooldown system on cooling Cooling of the safety system consumers is provided through the system for service water supply to safety system consumers to the atmosphere. Subcriticality is maintained by insertion of the control rods and by primary boric solution injection systems. At complete unavailability of the secondary circuit systems, reaching of the primary circuit parameters at which it is possible to transfer to operation of the cooling circuit, „feed-and-bleed” procedure may be applied. During cold condition, the main way to remove heat to the ultimate heat sink is through service water supply system of safety system consumers via the spray pools to the atmosphere. 5.1.3.2 Loss of main ultimate heat sink 5.1.3.2.1 Schemes and procedures on heat removal to alternative heat sinks At loss of access to the Danube river due to simultaneous loss of BPS and/or low-pressure channels and emergency pump station and its pipelines to the emergency volume, in these cases heat release from the core of each of the nuclear reactors 5 and 6 is provided via self-contained circuit through the service water supply system to the safety systems consumers through the spray pools to the atmosphere. 148/202
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Summary Report for Conduct of Kozloduy NPP Stress Tests

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