Insight of Safety Features at KKNPP
General information Under Operation, 20 Reactors, 4780 MW Under Construction, 6 Reactors, 4800 MW Proposed Projects Location: The Kudankulam is located on the coast of the Gulf of Mannar, at 25 km to the northeast from Kanyakumari,in Tamil Nadu State. Type: The Kudankulam Nuclear Power Projects are world s most advanced VVER-1000 reactors designed by Russian Engineers & Scientists. Experience: The design has been evolved from serial design of VVER 1000 reactors, of which 15 units are under operation for last 25 years. KKNPP: The VVER design adopted at Kudankulam has in additional many additional unique safety features.
GENERAL INFORMATION :KKNPPs 1000MWe. Coolant and moderator - Light water. Fuel -Enriched uranium (up to 3.92%) as fuel. Coolant Four loops Multi stateof-art reactor protection and safety systems to handle all the design basis and beyond design basis events.
Safety features 1. Inherent safety. 2. Multiple Safety barriers 3. Redundant safety trains 4. Passive safety systems. 5. Active safety Systems 6. Safety culture
INHERENT SAFETY FEATURES The VVER 1000 reactor chosen for Kudankulam is inherent safe having features Negative power coefficient: Wherein any increase in reactor power is self terminating. Negative Void Coefficient: reactor will shut down, if there is loss of water.
Safety Barriers Design safety incorporating defence-in-depth concept: Five barrier system in the way of ionising radiation preventing release of radioactivity in the environment FUEL MATRIX Prevent fission product release under fuel cladding FUEL CLADDING Prevent fission product release into primary (main circulation circuit) coolant MAIN CIRCULATION CIRCUIT Prevent fission product release into containment INNER & OUTER CONTAINMENT SYSTEM Prevent fission product release in the environment Five tiers of engineered features and administrative measures provided to protect these barriers.
REDUNDANT SAFETYF TRAINS: 4No. Four independent safety Trains even though one alone is sufficient for the 100% safety of the reactor. System shown in different four colours above are four independent train 7
ACTIVE SAFETY SYSTEMS Emergency reactor shutdown. Emergency boron injection. Containment spray. High pressure safety injection. Primary system emergency and planed cool down and fuel pool cooling. Primary circuit shut down cooling.
CONTAINMENT SYSTEMS Double Containment Buildings Primary Containment designed for LOCA peak pressure of 0.4MPa. Passive Hydrogen recombiners for combustible gas control inside the primary containment Containment spray system for pressure control. Secondary Containment designed for external effects, such as missile attack, aircraft crash & shock waves,
PASSIVE HEAT REMOVAL SYSTEM Drag shaft Drag shaft System ensures longterm removal of reactor core decay heat in absence of all power supplies Atmospheric air Atmospferic air LOSS OF POWER Steam generator Reactor Atmospheric air Atmospferic air
PASSIVE HYDROGEN RECOMBINERS PBLIC INTERACTIONS Passively recombins the hydrogen Thus maintains the volumetric hydrogen concentration in the mixture below the safe limits. Thereby avoid the formation of the explosive mixtures inside the containment.
PASSIVE 1 st & 2 nd Stage Hydro Accumulators 1 st Stage Hydro Accumulators Steam generator 2 nd Stage Hydro Accumulators 1 st Stage Hydroaccumulators ensures borated water supply to the reactor core in the event of loss of coolant RCP RCP 2 nd Stage Hydroaccumulators ensures long term flooding of reactor core with borated water at lower pressures. Reactor
QUICK BORON INJECTION (PASSIVE SYSTEM) System ensures reactor shut down Reactor Steam generator Injects high concentration borated water into primary coolant by inertial rotation of cooling pumps. LOSS OF POWER hffhff Quick acting valve ГЦН RCP Boric acid tank
PASSIVE ANNULUS SPACE DE-PRESSURIZING & FILTERING Atmospheric air Steam generator Reactor Atmospheric air System is intended for controlled removal of steamgas mix from the annulus in case of loss of all the power. Sys maintains vacuum and cleaning fluid in annular space. Inter-space kept at negative pressure to reduce releases significantly.
CORE CATCHER Confines molten core within the containment boundaries in the hypothetical event of melting of the reactor core.
Supply of water to core catcher from settling tanks located inside containment 1 reactor; 2 core catcher; 3 fuel pool; 4 monitor chamber for reactor internals; 5 pipeline of water supply to the surface of molten corium; 6 water supply pipeline from external source 6 5 4 1 2 3
SG EMERGENCY COOLDOWN SYSTEM Residual core heat removal during loss of power supply Reactor Steam generator Process condenser loss of heat removal through the secondary side. Pump
18 Provisions for withstanding external effects involving earthquake, tsunami/storm, tidal waves, cyclones, shock waves, fire and aircraft impact on main buildings
RELATIVE ELEVATIONS OF SEA & STRUCTURES AT KKNPP SWITCH YARD Design basis flood level + 5.44 (MSL) due to tidal variations, wave runup, storm surge / tsunami +5.44m PUMP HOUSE PUMP +7.65m TURBINE +8.1m REACTOR +8.7m DG 2 DG 4 DG 3 +9.3m +13m Tsunami of 26.12.2004 MEAN SEA LEVEL 170-70 30 130 230 330 430 530
PROTECTIONS AGAINST TSUNAMI AT KKNPP Kudankulam site is located far off (about 1500 km) from the tsunamigenic fault (where tsunamis originate). Thus, if there is a tsunami, it would take time and lose its energy by the time it strikes Kudankulam site. Where as against this, the tsunamigenic fault was only about 130 km away at Fukushima. 170-70
Food Levels of important facilities at KKNPP As compared to the Design Basis Flood Level of 5.44 meters, levels of important facilities at KKNPP wiih respect to -mean sea level are: Reactor Building ground floor 8.7m Safety diesel generator sets 9.3m Switch gear for safety trains 9.3m Group I battery bank 12.9m Station blackout battery 16.5m Control instruments for safety trains 16.5m Supplementary control room 9.7m
STATUS ON KUDANKULAM PROJECT Additional protection against flooding The supplementary control room and the four diesel generator - safety train rooms are provided with water tight doors to protect them against flooding. We should normally ensure that the doors remain shut when the reactors are operating by using interlocks or strict administrative procedures.
STATUS ON KUDANKULAM PROJECT With regard to earthquakes Strongest one occurred at Coimbatore on February 8, 1900. The India Meteorological Department estimated its magnitude at 6.0 on the Richter scale. The epicenter was little more than 300 km from Kudankulam. The nearest recorded was on August 25, 1856 near Trivandrum with an intensity estimated at 4.3 on the Richter scale. Based on these observations, the parameters chosen for design were: Peak Ground Acceleration in g Horizontal Vertical Design Basis - safe shutdown 0.15 0.11 Design Basis - operating 0.05 0.036 Automatic trip of the reactor is initiated at the vertical and horizontal acceleration levels chosen for the operating basis earthquake (namely 0.036 g vertical and 0.05 g horizontal)
STATUS ON KUDANKULAM PROJECT Grid connectivity Kudankulam is connected to the southern grid at Tirunelveli by double circuit 220 KV series and double circuit 400 KV lines. Tuticorin thermal power station is connected directly to Tirunelveli. There are a number of hydro power stations in Kerala and Tamil Nadu close to Kudankulam. We are having 10 MW of wind turbines in our site
STATUS ON KUDANKULAM PROJECT Decay Heat Removal For cooling of the core in a shut down condition, to remove the decay heat, four independent cooling trains, each with its own diesel generator set, are provided. There is a back up to this through hydro accumulators (in two stages). Normally, the decay heat gets transferred to the secondary side water. If the latter is not available for any reason. There is a passive heat removal system where by the secondary side water is cooled in air cooled heat exchangers. The latter are located at a considerable height on the outer containment to ensure natural circulation (i.e. it is a passive system requiring no pumps or no power driven equipment). This feature has been built into KKNPP design specifically at India's insistence.
STATUS ON KUDANKULAM PROJECT Safety for extreme situation There is a safety provision for an extreme situation of the fuel in the core melting and breaching the pressure vessel. In such a situation, the core catcher below the pressure vessel will ensure that the molten core mixes with a large quantity of neutron absorbing material and thus prevent the possibility of a nuclear explosion. Only the most modern designs have such a provision. There are 154 passive hydrogen recombines to prevent any explosive mixture forming in any zone of the primary containment.