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Flamanville 3 Safety analysis of Internal Hazards

Flamanville 3 Safety analysis of Internal Hazards. Summary. Internal hazards considered in FA3 design General rules for Internal Hazards Pipe rupture Internal Flooding Internal Missiles L oad drop. Internal Hazards. Internal hazards considered in FA3 design Pipe failure

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Flamanville 3 Safety analysis of Internal Hazards

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  1. Flamanville 3Safety analysis of Internal Hazards

  2. Summary • Internalhazardsconsidered in FA3 design • General rules for Internal Hazards • Pipe rupture • InternalFlooding • InternalMissiles • Load drop GP - Examen de la démarche de classement de sûreté du réacteur EPR de Flamanville - 29/04/2014

  3. Internal Hazards Internalhazardsconsidered in FA3 design Pipe failure Failure of tanks, pumps & valves Internal flooding Missiles Load drop Internal explosion Fire Not in the scope of PSN-SRDS/SSyR Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  4. General rules for Internal Hazards(1/3) Radiological consequences of internal hazards In accordance with the Technical Order INB167-6 the radiological consequences shall be at most equal to those of Plant Conditions of an equivalent frequency Design and installation rules internal hazards shall not prevent the completion of F11functions, even if they are generally not required for such an event internal hazards shall not cause a PCC3/PCC4 event internal hazards shall not impair the separation into divisions Nota 1 : F1 functions are functions required to lead the plant in a controlled or safe state after a Design Basis Event (PCC2 to PCC4) (Engineered Safety Features) Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  5. General rules for Internal Hazards(2/3) Therefore an internal hazard shall not damage : More than 1 redundancy of a F1 system The stability and/or integrity of : the Reactor Pressure Vessel the Reactor Pressure Vessel internals including the fuel elements the Main Steam and Feed Water lines the Fuel pool internals including the fuel elements the components the rupture of which is precluded the safety buildings Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  6. General rules for Internal Hazards(3/3) Moreover : In all cases a sufficient number of systems required to reach and maintain a safe state shall be available The control room shall be usable Specific rules Supplementary rules for : Pipe rupture Internal flooding The possible links between an Internal Hazard and a plant state are considered Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  7. Internal Hazards analysis methodology (1/3) Internal hazard independent from a PCC or RRC event All systems may be credited to reach and maintain a safe state A random single failure is postulated Internal hazard triggering a PCC21event The single failure postulated is the most challenging between the random single failure of the internal hazard and the Single Failure of the PCC2 Nota 1 : An internal hazard should not lead to a PCC3/PCC4 event. If it triggers such an event, it has to be demonstrated that the plant can be driven to a safe state Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  8. Internal Hazards analysis methodology (2/3) Internal hazard resulting from a PCC3/4 or a RCC-A1 event The analysis must verify that the systems necessary to cope with the event are not damaged in an unacceptable way by the internal hazard No random single failure is postulated if a SF is taken into account in the analysis of the PCC They are credited 30 mn after the first information in the MCR for actions from the MCR Nota 1 : a RRC-A situation is a Design Extension Condition (multiple failure, Station Blackout, Loss of the Cooling Chain) Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  9. Internal Hazards analysis methodology (3/3) Operator actions They are credited 30 mn after the first information in the MCR for actions from the MCR They are credited 1 h after the first information in the MCR for local actions Safety classification The functions specifically used to control internal hazards are F2 classified Nota 1 : a RRC-A situation is a Design Extension Condition (multiple failure, Station Blackout, Loss of the Cooling Chain) 2 Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  10. Pipe rupture (1/8) 2 kinds of pipe High energy pipes (P>20 bars OR T > 100°C OR gas pipe P > 1 bar) Else Medium energy pipes Failure assumption for high energy pipes Small pipes (D < 50 mm) : a break is postulated at any location Large pipes : a break is postulated : If the pipe is classified (component class Q1 to Q3), only in predefined location (ends, location where the strain is > some criteria). Moreover, a verification study (with realistic assumptions) is performed in other locations If the pipe is not classified, a break is postulated at any location The break is precluded for some pipes : Main Coolant lines, Main steam Lines Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  11. Pipe rupture (2/8) Failure assumption for medium energy pipes Small pipes (D < 50 mm) : a break is postulated at any location Large pipes : If the pipe is classified (component class Q1 to Q3), a leak (conventional area = e D / 4) is assumed in predefined locations (ends, location where the strain is > some criteria). If the pipe is not classified, a break is postulated at any location The leak is precluded for some pipes : Fuel Pools Treatment System lines, transfer tube Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014 14

  12. Pipe rupture (3/8) Effects of failures of pipes Local effects (High Energy pipes only) : Jet force effect on surrounding pipes and equipment Reaction forces on structures supporting the pipe Pressure waves and flow rate force on equipment of the failed pipe Pipe whip effect : The rupture of a HE pipe of diameter D0 and thickness e0 induces on an other pipe of diameter D and thickness e : a break if D < D0 a leak if D ≥ D0 AND e < e0 Loss of all electric equipment and wires in the room Global effects (High and Medium Energy pipes) : Degraded ambient conditions (pressure, temperature, humidity, radiation) in the buildings Flooding Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  13. Pipe rupture (4/8) Specific rules for pipe ruptures Additional requirements : A failure of a primary loop shall not induce a failure of another loop A failure of the primary circuit should not induce a failure of the secondary circuit (and vice-versa) A failure of a secondary line should not induce a depressurization of 2 SGs Simultaneous failure of the steam and water lines of a SG should be avoided Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  14. Pipe rupture (5/8) 1rst stage analysis of the consequences of HELB (1) Identification for each room of the most bounding HELB (rupture in any location) Identification of lost pipes : all classified pipes (Safety Class >= F2) of the room the diameter of which is lower than the HEL diameter Identification of lost equipment : all classified equipment (SC >= F2) of the room is lost Identification of detection and mitigation means Identification of components being able to detect and isolate the break (shall be F2 classified) Checking if those components are qualified for the environmental conditions due to the HELB and (if local operation) in accessible rooms Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  15. Pipe rupture (6/8) 1rst stage analysis of the consequences of HELB (2) Identification for each room of the lost redundancies of F1 functions Identification of F1 function for which > 1 redundancy is lost Analysis of the possibility to reach a safe state despite the consequences of the HELB, a single failure and a maintenance If impossible => Open point Identification of accidental transients If the transient is a PCC3 or PCC4 and could be avoided (caused by a break which is not a PCC3-4) => Open point Analysis of the possibility to reach a safe state despite the consequences of the HELB, a single failure and a maintenance If impossible to reach a safe state => Open point Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  16. Pipe rupture (7/8) 2nd stage analysis of the consequences of HELB In the rooms where the safety criteria are not matched in the 1rst stage study : a precise location of the break is defined calculation of the whipping and jet force effect determination of the equipment and pipes possibly damaged Functional analysis of the consequences of lost wires Taking into account of the global effects of the HLB Design of protection means Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  17. Pipe rupture (8/8) Analysis of the global consequences of HELB Propagation of degraded ambient conditions Identification in each building of HE pipes and of the ambient conditions due to the break (only pipes of diameter > 50 mm are taken into account) Only the safety building or the safety division in which the HELB occurs should be affected Identification of requirements on : doors (all buildings, esp. RHR System rooms) burst openings (valve compartments of safeguard buildings) ventilation ducts (in RHR System rooms) cables Flooding The flooding is assessed in the frame of Internal Flooding studies Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  18. Internal Flooding (1/3) Sources of flooding Sources considered Break or leaks of pipes Spurious actuation of Fire Fighting System Error of alignment Overfilling of tanks Rules of Internal Flooding No damage to more than 1 redundancy of a F1 system The separation between divisions is not impaired (particularly, no propagation from one safety building to another) Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  19. Internal Flooding (2/3) Detection and time for operator action Internal Flooding events are in most cases mitigated by a manual operator action (often closure of manual valves) Time limit considered in the safety cases for operator action : 30 minutes if the leak/break can be detected by signals in the MCR and the mitigation action can be carried out in the MCR 1 h if the leak/break can be detected by signals in the MCR and the mitigation action requires a local action 2 h if the leak/break is detected by signals not specific to the failed system (for ex. alarm on a sump level) If the detection signal is an alarm from a sump level, the time of filling of the sump is added (calculated or often considered equal to 30 mn) Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  20. Internal Flooding (3/3) Features credited in Internal Flooding studies Flow rate of the water under the doors and in the stair cases Draining system of the building Discharge valves Opening in the walls Level sensors in the sumps (should be F2 classified) Valves isolating the break/leak (should be F2 classified) Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  21. Internal Missiles (1/2) Internal Missiles considered Sources of missiles considered Failure of turning components (pumps, turbines, MCP wheels) Failure of pressure retaining components (valves, tanks) Rules of Internal Missiles No damage to more than 1 redundancy of a F1 system The separation between divisions is not impaired Protection against Internal Missiles The protection if necessary is provided by walls. The perforation of the wall caused by the impact of the missile is computed in the studies to verify that it is lower than the wall thickness Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  22. Internal Missiles (2/2) Internal Missiles considered Turning components Failure of the turbine of the turbo alternator not considered (deemed too unlikely) Failure of the wheels of the MCP not considered, due to their high quality of design, fabrication and in-service inspection Pressure retaining component studied : Control rods Non classified high energy valves and tanks (the failure of Q1 to Q3 valves and tanks is considered incredible by EDF) Some Q1 to Q3 classified high energy valves deemed representative (the failure of the stem or the motor is studied) Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

  23. Load Drop(1/1) 2 kinds of safety related cranes HS1 cranes Polar crane of the RB Auxiliary crane of the FB HS2 cranes the other cranes Safety analyses Failure of the HS1 cranes is not considered, due to their high quality of design, fabrication and maintenance => no safety analysis Failure of the HS2 cranes is considered, safety analysis with the general rules Flamanville 3 Safety analysis of Internal Hazards – 05/06/2014

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