Eletronuclear ( Brazil) Fukushima Response Plan

Transcription

1 Eletronuclear ( Brazil) Fukushima Response Plan Edmundo Selvatici Site Manager Mario de Mello Ferreira Junior Manager, Materials Engineering Technical Meeting on Operational Experience with Implementation of Post-Fukushima Actions in Nuclear Power Plants march

2 Angra Nuclear Power Station (single NPP site in Brazil) ANGRA 1 PWR Power: 640 MW Technology: Westinghouse Operation start: Jan ANGRA 2 PWR Power: 1,350 MW Technology: KWU/ Siemens Operation start: Jan ANGRA 3 PWR Power: 1,405 MW Technology: KWU/ Siemens/ Areva Under construction Planned start of operation: 2022 (illustrative view) ANGRA 1 ANGRA 2 RADIOACTIVE WASTE STORAGE CENTER 500kV Switchyard 2

3 Plan in Full Integration with Nuclear Industry Initiatives Brazilian Nuclear Authority 3

4 Response to Fukushima Main Safety Goals

5 Response to Fukushima Evaluation of ST Report Basis: WENRA Specification for Stress Test Report FORO Angra 1 and Angra 2 NPPs Stress Test Report Evaluation 5

6 Protection from Hazard Events External Events Earthquakes; Rainfalls; Landslides; Tidal Waves; Tornadoes. Assessment of existing DB external event scope and design criteria for completeness and updating Assessment of safety margins of existing design in case of BD external events 1st step: simplified calculations, engineering/expert judgement 2nd step: detailed deterministic and probabilistic analyses. Internal Events Fire; Internal Flooding. Reevaluation considering up-to-date safety requirements; Identification of design gaps. 6

7 Protection from Hazard Events - Results Earthquakes Plants Seismic Design Low seismicity site (intraplaque region). Largest recorded earthquake 5.2 Richter scale at 300 km (PGA 0.002g at site); Design PGA for SSE: 0.1g (p< 10-4 /yr) based on deterministic seismic response spectrum. Evaluation of margins estimated safety margins relative to Design PGA by expert walkdown and judgement : for Angra 1 and for Angra 2; Extensive updating of geological and seismological database (three-years program completed); PGMRS( Probabilistic Ground Motion Response Spectrum) determined for use in the Seismic PSA; Seismic PSA for Angra 2 completed (safety margin: up to 4xDesign PGA) 8

8 Protection from Hazard Events - Results Rainfall and Landslides Evaluation of margins Studies considering heavy rains and consequential or seismic induced landslides concluded. Extreme case of full rupture of slope covering material evaluated. Slopes very steep around the site Residual and colluvial soils High rainfall rates Station protected by slope stabilization works and slope monitoring system 8 Results: For worst case switchyard and discharge channels may be affected however no impact on Plants buildings; Recommendation for enlargement of slope drainage system and reinforcement of some stabilization works (ongoing) 9

9 Protection from Hazard Events - Results External Flooding plant construction level access to safety buildings Angra 1 and m m 0 CNG Evaluation of margins: Reevaluation of flooding level under more severe conditions concluded (rainfall rate higher than 10,000 years rainfall, blockage of site drainage channels and circulating water discharge tunnel due to landslides, highest sea level). Results: Current design flooding level includes sufficient safety margin (up to years rainfall); Recommendation for checking and reinforcement of existing flooding barriers (finished). 9

10 Protection from Hazard Events - Results Tidal Waves calculation of tidal waves for severe metereological conditions( sea storms and hurricanes) at Ilha Grande Bay concluded; largest waves> maximum design wave for wave breaker design evaluation of wave breaker stability through physical model by international lab being contracted; Results may lead to recommendation of breaker structural reinforcement Angra NP Station Ilha Grande Bay Bay area, natural protection from Atlantic Ocean 11

11 Protection from Hazard Events - Results Tornadoes Tornadoes were not originally considered for Angra 1 and 2 due to low probability (~10-7/y); Tornado hazard study developed for Angra 3; Impact on Angra 1 and 2 evaluated and actions plans issued for further evaluation and/or protection of selected structures and components. Internal Fire Internal Flooding Fire Hazard of Angra 1 revised by EPRI (risk based evaluation); design modification packages under evaluation. Reevaluation of Angra 1 design against internal flooding; Recommendation to increase the safety margins under evaluation 11

12 Evaluation of Station Blackout Scenarios (SBO) Existing power supply conditions for Angra 1 and Angra 2 (Design or backfit) Cachoeira Paulista São José SE 500kV Zona Oeste SE 138kV Santa Cruz Off site Power Angra 1: 2x100% DG ( Plant Design) + 2x100% DG (backfit) Same cooling system for all DG A2 A1 Angra 2 Angra 1 4 x 50% 2 x 100% 4x 2x M G M G UBP D1 EDE 3/4 A2 A1 Emergency Diesels 1 st Emergency Power System Angra 2: 4x50% EDG + 4x50% EFDG in dedicated bunkered building with independent cooling system. M 4x G ULB D2 Minimum batery duration 2x 2x M G EAS 1A/1B 2,5h 4,0h 2 nd Emergency Power System both meet NRC requirements for exclusion of SBO 14

13 Existing SBO Emergency Procedures SG feeding through steam turbine driven pumps (Auxiliary Feedwater Turbine Pumps) in Angra 1 and Diesel Driven Emergency Feedwater Pumps in Angra 2); at least 20 hours in Angra 1 and 33 hours in Angra 2 of feeding from, respectively, Auxiliary Feedwater Tank - AFT and Demineralized Water Pools - DWP; possibility of AFT and DWP refilling from Fire Fighting Water Supply System - FFWS (5,000 m 3 reservoir, located on an elevation 110 m above the site level); possibility of full passive secondary B&F from the FFWS reservoir (connection before SG becomes empty, in case AF-2 or LAS pump fails, about 50 minutes). 15

14 Evaluation of Loss of Main Heat Sink Existing design conditions: water intake structures protected from open sea hazards (Ilha Grande Bay); water intake structures protected by wave breaker 8.0 m high above average seawater level; Availability of alternative heat sink by means of Fire Fighting Water Supply System - FFWS (5,000 m 3 reservoir, located on an elevation 110 m above the site level); alternative already incorporated in Emergency procedures for both Plants. Not designed for earthquake.. Main implications for the plants: Angra 1: failure of both Emergency Diesel Generator Systems (failure of common cooling system); Angra 2: Only EDG fail. Bunkered Emergency Feedwater Diesels (EFDG) not dependent of Service Water; impossibility of operating the RHR chain. 16

15 Provision of Cooling Capacity extreme conditions Deterministic evaluation approach (WENRA/FORO guidelines) no credit given to special design features or former backfits at the Angra plants no possibility of external support within 72h after the accident onset; Event Initial Conditions Loss of Offsite and Onsite Power (SBO) and Loss of Ultimate Heat Sink (LUHS) Plant in Power Operation 100% reactor power; Plant at Refueling (worst condition for fuel pool temperature) full core transferred to fuel pool; full loading of fuel pool storage racks; 15

16 Stress Test results Based on the Stress Tests results mobile equipment to provide additional means to supply power and cooling capacity for the core and the fuel pools were identified, specified and purchased, comprising different sizes of Diesel Generators, Diesel driven pumps and associated connection fixtures. General Concept adopted for Mobile equipment Equipment stored on site in location that is not affected by the external events that would affect the site, housed in a light tent-like structure commercial grade equipment; Mobile equipment connections specified in accordance to the Requirement Category of the systems where the connection is applied. Mobile equipment incorporated to the decision trees of the EOPs; Mobile equipment have specific procedures; not incorporated to the Tec Specs. 16

17 Stress Test results Design modification processes have been developed for the short and medium term strategies, in case of loss of all AC power and/or UHS, as follows: Short term (1 to 3 hours): recharging of batteries and Steam Generator feed. Mobile equipment : one 250 KVA DG and 2 Diesel Driven pumps per Plant; Countermeasure: Bleed and Feed through the secondary side. Medium term (1 to 2 days): in case of available UHS. Countermeasure: repowering one RHR cooling train Mobile equipment: 3 large DG, of 600 KVA each for Angra 1; 2 large DG, of 600 KVA each for Angra 2. Medium term (1 to 2 days): in case UHS is unavailable Countermeasure: continue Secondary B&F and replenish source of water for SG cooling (tank/pool) with sea water; Mobile equipment: 2 submergible Diesel powered pumps 16

18 Stress Test results The implementation of a new water reservoir of 4000 m 3 meeting seismic requirements located at a height able to provide means of feeding the steam generators in a totally passive way, is in phase of design completion. An alternative means of cooling the Diesel Groups in Angra 1, in case of loss of the Service Water System (SWS), was developed by installing a connection in the SWS piping for sea water injection with a mobile Diesel powered pump. 16

19 Overview of Additional Emergency Supply Alternatives Mobile DG (Emergency Power Supply for essential Safety Systems) 2017 status (completed) 2017 status (completed) Mobile DG (Emergency Power Supply for essential Safety Systems) Interconnection of Diesel Systems D1 and D2 (intended) 2017 status (design concluded) Alternative cooling chain for Angra 1 Emergency Power DG ANGRA 2 ANGRA 1 Mobile DG (extension of batteries autonomy) 2017 status (final implementation) 2017 status (final implementation) Mobile DG (extension of batteries autonomy) 17

20 Additional Alternatives for Reactor Cooling Alternatives for Reactor Cooling Via Steam Generators Angra 1 and Angra 2: Secondary side bleed-and-feed through the Steam Generators. (2017 status final implementation) Alternatives for Direct Reactor Cooling Angra 2 Primary side bleed-and-feed : Installation of additional valves in the Pressurizer valve station with dedicated power supply and I&C. (2017 status completed). Ensures depressurization of Primary System(bleed). 18

21 Additional Alternatives for Reactor Cooling Mobile Pumps for SG Feeding Mobile Pumps for Refilling Water Reservoirs Fire Hoses Mobile Ar Compressor for Remote Valve Actuation (Angra 1) 19

22 Mobile Equipment maintenance and storage Testing and Maintenance activities: - All tests and maintenance are being performed according the equipment supplier manuals; - Weekly sequence of DG performance tests, mobile pumps and mobile air compressor; 21

23 Loss of Fuel Pool Cooling Fuel Pool Temperature Increase after Loss of Cooling Unit Plant condition Time until start boiling Time until fuel element exposure Angra 1 Angra 2 Power Operation 28 h 179 h Refueling (*) 9 h 56 h Power Operation 23 h 136 h Refueling (*) 5 h 31 h (*) Full core unloaded and full occupation of pool racks Fuel Pool Cooling alternatives : Angra 1 (SFP in external Fuel Building): Feed to the SFP from outside fire fighting FF) water reservoir or FF truck. (2017) Angra 2( SFP inside Containment): fuel pool cooling using fire fighting water 2018) 22

24 Mitigation of Radiological Consequences Containment Protection: Passive H2 catalytic recombiners (PARs) already installed in Angra 1 and 2 (completed) Containment Filtered Venting (CFV): AREVA CFV (wet option) under design for Angra 2. Implementation in steps due to budget limitations Not yet decided for Angra 1. Severe Accident Management Guidelines (SAMGs): Angra 1: WOG SAMGs have been implemented and integrated with the Emergency Planning (EP) procedures. Angra 2: AREVA SAMGs have been developed, implemented and integrated with the Emergency planning procedures. Other improvements of the infrastructure for Emergency Planning Implementation of trails in emergency planning zones (completed) Improvements in Emergency Centers (underway) Improvements in radiological protection controls for Severe accident situations( underway) 23

25 Thank you for your attention. 24