SAFETY REQUIREMENTS IN FRANCE FOR THE PROTECTION AGAINST EXTREME EARTHQUAKES

Transcription

1 SAFETY REQUIREMENTS IN FRANCE FOR THE PROTECTION AGAINST EXTREME EARTHQUAKES French Safety Authority Nuclear Power Plants Department Radioprotection and Nuclear Safety Institute IRSN/PRP-DGE/SCAN/BERSSIN M. Romain PIERRE M. David BAUMONT International Experts Meeting on Protection against Extreme Earthquakes and Tsunamis IEM3 IAEA 1

2 Content 1. The nuclear safety approach in France to determine the seismic loadings 1. Deterministic approach 2. Complementary methods (PSA, SMA, Earthquake-event approach) 2. Conclusions of the complementary safety assessment relative to earthquake 3. National crisis drill «nuclear and seismic» 1. Crisis organization 2. Drill Scenario 2

3 Nuclear safety approach in France to determine the seismic loadings RFS French Safety Authority Nuclear Power Plants Department IEM3 IAEA 3

4 Safety approach in France The nuclear safety approach in France is based on: The prime responsibility of the licensee for the safety of its facilities; Continuous improvement of nuclear safety and radiation protection. ASN defines safety objectives The licensee realises the demonstration of the safety with methods of his choice ASN guides and safety rules (RFS) produced by ASN with the technical support of IRSN: Texts that are not legally binding These are recommendations which : imply an interpretation of positive law ; clarify the safety objectives and describe practices that ASN considers to be satisfactory to reach the objectives set by the regulatory texts. These rules can be made legally binding by a formal decision French regulation is globally deterministic. 4

5 French regulatory recommendations applicable to NPP s Soil characteristics RFS 1.3.c (1984) Seismic ground motion RFS (2001) Earthquake design Guide ASN/2/01 (2006) Instrumentation RFS 1.3.b (1984) 5

6 Regulatory requirements for Seismic Hazard for French NPPs 1981 : Regulation devoted to the SHA for nuclear installations : «French Safety Rule» : Revision motivated by the improvement in : - Characterization of active faults - Estimation of the magnitude of historical events - GMPE based on numerous recent accelerometric data recorded in Europe - Experience feedback on the importance of site effects following important earthquakes (Mexico 1985, Loma-Prieta 1989, Northridge 1994, Kobe 1995 ) 2001 : New safety rule, named RFS /20 6/9

7 RFS Requirements for Seismic Hazard for French NPPs SCOPE OF RFS Safety-related functions must be maintained during and following plausible earthquakes that could affect nuclear installations. Define an acceptable method for determining the vibratory ground motions that are to be taken into account in the seismic design. BASICS OF RFS In this French deterministic approach, we assume that EQ analog to past events can happen in the future in a penalizing location for the facilities. Definition of the characteristics of "Maximum Historically Probable Earthquakes" (SMHV) considered to be the most penalizing earthquakes liable to occur over a period comparable to the historical period (~ yrs). Definition of a "Safe Shutdown Earthquakes (SMS) to account for uncertainty on the definition of MPHE, which may be completed by paleoseismological evidences. 7/20 7/9

8 Step 1 - Characterizing Seismic Source Zones & Potentially Active Faults In France, tectonic deformation rate and seismic activity are low. EQ are often difficult to relate to a specific fault. The RFS recommends to define seismotectonic zones where the seismogenic potential is assumed to be homogeneous. Example of IRSN seismotectonic zoning scheme (Baize et al., 2012). 8/20 8/9

9 Step 2 - Defining Reference Earthquakes for NPP sites Historically known EQ can occur in the future at any point of their seismotectonic zone. The most penalizing location for the NPP (in terms of intensity) is retained (i.e. closest distance to site). "Maximum Historically Probable Earthquakes - SMHV ID, distance, predicted intensity at site Example for Paluel NPP IRSN scheme 9/20 9/9

10 Step 2 - Defining Reference Earthquakes for NPP sites Historical seismicity data are hindered by a lack of precision concerning both the accuracy of the facts and the assessment of macroseismic intensity levels. Information collected in an updated macroseismic data base ( "Maximum Historically Probable Earthquakes - SMHV ID, distance to site, magnitude and depth, predicted intensity at site Example for the 1775 Caen EQ IRSN scheme 10/20 10/9

11 Step 3 - Defining the Safe Shutdown Earthquake In order to take account of uncertainties inherent in the determination of the SMHV characteristics, a fixed safety margin is defined as follows. For each SMHV, we define a "Safe Shutdown Earthquake" (SMS), deduced from the SMHV by increasing the intensity at site by one unit : I SMS = I SMHV +1 Safe Shutdown EQ SMS A one-degree increase in intensity corresponds to an increase in magnitude conventionally set at /20 11/9

12 Step 4 - Accounting for Paleoseismic Evidences Active faults are considered in the regulation only in the presence of paleoseismic evidences 12/20 12/9

13 Step 5 - Calculation of Seismic Ground Motion Pseudo-accélération (g) Fréquence (Hz) SMS Sédiments M=5.3 Distance= 10 km - EDF Minimal forfaitaire 0,1 g sédiment EDF 0,2 g Seismic motion is defined by the response spectra of the horizontal and vertical components of the motion on the surface of the site ground. This definition can be supplemented by other parameters. Input parameters = Surface-waves magnitude, hypocentral distance and soil conditions Median value of GMPE for SMHV, SMS and paleoeq A minimum fixed spectrum anchored at a PGA of 0.1 g is applied 13/20 13/9

14 Deterministic and probabilistic approaches The demonstration of the safety of these installations is based firstly on a deterministic approach. This approach is supplemented by probabilistic safety assessments (PSA), which needs to be feed with PSHA. PSAs are to be used as a complement to deterministic studies and not as a substitute for them. Low frequency content = Large EQ on the Cévennes fault High frequency content = Local moderate EQ translated below the NPP Baumont & Scotti (2008) 14/20 14/9

15 Complementary methods (2/2) Seismic Margin Assessment (SMA): Aims: Study the robustness of the facility to an earthquake larger than the design-basis earthquake. Deterministic study of the strength of equipment, systems and structures necessary for shutdown of the unit to a safe state, considering as standard a small RCS break and a loss of offsite power Identification of the points which, if improved, would reinforce the robustness (construction measures, protection, relocation of equipment and so on) ASN asked EDF to include this topic in the forthcoming periodic reactor safety reviews Earthquake event approach Aim: prevent damage to an equipment item necessary in the event of an earthquake by an item or structure not seismicclassified. Approach implemented on the occasion of the periodic safety review. 15

16 Periodic Safety Reviews and Seismic Reinforcements PSR Process Seismic PSR Seismic reinforcements Design Every 10 years Compliance exam reassessment Laws impose PSR Opinion of ASN after licensee report Most recent safety objectives taken into account ASN policy : improvement of the safety level (former design vs. new safety standards) Ground motion Rules for earthquakeresistant construction Resistance studies, reinforcement Margin studies (SMA), seismic PSA, Eventearthquake approach Non conformity, incident, inspection OEF (French and worldwide) Modifications (equipment, seismic qualification) Maintenance Strengthening concrete structures using fibre composite material 16

17 Conclusions of the complementary safety assessment Earthquakes French Safety Authority Nuclear Power Plants Department IEM3 IAEA 17

18 Complementary Safety Assessments Specific inspections 2-3 days per NPP Fukushima-related topics 38 inspections (June-Oct. 2011), 116 days of inspection Stress Tests requested by the European Council and the French Prime Minister Based on Europeans stress tests Specifications 150 nuclear installations, 21 Licensees Includes Human and Organizational Factors 18

19 Conclusions - Earthquakes Seismic margins on the nuclear reactors and the more recent fuel cycle facilities are sufficient to prevent cliff-edge effects from occurring in the event of a limited overshoot of the current baseline safety requirements However, ASN identified several areas in which safety could be improved, related to the robustness of the facilities to earthquakes and it will be asking for: Protection against fire for equipment used to control the basic safety functions; Greater awareness and assimilation of the seismic risk by the operators in the day-today operation of the facilities, by strengthening operator training, improving the awareness of the "event-earthquake1", ensuring compliance with the basic safety rule concerning seismic instrumentation (maintenance, operator familiarity with the equipment, calibration); For some facilities, study analysing the seismic robustness of the dykes and other structures designed to protect the facilities against flooding and to present the consequences of a failure of these structures. Hardened safety core: beyond basis design this level of robustness beyond basis design will be integrated into French regulation. ASN has decided to review the methodology for assessing the effects of earthquake on nuclear facilities, to take account of experience feedback from the Fukushima accident, the most recent data and the best international practices 19

20 National crisis drill «nuclear and seismic» Cadarache Site January 17th, 2012 French Safety Authority Nuclear Power Plants Department IEM3 IAEA 20

21 Crisis organization Public authorities Government Prefet Off-site emergency plan: PPI Emergency services Nuclear Authorities IRSN Licencees On-site emergency plan: PUI 21

22 Simulation of a realistic event in terms of earthquake and consequences : M = 5.5 P = 5 km 12 km from Cadarache Simulation of a nuclear accident induced by an earthquake having affected a large territory around the site The damage to the nuclear site and the vicinity were assessed from the earthquake scenario and from the already known vulnerability of the structures and equipment. Scenario Outside the centre: - More than homeless; - 90 fatalities; - 45 persons under rubbles; severely injured people; slightly injured persons; destroyed buildings; partially destroyed buildings; cracked buildings. 22

23 Radioactive emission Scenario In the CEA Radioactive emission T 0 T min Earthquake First major event on a nuclear installation Loss of telecommunications T h30 Second major event on another installation T h T h 30 Loss of power supply on the site Contaminated wounded persons Contamination of the staff Rescue opérations No seismic replica during the drill Control and decontamination Management of the events on the installations 23

24 The drill The licensee simulated a diagnostics and put the installation in a safe state Evacuation of workers if needed 24

25 The drill In the CEA The licensee called external specialized services (specialized firemen, decontamination services, clearing services) Specialized firemen simulated to rescue people. 25

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27 The drill Inside the centre The licensee simulated to call external emergency services (firemen, clearing services, decontamination services) 27

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29 The drill In the CEA Robots of INTRA 29

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31 The drill Ouside the centre Rescue to population Evacuation 31

32 Radioactivity measures The drill Outside the centre 32

33 Learned Lessons The aims of this drill were reached Experience feedback: Sheltering procedure are not adapted in case of an earthquake and a nuclear crisis (dammages of buildings) Importance of means of emergency (robots, radioactive measures, telecommunications) and of external services (specialized firemen, clearing services and decontamination services) 4 prefets (zone prefet + region prefet) need for a single center of command 33

34 A movie on this drill French and English versions 34

35 Questions? 35