APPLICATION OF BASE-ISOLATION TO NUCLEAR FACILITIES

Transcription

1 APPLICATION OF BASE-ISOLATION TO NUCLEAR FACILITIES Pierre Sollogoub Consultant (France) SECED 30/03/2016 London UK 1

2 Content General idea of base-isolation Isolation directions: H, H-V, 3D Isolators Non-nuclear applications Post earthquake feedback of experience Nuclear applications Codes and standards Some specific questions related to seismic isolation Mainly building isolation will be considered in the presentation SECED 30/03/2016 London UK 2

3 General idea of base isolation Low frequency <1Hz Accelerations in the superstructure are decreased Displacements are increased Higher damping, lower displacement First mode is predominant (orthogonal to the other modes) in general Limited amplification of acceleration with height In-structure floor response spectra With low frequency peak and possibly secondary peaks a. Acceleration response b. Displacement response SECED 30/03/2016 London UK 3

4 Directions of isolation Functions of isolation system: sustain vertical load accommodate displacement : stiffness control displacement : damping re-centering capacity Can be : 1D, 2D, 3D Rocking Usual: 2 horizontal directions SECED 30/03/2016 London UK 4

5 Isolators Bearing Dampers SECED 30/03/2016 London UK 5

6 Isolators examples d e h D Rubber bearing Lead-rubber bearing Damper Friction pendulum bearing Frequency depends only on R: radius of curvature SECED 30/03/2016 London UK

7 Isolators Hysteretic loop of HDRB (at 110% - left and 220% - right GERB Spring and Damper Spent fuel storage (Switzerland) Total Supported Weight: >5000 Metric Tons Seismic and Airplane Impact! SECED 30/03/2016 London UK 7

8 3D System «anti-rocking» Mechanism of rocking suppression system SECED 30/03/2016 London UK 8

9 Materials (Laminated) Rubber Natural or Synthetic Low Damping Rubber Bearing LDRB Lead-Rubber Bearing LRB High Damping Rubber BearingHDRB Main questions Ageing Non linear cyclic behaviour Ultimate behaviour Lead behaviour: cyclic and with time SECED 30/03/2016 London UK 9

10 Materials Sliding devices Rigid sliding Bearings Curved surface sliders : RECENTRERING CAPABILITY Choice of materials: Steel surface PTFE polytetrafluorethylene Main questions: Ageing of sliding surface Recentering SECED 30/03/2016 London UK 10

11 Non-nuclear Applications The technique is known since beginning of XXth century (USA and USSR) with few applications Derived from bridge devices Applied for conventional buildings (70s+): New-Zealand, Italy, France, Japan, USA Strong development in Japan in late 90s (after Kobe earthquake 1995 Numerous application in industrial facilities: LNG tanks RB, LRB, FPB Emergency buildings in K-K and Fukushima stations (TEPCO) 11

12 Seismic feedback of experience There are some exemples in California: Northridge earthquake 1994 USC Hospital LRB and LDRB : free field 0.49g- isolated raft: 0.13g top:0.2g Landers Earthquake 1992 Foothill Communities Justice Center HDRB: base 0.09g top 0.19g Japan (Kobe 1995, Niigata Chuetsu, 2004, Martinique (2007) Mendoza (Argentina) M5.7 in twin buildings, one fixes base and one isolated by springs and dampers Xni/i = 0.25/0.05g Yni/i = 0.4/0.06g Zni/i = 0.06/0.07g 12

13 Feedback of experience - Kobe 1995 Distorsion of pads during earthquake: 170mm Distorsion max: 400mm LRB and natural rubber bearings 13

14 Seismic feedback of experience Great Tohoku earthquake (2011) Many base-isolated buildings in Tohoku and other (Tokyo) region, with acceleration in free-field up to 0.6g Base isolated emergency buildings in NPPs:Fukushima 1 and 2, Onagawa In all cases, the behaviour was satisfactory, in the sense that the «filtering» effect was present and no unexpected phenomena were present. No damage to structures;some damages when design is deficient (on bridges) R/D Tests SECED 30/03/2016 London UK 14

15 Emergency Control Building - BWR 40.6m 52.6m Natural Rubber Bearing(φ1200)[10] Lead Rubber Bearing(φ1200)[4] Sliding Bearing[31] Oil Damper[16] SECED 30/03/2016 London UK 15

16 Design codes and Technical documents Conventional buildings ASCE/SEI 7-10 Minimum design loads for buildings and other structures, American Society of Civil Engineers (ASCE), USA AIJ (AIJ, 2013 Recommendation for the Design of Base Isolated Buildings, Architectural Institute of Japan, (in Japanese) JSSI (JSSI, 2009, 2012, 2013) Japan Society of Seismic Isolation developed texts giving list of possible devices, Guidelines for umbilical s design and elements on maintenance for buildings and bridges. EN :2004 Eurocode 8: Design of structures for earthquake resistance Part 1: General rules, seismic actions and rules for buildings EN :2005 Eurocode 8: Design of structures for earthquake resistance Part 2: Bridges NF EN 15129:2010 Anti-Seismic Devices NF EN 1337:2005 Structural bearings ISO22762: International Standard is dedicated to elastomeric seismic isolators 16

17 Design codes and Technical documents Nuclear Facilities Japan JEAG , Seismic Design Guidelines for Base-Isolated Structures of Nuclear Power Plant, Japan Electric Association, in Japanese JNES, Seismic Safety Division, Proposal of technical review guidelines for structures with seismic isolation, report n JNES-RC Europe European Commission, Proposals for design guidelines for seismically isolated nuclear plants, EUR EN, AFCEN PTAN RCC-CW 2015 French Experience and Practice of Seismically Isolated Nuclear Facilities RCC-CW 2015 edition of the AFCEN code for Civil Works 17

18 Design codes and Technical documents USA U.S. Nuclear Regulatory Commission (USNRC) NUREG/CR xx, Technical considerations for Seismic Isolation of Nuclear Facilities, Draft May 2013 ASCE Standard, ASCE 4-xx Seismic Analysis of Safety-Related Nuclear Structures and Commentary. ASCE, 20xx ASCE Standard, ASCE 43-05, Seismic design criteria for SSC in Nuclear Facilitiies, ASCE, 2005 (under revision) IAEA: TECDOC 1288 Verification of analysis methods for predicting the behaviour of seismically isolated nuclear structures (CRP ) TECDOC (Draft) Seismic Isolation systems for Nuclear Installations SECED 30/03/2016 London UK 18

19 Design codes and Technical documents OTHER documents France: Technical specifications used for RJH and ITER design USA PEER and MCEER reports EPRI Draft on Seismic Isolation for NPP AASHTO document for bridges Korea SECED 30/03/2016 London UK 19

20 Nuclear Applications Advantages Lower accelerations on structures and components, enabling simple, seismically safer, economical and standardised design Simple structural behaviour leading to a simplicity of the analyses in some cases, static analysis may be applicable for equipment inside isolated structure. Increase safety by decreasing in the uncertainties, due to the fact that the critical element is the seismic isolation system itself, for which the behaviour up to failure is better evaluated than the one of a nonisolated structure. Simpler layout, with possibly more slender buildings and more flexibility to locate equipment (for instance, due to almost constant acceleration over height, it is possible to have heavy or sensitive components located at higher elevations), Reduce costs for new build (in terms of scheduling and global price) due to the capability to reuse original design for middle range seismic input (typically g) and existing main components qualification SECED 30/03/2016 London UK 20

21 Why so few application of BI in Nuclear facilities? Licensing: BI is a «NEW» technique Construction schedule is increased Cost of isolation system and complementary raft; must be compensated by lower cost of SSCs Lack of consensus standards Nuclear Market in high seismicity zones Cost-benefit analysis has to be done; from which value of acceleration is BI interesting? Lack of audacity! SECED 30/03/2016 London UK 21

22 Nuclear projects (partial) Facility Country Type Date EFR Europe FBR 80s PRISM USA Small WR Mid 80s SAFR USA Fast Reactor Mid 80s KALIMER Korea Fast Reactor ALMR USA Fast Reactor STAR-LM USA LMR Gen IV IRIS International 2000s SILER Europe GEN IV reactors 2012 ASTRID ALFRED Europe/ France Europe/ Romania GEN-IV SFR Under develop. GEN IV LCFR Under develop. SECED 30/03/2016 London UK 22

23 Some Nuclear Projects IRIS PRISM STAR -LM 3D isolation KALIMER SECED 30/03/2016 London UK 23

24 ASTRID ALFRED GEN IV SFR France GEN IV LCFR Romania SECED 30/03/2016 London UK 24

25 French Base Isolated Nuclear Installations CRUAS 900MWe NPP (EDF) KOEBERG 900MWe NPP (RSA) La Hague storage pools (COGEMA) STAR Laboratory in CADARACHE (CEA) Georges Besse II enrichment plant SECED 30/03/2016 London UK 25

26 CRUAS NPP Facility: Nuclear Power Plant 4 Units (900MWe) EDF (1980) Location: CRUAS in the Rhone valley The plant is part of a standardised set designed to 0.2g; presence of a shallow focus 0.3g earthquake Two twin units Nuclear Island (raft dimensions: 140m x 80m) tons on 2000 pads Pads: laminated rubber bearings ; 0.5m x 0.5m x 0.065m (3 neoprene layers 13.5mm thick) Neoprene Rubber Isolation frequency: 1Hz (the objective was to limit the acceleration to 0.2g, with 5% damping) Possibility of pads replacement (qualified in-situ procedure) Koeberg NPP (South-Africa), same type of bearings with sliding plate SECED 30/03/2016 London UK 26

27 Acceleration (g) Cruas Seismic input SDD EDF 0.2g SDD CRUAS 0.3g Frequency (Hz) SECED 30/03/2016 London UK 27

28 CRUAS - Position of pedestals SECED 30/03/2016 London UK 28

29 CRUAS NPP SECED 30/03/2016 London UK 29

30 Cruas NPP Courtesy EDF SECED 30/03/2016 London UK 30

31 Design Eigenfrequency of the isolated structure It is a trade-off between effects on acceleration and on differential displacements. At Cruas-Meysse f 0 = 1Hz was selected, resulting in a 5 cm differential displacement. Main technical features Shear modulus G 0 : 1.1 GPa Damping : 7% Pressure on isolation pads: 7.5 MPa Rubber thickness: 40.5 mm Distortion under SSE: 1.2 (shear strain : 120%) Ageing effects on G Anticipated : G 0 x1.3 after 20 years ; < G 0 x1.5 after 60 years Design margin: G 0 x 2.25 (the design is still OK up to f = f 0 x1.5) SECED 30/03/2016 London UK 31

32 Design Laminated polychloroprene rubber bearings In 1978, in France, elastomer bearings pad had been used for 30 years, with an excellent experience feedback. In Europe, around road or rail bridges are placed on such pads. SECED 30/03/2016 London UK 32

33 KOEBERG NPP Construction Lower raft and pedestals ( ) Photo: Spie Batignolles SECED 30/03/2016 London UK 33

34 Koeberg (RSA) NPP PGA: 0.3 g Frequency: 0.75 Hz Pad size: 700x700x130 mm G modulus: 1.4 Mpa Friction coefficient: 0.2 SECED 30/03/2016 London UK 34

35 JHR General Design SECED 30/03/2016 London UK 35

36 RJH Seismic Design Use of industrially proven solution : square elastomere pads Low damping Frequency : 0,65 Hz at the end of life Dimensions of pads : 0,9 x 0,9 m2 Design compressive stress 7,5 MPa Maximum design distorsion : 1,4 211 Pads - Review of existing standards: EC8, AFPS90, SETRA Guidelines Ageing is taken into account by considering a margin in Shear Modulus Integration of inspection constraints - Accessibility - Testing Integration of pads replacement capability Equipment design: margins SECED 30/03/2016 London UK 36

37 ITER International Thermonuclear Experimental Reactor Under construction PGA: 0.32 g Frequency: 0.55 Hz Pad size: 900x900x181 mm G modulus: 1.1 Mpa Same isolators than RJH SECED 30/03/2016 London UK 37

38 Elastomeric bearing characteristics Mechanical properties RJH ITER ITER JHR 900x900x181 mm square bearing 6 layers of 20mm of elastomer 5x 5 mm-thick steel plates + 2 external 15 mm-thick steel plates Dynamic shear modulus: G d = 1.1 MPa Damping : 5% Shape factor S PGA Number isolators of (hard soil) Mass (t) ~ ~ Isolation frequency (Hz) Service (N Sd ) loading MN (s = 8 MPa) 5.67 MN (σ = 7 MPa) Displacement d bd (mm) SECED 30/03/2016 London UK 38

39 Georges Besse II enrichment plant Seismic spectrum of TRICASTIN 1,0000 Acceleration (g) 0,1000 Facility isolated for protection of the investment considerations 0,0100 SMS 5% IPS2 5% 0,0010 0,10 1,00 10,00 100,00 Frequency (hz) Elastomeric bearing characteristics Mechanical properties GBII Circular bearing of diameter 500mm Height around 400mm Dynamic shear modulus: G d = 0.7 MPa, Damping : 7 % PGA 0.3g Displacement (mm) d bd SECED 30/03/2016 London UK

40 Some specific questions related to seismic isolation Design of Isolators Manufacturing - Material Qualification Ageing - monitoring Input signal (low frequency) Isolator(s) replacement Construction tolerances (on site) Control of vertical loads on isolators Construction phasing Vertical stiffness of isolators Tension loads / uplift Other external events: fire, aircraft crash Connecting structures umbilicals Effect of isolators damping Non-linear isolator behaviour H and V coupling Cruas- replacement of 2 isolators SECED 30/03/2016 London UK 40

41 Some specific questions Ultimate behaviour of the isolation system Margins Beyond design conditions PRA Hard stop or not moat design Ductility demand Signal on isolated part has a «low frequency» content. Ductility demand may be important. A complementary margin above calculated response spectrum is necessary In structure Response Spectra Equipment design SECED 30/03/2016 London UK 41

42 Inelastic Spectra RG1.60 spectrum Frequency 3,4 3,2 3 2,8 2,6 2,4 Elastic Duct. 2.0 Duct. 3.0 Duct. 5.0 Elastic Response Acceleration [g] 2,2 2 1,8 1,6 1,4 1,2 1 0,8 0,6 0,4 0, Frequency [Hz] SECED 30/03/2016 London UK 42

43 Base Isolated Structure inelatic FRS Frequency 6 5,5 5 4,5 Elastic Duct. 2.0 Duct. 3.0 Duct. 5.0 Elastic Response Acceleration [g] 4 3,5 3 2,5 2 1,5 1 0, Frequency [Hz] SECED 30/03/2016 London UK 43

44 In Structure Response Spectra Example: ITER (fusion experimental reactor) [Combesure et al, 2010] Horizontal floor spectra SECED 30/03/2016 London UK

45 In-structure Response spectra Secondary peak may be due to: Vertical Horizontal coupling Kinematic interaction in embedded foundations Damping in the isolation system «Simple» dynamic behaviour is no more applicable SECED 30/03/2016 London UK 45

46 Equipment behaviour 10 2 spectre pseudo-accélération m/s2 RCC-E SQUG BI structure fréquence (Hz) SILER International Workshop, June 2013, Roma 46

47 Conclusions There are many techniques for base isolation Manufacturing quality, ensure a good long term behaviour Good behaviour of base isolated structures during earthquakes There are examples of base-isolated nuclear facilities Some care must be exercised in design Seismic isolation is a mature technique for nuclear facilities SECED 30/03/2016 London UK 47