| 1SILER International Workshop – 2013/06/18-19 – Rome
French experience and practice of seismically isolated nuclear facilities – Main considerations
1 NUVIA Travaux Spéciaux, Lyon, France
2 EDF Nuclear Engineering Division SEPTEN, Lyon, France
3 AREVA Engineering & Projects, Lyon, France
Sébastien DIAZ & Micaël CONNESSON1, Frédéric ALLAIN2, Nadim MOUSSALLAM3, Ilie PETRE-LAZAR2
| 2SILER International Workshop – 2013/06/18-19 – Rome
Introduction
Since recent events in KK and FKS, there is a global renewal of interest in seismic isolation technologies.The IAEA is preparing a TECDOC dedicated to the seismic isolation of nuclear facilities.For more than 30 years, seismic isolation technologies have beenused by operators of nuclear facilities in France (EDF, AREVA, CEA, I/O) to protect them against earthquake loading.To support the IAEA documentation effort and to share knowledge with other member countries, a synthesis of the French practice and experience is being jointly written by operators, designers and manufacturers.This presentation is an extract from this work. The full document will be published by AFCEN before the end of 2013.
Le Groupe NuviaFrench practical examples of isolated NPP 1ActivitésIsolated plant overview 2Gamme de produitsPlant design 3Exemples de projetsIsolators design & technological choice 4Exemples de projetsEquipments design 5
| 3SILER International Workshop – 2013/06/18-19 – Rome3
Le Groupe NuviaFrench practical examples of isolated NPP 1ActivitésIsolated plant overview 2Gamme de produitsPlant design 3Exemples de projetsIsolators design & technological choice 4Exemples de projetsEquipments design 5
| 4SILER International Workshop – 2013/06/18-19 – Rome4
| 5SILER International Workshop – 2013/06/18-19 – Rome
Cruas NPP
4 PWR 900 Mwe units,EDF, Cruas, France
CruasNPP
Dynamic shear modulus: Gd = 1.1 MPa ± 0.10 MPa,Damping : 7.5 ± 1%
Shape factor S 9.26PGA 0.3 gIsolation frequency (Hz) 1Displacement dbd (mm) 48
Elastomeric bearing characteristics
Mechanical properties
500 x 500 x 66.5 mm square bearing 3 layers of 13.5 mm of elastomer 2 x 3 mm-thick steel plates + 2
external 10 mm-thick steel plates
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courtesy of EDF
| 6SILER International Workshop – 2013/06/18-19 – Rome
Cruas NPP 1
courtesy of EDF
| 7SILER International Workshop – 2013/06/18-19 – Rome
La Hague Spent Fuel Storage Pools
Spent Fuel Storage PoolsAreva, La Hague, France
La Hague700 x 700 x 147 mm square bearing10 layers of 10 mm of elastomer9x 3 mm-thick steel plates + 2 external 10 mm-thick steel platesDynamic shear modulus: Gd = 1.1 MPaDamping : 7%
Shape factor S 17.5PGA 0.2gIsolation frequency (Hz) 0.85Displacement dbd (mm) 120 (including torsion motion)
Elastomeric bearing characteristics
Mechanical properties
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courtesy of AREVA
| 8SILER International Workshop – 2013/06/18-19 – Rome
Jules Horowitz Reactor
Experimental and medical research-dedicated reactorCEA, Cadarache, France
JHR900x900x181 mm square bearing6 layers of 20 mm of elastomer5x 5 mm-thick steel plates + 2 external 15 mm-thick steel platesDynamic shear modulus: Gd = 1.1 MPaDamping : 5%
Shape factor S 11.25PGA 0.315 g (hard soil)Number of isolators 195Mass (t) ~110 000Isolation frequency (Hz) 0.6Service loading (NSd) 5.67 MN (σ = 7 MPa)Displacement dbd (mm) 108
Mechanical properties
Elastomeric bearing characteristics
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courtesy of CEA
| 9SILER International Workshop – 2013/06/18-19 – Rome
ITER
Experimental fusion tokamakF4E, Cadarache, France
ITER900x900x181 mm square bearing6 layers of 20 mm of elastomer5x 5 mm-thick steel plates + 2 external 15 mm-thick steel platesDynamic shear modulus: Gd = 1.1 MPaDamping : 5%
Shape factor S 11.25PGA 0.315 g (hard soil)Number of isolators 493Mass (t) ~ 300 000Isolation frequency (Hz) 0.55Service loading (NSd) 6.4 MN ( = 8 MPa)Displacement dbd (mm) 112
Elastomeric bearing characteristics
Mechanical properties
Lower bear ing plate
Connec tors
Non-shrinkage grout laye r La te ral removable stops
Elastome ric be aring
Upper bearing plate
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courtesy of F4E/IO
Le Groupe NuviaFrench practical examples of isolated NPP 1ActivitésIsolated plant overview 2Gamme de produitsPlant design 3Exemples de projetsIsolators design & technological choice 4Exemples de projetsEquipments design 5
| 10SILER International Workshop – 2013/06/18-19 – Rome10
| 11SILER International Workshop – 2013/06/18-19 – Rome
Plant overview
Lower basemat
Plinth (or Pedestal)
Isolator
Shear studsUpperbearing plate
Lowerbearing plate
Lateral removablestops
Elastomeric bearing
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Le Groupe NuviaFrench practical examples of isolated NPP 1ActivitésIsolated plant overview 2Gamme de produitsPlant design 3Exemples de projetsIsolators design & technological choice 4Exemples de projetsEquipments design 5
| 12SILER International Workshop – 2013/06/18-19 – Rome12
| 13SILER International Workshop – 2013/06/18-19 – Rome
Plant design
Similar design practice to non-isolated NPP design, except a few particularities,
Preliminary design : rigid body behaviour : 1 DOF system analysis ,or simplified rigid 3D model,
Detailed design stage (1/2) : 3D model of the structure,
Soil-Structure-Interaction,
Modal-spectral analysis is limited to projects usingbearings with linear behavior,
3D Time-history calculations contribution of the verticalmotion to the horizontal response
JHR (amplified deformation)
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| 14SILER International Workshop – 2013/06/18-19 – Rome
Plant design
Detailed design stage (2/2) Effects of construction sequence, creep and shrinkage (one model for each step), Specific temporary load cases (replacement of one or several bearings),
Bearing Input data: Real mechanical properties: standards formulae not 100% applicable for metric-size bearings full-scale tests Ranged mechanical isolators properties, including:
– Production tolerances → impact on production quality follow-up– Beginning / end of service life: ageing influence → accelerated ageing tests
qualification step
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| 15SILER International Workshop – 2013/06/18-19 – Rome
Plant design
Bearings layout optimization :Uniform vertical distribution of loads: ±20% of deviation (EC8)
reduction of torsional mode,
Constructibility & MaintenanceAccesses to plinths
Interfaces with reinforcement
Therefore, isolators plan layout to be adapted accordinglyPlinth Reinforcement interface
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| 16SILER International Workshop – 2013/06/18-19 – Rome
Plant design
Other design recommandations :Sizing the seismic gap, from Beyond Design evaluations and objectives,
Specific sizing of the pedestals (could be subjected to unusual loads for beyond-design earthquake),
Specific design of « beam-walls » connected to the upper raft,
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| 17SILER International Workshop – 2013/06/18-19 – Rome
Plant design
Qualification of the isolators“Real” mechanical properties Dynamic compression, dynamic shear:
effects of frequency / distortion variation on the stiffness and damping Creep test
Aged mechanical properties
Validation of scale effects on samples: full-scale bearings vssamples Used for accelerated ageing tests Used for monitoring after commissioning of the plant
Comparison of acceleratedageing tests on samples &
full-scale bearings
Creep test
Comparison of dynamicshear tests on samples & full-scale bearings
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Le Groupe NuviaFrench practical examples of isolated NPP 1ActivitésIsolated plant overview 2Gamme de produitsPlant design 3Exemples de projetsIsolators design & technological choice 4Exemples de projetsEquipments design 5
| 18SILER International Workshop – 2013/06/18-19 – Rome18
| 19SILER International Workshop – 2013/06/18-19 – Rome
Safety requirements
Functional & Safety analysis of the Seismic Isolation (Safety Important Component)Stable (over time, radiations) & Resistant to fire
Robust & durable
Proper transmission of the loads
Repleacable
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| 20SILER International Workshop – 2013/06/18-19 – Rome
Safety requirements & design implications
Technological solution impacts the design criteriaFrench experience is based upon Elastomeric Bearings
Polychloroprene Rubber bearingCompounding: damping ratio tuned through Carbon black addition
No scragging: stiffness / damping stable over cyclic deformations
Predictible & stable creep
Gd from 0.4 to 1.4 MPa
Limited resistance to cold temperatures
Flame retardant: endothermic reactiondue to chlorid acid formation
Stability & Fire resistance
Robustness & durability
Load transmission
Repleacability
Cl
– CH2 – C = CH – CH2 –
Cl
– CH2 – C = CH – CH2 –
CR cross-linking system
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| 21SILER International Workshop – 2013/06/18-19 – Rome
Safety requirements & design implications
Self-standing system: do not rely on any other mechanical system to damp the displacement
Damping ratio taken conservatively = 5 to 6% (LDRB - CR)
Lateral displacementUltimate distortion limited to 140% of elastomer thickness linear behaviour of the isolator on its working range
Possibly: hard-stop for beyond-design case (not implemented in France)
Long service life (up to 60 years)Creep under high distortion limited service compression: 7 to 8 MPa in service (up to 20 MPa in ultimate)
Radiation & Air exposure: oxidation stiffening accelerated ageing tests
Stability & Fire resistance
Robustness & durability
Load transmission
Repleacability
Beyond design test – 400% shear strain
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| 22SILER International Workshop – 2013/06/18-19 – Rome
Safety requirements & design implications
Accelerated ageingArrhenius law applicable for the stiffness (G): Ageing mechanisms are identical at Room Temperature and until 100°C Temperature accelerates ageing reactions
(Increase of Gd over service life) x (production tolerance) x (safety coefficient) = design value
Stability & Fire resistance
Robustness & durability
Load transmission
Repleacability
T increases
0%
5%
10%
15%
20%
25%
30%
35%
40%
0 500 1000 1500 2000 2500 3000Time
P/
P 0
T1
T2
T3
T4
Gd/Gd0
X% increase in Gd
log(t)
log(t)
0
2
4
6
8
10
12
14
16
18
0.0025 0.0026 0.0027 0.0028 0.0029 0.0030 0.0031 0.0032 0.0033 0.0034 0.0035
1/T
ln(t)
Service temperature
Time in which Gd will have increasedby X% at service temperature
1/T
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| 23SILER International Workshop – 2013/06/18-19 – Rome
Safety requirements & design implications
Horizontal loadFrom the isolator point of view: Friction between the isolator and the steel plates not taken into account in seismic event Shear studs & lateral removable stops
From the plinth point of view: sufficient margin against bending
Horizontal response not biased by the vertical stiffnessDesign criteria: limited initial rotation in the isolator at the end of installation → specific implementation at construction stage
up-to-date French seismic level: no tension in the isolators but allowed in EN15129
So far: min > 1 MPaFrom a technological point of view, easier replaceability
Stability & Fire resistance
Robustness & durability
Load transmission
Repleacability
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| 24SILER International Workshop – 2013/06/18-19 – Rome
Safety requirements & design implications
Ability to replacement to be taken into account
In the upper basemat design: layout & local bending
In the technology of the isolator
Sequence of works:1) load transfer (propping) design load case2) removal of lateral stops and “fuse” mortar layer3) replacement of the isolator4) recompression through a flat jack (injected with grout)
Stability & Fire resistance
Robustness & durability
Load transmission
Repleacability
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Le Groupe NuviaFrench practical examples of isolated NPP 1ActivitésIsolated plant overview 2Gamme de produitsPlant design 3Exemples de projetsIsolators design & technological choice 4Exemples de projetsEquipments design 5
| 25SILER International Workshop – 2013/06/18-19 – Rome25
| 26SILER International Workshop – 2013/06/18-19 – Rome
Equipments design
Design essentially similar to the design of equipments in a non-isolated nuclear structure: same design codes, same methodologies.Specificity arises from the type of loading, that must be carefully determined to capture cross-direction coupling effects. 3D building models are mandatory.
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| 27SILER International Workshop – 2013/06/18-19 – Rome
Equipments design
Specific design solutions developed for connections between the isolated and the non isolated structuresEx: Cruas NPP
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| 28SILER International Workshop – 2013/06/18-19 – Rome
THANK YOU
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