How to isolate a NPP vC - · PDF fileHOW TO ISOLATE A NPP ? ... How to increase the quality...

Présentation Nuvia Travaux SpéciauxSILER - Training course on seismic protection of lead-cooled reactors – Verona (Italy) – May 21-25, 2012

HOW TO ISOLATE A NPP ?S. DIAZ – NUVIA Travaux Spéciaux

Le Groupe NuviaSeismic isolation 1Présentation de SalvaremState of the art 2ActivitésIssues to be addressed 3Gamme de produitsDesign & safety 4Exemples de projetsIndustrialization 5

SILER - Training course on seismic protection of lead-cooled reactors – Verona (Italy) – May 21-25, 2012

Exemples de projetsInstallation on-site 6


1. Seismic isolationBehavior of base-isolated structure

1

Horizontal isolationResistance to vertical loading (without creep)

Resistance to horizontal displacement

Control of the horizontal displacement (flexibility and damping)


Springs with horizontal stiffness K

KM2T

Building mass M Principle of seismic isolationIsolate the motion of the superstructure from that of the ground by using flexible horizontal isolators (ASB).

ConsequencesLengthen and shift away the natural period from the high frequency range of the earthquakes (reducing the amount of energy transferred to the structure).

Reduce significantly the acceleration and thus the shear forces induced by the earthquakes in the structure (F = M x A).

BenefitsBuilding costs reduction

Reduce damages in structural and non structural components

12. Principles and benefits

K C


Elastomeric bearings (state of the art in the NPP)Choice of Chloroprene rubber (CR) for robustness

Main advantages: Re-centering of the structure Lesson learnt from other application (bridges, industry,

buildings) No maintenance All inclusive (damping + stiffness)

Major components Rubber layers : provide lateral flexibility Steel shims : provide vertical stiffness to support building

weight while limiting lateral bulging of rubber

Behavior law

21. Isolators


Sandwich metal – elastomeric rubber

Metal: metallic steel plates S235 prepared

Elastomeric rubber: raw elastomeric matrix made of :Elastomeric polychloroprene (CR)

Charges

Plasticizers

Activators

Protection agent

Vulcanizer agent

Accelerators

Vulcanization = temperature + pressure

CH2 C

Cl

CH CH2

polychloroprene

CH2 C

Cl

CH CH2=

chloroprene

==

1. Isolators composition 2


Elastomeric bearings main featuresBehavior Each elementary layer, subject to stresses and movements, deflects as shown in the three diagrams below :

Elastomeric bearings are assimilated to spring and damper associated in parallel.

22. Principles and benefits


3. References on nuclear facilities Koeberg NPP

Main data

- Eigen frequency of isolated structures : 0,75 Hz

- Dynamic Shear modulus Gd = 1,40 MPa

- PGA : 0,3g

- 1800 elastomeric bearings (2 power plants)

- Bearings dimensions : 700 x 700 x 130 mm

- Bearings coupled with friction flat sliders

- Lowering of acceleration : 2,7 to 7 times

Sliding surface

2


3. References on nuclear facilities Cruas NPP

Main data

- Eigen frequency of isolated structures : 1 Hz

- Dynamic Shear modulus Gd = 1,10 MPa (at construction time)

- PGA : 0,3g

- 3600 elastomeric bearings (4 power plants)

- Bearings dimensions : 500 x 500 x 66,5 mm

2


Jules Horowitz Reactor (JHR)

Main data

- Eigen frequency of rigid structures : 9 Hz

- Eigen frequency of isolated structures : 0,60 Hz

- PGA : 0,35g (hard soil conditions)

- 195 elastomeric bearings


- Damping ratio : 5%

- Dynamic shear modulus : Gd = 1,10 MPa

23. References on nuclear facilities


3. References on nuclear facilities International Thermonuclear Experimental Reactor (ITER)

Main data

- Eigen frequency of isolated str. : 0,60 Hz

- PGA : 0,35g (hard soil conditions)

- 493 elastomeric bearings


- Damping ratio : 5%

- Dynamic shear modulus : Gd = 1,10 MPa

2


3Key issues to be addressedThe isolation supports the nuclear island and the isolators are classified as safety important components. Even if the technology (construction method and isolators themselves) are well known, the following issue need to be addressed :

Design What are the code and standard applicable and what are the nuclear requirements ? How to deal with a long design life – durability demonstration and maintenance requirement - ?

Industrialization How to increase the quality control of the fabrication of standard product ?

On-site installation How to deal with the interfaces with the other construction lot ? What are the installation requirement ?


1. ASB – Normative contextTwo effective European norms for isolators

Prescriptive standards (« CE » labeled products)

No standard or guidelines for NPP but state of the art

Additional requirements for nuclear facilities are often added from designer

EN 1337Structural bearings

Static calculation criteria

Type tests and routine tests

Production tolerances

EN 15129Paraseismic bearings

Dynamic calculation criteria

Type tests

Production tests

Materials properties

Make distinction between: LDBR – damping <6% HDBR – damping >6% LRB with lead plug

4


2. Design criteria 4Common practice from previous references

Limitation of the total cumulative deformation and distortion to :

Limitation of the compression loading around 7 to 8 MPa

Mechanical data for the isolators properties to implement the FEM model:

Coming from actual tests on full scale ASB

Higher bound and lower bound properties including the aging effect and the deviations due to production

EN15129


3. Materials durabilityDurability of elastomeric bearings is a concern because :

Nuclear facilities’ life duration is great (70 years)

Mechanical properties of elastomers change over time

Tests are performed in laboratory to predict these evolutionsPrinciples are based on Arrhenius law

Treatment method in norm ISO 11346

Temperature speeds up physical and chemical changes (aging phenomena)

Impact on the project schedule need to be anticipated

90°C4,75 months

80°C9,5 months

70°C19 months

60°C38 months

50°C6,25 years

40°C12,5 years

30°C25 years

20°C50 years

T°CAging

Van’t Hoff law:Aging divided by 2 when T°C increases by 10°C

4


Principle of the testsAging phenomena affects chemical and mechanical properties of the rubber.

Key parameter of the experimentation : the shear modulus G i.e the tracer

Knowing the evolution of G, we can deduct the evolution the ASB behavior

Tests performed on both samples and full scale ASB

Description of aging tests (Arrhenius model)Regular measurements of shear modulus G

on pieces of elastomer exposed to various T°C

For a variation of X% in the shear modulus value,

we note the corresponding time for each isotherm.

43. Materials durability

∆G/G0

G = Shear Modulus

Time in hours


Description of aging tests (Arrhenius model)Combinations (t / T°C) are plotted on a graph log (t) = f(1/T).

If the accelerated aging follows Arrhenius model, all points should line up.

The slope of the Arrhenius line is proportional to the activation energy of the physicochemical reaction E (J/mol).

43. Materials durability


4Maintenance limited to standards requirements :

The preventive maintenance: based on visual regular inspections Normal inspection Principal inspection (more detailed including some measurements)

Additional requirements coming from regulators:Assessment of the actual mechanical properties of the isolators versus time: Full-scale and samples are kept in the same atmosphere as the real isolators

(samples remain also under compression) Using a zero point performed during the construction and before the loading,

testing are performed to validate the aging curve assumed for the calculation

Isolator replacement

4. Maintenance


45. ReplacementThe demonstration of the feasability of a replacement was part of the safety issues:

CRUAS lesson learnt: Bearing has been extracted from Cruas NPP in 1990 Civil works which need to destroy the top pedestal concrete

RJH/ITER concept Possibility to remove / change one isolator Method statement Load transfer Removal of the non-shrinkage mortar underneath the isolator Inflate and inject the flat jack

Before: fused mortar After: flat jack injected


EN standards require I.T.T (Initial Type Tests) i.e qualification of the isolators regarding different issues.

For JHR/ITER Project, test plan with parametric studies (> 1000 tests) during 2006-2008 in collaboration with French Safety authorities and CEA (French Nuclear Agency)

Mechanical properties variation studies (stiffness, damping) versus:

Solicitation parameters: frequency, distortion, creeping

Size of the sample: full scale test and samples (even sample location)

ageing: accelerated ageing (18 months equivalent to 70 years)

51. Qualification


Elastomeric Vulcanizing agent

Plasticizer Adds

Mixing

Raw materials mixed

Confection

Vulcanizing

Plates preparation

Plates Bonding agent

Plates prepared

Finishing Works

Calendaring

Protection

52. Manufacturing


The manufacturing process need to be control and assess according to nuclear safety issues which need the definition of quality related activities

Important process points are identified and checked at each steps and are part of the QA process :Follow-up documents filledTests performed (rheology on mixture, mechanical properties of mixture samples…)Measurements (thickness, mass, pressure and temperature of the press…)Monitoring (thermal gage inside each bearing)

3. QA & QC on factory 5


Tests are realized to control the fabrication deviation.

The key issue is related to the control frequency i.e test numbers and distribution that have huge impact on the project schedule.

For JHR/ITER, number of tests are sometimes higher than the EN standard but sometimes lower

The following tests are done :Compression tests (static & dynamic)

Shear tests (static & dynamic)

Shear adhesion tests

54. Production Tests


Jules Horowitz Reactor (JHR) / ITERContext

Installation requirements (mechanical tolerances vs civil works !)Flatness tolerances : < 0,1% (i.e. < 1mm/m) due to strong ratio vertical stiffness / horizontal stiffness

Void ratio criteria under steel plate : < 5%

+ =Grouted bearingConcrete pier C40/50

13001300

Elastomeric bearing + plates S355(1,5 T)

1100 1100

51. On-site installation requirements


Jules Horowitz Reactor (JHR) / ITER

On work-shop (constant height and parallelism):Monolithic sandwich assembly (same height)

Injection of a mortar (removable layer for replacement operations)

Tests on mortar (rheology, compression)

Follow-up documents filled

2. Pre-assembly on workshop 3


STEP 1 : Bearing installation

Flatness setting by the mean of 3 adjustable supports

Shuttering top of the pier

STEP 2 : 1st stage grouting (studs sealing)

Pouring of self-compacting concrete on 20cm (Foreva Premix C500®)

Flatness control before concrete hardening

STEP 3 : 2nd stage grouting

Pouring of non shrink mortar on 3cm (« Gravity Wave »)

Removing of forms and concrete finishing

5Jules Horowitz Reactor (RJH) / ITER

Innovated solution : 2 stages grouting (decoupling flatness and void requirements)

3. Installation on site


System installation Filling of the pocket with mortar

Non shrink mortarPEHD Pocket

Hot string

Foreva Premix C500 N

Homogeneous mortar

Bursting of the pocket by PEHD melting

5Jules Horowitz Reactor (RJH)

Focus on the « gravity wave » solution : gravity and laminar mortar flow

3. Installation on site


54. Full-scale mock-up


55. QA & QC on site


56. Interface with othersInterface with Main Contractor in charge of the civil structure:

Casting method for lower raft and upper raft could interfere with the installation on the isolators (method statement sequence)

Interruption of the erection for installation of the isolators for the Main Contractor

Connection interface (reinforcement layout / studs)

Services interface: Handling system for installation Storage of goods (pre fabrication and anticipation of the production)


5Jules Horowitz Reactor (RJH)

7. JHR pictures


5International Thermonuclear Experimental Reactor (ITER)

8. ITER pictures

Présentation Nuvia Travaux SpéciauxSILER - Training course on seismic protection of lead-cooled reactors – Verona (Italy) – May 21-25, 2012

New Build & Decommissioning DepartmentSébastien DIAZ92 cours Vitton69006 Lyon

[email protected]

+33 (0)4 72 14 44 90

+33 (0)4 72 14 45 09

How to isolate a NPP vC - · PDF fileHOW TO ISOLATE A NPP ? ... How to increase the quality...

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