tince2016 - following through the vercors mock-up construction - m. guichard, r. vénier, g. laou

3rd Conference on Technological Innovations in Nuclear Civil Engineering

Full paper Submission, TINCE-2016 Paris (France), September 5th – 9th, 2016

Following through the VERCORS mock-up construction

Martin Guichard1, Romain Vénier2, and Guillaume Laou3

1Project Engineer, Nuclear and Industry, Tractebel Engie / Coyne et Bellier, Gennevilliers,France ([email protected])2Project Engineer & Manager, Nuclear and Industry, Tractebel Engie / Coyne et Bellier, Lyon,France ([email protected])3Project Manager EDF DPNT-DIPDE, Marseille, France ([email protected])

Introduction

The VERCORS project (French acronym meaning “Realistic verification of the behavior ofreactor containments”) consists in designing and building a 1/3 scaled mock-up of the inner con-tainment of a French nuclear reactor P’4. The mock-up is a prestressed concrete building dedi-cated to research purposes. Its overall dimensions are: height 25 m, diameter 15 m, thickness ofcylinder wall 0.40 m.

Figure 1. Cross section of the VERCORS mock-up

3rd Conference on Technological Innovations in Nuclear Civil EngineeringTINCE 2016, Paris 5th to 9th September

Other structures of the project (external containment, additional building comprising devic-es for in-service monitoring, metallic structures) will not be dealt with in this paper.

The mock-up was designed so that its initial state (stresses in concrete containment wall)is representative of a real P'4 inner containment when just built. With the scale and accelerationeffects, the mock-up will enable the observation of concrete aging processes and the evaluationof the behavior of the structure in pressure test and accident situations ([MAS13]).

Tractebel Engie / Coyne et Bellier (TEF-COB) was commissioned by EDF to design themock-up and to follow through its erection, which erection was carried out in 2014-2015 by anassociation of companies led by the constructor Eiffage GC. The protagonists of the VERCORSproject during the erection are presented concisely on the sketch below.

MOeG / MOaD Project Manager / Client DeputyAMOeG Project Manager AssistanceMOeI Project Manager Assistance for the InstrumentationPROPEX Operator

Technical mattersTechnical and financial mattersOperating matters

Figure 2. Cross section of the VERCORS mock-up

MOeG is EDF DPNT-DIPDE, AMOeG is TEF-COB and Constructor is Eiffage GC.

Key to success in the mock-up erection is its representativeness, first criteria being thetime of erection and prestressing works, and the compliance with scaled-up construction toler-ances. This makes it necessary for TEF-COB, as AMOeG to adapt to the constructor’s proce-

MOeG / MOaDPROPEX

AMOeGMOeI

Constructor and its sub-contractors

Back officeBack-office


dures (such as [DES14]) and develop specific strategies for construction management and fol-low through.

To achieve all these objectives, a construction under particular constraints had to be com-pleted.

Figure 3. Global schedule overview of the mock-up construction


Key points to comply with general demands of representativeness

In addition to the common objectives of a construction follow through (respect of costs anddeadlines, concreting quality, checking of the reinforcement positioning/tying and other tradition-al geometry and functionality constraints), some particular points, detailed hereafter [KP], havebeen emphasized out during the construction of the VERCORS inner containment, as being es-sential to comply with the representativeness requirement.

Same initial state when just built and prestressed[KP1]To be respected, a limited time of erection of one year from the first concrete pouring(base slab) till the end of prestressing activities (due to the accelerated ageing) was im-posed. It demanded for the surveillance team:

1. A close surveillance of the schedule: tasks successions and sequences, re-quired documents (at approved status) before the starts of the several activi-ties.

2. The adaptation of the surveillance regarding the fast erection: reactivity, staffmobilization (permanent and support) in order not to alter the construction con-tinuity.

Besides, the drying of the inner containment had to be controlled during this constructionperiod by:

3. Maintaining a permanent curing on its walls, which had to be checked andtraced.

Scaling[KP2]In order to respect the scaling requests, the following elements had to be fulfilled:

1. Compliance with the design and the associated guide drawings which basicallycombine strict scaling of the P’4 inner containment and results of finite elementcalculations.- Close surveillance of the construction drawing (formwork, reinforcement,

tendons ducts lists, etc.).2. On site: strict compliance with the construction drawings and with low toler-

ances (see [KP3]). So that:- Not too few (structural matters) and not too much (representativeness mat-

ters) reinforcement is installed.- Formwork dimensions are strictly respected (global geometry).- Prestressing route of tendons are strictly respected.

3. Concrete pouring, and young age state surveillance:- Concreting quality considering the particularity of the specific concrete for-

mula: operability time, rheology (liquidity), compaction in congested areas.- Verification of the construction joint surfaces in terms of leak-tightness and

strength.- Survey of the early age cracking.

Restrictive tolerances[KP3]Examples of tolerances applied for the mock-up construction:

1. Rebars: +/- 10mm from one bar to the next or to any other2. Reinforcement cover: -0/+5mm3. Prestressing ducts : +/-10mm in 3 directions (radial, tangential, height in global

coordinates system)


Adapted methods of surveillance[KP4]The surveillance methods are adapted to the construction tolerances and the inducedconstruction methods implemented by the constructor (see examples in the followingparagraph). The surveillance team resort to its own land surveyor in order to doublecheck the works.

1. Prestressing ducts setting up:

Figure 4. Horizontal tendons ducts supports and position of prestressing tendons (commonzones of the cylinder wall, vertical cross sections)

- Control of the setting up points (topographical data of the constructor and/orthe surveillance team)

- Control of the supports in warehouse after fabrication- Control of the supports setting up on site compared to the setting up points- Control of the ducts’ orientations in compliance with prestressing drawings.- Control of the vertical ducts’ spacing and radial positioning at the top of eve-

ry lift. See Figure 9 and Figure 12.- Control of the vertical ducts tangential position (in the absolute coordinates

system) by the surveillance’s team land surveyor, randomly or for criticalareas (high deviations for example)

2. Reinforcement bars: 100% surveillance (diameters, spacing, positioning, laps,etc.) especially in the singularity zones (gusset, buttresses, penetrations, toricbelt, dome).

3. Formwork and geometry: control of main dimensions (wall thicknesses, liftheights) and topographical measures of some singularity points (toric belt fac-ets) before concreting authorization is given, occasional topographicalmeasures of the concreted lift (radius, heights).

4. Visits on site and communication with the constructor ([VEN14]):- Permanent presence of the surveillance team during the inner containment

erection with several visits each day: further to constructor’s notifications(hold points, for instance) or spontaneously.

- Daily formalized e-mails (considering the speed of the works: shift works(2x8h a day). due to schedule constraint: [KP1]-2 []), compiling all the re-


marks and demands of reworks discussed with the constructor during theday as well as listing the approved works and authorizations to proceed.All the remarks are precisely recorded in a table (with location, description,photographs, etc.) to follow that on site comments are taken into account,or to trace any deviations (see also [KP5]2)

- Observations sheets: stronger mean to insist on important remarks to beconsidered by the constructor.

- Weekly on-site meetings, more traditional communication means in whichshort term planning (3 weeks), global organization, documentation require-ments and technical subjects and methods are discussed.

Traceability of the construction[KP5]In order to collect all the monitoring data (about 700 sensors, 2km of fiber optic cables),to process at a later stage the construction data / events and in order to correlate them tonumerical models, EDF has designed a dedicated database (called “SAV”, French forSystem accompanying VERCORS mock-up).In addition to all the monitoring data recorded by the sensors, the surveillance team hadto collect a lot of other construction:

1. Constitutive materials characteristics (rebars, prestressing elements, concretedata for every truck mixers discharging on site).

2. Follow up of all the deviation through documents (Non-Conformance or Adap-tation Forms, etc.) with the exact localization of the deviation (time and space).

3. Construction data and events during erection.4. Verification of the record of finished work (accuracy and completeness).5. Etc.

Figure 5. Extract of the daily remarks table

Respect of key points are detailed below through two precise examples: a typical concretelift and the case of prestressing ducts installation in the toric belt and the dome.


Typical concrete lift

In this paragraph are described the main steps of construction of a typical concrete lift of the cylinderwall (instrumentation activities excluded) and the associated surveillance actions.

ACTIVITIES FOLLOWED THROUGH

1. Horizontal ducts positioning on “made tomeasure” supports

Figure 6. Horizontal tendons deviations (on the personalairlock)

Figure 7. Horizontal tendons (deviation-free area)

2. Inner side rebar layers positioning

Figure 8. Inner side rebar layers on a typical area

EXAMPLE OF SPECIFIC CONTROLS

Verification that prestressing route of tendonsare strictly respected ([KP2]-2) considering the[KP3]-3 tolerances.Example of adapted methods ([KP4]-1):- Control of the setting up points (constructortopographical data)- Control of the supports in warehouse after fab-rication

Figure 9. Control of supports in warehouse

- Control of the on-site setting up of supportscompared to the setting up points- Control of the ducts orientations in compliancewith the ducts layout drawings. Knowing the dis-cretization chosen during the design (differentducts’ radius lead to different ducts’ orientation)is here a great advantage, and it also helped theconstructor in the positioning.

Figure 10. Ducts layout drawing

100% controlled ([KP4]-2)

Check that exact amount of rebars is installedand in compliance with special requests as alter-nated ovellapping ([KP2]-2)

Respect of the tolerances ([KP3]-1 and 2)



3. Inner side formwork positioning

Figure 11. Inner side formwork positioning on a typical liftand near the equipment access hatch

4. Vertical ducts positioning

Figure 12. Radial positioning of the vertical ducts

5. Outer side rebar layers and stirrups position-ing

Figure 13. Outer side rebar layers and stirrups position-ing in a typical area


Formwork dimensions are strictly respected([KP2]-2 and [KP4]-3) :- Radius of the inner side formwork (topograph-ical data)- Thickness of the wall- Height of the horizontal upper face of the lift

Verification that prestressing route of tendonsare strictly respected ([KP2]-2) considering the[KP3]-3 tolerances.

Example of adapted methods ([KP4]-1):- Dimensions control of the specially made “fork”type support.- Control of the implementation of the support(topographical data and/or spacing verificationfor a given height compared to the theoreticalvalues. Here again being the designer helps- Verification of the good tying

100% controlled ([KP4]- 2)

Exact amount of rebars is installed and in com-pliance with special requests as alternated over-lapping ([KP2]-2)

Respect of the tolerances ([KP3]-1 and 2)



6. Outer side formwork positioning

Figure 14. Outer side formwork positioning (supported bythe outer containment)

7. Concreting

Figure 15. Concrete skip in action


Formwork dimensions are strictly respected([KP2]-2 and [KP4]-3) :- Thickness of the wall- Height of the horizontal upper face of the lift

Surveillance of the concrete pouring and walls atyoung age state ([KP2]-3)- Concreting quality considering the particularityof the specific concrete formula: operability time,rheology (liquidity), compaction in congsted are-as.- Verification of the construction joint surface interms of leak-tightness and strength- Survey of the early age cracking

Figure 16. Cracks survey

Concrete data collection for every truck mixersdischarging on site ([KP5]-1)


Prestressing ducts installation in the toric belt and in the dome

Ducts positioning in these zones is one of the difficulties encountered during the construc-tion as tendon routes change in the three special directions (contrary to cylinder area), in orderto connect cylinder wall tendons ducts to dome ducts.

The surveillance team decided to organize a dedicated control of this positioning whileguaranteeing the succession of the many different tasks to be done by the constructor. This con-trol is described below.

Regarding tendons routes, this zone is particularly complex as vertical and dome tendonsare anchored in it and “gamma-shaped” tendons turn over from their vertical part to their domepart.

Figure 17. Ducts and reinforcement in toric belt

Figure 18. Ducts positioning in the dome


ACTIVITY FOLLOWED THROUGH

8. Setting up of the supports in the toric belt

Figure 19. Ducts vertical supports to be implanted

Operations carried out by the land surveyor ofthe constructor:- Setting up of the vertical supports- Setting up of the tangential supports on thevertical supports by matching topographicalpoints marked (radially and tangentially)

Potential corrections of the supports with newtopographical survey of the corrected supportsby the constructor

9. Positioning of the ducts on their supports- Pre-Positioning

Figure 20. Ducts on their supports (lift 15)

- Tying and continuation to the next steps

10. Operations in the dome (corresponding tooncrete lifts 16 and 17)Same as for the toric belt, except that the verti-cal setting up is replaced by a positioning basedon the inner side facing of the dome. The sup-ports are circumferential for the lift 16 andarched for the lift 17 (see Figure 22).

EXAMPLE OF SPECIFIC CONTROL

Topographical control of the setting up by the landsurveyor of the surveillance team ([KP2]-2, andconsidering the [KP3]-3 tolerances)

Figure 21. Topographical control of the ducts sup-ports in the toric belt (lift 15)

Nota: All theoretical coordinates are computed bythe designer (TEF-COB) which allows a prelimi-nary control of the “working documents” of theconstructor.

Validation of the orientations in compliance withthe ducts layout drawings ([KP4]-1)

Figure 22. Tendons routes of the dome with theirsupports (green)

All these activities had to be carefully planned andcoordinated in order not to alter the tight schedule.


Conclusion

Throughout its surveillance, the team encountered some difficulties: The scaled structure. Reinforcement, prestressing and monitoring elements (sen-

sors) constituted a very dense amount of elements which position proved difficultto change after being implemented on site. The surveillance team tried to guidethe constructor as much as possible to the better arrangement of the componentsall together in the formwork and prevent them from possible damages. For exam-ple: positioning of the rebars in relation with tendon routes helped to position thestirrups and not to damage some fiber optic cables.

The fast schedule imposed: a typical lift was raised and concreted in one week.At that time of the construction, the constructor worked in shifts (2x8h a day).Thus, the surveillance team had to follow and to have the required reactivity (au-thorization to proceed, etc.) without disruptin the schedule.

In addition, adaptation of the surveillance to the constructor procedures appeared as beingessential. Working in close collaboration with the constructor (preparation meetings, exchangeson procedures), was necessary for a fast and smooth succession of tasks. It also appeared thatbeing both designer and surveyor proved being an advantage for TEF-COB. Global knowledgeof the structure and pre-identified difficulties (especially for the prestressing tendons installation)helped a lot, as is described in this paper.

VERCORS mock-up erection has been completed in October, 2015, and the structure un-derwent its first and second pressure tests successfully (in November 2015 and January 2016).In particular, it has to be said that no major problem occurred during prestressing operations (nobreak of strands), no particular leak points due to construction faults, etc…Erection quality andplanning have been respected due to the deep involvement of Eiffage GC, EDF and TEF-COBteams working on the project.

References

[MAS13] Masson, B. and Alliard, P.-M. (2013), « Objectives and design of the new experimentalprogram VERCORS based on a 1/3 scaled PWR containment building », Technical Inno-vation in Nuclear Civil Engineering (TINCE 2013)

[DES14] Dessagne, M. and Peigner, J.-D. (2014), « Maquette VERCORS – Construction – Pro-cédure de réalisation de l’enceinte interne », Construction procedure

[PEI15-1] Peigner, J-D '(2015) « Maquette VERCORS – Construction – Procédure de réalisationde la ceinture du dôme de l’enceinte interne », Construction procedure

[PEI15-2] Peigner, J-D '(2015) « Maquette VERCORS – Construction – Procédure de réalisationdu dôme de l’enceinte interne », Construction procedure

[VEN14] Vénier, R. and Guichard, M. (2014), « Programme de surveillance des travaux de lamaquette VERCORS », Report


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Topic: 1 - Advanced Materials 2 - Design and Hazard Assessment 3 - Civil Works Construction 4 - Long Term Operation & Maintenance 5 - Dismantling of civil works & Civil Works in Hostile Environment 6 - Geotechnical Design & Construction & Fluid Structure Interaction

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