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Construction Technologies related to Site Preparation, Civil and Structural Works

Azhar KhanManager, EC 6 Containment Design / Constructability, AECLJune 2011

IAEA Workshop on Construction Technologies for Nuclear Power Plants

Hosted BY SNPTC, Shanghai, ChinaJune 22-24, 2011

Scope of Presentation

Project and Construction Schedule

Site Preparation

Construction Technologies for Civil and Structural Works

Construction technologies for Nuclear Power Plant Buildings

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Overall Project Schedule

Construction Schedule

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Site Preparation

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Background to Site Planning and Development

• Phases of site planning and development works:– Advanced site development– Supply-chain infrastructure– Off-site management for module fabrication– Module delivery, assembly and outfitting– Power island construction

– Open top construction:

– Need at least 1 VHL crane– Modularization and prefabrication:

– Fully developed site infrastructure to support offloading , assembly and outfitting to exact standards before first nuclear concrete.

– Module lay-down areas to be “hardstand”, fully trafficable and heavy load capable.

– Support facilities required for off site module fabrication and module assembly

– Large area needed for storage, prefabrication and pre-assembly of modules

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Site Development Schedule

• Site development affects construction schedule:– If lay-down areas are not available for storage, prefabrication

and pre-assembly of modules - site construction schedule will be affected

– Excavation of power block to be completed before site development

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Pre-requisites for Site development and Plant Construction

• It is recommended that the following be completed prior to commencement of site development and plant construction:

– Subsurface (soils and bedrock) testing and analysis to assess site optimum location

– Environmental assessment– Site survey, and site survey control programme established– Transportation study for modules, equipment and personnel– Upgrades and load testing of routes required to handle heavy loads of

existing roads, bridges or overpasses and barge offload facilities– Significant cuts and fills necessary to provide a flat and level site free of

encumbrances and obstructions– Design for both permanent and temporary construction facilities– Electronic three dimensional (3-D) model for all permanent and

temporary sites, structures and components– Site drainage, trenching for utilities– Site development schedule– Excavation plan

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Pre-requisites for Site development and Plant Construction, cont’d.

– Temporary services facilities and assembly areas– Site development permits, licensing documentation for site

preparation and construction licenses– Procurement of equipment and facilities required for site

preparation– Develop quality assurance program

– Quality Assurrance procedures– Quality surveillance procedures/check lists– Quality control procedures/check lists

Methods Utilized for Site Infrastructure Implementationand Layout for Site Construction

• All weather construction method:–Construction environment isolated from ambient weather–Buildings have temporary enclosures – Qinshan CANDU–Open top Construction

• Methods for construction personnel mobility:–Scaffolding–Mobile scissor lifts, bucket trucks–Access to personal services (tool sheds, toilets, wash water)–Mobile communication systems

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Methods Utilized for Site Infrastructure Implementationand Layout for Site Construction, cont’d.

• Transportation:– Stick build approach– Modularization approach– Combined approach– Heavy haul path– Need barge unloading facility and heavy haul road(s)– Railroads

• Site mapping and measuring:–Existing conditions including topography–Existing buildings and infrastructure–Existing underground infrastructure–Layout of reference points and markers–Laser and global positioning system mapping (GPS)

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Methods Utilized for Site Infrastructure Implementationand Layout for Site Construction, cont’d.

• Three dimensional modeling:– It can be developed during early design stages so that the entire

plant can be designed using available software– There would be cases where the vendor already has a design with

approved two dimensional (2-D) drawings that need to be partially modified to account for country specific requirements.

– In such cases, it is recommended that the design drawings are input to the 3-D modelling software to derive the required modifications.

– The only disadvantage in using 3-D modelling is that considerable time is needed to develop interference-free plant layout, to work out the BOM to be procured, and to develop ‘working drawings’ to be used in the field.

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Main Construction Facilities

• Construction management centre:– Use the latest technology to provide direction and control of real time

field activities, tracking of equipment, visual and daily debriefing with field personnel

– Video conferencing– Real time management of critical path

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Main Construction Facilities, cont’d.

• Civil:– Computerized concrete batch plants:

– Good quality concrete on a continuous basis with no human error

–Concrete/materials testing laboratories–Embedded parts fabrication shop–Reinforcing steel fabrication shop–Shop fabrication mock-up:

– Full scale or partial scale mock-ups can save on actual work time

–Structural steel fabrication/assembly shop–Paint shop–Contractor building–Warehouse–Housing for staff

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Main Construction Facilities cont’d.

• Mechanical/Piping:–Pipe fabrication shop–Pickle bath facility–Paint shop–Contractor building–Warehouse–Housing for staff

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Main Construction Facilities, cont’d.

• Electrical, Control and Instrumentation:–Electrical cabling shop–Instrument calibration shop–Contractor building–Warehouse–Housing for staff

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Main Construction Facilities, cont’d.

• Owner:–Material management centre–Technical and administration building–Lay-down and assembly areas(modules, liner vessels,

equipment)–Warehouse–Housing for staff–Transportation depot–VHL crane–Tower cranes and telescopic cranes–Construction control room–Construction parking–Security fencing, gates and building

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Main Construction Facilities, cont’d.

• Owner cont’d.:–Temporary power–Fire protection water and service water–Housing for staff–Transportation depot–Cafeteria for workers–First aid station

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Construction Technologies for Civil and Structural Works

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Civil and Structural Works

• Civil and structural works comprise the construction (fabrication, manufacture) of buildings, structures and their components and the supply of yard services (drainage, fencing, etc.)

• Longest duration on project schedule• Hence important to optimize by using advanced methods that

reduce the schedule• Very difficult and very time consuming to correct mistakes

–Quality assurance program is critical

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Civil and Structural Works cont’d.

• The civil and structural works comprise the following:– Site clearing, grading and surveying; – Site protection works against flooding, tidal waves, typhoon, tsunami, etc.;– Excavation;– Earth soil/rock removal and disposal;– Site dewatering;– Remedial measures on foundation soil/rock;– Rock and soil slope stabilization;– Building under drainage;– Foundation works;– Building peripheral drainage;– Concrete works above foundation;– Structural steel fabrication and erection– Yard services– Backfill works– Roads and landscaping– Permanent security construction

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Excavation

• Requires permits from local jurisdiction prior to start• Requires construction license from regulator prior to start in some

countries• Activity of long duration that can last between 6 to 12 months• Sometimes adjacent to operating nuclear power plants• Environment regulations and constraints• It is essential to minimize damage to final foundation material:

Protection from blasting near final level• Protection from flood and freezing• It is essential to provide protection to workers• It is essential to provide protection to nearby facilities

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Excavation Cont’d.

• Conventional method:–Uses light machinery, blasting and hand excavation.

• Advance method:–Precision line blasting;–Chemical foam expansion for breaking rock.

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Confirmation Of Soundness OfFoundation Materials And Remedial

Measures

• Visual examination– Identification of weak areas

• Open pit load tests to confirm foundation materials• Conventional remedial measures:

– Extra excavation to overcome weak areas;– Thicken and/or enlarged sub-base engineered to reduce differential

settlement and tilt of buildings.• Advanced method:

–Consolidation grouting;–Rock anchors;–Bridging of weak areas;–Instrumentation to measure differential settlement and tilt of

buildings.

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Remedial Measures For Slopestabilization

Objective:–Safety of workers, equipment and project assets during the

construction phaseConventional methods:

–Reducing slope of cuts–Use of anchored steel mesh

• Advanced methods–Consolidation Grouting–Grouted rock anchors–Earth reinforcing

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Concrete Types

• Responsibility of site engineering to develop the specified mix designs• Nuclear plants are using more concrete; Hundred of thousands of cubic meters• Functional & performance requirements of buildings are different hence it is

economical to specify different mixes• Concrete mixes should be developed and approved at least 6 months before

concreting program• Supply of constituent materials (aggregates, sand, water, fly ash, etc) must be

confirmed a minimum of 12 months before start of concreting program• Portland cement is normally used• Heavy shielding concrete• Higher performance concretes (45-60 MPa) are being specified recently for

containment buildings

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CONCRETE TYPES cont’d.

• Conventional Concrete Mixes– Portland cement– 25 to 35 MPa– Heavy shielding concrete

Advanced Concrete Mixes:– High workability concrete;– High performance concrete: 45 to 60 Mpa;– Fly ash concrete; large volume pours;– Pervious or “no fine” concrete;– Pre-cast concrete;– Self-Consolidating Concrete;– Self levelling concrete.

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Concrete Placement Methods

• Conventional placement method:– Use of buckets and tower cranes to place concrete

• Advanced Concrete Placement Method:– Concrete placed with pumps

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Bonding Between Concrete Pours

• Conventional method:– Expose aggregates to receive the next pour

• Advanced method:– Green cutting

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Reinforcing Steel

• Conventional reinforcing steel method:– Placing steel bars with lap splices– Bar size 44 mm and above are connected by exothermic welding

• Advanced reinforcing steel methods:– Using mechanical & cad weld splicing– T-headed shear bars– Use of automatic rebar tie machines– Large prefabricated rebar modules

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Embedded Parts

• Conventional embedded parts:– Plate type with manually welded strips or studs for anchoring in

concrete– Embedded anchor bolts for equipment and structural steel– Penetrations for piping and conduits

• Advance embedded parts method:–Plate type with studs welded with stud gun–Steel plate reinforced walls: Supports are connected directly

to the plate

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Expansion Anchors

• These are anchors drilled into concrete to support structures, systems and components

• Objective:– Should reduce the use of expansion anchors to only support conduits and

non-seismically qualified systems and non vibrating equipment– Anchors should not cut reinforcing steel

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Foundation Construction

• Conventional foundation construction methods:– Spread footings, combined footings, mat foundations, pile

foundations– In the case of mat foundations, multiple pours are used

• Advanced foundation construction methods:– Advances in concrete technology and placement methods have– led to single pours for large mats– Advances in the development of seismic isolations permit the– isolation of foundations for structures and equipment and thus– protect them from high seismic events

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Foundation Construction – Seismic Isolators

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EC 6 for High Seismicity Regions;Common Reactor Building and Service Building Foundation,

Lower Base Slab c/w Isolator Pedestals

Foundation Construction – Seismic Isolators cont’d.

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Concrete Construction Above Foundation

• Formwork• Conventional formwork:

– Slab formwork consists of wood/metal forms supported by shoring– Wall formwork consists of wood/metal face forms held together with

form ties– Forms are stripped after concrete has set and achieved sufficient

strength so that it can support its dead load plus a small live load• Advanced types of formworks:

– Q-deck or left in shutters– Steel plate reinforced walls (no reinforcing steel in walls)– Steel plate modular floors– Pre-fabricated permanent formwork

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Walls & Columns

• Conventional Method:– Place conventional form and pour concrete through trunks up to

height of 6 to 7 meters.• Advanced Construction:

– Steel plate reinforced walls;– Self consolidating concrete;– Self levelling concrete.

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Slab, floors and roofs

• Conventional Method:– Use conventional concrete mixes, conventional reinforcing steel with

lap splicing, conventional formworkAdvanced Method:

– Use Q-Deck or left in shutters in slabs not supporting seismically qualified systems

– Modular floors– Steel reinforcement concrete composite structures and Deck Plate

construction– Self compacting concrete– Pre-fabricated permanent formwork

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Structural Steel Fabrication

• Braced frames consisting of columns, beams and bracing, and equipment supporting steel systems

• Conventional method– Cutting and welding of structural steel based on two-dimensional

fabrication drawings and using manual measurements– Use of clip angles– Maximize welding in shop

• Advanced method– Automated fabricating shop– Use of 3D and precision control maintained by lasers– Use of end plate connections

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Structural Steel Erection

• Conventional method:– Use of temporary bracing to align and temporarily support the

braced frame structures– Use of conventional high strength steel bolts using torque method

such as turn of nut and calibrated wrenches – Maximize bolting and minimize welding at site

• Advanced method:–Facilitates modularization and parallel works–Use of buckling restrained braces (BRBs)–Use of twist off bolts

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Water Proofing

• Required for underground structures, basements, large water transporting system, liquid retaining concrete tanks, etc.

• Conventional method:– Use of rubber water-stops– Use of external painted waterproofing on structures below ground– Use of sump pump installation

• Advanced method:– Use of superior waterproofing material with advance spraying

system– Use of fast setting epoxy injection material

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Backfilling

• Used for areas between open cut and buildings;• Used in pipe trenches• Used in landscaping• Conventional method:

– Common backfill in open area– Granular backfill adjacent to building and covering piping in trenches

• Advanced method:–Cement / sand backfill mixture is used

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Yard Services

• Storm water drainage system• Sewage system• Plant system, piping and cables• Plant roads• Conventional method:

– Backfilled trenches• Advanced method

–Tunnels

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Construction Technologies for Nuclear Power Plant Buildings

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CONTAINMENT BUILDING

• Foundation base slab + steel liner• Containment vessel or steel lined concrete• Containment wall + dome• Shield wall (in double containments)• Internal structures

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FOUNDATION BASE SLAB + LINER

• Large reinforced concrete mat foundations (greater than 5000 m3)• Waterproofing membrane under foundation• Conventional Method:

– Multiple pours, placed to minimize shrinkage– Conventional concrete design mix

• Advanced Methods:– Single pour due to improved concrete technology / concrete mixes

with low shrinkage cement, reduced cement content, increased use of plasticizer admixtures, etc.

– Significant increase in concrete pump use– Increased reliability of batch plants

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BASE SLAB

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Example of RB Base Slab Rebar Mat

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CONTAINMENT WALL

• Conventional Method:– Use pre-assembled gang wall forms & construct in multiple repetitive

concrete lifts between 6 to 7 meters– Concrete placement using trunks to pour concrete; not greater than

1 meter fall– Use vibrators for achieving homogeneity– Carpenter crews are employed for erecting forms– Large scaffolding to set up

• Advanced Method:– Slip-forming:

– Continuous placing of concrete at pre-planned rates– Hydraulic lift with jacks moving short section of formwork

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Climbing Formwork

• Climbing formwork is a self supporting formwork system.

• Standard steel forms supported from frame

• After wall is poured, form is released and rolled back from face

• Jacks lift or climb the whole frame up one level

• Prefab rebar installed• Formwork panels are closed and next

concrete wall is poured• Standard cycle times

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CONTAINMENT WALL SLIP-FORMING cont’d.

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CONTAINMENT WALL SLIP-FORMING cont’d.

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CONTAINMENT WALL SLIP-FORMING cont’d.

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CONTAINMENT WALL SLIP-FORMING cont’d.

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CONTAINMENT WALL cont’d.

• Advanced Method cont’d.:– Jump forming:– This method is being used to construct practically all steel lined

containment walls– Wall is formed in stages with the form lifted hydraulically or “jumped

up” to the next stage after concrete has reached sufficient strength– Use of prefabricated rebar modules

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Jump Forming

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Jump Forming in Parallel withLiner Construction and Installation

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Jump Forming and Prefab Rebar Mat

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Completion of Jump Forming

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CONTAINMENT DOME

• Conventional Method:– Support formwork:

–Uses a space truss system and shoring supports from the base slab

• Advanced Method:– Use a permanent steel plate dome formwork, lifted into place with a

VHL crane– Jump form the dome– Use of prefabricated rebar modules

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CONTAINMENT DOME cont’d.

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INTERNAL STRUCTURES

• Conventional Method:– Use preassembled gang wall forms or hand set forms and construct the wall

in multiple repetitive lifts– Construction is up to underside of slabs, construct slab and then proceed

with columns and walls up to next slab– Conventional concrete mixes are used– Scaffolding is supported from the base slab and subsequently from the next

slab

Advanced Methods:– Use Q-deck or left in shutters supported by steel beams, for slabs not

supporting seismically qualified systems– Self consolidating concrete– Self levelling concrete– Proposed methods are to use modular floors and modules with mechanical

and electrical systems. These activities are performed off site and subsequently, the modules are transported to site and installed with a VHL crane

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TURBINE BUILDING

Significant activities are:– Excavation (significant at coastal sites with large tidal variations)– Dewatering system– Base Slab– Turbine generator Pedestal– Structural Steel– Building Crane (200 tons or greater);

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TURBINE BUILDING

Conventional Method:– Base slab is constructed in multiple pours;– For concrete structures use preassembled gang wall forms and

construct the wall in multiple repetitive lifts;– Turbine generator pedestal is concreted similar to other concrete

structures;– Structural steel is erected with conventional method of erecting

braced frames, stabilizing with temporary or permanent braces– Roof trusses are installed on columns after being preassembled on

ground;– Building Crane is lifted in to place with a heavy lift transportation

crane.

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TURBINE BUILDING cont’d.

Advanced Method:– Base slabs – single pour or larger pours– Concrete structures – left in shutters, pumped concrete– Turbine pedestal – seismic isolators and self consolidating concrete,

pumped concrete– Structural Steel – modularized and installed with heavy lift crane,

use of buckling restraint braces, twist off bolts– Turbine building crane – installed with VHL crane

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Turbine Building Excavation

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TURBINE BUILDING CONSTRUCTION

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Turbine Building Construction

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Turbine Building Base Mat

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TURBINE BUILDING CONSTRUCTION

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Prefabricated Rebar Mat

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Wall Rebar Mat

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