• Advanced High Temperature Reactor (AHTR)

    NSE is appointed by Eskom to develop a concept design for the Advanced High Temperature Reactor (AHTR). The concept design focused on the Prestressed Concrete Reactor Vessel (PCRV), the nuclear power plant building layout and the assessment of potential sites on the Necsa Pelindaba facility. The operating pressure and temperature of the reactor is 9 MPa and 1200°C, respectively whilst the maximum operating temperature of the PCRV is restricted to 65°C during normal operation.

    • The PCRV was analysed primarily for temperature and pressure loads associated with normal and operating conditions
    • An investigation is being developed into the use of refractory concrete for use in the PCRV. The objective is to provide a concrete vessel which has increased resistance against temperature transients which could result in cracking and reduced strength of conventional concrete
    • A licensing strategy is in progress for the AHTR to capture the differences between gas cooled reactors and LWR
    • Excavation options are being considered to find an optimum layout between depth of embedment and height of the nuclear building which will be exposed to external hazards
    • Site investigations have been performed on the Necsa Pelindaba site to identify suitable brown field areas which can be used for the construction of a proof of concept plant

  • Bulk Stores Cask Storage Slab

    Eskom appointed Nuclear Structural Engineering for the design and specification of a cast-in-situ concrete slab 36 m x 28 m at the Bulk Stores Complex at Koeberg NPS. The slab is designed to support 12 unloaded spent fuel storage casks on grade each having a mass of 113 t distributed over an area of 6.5 m x 4.5 m. The slab perimeter on the Eastern and Southern sides have 3.5 m high masonry walls with support columns.

    • The design includes basic soil tests on the cohesionless sands in the form of DCP tests to estimate static soil properties and to determine ground compaction requirements
    • Loading was applied to the structure by using the cask loading sequence specified by Eskom
    • The figure illustrates the layout for all casks together with the crane outriggers having 2.5 x 2.5 m spreader pads
    • Concrete thickness 375mm, of which 300mm is regarded as structural and the 75 mm is a screed for creating the required runoff slope. The rebar provided is Y16 @ 250 mm
    • 125mm and 75 mm cover top and bottom respectively, to enhance durability. The additional cover on top is to allow for a 90mm saw cut while maintaining a minimum of 30mm cover
    • Design codes used include ACI 318-11 (2014) for the reinforced concrete works, ACI 530-02 for the masonry walls and SANS 10160-3 (2010) loading code

  • Cask drop accidents

    NSE is appointed by Eskom to investigate postulated drop accidents when the spent fuel casks are lifted into the Cask Loading Cell (CLC), Cask Cleaning Cell (CCC), and Zero Metre Loading Bay (ZLB).

    • The investigation focuses on the effect of a postulated 0.5 m perpendicular drop of a 113 ton and 122 ton cask on the support slabs in the CCC and CLC
    • A finite element model of the CCC depicts the reinforced concrete structure (blue), the Expanded Polystyrene (EPS) (red) and the low density foam concrete (brown)
    • The investigation of the ZLB slab focuses on the effect of a 0.5m perpendicular drop of a 122 ton cask onto the transport trailer which is parked on the slab
    • The ZLB non-linear finite element model shows the cask cradle, 31.5m2 trailer bed, trailer axles, wheel rims, and tyres that were modelled in order to consider the effects of stiffness and damping of the various components of the trailer
    • The impact analysis was conducted using a non-linear transient solver in order to determine the Demand / Capacity ratios in the reinforced concrete slab, for both flexure and shear loads

  • Geotechnical investigation and seismic hazard assessment

    The C3-C5 building on the Pelindaba Site was identified as a possible location for the production of fuel spheres for the Pebble Bed Modular Reactor (PBMR). NSE was appointed to undertake the structural re-qualification of the building and in doing so, required a geotechnical assessment of the site as well as an up to date seismic hazard assessment of the site. The nature of the work involved the use of various specialists in the geotechnical field including geologists, geophysicists, seismologists and dating laboratories

      The scope of work undertaken by NSE’s personnel on this project included:
    • The development of an investigation programme which would characterise the site for the structural and seismic analysis of the facility. In addition, SHEQ documents were developed and approved by Necsa
    • Conventional geotechnical tests were performed and laboratory tests undertaken to characterise the near surface deposits. All testing was performed in conjunction with the NSE Quality management System
    • Two deep boreholes were drilled to a depth of 100 m. Logging of the core was performed as the drilling proceeded. On completion of the drilling P and S wave velocities were measured by suspension logging. Surface waves were generated by a truck mounted shaker
    • The suspension logging was complimented by acoustic televiewing which provided information on the jointing of the bedrock
    • A level 2 seismic hazard assessment was performed in accordance with USNRC RG 1.208. This effort was led by PC Rizzo & Associates. As the site was located close to the Brits Graben trenching was undertaken and samples removed for thermo-luminescence dating in specialist laboratories. The dating exercise resulted in an estimation of last movement on the Graben
    • The level 2 PSHA resulted in an estimation of the seismic hazard at probability of exceedance ranging from 10 E-2 to 10 E-6 per annum. Ground motion response spectra were developed at the top of weathered rock together with acceleration time histories
  • Civil/Structural Design Services for Nuclear New Build to Eskom

    NSE provided civil and structural engineering design services to Eskom Enterprises on the three potential Nuclear New Build sites. The sites are green fields and the EIA for each is in the process of being completed. Aspects of the sites related to external hazards, geology, geotechnics, demographics and access were also in the process of being completed as part of the Site Safety Report. The three sites were investigated for the optimum number of reactor units for each of the potential vendors and the civil works around these developed accordingly for each vendor. Schedules, Work Breakdown Structures and Cost estimates were also prepared

      The scope of work undertaken by NSE’s personnel on this project included the following:
    • Reviews of the EIA investigations and the incorporation of the recommendations into the site layouts and design
    • Participation in the estimation of the seismic hazard assessment of the Thyspunt Site
    • Review of the external hazard, geotechnical, geologic, traffic and other investigations for incorporation into the Site Safety Report
    • Optimisation of the reactor layouts for the various nuclear island vendors on each of the sites
    • Optimisation of the earthworks and terraces for each site to minimise the quantities of excavated and imported materials
    • Concept and basic design of the roads, stormwater, potable water, clean, grey and dirty water systems
    • Concept design of the cooling water intake and discharge systems
    • Architecture, concept and basic design of the buildings comprising the balance of plant
    • Concrete mix design
    • Participation in the development of the WBS and schedule
    • Development of working procedures for the civil and structural design work

  • Civil/Structural Expertise to Federal Authority for Nuclear Regulation

    NSE is currently providing civil and structural engineering expertise to the Federal Authority for Nuclear Regulation (FANR) in the United Arab Emirates. This service is provided via Lloyd’s Register EMEA/Lightbridge who also provide engineering experts with nuclear experience from various disciplines to FANR. FANR is performing the regulatory function on the site of the 4-Unit Barakah Nuclear Power Plant, located 300 km from Abu Dhabi, UAE. NSE was appointed in 2015 for a contract period of 3 years, to perform quarterly inspections, or on an as-needed basis

      The scope of work undertaken by NSE’s personnel on this project included the following:
    • Reviews of civil engineering project specifications for safety related structures
    • Reviews of working procedures and on-site compliance of the Contractor to these procedures
    • Site inspections of construction activities for safety class structures
    • Reviews of the Plant owner and Contractor’s quality surveillance activities and records
    • Checking compliance of the quality surveillance documentation to the project quality assurance (NQA 1) and control requirements
    • Checking compliance to the applicable international codes or practice, and regulatory guide documents
    • Concept design of the cooling water intake and discharge systems
    • Checking compliance with the construction drawings and construction procedures
    • Providing civil engineering support to FANR resident inspectors

  • Polar Crane Deflection Analysis

    As part of an ongoing operation to extend the design life of the nuclear power plant, Eskom is upgrading various structures. Part of this operation includes the replacement of the Steam Generators (SGs) in the Containment Buildings for both Unit 1 and Unit 2. NSE has been appointed by Group Five Construction (Pty) Ltd to analyse and assess the deflection of the Polar Crane’s main girders with the new SG loading at prescribed locations. The objective of this study is to calibrate the polar crane finite element model as accurately as possible, to reflect deflections of the main girders to correspond to that indicated in the test load certificates. Thereafter, the objective is to analyse the deflection of the polar crane with the new SG loading

    • The Assessment involves the analysis of 28 steel platforms using appropriate nuclear design codes
    • The platforms were assessed in terms of their member strength and member serviceability
    • In addition to the member checks, connections were assessed based on the results of the internal forces obtained from the member analysis
    • There were 7 levels of platforms that had to be assessed i.e. the 8m, 10m, 16m, 20m-Annulus, 22m, 26m and the 30m levels
    • Figure 1 and Figure 2 represents a typical layout of the platforms in Unit1 on levels 10m and 16m for SG number 1
    • NSE utilised RFEM to construct finite element models, ensuring correct member types, loading and restraints at the connections
    • Figure 3 represents a typical display of the results for the platform member strength check. The figure was extracted from RFEM
    • SANS 10160 Part 1 and SANS 10162-1 were used to assess the members for code compliance.

  • Design check of Steam Generator Platforms

    Eskom are in the process of doing extensive modification to various structures at Koeberg Nuclear Power Station as part of an ongoing operation to extend the design life of the nuclear power plant. Part of this operation includes the replacement of the Steam Generators (SG) in the Containment Buildings for both Unit 1 and Unit 2. Scaffolding will be used to remove the SG platforms which surround the SG’s at various heights. NSE has been appointed by Lesedi Nuclear Services (LNS) to analyse and assess the SG platform structures for compliance to applicable structural design codes according to the loading given by LNS

    • NSE created finite element models ensuring correct member types, loading and restraints at the connections
    • The finite element models were analysed using the software Strand7
    • Figure 1 represents the Polar Crane with the original trolleys. Figure 2 represents the Polar Crane with the Temporary Lifting Device (TLD) modelled only by its wheel positions
    • The Calibration was done with the original deflection test certificate and the results showed a margin of error less than 3 mm (< 10%)
    • Figure 2 shows the model used for the deflection analysis of the Polar Crane for the TLD and new SG load. This was one of three location that was analysed
    • Figure 3 shows the results of the deflection analysis of the first TLD position with 20% of the new SG load
    • The maximum deflection occurred at position three where the TLD is directly at the centre of the polar crane and with 100% of the SG load

  • Geohazard Assessment of the Sinop NPS, Turkey

    NSE is appointed by TUV Rheineland / Risktec to review the geohazards on the Sinop NPS, Turkey in support of the site confirmation studies. Geological, geotechnical and seismic hazard studies have been performed over the past 20 years and these historical documents form part of the input data which will be complimented by an in-depth geotechnical / geophysical site investigation which is currently in progress. The current investigation programme incorporates both in-situ and laboratory testing of the overburden deposits and the volcanic tuffs and basalts covering the site

    • Geohazards comprise natural and engineered geotechnical related hazards that can affect the safety of a Nuclear Power Plant (NPP). The geotechnical parameters and associated analyses quantify the hazards associated, inter alia, with slope stability, liquefaction, ground subsidence / collapse using the software Strand7
    • The evaluation of the representative geotechnical parameters of the various geologic horizons underlying the NPP site, in conjunction with an assessment of the various external hazards and environment restrictions on the site, advises the preferred horizon on which the NPP should be founded
    • Geophysical tests have been interpreted to check for the existence of Karst structures
    • In addition to the geotechnical investigations, ambient noise measurements are being recorded to develop V/H ratios for use in the seismic specification. The downhole, crosshole and suspension logging measurements will inform the shear wave velocity profile
    • Geotechnical ground profiles will be developed on completion of the current site investigations for use in the site response analysis and bearing capacity / settlement calculations for the power plant
    • Statistical variations in the various geotechnical parameters currently being measured will be developed for design

  • Development of a Small Modular Reactor in Canada

    NSE is appointed by USNC to develop a concept design for small modular reactor (SMR) with specific attention to the licensing requirements, design basis, design criteria, building and facility layout, and site selection. Structural analyses include the development of floor response spectra for the confinement taking into account soil structure interaction and varying properties of the soil which should incorporate a range of potential sites

    • Design criteria have been developed as per the requirements of the Nuclear Regulator for Canada and include the design basis and beyond design basis for which the power plant will be designed
    • A plant layout is developed for both the nuclear and non-nuclear parts of the power plant and security measures implemented as part of the safeguards
    • Due to the climatic restrictions on construction, a modular approach is being adopted in the concept design which includes the use of precast and post tensioned concrete
    • Initial seismic, wind / tornado and aircraft crash analyses incorporate ranges of soil / rock properties so that the soil structure interaction for a range of sites can be accommodated
    • Correct treatment of the permafrost in the selection of foundation options is vital in the cold climates being considered
    • The Canadian National Laboratories facility at Chalk River has been identified as a potential site for a proof of concept plant. Siting criteria and associated weighting factors are currently being developed for input into a site selection programme
    • Existing site information is being reviewed to determine what specific investigation studies will need to be implemented once a site is selected

  • Koeberg Nuclear Power Station

    NSE currently provides most of the civil engineering support to Koebergs Nuclear Power Station, current projects include:

    • Analysis and structural evaluation of the 120 m high meteorological mast as well as the re-tensioning, repainting and installation of the new tension monitoring system for the stay cables to the mast.
    • Routine inspection of the meteorological mast.
    • Inspections that constitute the civil monitoring programme of the power station as well as condition inspections of gantries and buildings; Compilation of the design basis for the inspection program
    • Feasibility Studies for special projects requiring civil engineering input.
    • Assessment of Turbine Hall structure for a revised plant layout.
    • Seismic design of the new wind lobby to the PTR tank area and new buildings to house the air-handling equipment.