Design approach to facilitate construction

The ease, efficiency and cost effectiveness of construction of a nuclear power plant are key factors in improving quality and reducing the gestation period and cost. Design has a major effect on construction, as it determines the choices that are available to the construction organizations. If modules are to be used, for example, they must be incorporated into the design from the very beginning of the design process. Otherwise, there is very little chance that the construction organizations can use modular construction techniques.

For most of the analysed projects, design accounts for 6–10% of the total plant capital costs. A specific case is Yonggwang where due to standardisation design costs were reduced to 3.5–4% of the capital costs. Design has a significant impact on the total project costs and a sound design is the key to success of a nuclear power project.

It is good practice to assess the technical merits of all design and engineering options and establish a programme for improving the efficiency of construction through design at an early stage of the project. The programme should specify roles and responsibilities of the plant owner, design and engineering organizations in this regard and include policies, criteria and a set of implementation procedures.

The programme should integrate lessons learned and experiences accumulated from previous practices, both national and international. The programme should provide for incorporating advanced construction methods and techniques into design, implementing construction training to the project personnel, developing a database of lessons learned during the project implementation and establishing a system to measure the cost-benefit of the programme of design for facilitating construction.

5.1.1. Design tools

Computer modelling can be a very effective tool for both designers and constructors.

The use of these tools has not only improved the quality of design and construction by

identifying errors and weaknesses in advance, but it has also resulted in great savings in materials and man-hours so as to reduce the project construction time and costs.

The increasingly integrated design tools known as Computer Aided Design (CAD), Computer Aided Design & Drafting (CADD) or Computer Aided Engineering (CAE) are broadly used in the design and also in the construction and commissioning stages for establishing plant and building layouts. They are in addition used in the modularization process identifying structure and system interfaces; minimizing interferences; reducing the number of welds in components and piping systems; planning and sequencing construction activities; providing documents and other support to procurement; construction &

commissioning activities (such as: releasing drawings; material management; configuration management and providing wiring, cabling, connection and equipment information). It is an essential technology for plant design and a very useful tool during construction and commissioning.

The following examples illustrate the extent to which computer-aided design tools were used in the recent NPP projects:

o Qinshan:

3D CADDs - The design information in CADDs tool (developed by AECL) was integrated with other electronic management systems for controlling and managing of materials and documentation. For the first time CADDs was used to issue formal construction documentation that satisfied the requirements of the QA program. The use of 3D CADDs in the design phase led to dramatic reductions in interferences among different design elements such as piping, cable trays, structural members and equipment. Using manual design techniques, such interferences in the past numbered in thousands for a major project and had to be corrected on the field, but with CADDS, they were substantially reduced.

Integrated Electrical and Control database (IntEC): IntEC is a state of the art cabling and wiring system database developed by AECL. It provides wiring, cabling, connection and equipment information and includes live design and as-pulled data at site for all the wiring, cabling and connections. The design information in CADDs and IntEC was integrated with other AECL electronic management systems for controlling and managing materials and documentation and other project participants, including construction contractors, successfully used it.

o Kashiwazaki-Kariwa:

Three-dimensional CAD (3D-CAD): Hitachi has developed and customized this system based on own plant design practice. The system configuration is shown in Figure 5.1. The system contains a centralized engineering database, which includes small tubes, pipes and supports, enabling wide and effective data applications, e.g. preventive maintenance planning (accessibility, maintainability, etc.) and construction work planning (installation procedure, equipment set-on/carry-in, temporary scaffolding, etc.). This engineering database is very effective in plant design and construction but also in plant data management, preventive maintenance, and improving design, etc.

(Figure 5.2.), and its widely practical use through the entire lifetime of a nuclear plant is greatly expected [3].

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Up to the year 2000, all drawings for Units 3 & 4 were made manually. Later, all the drawings were prepared in AutoCAD, a powerful two-dimensional CAD tool. The three-dimensional feature of AutoCAD 2000 was used to prepare 3D models of the civil structure for better understanding. However, issue of general arrangements, isometric, detailed drawings etc. was done based on the two-dimensional functionality of AutoCAD.

In the year 2002, three-dimensional tools for plant design were used to identify the interferences in various buildings. Having seen the benefits of using 3D plant design tools, it has been planned that for all future units the complete plant will be modelled with 3D plant design software for controlling and managing drawings, documents, bill of material etc. It has also been seen that use of 3D plant design software in the design phase leads to dramatic reductions in interferences among different design elements such as piping, cable trays, structural members and equipment.

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5.2. Improved construction techniques/methods