The South African electricity utility, Eskom, has been investigating the Pebble Bed Modular Reactor (PBMR) since 1993 as part of its Integrated Electricity Planning process.

The overall objectives of these investigations were to establish whether such a system could form part of Eskom's expansion planning, and what specific advantages it would bring over other options. These included an evaluation of the technical performance and economic merits of the project. These investigations indicated that the PBMR had major potential advantages, both to the electricity supply industry and to the overall South African economy; and that it warranted consideration as a possible option for future South African electricity supply.

In 2000, a PBMR company was formed between Eskom, the Industrial Development Corporation of South Africa (IDC), British Nuclear Fuel (BNFL) and the US utility Exelon, to build and market PBMR-based power plants. The intention is to build and operate a single module to serve as a demonstration plant and a launch platform for local and international sales. Successful completion of the demonstration will be followed by commercialisation, with Eskom likely to be the first customer.

The PBMR module is the smallest standalone component of the PBMR power generation system. The commercial models can produce approximately 165 MW of electrical power. This module can be used to generate power in a standalone mode or as part of a power plant that consists of up to 10 units.

The module consists of a pebble bed reactor that drives a closed circuit gas turbine machine. The working gas in the cycle is helium. Helium was chosen because it is chemically and radiologically inert.

UG CAD at PBMR

Currently PBMR is making use of Unigraphics CAD as well as Teamcenter software to manage large mechanical assemblies.

P & ID

At PBMR, the P & ID process is currently in its infancy, Autoplant P & ID record structures have, in a demonstration model, been incorporated together with Teamcenter. Communication between P & ID data and Teamcenter Item files has been established. The plans are to expand this demonstration method to include the entire PBMR assembly structure and to use a common database.

According to Craig Kerr, CAD Manager at PBMR, the benefits of incorporating P & ID into the module are shorter design cycle to instrumentation and electrical systems, as well as a more reliable system - due to the fact that all tags can be checked and evaluated.

Large assembly modelling

Within PBMR's drafting module, filters are used to minimise data required for creating standard views, section views and layouts. Reference sets are used in the display of plant layouts. This may often require external data only, thus a 'lite' or 'external' reference set will be used. Filters are then saved with options of 'lite' data. Additional reference sets may also be generated for interface checking and application specific requirements, for example FEM or Computational Fluid Dynamics.

As a general rule, all components are modelled parametrically, however, third party sub-systems may require translation, using parasolid, STEP or IGES. The result is a non-parametric UG model.

In addition to parametric modelling techniques, at PBMR, the unique WAVE method is used to drive 3D component positions and common data through the assembly.

Management of CAD data

According to Kerr, "UG CAD data is central to PBMR's large assembly management philosophy."

Configuration control methods and structures are easily set-up and managed within the Teamcenter environment. Teamcenter provides a flat data structure that may be viewed, but not necessary changed, by working groups and administrators.

Shortening the FEA cycle

Kerr concluded by commenting on the FEA cycle, "The (native) UG CAD file is imported into Patran, saving modelling time and assuring model integrity. Models created parametrically, within UG CAD, may then be changed, using sketches and WAVED geometry, resulting in an updated FEM model. The Create mid surface command may shorten the FEM shell element mesh times. The parasolid output exchange file is also used to interface into PBMR Patran software."

For more information on UG CAD as well as Teamcenter software contact ESTEQ Design, 012 991 9200.

For more information on the PBMR project, visit www.pbmr.co.za