PBMR design for the future

The Pebble Bed Modular Reactor (PBMR) being developed by Eskom and partners in South Africa, has been under development since 1994. In the process, it was found necessary to increase the unit power in order to stay within the commercial targets set for the project. This was done in successive steps whereby the basic inherent safety characteristics were always kept uppermost in mind. The conceptual design has moved from a copy of the HTR-Modul developed in Germany to a direct gas cycle design utilising the Brayton cycle. In the process of upgrading the output power, the design first adopted an annular core with a dynamic centre column, which was recently replaced by a solid centre reflector. This design change allows a thermal reactor power of 400 MW and keeps the operating fuel temperature below 1130degreesC for low fission product contamination of the turbines. At the same time, the geometry of the core structures was kept such that passive cooling to the environment keeps maximum fuel temperatures of the TRISO-coated particle fuel within the safe limits as proven with predecessor reactors like the AVR. (C) 2003 Elsevier Science B.V. All rights reserved.