[en] As the nuclear power simulation training industry matures, the needs of the individual training facilities are becoming increasingly diverse. To respond to this trend, simulation vendors must offer a greater level of customization, and as such, are facing increasingly challenging projects. In 2002, CAE embarked on such a project for South Africas Koeberg nuclear power station. This simulator upgrade project, carried out in two phases, served as a unique exercise in product customization. In the first phase, CAE replaced the simulation servers, the software environment, and re-hosted the existing plant models. In the second phase, CAE replaced several of the existing thermal-hydraulics models to improve simulator fidelity. Throughout this project, CAE overcame a series of challenges stemming from project-specific requirements. In fact, the retention of the legacy software maintenance tools, the preservation of the instructor station package, and the interfacing with the existing hardware panel elements presented a number of opportunities for innovation. In the end, CAE overcame the challenges and acquired invaluable experience in doing so. (author)