[en] Nuclear reactors generate tremendous amount of thermal energy and radioactivity due to fission reactions. Safety is in general an important aspect for any industry; however, the main safety concern from a Nuclear Reactor is the emission of uncontrolled radiation into the environment which could cause harm to humans both at the reactor site and off-site during an accident. There have been three major reactor accidents in the history of civil nuclear power releasing radioactivity to environment- Three Mile Island, Chernobyl and Fukushima. To avoid these accidents in future, the demand for safety in Nuclear installations have become more important. Nuclear industry from these accidents has learned and taken stringent steps towards ensuring a better reliability of safety systems that ensure cooling of reactor and fuel storage pond, shutting down of reactor and containing the radioactivity. Plant experience indicates that quality assurance during design, procurement, operation, maintenance, surveillance and human resource management have a direct bearing on the reliability of these safety systems. Based on a philosophy that effective quality assurance is inseparably linked to the fostering of an excellent safety culture and ensuring reliability, the implementation of quality management system based on IAEA standard is needed to achieve the desired safety and reliability objective. This paper presents the detailed activities carried out in quality assurance programme in a nuclear reactor to enhance the safety and reliability of nuclear reactor safety systems. (author)