Safety in shut down

Safety in nuclear power plant at all times is ensured right from design stage to plant construction and operation. Adhering to regulatory limits or criteria ensures safety in shut down, such that safety margins are not reduced. In shut down conditions, sufficient redundancy, reliability and capacity in equipment are provided such that safety margins are not lowered. There is provision of two fast acting independent shut down systems of diverse design, each independently capable of safely terminating any reactivity transient at all circumstances. The depth required would be governed by appropriate combination of reactivity effects, which include total voiding in the core; cool down of fuel, coolant and moderator as well as xenon decay. Depth of the shut down system required during prolonged shutdown is maintained by neutron poison in moderator In shut down condition, reactivity control and cooling of fuel requirements are met at all times. (author)