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An LPCI is an emergency system which consists of a pump that injects a coolant into the reactor vessel once it has been depressurized. In some nuclear power plants an LPCI is a mode of operation of a residual heat removal system, also known as an RHR or RHS but is generally called LPCI. It is also not a stand-alone valve or system.
The Reactor Protection System (RPS) is a system, computerized in later BWR models, that is designed to automatically, rapidly, and completely shut down and make safe the Nuclear Steam Supply System (NSSS – the reactor pressure vessel, pumps, and water/steam piping within the containment) if some event occurs that could result in the reactor entering an unsafe operating condition.
Another example was the Isolation Condenser system, which relied on the principle of hot water/steam rising to bring hot coolant into large heat exchangers located above the reactor in very deep tanks of water, thus accomplishing residual heat removal. Yet another example was the omission of recirculation pumps within the core; these pumps were ...
The Fukushima Daiichi nuclear disaster in 2011 occurred due to a loss-of-coolant accident. The circuits that provided electrical power to the coolant pumps failed causing a loss-of-core-cooling that was critical for the removal of residual decay heat which is produced even after active reactors are shut down and nuclear fission has ceased.
The AHWR incorporates several passive safety features. These include: Core heat removal through natural circulation; direct injection of emergency core coolant system (ECCS) water in fuel; and the availability of a large inventory of borated water in overhead gravity-driven water pool (GDWP) to facilitate sustenance of core decay heat removal.
When pressure control is lost in a reactor plant, depending on the level of heat being generated by the reactor plant, the heat being removed by the steam or other auxiliary systems, the initial pressure, and the normal operating temperature of the plant, it could take minutes or even hours for operators to see significant trends in core behaviour.
After the reactor has been depressurized, the decay heat is transferred to the containment as water inside the reactor boils and exits the reactor pressure vessel into the containment in the form of steam. The PCCS consists of a set of heat exchangers located in the upper portion of the reactor building.
A regenerative thermal oxidizer (RTO) is an example of a waste heat recovery unit that utilizes a regenerative process.. A waste heat recovery unit (WHRU) is an energy recovery heat exchanger that transfers heat from process outputs at high temperature to another part of the process for some purpose, usually increased efficiency.