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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.
The removal of heat from nuclear reactors is an essential step in the generation of energy from nuclear reactions.In nuclear engineering there are a number of empirical or semi-empirical relations used for quantifying the process of removing heat from a nuclear reactor core so that the reactor operates in the projected temperature interval that depends on the materials used in the construction ...
Thus, no electrical pumping assistance should be required, natural convection being sufficient to remove residual heat after shutdown. To achieve this, reactor designs include dedicated passive heat removal systems, that requires no electrical power and no operator action.
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.
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 ...
Following the reactor SCRAM, operators activated the reactor core isolation cooling system (RCIC) and the residual heat removal system and core spray systems were made available to cool the suppression pool; whether they were activated prior to the tsunami has not been made clear. The RHRS and CS pumps were knocked out of commission by the tsunami.
The core produces 2166 MW of heat which is converted into 700 MW of electricity at a thermal efficiency of 32%. Because there is less excess reactivity inside the reactor, it needs to be refuelled continually during operation. The reactor is designed for an estimated life of 40 years. [6]