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Like most boiling water reactors, the BWRX-300 will use low pressure water to remove heat from the core. A distinct feature of this reactor design is that water is circulated within the core by natural circulation. This is in contrast to most nuclear reactors which require electrical pumps to provide active cooling of the fuel. This system has ...
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 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 essential service water system (ESWS) circulates the water that cools the plant's heat exchangers and other components before dissipating the heat into the environment. Because this includes cooling the systems that remove decay heat from both the primary system and the spent fuel rod cooling ponds, the ESWS is a safety-critical system. [ 7 ]
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.
Passive nuclear safety is a design approach for safety features, implemented in a nuclear reactor, that does not require any active intervention on the part of the operator or electrical/electronic feedback in order to bring the reactor to a safe shutdown state, in the event of a particular type of emergency (usually overheating resulting from a loss of coolant or loss of coolant flow).
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.