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Decay heat is the heat released as a result of radioactive decay. This heat is produced as an effect of radiation on materials: the energy of the alpha, beta or gamma radiation is converted into the thermal movement of atoms. Decay heat occurs naturally from decay of long-lived radioisotopes that are primordially present from the Earth's formation.
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 ...
In events where the reactor coolant pressure boundary remains intact, the Isolation Condenser System (ICS) is used to remove decay heat from the reactor and transfer it outside containment. The ICS system is a closed loop system that connects the reactor pressure vessel to a heat exchanger located in the upper elevation of the reactor building.
This is a heat exchanger located above containment in a pool of water open to atmosphere. When activated, decay heat boils steam, which is drawn into the heat exchanger and condensed; then it falls by weight of gravity back into the reactor. This process keeps the cooling water in the reactor, making it unnecessary to use powered feedwater pumps.
In the event of a reactor shutdown and failure of all active heat-removal systems in the SSR, decay heat from the core would dissipate into air-cooling ducts around the perimeter of the tank that operate continually. This is known as the Emergency Heat Removal System. The main heat-transfer mechanism is radiative.
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 ...
Passive decay heat removal is achieved in MSRs. In some designs, the fuel and the coolant are a single fluid, so a loss of coolant carries the fuel with it. Fluoride salts dissolve poorly in water, and do not form burnable hydrogen. The molten salt coolant is not damaged by neutron bombardment, though the reactor vessel is.
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).