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Boiling water reactors generally have negative void coefficients, and in normal operation the negative void coefficient allows reactor power to be adjusted by changing the rate of water flow through the core. The negative void coefficient can cause an unplanned reactor power increase in events (such as sudden closure of a streamline valve ...
This is measured by the coolant void coefficient. Most modern nuclear power plants have a negative void coefficient, indicating that as water turns to steam, power instantly decreases. Two exceptions are the Soviet RBMK and the Canadian CANDU. Boiling water reactors, on the other hand, are designed to have steam voids inside the reactor vessel.
Most reactor systems employ a cooling system that is physically separate from the water that will be boiled to produce pressurized steam for the turbines, like the pressurized-water reactor. But in some reactors the water for the steam turbines is boiled directly by the reactor core, for example the boiling-water reactor.
In this formula is the summation of the area fraction of group , over all the different groups and is somewhat similar in form, but not the same as . Ψ m n {\displaystyle \Psi _{mn}} is the group interaction parameter and is a measure of the interaction energy between groups.
The prototype fast breeder reactor has a negative void coefficient, thus ensuring a high level of passive nuclear safety. This means that when the reactor overheats (below the boiling point of sodium) the speed of the fission chain reaction decreases, lowering the power level and the temperature. [25]
Such a condition is called a "positive void coefficient", and the RBMK reactor series has the highest positive void coefficient of any commercial reactor ever designed. A high void coefficient does not necessarily make a reactor inherently unsafe, as some of the fission neutrons are emitted with a delay of seconds or even minutes (post-fission ...
A pressurized heavy-water reactor (PHWR) is a nuclear reactor that uses heavy water (deuterium oxide D 2 O) as its coolant and neutron moderator. [1] PHWRs frequently use natural uranium as fuel, but sometimes also use very low enriched uranium .
To calculate the pressure drop in a given reactor, the following equation may be deduced: = + | |. This arrangement of the Ergun equation makes clear its close relationship to the simpler Kozeny-Carman equation, which describes laminar flow of fluids across packed beds via the first term on the right hand side.