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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 ...
Thus the BWR has a negative void coefficient. Reactor pressure in a BWR is controlled by the main turbine or main steam bypass valves. Unlike a PWR, where the turbine steam demand is set manually by the operators, in a BWR, the turbine valves will modulate to maintain reactor pressure at a setpoint.
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]
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.
Should coolant circulation fail, the neutron moderation effect of the water diminishes due to increased heat which creates steam bubbles which do not moderate neutrons, thus reducing reaction intensity and compensating for loss of cooling, a condition known as negative void coefficient. Later versions of the reactors are encased in massive ...
The reactor physics design is tuned to maximise the use of thorium based fuel, by achieving a slightly negative void coefficient. Fulfilling these requirements has been possible through the use of PuO 2 -ThO 2 MOX, and ThO 2 - 233 UO 2 MOX in different pins of the same fuel cluster, and the use of a heterogeneous moderator consisting of ...
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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.