Abstract
In Nuclear Power plants, Reactivity Induced Accidents can lead to sever accidents. Rod Ejection Accidents are part of Reactivity Induced Accidents that induced through driven by reactivity insertion due to many failures. Thus, safety analysis of core behaviour under many external rod reactivities in Nuclear power plants are mandatory by regulators or safety authorities. In this research, a new dynamic model is proposed for core safety analysis under Rod Ejection Accidents. Thermal Power and other core parameters predictions are the most important goals for any reactor operation policy, during all periods and specifically at zero power to avoid severe accidents. The proposed model involves of a point kinetics explanation of neutronics combined with thermal hydraulic dynamics in the reactor core to predict its variation of parameters during transients using MATLAB environment. The proposed model is validated through comparing with the transient dynamic responses obtained through previous research for a chosen design of NuScale small modular reactor. In addition, the proposed model is verified through determining the dynamic reactor responses of Rod Ejection Accidents at hot zero power with many perturbations of different control rod ejection. The Performed safety analysis results of validation and the verification demonstrate that, the proposed model represents the reactor core behavior during the rod ejection transients with good prediction of thermal power of core peaks. Moreover, it allowed large explorations of core safety parameters and predicting the performance of its rector core during Rod Ejection Accidents under critical Hot zero power.
Highlights
A Reactivity Initiated Accident (RIA) is an accident in a nuclear reactor wherever the reactivity is increased involuntarily consecutively fission rate and the thermal power is increased that can lead to fail some fuel rods, or a core disruption if the energy deposited or enthalpy increase that causes severe accidents
The results of adding versus ρext [0.5$ 1$ 1.5$ 2$] as a step reactivity increasing at t=0 sec at initial power 2% an initial value from normal power this case is considered as hot zero power show that: the act of versus ρext causes, the fission rate and fractional thermal core power increase congruently, prompt jump as shown in Figure 7 which illustrates the variation curve of the reactor thermal power ( P) with the versus
They show that the power variation curve illustrates that as larger ρext due to Rod Ejection Accidents (REAs) lead to increase power generation that causes the fuel temperature increases as shown in Figure 8 and when the fuel temperatures increase rapidly produces more heat that moves to the two core coolant temperatures, as shown in Figures (9&10)
Summary
A Reactivity Initiated Accident (RIA) is an accident in a nuclear reactor wherever the reactivity is increased involuntarily consecutively fission rate and the thermal power is increased that can lead to fail some fuel rods, or a core disruption if the energy deposited or enthalpy increase that causes severe accidents. The reactivity adding rates and the resulting power transients increased more and more, the control rod ejections accidents are considered design basis accidents in light water reactors. Many accidents scenarios for control rod ejections in light water reactors are additional described at [4]. Start-up with power is continued over (2%) of full power at that time critical reactor is reached by the core heating through many control rods are removed from the core to increase power more and more to reach operation pressure and temperature. The hot zero power condition is very important to safety analysis since REA can cause sever accidents during increase the thermal power core and if the more reactivity inserted due to external control rod special above than 1$.
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