Selection of Analysis Method

There are two types of approaches used in stability analyses a time domain approach and a frequency domain approach. 

In the time domain approach, the purpose is to simulate the transient behavior of the reactor plant system. The governing equations, which describe the physical phenomena of the reactor dynamics system, are integrated in the time domain. This approach permits the considerations of detailed physical mechanisms, including nonlinear features. It does not need simplified assumptions and can provide information on the behavior of the reactor system beyond the stability threshold. However, a much longer time is necessary to calculate the extensive number of time steps than the frequency domain approach. 

It is well-recognized that instability is a highly nonlinear phenomenon. However, the dynamic behavior of nuclear reactors can be assumed to be linear for small 

For the purpose of preliminary concepmal design of the Super LWR, first, it is important to determine whether the instability will be a problem, and how it can be avoided if it occurs. Thus, the first aim is to investigate what may cause the instability and when it can occur in the Super LWR. To achieve that aim, the approach is to use a simple model which can explain the essential features of the physical phenomena of the system without the requirement of much computing effort. Hence, the simple frequency domain linear stability analysis method is employed to investigate the onset of instability in the Super LWR. 

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The first parts of the AOP 52 give an overview of the management and steering process and technical methods and techniques within the development program, see chapters 3.1 to 3.6. One emphasis lies on an extensive selection of analysis methods for hardware and software. 

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