抄録
Dead times appear inevitably in responses of plant control systems, which often make the stable control difficult in case with improper values. It is necessary to evaluate them correctly in order to realize the stability of the control systems. A correlation method by a maximum-length linear shift register sequence (M-sequence) was proposed to evaluate the dead time as an accurate method. In nuclear power plants (NPPs), however, response data against M-sequence signals are unavailable at some parts of control systems, because the target locations and signal specifications are highly restricted not to disturb the stable operations. A wavelet analysis method against step responses was applied to Japanese prototype fast breeder reactor MONJU control system in the heat transfer system; one was the primary sodium flow control system and another was the secondary sodium flow control system. This method was considered as a promising method without application of M-sequence signals to the control systems. We also evaluated the dead times by the M-sequence method in the same control systems in order to validate the accuracy. Accordingly, the dead times evaluated by the wavelet analysis method also agreed well with those by the M-sequence method in the two control systems. From these results, we concluded that the present advanced method could predict the dead times with good accuracy in any control systems of NPPs.
