Response Analysis From Transient Signal for Variation of R-C Passive Elements Under High Temperature Accident Condition in NPPs

The electrical signal could be checked whether it lies within its expected electrical range when it is doubtful condition. In the case of an abnormal transient signal from an instrument under a severe accident condition, it needs to define a signal validation to operate at control room in NPPs. Diagnostics and analysis for some abnormal transient signals have been also performed through the important equivalent circuits modeling for the passive elements under the conditions. Even under such a condition, the electrical signal should be within its expected range so that some mitigation actions can be taken through it in control room. Whereas, in case that an abnormal signal is expected from an instrument, such a signal should be refined through a signal validation process so that the refined signal could be available in the control room. For some abnormal signals expected under severe accident conditions, to date, diagnostics and response signals have been evaluated with an equivalent circuit model to real instruments, which is regarded as the best way. Main objective of this paper is to introduce a program designed to implement a diagnostic and response analysis for an equivalent circuit modeling. The program links a signal analysis tool code to an abnormal signal simulation engine not only as a one body order system, but also as a part of functions of a PC-based ASSA (abnormal signal simulation analysis) module developed to obtain a varying range of the elements in high temperature conditions. As a result, a special function for abnormal signal patterns can be obtained through the program, which in turn makes it possible to analyze the abnormal output signals through a response characteristic of a 4∼20mA circuit model and a range of the elements changing with temperature under an accident condition.