Unlike design basis accidents, some inherent uncertainties of the reliability of instrumentations are expected while subjected to\r\nharsh environments (e.g., high temperature and pressure, high humidity, and high radioactivity) occurring in severe nuclear\r\naccident conditions. Even under such conditions, an electrical signal should be within its expected range so that some mitigating\r\nactions can be taken based on the signal in the control room. For example, an industrial process control standard requires that\r\nthe normal signal level for pressure, flow, and resistance temperature detector sensors be in the range of 4~20mA for most\r\ninstruments.Whereas, in the case that an abnormal signal is expected from an instrument, such a signal should be refined through\r\na signal validation process so that the refined signal could be available in the control room. For some abnormal signals expected\r\nunder severe accident conditions, to date, diagnostics and response analysis have been evaluated with an equivalent circuit model\r\nof real instruments, which is regarded as the best method. The main objective of this paper is to introduce a program designed\r\nto implement a diagnostic and response analysis for equivalent circuit modeling. The program links signal analysis tool code to\r\nabnormal signal simulation engine code not only as a one body order system, but also as a part of functions of a PC-based ASSA\r\n(abnormal signal simulation analysis) module developed to obtain a varying range of the R-C circuit elements in high temperature\r\nconditions. As a result, a special function for abnormal pulse signal patterns can be obtained through the program, which in turn\r\nmakes it possible to analyze the abnormal output pulse signals through a response characteristic of a 4~20mA circuit model and\r\na range of the elements changing with temperature under an accident condition.
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