Method for calculating probability of dangerous failure on demand (PFD) and probability of dangerous failure per hour (PFH) in two out of four channel logic structure system

Abstract

The invention discloses a method for calculating a probability of dangerous failure on demand (PFD) and a probability of dangerous failure per hour (PFH) in a two out of four channel logic structure system. The method includes firstly calculating a common cause failure probability of the PFD and the PFH respectively according to a common cause failure formula of a common channel logic structure, then calculating formulas of probabilities of non-common cause danger failure which occurs in different channels of four channels respectively, and adding the formulas of the probabilities of non-common cause danger failure of different channels and the corresponding common cause failure formula to obtain a calculating method of a danger failure rate of the four channel logic structure. According to the method for calculating the PFD and the PFH in the two out of four channel logic structure system, a result obtained by the method is verified to be completely identical to a standard result and is capable of meeting normative requirements when compared with the result obtained through a reliability basic theory method. Calculating formulas can be directly written without establishing models, and the calculating result is more accurate and low in time consumption.

Description

Technical field [0001] The invention relates to a safety evaluation method, in particular to a non-common cause safety failure probability evaluation method based on PFD and PFH in a two-out-of-four logic architecture in a protection system of a nuclear power plant. Background technique [0002] PFD (Probability of Dangerous Failure on Demand), PFH (Average frequency of dangerous failure[h -1 ]) is a proper term derived from the IEC 61508 standard. PFD is used to evaluate the probability of dangerous failures of the system when required under low-demand operation mode, while PFH is used to evaluate the frequency of dangerous failures of the system under high-demand or continuous operation mode. [0003] IEC 61508-6 (2010 (Edition) is the top-level standard for functional safety. The standard gives the PFD and PFH calculation formulas for the following structures, including: 1oo1 (1out of 1 channel architecture), 1oo2, 2oo2, 1oo2D (1 out of 2 channel architecture with Diagnostics),...

AI Technical Summary

Problems solved by technology

[0005] In order to solve the problem that PFD / PFH does not provide four-channel safety calculation formulas in the prior art, and errors and time-consuming phenomena occur when other methods are used to solve the problem, the present invention provides a four-channel safety calculation formula deduced according to the basic theory of IEC61508. The specific calculation formula is as follows: a calculation method for PFD and PFH in a four-out-of-two logic architecture system, characterized in that,

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